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Journal articles on the topic 'S-H Bond Study'

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Published: 7 September 2023

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1

Munshi, Parthapratim, Tejender S. Thakur, Tayur N. Guru Row, and Gautam R. Desiraju. "Five varieties of hydrogen bond in 1-formyl-3-thiosemicarbazide: an electron density study." Acta Crystallographica Section B Structural Science 62, no. 1 (January 17, 2006): 118–27. http://dx.doi.org/10.1107/s0108768105033689.

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In an attempt to investigate the putative S—H...N hydrogen bond, we have studied the title compound, 1-formyl-3-thiosemicarbazide, which was revealed in a CSD search as a crystal structure which might show such an interaction. However, a redetermination of the structure at room temperature and careful analysis showed that the earlier study [Saxena et al. (1991). Acta Cryst. C47, 2374–2376] on which the CSD search was based was in error and that the possibility of an S—H...N hydrogen bond is negated. The presence of five other varieties of hydrogen bond (N—H...O, N—H...S, N—H...N, C—H...O, C—H...S) in the crystal packing prompted us to redirect our efforts and to undertake a study of the charge-density distribution at 90 K. The topological analysis of these five varieties of hydrogen bond was carried out with Bader's quantum theory of `atoms in molecules' and by applying Koch–Popelier's criteria. The analysis reveals that the hydrogen-bond strength is highest for N—H...O and lowest for C—H...S with N—H...S, N—H...N and C—H...O forming the middle order.
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2

Kohli, Ruchi, and Rupinder Preet Kaur. "A Theoretical Study of Hydrogen-Bonded Complexes of Ethylene Glycol, Thioglycol and Dithioglycol with Water." Asian Journal of Chemistry 34, no. 1 (2021): 169–82. http://dx.doi.org/10.14233/ajchem.2022.23487.

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In the present study, a theoretical analysis of hydrogen bond formation of ethylene glycol, thioglycol, dithioglycol with single water molecule has been performed based on structural parameters of optimized geometries, interaction energies, deformation energies, orbital analysis and charge transfer. ab initio molecular orbital theory (MP2) method in conjunction with 6-31+G* basis set has been employed. Twelve aggregates of the selected molecules with water have been optimized at MP2/6-31+G* level and analyzed for intramolecular and intermolecular hydrogen bond interactions. The evaluated interaction energies suggest aggregates have hydrogen bonds of weak to moderate strength. Although the aggregates are primarily stabilized by conventional hydrogen bond donors and acceptors, yet C-H···O, S-H···O, O-H···S, etc. untraditional hydrogen bonds also contribute to stabilize many aggregates. The hydrogen bonding involving sulfur in the aggregates of thioglycol and dithioglycol is disfavoured electrostatically but favoured by charge transfer. Natural bond orbital (NBO) analysis has been employed to understand the role of electron delocalizations, bond polarizations, charge transfer, etc. as contributors to stabilization energy.
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3

Wood, Peter A., Elna Pidcock, and Frank H. Allen. "Interaction geometries and energies of hydrogen bonds to C=O and C=S acceptors: a comparative study." Acta Crystallographica Section B Structural Science 64, no. 4 (July 10, 2008): 491–96. http://dx.doi.org/10.1107/s0108768108015437.

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The occurrence, geometries and energies of hydrogen bonds from N—H and O—H donors to the S acceptors of thiourea derivatives, thioamides and thiones are compared with data for their O analogues – ureas, amides and ketones. Geometrical data derived from the Cambridge Structural Database indicate that hydrogen bonds to the C=S acceptors are much weaker than those to their C=O counterparts: van der Waals normalized hydrogen bonds to O are shorter than those to S by ∼ 0.25 Å. Further, the directionality of the approach of the hydrogen bond with respect to S, defined by the C=S...H angle, is in the range 102–109°, much lower than the analogous C=O...H angle which lies in the range 127–140°. Ab initio calculations using intermolecular perturbation theory show good agreement with the experimental results: the differences in hydrogen-bond directionality are closely reproduced, and the interaction energies of hydrogen bonds to S are consistently weaker than those to O, by ∼ 12 kJ mol−1, for each of the three compound classes. There are no CSD examples of hydrogen bonds to aliphatic thiones, (Csp 3)2C=S, consistent with the near-equality of the electronegativities of C and S. Thioureas and thioamides have electron-rich N substituents replacing the Csp 3 atoms. Electron delocalization involving C=S and the N lone pairs then induces a significant >Cδ+=Sδ− dipole, which enables the formation of the medium-strength C=S...H bonds observed in thioureas and thioamides.
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4

Nowroozi, A., H. Roohi, M. Poorsargol, P. Mohammadzadeh Jahani, H. Hajiabadi, and H. Raissi. "NH···S and SH···N intramolecular hydrogen bond in β-thioaminoacrolein: A quantum chemical study." International Journal of Quantum Chemistry 111, no. 12 (June 10, 2010): 3008–16. http://dx.doi.org/10.1002/qua.22615.

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5

Steiner, T. "Hydrogen-Bond Distances to Halide Ions in Organic and Organometallic Crystal Structures: Up-to-date Database Study." Acta Crystallographica Section B Structural Science 54, no. 4 (August 1, 1998): 456–63. http://dx.doi.org/10.1107/s0108768197014821.

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Geometrical data on hydrogen bonds to halide ions are compiled from the currently available crystal structures. Hydrogen bonds from 25 donor types to fluoride, chloride, bromide and iodide ions are considered. Compared with earlier compilations, the increased data volume allows a finer subdivision of O—H and N—H donors, and the donors C—H, S—H and P—H can be included. For a given donor type, the hydrogen-bond distance typically increases by over 0.5 Å from fluoride to chloride, 0.15 Å from chloride to bromide and 0.25 Å from bromide to iodide acceptors. The strongest of the C—H donors considered, chloroform, forms hydrogen bonds with chloride ions with an average H...Cl separation of only 2.39 Å and an average C...Cl separation of 3.42 Å. The lengthening of the N—H covalent bond in hydrogen bonds to chloride ions is quantified from neutron diffraction data.
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6

Li, An Yong, Li Juan Cao, and Hong Bo Ji. "Theoretical study of H bonds of HArF and HF with isoelectronic systems N2, CO, and BF." Canadian Journal of Chemistry 88, no. 4 (April 2010): 352–61. http://dx.doi.org/10.1139/v10-004.

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The H bonds of HArF and HF with N2, CO, and BF were studied at the MP2(full)/6-311++G(2d, 2p) level. The results show that only the complexes WY···HArF (WY = N2, OC) and WY···HF (WY = N2, OC, FB) are stable, the H-bonding WY···HArF leads to contraction of the HAr bond with a concomitant frequency blue shift, but the H-bonding WY···HF causes the HF bond to elongate with a frequency red shift. A quantity P is defined to measure polarization of the HX bond; the H bonding causes the P value of the HX bond (X = Ar, F) to increase. The HX bond length change and frequency shift in the H-bonding WY···HArF and WY···HF are mainly caused by intermolecular hyperconjugation, n(Y) → σ*(HX) (X = Ar, F), where electrostatic interaction has only a small contribution. In HArF, the strong intramolecular hyperconjugation, n(F) → σ*(HAr), can adjust electron density on σ*(HAr); upon formation of H bonding, the HAr stretching frequency blue shift is caused by a decrease of intramolecular hyperconjugation and an increase of the s character of the Ar hybrid in the HAr bond, induced by the intermolecular hyperconjugation. In the H bonds of HF without intramolecular hyperconjugation, the intermolecular hyperconjugation, n(Y) → σ*(HF), leads to a red shift of the HF bond, although there is also large rehybridization.
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7

Yang, Yong. "Theoretical study of the SH···O blue-shifted hydrogen bond." International Journal of Quantum Chemistry 109, no. 2 (2009): 266–74. http://dx.doi.org/10.1002/qua.21691.

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8

Raissi, Heidar, Mehdi Yoosefian, Soheila Zamani, and Farzaneh Farzad. "Conformational study, molecular structure, and S…H‒N, S‒H…N intramolecular hydrogen bond in thioformyl-3-aminoacrylaldehyde." Journal of Sulfur Chemistry 33, no. 1 (November 28, 2011): 75–85. http://dx.doi.org/10.1080/17415993.2011.635793.

