Academic literature on the topic 'Fluorine-substituted ligand'

Electron ionization positive ion mass spectra of 15 substituted cobalt(III) β-diketonates and monothio-β-diketonates, CoIIIL3, where L = RCXCHCOR′, R = phenyl, 2-thienyl, or 2-naphthyl; X = O or S; and R′ = CHF2, CF3, C2F5, or n-C3F7, show a marked dependence on the ligand. Molecular ions, [CoIIIL3]+•, are observed only for some of the more highly fluorinated complexes (R′ = C2F5 or n-C3F7). The [CoIIIL2]+• ion, possibly generated by ionization of CoIIL2 formed by thermal degradation, or by electron ionization of CoIIIL3, typically decomposes by elimination of a radical, i.e., L• or R′•, to yield ions containing Co(II); subsequent decompositions proceed preferentially by loss of even-electron neutral species, also to yield ions containing Co(II). Cobalt-containing ions in which fluorine has rearranged to the metal decrease in variety and abundance for the ligands with higher fluorine content. When metal-bonded oxygen is replaced by sulfur, fluorine migration to Co(III), rather than to Co(II), is preferred. These trends are consistent with a combination of several different concepts including the ability of the metal to undergo valency change, the principle of Hard and Soft Acids and Bases, and the inductive capabilities of the ligand donor atoms and of the R and R′ groups. Ion decomposition pathways are proposed. Keywords: mass spectrometry, cobalt complexes, β-diketonates, fluorinated chelate complexes.

Abstract Mössbauer investigations, in association with density functional theory (DFT) calculations, have been conducted for the molecular and electronic structures of iron (III) [tetrakis (pentafluorophenyl)] porphyrin chloride [(F20TPP)Fe:Cl], as a Fe(III)-tetraphenylporphyrin complex containing chloride axial ligand and substituted hydrogen atoms by fluorine ones in the four phenyl rings, in comparison with its fluorine unsubstituted analogue [(TPP)Fe:Cl]. It was found that the parameters of Mössbauer spectra of both complexes are close to one another, and correspond to the high-spin state of Fe(III) ions, but they show the different temperature dependence and the quadrupole doublets in Mössbauer spectra show different asymmetry at low temperatures. Results of DFT calculations are analyzed in the light of catalytic activity of the halogenated complex.

In order to synthesize new iron (II) complexes of 1,5-diaza-3,7-diphosphacyclooctanes with a wider variety of the substituents on ligands heteroatoms (including functionalized ones, namely, pyridyl groups) and co-ligands, it was found that these ligands with relatively small phenyl, benzyl, and pyridin-2-yl substituents on phosphorus atoms in acetonitrile formed bis-P,P-chelate cis-complexes [L2Fe(CH3CN)2]2+ (BF4)2−, whereas P-mesityl-substituted ligand formed only monoligand P,P-complex [LFe(CH3CN)4]2+ (BF4)2−. 3,7-dibenzyl-1,5-di(1′-(R)-phenylethyl)-1,5-diaza-3,7-diphosphacyclooctane reacted with hexahydrate of iron (II) tetrafluoroborate in acetone to give an unusual bis-ligand cationic complex of the composition [L2Fe(BF4)]+ BF4−, where two fluorine atoms of the tetrafluoroborate unit occupied two pseudo-equatorial positions at roughly octahedral iron ion, according to X-ray diffraction data. 1,5-diaza-3,7-diphosphacyclooctanes replaced tetrahydrofurane and one of the carbonyl ligands of cyclopentadienyldicarbonyl(tetrahydrofuran)iron (II) tetrafluoroborate to form heteroligand complexes [CpFeL(CO)]+BF4−. The structural studies in the solid phase and in solutions showed that diazadiphosphacyclooctane ligands of all complexes adopted chair-boat conformations so that their nitrogen atoms were in close proximity to the central iron ion. The redox properties of the obtained complexes were performed by the cyclic voltammetry method.

A new series of twenty-two C-5 substituted N-arylsulfonylindoles was prepared with the aim of exploring the influence of C-5 substitution on 5-HT6 receptor affinity. Eleven compounds showed moderate to high affinity at the receptor (Ki = 58–403 nM), with compound 4d being identified as the most potent ligand. However, regarding C-5 substitution, both methoxy and fluorine were detrimental for receptor affinity compared to our previously published unsubstituted compounds. In order to shed light on these observations, we performed docking and molecular dynamics simulations with the most potent compounds of each series (4d and 4l) and PUC-10, a highly active ligand previously reported by our group. The comparison brings about deeper insight about the influence of the C-5 substitution on the binding mode of the ligands, suggesting that these replacements are detrimental to the affinity due to precluding a ligand from reaching deeper inside the binding site. Additionally, CoMFA/CoMSIA studies were performed to systematize the information of the main structural and physicochemical characteristics of the ligands, which are responsible for their biological activity. The CoMFA and CoMSIA models presented high values of q2 (0.653; 0.692) and r2 (0.879; 0.970), respectively. Although the biological activity of the ligands can be explained in terms of the steric and electronic properties, it depends mainly on the electronic nature.

