B. Sarkar, Kishalay Bhar, S. Kundu
Nov 12, 2009
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Influential Citations
15
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Journal
Journal of Molecular Structure
Abstract
Abstract Two hexacoordinated mononuclear cobalt(II)thiocyanate complexes of general formula [Co(LL) 2 (NCS) 2 ]. n H 2 O [LL = 2,2′-dipyridylamine (dpa), n = 1, 1 ; LL = N -((pyridin-2-yl)benzylidene)benzylamine (pbba), n = 0, 2 ] have been prepared and characterized using microanalytical, spectroscopic and other physicochemical results. The compounds are non-electrolytes and behave as three-electron paramagnets. Structures of 1 and 2 are solved by X-ray diffraction measurements. Structural analyses show that each metal center in 1 and 2 adopts a distorted octahedral geometry with a CoN 6 chromophore ligated through four N atoms of two bidentate LL units; the hexacoordination is completed by two N atoms of terminal thiocyanates in mutual cis orientation. The mononuclear units in 1 are engaged in weak intermolecular N–H…S and C–H…S hydrogen bonds to give a 2D sheet structure, which is further stabilized by π…π interactions among the pyridine rings of dpa units. In the long-range form, two mononuclear units of 2 are locked by weak doubly C–H…S hydrogen bonds producing a dimeric unit, which packs through C–H…π interaction leading to a 2D continuum. In MeCN solutions, the compounds show a nearly reversible one-electron oxidative response corresponding to cobalt(III)–cobalt(II) couple. The complexes display intraligand 1 (π–π∗) fluorescence at room temperature and intraligand 3 (π–π∗) phosphorescence in glassy solutions (DMF at 77 K).