H.-K. Fun

Coordination chemistry and bioactivity of Ni2+, Cu2+, Cd2+ and Zn2+ complexes containing bidentate Schiff bases derived from S-benzyldithiocarbazate and the X-ray crystal structure of bis[S-benzyl-β-N-(5-methyl-2-furylmethylene)dithiocarbazato]cadmium(II)

New bidentate isomeric NS and NS′ Schiff bases were derived from the condensation of S-benzyldithiocarbazate (SBDTC) with 5-methyl-2-furyldehyde and 2-furyl-methylketone. Reaction of NS ligand with Ni(II), Cu(II), Cd(II) and Zn(II) salts gave solid complexes. Only the Ni(II) complex of the NS′ ligand was isolated. All complexes were characterized by a variety of physico-chemical techniques, viz. elemental analyses, molar conductivity, i.r. and electronic spectral studies. The Schiff bases behaved as uninegatively charged bidentate ligands. Square-planar structures have been proposed for the Cu(II) complex containing the NS Schiff base ligand and the Ni(II) complexes of the bidentate NS and NS′ Schiff base ligands. Single crystal X-ray diffraction study of [Cd(NS)2] showed that the complex was bis chelated with a distorted tetrahedral structure. The antimicrobial properties of the Schiff bases and their metal complexes indicate that the organic compounds are stronger antifungal agents than their complexes with the metals studied. However, the zinc complex of the Schiff base, S-benzyl-β-N-(5-methyl-2-furyl)methylenedithiocarbazate, (NS), was found to be highly active against CEM-SS (Human cell T-lymphoblastic leukemia) with a CD50 value of 2.0 μg cm−3, while [Cd(NS)2] was moderately active with a CD50 value of 4.95 μg cm−3. None of the compounds were found to be active against HT-29 (Human colon adenocarcinoma cells). The bioactivity of a previously reported tridentate NNS Schiff base (SBD1) and its metal complexes with nickel(II) and copper(II) are also discussed.

Coordination chemistry and bioactivity of some metal complexes containing two isomeric bidentate NS schiff bases derived from S-benzyldithiocarbazate and the x-ray crystal structures of S-benzyl-β-N-(5-methyl-2-furylmethylene)dithiocarbazate and bis[S-benzyl-β-N-(2-furylmethylketone)dithiocarbazato]cadmium(II)

Abstract Isomeric bidentate ligands having nitrogen–sulfur donor sequence were prepared by condensing S-benzyldithiocarbazate (SBDTC) with 5-methyl-2-furyladehyde (NS) and 2-furylmethylketone (NS′). Complexes of these ligands with lead, tin, iron, cobalt and cadmium gave complexes of [M(L)2] (M=Pb, Fe and Cd) and [M(L)2]Cln (M=Sn, n=2 and Co, n=1) (L=NS and NS′). The compounds have been characterized by spectroscopic studies (infrared, 1H NMR and electronic spectra). X-ray crystallographic analysis of S-benzyl-β-N-(5-methyl-2-furylmethylene)dithiocarbazate shows the presence of two independent molecules in the asymmetric unit. The molecule adopts a trans–cis configuration, as was observed in other analogues, such as SBDTC where the furylmethylene and benzyl groups are trans and cis about the NC and CS bonds, respectively. The molecular structure of bis[S-benzyl-β-N-(2-furylmethylketone)dithiocarbazato]cadmium(II) shows a tetrahedral geometry about the central cadmium atom with the bidentate ligand coordinating through the thioketo sulfur and the azomethine nitrogen atoms. The lead(II) complex of the NS ligand was highly cytotoxic against leukemic cells (CEM-SS) with a CD50 of 3.25 μg cm−3 while antimicrobial screening showed that the [Fe(NS)2]Cl2·H2O complex was effective against Aspergillus achraceous.

