Assemblies of 1D and 2D Copper(II) Chiral Coordination Polymers by Salicylaldehyde Schiff Bases: Synthesis,Crystal Structures,and Magnetic Properties

Reaction of CuCl₂ · 2H₂O with chiral Schiff bases and sodium dicyanamide led to the formation of two chiral copper(II) coordination polymers, namely [Cu₄(L¹)₂(dca)₄]_n ( 1 ) and [Cu₂(L²)(μ‐Cl)(dca)(H₂O)]_n · nH₂O ( 2 ) {H₂L¹ = (1R, 3S)‐N′,N′′‐bis[salicylidene]‐1,3‐diamino‐ 1,2,2‐trimethylcyclopentane, H₂L² = (1R, 3S)‐N′,N′′‐bis[3‐ethoxysalicylidene]‐1,3‐diamino‐ 1,2,2‐trimethylcyclopentane, dca = dicyanamide}. Both complexes were structurally characterized by elemental analyses, IR spectroscopy and single‐crystal X‐ray diffraction. Complex 1 exhibits a two‐dimensional polymeric structure formed by single dca bridging tetranuclear Cu₄ units. Complex 2 displays a left‐handed helical chain structure constructed from Cu₂ dimers with single dca bridges. The chirality of 1 and 2 was confirmed by circular dichroism (CD) measurements in solution. Both complexes exhibit strong antiferromagnetic couplings with J = –308(4) cm^–1 for 1 and J = –123(1) cm^–1 for 2 in 2–300 K.     

Synthesis and characterization of diorganotin(IV) complexes of tetradentate Schiff bases: crystal structure of n-Bu2Sn(Vanophen)

Diorganotin(IV) complexes of the general formula R₂SnL (R=Ph, n-Bu and Me) have been prepared from diorganotin(IV) dichlorides (R₂SnCl₂) and tetradentate Schiff bases (H₂L) containing N₂O₂ donor atoms in the presence of triethylamine in benzene. The Schiff bases, H₂L, were derived from salicylaldehyde, 3-methoxysalicylaldehyde (o-vanillin), 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and diamines such as o-phenylenediamine and 1,3-propylenediamine. The complexes were characterized by IR, NMR (¹H, ¹³C, ¹¹⁹Sn) and elemental analysis. The structure of the complex, n-Bu₂Sn(Vanophen), was determined using single crystal X-ray diffraction. The tin atom has a distorted octahedral coordination, with the Vanophen ligand occupying the four equatorial positions and the n-butyl groups in the trans axial positions. Six-coordinated distorted octahedral structures have been proposed for all diorganotin(IV) complexes studied here, as they possess similar spectroscopic data.     

Schiff base supported mononuclear organotin(IV) complexes: Syntheses,structures and fluorescence cell imaging

Three mononuclear organotin(IV) complexes supported by Schiff bases have been synthesized. The complexes [(C₆H₅)₂Sn(L)] ( 1 ), [(t‐Bu)₂Sn(L)] ( 2 ) and [(t‐Bu)₂Sn(L')] ( 3 ) (L, L' = deprotonated Schiff bases) were obtained in good yield by the reaction of Schiff bases H ₂ L or H ₂ L′ with corresponding diorganotin dichlorides respectively. All newly synthesized complexes were characterized by means of FT‐IR spectroscopy, elemental analysis and multinuclear (¹H, ¹³C and ¹¹⁹Sn) NMR spectroscopy. In addition, single crystal X‐ray diffraction analyses were employed to establish the solid state molecular structures of these complexes. The structures of 1 – 3 reveal that all complexes are mononuclear with a five‐coordinated tin(IV) centre in it. The absorption and emission properties of all complexes have been investigated. Moreover, cytotoxicity and fluorescence cell imaging studies of theses complexes have been performed.     