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9

Hützler, Wilhelm Maximilian, and Michael Bolte. "Five pseudopolymorphs of 6-amino-2-thiouracil: absence of N—H...S hydrogen bonds." Acta Crystallographica Section C Crystal Structure Communications 69, no. 1 (December 15, 2012): 93–100. http://dx.doi.org/10.1107/s010827011204930x.

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In order to study the preferred hydrogen-bonding pattern of 6-amino-2-thiouracil, C4H5N3OS, (I), crystallization experiments yielded five different pseudopolymorphs of (I), namely the dimethylformamide disolvate, C4H5N3OS·2C3H7NO, (Ia), the dimethylacetamide monosolvate, C4H5N3OS·C4H9NO, (Ib), the dimethylacetamide sesquisolvate, C4H5N3OS·1.5C4H9NO, (Ic), and two different 1-methylpyrrolidin-2-one sesquisolvates, C4H5N3OS·1.5C5H9NO, (Id) and (Ie). All structures containR21(6) N—H...O hydrogen-bond motifs. In the latter four structures, additionalR22(8) N—H...O hydrogen-bond motifs are present stabilizing homodimers of (I). No type of hydrogen bond other than N—H...O is observed. According to a search of the Cambridge Structural Database, most 2-thiouracil derivatives form homodimers stabilized by anR22(8) hydrogen-bonding pattern, with (i) only N—H...O, (ii) only N—H...S or (iii) alternating pairs of N—H...O and N—H...S hydrogen bonds.
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10

Kruszynski, Rafal. "Intermolecular interactions in 2,4-dinitrophenylhydrazine hydrochloride hydrate: X-ray structural and quantum mechanical study." Open Chemistry 6, no. 4 (December 1, 2008): 542–48. http://dx.doi.org/10.2478/s11532-008-0067-7.

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Abstract2,4-dinitrophenylhydrazine hydrochloride hydrate (I) was determined by X-ray crystallography, and the intermolecular interaction energies were calculated in terms of Natural Bond Orbital analysis. The asymmetric unit of (I) consists of a dinitrophenylhydrazinium cation, a chloride anion and a water molecule. The interatomic distances and angles in (I) show no unusual values. In the structure there are intermolecular N—H⊎⊎⊎O, N—H⊎⊎⊎Cl, O—H⊎⊎⊎Cl, C—H⊎⊎⊎O hydrogen bonds with bonding energy ranging form 16.03 to 0.76 kcal mol−1. These hydrogen bonds create the following N1 motifs: 6D, S(5), S(6), C(6), C(9). N1D motifs become infinite at the third level and are 2C 32(6), C 32(7).
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11

Ramegowda, Mariyappa, Keremegaladoddi N. Ranjitha, and Thalashasana N. Deepika. "Exploring excited state properties of 7-hydroxy and 7-methoxy 4-methycoumarin: a combined time-dependent density functional theory/effective fragment potential study." New Journal of Chemistry 40, no. 3 (2016): 2211–19. http://dx.doi.org/10.1039/c5nj02917a.

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12

Okuniewski, Andrzej, Damian Rosiak, Jarosław Chojnacki, and Barbara Becker. "Crystallographic study of self-organization in the solid state including quasi-aromatic pseudo-ring stacking interactions in 1-benzoyl-3-(3,4-dimethoxyphenyl)thiourea and 1-benzoyl-3-(2-hydroxypropyl)thiourea." Acta Crystallographica Section C Structural Chemistry 73, no. 1 (January 1, 2017): 52–56. http://dx.doi.org/10.1107/s2053229616019495.

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1-Benzoylthioureas contain both carbonyl and thiocarbonyl functional groups and are of interest for their biological activity, metal coordination ability and involvement in hydrogen-bond formation. Two novel 1-benzoylthiourea derivatives, namely 1-benzoyl-3-(3,4-dimethoxyphenyl)thiourea, C16H16N2O3S, (I), and 1-benzoyl-3-(2-hydroxypropyl)thiourea, C11H14N2O2S, (II), have been synthesized and characterized. Compound (I) crystallizes in the space group P\overline{1}, while (II) crystallizes in the space group P21/c. In both structures, intramolecular N—H...O hydrogen bonding is present. The resulting six-membered pseudo-rings are quasi-aromatic and, in each case, interact with phenyl rings via stacking-type interactions. C—H...O, C—H...S and C—H...π interactions are also present. In (I), there is one molecule in the asymmetric unit. Pairs of molecules are connected via two intermolecular N—H...S hydrogen bonds, forming centrosymmetric dimers. In (II), there are two symmetry-independent molecules that differ mainly in the relative orientations of the phenyl rings with respect to the thiourea cores. Additional strong hydrogen-bond donor and acceptor –OH groups participate in the formation of intermolecular N—H...O and O—H...S hydrogen bonds that join molecules into chains extending in the [001] direction.
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13

Poon, Clement, and Paul M. Mayer. "Electron-spin conservation and methyl-substitution effects on bonds in closed- and open-shell systems — A G3 ab initio study of small boron-containing molecules and radicals." Canadian Journal of Chemistry 80, no. 1 (January 1, 2002): 25–30. http://dx.doi.org/10.1139/v01-185.

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High level ab initio molecular orbital theory calculations have been used to study the geometries and thermochemistry of molecules and free radicals substituted by BH2, BHCH3, and B(CH3)2. The heats of formation and RR'B—X bond strengths (RR' = H, H; H, CH3; CH3, CH3 and X = CH3, NH2, OH, F, SiH3, PH2, SH, and Cl) together with those for the open-shell systems RR'B—Y· (RR' = H, H; H, CH3; CH3, CH3 and Y = CH2, NH, O, SiH2, PH, and S) have been calculated at the G3 level of theory. The trends observed for the homolytic bond strengths in the closed-shell systems are those expected from electronegativity arguments, i.e., as the difference in electronegativity between the two atoms in the B—X bond increases, the bond strength increases. Methyl substitution on B in the closed- and open-shell species increases the ionic contribution to the bond thereby decreasing the bond strength. The lowest possible homolytic dissociation energy for the free radicals RR'BY· is lower than those of their closed-shell counterparts, yet the B—Y· bonds are shorter. This is due to the demands of spin conservation in the dissociation of the radicals favouring the formation of higher energy products.Key words: ab initio calculations, bond dissociation energy, organoboron compounds, thermochemistry.
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14

Hamzehee, Farahnaz, Mehrdad Pourayoubi, Marek Nečas, and Duane Choquesillo-Lazarte. "Extensive analysis of N—H...O hydrogen bonding in four classes of phosphorus compounds: a combined experimental and database study." Acta Crystallographica Section C Structural Chemistry 73, no. 3 (February 21, 2017): 287–97. http://dx.doi.org/10.1107/s2053229617001516.

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The N—H...O hydrogen bond is the characteristic interaction in the crystal structures of N-benzyl-P-phenyl-N′-(p-tolyl)phosphonic diamide, C20H21N2OP or (C6H5)P(O)(NHCH2C6H5)(NHC6H4-p-CH3), (I), diphenylphosphinic 1-methylpropylamide, C16H20NOP or (C6H5)2P(O)[NHCH(CH3)(C2H5)], (II), (S)-1-phenylethylammonium N-[(S)-1-phenylethyl]phenylphosphonamidate, C8H12N+·C14H15NO2P− or [S-(C6H5)CH(CH3)NH3][(C6H5)P(O){S-NHCH(CH3)(C6H5)}(O)], (III), and (4-methylbenzyl)ammonium diphenylphosphinate, C8H12N+·C12H10O2P− or [4-CH3-C6H4CH2NH3][(C6H5)2P(O)(O)], (IV). This article focuses on the N—H...O hydrogen bonds by considering the structures of (I), (II), (III) and (IV), and reviewing their analogous compounds, including 43 (C)P(O)(N)2, 102 (C)2P(O)(N), 31 (C)P(O)(N)(O) and 96 (C)2P(O)(O) structures, deposited in the Cambridge Structural Database (CSD). For the structures with a (C)P(O)(N)2 segment, only neutral hydrogen bonds were found in the CSD. The other three classes of compounds included both neutral and `charge-assisted' hydrogen bonds, and the (C)2P(O)(O) structures were particularly noticeable for a high number of cation–anion compounds. The overall tendencies of N...O distances in neutral and cation–anion compounds were compared. The N—H...O hydrogen-bond angles were also analyzed for the four classes of phosphorus compounds.
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15

Pavan, Mysore S., Sounak Sarkar, and Tayur N. Guru Row. "Exploring the rare S—H...S hydrogen bond using charge density analysis in isomers of mercaptobenzoic acid." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 73, no. 4 (July 27, 2017): 626–33. http://dx.doi.org/10.1107/s2052520617008344.