Synthesis of copper(II) and nickel(II) complexes using compartmental ligands: X-ray, electrochemical and magnetic studies

Abstract Acyclic dicompartmental ligands suitable for the complexation of transition-metal ions which can form mononuclear, homo- or heterodinuclear complexes have been synthesised. The mononuclear complexes ML1 (M=Cu, Ni) where L1=N,N′-bis[2-hydroxy-3-(morpholino-1-ylmethyl)-5-methylbenzyl]alkyldiimine (alkyl=ethylene, L1a; propylene, L1b; butylene, L1c; triethylenetetraamine, L1d); ML2 (M=Cu, Ni) where L2=N,N′-bis[2-hydroxy-3-(morpholino-1-ylmethyl)-5-methylbenzyl]alkyldiamine (alkyl=ethylene, L2a; propylene, L2b); and ML3 (M=Cu, Ni) where L3=N,N′-bis[2-hydroxy-3-(morpholino-1-ylmethyl)-5-bromobenzyl]alkyldiimine (alkyl=ethylene, L3a; propylene, L3b; butylene, L3c) have been synthesised and characterised by C, H, N analysis, IR, electronic and ESR spectra. The complexes CuH2L1a (1), CuH2L2a (4), NiH2L1a (9) and NiH2L1d (12) have been analysed by X-ray crystallography. Complexes 1 and 4 have square pyramidal geometry. The coordination geometry around the metal ion in complex 9 is square planar and in complex 12 it is octahedral. Electrochemical studies of the complexes show a single quasi-reversible electron transfer process at the negative potential region. For copper complexes (1–8) Epc=−1.10 to −0.70 V, for nickel complexes (9–12) Epc=−1.0 to −0.85 V. Copper complexes show a magnetic moment value of μeff=1.70–1.75 BM. The square planar nickel complexes are diamagnetic whereas the nickel complex (12) with octahedral structure has a magnetic moment value of 3.12 BM.

Synthesis and spectral studies on Ru3(CO)12−n(μ-Ph2AsCH2AsPh2)(L) (n = 3, L : PPh3, PCy2Ph,P(OCH3)3); n = 4, L = Ph2PCH2PPh2) : crystal and molecular structures of Ru3(CO)9(μ-Ph2AsCH2AsPh2)(PCy2Ph) and Ru3(CO)8(μ-Ph2AsCH2AsCH2AsPh2)μ-Ph2PCH2PPh2)

Abstract Mixed ligand triangulotriruthenium cluster carbonyls, Ru3(CO)9(μ-Ph2AsCH2AsPh2)(L) (L = PPh3, PCy2Ph, P(OCH3)3) and Ru3(CO)8(μ-Ph2AsCH2AsPh2)(μ-Ph2PCH2PPh2) were synthesised and characterised by microanalysis, IR, 1H, 13C and 31P NMR spectrometry. Single crystal X-ray structure determination of Ru3(CO)9(μ-Ph2AsCH2AsPh2)(PCy2Ph) and Ru3(CO)8(μ-Ph2AsCH2AsPh2(μ-Ph2PCH2PPh2) are reported. In both the clusters, the triruthenium framework is planar. In Ru3(CO)9(μ-Ph2AsCH2AsPh2)(PCy2Ph), the monodentate phosphine occupies an equatorial position for steric reasons. The effect of trisubstitution is explicit in the highly significant differences observed in RuRu distances (2.8301 (6), 2.8653(7) and 2.8873(7) A) in the present compound compared to Ru3(CO)10(μ-Ph2AsCH2AsPh2). The observed RuAs distances are 2.4508(7) and 2.4331(7) A respectively and the RuP distance is 2.362(1) A. In the case of Ru3(CO)8(μ-Ph2AsCH2AsPh2)(μ-Ph2PCH2PPh2), the chelating ligands occupy four equatorial positions. Two of the RuRu distances are similar in length (2.848(2), 2.850(2) and 2.828(2) A). However, positional disorder is associated with As and P atoms. Other bond parameters are normal.

Synthesis of mononuclear nickel(II) and copper(II) complexes using compartmental ligands: X-ray and electrochemical studies

Abstract A series of mononuclear complexes ML 1 (M=Ni, Cu) where L 1 = N , N ′-bis[2-hydroxy-3-(piperidin-1-ylmethyl)-5-methylbenzyl]alkyldiimine (alkyl=ethylene L 1a , propylene L 1b , butylene L 1c ) and ML 2 (M=Ni, Cu) where L 2 = N , N ′-bis[2-hydroxy-3-(piperidin-1-ylmethyl)-5-bromobenzyl]alkyldiimine (alkyl=ethylene L 2a , propylene L 2b , butylene L 2c ) have been synthesized and characterized by C, H, N analysis, IR, electronic and ESR spectra. The crystal structures of the complexes NiH 2 L 1a ( 1 ) and CuH 2 L 1a ( 6 ) were determined and the geometry around the metal ion is square planar. Electrochemical studies of the complexes show a quasi-reversible single redox wave at negative potential in the range 0 to −1.3 V. For nickel complexes ( 1 – 5 ) E pc =−1.0 to −0.80 V and for copper complexes ( 6 – 9 ) E pc =−0.90 to −0.72 V. The ESR spectra of nickel complexes are inactive due to square planar nature of the complexes whereas copper complexes show an ESR spectrum characteristic of square planar complex with nuclear hyperfine spin 3/2. Copper complexes show a normal magnetic moment value of μ eff =1.70–1.75 B.M. which is close to the spin-only value of 1.73 B.M.