Synthesis,structural characterization and in vitro cytotoxicity of diorganotin complexes with Schiff base ligands derived from 3‐hydroxy‐2‐naphthoylhydrazide

A series of diorganotin complexes with Schiff base ligands, (E)‐N′‐(5‐bromo‐2‐hydroxybenzylidene)‐3‐hydroxy‐2‐naphthohydrazide, H₂L1, and (E)‐N′‐(5‐chloro‐2‐hydroxybenzylidene)‐3‐hydroxy‐2‐naphthohydrazide, H₂L2, were synthesized and characterized by elemental analysis, IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. The molecular structures of the complexes, [(5‐bromo‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]di(o‐chlorobenzyl)tin(IV) 6 and [(5‐chloro‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]dibutyltin(IV) 9, were determined through single‐crystal X‐ray diffraction and revealed a distorted trigonal‐bipyramidal configuration. The in vitro cytotoxic activity of the Schiff bases and their diorganotin complexes was also evaluated against several human carcinoma cell lines, namely HT29 (human colon carcinoma cell line), SKOV‐3 (human ovarian cancer cell line), MCF7 (hormone‐dependent breast carcinoma cell line) and MRC5 (non‐cancer human fibroblast cell line). [(5‐Bromo‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]dibutyltin(IV) 2 and [(5‐bromo‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]dibenzyltin(IV) 5 were the most active diorganotin complexes of H₂L1 ligand. Among the diorganotin complexes of H₂L2 ligand, [(5‐chloro‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]dicyclohexyltin(IV) 11 showed good cytotoxic activity against all the tested cell lines. As such, the above compounds can be considered agents with potential anticancer activities, and can therefore be investigated further in in vitro or in vivo anticancer studies. Copyright © 2012 John Wiley & Sons, Ltd.     

Experimental and theoretical studies of the products of addition–elimination reactions between benzil dihydrazone and three isomeric chlorobenzaldehydes

A series of mono‐ and di‐Schiff bases formed between benzil dihydrazone {BDH; systematic name: (1Z)‐[(2E)‐2‐hydrazinylidene‐1,2‐diphenylethylidene]hydrazine} and three isomeric chlorobenzaldehydes were designed and synthesized to be used as model compounds to help to explain the reaction mechanisms for the formation of Schiff bases. These compounds are 1‐(2‐chlorobenzylidene)‐2‐{2‐[2‐(2‐chlorobenzylidene)hydrazin‐1‐ylidene]‐1,2‐diphenylethylidene}hydrazine (BDHOCB), and the 3‐chloro (BDHMCB) and 4‐chloro (BDHPCB) analogues, all having the formula C₂₈H₂₀Cl₂N₄. Surprisingly, only di‐Schiff bases were obtained; our attempts to push the reaction in favour of the mono‐Schiff bases all failed. Density functional theory (DFT) calculations were performed to explain the trend in the experimental results. In the case of the systems studied, the type of Schiff base produced exhibits a clear dependence on the HOMO–LUMO energy gaps (ΔE_HOMO–LUMO), i.e. the product is mainly governed by its stability. The compounds were characterized by single‐crystal X‐ray diffractometry, elemental analysis, melting point, ¹H NMR and ¹³C NMR spectroscopy. The structural features of the three new Schiff bases are similar. For instance, they have the same chemical formula, all the molecules have a symmetrical double helix structure, with each Ph—C=N—N=C—Ph arm exhibiting an anti conformation, and their supramolecular interactions include intermolecular π–π and weak C—H...π stacking interactions. The crystal systems are different, however, viz. triclinic (space group P) for BDHPCB, monoclinic (space group P2₁/n) for BDHOCB and orthorhombic (space group Pnna) for BDHMCB.     

