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Articoli di riviste sul tema "Complexe homochiral"

Autore: Grafiati
Pubblicato: 21 dicembre 2024

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1

Ma, Ting-Ting, Xiao-Peng Sun, Zi-Shuo Yao e Jun Tao. "Homochiral versus racemic polymorphs of spin-crossover iron(ii) complexes with reversible LIESST effect". Inorganic Chemistry Frontiers 7, n. 5 (2020): 1196–204. http://dx.doi.org/10.1039/c9qi01590f.

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2

Roithová, Jana. "Diastereoisomeric proton-bound complexes of 1,5-diaza-cis-decalin in the gas phase". Collection of Czechoslovak Chemical Communications 74, n. 2 (2009): 243–54. http://dx.doi.org/10.1135/cccc2008185.

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Diastereoisomeric proton-bound complexes of 1,5-diaza-cis-decalin (1) with butan-2-amine (2) are studied by means of the DFT calculations and mass spectrometry. The calculations reveal that 2 is bound via proton to only one nitrogen atom of the bicyclic base 1. The homochiral complex is favored by about 4 kJ/mol over the heterochiral complex. For a more loosely bound ion-pair complex [(1H)I(2H)]+ of the protonated bases 1 and 2 with an iodine counterion the energy difference drops to about 2 kJ/mol. Chiral effects in the formation of [(1)H(2)]+ are studied by the collision-induced dissociation of [(1H)I(2H)]+ generated by the electrospray ionization of the solution of [1·Cu(OH)I] and 2 in acetonitrile. The dominant fragmentation of [(1H)I(2H)]+ leads to 1·H+ and 2·HI, which is at small collision energies accompanied by the elimination of HI leading to the desired [(1)H(2)]+ ion. The chiral effect of 1.2 is determined in favor for the formation of the homochiral complex [(1)H(2)]+.
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3

Liu, Yu-Ling, Jia-Zhen Ge, Zhong-Xia Wang e Ren-Gen Xiong. "Metal–organic ferroelectric complexes: enantiomer directional induction achieved above-room-temperature homochiral molecular ferroelectrics". Inorganic Chemistry Frontiers 7, n. 1 (2020): 128–33. http://dx.doi.org/10.1039/c9qi01197h.

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4

Howard, Philip W., G. Richard Stephenson e Stephen C. Taylor. "Convenient access to homochiral tricarbonyliron complexes". Journal of the Chemical Society, Chemical Communications, n. 24 (1988): 1603. http://dx.doi.org/10.1039/c39880001603.

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5

Sapotta, Meike, Peter Spenst, Chantu R. Saha-Möller e Frank Würthner. "Guest-mediated chirality transfer in the host–guest complexes of an atropisomeric perylene bisimide cyclophane host". Organic Chemistry Frontiers 6, n. 7 (2019): 892–99. http://dx.doi.org/10.1039/c9qo00172g.

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6

Gao, Wan-Qing, Yin-Shan Meng, Chun-Hua Liu, Yao Pan, Tao Liu e Yuan-Yuan Zhu. "Spin crossover and structural phase transition in homochiral and heterochiral Fe[(pybox)2]2+ complexes". Dalton Transactions 48, n. 19 (2019): 6323–27. http://dx.doi.org/10.1039/c8dt04893b.

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7

Míšek, Jiří, Miloš Tichý, Irena G. Stará, Ivo Starý e Detlef Schröder. "Preferential formation of homochiral silver(I) complexes upon coordination of two aza[6]helicene ligands to Ag+ ions". Collection of Czechoslovak Chemical Communications 74, n. 2 (2009): 323–33. http://dx.doi.org/10.1135/cccc2008184.

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By means of selective deuterium labeling of 1-aza[6]helicene combined with resolution of the enantiomers, chiral discrimination in silver(I)-bound dimers of the type [LAgL′]+ is probed by electrospray mass spectrometry. The analysis of the results reveals a pronounced preference for the formation of homochiral dimers (P,P and M,M, respectively) over the statistically preferred heterochiral variant (P,M), which is fully consistent with previous data about the formation of homochiral dimers in the condensed phase. Further, competitive experiments with mixtures of 1- and 2-aza[6]helicene suggest a largely preferred coordination of 1-aza[6]helicene to the silver(I) cation.
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8

Kataeva, Olga, Kirill Metlushka, Kamil Ivshin, Zilya Yamaleeva, Ruzal Zinnatullin, Kristina Nikitina, Elena Badeeva et al. "Supramolecular chirality in the crystals of mononuclear and polymeric cobalt(ii) complexes with enantiopure and racemic N-thiophosphorylated thioureas". CrystEngComm 23, n. 10 (2021): 2081–90. http://dx.doi.org/10.1039/d0ce01871f.

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The control of stereochemistry in Co(ii) complexes was provided by additional pyridine and pyrazine ligands. 1D and 2D supramolecular homochiral arrangements in racemic crystals of mononuclear complexes are transferred to their polymeric counterparts.
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9

Jiao, Luyang, Mengying Du, Yameng Hou, Yuan Ma e Xianglei Kong. "Homochiral or Heterochiral: A Systematic Study of Threonine Clusters Using a FT ICR Mass Spectrometer". Symmetry 14, n. 1 (6 gennaio 2022): 86. http://dx.doi.org/10.3390/sym14010086.