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Experimental and theoretical charge density analyses on isomers of mercaptobenzoic acid have been carried out to quantify the hydrogen bonding of the hitherto less explored thiols, to assess the strength of the interactions using the topological features of the electron density. The electron density study offers interesting insights into the nature of the S—H...S interaction. The interaction energy is comparable with that of a weak hydrogen bond. The strength and directionality of the S—H...S hydrogen bond is demonstrated to be mainly due to the conformation locking potential of the intramolecular S...O chalcogen bond in 2-mercaptobenzoic acid and is stronger than in 3-mercaptobenzoic acid, which lacks the intramolecular S...O bond. Thepara-substituted mercaptobenzoic acid depicts a type I S...S interaction.
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16

Paulus, Georgiana, Huey Chong Kwong, Karen A. Crouse, and Edward R. T. Tiekink. "2-[(1E)-[(Z)-2-({[(1Z)-[(E)-2-[(2-Hydroxyphenyl)methylidene]hydrazin-1-ylidene]({[(4-methylphenyl)methyl]sulfanyl})methyl]disulfanyl}({[(4-methylphenyl)methyl]sulfanyl})methylidene)hydrazin-1-ylidene]methyl]phenol: crystal structure, Hirshfeld surface analysis and computational study." Acta Crystallographica Section E Crystallographic Communications 76, no. 8 (July 10, 2020): 1245–50. http://dx.doi.org/10.1107/s2056989020008762.

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The complete molecule of the title hydrazine carbodithioate derivative, C32H30N4O2S4, is generated by a crystallographic twofold axis that bisects the disulfide bond. The molecule is twisted about this bond with the C—S—S—C torsion angle of 90.70 (8)° indicating an orthogonal relationship between the symmetry-related halves of the molecule. The conformation about the imine bond [1.282 (2) Å] is E and there is limited delocalization of π-electron density over the CN2C residue as there is a twist about the N—N bond [C—N—N—C torsion angle = −166.57 (15)°]. An intramolecular hydroxyl-O—H...N(imine) hydrogen bond closes an S(6) loop. In the crystal, methylene-C—H...π(tolyl) contacts assemble molecules into a supramolecular layer propagating in the ab plane: the layers stack without directional interactions between them. The analysis of the calculated Hirshfeld surfaces confirm the importance of H...H contacts, which contribute 46.7% of all contacts followed by H...C/C...H contacts [25.5%] reflecting, in part, the C—H...π(tolyl) contacts. The calculation of the interaction energies confirm the importance of the dispersion term and the influence of the stabilizing H...H contacts in the inter-layer region.
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17

Khairuanuar, Nadia Liyana, Karen A. Crouse, Huey Chong Kwong, Sang Loon Tan, and Edward R. T. Tiekink. "4-[(1E)-({[(Benzylsulfanyl)methanethioyl]amino}imino)methyl]benzene-1,3-diol chloroform hemisolvate: crystal structure, Hirshfeld surface analysis and computational study." Acta Crystallographica Section E Crystallographic Communications 76, no. 7 (June 2, 2020): 990–97. http://dx.doi.org/10.1107/s2056989020007070.

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The title hydrazine carbodithioate chloroform hemisolvate, 2C15H14N2O2S2·CHCl3, comprises two independent hydrazine carbodithioate molecules, A and B, and a chloroform molecule; the latter is statistically disordered about its molecular threefold axis. The common features of the organic molecules include an almost planar, central CN2S2 chromophore [r.m.s. deviation = 0.0203 Å (A) and 0.0080 Å (B)], an E configuration about the imine bond and an intramolecular hydroxyl-O—H...N(imine) hydrogen bond. The major conformational difference between the molecules is seen in the relative dispositions of the phenyl rings as indicated by the values of the dihedral angles between the central plane and phenyl ring of 71.21 (6)° (A) and 54.73 (7)° (B). Finally, a difference is seen in the disposition of the outer hydroxyl-H atoms, having opposite relative orientations. In the calculated gas-phase structure, the entire molecule is planar with the exception of the perpendicular phenyl ring. In the molecular packing, the A and B molecules assemble into a two-molecule aggregate via N—H...S hydrogen bonds and eight-membered {...HNCS}2 synthons. The dimeric assemblies are connected into supramolecular chains via hydroxyl-O—H...O(hydroxyl) hydrogen bonds and these are linked into a double-chain through hydroxy-O—H...π(phenyl) interactions. The double-chains are connected into a three-dimensional architecture through phenyl-C—H...O(hydroxyl) and phenyl-C—H...π(phenyl) interactions. The overall assembly defines columns along the a-axis direction in which reside the chloroform molecules, which are stabilized by chloroform–methine-C—H...S(thione) and phenyl-C—H...Cl contacts. The analysis of the calculated Hirshfeld surfaces, non-covalent interaction plots and interaction energies confirm the importance of the above-mentioned interactions, but also of cooperative, non-standard interactions such as π(benzene)...π(hydrogen-bond-mediated-ring) contacts.
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18

Tan, Ming Yueh, Huey Chong Kwong, Karen A. Crouse, Thahira B. S. A. Ravoof, and Edward R. T. Tiekink. "1-{(E)-[4-(4-Hydroxyphenyl)butan-2-ylidene]amino}-3-phenylthiourea: crystal structure, Hirshfeld surface analysis and computational study." Acta Crystallographica Section E Crystallographic Communications 77, no. 8 (July 13, 2021): 788–94. http://dx.doi.org/10.1107/s2056989021006666.

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The title thiourea derivative, C17H19N3OS, adopts a U-shaped conformation with the dihedral angle between the terminal aromatic rings being 73.64 (5)°. The major twist in the molecule occurs about the ethane bond with the Ci—Ce—Ce—Cb torsion angle being −78.12 (18)°; i = imine, e = ethane and b = benzene. The configuration about the imine bond is E, the N-bound H atoms lie on opposite sides of the molecule and an intramolecular amine-N—H...N(imine) hydrogen bond is evident. In the molecular packing, hydroxyl-O—H...S(thione) and amine-N—H...O hydrogen bonding feature within a linear, supramolecular chain. The chains are connected into a layer in the ab plane by a combination of methylene-C—H...S(thione), methylene-C—H...O(hydroxyl), methyl-C—H...π(phenyl) and phenyl-C—H...π(hydroxybenzene) interactions. The layers stack without directional interactions between them. The analysis of the calculated Hirshfeld surface highlights the presence of weak methyl-C—H...O(hydroxyl) and H...H interactions in the inter-layer region. Computational chemistry indicates that dispersion energy is the major contributor to the overall stabilization of the molecular packing.
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19

Su, Xing-Xing, Xia-He Chen, De-Bo Ding, Yuan-Bin She, and Yun-Fang Yang. "Computational Exploration of Dirhodium Complex-Catalyzed Selective Intermolecular Amination of Tertiary vs. Benzylic C−H Bonds." Molecules 28, no. 4 (February 17, 2023): 1928. http://dx.doi.org/10.3390/molecules28041928.

