NMR and fluorescence spectral studies on bisdithiocarbamates of divalent Zn,Cd and their nitrogenous adducts: Single crystal X-ray structure of (1,10-phenanthroline)bis(4-methylpiperazinecarbodithioato) zinc(II) |
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Authors: | Balasubramaniyam Arul Prakasam Kuppukkannu Ramalingam Gabriele Bocelli Andrea Cantoni |
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Institution: | 1. Department of Chemistry, Annamalai University, Annamalainagar, Tamil Nadu 608 002, India;2. IMEM, CNR, Parma, Italy |
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Abstract: | The current paper describes the synthesis and characterization of the following adducts: Zn(4-mpzdtc)2(1,10-phen)] · H2O (1), Zn(4-mpzdtc)2(2,2′-bipy)] (2), Cd(4-mpzdtc)2(1,10-phen)] (3), Cd(4-mpzdtc)2(2,2′-bipy)] (4), Zn(padtc)2(1,10-phen)] (5) and Cd(padtc)2(1,10-phen)] (6) (where, 4-mpzdtc = 4-methylpiperazinecarbodithioate anion, padtc = N,N′-(iminodiethylene)bisphthalimide dithiocarbamate anion, 1,10-phen = 1,10-phenanthroline and 2,2′-bipy = 2,2′-bipyridine). All the synthesized complexes were characterized by UV–Vis, IR, NMR, (1H and 13C) and fluorescence spectra. A single crystal X-ray structural analysis was carried out for complex 1. IR spectra of the complexes show the contribution of the thioureide form to the structures. The observed deshielding of the α-protons for 1–6 in the 1H NMR spectra is attributed to the drift of electrons from the nitrogen of the NR2 groups, forcing a high electron density towards sulfur via the thioureide π-system. In the 13C NMR spectra, the most important thioureide (N13CS2) carbon signals are observed in the region 206–208 ppm. Fluorescence spectra of complexes 5 and 6 show intense fluorescence due to the presence of rigid conjugated systems such as phthalimide and 1,10-phenanthroline. The observed fluorescence maxima for complexes with a MS4N2 chromophore in the visible region are assigned to the metal-to-ligand charge transfer (MLCT) processes. Single crystal X-ray structural analysis of 1 showed that the zinc atom is in a distorted octahedral environment with a MS4N2 chromophore. VBS equivalent to 1.81 supports the correctness of the determined structure. The piperazine ring in the dithiocarbamate fragment is in the normal chair conformation. |
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Keywords: | Dithiocarbamate Thioureide NMR Fluorescence Single crystal X-ray structure |
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