At the molecular level, the enantiomerically pure square-planar organoplatinum complex (SP-4-4)-(R)-[2-(1-aminoethyl)-5-fluorophenyl-κ2C1,N][(R)-1-(4-fluorophenyl)ethylamine-κN](isocyanato-κN)platinum(II), [Pt(C8H9FN)(NCO)(C8H10FN)], and its congener without fluorine substituents on the aryl rings adopt the same structure within error. The similarities between the compounds extend to the most relevant intermolecular interactions,i.e.N—H...O and N—H...N hydrogen bonds link neighbouring molecules into chains along the shortest lattice parameter in each structure. Differences between the crystal structures of the fluoro-substituted and parent complex become obvious with respect to secondary interactions perpendicular to the classical hydrogen bonds; the fluorinated compound features short C—H...F contacts with an F...H distance ofca2.6 Å. The fluorine substitution is also reflected in reduced backbonding from the metal cation to the isocyanate ligand.

The structure-thermodynamics correlation analysis was performed for a series of fluorine- and chlorine-substituted benzenesulfonamide inhibitors binding to several human carbonic anhydrase (CA) isoforms. The total of 24 crystal structures of 16 inhibitors bound to isoforms CA I, CA II, CA XII, and CA XIII provided the structural information of selective recognition between a compound and CA isoform. The binding thermodynamics of all structures was determined by the analysis of binding-linked protonation events, yielding the intrinsic parameters, i.e., the enthalpy, entropy, and Gibbs energy of binding. Inhibitor binding was compared within structurally similar pairs that differ bypara-ormeta-substituents enabling to obtain the contributing energies of ligand fragments. The pairs were divided into two groups. First,similarbinders—the pairs that keep the same orientation of the benzene ring exhibited classical hydrophobic effect, a less exothermic enthalpy and a more favorable entropy upon addition of the hydrophobic fragments. Second,dissimilarbinders—the pairs of binders that demonstrated altered positions of the benzene rings exhibited the non-classical hydrophobic effect, a more favorable enthalpy and variable entropy contribution. A deeper understanding of the energies contributing to the protein-ligand recognition should lead toward the eventual goal of rational drug design where chemical structures of ligands could be designed based on the target protein structure.

Coordination complexes, [Co2(1)4(H2O)2] (2), [Ni2(1)4(H2O)2] (3), and [Cu(1)2] (4), by using an asymmetric and partially fluorinated 3-hydroxy-3-pentafluorophenyl-1-phenyl-2-propen-1-one (H1) have been prepared, and the structures were investigated to compare with the corresponding fully fluorinated complexes of [Co2(5)4(H2O)2] (6), [Ni2(5)4(H2O)2] (7), and [Cu(5)2] (8) with bis(pentafluorobenzoyl)methane (H5) and to understand the fluorine-substituted effects. While the coordination mode of the partially fluorinated complexes was quite similar to the fully fluorinated complexes, the intra- and intermolecular π-interactions of the ligand moieties were highly influenced by the fluorination effects; the arene-perfluoroarene interactions were observed in complexes 2 and 3 as a reason of the dinucleation. In this paper, we describe detail structures of the protonated form of the ligand, H1, and complexes 2–4 by X-ray crystallographic studies.

The second-order non-linear optical (NLO) response of organoimido-substituted hexamolybdates has been tuned from 218.61 × 10–30 to 490.10 × 10–30 esu. The dipole polarizabilities and second-order nonlinear optical (NLO) properties of organoimido derivatives of hexamolybdates have been investigated by using the time-dependent density functional response theory (TDDFT). The electron withdrawing ability of F (fluorine) has played an important role in tuning the second-order NLO response in this class of organic-inorganic hybrid compounds; particularly system 6 [Mo6O18(NC16H8F2(CF3)2I)]2– with the static second-order polarizability (βvec ) computed to be 490.10 × 10–30 esu. Thus, our studied systems have the feasibility to be excellent tuneable second-order NLO materials. The analysis of the major contributions to the βvec value suggests that the charge transfer (CT) from POM to organic ligand (D-A) along the z-axis has been enhanced with addition of F atoms at the end phenyl ring which directs head (POM) to tail (fluorinated ring) charge transfer. The computed βvec values have been tuned by incorporation of different halogen atoms at the end phenyl ring of organoimido segment. Furthermore, substitution of two trifluoromethyl (–CF3) groups sideways along with iodine (I) at the terminus of end phenyl ring in the organoimido ligand has a striking influence on tuning the optical non-linearity, as CT from POM to the organoimido ligand was significantly increased. These systematic small changes in molecular composition by substitution of different halogen groups leads to a tuning the NLO response; the so-called ‘ripple effect’ catches this point nicely. Thus, the present investigation provides thought provoking insight into the tuneable NLO properties of organoimido-substituted hexamolybdates.