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The strong chiral preferences of some magic clusters of amino acids have attracted continually increasing interests due to their unique structures, properties and possible roles in homochirogenesis. However, how chirality can influence the generation and stability of cluster ions in a wild range of cluster sizes is still unknown for most amino acids. In this study, the preference for threonine clusters to form homochiral and heterochiral complex ions has been investigated by electrospray ionization (ESI) mass spectrometry. Abundant cluster [Thrn+mH]m+ ions (7 ≤ n ≤ 78, 1 ≤ m ≤ 5) have been observed for both samples of enantiopure (100% L) and racemic (50:50 L:D) threonine solutions. Further analyses of the spectra show that the [Thr14+2H]2+ ion is characterized by its most outstanding homochiral preference, and [Thr7+H]+ and [Thr8+H]+ ions also clearly exhibit their homochiral preferences. Although most of the triply charged clusters (20 ≤ n ≤ 36) are characterized by heterochiral preferences, the quadruply charged [Thrn+4H]4+ ions (40 ≤ n ≤ 59) have no obvious chiral preference in general. On the other hand, a weak homochiral preference exists for most of the quintuply charged ions observed in the experiment.
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10

Fowler, Jonathan M., Flora L. Thorp-Greenwood, Stuart L. Warriner, Charlotte E. Willans e Michaele J. Hardie. "M12L8 metallo-supramolecular cube with cyclotriguaiacylene-type ligand: spontaneous resolution of cube and its constituent host ligand". Chemical Communications 52, n. 56 (2016): 8699–702. http://dx.doi.org/10.1039/c6cc04130b.

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11

Ren, Min, Zhong-Li Xu, Ting-Ting Wang, Song-Song Bao, Ze-Hua Zheng, Zai-Chao Zhang e Li-Min Zheng. "Homochiral mononuclear Dy-Schiff base complexes showing field-induced double magnetic relaxation processes". Dalton Transactions 45, n. 2 (2016): 690–95. http://dx.doi.org/10.1039/c5dt03800f.

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Homochiral mononuclear complexes (Et3NH)[Dy((R,R)/(S,S)-3-NO2salcy)2] (1R/1S), where 3-NO2salcyH2 is N,N′-(1,2-cyclohexanediylethylene)bis(3-nitrosalicylideneiminato), are reported, and their optical and magnetic behaviors are studied.
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12

Horie, Miki, Naoki Ousaka, Daisuke Taura e Eiji Yashima. "Chiral tether-mediated stabilization and helix-sense control of complementary metallo-double helices". Chemical Science 6, n. 1 (2015): 714–23. http://dx.doi.org/10.1039/c4sc02275k.

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Control of the helical sense and stability enhancement of PtII-linked double helices by interstrand cross-linking using chiral diphosphines and complete homochiral self-sorting is demonstrated.
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13

García-Rubiño, M. E., M. C. Núñez-Carretero, D. Choquesillo-Lazarte, J. M. García-Ruiz, Yolanda Madrid e J. M. Campos. "Stereospecific alkylation of substituted adenines by the Mitsunobu coupling reaction under microwave-assisted conditions". RSC Adv. 4, n. 43 (2014): 22425–33. http://dx.doi.org/10.1039/c4ra01968g.

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The Mitsunobu reaction under microwave-assisted conditions reveals a complete inversion of the stereogenic centre of the secondary alcohol giving an alkylated purine linked to a homochiral six-membered ring.
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14

Bagi, Péter, Réka Herbay, Gábor Györke, Péter Pongrácz, László Kollár, István Timári, László Drahos e György Keglevich. "Preparation of Palladium(II) Complexes of 1-substituted-3-phospholene Ligands and their Evaluation as Catalysts in Hydroalkoxycarbonylation". Current Organic Chemistry 23, n. 25 (14 gennaio 2020): 2873–79. http://dx.doi.org/10.2174/1385272823666191204151311.

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: A series of palladium(II) complexes incorporating 1-substituted-3-methyl-3- phospholenes as the P-ligands were prepared from phospholene oxides by deoxygenation followed by complexation with PdCl2(PhCN)2. The two 1-substituted-3-methyl-3- phospholene ligands were trans position to each other in the Pd(II)-complexes. As the ligands contain a P-stereogenic center, the Pd-complexes were obtained as a 1:1 mixture of two stereoisomers, the homochiral (R,R and S,S) and the meso (R,S) forms, when racemic starting materials were used. An optically active Pd-complex containing (R)-1-propyl- 3-phospholene ligand was also prepared. Catalytic activity of an aryl- and an alkyl-3- phospholene-palladium(II)-complex was evaluated in hydroalkoxycarbonylation of styrene. The alkyl-derivative showed higher activity and selectivity towards the formation of the esters of 3-phenylpropionic acid. However, the overall activity of these PdCl2(phospholene)2-type complexes was low.
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15

Lincoln, Per, e Bengt Nordén. "Binding of dimeric homochiral ruthenium complexes to DNA". Journal of Inorganic Biochemistry 59, n. 2-3 (agosto 1995): 156. http://dx.doi.org/10.1016/0162-0134(95)97264-q.

