Search

The effect of the substituents at the N 1 /C 2 atoms of the thiosemicarbazones R 1 R 2 C 2 = N 3 -N 2 H-C 1 (=S)-N 1 HR 3 on the type of gold(I) complexes is investigated. Direct reaction of gold(I) chloride with benzaldehyde-N-methyl thiosemicarbazones (HL 1 : R 1 = Ph, R 2 = H, R 3 = Me) in a 1:2 M ratio in acetonitrile has yielded an ionic complex, [Au(κ 1 -S-HL 1 ) 2 ]Cl ( 1 ). Similarly, the reaction of benzaldehyde-N-ethyl thiosemicarbazone (HL 2 : R 1 = Ph, R 2 = H, R 3 = Et) has formed another ionic complex, [Au(κ 1 -S-HL 2 ) 2 ]Cl ( 2 ). The complexes have been characterized using analytical data, spectroscopy (IR, 1 H, 13 C NMR, UV–Vis), fluorescence, ESI-mass and X-ray crystallography. Complexes 1 and 2 represent the first examples obtained from the direct reactions of gold(I) chloride with a thio-ligand without the presence of PPh 3 or the use of any intermediate substrate, as has normally been used. Complex 1 , with a methyl substituent at N 1 , has two independent molecules in the crystal lattice, while complex 2 , with an N-ethyl substituent, has only one type of molecule in the crystal lattice. ESI-mass studies reveal the formation of the species: [Au I Cl+H] + ( A ), [Au I Cl 2 (HL 1 )+2H] + ( B ), [Au I (HL 1 ) 2 ] + ( C ) (complex 1 ) and [Au I (HL 2 ) 2 -4H] + ( D ) (complex 2 ). Interestingly both complexes have shown intense fluorescence bands in the wide region 340–540 nm, corresponding to the excitation wavelength of 308 nm. [ABSTRACT FROM AUTHOR]

Abstract: This review describes the coordination chemistry of thiosemicarbazones and covers all the metals for which complexes are reported. The coordination compounds of d-block, p-block and f-block elements are discussed with respect to their bonding and structures. The description of work is group by group and with a given metal, coordination compounds of all the ligands under purview are described. A brief description of synthesis and spectroscopy of complexes is also given. Several of complexes are mononuclear, with distorted tetrahedral, square planar, square pyramid or octahedral as their common geometries. Dimers, trimers, tetramers, as well as complexes of higher nuclearity are also reported. Variable bonding properties, metallation, metal–metal interactions, role of solvents/other factors in stabilization of sulfur-bridging in coinage metals, and the nature of substituents at azomethine carbon are other interesting features of the review. Further, biological and analytical applications of the ligands/complexes are included in brief so as to indicate the importance of ligands under consideration. The literature survey is complete to December 2007, and some papers of more recent origin are included. [Copyright &y& Elsevier]