A one‐dimensional coordination polymer formed from the reaction of 1,1‐diphenyl‐3,3′‐[(1R,2R)‐cyclohexane‐1,2‐diylbis(azanediyl)]dibut‐2‐en‐1‐one with MnCl2·4H2O

In the title coordination polymer, catena‐poly[[dichloridomanganese(II)]‐μ‐1,1‐diphenyl‐3,3′‐[(1R,2R)‐cyclohexane‐1,2‐diylbis(azaniumylylidene)]dibut‐1‐en‐1‐olate‐κ²O:O′], [MnCl₂(C₂₆H₃₀N₂)]_n, synthesized by the reaction of the chiral Schiff base ligand 1,1‐diphenyl‐3,3′‐[(1R,2R)‐cyclohexane‐1,2‐diylbis(azanediyl)]dibut‐2‐en‐1‐one (L) with MnCl₂·4H₂O, the asymmetric unit contains one crystallographically unique Mn^II ion, one unique spacer ligand, L, and two chloride ions. Each Mn^II ion is four‐coordinated in a distorted tetrahedral coordination environment by two O atoms from two L ligands and by two chloride ligands. The Mn^II ions are bridged by L ligands to form a one‐dimensional chain structure along the a axis. The chloride ligands are monodentate (terminal). The ligand is in the zwitterionic enol form and displays intramolecular ionic N⁺—H...O⁻ hydrogen bonding and π–π interactions between pairs of phenyl rings which strengthen the chains.     

Synthesis,spectral analysis and in vitro cytotoxicity of diorganotin (IV) complexes derived from indole-3-butyric hydrazide

A series ( 1–20 ) of diorganotin (IV) complexes with general formula R₂SnL were formed by the reaction of R₂SnCl₂ (where R = Me, Et, Bu and Ph) with Schiff base ligands ( H ₂ L ^1–4 ) derived from the reaction of indole-3-butyric hydrazide with the salicylaldehyde and its derivatives. The structure elucidation of compounds were done by using UV–Vis, FT-IR, NMR (¹H, ¹³C, ¹¹⁹Sn), Mass spectrometry and thermal gravimetric analysis. Spectroscopic evidences suggested tridentate nature (ONO) of Schiff base ligands and coordinated to the dialkyl/diaryltin (IV) moieties through nitrogen and oxygen donor sites giving pentacoordinated geometry to complexes. The compounds were tested for the antimicrobial activity against bacterial and fungal strains which showed promising biological activity with compound 20 (Ph₂SnL⁴) as most active against microbes. The in silico study of the compounds was carried and observed that the compounds are used as orally active drugs and promote the formation of different hydrazide based drugs. The synthesized compounds were tested against human carcinoma cell lines namely A549, MCF7 and one normal cell line IMR 90 using MTT assay. The diethyl and dibutyltin complexes of Schiff bases displayed good cytotoxic activities. Compound 3 (H₂L³) and 10 (Et₂SnL²) were most potent against cancer cell lines with lowest IC₅₀ values and 7–8 times less toxic against the normal cell line.     

Electrochemical Synthesis and Characterization of Tin(IV) Complexes of Dianionic Terdentate Schiff Base Ligands

Tin(IV) complexes of the series of dianionic terdentate Schiff bases N‐[(2‐pyrroyl)methylidene]‐N′‐tosylbenzene‐1,2‐diamine, (H₂L¹), N‐[(2‐hydroxyphenyl)methylidene]‐N′‐tosylbenzene‐1,2‐diamine (H₂L²) and some R substituted 2‐{[(2‐hydroxyphenyl)imino]methyl}phenols [R = H (H₂L³), 4,6‐(OCH₃)₂ (H₂L⁴), 3‐(OC₂H₅) (H₂L⁵) and 3,5‐Br₂ (H₂L⁶)] have been synthesized. The compounds were obtained by the electrochemical oxidation of a tin anode in a cell containing an acetonitrile solution of the corresponding ligand. The complex [SnL¹₂] was also obtained by reaction of SnCl₂·2H₂O and H₂L¹ in methanol in the presence of triethylamine. The crystal structure of the ligand [H₂L⁶] and the complexes [SnL¹₂] (1) , [SnL²₂] (2) , [SnL³₂] (3) and [SnL⁶₂] (6) were determined by X‐ray diffraction. In the complexes, the tin atom is in an octahedral environment coordinated by two dianionic terdentate ligands. Spectroscopic data for the complexes (IR, ¹H and ¹¹⁹Sn NMR and mass spectra) are discussed and related to structural information.     