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16

Weller, Michael G. "The Mystery of Homochirality on Earth". Life 14, n. 3 (6 marzo 2024): 341. http://dx.doi.org/10.3390/life14030341.

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Homochirality is an obvious feature of life on Earth. On the other hand, extraterrestrial samples contain largely racemic compounds. The same is true for any common organic synthesis. Therefore, it has been a perplexing puzzle for decades how these racemates could have formed enantiomerically enriched fractions as a basis for the origin of homochiral life forms. Numerous hypotheses have been put forward as to how preferentially homochiral molecules could have formed and accumulated on Earth. In this article, it is shown that homochirality of the abiotic organic pool at the time of formation of the first self-replicating molecules is not necessary and not even probable. It is proposed to abandon the notion of a molecular ensemble and to focus on the level of individual molecules. Although the formation of the first self-replicating, most likely homochiral molecule, is a seemingly improbable event, on a closer look, it is almost inevitable that some homochiral molecules have formed simply on a statistical basis. In this case, the non-selective leap to homochirality would be one of the first steps in chemical evolution directly out of a racemic “ocean”. Moreover, most studies focus on the chirality of the primordial monomers with respect to an asymmetric carbon atom. However, any polymer with a minimal size that allows folding to a secondary structure would spontaneously lead to asymmetric higher structures (conformations). Most of the functions of these polymers would be influenced by this inherently asymmetric folding. Furthermore, a concept of physical compartmentalization based on rock nanopores in analogy to nanocavities of digital immunoassays is introduced to suggest that complex cell walls or membranes were also not required for the first steps of chemical evolution. To summarize, simple and universal mechanisms may have led to homochiral self-replicating systems in the context of chemical evolution. A homochiral monomer pool is deemed unnecessary and probably never existed on primordial Earth.
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17

Breu, Josef, e Andrea Zwicknagel. "Chirale Erkennung bei Tris(diimin)-Metallkomplexen, 10. Vergleich der intermolekularen Wechselwirkungs- und Packungsmuster in der Reihe [Cr(bpy)3]n+(PF6)n (n = 0 – 3) / Chiral Recognition among Tris(diimine)-metal Complexes, 10. Comparison of Intermolecular Interactions and Packing Patterns in the Series [Cr(bpy)3]n+(PF6)n (n = 0–3)". Zeitschrift für Naturforschung B 59, n. 9 (1 settembre 2004): 1015–25. http://dx.doi.org/10.1515/znb-2004-0911.

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Due to their conformational rigidity, the corrugated, chiral molecular structure, and the variability in the central metal and its oxidation state, [M(bpy)3]n+ complexes are particularly well suited to study chiral recognition and to identify intermolecular interaction patterns in the crystalline state. For [Cr(bpy)3]n+(PF6)n (n=0 - 3) four oxidation states are readily accessible which allows to investigate the influence of the cation/anion ratio on the observed packing patterns.The crystal structures of all four oxidation states are governed by so-called ‘π-π-interactions’. Apparently, in molecular salts the Madelung energy is less important as compared to classical inorganic salts.Interestingly, [Cr(bpy)3](PF6) and [Cr(bpy)3](PF6)2 comprise the same homochiral layers. However, while the former crystallises as true racemate, the latter spontaneously resolves into a conglomerate. This two-dimensional building block of homochiral layers is the most popular structural motif in this class of compounds which has been observed in a great variety of racemic and homochiral stackings.
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18

Kataeva, Olga, Kirill Metlushka, Zilya Yamaleeva, Kamil Ivshin, Ruzal Zinnatullin, Kristina Nikitina, Dilyara Sadkova, Elena Badeeva, Oleg Sinyashin e Vladimir Alfonsov. "Chirality Control in Crystalline Ni(II) Complexes of Thiophosphorylated Thioureas". Crystals 9, n. 12 (20 novembre 2019): 606. http://dx.doi.org/10.3390/cryst9120606.

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Chirality control over the formation of Ni(II) complexes with chiral thiophosphorylated thioureas was achieved via breaking the symmetry of nickel coordination geometry by the introduction of the pyridine ligand, while centrosymmetric meso-complexes are formed from racemic ligands in case of square-planar nickel coordination. Centrosymmetric heterochiral arrangement is observed in crystals of ligands themselves through N–H⋅⋅⋅S hydrogen bonds in intermolecular dimers. Molecular homochirality in tetragonal pyramidal complexes is further transferred to supramolecular homochiral arrangement via key–lock steric interactions.
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19

Kumar, Navnita, Sadhika Khullar e Sanjay K. Mandal. "Controlling the self-assembly of homochiral coordination architectures of CuII by substitution in amino acid based ligands: synthesis, crystal structures and physicochemical properties". Dalton Transactions 44, n. 12 (2015): 5672–87. http://dx.doi.org/10.1039/c4dt03643c.

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In this paper we report six chiral ligands based on l-tyrosine, l-serine and l-phenylalanine and their homochiral CuII complexes to study the effect of various substitutions in the ligands on the formation of diverse coordination architectures.
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20

Liu, Cai-Ming, Xiang Hao e Xi-Li Li. "Assembly of Homochiral Magneto-Optical Dy6 Triangular Clusters by Fixing Carbon Dioxide in the Air". Molecules 29, n. 14 (19 luglio 2024): 3402. http://dx.doi.org/10.3390/molecules29143402.