The dinuclear cyclometallated gold(I) complex [Au2(μ-2-C6F4PPh2)2] was prepared in high yield from the reaction of 2-LiC6F4PPh2 with either [AuBr(AsPh3)] or [AuCl(tht)], and from the reaction of 2-Me3SnC6F4PPh2 with [AuCl(tht)]. The digold(I) complex undergoes oxidative addition reactions with halogens to give the metal-metal bonded dihalodigold(II) complexes [Au2IIX2(μ-2-C6F4PPh2)2] (X = Cl, Br, I), which on warming or exposure to light, isomerise to give the heterovalent gold(I)-gold(III) species [XAu(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuX] containing a four-membered cyclometallated ring on a gold(III) centre. Unlike its protio analogue, [Au2(μ-2-C6F4PPh2)2] did not undergo oxidative addition of methyl iodide or dibenzoyl peroxide. The dihalodigold(II) [Au2IIX2(μ-2-C6F4PPh2)2] and gold(I)-gold(III) compounds [XAu(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuX] (X = Cl, Br) are further oxidised by halogens to give the digold(III) species [Au2X4(μ-2-C6F4PPh2)2] and [X3Au(μ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuX], respectively. The complexes [Au2X4(μ-2-C6F4PPh2)2] are reduced to the dihalodigold(II) complexes in the presence of one equivalent of zinc powder; further addition of zinc gave the parent digold(I) dimer. Treatment of [Au2IICl2(μ-2-C6F4PPh2)2] and [ClAu(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuCl] with an excess of silver nitrate, benzoate, acetate, trifluoroacetate or triflate gave the corresponding oxyanion complexes. Slow crystallisation of the di(benzoato)digold(II) complex from dichloromethane and methanol gave the parent digold(I) complex derived by reductive elimination. The di(triflato)digold(II) complex behaved similarly, although in this case the novel gold(I) tetramer [Au4(μ-2-C6F4PPh2)4] was formed together with the dimer. Two closely related gold complexes containing the chelating κ2(C,O) phosphine oxide ligand, 2-C6F4P(O)PPh2, were isolated from the reaction of [ClAu(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuCl] with an excess of silver nitrate. The reaction of [Au2IICl2(μ-2-C6F4PPh2)2] with two equivalents of potassium trifluoroethoxide failed to give the corresponding digold(II) bis(alkoxo) complex; instead, reduction took place to form the digold(I) dimer [Au2(μ-2-C6F4PPh2)2]. Treatment of a solution of the di(benzoato)digold(II) complex with C6F5Li gave the pentafluorophenyl complex [Au2(C6F5)2(μ-2-C6F4PPh2)2] which, when heated in toluene, rearranged to the gold(I)-gold(III) complex [(C6F5)Au(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)Au(C6F5)], analogous to the behaviour of the dihalodigold(II) complexes. The heterovalent, gold(I)-gold(III) dimethyl compound [Au2I,III(CH3)2(μ-2-C6F4PPh2)2] was obtained from the reaction of the di(benzoato)digold(II) complex with dimethylzinc. This compound is structurally similar to its tetraprotio analogue. The cycloaurated dinuclear gold complexes [Au2(μ-C6H3-n-F-2-PPh2)2] (n = 5, 6) were made similarly to the 2-C6F4PPh2 analogue from the appropriate lithium or tin reagents, though in some cases the dimers were formed in admixture with the corresponding gold(I) tetramers. Like their tetrafluoro analogues, the 6-fluoro complexes [Au2X2(μ-C6H3-6-F-2-PPh2)2] (X = Cl, Br, I) rearrange on heating to give the heterovalent gold(I)-gold(III) species [XAu(µ-C6H3-6-F-2-PPh2)(κ2-C6H3-6-F-2-PPh2)AuX]. Thus, the presence of a fluorine atom in place of hydrogen in the 6-position of the bridging aryl group is sufficient to stop the isomerisation of the digold(II) complexes [Au2X2(μ-2-C6H4PPh2)2] at the gold(I)-gold(III) stage and to prevent subsequent C-C coupling of the aryl groups at the gold(III) centre. In contrast, the dihalodigold(II) complexes containing the 5-fluoro substituted ligand undergo reductive elimination and coupling of the metallated aryl groups to give the digold(I) biphenyldiyl complexes [Au2X2(2,2'-Ph2P-5-FC6H3C6H3-5-F-PPh2)] (X = Cl, Br, I). The described complexes were characterised using 1H NMR, 31P NMR, 19F NMR spectroscopy, elemental analysis, mass spectroscopy, IR spectroscopy, X-ray diffraction and 197Au Mössbauer spectroscopy.