Synthesis and physico-chemical and biological studies on ruthenium (III) complexes with Schiff bases derived from aminocarboxylic acids

Summary Ruthenium(III) complexes of types [Ru(L)₃], [Ru(L)Cl(H₂O)₂], [Ru(L)Cl₂]_n, [Ru(L)Cl(H₂O)]_n(LH =Schiff bases derived from anthranilic acid and benzaldehyde, acetophenone, vanillin, cinnamaldehyde orm-hydroxyacetophenone; LH₂=Schiff bases derived from anthranilic acid and salicylaldehyde oro-hydroxyacetophenone; LH=Schiff bases derived fromp-aminobenzoic acid and benzaldehyde, acetophenone, vanillin, cinnamaldehyde orm-hydroxyacetophenone; LH₂=Schiff bases derived fromp-aminobenzoic acid and salicylaldehyde oro-hydroxyacetophenone) have been synthesized and characterized on the basis of elemental analyses, conductance, magnetic moment and spectral (electronic, i.r. and¹H n.m.r.) data. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of crystal field theory and various parameters have been evaluated. On the basis of the electronic spectra, an octahedral geometry has been established for all these complexes except [Ru(L)Cl₂]_n. The complexes [Ru(L)Cl₂]_n are pentacoordinate and a trigonal-bipyramidal environment, D_3h, is suggested for the ruthenium(III) ion. The thermal behaviour of these complexes has also been studied by t.g., d.t.g and d.s.c techniques. Heats of reaction for the decomposition steps were calculated from the d.s.c. curves. The antifungal and antiviral activities of the complexes with Schiff bases derived from anthranilic acid were also investigated.     

Synthesis, structural characterization and antibacterial activity of 2,6-diacetylpyridine bis(benzenesulfonohydrazide) Schiff bases and their copper(II) complexes

2,6-Diacetylpyridine bis(benzenesulfonohydrazide) Schiff bases (L¹, L² and L³) and their Cu(II) complexes of the general formula [CuL·H₂O] were synthesized and characterized by various spectroscopic techniques. The crystal structure of [CuL³·(py)]·py was investigated by single crystal X-ray structure analysis. The Cu(II) cation has near square pyramidal, penta-coordinate geometry. The binegatively charged tetradentate Schiff base is asymmetrically coordinated to the Cu(II) ion via the pyridine N atom, the azomethine N atom, the sulfonyl O atom and the deprotonated hydrazine N atom. There is a pyridine molecule apically coordinated to the Cu(II) ion. All the Schiff bases and their copper(II) complexes were screened by the disc diffusion method against multi-drug resistant (MDR) gram-negative and gram-positive bacteria. The minimum inhibitory concentration (MIC) values were also determined. These results show that the antibacterial activity of the Schiff bases against Methicillin-resistant Staphylococcus aureus (MRSA) is enhanced when they are chelated with the copper(II) ion.     

Syntheses,Spectral, and Biological Studies of New Imines Derived From 5-Bromothiophene-2-Carboxaldehyde and Their Si(IV), Sn(IV) Complexes

The Schiff bases (imines) HL¹ and HL² have been synthesized by the reaction of 5-bromothiophene-2-carboxaldehyde with 4-amino-5-mercapto-1,2,4-triazole and 4-amino-3-ethyl-5-mercapto-1,2,4-triazole, respectively. Organosilicon(IV) and organotin(IV) complexes having the general formulae R₂MCl(L¹), R₂MCl(L²), R₂M(L¹)₂, R₂M(L²)₂, (M = Si, Sn; R = CH₃) were synthesized by the reaction of R₂MCl₂ with these Schiff bases in 1:1 and 1:2 molar ratio. The Schiff bases and their metal complexes have been characterized with the aid of elemental analyses, molar conductance, and spectroscopic studies, including UV, IR, ¹H, ¹³C, MS, ²⁹Si, and ¹¹⁹Sn NMR spectroscopy. On the basis of these studies, the resulting complexes have been proposed to have trigonal bipyramidal and octahedral geometries. In vitro activities of the Schiff bases and their metal complexes against some Gram positive and Gram negative bacteria and fungi have been carried out and described.     