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A new hydrazone Schiff base bridging ligand (H2LSchiff (E)-N′-((1-hydroxynaphthalen-2-yl)methylene)pyrazine-2-carbohydrazide) and L/D-proline were used to construct a pair of homochiral Dy6 cluster complexes, [Dy6(CO3)(L-Pro)6(LSchiff)4(HLSchiff)2]·5DMA·2H2O (L-1, L-HPro = L-proline; DMA = N,N-dimethylacetamide) and [Dy6(CO3)(D-Pro)6(LSchiff)4(HLSchiff)2]·5DMA·2H2O (D-1, D-HPro = D-proline), which show a novel triangular Dy6 topology. Notably, the fixation of CO2 in the air formed a carbonato central bridge, playing a key role in assembling L-1/D-1. Magnetic measurements revealed that L-1/D-1 displays intramolecular ferromagnetic coupling and magnetic relaxation behaviours. Furthermore, L-1/D-1 shows a distinct magneto-optical Faraday effect and has a second harmonic generation (SHG) response (1.0 × KDP) at room temperature. The results show that the immobilization of CO2 provides a novel pathway for homochiral multifunctional 4f cluster complexes.
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21

Nugent, William A., e Richard L. Harlow. "Early Transition Metal Alkoxide Complexes Bearing Homochiral Trialkanolamine Ligands". Journal of the American Chemical Society 116, n. 14 (luglio 1994): 6142–48. http://dx.doi.org/10.1021/ja00093a011.

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22

Fraschetti, Caterina, Marco Pierini, Claudio Villani, Francesco Gasparrini, Antonello Filippi e Maurizio Speranza. "Gas-phase structure and relative stability of proton-bound homo- and heterochiral clusters of tetra-amide macrocycles with amines". Collection of Czechoslovak Chemical Communications 74, n. 2 (2009): 275–97. http://dx.doi.org/10.1135/cccc2008155.

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The structure, stability, and CID pattern of proton-bound homochiral and heterochiral complexes, formed in the gas phase by the combination of two molecules of a chiral macrocyclic tetra-amide and an amine B, i.e. CH3NH2, (CH3)2NH, or (S)-(–)-1-phenylethylamine, have been examined by ESI-ITMS-CID mass spectrometry. With B = CH3NH2, the CID pattern is characterized by the predominant loss of B, accompanied by a much less extensive release of one tetra-amide molecule. With (S)-(–)-1-phenylethylamine, loss of a tetra-amide molecule efficiently competes with loss of B. Finally, with (CH3)2NH, loss of a tetra-amide molecule predominates over loss of B. No appreciable isotope and chiral guest configuration effects have been detected in the fragmentation of the homochiral complexes. A distinct configurational effect has been appreciated in the CID of the homo- and the heterochiral complexes with all amines used. The results of this study have been discussed in the light of semi-empirical computational evidence. The differences in the CID patterns of the homo- and the heterochiral complexes have been rationalized in terms of structural factors and of the basicity of amine B.
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23

Malinkina, O. N., e A. B. Shipovskaya. "Energy of Salt Formation and Supramolecular Ordering of Chitosan L- and D-Ascorbates". Высокомолекулярные соединения А 65, n. 5 (1 settembre 2023): 351–61. http://dx.doi.org/10.31857/s2308112023600059.

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Using two samples of chitosan (D-glucan) with viscosity-average molecular mass 40 × 103 and 200 × 103 as the example, the influence of diastereomer form (L- and D-) of ascorbic acid on the energetics of formation, structure, and supramolecular ordering of hetero- (D‒L) and homochiral (D‒D) polymer–acid salt complexes has been studied. It has been found that heat effect during the interaction of chitosan with L-ascorbic acid in aqueous medium and degree of protonation of the (D‒L)-salts are lower in comparison with D-isomer of the acid. The homochiral (D‒D)-salts, in contrast to the heterochiral (D‒L)-salts, have exhibited lower amount of crystallization water, high degree of crystallinity, and denser supramolecular structure with high level of inter- and intramolecular contacts.
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24

Brewer, Greg, Raymond J. Butcher e Peter Zavalij. "Use of Pyrazole Hydrogen Bonding in Tripodal Complexes to Form Self Assembled Homochiral Dimers". Materials 13, n. 7 (31 marzo 2020): 1595. http://dx.doi.org/10.3390/ma13071595.

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The 3:1 condensation of 5-methyl-1H-pyrazole-3-carboxaldehyde (MepyrzH) with tris(2-aminoethyl)amine (tren) gives the tripodal ligand tren(MePyrzH)3. Aerial oxidation of a solution of cobalt(II) with this ligand in the presence of base results in the isolation of the insoluble Co(tren)(MePyrz)3. This complex reacts with acids, HCl/NaClO4, NH4ClO4, NH4BF4, and NH4I to give the crystalline compounds Co(tren)(MePyrzH)3(ClO4)3, {[Co(tren)(MePyrzH0.5)3](ClO4)1.5}2 {[Co(tren)(MePyrzH0.5)3](BF4)1.5}2 and [Co(tren)(MePyrzH)3][Co(tren)(MePyrzH)3]I2. The latter three complexes are dimeric, held together by three Npyrazole –H…Npyrazolate hydrogen bonds. The structures and symmetries of these homochiral dimers or pseudodimers are discussed in terms of their space group. Possible applications of these complexes by incorporation into new materials are mentioned.
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25

Qin, Ling, Qing Hu, Yang Wu, Jia-Le Cai e Yun-Yun Li. "Three novel Co(ii)/Ni(ii)-based coordination polymers as efficient heterogeneous catalysts for dye degradation". CrystEngComm 20, n. 28 (2018): 4042–48. http://dx.doi.org/10.1039/c8ce00860d.