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The mechanism and origins of site-selectivity of Rh2(S-tfpttl)4-catalyzed C(sp3)–H bond aminations were studied using density functional theory (DFT) calculations. The synergistic combination of the dirhodium complex Rh2(S-tfpttl)4 with tert-butylphenol sulfamate TBPhsNH2 composes a pocket that can access both tertiary and benzylic C–H bonds. The nonactivated tertiary C–H bond was selectively aminated in the presence of an electronically activated benzylic C–H bond. Both singlet and triplet energy surfaces were investigated in this study. The computational results suggest that the triplet stepwise pathway is more favorable than the singlet concerted pathway. In the hydrogen atom abstraction by Rh–nitrene species, which is the rate- and site-selectivity-determining step, there is an attractive π–π stacking interaction between the phenyl group of the substrate and the phthalimido group of the ligand in the tertiary C–H activation transition structure. By contrast, such attractive interaction is absent in the benzylic C–H amination transition structure. Therefore, the DFT computational results clearly demonstrate how the synergistic combination of the dirhodium complex with sulfamate overrides the intrinsic preference for benzylic C–H amination to achieve the amination of the nonactivated tertiary C–H bond.
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20

Dege, Necmi, Md Serajul Haque Faizi, Onur Erman Doğan, Erbil Ağar, and Irina A. Golenya. "Crystal structure and DFT study of (E)-2-chloro-4-{[2-(2,4-dinitrophenyl)hydrazin-1-ylidene]methyl}phenol acetonitrile hemisolvate." Acta Crystallographica Section E Crystallographic Communications 75, no. 6 (May 10, 2019): 770–73. http://dx.doi.org/10.1107/s205698901900642x.

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The title Schiff base compound, C13H9ClN4O5·0.5CH3CN, crystallizes as an acetonitrile hemisolvate; the solvent molecule being located on a twofold rotation axis. The molecule is nearly planar, with a dihedral angle between the two benzene rings of 3.7 (2)°. The configuration about the C=N bond is E, and there is an intramolecular N—H...Onitro hydrogen bond present forming an S(6) ring motif. In the crystal, molecules are linked by O—H...O and N—H...O hydrogen bonds, forming layers lying parallel to (10\overline{1}). The layers are linked by C—H...Cl hydrogen bonds, forming a supramolecular framework. Within the framework there are offset π–π stacking interactions [intercentroid distance = 3.833 (2) Å] present involving inversion-related molecules. The DFT study shows that the HOMO and LUMO are localized in the plane extending from the phenol ring to the 2,4-dinitrobenzene ring, and the HOMO–LUMO gap is found to be 0.13061 a.u.
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21

Djedouani, Amel, Barkahem Anak, Salima Tabti, Franck Cleymand, Michel François, and Solenne Fleutot. "Crystal structure and DFT study of the zwitterionic form of 3-{(E)-1-[(4-ethoxyphenyl)iminiumyl]ethyl}-6-methyl-2-oxo-2H-pyran-4-olate." Acta Crystallographica Section E Crystallographic Communications 74, no. 2 (January 16, 2018): 172–75. http://dx.doi.org/10.1107/s2056989018000919.

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The title Schiff base compound, C16H17NO4, crystallizes as a zwitterion, with the phenolic H atom having been transferred to the imino group. The resulting iminium and hydroxy groups are linked by an intramolecular N—H...O hydrogen bond, enclosing an S(6) ring motif. The conformation about the C=N bond is E and the dihedral angle between the benzene and pyran rings is 70.49 (6)°. In the crystal, molecules are linked by C—H...O hydrogen bonds, forming a three-dimensional supramolecular structure. There are also C—H...π interactions and offset π–π interactions, involving the pyran rings [intercentroid distance = 3.4156 (8) Å], which consolidate the three-dimensional structure. Quantum chemical calculations of the molecule are in good agreement with the solid state keto–amine (NH) form of the title compound.
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22

Tan, Sang Loon, Mukesh M. Jotani, and Edward R. T. Tiekink. "3,3-Bis(2-hydroxyethyl)-1-(4-nitrobenzoyl)thiourea: crystal structure, Hirshfeld surface analysis and computational study." Acta Crystallographica Section E Crystallographic Communications 76, no. 2 (January 7, 2020): 155–61. http://dx.doi.org/10.1107/s2056989019017328.

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In the title compound, C12H15N3O5S, a trisubstituted thiourea derivative, the central CN2S chromophore is almost planar (r.m.s. deviation = 0.018 Å) and the pendant hydroxyethyl groups lie to either side of this plane. While to a first approximation the thione-S and carbonyl-O atoms lie to the same side of the molecule, the S—C—N—C torsion angle of −47.8 (2)° indicates a considerable twist. As one of the hydroxyethyl groups is orientated towards the thioamide residue, an intramolecular N—H...O hydrogen bond is formed which leads to an S(7) loop. A further twist in the molecule is indicated by the dihedral angle of 65.87 (7)° between the planes through the CN2S chromophore and the 4-nitrobenzene ring. There is a close match between the experimental and gas-phase, geometry-optimized (DFT) molecular structures. In the crystal, O—H...O and O—H...S hydrogen bonds give rise to supramolecular layers propagating in the ab plane. The connections between layers to consolidate the three-dimensional architecture are of the type C—H...O, C—H...S and nitro-O...π. The nature of the supramolecular association has been further analysed by a study of the calculated Hirshfeld surfaces, non-covalent interaction plots and computational chemistry, all of which point to the significant influence and energy of stabilization provided by the conventional hydrogen bonds.
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23

Dandárová, Miloslava, Daniel Végh, Jaroslav Kováč, Igor Goljer, Nadežda Prónayová, and Katarína Špirková. "1H and 13C NMR study of some substituted 2-furyl- and 2-thienylethylene derivatives." Collection of Czechoslovak Chemical Communications 51, no. 4 (1986): 889–98. http://dx.doi.org/10.1135/cccc19860889.

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The 1H and 13C NMR spectral data of 1-(5-nitro-2-furyl)-2-X-2-Y-ethylenes and some their thienyl analogues are presented. Geometrical arrangement of the trisubstituted ethylenes was adduced from vicinal coupling constants 3J(C, H) for the carbon atom at the functional group attached to the double bond and the ethylene proton. The orientation of the heterocyclic ring towards the double bond of the side chain was determined from the 1H NMR data. The preferred s-cis or s-trans conformations of 5-nitro-2-furylethylene derivatives is substituent at the double bond dependent; all thiophene derivatives under study were found in the s-trans conformation.
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24

Jiang, Yuan-Ye, Ling Zhu, Xia Fan, Qi Zhang, Ya-Jie Fu, He Li, Bing Hu, and Siwei Bi. "A computational study on H2S release and amide formation from thionoesters and cysteine." Organic & Biomolecular Chemistry 17, no. 23 (2019): 5771–78. http://dx.doi.org/10.1039/c9ob00854c.

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25

Tan, Sang Loon, Ainnul Hamidah Syahadah Azizan, Mukesh M. Jotani, and Edward R. T. Tiekink. "3,3-Bis(2-hydroxyethyl)-1-(4-methylbenzoyl)thiourea: crystal structure, Hirshfeld surface analysis and computational study." Acta Crystallographica Section E Crystallographic Communications 75, no. 10 (September 12, 2019): 1472–78. http://dx.doi.org/10.1107/s2056989019012581.

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In the title tri-substituted thiourea derivative, C13H18N2O3S, the thione-S and carbonyl-O atoms lie, to a first approximation, to the same side of the molecule [the S—C—N—C torsion angle is −49.3 (2)°]. The CN2S plane is almost planar (r.m.s. deviation = 0.018 Å) with the hydroxyethyl groups lying to either side of this plane. One hydroxyethyl group is orientated towards the thioamide functionality enabling the formation of an intramolecular N—H...O hydrogen bond leading to an S(7) loop. The dihedral angle [72.12 (9)°] between the planes through the CN2S atoms and the 4-tolyl ring indicates the molecule is twisted. The experimental molecular structure is close to the gas-phase, geometry-optimized structure calculated by DFT methods. In the molecular packing, hydroxyl-O—H...O(hydroxyl) and hydroxyl-O—H...S(thione) hydrogen bonds lead to the formation of a supramolecular layer in the ab plane; no directional interactions are found between layers. The influence of the specified supramolecular interactions is apparent in the calculated Hirshfeld surfaces and these are shown to be attractive in non-covalent interaction plots; the interaction energies point to the important stabilization provided by directional O—H...O hydrogen bonds.
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26

Bandyopadhyay, Debashruti, Annaram Thirupathi, Nagsen Munjaji Dhage, Nirmala Mohanta, and S. Peruncheralathan. "Nickel catalyzed site selective C–H functionalization of α-aryl-thioamides." Organic & Biomolecular Chemistry 16, no. 35 (2018): 6405–9. http://dx.doi.org/10.1039/c8ob01712c.