• Two distinct g values (g ‖ and g ⊥) indicate axial symmetry for the copper(II) complexes. • Excellent anti-TB activity of ligands and complexes. • Pharmacokinetics (effective transport of molecule to their target sites) studied using drug-protein binding study of molecules with human serum albumin (HSA). • Interaction of ligands and their complexes with mycobacterium tuberculosis enoyl reductase was studied by molecular docking. Reaction of copper (II) acetate with 2,5 thiophenedicarboxaldehyde bisthiosemicarbazone (2,5 H 2 bttsc, 1H 2 L), 2,5 thiophenedicarboxaldehyde-N1-methyl bisthiosemicarbazone (2,5 H 2 bttsc-N1-Me, 2H 2 L) and 2,5 thiophenedicarboxaldehyde -N1-phenyl bisthiosemicarbazone (2,5 H 2 bttsc-N1-Ph, 3H 2 L) in 1:1 (M:L) molar ratio yielded complexes of stoichiometry, [Cu(L)] 1-3 (1L, 1; 2L 2; 3L 3). All the complexes are characterized using elemental analysis FTIR, Mass and ESR spectroscopy. The two distinct g values, g ‖ = 2.40 (1), 2.15 (2), 2.20 (3) and g ⊥ = 2.08 (1), 2.07 (2), 2.12 (3) indicate axial symmetry for the complexes. The greater g ‖ value than g ⊥, confirms the presence of free electrons in d x2-y2 ground term in square planar geometry. The ligands (1H 2 L - 3H 2 L) and their complexes (1–3) were tested for DPPH radical scavenging, ABTS radical scavenging, FRAP ferric reducing, and CUPRAC cupric reducing antioxidant capacity assays. In general, all the ligands and their metal complexes exhibited moderate antioxidant potential, however 3H 2 L has shown best Cu2+ reducing activity (7.34 μg TE/ml) and ABTS radicals scavenging activity (IC 50 , 16.95) amongst all. Ligands (1H 2 L - 3H 2 L) and their complexes (1–3) were also evaluated for anti-tuberculosis activity against M. tuberculosis H37RV strain. It has been observed that with the increase of hydrophobicity of ligand due to substituent present at N1 atom, anti-TB activity increased (H, MIC = 6.25 µg/ml < Me, MIC = 3.12 µg/ml < Ph, MIC = 1.6 µg/ml). Molecular modeling studies have shown considerable intermolecular interaction of these compounds with minimum binding energy −5.8 (1H 2 L), −5.8 (2H 2 L), −9.6 (3H 2 L), −6.9 (1), −6.6 (2) and −9.6 (3) Kcal/ mol, which also supports the experimental data. Pharmacokinetics (effective transport of molecule to their target sites) was studied using drug-protein binding study of molecules with human serum albumin (HSA) was performed using UV–vis and fluorescence spectroscopy. The ligand 2H 2 L and complex 2 showed strong binding interactions with HSA having binding constant values of 4.24 × 105 M−1 and 4.92 × 105 M−1 respectively. N1-Substituted 2,5 thiophenedicarboxaldehyde bisthiosemicarbazones and their copper(II) complexes are synthesized and characterized using various spectroscopic techniques. All the compounds have shown good anti-tuberculosis activity against M. tuberculosis H37RV strain. Mode of interaction and their delivery to target site was studied using molecular docking and BSA binding studies. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Reaction of copper(II) acetate with cyclohexanoneselenosemicarbazone (Hcysesc), 5-chloro isatinselenosemicarbazone (5-ClHIstsesc), 1-methyl isatinselenosemicarbazone (1-MeHIstsesc), 3-indole selenosemicarbazone (3-HInsesc), 3-acetylindole selenosemicarbazone (3-AcHInsesc and 2-naphthaldehyde selenosemicarbazone (2-Hnaphsesc) in 1:2 (M: L) molar ratio yielded complexes of stiochiometry, [Cu(L) 2 ] 1 – 6 (L = cysesc 1 ; 5-ClIstsesc 2 ; 1-MeIstsesc 3 ; 3-Insesc 4 ; 3-AcInsesc 5 ; 2-naphsesc 6). All the complexes are characterized by IR, Mass and ESR spectroscopy. Two well defined g values (g ‖ and g ⊥) in ESR spectrum of complexes 1 – 4 , 6 indicate axial symmetry, whereas symmetry around copper(II) metal in complex 5 is confirmed by three different g values (g 1 , 2.095; g 2 , 2.15; g 3 , 2.26), which supports rhombic distortion. The value of g ‖ obtained is greater than g ⊥, which is greater than g e, in 1 – 4 , 6 is in well agreement in d x2-y2 ground term of square planar geometry. The value of empirical factor f for complexes 1 – 4, 6 lies in the range, 102–135 cm indicating a square planar geometry with small distortion, where as in complex 5 value (f = 146 cm) is in conformity of tetrahedral geometry with larger distortion. All the compounds (selenosemicabazones and their complexes) are tested for DPPH radical scavenging, ABTS radical scavenging, FRAP ferric reducing and CUPRAC cupric reducing antioxidant capacity assay and all the compounds have shown good antioxidant capacity in general. Best results are obtained for H1L with FRAP, 6.75 ± 0.01 μg TE/ml and CUPRAC, 9.52 ± 0.07 μg TE/ml. All the compounds are also tested for their anti-tubercular activity against M. tuberculosis H37RV strain ATCC27294. Ligands, H1L , H3L , H6L and complex 6 have shown highest anti-TB activity (MIC = 1.6 µg/ml) which is similar to the standard drugs (Isoniazid, Ethambutol). anti-TB activity of H2L and H5L (MIC = 12.5 µg/ml and 25 µg/ml) increased on complexation with copper(II) (MIC = 1.6 µg/ml, 2 ; 12.5 µg/ml, 6). Experimental results are supported by molecular modeling studies, where a considerable intermolecular interaction of these compounds with the active site of amino acid of enoyl reductase from M. tuberculosis has been observed with minimum binding energy −6.2, −7.3, −7.7, −7.4, −7.2, −8.7 Kcal/mol for H1L , H2L , H3L , H4L , H5L , and H6L and −7.2, −9.4, −8.6, −9.3, −9.9, and −10.6 Kcal/mol for copper complexes 1, 2, 3, 4, 5 and 6 exhibited respectively. [ABSTRACT FROM AUTHOR]