Cooperative intramolecularly hydrogen-bonded motif in the structure of 2:2 complex of TBD with 4-nitrocatechol

Abstract In the crystal of the 2:2 complex of 1,5,7-triazabicyclo[4.4.0]dec-5-ene with 4-nitrocatechol the proton from 1-hydroxyl group of 4-nitrocatechol moiety is transferred to TBD to form ion-pair; two adjacent ion-pairs are linked across a center of inversion. The structure exhibits a cooperative, intramolecularly hydrogen-bonded motif. The hydrogen bonds are relatively long and, and they display only minor proton polarizability. The structure of the complex is retained in chloroform solution, as shown by FT-IR and 1H NMR measurement; in acetonitrile, the compound partially dissociates. The partial dissociation is implied by the presence of free cations, and also by that of the (O⋯H⋯O)− hydrogen bonds formed between two mono-deprotonated 4-nitrocatechol molecules.

Structural, spectroscopic and theoretical studies of the 2:2 complex of 5,5′-dibromo-2,2′-biphenol with 1,5,7-triazabicyclo[4.4.0]dec-5-ene

Abstract In the crystal of the 2:2 complex of 1,5,7-triazabicyclo[4.4.0]dec-5-ene with 5,5′-dibromo-2,2′-biphenol a cooperative inter-intra-molecular hydrogen-bonded system is formed. The intermolecular hydrogen bonds are relatively long [2.708(6) and 2.895(7)] and do not show large proton polarizability. The intramolecular OHO− hydrogen bond is relatively short [2.489(6)]. The structure of the complex is very well reflected in its FT-IR spectrum in the solid. On the basis of the FT-IR and 1H NMR studies of the complex in chloroform and in acetonitrile a structure different than in the solid is proposed. DFT structures of both isolated ions in their ground electronic states at the B3LYP/6-31++G(d,p) level are employed to follow the effects of the hydrogen bonding on the intrinsic ionic structures.

[4-(4-Methylphenyl)-3,5-bis(2-pyridyl)-4H-1,2,4-triazole]bis(triphenylphosphine)silver(I) perchlorate

The coordination geometry of silver(I) in the title compound, [Ag(C 19 H 15 N 5 )(C 18 H 15 P) 2 ]ClO 4 , is distorted tetrahedral. The pyridyl groups, the substituted benzene ring and the 1,2,4-triazole moiety do not share a common plane. The perchlorate ion is highly disordered and is involved in C-H...O hydrogen bonding.

N-H...S hydrogen bonding in N-benzoyl-N'-methyl-N'-phenylthiourea and N-benzoyl-N'-(3,4-dimethylphenyl)thiourea

In the title compounds, C 15 H 14 N 2 OS and C 16 H 16 N 2 OS, the C=S bond distances are 1.670(2) and 1.667(2)A, respectively. The molecules are packed in a centrosymmetric manner by forming a two-dimensional array through N-H...S hydrogen bonding.

Synthesis and characterization of [bis(β-diketonato)uranium(VI)]nitrone compounds. The crystal and molecular structure of [UO2(TTA)2·p-NO2C5H4NO]

Abstract N-oxide compounds of the type [UO2(OO)2·L] (OO=TTA, DBM, BA or BTA; L=C6H5CHN(O)C6H5 (L1), C6H5CHN(O)C6H4·CH3-p) (L2) or p-NO2C5H4NO) have been prepared and characterized by IR, 1H and 19F NMR spectroscopic and elemental analyses methods. Spectral studies show that the N-oxide ligands coordinate through its nitroxyl oxygen atom to the uranyl group. The single crystal X-ray structure of the compound [UO2(TTA)2·p-NO2C5H4NO] confirms the spectroscopic observations.