A new amino alcohol NpyNimineNamineOalcohol-donor ligand: coordination toward zinc(II) and cadmium(II) halides and enantioselective products

In the present work a new ligand, 2-(2-(phenyl(pyridin-2-yl)methyleneamino)ethylamino)ethanol (L), and its Zn(II) and Cd(II) complexes, [Zn(L)Br₂] (1), [Cd(L)Br₂] (2) and [Cd(L)I₂] (3), have been synthesized and characterized by elemental analysis, FT-IR, Raman and ¹H NMR spectroscopies as well as X-ray crystallography. All complexes are isostructural and their metal ions have distorted square pyramidal geometry with an MN₃X₂ (X: Br, I) environment. During the complexation process, the amine group of the ligand becomes a chiral center. In the solid-state, an R-configuration was observed in all three complexes. Furthermore, the molecules form intermolecular C–H?O, C–H?X and O–H?X (X: Br, I) hydrogen bonds in the solid-state.     

Synthesis,spectral and antimicrobial studies of chlorodiorganotin(IV)[3(2′-hydroxyphenyl)-5-(4-substitutedphenyl) pyrazolinates]

Chlorodiorganotin(IV)pyrazolinates of the type R₂SnCl(C₁₅H₁₂N₂O?·?X) [where C₁₅H₁₂N₂O?·?X?=?3(2′-Hydroxyphenyl)-5(4-X-phenyl)pyrazoline {where X?=?H (a); CH₃ (b); OCH₃ (c); Cl (d) and R?=?Me, Pr ⁿ and Ph}] have been synthesized by reaction of R₂SnCl₂ with the sodium salt of pyrazolines in 1?:?1 molar ratio, in anhydrous benzene. These newly synthesized derivatives have been characterized by elemental analysis (C, H, N, Cl and Sn), molecular weight measurement and spectral studies [IR and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn)]. The bidentate behavior of the ligands was confirmed by IR, ¹H and ¹³C NMR spectral data. Trigonal bipyramidal structure around tin(IV) for R₂SnCl(C₁₅H₁₂N₂O?·?X) is suggested. The free pyrazoline and some chlorodiorganotin(IV) pyrazolinates have been screened for their antibacterial and antifungal activities. Some chlorodiorganotin(IV) pyrazolinates exhibit higher antibacterial and antifungal effect than free pyrazoline and some antibiotics.     

Effects of electron-rich ancillary ligands on green and yellow-emitting bis-cyclometalated iridium complexes

Abstract

Six new green to yellow-emitting heteroleptic bis-cyclometalated iridium(III) complexes of the type Ir(C?N)₂(L?X) (C?N?=?cyclometalating ligand, L?X?=?monoanionic chelating ancillary ligand) bearing two widely used cyclometalating ligands (C?N?=?2-(2-thienyl)pyridine (thpy) and 2-phenylbenzoxazole (bo)) and six different ancillary ligands were prepared. In this study, the complexes include structurally diverse ancillary ligands that allow us to investigate several aspects of structure-property relationships. Ancillary ligands used in this study are small-bite-angle N-phenylacetamidate (paa), N-isopropylbenzamidate (ipba) and N,N′-diisopropylbenzamidinate (dipba), and larger bite-angle β-ketoiminate (acNac), β-diketiminate (NacNac), and β-thioketoiminate (SacNac). The emission color is governed by the choice of the cyclometalating ligand, but the ancillary ligands influence the electrochemical and photophysical properties. Electrochemical analysis shows that the energy of the HOMO varies substantially as the L?X structure is altered, whereas the energy of LUMO remains nearly constant. The emission maxima range from 537?nm to 590?nm, with solution quantum yields between 0.0094 and 0.60 and microsecond lifetimes. The results here reveal the ancillary ligands provide a channel to control redox properties and excited-state dynamics in cyclometalated iridium complexes that luminesce in the middle regions of the visible spectrum.     