Syntheses and Structures of Zinc Bis(phosphinimino)methanide Complexes

Reactions of bis(phosphinimino)methanes H₂C(PPh₂NR)₂ [R = SiMe₃ (L¹H), Ph (L²H), 2,6‐iPr₂‐C₆H₃ (DIPP) (L³H)] with ZnR₂ (R = Me, Et) yielded the corresponding bis(phosphinimino)methanide zinc complexes LZnMe [L² ( 1 ), L³ ( 2 )] and LZnEt [L¹ ( 3 ), L² ( 4 ), and L³ ( 5 )]. Complexes 1 – 5 were characterized by heteronuclear NMR (¹H, ¹³C, ³¹P) and IR spectroscopy, elemental analysis, and single‐crystal X‐ray diffraction.     

New diorganotin(IV) complexes with some Schiff bases derived from β-diketones: synthesis,spectral properties,thermal analysis,and antibacterial activity

The Schiff bases H₂L^a, H₂L^b, and H₂L^c have been prepared from the reaction of 2-amino-4-chlorophenol with acetylacetone, benzoylacetone, and dibenzoylmethane, respectively. Organotin(IV) complexes [SnPh₂(L^a)] (1), [SnPh₂(L^b)] (2), [SnPh₂(L^c)] (3), and [SnMe₂(L^c)] (4) have been synthesized from the reaction of SnPh₂Cl₂ and SnMe₂Cl₂ with these Schiff bases. The synthesized complexes have been characterized by elemental analysis and FT-IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy. Spectroscopic data suggest the Schiff bases are completely deprotonated and coordinated tridentate to tin via imine nitrogen and phenolic and enolic oxygen atoms; the coordination number of tin is five. Thermal decomposition of the complexes has been studied by thermogravimetry. The in vitro antibacterial activities of the Schiff bases and their complexes have been evaluated against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. H₂L^a, H₂L^c, and all complexes exhibited good activities and have potential as drugs.     

Synthesis,spectral studies,and antimicrobial activity of binary and ternary Cu(II), Ni(II), and Fe(III) complexes of new hexadentate Schiff bases derived from 4,6-diacetylresorcinol and amino acids

Two new hexadentate N₂O₄ donor Schiff bases, H₄L¹ and H₄L², were synthesized by condensation of 4,6-diacetylresorcinol with glycine and alanine, respectively. The structures of the ligands were elucidated by elemental analyses, IR, ¹H NMR, electronic, and mass spectra. Reactions of the Schiff bases with copper(II), nickel(II), and iron(III) nitrates in 1 : 2 molar ratio gave binuclear metal complexes and, in the presence of 8-hydroxyquinoline (8-HQ) or 1,10-phenanthroline (Phen) as secondary ligands (L′), mixed-ligand complexes in two molar ratios 1 : 2 : 2 and 1 : 2 : 1 (L¹/L² : M : L′). The complexes were characterized by elemental and thermal analyses, IR, electronic, mass, and ESR spectral studies, as well as conductivity and magnetic susceptibility measurements. The spectroscopic data reveal that the Schiff-base ligands were dibasic or tetrabasic hexadentate ligands. The coordination sites with the metal ions are two azomethine nitrogens, two oxygens of phenolic groups, and two oxygens of carboxylic groups. Copper(II) complexes were octahedral and square planar while nickel(II) and iron(III) complexes were octahedral. The Schiff bases, H₄L¹ and H₄L², and some of their metal complexes showed antibacterial activity towards Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) and Gram-negative (Pseudomonas fluorescens and Pseudomonas phaseolicola) bacteria and antifungal activity towards the fungi Fusarium oxysporium and Aspergillus fumigatus.     