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27

Henschel, Dagmar, Oliver Moers, Karna Wijaya, Andreas Wirth, Armand Blaschette, and Peter G. Jones. "Polysulfonylamine, CLIII [1]. Schwache Wasserstoffbrücken mit aktivierten Methyldonoren: Kristallstrukturen von Cholinium-, Betainium- und Dimethyl[2-(dimethylamino)ethyl]ammonium-dimesylamid Polysulfonylamines, CLIII [1]. Weak Hydrogen Bonding with Activated Methyl Donors: Crystal Structures of Cholinium, Betainium and Dimethyl[2-(dimethylamino)ethyl]ammonium-dimesylamide." Zeitschrift für Naturforschung B 57, no. 5 (May 1, 2002): 534–46. http://dx.doi.org/10.1515/znb-2002-0510.

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In order to study weak hydrogen bonds originating from inductively activated C(sp3)-H donor groups, low-temperature X-ray structures are reported for three onium salts of general formula BH+(MeSO2)2N-, where BH+ is Me3N+CH2CH2OH (1; orthorhombic, space group P212121, Z′ = 1), Me3N+CH2C(O)OH (2; orthorhombic, P212121, Z′ = 1), or Me2HN+CH2CH2NMe2 (3; monoclinic, P21/c, Z′ = 1). The asymmetric units consist of cationanion pairs assembled by an O-H···O=S hydrogen bond in 1, an O-H···N- bond in 2, and an N+-H ··· N- bond in 3. The packings display a plethora of short interionic C(sp3)-H···O/N contacts that are geometrically consistent with weak hydrogen bonding; those taken into consideration have normalized parameters d(H ··· O) ≤ 269 pm, d(H···N) ≤ 257 pm and θ(C-H···O/N) ≥ 127°. The roles of the weak hydrogen bonds are as follows: In structures 1 and 3, the anions are associated into corrugated layers, which intercalate catemers of cations (1) or stacks of discrete cations (3), whereas structure 2 involves cation catemers surrounded by four anion catemers and vice versa; moreover, all cations are linked to adjacent anions by several weak hydrogen bonds (and to one anion in particular by the strong H bond). Among the cation-anion interactions, the N+(CH2-H···)3O tripod pattern arising in 1 and 2 is of special interest.
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28

Klein, Erik, Vladimír Lukeš, Zuzana Cibulková, and Júlia Polovková. "Study of N–H, O–H, and S–H bond dissociation enthalpies and ionization potentials of substituted anilines, phenols, and thiophenols." Journal of Molecular Structure: THEOCHEM 758, no. 2-3 (January 2006): 149–59. http://dx.doi.org/10.1016/j.theochem.2005.10.015.

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29

Tan, Sang Loon, and Edward R. T. Tiekink. "2,2′-(Disulfanediyl)dibenzoic acid N,N-dimethylformamide monosolvate: crystal structure, Hirshfeld surface analysis and computational study." Acta Crystallographica Section E Crystallographic Communications 76, no. 7 (June 26, 2020): 1150–57. http://dx.doi.org/10.1107/s2056989020008257.

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The title 1:1 solvate, C14H10O4S2·C3H7NO, features a twisted molecule of 2,2′-dithiodibenzoic acid (DTBA), with the central C—S—S—C torsion angle being −88.57 (6)°, and a molecule of dimethylformamide (DMF). The carboxylic acid groups are, respectively, close to co-planar and twisted with respect to the benzene rings to which they are connected as seen in the CO2/C6 torsion angles of 1.03 (19) and 7.4 (2)°. Intramolecular, hypervalent S←O interactions are noted [S...O = 2.6140 (9) and 2.6827 (9) Å]. In the crystal, four-molecule aggregates are formed via DTBA-O—H...O(DMF) and DTBA-O—H...O(DTBA) hydrogen bonding, the latter via an eight-membered {...OHCO}2 homosynthon. These are linked into supramolecular layers parallel to (011) via benzene-C—H...O(DTBA) and DTBA-C=O...π(benzene) interactions, with the connections between these, giving rise to a three-dimensional architecture, being of the type benzene-C—H...π(benzene). An analysis of the calculated Hirshfeld surfaces indicates, in addition to the aforementioned intermolecular contacts, the presence of stabilizing interactions between a benzene ring and a quasi-π-system defined by O—H...O hydrogen bonds between a DTBA dimer, i.e. the eight-membered {...OCOH}2 ring system, and between a benzene ring and a quasi-π(OCOH...OCH) system arising from the DTBA-O—H...O(DMF) hydrogen bond. The inter-centroid separations are 3.65 and 3.49 Å, respectively.
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30

Manawar, Rohit B., Mitesh B. Gondaliya, Manish K. Shah, Mukesh M. Jotani, and Edward R. T. Tiekink. "2-{(1E)-[(E)-2-(2,6-Dichlorobenzylidene)hydrazin-1-ylidene]methyl}phenol: crystal structure, Hirshfeld surface analysis and computational study." Acta Crystallographica Section E Crystallographic Communications 75, no. 10 (September 10, 2019): 1423–28. http://dx.doi.org/10.1107/s2056989019012349.

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The title Schiff base compound, C14H10Cl2N2O, features an E configuration about each of the C=N imine bonds. Overall, the molecule is approximately planar with the dihedral angle between the central C2N2 residue (r.m.s. deviation = 0.0371 Å) and the peripheral hydroxybenzene and chlorobenzene rings being 4.9 (3) and 7.5 (3)°, respectively. Nevertheless, a small twist is evident about the central N—N bond [the C—N—N—C torsion angle = −172.7 (2)°]. An intramolecular hydroxy-O—H...N(imine) hydrogen bond closes an S(6) loop. In the crystal, π–π stacking interactions between hydroxy- and chlorobenzene rings [inter-centroid separation = 3.6939 (13) Å] lead to a helical supramolecular chain propagating along the b-axis direction; the chains pack without directional interactions between them. The calculated Hirshfeld surfaces point to the importance of H...H and Cl...H/H...Cl contacts to the overall surface, each contributing approximately 29% of all contacts. However, of these only Cl...H contacts occur at separations less than the sum of the van der Waals radii. The aforementioned π–π stacking interactions contribute 12.0% to the overall surface contacts. The calculation of the interaction energies in the crystal indicates significant contributions from the dispersion term.
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31

Yang, H. W., and B. M. Craven. "Charge Density Study of 2-Pyridone." Acta Crystallographica Section B Structural Science 54, no. 6 (December 1, 1998): 912–20. http://dx.doi.org/10.1107/s0108768198006545.

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The crystal structure of 2-pyridone has been redetermined from high-resolution X-ray data collected at 123 K. The molecule is in the lactam form. Bond lengths (corrected for rigid-body libration) and angles have been determined with s.u.'s of 0.001 Å and 0.1°, respectively. The hydrogen-bonded cyclic dimers which occur in the vapor and in solution are absent in the crystal where molecules are linked by N—H...O hydrogen bonds to form puckered chains. There also appears to be a weaker C—H...O interaction (H...O, 2.57 Å) and weak C—H...π or van der Waals interactions occurring on both sides of the pyridone ring. Following a refinement of the structure assuming Stewart's rigid pseudo-atom model, the electronic charge density distribution in the crystal and its Laplacian have been calculated for atoms at rest. The total electrostatic potential has been mapped for an isolated molecule and the molecular dipole moment has been determined [8.8 (19) D; 1D ≃ 3.33564 × 10−30 C m]. Critical points in the electron density have been located for the bonds within the molecule and for the molecular interactions cited above. For the C—H...π interactions, only the spherical components of the valence density for the pyridone ring atoms contribute effectively at the critical points. Hence, these may be better described as van der Waals interactions.
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32

Kaur, Rupinder preet, Damanjit Kaur, and Ritika Sharma. "Substituent effect on N–H bond dissociation enthalpies of carbamates: a theoretical study." Canadian Journal of Chemistry 93, no. 3 (March 2015): 279–88. http://dx.doi.org/10.1139/cjc-2014-0326.