Supramolecular Self Assembly of [Cu(CN)4]3− Ions with Cationic {Ph3Sn+} Units in the Presence of Neutral Bidentate Ligands

The supramolecular interplay of the Ph ₃ Sn⁺ unit and the [Cu(CN) ₄ ]^3? ion with either 4,4′-bipyridine (bpy), trans-1,2-bis(4-pyridyl)ethene (tbpe), 1,2-bis(4-pyridyl)ethane (bpe), pyrazine (pyz), or methylpyrazine (mepyz) as bidentate ligands in presence of H ₂ O has been investigated for the first time. The products obtained have the general formula [(Ph ₃ Sn) ₃ Cu(CN)₄·L·XH₂O], where L is a bidentate ligand and X = 0–2. H ₂ O molecules are usually coordinated to tin atoms and are involved in two significant O─H─N hydrogen bonds, wherein the nitrogen atoms belong either to the bidentate ligand or the M-coordinated cyanide ligands. The structures of these supramolecular coordination polymers were investigated by elemental analysis, X-ray powder diffraction, and IR, mass, and NMR spectra.     

Synthesis,spectral and antimicrobial studies of triorganotin(IV) 3(2′-hydroxyphenyl)-5-(4-substituted phenyl) pyrazolinates

Triorganotin(IV) pyrazolinates of the type R₃Sn(C1₅H₁₂N₂O?·?X) [where C₁₅H₁₂N₂O?·?X?= 3(2′-hydroxyphenyl)-5(4-X-phenyl)pyrazoline {where X?=?H (a); CH₃ (b); OCH₃ (c); Cl (d) and R?=?Me, Pr ⁿ and Ph}] have been synthesized by the reaction of R₃SnCl with the sodium salt of pyrazolines in a 1?:?1 molar ratio, in anhydrous benzene. These newly synthesized derivatives have been characterized by elemental analysis (C, H, N, Cl and Sn), molecular weight measurement as well as spectral studies [IR and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn)]. The bidentate behaviour of the ligands was confirmed by IR, ¹H and ¹³C NMR spectral data. Trigonal bipyramidal structure around tin(IV) atom for R₃Sn(C₁₅H₁₂N₂O?·?X) has been suggested. The free pyrazoline and a few triorganotin(IV) pyrazolinates have also been screened for their antibacterial and antifungal activities. Some triorganotin(IV) pyrazolinates exhibit higher antibacterial and antifungal effects than free pyrazoline and some of the antibiotics.     

Strukturuntersuchungen an Derivaten des Nickelkomplexes Ni(ONO) (ONO2− = Dianion einer dreizähnigen Schiffschen Base)

Structure Studies on Derivatives of the Nickel Complex Ni(ONO) (ONO^2? = Dianion of a Tridentate Schiff Base) The thermodynamically stable form of the solvent free, formally tri-coordinate complex Ni(ONO) (ONO^2? = dianion of N-(2-hydroxyphenyl)-2-ethoxycarbonyl-3-ox(o-butene(1) amine(1)) as well as the mono adducts Ni(ONO)X with X = ammonia and X = diphenyl thiourea (DPT) have been characterized by X-ray structure analysis. In all cases the central atom is coordinated in a square-planar fashion, only for the adduct Ni(ONO)(DPT) a pyramidal distortion is observed which is due to the formation of hydrogen bonds. The solvent free form is a dimer [Ni(ONO)]₂, and represents one of the few examples of dinuclear nickel complexes with a planar [NO₃] coordination. The phenolic O-atoms act as bridging ligands. Due to their reduced π-donor strength the bond lengths Ni? O trans to the bridges are significantly shortened. In contrast to the analogous complex with an aliphatic bridge, “NiEIA”, both halves of the dimeric molecules are coplanar with a Ni? Ni distance of 3.29 Å.     