Syntheses,spectroscopy, and X-ray structures of 3-{(R)-(Ar)-ethylimino}-1,3-dihydro-indol-2-one (Ar = Ph,MeOC6H4, BrC6H4, 1-naphthyl) and [Rh(η4-cod){3-((R)-(Ar)-ethylimino)-3H-indol-2-olato}]

Condensation of 1H-indole-2,3-dione (isatin) with (R)-(Ar)-ethylamines gives enantiopure Schiff bases, 3-{(R)-(Ar)-ethylimino}-1,3-dihydro-indol-2-one (HL) {Ar?=?Ph (HL1), 2-MeOC₆H₄ (HL2), 4-MeOC₆H₄ (HL3), 4-BrC₆H₄ (HL4), and 1-naphthyl (HL5)}. The Schiff bases readily coordinate to [Rh(μ-O₂CMe)(η⁴-cod)]₂ (cod?=?1,5-cyclooctadiene) to give mononuclear [Rh(η⁴-cod){3-((R)-(Ar)-ethylimino)-3H-indol-2-olato}] {Ar?=?Ph (1), 4-MeOC₆H₄ (2), and 4-BrC₆H₄ (3)}, respectively. The Schiff bases and complexes have been fully characterized by IR, UV-Vis, ¹H-NMR, mass, and circular dichroism (CD) spectrometry. Polarimetry and CD measurements show the enantiopurity of the Schiff bases as well as the complexes. ¹H NMR measurements reveal slow conversion of the lactam to the enol form of the Schiff bases in solution. In the solid state the lactam form dominates as shown by crystal structures of HL1 and HL4. While gross structural features of both are similar, the molecules differ significantly in the relative orientations of the aryl and lactam rings. The difference is mostly rotation about the N2–C9 bond with different C8–N2–C9–C11 torsion angle of +89.77(12)° for HL1 and C2–N2–C9–C11 of +106.8(3)° for HL4.     

Adducts of tellurium and organotellurium(IV) chlorides with transition metal chelates of tetradentate schiff bases

Summary Coordinative interaction between tellurium tetrachloride or aryltellurium trichloride and transition metal chelates of tetradentate Schiff bases has yielded bimetallic molecular adducts of the general formula R_nTeCl_4–n · ML [n = 0 or 1, R = Ph,p-MeOC₆H₄ orp-EtOC₆H₄, M = nickel(II) or copper(II) and L^2– dianion of the Schiff bases derived from salicylaldehyde oro-hydroxyacetophenone and ethylenediamine]. The i.r. spectral and magnetic measurements on the complexes in the solid state indicate coordination of the metal chelates to tellurium(IV)via two phenolic oxygens. Planarity about the transition metal ion is thus retained.     

S,N‐Chelated organotin(IV) compounds containing 6‐phenylpyridazine‐3‐thiolate ligand—structural,antibacterial and antifungal study

A series of tri‐ and diorganotin(IV) compounds containing potentially chelating S,N‐ligand(s) (L^SN, where L^SN is 6‐phenylpyridazine‐3‐thiolate) were prepared and structurally characterized by multinuclear NMR spectroscopy. X‐ray diffraction techniques were used for determination of the structure of compounds containing one [(L^SN)Ph₂SnCl], two [(n‐Bu)₂Sn(L^SN)₂] and the combination of two L^SN and one L^CN [(L^CN)(n‐Bu)Sn(L^SN)₂] (where L^CN is {2‐[(CH₃)₂NCH₂]C₆H₄}‐) ligands. The coordination number of the tin atom varies from five to seven and is dependent on the number of chelating ligands present. The formation of the five‐membered azastanna heterocycle is favored over the formation of four‐membered azastannathia heterocycle in compounds containing both types of ligands. The di‐n‐butyl‐substituted compounds are the most efficient ones in inhibition of growth of yeasts, molds and G⁺ bacteria strains. Copyright © 2011 John Wiley & Sons, Ltd.     