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The present investigation deals with the study of the N–H bond dissociation enthalpies (BDEs) of the Y-substituted (NH2-C(=X)Y-R) and N-substituted ((R)(H)NC(=X)YH) carbamates (X, Y = O, S, Se; R = H, CH3, F, Cl, NH2), which have been evaluated using ab initio and density functional methods. The variations in N−H BDEs of these Y-substituted and N-substituted carbamates as the effect of substituent have been understood in terms of molecule stabilization energy (ME) and radical stabilization energy (RE), which have been calculated using the isodesmic reactions. The natural bond orbital analysis indicated that the electrodelocalization of the lone pairs of heteroatoms in the molecules and radicals affect the ME and RE values depending upon the type and site of substitution (whether N- or Y-). The variations in N−H BDEs depend upon the combined effect of molecule stabilization and radical stabilization by the various substituents.
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33

Guimarães, Heloísa A. B., Paula C. Cardoso, Rafael A. Decurcio, Lúcio J. E. Monteiro, Letícia N. de Almeida, Wellington F. Martins, and Ana Paula R. Magalhães. "Simplified Surface Treatments for Ceramic Cementation: Use of Universal Adhesive and Self-Etching Ceramic Primer." International Journal of Biomaterials 2018 (December 31, 2018): 1–7. http://dx.doi.org/10.1155/2018/2598073.

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The aim of this study was to evaluate the shear bond strength of resin cement and lithium disilicate ceramic after various surface treatments of the ceramic. Sixty blocks of ceramic (IPS e.max Press, Ivoclar Vivadent) were obtained. After cleaning, they were placed in polyvinyl chloride tubes with acrylic resin. The blocks were divided into six groups (n=10) depending on surface treatment: H/S/A - 10% Hydrofluoric Acid + Silane + Adhesive, H/S -10% Hydrofluoric Acid + Silane, H/S/UA - 10% Hydrofluoric Acid + Silane + Universal Adhesive, H/UA- 10% Hydrofluoric Acid + Universal Adhesive, MBEP/A - Monobond Etch & Prime + Adhesive, and MBEP - Monobond Etch & Prime. The light-cured resin cement (Variolink Esthetic LC, Ivoclar Vivadent) was inserted in a mold placed over the treated area of the ceramics and photocured with an LED for 20 s to produce cylinders (3 mm x 3 mm). The samples were subjected to a shear bond strength test in a universal test machine (Instron 5965) by 0.5 mm/min. ANOVA and Tukey tests showed a statistically significant difference between groups (p<0.05). The results of the shear strength test were H/S/A (9.61±2.50)A, H/S (10.22±3.28)A, H/S/UA (7.39±2.02)ABC, H/UA (4.28±1.32)C, MBEP/A (9.01±1.97)AB, and MBEP (6.18±2.75)BC. The H/S group showed cohesive failures, and the H/UA group was the only one that presented adhesive failures. The conventional treatment with hydrofluoric acid and silane showed the best bond strength. The use of a new ceramic primer associated with adhesive bonding obtained similar results to conventional surface treatment, being a satisfactory alternative to replace the use of hydrofluoric acid.
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34

Bombicz, P., M. Czugler, A. Kálmán, and I. Kapovits. "A database study of the bonding and conformation of bis-sulfonylamide/-imide moieties." Acta Crystallographica Section B Structural Science 52, no. 4 (August 1, 1996): 720–27. http://dx.doi.org/10.1107/s0108768196003977.

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The bonding and conformational characteristics of bissulfonylamides and analogous imides are compared. Structures (44 altogether) containing R—SO2—NQ—SO2—R′ units were retrieved from the Cambridge Structural Database. They are either neutral (Q-H, alkyl or aryl groups, hereto atoms such as O and S) or charged (Q = e−) and bearing the functions R, R′ = Me, Et or Ph, respectively. The principal conformations of the —SO2—NQ—SO2— bridge (open versus folded) are represented by sodium dibenzenesulfonamide (BSULFA) and dibenzenesulfonimide (NABSUF). In addition to the compounds possessing Q = alkyl or aryl functions, complexes with N-metal bonds could clearly be distinguished. The dominant forms of SVI—X (X = O, N C) bonds are characterized and correlated with the bond angles formed around the S atoms. The marked difference between the archetypes of the S—N bonds (i.e. nitrogen charged or neutral) indicated that the interdependence of the S—X bonds, i.e. the size and the shape of the SVI[O,O′,N,C] tetrahedra, are principally governed by the environment of the N atoms. The conformation symmetry and dissymmetry of the charged and neutral —SO2—NQ—SO2— moieties are described in terms of the internal rotations about the bonds in the R—S—N—S—R′ fragment.
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35

Radu, Luana-Flavia, Amr A. A. Attia, Radu Silaghi-Dumitrescu, Alexandru Lupan, and R. Bruce King. "Reversible complexation of ammonia by breaking a manganese–manganese bond in a manganese carbonyl ethylenedithiolate complex: a theoretical study of an unusual type of Lewis acid." Dalton Transactions 48, no. 1 (2019): 324–32. http://dx.doi.org/10.1039/c8dt04217a.

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The addition of bases such as ammonia and trimethylphosphine to H2C2S2Mn2(CO)6 to give yellow 1 : 1 adducts is shown to break the metal–metal bond rather than displace the coordinated double bond.
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36

Pasto, Daniel J. "A theoretical study on the modes of homolytic bond fragmentation in HnXYHm, HSXY and HS(O)XY systems." Journal of Molecular Structure 446, no. 1-2 (April 1998): 75–92. http://dx.doi.org/10.1016/s0022-2860(97)00399-2.

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37

QIN, SONG, CHANGWEI HU, and HUAQING YANG. "THEORETICAL STUDY ON THE MECHANISM OF THE REACTION OF Ni(d10 1S) + H2 + CO2 → NiCO + H2O." Journal of Theoretical and Computational Chemistry 04, no. 02 (June 2005): 449–59. http://dx.doi.org/10.1142/s0219633605001593.

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The detailed singlet potential energy surface (PES) of the reaction of Ni ( d 10 1 S ) + H 2 + CO 2→ NiCO + H2O is investigated at the CCSD(T) /6-311+ G(2d,2p) // B3LYP /6-311+ G(2d,2p) levels in order to explore possible reaction mechanism of CO 2 hydrogenation on Ni center. The calculation predicts that the co-interacted H 2 involved C–O bond cleavage of CO 2 molecule is prior to the dissociation of adsorbed H 2 molecule, and the entire reaction is exothermic by 297.3 kJ/mol with an energy barrier of 137.7 kJ/mol. The rate-determining step (RDS) for the overall reaction is predicted to be the insertion of Ni into the C–O bond of the CO 2 moiety.
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38

Kansiz, Sevgi, Digdem Tatlidil, Necmi Dege, Feyzi Alkim Aktas, Samir Osman Mohammed Al-Asbahy, and Aysen Alaman Agar. "Crystal structure and molecular docking study of (E)-2-{[(E)-2-hydroxy-5-methylbenzylidene]hydrazinylidene}-1,2-diphenylethan-1-one." Acta Crystallographica Section E Crystallographic Communications 77, no. 6 (May 28, 2021): 658–62. http://dx.doi.org/10.1107/s2056989021005442.

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The title compound, C22H18N2O2, is a Schiff base that exists in the phenol–imine tautomeric form and adopts an E configuration with respect to the C=N bond. The molecular structure is stabilized by an O—H...N hydrogen bond, forming an S(6) ring motif. In the crystal, pairs of C—H...O hydrogen bonds link the molecules to form inversion dimers. Weak π–π stacking interactions along the a-axis direction provide additional stabilization of the crystal structure. The molecule is non-planar, the aromatic ring of the benzaldehyde residue being nearly perpendicular to the phenyl and 4-methylphenol rings with dihedral angles of 88.78 (13) and 82.26 (14)°, respectively. A molecular docking study between the title molecule and the COVID-19 main protease (PDB ID: 6LU7) was performed, showing that it is a potential agent because of its affinity and ability to adhere to the active sites of the protein.
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39

Sun, Tao, Kejian Ma, Zhihua Chen, Jin Chen, and Yuhao Zhu. "Experimental Study on Bond-Slip Behavior between H-Shaped Steel and Gypsum Cover in SGFCG." Journal of Engineering 2020 (June 25, 2020): 1–12. http://dx.doi.org/10.1155/2020/8738754.