Chromotropism studies on copper(II) compounds. Part II. Dinuclear copper(II) complexes with triply-bridged hydroxo,acetate, and halo ligands

Abstract

Two triply-bridged dinuclear copper(II) complexes of formula [LCu(μ-OH)(μ-OAc)(μ-X)CuL]X?0.5H₂O where L is a bidentate ligand of N-(pyridine-2-ylmethyl)propane-2-amine and X=Cl, 1 and Br, 2 were synthesized and characterized by elemental analyses, spectroscopic techniques (IR, UV–Vis, EPR), thermal analysis, conductance measurements, and single-crystal X-ray structure determination. The structures of both complexes are similar. The complexes show a distorted square-pyramidal arrangement around each copper(II) ion with a CuN₂O₂X chromophore in which both copper(II) ions are connected by a hydroxo bridge and a triatomic syn-syn carboxylato bridge in equatorial positions and a halide ion bridge at the axial site. The chromotropism behavior of the complexes, including solvato-, thermo-, and halochromism, were investigated in detail. Their halochromism was investigated in the pH range of 2.0–11.0 by visible absorption spectroscopy. The reversible color variations from blue to colorless are attributable to deprotonation and protonation of the ligands. The complexes show reversible thermochromism in solution due to dissociation and recombination of ligands to copper ions.     

Influence of supporting ligand microenvironment on the aqueous stability and visible light-induced CO-release reactivity of zinc flavonolato species

The visible light-induced CO-release reactivity of the zinc flavonolato complex [(6-Ph₂TPA)Zn(3-Hfl)]ClO₄ (1) has been investigated in 1?:?1 H₂O?:?DMSO. Additionally, the effect of ligand secondary microenvironment on the aqueous stability and visible light-induced CO-release reactivity of zinc flavonolato species has been evaluated through the preparation, characterization, and examination of the photochemistry of compounds supported by chelate ligands with differing secondary appendages, [(TPA)Zn(3-Hfl)]ClO₄ (3; TPA = tris-2-(pyridylmethyl)amine) and [(bnpapa)Zn(3-Hfl)]ClO₄ (4; bnpapa = N,N-bis((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine)). Compound 3 undergoes reaction in 1?:?1 H₂O?:?DMSO resulting in the release of the free neutral flavonol. Irradiation of acetonitrile solutions of 3 and 4 at 419 nm under aerobic conditions results in quantitative, photoinduced CO-release. However, the reaction quantum yields under these conditions are lower than that exhibited by 1, with 4 exhibiting an especially low quantum yield. Overall, the results of this study indicate that positioning a zinc flavonolato moiety within a hydrophobic microenvironment is an important design strategy toward further developing such compounds as CO-release agents for use in biological systems.     

Lead(II) coordination frameworks with 3-fluorophthalic acid: hydrothermal synthesis,crystal structure,and luminescence

Hydrothermal reactions of Pb(NO₃)₂ and 3-fluorophthalic acid (H₂Fpht) in the absence or presence of 2,2′-bipyridine (bpy) gave two coordination polymers: Pb₅(Fpht)₄(Fba)₂ (1) and [Pb₂(Fpht)₂(bpy)(H₂O)]·3H₂O (2). The 3-fluorobenzoic acid (HFba) results from an in situ decarboxylation of H₂Fpht. Solid 1 displays a 2-D structure, comprising center-related hexanuclear [Pb₃(COO)₆]₂ units. There are three crystallographically different Pb(II) ions and two different ligands, Fpht and Fba. The Fpht ligands adopt μ_6?:?η⁵η³ and μ_6?:?η³η⁴ unusual bridging coordination modes. A 3-D supramolecular architecture is formed via C–H?F hydrogen bonds. Solid 2 possesses a 1-D chain structure, comprising center-related tetranuclear [Pb₂(COO)₄]₂ units. There are two crystallographically different Pb(II) ions. The Fpht ligands adopt μ_3?:?η²η³ and μ_4?:?η³η³ bridging coordination. The free water molecules form (H₂O)₃ clusters to link the 1-D chain by hydrogen bonds. A 3-D supramolecular assembly is constructed via hydrogen bonds between the free water and the F of Fpht ligands. Fluorescence of the complexes originates from π*–π transitions of the ligands.     

INORGANIC RINGS WITH GALLIUM ORGANYLS AND IMINODIPHOSPHINECHALCHOGENIDES

The organometallic complexes of general formula [Me ₂ Ga{(XPR ₂ ) (YPR′ ₂ )N}] (R, R′ = Ph, X, Y = O, (1); R, R′ = Ph, X, Y = S (2); R, R′ = Ph, X = O, Y = S (3); R = Me, R′ = Ph, X = O, Y = S (4)) were obtained by alkane eliminations from Me ₃ Ga and the free acidic ligands, LH, in toluene solutions. Complexes 1– 4 seem to be potential precursors to cationic gallium species.     