Asymmetric oxidation of sulfides with H2O2 catalyzed by titanium complexes of Schiff bases bearing a dicumenyl salicylidenyl unit

The sterically hindered Schiff bases (L³–L⁵), prepared from 3,5‐dicumenyl salicylaldehyde and chiral amino alcohols, were used in combination with Ti(OiPr)₄ for asymmetric oxidation of aryl methyl sulfides with H₂O₂ as terminal oxidant. Among the ligands L³–L⁵, L⁴ with a tert‐butyl group in the chiral carbon of the amino alcohol moiety gave the best result with 89% yield and 73% ee for the sulfoxidation of thioanisole under optimal conditions [with 1 mol% of Ti(OiPr)₄ in a molar ratio of 100:1:1.2:120 for sulfide:Ti(OiPr)₄:ligand:H₂O₂ in CH₂Cl₂ at 0 °C for 3 h]. The reaction afforded good yield (84%) with a moderate enantioselectivity (62% ee) even with a lower catalyst loading from 1.0 to 0.5 mol%. The oxidations of methyl 4‐bromophenyl sulfide and methyl 4‐methoxyphenyl sulfide with H₂O₂ catalyzed by the Ti(OiPr)₄–L⁴ system gave 79–84% yields and 54–59% ee of the corresponding sulfoxides in CH₂Cl₂ at 20 °C. The chiral induction capability of the cumenyl‐modified sterically hindered Schiff bases for sulfoxidation was compared with the conventional Schiff bases bearing tert‐butyl groups at the 3,5‐positions of the salicylidenyl unit. Copyright © 2011 John Wiley & Sons, Ltd.     

New complexes of Ni(II) and Cu(II) with Schiff bases functionalised with 1,3,4-thiadiazole: spectral,magnetic, biological and thermal characterisation

Schiff bases obtained by the condensation of 2-amino-5-mercapto-1,3,4-thiadiazole with 2,4-pentandione or 1-phenyl-1,3-butandione were synthesized and characterized in order to obtain polydentate ligands HL¹ and HL², respectively. The complexes with these ligands of the type M(L)Cl·nH₂O [(1) M:Ni, L:L¹, n = 0.5; (3) M:Ni, L:L², n = 0.5]; [(2) M:Cu, L:L¹, n = 1; (4) M:Cu, L:L², n = 0] were also synthesized and characterized. The modifications evidenced in IR spectra of complexes were correlated with the presence of monodeprotonate Schiff bases. The electronic spectra display the characteristic pattern of square-planar stereochemistry. The in vitro qualitative and quantitative antimicrobial activity assays showed that the new complexes exhibited variable antimicrobial activity. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Schiff bases and complexes have a similar thermal behaviour. Processes as water elimination, melting, chloride anion removal as well as oxidative degradation of the organic ligands were observed.     

Synthesis,structures, and urease inhibition of nickel(II), zinc(II), and cobalt(II) complexes with similar hydroxy-rich Schiff bases

Four new nickel(II), zinc(II), and cobalt(II) complexes, [Zn(L¹)₂]?·?H₂O (1), [Ni(L¹)₂]?·?H₂O (2), [Ni(L²)₂] (3), and [Co(L³)₂]?·?H₂O (4), derived from hydroxy-rich Schiff bases 2-{[1-(5-chloro-2-hydroxyphenyl)methylidene]amino}-2-methylpropane-1,3-diol (HL¹), 2-{[1-(2-hydroxy-3-methoxyphenyl)methylidene]amino}-2-ethylpropane-1,3-diol (HL²), and 2-{[1-(5-bromo-2-hydroxyphenyl)methylidene]amino}-2-methylpropane-1,3-diol (HL³) have been synthesized and characterized by elemental analyses, infrared spectroscopy, and single-crystal X-ray determination. Each metal in the complexes is six-coordinate in a distorted octahedral coordination. The Schiff bases coordinate to the metal atoms through the imino N, phenolate O, and one hydroxyl O. In the crystal structures of HL¹ and the complexes, molecules are linked through intermolecular O–H···O hydrogen bonds, forming 1-D chains. The urease inhibitory activities of the compounds were evaluated and molecular docking study of the compounds with the Helicobacter pylori urease was performed.