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Nine push-out specimens of H-shaped steel with gypsum cover (HSG) are designed to study the bond-slip behavior between steel and gypsum in steel grid frame filling with cast-in-situ gypsum (SGFCG). Three main factors including gypsum compression strength (fcu), gypsum cover thickness (Cs), and steel-gypsum connected length (la) are considered. It is shown by the test results that the ultimate average bond strength is within [0.333–0.456] MPa, and the residual strength is about 90–98% of the ultimate strength. Both gypsum cover thickness and steel-gypsum connected length have evident influence on the bond strength, while the effect of gypsum compression strength is not obvious. Based on the test data, the formulas of average bond strength characteristics (τs¯, τu¯, and τr¯) and slip characteristics (Su and Sr) are established by statistical fitting. Furthermore, the bond-slip constitutive relationship (τ¯−S) is recommended.
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40

Remko, Milan. "Ab initio study of the configuration and protonation of thiocarbamic acid." Collection of Czechoslovak Chemical Communications 54, no. 2 (1989): 297–302. http://dx.doi.org/10.1135/cccc19890297.

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The ab initio SCF method was applied to a conformation study of thiocarbamic acid. The 3-21 G calculations revealed that the trans isomer with the O-H···S intramolecular hydrogen bond is more stable than the cis isomer. The calculated rotational barrier for the rotation about the central C-N bond is very high, 125.5 kJ mol-1; this value, however, decreased to 106.2 kJ mol-1 by electron correlation determined at the 2nd order Moller-Plesset perturbation level. Proton affinities for the protonation of the electronegative atoms in the acid increase in the order of the atoms N, O and S. Changes in the Mulliken gross atomic populations are examined in dependence on the configuration and protonation of the acid.
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41

Jang, Eun-Yoo, Jung J. Kim, and Doo-Yeol Yoo. "Dynamic Pullout Behavior of Multiple Steel Fibers in UHPC: Effects of Fiber Geometry, Inclination Angle, and Loading Rate." Materials 12, no. 20 (October 15, 2019): 3365. http://dx.doi.org/10.3390/ma12203365.

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This study examined the influences of fiber geometry, inclination angle, and loading rate on the pullout behavior of multiple steel fibers in ultra-high-performance concrete (UHPC). For this, two different steel fiber types, i.e., straight (S-) and hooked (H-), four different inclination angles (0°–60°), and four different loading rates (0.018 mm/s to 1200 mm/s) were considered. Test results indicated that the pullout performance of S-fibers in UHPC was improved by increasing the loading rate. The highest maximum pullout load of the S-fiber was obtained at the inclination angle of 30° or 45°. The maximum pullout loads of H-fibers also increased with increases in the loading rate, while their slip capacities rather decreased. No specific inclination angle was identified in the case of H-fibers that caused the highest maximum pullout load. The H-fibers yielded higher average bond strengths than S-fibers, but similar or even smaller pullout energies under the impact loads. The aligned S-fiber in UHPC was most sensitive to the loading rate compared to the inclined S-fiber and aligned H-fiber. The rate sensitivity became moderate with the fiber inclination angle. Consequently, the aligned S-fiber was recommended to achieve the best energy absorption capacity and interfacial bond strength at various impact loads.
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42

Yu, Sujing, Dongzhi Zhang, Wenjing Pan, and Jingbin Zeng. "Adsorption of atmospheric gas molecules (NH3, H2S, CO, H2, CH4, NO, NO2, C6H6 and C3H6O) on two-dimensional polyimide with hydrogen bonding: a first-principles study." New Journal of Chemistry 45, no. 11 (2021): 5240–51. http://dx.doi.org/10.1039/d0nj06013e.

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In this study, we investigated the effects of hydrogen bond acceptors on the surface of two-dimensional polyimide towards NH3, H2S, CO, H2, CH4, NO, NO2, C6H6 and C3H6O gas molecules through first-principles study based on density functional theory.
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43

Shunje, Kelly N., Boris B. Averkiev, and Christer B. Aakeröy. "Influence of Multiple Binding Sites on the Supramolecular Assembly of N-[(3-pyridinylamino) Thioxomethyl] Carbamates." Molecules 27, no. 12 (June 8, 2022): 3685. http://dx.doi.org/10.3390/molecules27123685.

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In this study, we investigated how the presence of multiple intermolecular interaction sites influences the heteromeric supramolecular assembly of N-[(3-pyridinylamino) thioxomethyl] carbamates with fluoroiodobenzenes. Three targets—R-N-[(3-pyridinylamino) thioxomethyl] carbamate (R = methyl, ethyl, and isobutyl)—were selected and crystallized, resulting in three parent structures, five co-crystals, and one co-crystal solvate. Three hydrogen-bonded parent crystal structures were stabilized by N-H···N hydrogen bonding and assembled into layers that stacked on top of one another. Molecular electrostatic potential surfaces were employed to rank binding sites (Npyr > C=S > C=O) in order to predict the dominant interactions. The N-H⋯H hydrogen bond was replaced by I⋯Npyr in 3/6 cases, I⋯C=S in 4/6 cases, and I⋯O=C in 1 case. Interestingly, the I⋯C=S halogen bond coexisted twice with I⋯Npyr and I⋯O=C. Overall, the MEPs were fairly reliable for predicting co-crystallization outcomes; however, it is crucial to also consider factors such as molecular flexibility. Finally, halogen-bond donors are capable of competing for acceptor sites, even in the presence of strong hydrogen-bond donors.
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44

Vahdani Alviri, Banafsheh, Mehrdad Pourayoubi, Abolghasem Farhadipour, Marek Nečas, and Valerio Bertolasi. "A combined X-ray crystallography and theoretical study of N—H...OX (X is =P and —C) hydrogen bonds in two new structures with a (C—O)2(N)P(=Y) (Y is O and S) skeleton." Acta Crystallographica Section C Structural Chemistry 74, no. 12 (November 13, 2018): 1610–21. http://dx.doi.org/10.1107/s2053229618014006.

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The crystal structures of N,N′-(cyclohexane-1,4-diyl)bis(O,O′-diphenylphosphoramide), C30H32N2O6P2 or (C6H5O)2P(O)(1-NH)(C6H10)(4-NH)P(O)(OC6H5)2, (I), and N,N′-(1,4-phenylene)bis(O,O′-dimethylthiophosphoramide), C10H18N2O4P2S2 or (CH3O)2P(S)(1-NH)(C6H4)(4-NH)P(S)(OCH3)2, (II), have been investigated. In the structure of (I), with an (O)2(N)P(O) skeleton, two symmetry-independent phosphoramide molecules are linked through N—H...O=P hydrogen bonds. In the structure of (II), with an (O)2(N)P(S) skeleton, the ester O atoms take part in N—H...O—C hydrogen bonds as acceptors; the P=S groups do not participate in hydrogen-bonding interactions. The strengths of these hydrogen bonds were evaluated, using quantum chemical calculations with the GAUSSIAN09 software package at the B3LYP/6-311G(d,p) level of theory. For this, LP(O) to σ*(NH) charge transfers were studied, according to the second-order perturbation theory in natural bond orbital (NBO) methodology, for a three-component cluster of hydrogen-bonded molecules for both structures, including all of the independent N—H...O hydrogen bonds observed in the crystal packing. The details of the intermolecular interactions were studied by Hirshfeld surface maps and two-dimensional fingerprint plots.
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45

Borges dos Santos, Rui M., Vânia S. F. Muralha, Catarina F. Correia, Rita C. Guedes, Benedito J. Costa Cabral, and José A. Martinho Simões. "S−H Bond Dissociation Enthalpies in Thiophenols: A Time-Resolved Photoacoustic Calorimetry and Quantum Chemistry Study†." Journal of Physical Chemistry A 106, no. 42 (October 2002): 9883–89. http://dx.doi.org/10.1021/jp025677i.

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46

Fonseca, Beatriz Maria, Daphne Camara Barcellos, César Rogério Pucci, Eduardo Bresciani, and Maria Amélia Máximo de Araújo. "Influence of chlorhexidine on longitudinal bond strength to dentin: in vitro study." Brazilian Dental Science 20, no. 1 (February 20, 2017): 17. http://dx.doi.org/10.14295/bds.2017.v20i1.1315.