Synthesis and Complexing Properties of Phosphorus-Substituted Pyridine-2-Carboxylic Acid Anilides

Abstract

Novel phosphorus-containing ligands have been synthesized by the condensation of 2-(thio)phosphorylated anilines with 2,6-dichloro- and 4-chloropyridine-2-carbonyl chlorides in the presence of Et₃N and unsubstituted pyridine-2-carboxylic acid using P(OPh)₃ as a coupling agent. The compounds derived readily form complexes with a range of transition metals (M=Re(I), Pd(II), and Cu(II)), serving as bi- or tridentate monoanionic ligands. The composition and structure of the resulting metallocycles depend both on the presence/amount of the Cl atoms in the pyridine ring and on the nature of the donor atom X in the P=X moiety. The novel compounds were characterized by multinuclear NMR and IR spectroscopy as well as X-ray crystallography.     

Synthesis,crystal structure,and BSA interaction with a new Co(II) complex based on 5-(trifluoromethyl)pyridine-2-carboxylic acid

Abstract

A new complex, Co(Htpc)₂(H₂O)₂ (1) (Htpc = 5-(trifluoromethyl)pyridine-2-carboxylic acid), has been synthesized and characterized by X-ray single-crystal diffraction, elemental analysis, infrared spectral analysis, and thermogravimetric analysis. Meanwhile, the optimized geometric structure of the ligand was determined using the M06-2X functional of density functional theory (DFT) with the 6-311?+?G(d, p) basis set. The gap energies ΔE between the frontier molecular orbitals were computed in different solvent media (water, methanol and ethanol) using the time dependent density functional theory (TD-DFT)/M06-2X by applying the Polarizable Continuum Model (PCM). The coordination sphere around Co(II) is distorted octahedral with two chelating tpc^- ligands and two coordinated water molecules. Bovine serum albumin (BSA) binding properties of the ligand, CoCl₂·6H₂O and 1 were investigated by fluorescence and UV–Vis absorption spectroscopy, revealing 1 exhibits higher binding affinity with BSA than free ligand and CoCl₂·6H₂O. ΔG, ΔH and ΔS at 298 and 308?K manifested that van der Waals interactions and hydrogen bonds were the main forces in the binding process.     

Zur Kenntnis der Organophosphorverbindungen. XV. Darstellung und Reaktionen von Trimethylsilylestern der Phosphinsäuren

On Organophosphorus Compounds. XV. Preparation and Reactions of Trimethylsilyl Esters of Phosphinic Acids Trimethylsilylesters of Phosphinic acids R₂P(X)YSi(CH₃)₃ (R ? CH₃, C₂H₅, C₃H₇, t?C₄H₉, C₆H₅; X, Y ? O, S) were prepared by 7 different methods as in some cases easily hydrolysable but thermally remarkably stable compounds. The properties and some reactions of these substances are reported, their structures confirmed by IR? as well as ¹H- and ³¹P-NMR-spectroscopy. Dimethylsilylen-bis(phosphinic acid esters) were obtained according to \documentclass{article}\pagestyle{empty}\begin{document}$ 2{\rm R}_{2} {\rm P(\rm X)\rm ONH}_{4} + {\rm R}_{\rm 2} {\rm SiCl}_{2} \to 2{\rm E NH}_{4} {\rm Cl + R}_{2} {\rm P(X) - O - SiR}_{2} - {\rm O - P(X)R}_{2} ({\rm R = CH}_{3};{\rm X = O,S}) $\end{document}.     