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Three novel Co(ii)/Ni(ii)-based coordination polymers have been synthesized and characterized. Compound 2 shows a rare 2D + 2D heterogeneous framework. Compound 3 is a chiral 0-D molecular complex driven by the solvent-assisted homochiral helix. The photocatalytic oxidation activities and mechanism have been studied.
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26

Wen, He-Rui, Xin-Rong Xie, Sui-Jun Liu, Jun Bao, Feng-Feng Wang, Cai-Ming Liu e Jin-Sheng Liao. "Homochiral luminescent lanthanide dinuclear complexes derived from a chiral carboxylate". RSC Advances 5, n. 119 (2015): 98097–104. http://dx.doi.org/10.1039/c5ra14559g.

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A family of chiral Ln2 clusters based on a chiral monocarboxylate ligand has been successfully constructed via a diffusion method, and Eu, Tb and Dy analogues display good luminescent properties.
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27

Kostyanovsky, Remir G., Konstantin A. Lyssenko e Vasily R. Kostyanovsky. "Homochiral and pseudoracemic 3,3- and 1,2-dimethyldiaziridine–silver nitrate complexes". Mendeleev Communications 10, n. 2 (gennaio 2000): 44–46. http://dx.doi.org/10.1070/mc2000v010n02abeh001261.

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28

Li, Gao, Xiaobing Xi, Weimin Xuan, Taiwei Dong e Yong Cui. "Homochiral helical coordination polymers of metallosalen complexes with tunable pitches". CrystEngComm 12, n. 8 (2010): 2424. http://dx.doi.org/10.1039/c001121e.

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29

Yin, Jun, e Ronald L. Elsenbaumer. "Syntheses of Homochiral Multinuclear Ru Complexes Based on Oligomeric Bibenzimidazoles". Inorganic Chemistry 46, n. 17 (agosto 2007): 6891–901. http://dx.doi.org/10.1021/ic062148a.

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30

Schrader, Malcolm E. "Polypeptide formation on polar mineral surfaces: possibility of complete chirality". International Journal of Astrobiology 16, n. 1 (23 novembre 2015): 10–13. http://dx.doi.org/10.1017/s1473550415000427.

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AbstractIn the present work, it is shown that thermodynamically feasible polymerization of cyanomethanol, which can be formed from formaldehyde and hydrogen cyanide, can lead to synthesis of polypeptides as well as to the previously reported synthesis of RNA. If the polymerization takes place on a one-dimensional feature of a mineral, such as for example a crack on its surface, the concept of quasi-chirality is introduced to describe the adsorbed polypeptide. This, in principle, would lead to formation of proteins that are completely homochiral in their alpha carbon groups. The concept of quasi-chirality can also be introduced in the condensation of glycine under similar conditions to form a polypeptide. This again leads to proteins completely chiral in their alpha carbon groups.
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Matveevskaya, Vladislava, Dmitry Pavlov e Andrei Potapov. "Iridium(III) and Rhodium(III) Half-Sandwich Coordination Compounds with 11H-Indeno[1,2-b]quinoxalin-11-one Oxime: A Case of Spontaneous Resolution of Rh(III) Complex". Inorganics 10, n. 11 (25 ottobre 2022): 179. http://dx.doi.org/10.3390/inorganics10110179.

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Two half-sandwich iridium(III) and rhodium(III) complexes with 11H-indeno[1,2-b]quinoxalin-11-one oxime (IQ-1) ligand were prepared by the reaction of the proligand with [M(Cp*)Cl2]2 (M = Ir, Rh) dimers. The reaction between IQ-1 and [Ir(Cp*)Cl2]2 in methanol gave the complex [Ir(Cp*)(IQ-1)Cl] (1), which crystallized in a centrosymmetric space group as a true racemate. Whereas complex [Rh(Cp*)(IQ-1)Cl] (2) in the form of a racemic conglomerate was obtained by the reaction of [Rh(Cp*)Cl2]2 and IQ-1 in methanol. The crystal structures of complexes 1 and 2 (R and S enantiomers) were determined by X-ray diffraction analysis, and the structural features were compared in order to understand the structural factors leading to the spontaneous enantiomer resolution of the rhodium(III) complex. In the crystal packing of 1, intermolecular C–H···C contacts between a pair of enantiomers link the molecules into centrosymmetric dimers and lead to the formation of heterochiral crystals of 1. In contrast, the intramolecular contacts CH···Cl and CH···C in complex 2 bind all three ligands around the chiral Rh(III) metal center. In addition, a combination of intermolecular CH···O and CH···C contacts leads to the formation of a homochiral supramolecular structure. These interactions altogether reinforce the spontaneous resolution in complex 2.
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32

Fox, Allison C., Jason D. Boettger, Eve L. Berger e Aaron S. Burton. "The Role of the CuCl Active Complex in the Stereoselectivity of the Salt-Induced Peptide Formation Reaction: Insights from Density Functional Theory Calculations". Life 13, n. 9 (23 agosto 2023): 1796. http://dx.doi.org/10.3390/life13091796.