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<p><strong>Objective</strong>: This study evaluated the effect of 0.2% chlorhexidine gluconate solution used as an therapeutic primer on the long-term bond strength of etch-and-rinse adhesive to dentin. <strong>Material</strong> <strong>and</strong> <strong>Methods</strong>: Bovine incisors were worn to expose an area of dentin and were divided into 2 groups: Group C (Control) - acid etching with 37% phosphoric acid + Single Bond; Group CHX (0.2% CHX) - acid etching with 37% phosphoric acid + 0.2% CHX for 30 s + Single Bond. Blocks of composite were fabricated and stored for 24 h or 6 months, sectioned into beams and submitted to microtensile tests. Results were analyzed by two-way ANOVA and Tukey tests. <strong>Results</strong>: Mean (±SD) values (in MPa) were as follow: Group CHX/24h - 41.8(±2.62)A; Group C/24h - 40.8(±3.35)AB; Group CHX/6 months – 36.4(±3.52)B; Group CHX/6 months - 26.1(±1.54)C. <strong>Conclusion</strong>: CHX improve the imediatte bond strength of resin-dentin and significantly lowered the loss of bond strength after 6 months water storage as seen in the control bonds.</p><p><strong>Keywords</strong></p><p>Tensile bond strength; Dentin; Total-etch adhesives; Chlorhexidine gluconate.</p>
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47

Li, Lijuan, Dajing Qin, Zhijun Xu, and Yong Feng. "Study on Strengthening Mechanism of Epoxy Resin/Rubber Concrete Interface by Molecular Dynamics Simulation." Advances in Civil Engineering 2022 (January 11, 2022): 1–9. http://dx.doi.org/10.1155/2022/5100758.

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Rubber concrete has high environmental and economic benefits. However, the difference in the physical and chemical properties of the interface causes a weak interface between rubber and concrete, which limits the use of rubber concrete to a certain extent. Based on the macroexperiment of epoxy resin (EP) modified rubber concrete, from the nanoscale level, three interface models of Rh (natural rubber)/C-S-H, EP/C-S-H, and Rh/EP/C-S-H were constructed by molecular dynamics simulation to explore the interaction between epoxy resin and rubber cement-based interface and reveal its microreinforcement mechanism. The results of interaction energy, radial distribution function, and mean square displacement show that the addition of EP not only improves the interface interaction energy between Rh and C-S-H but also provides a large number of hydrogen bond donors and receptors, promotes the diffusion of Ca, and increases the adhesion between Rh and cement matrix. The results of the analysis of mechanical properties show that the elastic modulus of the rubber concrete interface model is improved and the interface properties are improved after adding EP.
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48

Grześkiewicz, Anita M., Agata Ostrowska, Dmytro Borzylo, and Maciej Kubicki. "When solvent becomes reactant: a study of 6-aminothiocytosine derivatives." Acta Crystallographica Section C Structural Chemistry 76, no. 10 (September 29, 2020): 992–99. http://dx.doi.org/10.1107/s2053229620012504.

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The dissolution of 6-aminothiocytosine in common solvents (such as methanol, dimethyl sulfoxide and dichloromethane) under alkaline conditions is shown to afford new compounds with a 6-aminothiocytosine skeleton: 2,2′-disulfanediylbis(pyrimidine-4,6-diamine) (1), C8H10N8S2, 2,2′-[methanediylbis(sulfanediyl)]bis(pyrimidine-4,6-diamine) (2), C9H12N8S2, 2-[(methoxymethyl)sulfanyl]pyrimidine-4,6-diamine (3), C6H10N4OS, and poly[(μ-4,6-diaminopyrimidine-2-sulfinato)potassium(I)] (4), [K(C4H5N4O2S)] n . The crystal architectures of these compounds are found to be strongly influenced by extensive hydrogen-bond networks, although some individual features are also observed. Specifically, 1 is characterized by very short C—H...N hydrogen bonds, 2 features apparently weak and long C—H...π, C—H...S and π–π contacts as the greatest contributors to stabilization energy, while 3 contains ribbons of molecules formed by centrosymmetric dimers of two types, and 4 is characterized by layers with principal structural units comprising distorted six-molecule rings. The intermolecular interactions in 1–4 are characterized in terms of their geometry, topology and energy, and the corresponding results are confirmed and visualized using Hirshfeld surface analysis.
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Anane, Hafid, Soufiane Houssame, Abdelali Guerraze, Abdeladim Guermoune, Abderrahim Boutalib, Abedellah Jarid, Ignacio Nebot-Gil, and Francisco Tomás. "A G2(MP2) theoretical study of substituent effects on H3BNHnCl3−n (n= 3-0) donor-acceptor complexes." Open Chemistry 6, no. 3 (September 1, 2008): 400–403. http://dx.doi.org/10.2478/s11532-008-0029-0.

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AbstractThe complexation energies of H3BNHnCl3−n (n= 3-0) complexes and the proton affinities of NHnCl3−n compounds have been computed at the G2(MP2) level of theory. G2(MP2) results show that the successive chlorine substitution on the ammonia decreases both the basicity of the NHnCl3−n ligands and the stability of H3BNHnCl3−n complexes. The findings are interpreted in terms of the rehybridisation of the nitrogen lone-pair orbital. The NBO partitioning scheme shows that the variation of the N-H and N-Cl bond lengths, upon complexation, is due to variation of “s” character in these bonds.
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50

McMullan, R. K., T. F. Koetzle, and C. J. Fritchie. "Low-Temperature Neutron Diffraction Study of the Silver Perchlorate–Benzene π Complex." Acta Crystallographica Section B Structural Science 53, no. 4 (August 1, 1997): 645–53. http://dx.doi.org/10.1107/s0108768197000712.

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The crystal structure of the AgClO4.C6H6 \pi complex, earlier determined by X-ray diffraction at room temperature, has been redetermined at 18, 78 and 158 K by neutron diffraction. Crystal data: orthorhombic, space group Cmcm, Z = 4, F(000) = 225.318 fm, T: 18, 17, 158 K; D x = 2.591 (2), 2.570 (1), 2.523 (1) g cm−1; \mu n = 0.166, 0.165, 0.162 cm−1; a = 7.913 (1), 7.973 (1), 8.100 (1), 8.336 (1) Å (at 295 K); b = 7.837 (2), 7.857 (1), 7.902 (1), 7.996 (1) Å (at 295 K); c = 11.798 (3), 11.777 (2), 11.739 (2), 11.638 (2) Å (at 295 K); wR(F 2) = 0.037, 0.035, 0.045, S = 1.18, 1.08, 1.10 for 782, 628, 800 reflections and 51 variable parameters. This study confirms the principal features reported in the X-ray investigation and reveals details of structure not observable at room temperature. Distortions of the benzene molecule from D 6h symmetry ascribed to Ag+...C6H6 interactions are small, but significant. At 18 K the two C—C bonds complexed by Ag+ are 1.405 (1) Å in length; the other four are 1.398 (1) Å. The C—H bonds are equal in length at 1.087 (2) (two) and 1.089 (1) Å (four). The H atoms nearest to Ag+ are displaced 0.064 (1) Å from the C6 plane, away from the silver. The shortest Ag+...C distance of the complex is 2.565 (1) Å. This value and bond lengths of the benzene molecule are invariant between 18 and 158 K within 2 e.s.d.'s or less. The nonequivalent bond lengths of ClO^{-}_4, 1.451 (1) (two) and 1.441 (1) Å (two) at 18 K, are foreshortened by −0.007 and −0.005 Å at 158 K by effects of thermal motion. The O—Cl—O angles, 109.08 (7), 109.98 (2) and 107.83 (8)° at 18 K, are virtually unchanged by temperature. The Ag+...ClO^{-}_4 interactions occur at Ag+...O distances of 2.785 (1) and 2.612 (1) Å (18 K), where the shorter values involve ClO^{-}_4 acting as a bidentate group. Rigid-body and riding-motion models do not adequately account for the observed temperature dependence of bond lengths in ClO^{-}_4 nor provide significant corrections to the C6H6 bond lengths at 18, 78 and 158 K beyond their uncertainty limits. A harmonic potential rationalizes the motion of Ag+ at these three temperatures.
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