Synthesis of 2-Mercapto- and 2-Hydroxy-Substituted Diphenylphosphines for use as Dianionic Bidentate Ligands and Polydentate Ligand Precursors

Abstract

As part of our studies into the synthesis of polydentate phosphine-containing ligands, we have investigated the preparation of the phosphines (4; X[dbnd]O) and (4; X[dbnd]S). These are of interest both as potential dianionic bidentate ligands and as useful precursors of more complex polydentate ligand systems. A synthesis of the thiol system (4; X[dbnd]S) from 1,2-dinitrobenzene has been previously reported [1], but the observation [2], that 2-bromoaryl esters of phosphoric acid rearrange to give esters of arylphosphonic acids in the presence of alkyl lithiums, led us to consider whether a similar type of rearrangement might provide a convenient approach to both (4; X[dbnd]S) and (4; X[dbnd]O).     

Synthesis,structures and characterization of two new supramolecular coordination complexes with the ambidentate ligand 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot)

Two new coordination supramolecular complexes based on a versatile and unsymmetrical 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and Mn^II and Ni^II have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of MnCl₂?· 4H₂O with Hpot afforded a neutral mononuclear complex [Mn(pot)₂(H₂O)₄]?·?2H₂O (1), which exhibits a three-dimensional (3-D) supramolecule through versatile intermolecular O–H?···?X (X=O, N and S) hydrogen bond interactions. When using NiCl₂?·?6H₂O instead of MnCl₂?· 4H₂O under similar reaction conditions, a neutral mononuclear complex [Ni(pot)₂(H₂O)₄] (2) is also obtained, which does not exhibit intermolecular hydrogen bonds and π–π stacking interactions. It is very interesting that the pot anion exhibits different coordination modes in complexes 1 and 2. The IR spectra and the TGA for 1 and 2 have been investigated and discussed in detail.     

The effect of orientation of the lateral methyl substituent on the mesophase behaviour of 4-alkoxyphenylazo aryl benzoates

Two homologous series of 4-alkoxyphenylazo 4?-(2?- (and 3?-) methyl-) 4?-substituted benzoates (IIn_a–f and IIIn_a–f, six series each) were prepared and investigated. Within each series, the length of the terminal alkoxy group varies among 6, 8, 10 and 12 carbons, while the other terminal substituent, X, is a polar group that alternatively changes between the electron-donating CH₃O, CH₃, and the electron-withdrawing Br, NO₂ and CN groups, in addition to the un-substituted analogue, X = H, aiming to investigate the effect of the different orientations of the methyl groups substituted on the central benzene ring, on the mesophase behaviour. The mesomorphic properties were discussed in terms of steric and polarisability effects. The mesophase stability was correlated with the polarisability anisotropy of bonds to the terminal substituent X. Comparative studies were made between the prepared isomers with each other and with the previously investigated laterally neat analogues 4-(4?-alkoxyphenylazo) phenyl 4?-substituted benzoates (In_a–f).     

Synthesis and X-ray crystal structures of N,N,N′,N′-tetraalkylpyridine-2,6-dithiocarboxamides (S-dapt) complexes of cobalt(II) and nickel(II)

Reactions of anhydrous CoX₂ (X?=?Br^?, SCN^?) and Ni(ClO₄)₂ with N,N,N′,N′-tetraisobutylpyridine-2,6-dithiocarboxamides (S-dbpt), N,N,N′,N′-tetraisopropyl pyridine-2,6-dithiocarboxamides (S-dppt), and N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamides (S-dept) lead to the formation of [Co(S-dbpt)Br₂] (1), [Co(S-dppt)(SCN)₂] (2), and [Ni(S-dept)₂]·(ClO₄)₂·H₂O (3), respectively. The X-ray crystal structures of the three S-dapt ligands and three complexes along with spectroscopic analyzes are presented. The molecular structure investigations of the S-dapt ligands show that the thiamide planes are twisted with respect to the pyridine ring, which is more in the case of phenyl groups. The structures of the Co(II) complexes reveal that an increase in steric crowding on the amide side arms of the ligands has no substantial effect on the geometry adopted by the corresponding complexes. The Co(II) gives only 1?:?1 five-coordinate, ion-paired complexes with a distorted square pyramidal geometry. Ni(II), on the other hand, prefers an octahedral geometry with 1?:?2 metal–ligand ratio. The coordination behavior of S-dapt has been compared to the analogous oxo(O-daap) ligands. Lesser propensity of S atom to get involved in H-bonding interactions ensures an S-N-S type of tridentate coordination by S-dapt.     

