NISCAIR Online Periodicals Repository Collection: IJC-A Vol.50A(09-10) [September-October 2011]

Zinc and cadmium complexes of a Schiff base ligand derived from diaminomaleonitrile and salicylaldehyde: Syntheses, characterization, photoluminescence properties and DFT study

Mon, 29 Aug 2011 22:58:59 GMT

Title: Zinc and cadmium complexes of a Schiff base ligand derived from diaminomaleonitrile and salicylaldehyde: Syntheses, characterization, photoluminescence properties and DFT study

Authors: Guha, Averi; Adhikary, Jaydeep; Mondal, Tapan Kumar; Das, Debasis

Abstract: Zn(II) and Cd(II) complexes of a 1+1 condensed Schiff base derived from salicylaldehyde and diaminomaleonitrile has been synthesized and characterized. Electronic and photoluminescence spectral properties of the complexes as well as the free ligand have been investigated and a thorough DFT study has been performed to rationalize the spectral behavior.

Page(s): 1463-1468

Density functional theory calculations on biological S-transfer: Insight into the mechanism of rhodanese

Mon, 29 Aug 2011 22:58:59 GMT

Title: Density functional theory calculations on biological S-transfer: Insight into the mechanism of rhodanese

Authors: Dey, Subal; Dey, Abhishek

Abstract: Biological sulfur transfer (S-transfer) is a key step in the synthesis of metabolites, CN^- detoxification and assembly of iron-sulfur clusters. Computational results addressing the thermodynamics of the S-transfer reactions from thiosulfate (natural S-donor) to HCN and thiol are presented. These calculations indicate that S-transfer from thiosulfate to HCN and thiol is possible only in the anionic forms of these species. However these species have pK_a values significantly higher than physiological pH value (i.e., they are protonated in physiological pH and incapable of S-transfer). In the rhodanese active site, basic residues are present to deprotonate the catalytic cysteine group which accepts the S-atom from thiosulfate. The resultant perthiol species transfer S-atom to CN^- in a synchronous S-atom and H⁺ transfer step facilitated by the two arginine residues present in the rhodanese active site. Based on these calculations, a mechanism is proposed for the rhodanese catalyzed CN^- detoxification pathway.

Page(s): 1457-1462

Ferromagnetic vs antiferromagnetic coupling in structurally analogous binuclear complexes based on salen type ligand

Mon, 29 Aug 2011 22:58:59 GMT

Title: Ferromagnetic vs antiferromagnetic coupling in structurally analogous binuclear complexes based on salen type ligand

Authors: Pandey, Rampal; Ribas, Joan; Corbella, Montserrat; Pandey, Daya Shankar

Abstract: Syntheses of the dinuclear complexes [Co(C₂₃H₁₈N₂O₂)]₂(1), [Cu(C₂₃H₁₈N₂O₂)]₂^.H₂O (2), [Ni(C₂₃H₁₈N₂O₂)]₂ (3), [Zn(C₂₃H₁₈N₂O₂)]₂ (4) and [Cd(C₂₃H₁₈N₂O₂)]₂ (5) containing the Schiff base ligand N,N′-bis(2-hydroxybenzilidene)-2,4,6-trimethylbenzene-1,3-diamine have been described. The complexes under investigation have been characterized by elemental analyses, IR, NMR(¹H, ¹³C), electronic absorption, emission and EPR spectral studies. The structure of (1) has been determined by X-ray single crystal analyses. Variable temperature magnetic susceptibility measurements on (1) and (2) reveal that the former displays antiferromagnetic coupling (J = -0.21 ± 0.1 cm^-1), while the latter exhibits ferromagnetic coupling (J = + 1.23 ± 0.1 cm^-1).

Page(s): 1450-1456

Trans-dichlorobis(N-p-tolylpyridin-2-amine)palladium(II): Synthesis, structure, fluorescence features and DNA binding

Mon, 29 Aug 2011 22:58:59 GMT

Title: Trans-dichlorobis(N-p-tolylpyridin-2-amine)palladium(II): Synthesis, structure, fluorescence features and DNA binding

Authors: Kundu, Suman; Maity, Suvendu; Bhadra, Ranjan; Ghosh, Prasanta

Abstract: Reaction of N-p-tolylpyridin-2-amine (L^Me) with H₂PdCl₄ in boiling acetonitrile and ethanol solvents mixture (1:1) affords trans-Pd(L^Me)₂Cl₂ (1) in high yield. (1) is substantiated by spectral data, single crystal X-ray structure determination, etc. Both (L^Me) and (1) absorb strongly in the UV region ( _max, nm (, 10⁴M^–1cm^–1), DCM: (L^Me), 310 (1.97), 276 (4.95); (1), 320 (4.36), 270 (6.98). (L^Me) is brightly fluorescent due to intra-ligand charge transfer singlet excited state ( _ex = 332 nm, _em = 400 nm; = 0.621 measured with respect to anthracene) as elucidated by DFT and TD DFT calculations. In (1), the luminescence of (L^Me) is significantly (~ 97 %) quenched ( = 0.016) and the fluorescence parameters are red shifted ( _ex = 378 nm, _em = 430 nm). Binding of (1) to CT-DNA has been investigated by UV-vis spectrum confirming a significant interaction with the intrinsic binding constant as K_b= ~ 9.78 X 10⁵ M^-1 and CT-DNA-ethidium bromide fluorescence quenching experiment giving the apparent binding constant as K_app= 9.02 X 10⁵ M ^–1.

Page(s): 1443-1449