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The salt-induced peptide formation (SIPF) reaction is a prebiotically plausible mechanism for the spontaneous polymerization of amino acids into peptides on early Earth. Experimental investigations of the SIPF reaction have found that in certain conditions, the l enantiomer is more reactive than the d enantiomer, indicating its potential role in the rise of biohomochirality. Previous work hypothesized that the distortion of the CuCl active complex toward a tetrahedral-like structure increases the central chirality on the Cu ion, which amplifies the inherent parity-violating energy differences between l- and d-amino acid enantiomers, leading to stereoselectivity. Computational evaluations of this theory have been limited to the protonated–neutral l + l forms of the CuCl active complex. Here, density functional theory methods were used to compare the energies and geometries of the homochiral (l + l and d + d) and heterochiral (l + d) CuCl–amino acid complexes for both the positive–neutral and neutral–neutral forms for alanine, valine, and proline. Significant energy differences were not observed between different chiral active complexes (i.e., d + d, l + l vs. l + d), and the distortions of active complexes between stereoselective systems and non-selective systems were not consistent, indicating that the geometry of the active complex is not the primary driver of the observed stereoselectivity of the SIPF reaction.
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33

Alcock, Nathaniel W., Graham A. Pike, Christopher J. Richards e Susan E. Thomas. "Generation of homochiral quaternary carbon centres from (vinylketenimine)tricarbonyliron(0) complexes". Tetrahedron: Asymmetry 1, n. 8 (gennaio 1990): 531–34. http://dx.doi.org/10.1016/s0957-4166(00)80542-x.

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34

Zhai, Halei, Yan Quan, Li Li, Xiang-Yang Liu, Xurong Xu e Ruikang Tang. "Spontaneously amplified homochiral organic–inorganic nano-helix complexes via self-proliferation". Nanoscale 5, n. 7 (2013): 3006. http://dx.doi.org/10.1039/c3nr33782k.

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35

Wang, Ruihu, Lijin Xu, Jianxin Ji, Qian Shi, Yueming Li, Zhongyuan Zhou, Maochun Hong e Albert S. C. Chan. "Metal-Directed Stereoselective Syntheses of Homochiral Complexes ofexo-Bidentate Binaphthol Derivatives". European Journal of Inorganic Chemistry 2005, n. 4 (febbraio 2005): 751–58. http://dx.doi.org/10.1002/ejic.200400659.

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36

Zee, Chih-Te, Calina Glynn, Marcus Gallagher-Jones, Jennifer Miao, Carlos G. Santiago, Duilio Cascio, Tamir Gonen, Michael R. Sawaya e Jose A. Rodriguez. "Homochiral and racemic MicroED structures of a peptide repeat from the ice-nucleation protein InaZ". IUCrJ 6, n. 2 (24 gennaio 2019): 197–205. http://dx.doi.org/10.1107/s2052252518017621.

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Abstract (sommario):
The ice-nucleation protein InaZ from Pseudomonas syringae contains a large number of degenerate repeats that span more than a quarter of its sequence and include the segment GSTSTA. Ab initio structures of this repeat segment, resolved to 1.1 Å by microfocus X-ray crystallography and to 0.9 Å by the cryo-EM method MicroED, were determined from both racemic and homochiral crystals. The benefits of racemic protein crystals for structure determination by MicroED were evaluated and it was confirmed that the phase restriction introduced by crystal centrosymmetry increases the number of successful trials during the ab initio phasing of the electron diffraction data. Both homochiral and racemic GSTSTA form amyloid-like protofibrils with labile, corrugated antiparallel β-sheets that mate face to back. The racemic GSTSTA protofibril represents a new class of amyloid assembly in which all-left-handed sheets mate with their all-right-handed counterparts. This determination of racemic amyloid assemblies by MicroED reveals complex amyloid architectures and illustrates the racemic advantage in macromolecular crystallography, now with submicrometre-sized crystals.
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37

Očić, Marko, e Lidija Androš Dubraja. "Intermolecular Interactions in Molecular Ferroelectric Zinc Complexes of Cinchonine". Crystals 14, n. 11 (13 novembre 2024): 978. http://dx.doi.org/10.3390/cryst14110978.