Origin of diastereoselectivity in the thermal [4+2] cycloadditions of dienophiles derived from Oppolzer's sultams: Steric vs. Stereoelectronic Influences

Comparative semi-empirical PM3 and ab initio STO 3-21G calculations on bornanesultam-derived dienophiles containing the structural moiety SO₂? N? C(O)? X(α) = Y(β) suggest that, among the conformers of low energy, the thermodynamically less stable SO₂/C(O)-syn,C(O)/X=Y-s-cis conformation is also reactive in terms of LUMO level and atomic coefficients. Furthermore, the X(α), Y(β) LUMO atomic coefficients are nonequivalent with respect to both X(α)-re and X(α)-si faces, and thus have, depending on the conformation, a matching or mismatching stereoelectronic influence with the co-operative steric effect. This dissymmetry is believed to result from the generalized anemone effect of the N lone pair, itself anomerically stabilized and directed, in the absence of crucial steric interactions, by the pseudo-axial anti-periplanar S?O bond. Five N-acyl-substituted bornanesultams arc discussed ((–)- 1a : N-acryloyl, X?CH, Y?CH₂; (–)- 1b ; N-crotonoyl, X?CH, Y?CHMe; (–)- 1c : N-N′-fumaroyl, X?CH, Y?CH(C(O)-bornanesultam); 2a : N-glyoxyloyl, X?CH, Y?O; 2b : N-acylnitroso, X?N, Y?O). In this context, differences with toluenesultams 3 are pointed out. A previous report on N-(acylnitroso)-bornanesultam 2b is revisited, and the diastereoselectivity observed is shown to result from thermodynamic control.     

Metal Complexes of Thiophosphinic and Selenophosphinic Acids

The anions of thiophosphinic and selenophosphinic acids R₂P(X) YH (X = S, Se; Y = O, S, Se) can act as bidentate ligands. They combine with many metals to form complexes containing a four-membered chelate ring, or to give coordination polymers in which they form ligand bridges. The preparation, properties, and reactions of these compounds, as well as the dielectric properties and analytical use of dithiophosphinato complexes, which are also of industrial interest, are described. Some thiophosphinato and selenophosphinato complexes exhibit concentration-dependent association via ligand bridges. Evidence of the chelate nature of the ligands R₂P(X)Y? was obtained from IR spectroscopic studies. The ligand field parameters of the anion (C₂H₅)₂P(S)S? were deduced from the electronic spectra of octahedral diethyldithiophosphinato complexes, and the position of the ligand in the spectrochemical and nephelauxetic series were determined from these parameters.     

Mercury(II) complexes containing new ortho-functionalized asymmetric triazene ligands: synthesis,crystal structures,and solution studies

Synthesis of two new asymmetric ligands: 1-(2-ethoxyphenyl)-3-(2-methoxycarbonylphenyl)triazene (HL) (1) and 1-(2-methoxyphenyl)-3-(2-methoxycarbonylphenyl)triazene (HL′) (2) are reported. The prepared triazenes are functionalized by ethoxy and methoxy groups in the ortho positions, respectively. The related monomeric complexes, [HgL₂] (3) and [HgL′₂] (4), were prepared by the reacting of the corresponding ligands with Hg(NO₃)₂ salt in methanol as solvent. All compounds were characterized by CHN analysis, FT-IR, ¹H NMR, and ¹³C NMR spectroscopy. According to the crystal structures of 1 and 2, the N–N bond distances indicate the presence of alternating single and double bonds, and hence the –N=N–NH– moiety. On coordination, each triazene was deprotonated and as a result, a resonance structure is formed between nitrogens which let them to be a tridentate ligand. In the crystal structure of 3, [HgL₂], the central Hg(II) is surrounded by two N atoms from interlocked L forming linear geometry, in which the other four Hg–N and Hg–O bonds are longer and can only be regarded as weak secondary bonds. An interesting feature of 3 is also the presence of π?π [centroid–centroid distance of 3.744(3)?Å] and C–H?π interactions. The results of solution studies for the formation of 3 in methanol support its solid-state stoichiometry.