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Abstract (sommario):
The use of chiral organic ligands as linkers and metal ion nodes with specific coordination geometry is an effective strategy for creating homochiral structures with potential ferroelectric properties. Natural Cinchona alkaloids, e.g., quinine and cinchonine, as compounds with a polar quinuclidine fragment and aromatic quinoline ring, are suitable candidates for the construction of molecular ferroelectrics. In this work, the compounds [CnZnCl3]·MeOH and [CnZnBr3]·MeOH, which crystallize in the ferroelectric polar space group P21, were prepared by reacting the cinchoninium cation (Cn) with zinc(II) chloride or zinc(II) bromide. The structure of [CnZnBr3]·MeOH was determined from single-crystal X-ray diffraction analysis and was isostructural with the previously reported chloride analog [CnZnCl3]·MeOH. The compounds were characterized by infrared spectroscopy, and their thermal stability was determined by thermogravimetric analysis and temperature-modulated powder X-ray diffraction experiments. The intermolecular interactions of the different cinchoninium halogenometalate complexes were evaluated and compared.
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38

Setsune, Jun-ichiro, Miku Kawama e Takeshi Nishinaka. "Helical binuclear CoII complexes of pyriporphyrin analogue for sensing homochiral carboxylic acids". Tetrahedron Letters 52, n. 15 (aprile 2011): 1773–77. http://dx.doi.org/10.1016/j.tetlet.2011.02.013.

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39

Zheng, Xiao-Dan, Yan-Long Hua, Ren-Gen Xiong, Jia-Zhen Ge e Tong-Bu Lu. "Cyano-Bridged Homochiral Heterometallic Helical Complexes: Synthesis, Structures, Magnetic and Dielectric Properties". Crystal Growth & Design 11, n. 1 (5 gennaio 2011): 302–10. http://dx.doi.org/10.1021/cg101314j.

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40

Uozumi, Yasuhiro. "Heterogeneous Asymmetric Catalysis in Water with Amphiphilic Polymer-Supported Homochiral Palladium Complexes". Bulletin of the Chemical Society of Japan 81, n. 10 (15 ottobre 2008): 1183–95. http://dx.doi.org/10.1246/bcsj.81.1183.

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41

Ren, Dong-Hong, Xiao-Li Sun, Ling Gu, Dan Qiu, Zaijun Li e Zhi-Guo Gu. "A family of homochiral spin-crossover iron(II) imidazole Schiff-base complexes". Inorganic Chemistry Communications 51 (gennaio 2015): 50–54. http://dx.doi.org/10.1016/j.inoche.2014.11.006.

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42

Uozumi, Yasuhiro. "Asymmetric allylic substitution of cycloalkenyl esters in water with an amphiphilic resin-supported chiral palladium complex". Pure and Applied Chemistry 79, n. 9 (1 gennaio 2007): 1481–89. http://dx.doi.org/10.1351/pac200779091481.

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Abstract (sommario):
A novel homochiral phosphine ligand, (3R,9aS)[2-aryl-3-(2-diphenylphosphino)phenyl]tetrahydro-1H-imidazo[1,5-a]indole-1-one, was designed, prepared, and anchored onto an amphiphilic polystyrene-poly(ethylene glycol) copolymer (PS-PEG) resin. Catalytic asymmetric substitution of a racemic mixture of cycloalkenyl esters with carbon, nitrogen, and oxygen nucleophiles was achieved in water as the single reaction medium under heterogeneous conditions by using the PS-PEG resin-supported palladium-imidazoindole phosphine complex to give optically active substituted cycloalkenes with up to 99 % ee.
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43

Wölper, Christoph, Sara Durán Ibáńez e Peter G. Jones. "Amine-rich Silver Complexes of rac-trans-1,2-Diaminocyclohexane". Zeitschrift für Naturforschung B 65, n. 10 (1 ottobre 2010): 1249–57. http://dx.doi.org/10.1515/znb-2010-1012.

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The use of the diamine rac-trans-1,2-diaminocyclohexane (LL) as a major component of the solvent system allows the isolation of crystalline silver complexes with higher ratios of LL to silver (up to 4 : 1, compared to the previously obtained 1 : 1 in ethanolic solution). The complexes obtained and crystallographically characterized were (LL)2AgNO3 (1), (LL)3Ag(OAc)(H2O)2 (2) and (LL)4AgBr(H2O)3 (3). Additionally, the silver-free compounds (LL)・(H2O) (4) and (LL)3・HCl (5) were obtained as by-products. Complex 1 is a chain polymer with one bridging and one terminal LL ligand; the chains are homochiral. Complex 2 contains isolated [(LL)3Ag]+ cations with one chelating and two monodentate ligands. Complex 3 contains dimeric [(LL)2AgBr]2 units; the additional LL molecules are not coordinated to the metal. Compound 5 consists of one diamine with imposed twofold symmetry, one half-protonated diamine in which the acidic hydrogen site is half-occupied (it is involved in a disordered hydrogen bond N-H・ ・ ・N across a twofold axis) and a chloride anion on a twofold axis. In all five structures, the components pack so as to form clearly defined hydrophilic and hydrophobic areas. In the former, classical hydrogen bonds are formed. Except for a few borderline cases of three-center bonds, these are all two-center systems. The appreciable number of these (e. g. 20 for compound 3) renders the layer structures quite complex, but in most cases they can be analyzed in terms of smaller units.
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44

Kühne, Irina A., Andrew Ozarowski, Aizuddin Sultan, Kane Esien, Anthony B. Carter, Paul Wix, Aoife Casey et al. "Homochiral Mn3+ Spin-Crossover Complexes: A Structural and Spectroscopic Study". Inorganic Chemistry 61, n. 8 (17 febbraio 2022): 3458–71. http://dx.doi.org/10.1021/acs.inorgchem.1c03379.

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45

Wang, Yong-Tao, Gui-Mei Tang, Wen-Zhu Wan, Yue Wu, Ting-Cui Tian, Jin-Hua Wang, Chao He, Xi-Fa Long, Jun-Jie Wang e Seik Weng Ng. "New homochiral ferroelectric supramolecular networks of complexes constructed by chiral S-naproxen ligand". CrystEngComm 14, n. 10 (2012): 3802. http://dx.doi.org/10.1039/c2ce25138h.

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46

Howell, James A. S., Andrew G. Bell, Paula J. O'Leary, Patrick McArdle, Desmond Cunningham, G. Richard Stephenson e Michelle Hastings. "Access to Homochiral Acyclic (diene)Fe(CO)3 Complexes Containing Electron Donor Substituents". Organometallics 13, n. 5 (maggio 1994): 1806–12. http://dx.doi.org/10.1021/om00017a043.

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47

Lamberts, Kevin, Mihaela-Diana Şerb e Ulli Englert. "Unexpected proline coordination in the copper chain polymer [Cu(μ-Cl)2(μ-DL-proline-κ2O:O′)]1∞". Acta Crystallographica Section C Structural Chemistry 71, n. 4 (10 marzo 2015): 271–75. http://dx.doi.org/10.1107/s205322961500426x.

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Abstract (sommario):
Incatena-poly[copper(II)-di-μ-chlorido-μ-proline-κ2O:O′], [CuCl2(C5H9NO2)]n, two symmetry-independent metal cations adopt distorted octahedral coordination, typical ford9Jahn–Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a CuIIcentre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter (i.e. a). TheO:O′-bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for CuII; the vast majority of amino acid derivatives of this cation are characterized byN,O-chelation.
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48

Boer, Stephanie A., e David R. Turner. "Self-selecting homochiral quadruple-stranded helicates and control of supramolecular chirality". Chemical Communications 51, n. 98 (2015): 17375–78. http://dx.doi.org/10.1039/c5cc07422c.

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49

Bianchet, Stephen, e Pierre G. Potvin. "The solution structures of chiral Ti4+ alkoxides. II. The roles of diolate basicity and side-chain binding group polarity". Canadian Journal of Chemistry 70, n. 8 (1 agosto 1992): 2256–65. http://dx.doi.org/10.1139/v92-284.

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Abstract (sommario):
With a view to reproduce the structure in solution of the Katsuki–Sharpless catalyst (the dimeric complex formed by homochiral diisopropyl tartrate with Ti(OiPr)4), five C2-symmetric chiral 2,3-butanediols, related to L-threitol but bearing N-, S-, and P-containing groups at the 1- and 4-positions, were prepared and their reactions with Ti(OiPr)4 were examined by nuclear magnetic resonance spectroscopy. The 1,4-dithioether formed a non-fluxional 2:2 tricyclic complex entirely analogous to those formed by alkylated sugar derivatives. The related disulfone formed a similar complex, but only at low temperatures, probably because of oligomerization at higher temperatures. A symmetric 2:1 complex also formed with excess Ti(OiPr)4, but incompletely and in equilibrium with the 2:2 species. No well-defined complexes were formed with pyrazole or phosphine oxide functionalities. However, in the presence of trifluoroacetic acid (TFA), a 1:2:2 L:Ti:TFA complex was identified with the dimethylpyrazole-containing diol and this resembled the 2:3 complexes formed by tartramides. Generally, the degree of spectral asymmetry and the coupling constant between diolate protons were instrumental in assigning structures and were used to classify all chiral diolate complexes into two groups according to whether or not they exhibited metal chelation and diolate bridging. By comparison of the effects of complexation on the diolate nuclei, a correlation was found between 13C and 1H nmr signal positions and between the pairs of signals in the spectra of asymmetric complexes, except in four cases where metal-bound side-chain groups induced a shielding of the bridging diolate proton. This could serve as an additional indication of metal chelation and diolate bridging and confirmed that nuclei at bridging positions appeared upfield of terminal ones. Noting that all the diols that readily chelated and bridged possessed electron-releasing side chains, while tartrates and tartramides that did not chelate possessed electron-withdrawing side chains, the basicity of the diolate oxygens is considered the most important determinant of structure. Side-chain polarity was instead found to influence whether or not a well-defined complex could form.
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50

Alam, Mohammad Sahabul, Andreas Scheurer, Rolf W. Saalfrank e Paul Müller. "STM Analysis of a Chiral Helical Onedimensional Nickel(II) Coordination Polymer". Zeitschrift für Naturforschung B 63, n. 12 (1 dicembre 2008): 1443–46. http://dx.doi.org/10.1515/znb-2008-1218.

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C2-symmetric nickel(II) salen complexes [NiL] 1 were deposited on a highly oriented pyrolytic graphite (HOPG) surface from their acetone solutions. They aggregate easily to single, segregated, homochiral polymeric chains of (M)-1D- 1n [NiL] (2) on the substrate as also found in single crystals. In STM topography, the single helical 1D structures 2 found on the surface were in excellent agreement with the dimension of aligned dimeric aggregates of 1 obtained from X-ray crystallography. Weak intermolecular NiII...OMe coordinations (dMeO−Ni = 0.35 nm) were found to be responsible for the formation of the chiral, helical and 1D assemblies on the substrate.
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