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A Deep Insight into the Photoluminescence Properties of Schiff Base CdII and ZnII Complexes

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journal contribution
posted on 23.10.2017, 17:51 by Ishani Majumder, Prateeti Chakraborty, Sanchari Dasgupta, Chiara Massera, Daniel Escudero, Debasis Das
A tridentate N,N,O donor ligand 2,4-dichloro-2-[(2-piperazine-4-yl-ethylimino)-methyl]-phenol (HL) was designed, and eight new ZnII and CdII complexes, namely, [Zn­(LH)­(SCN)2] (1), [Zn­(LH)­(N3)2] (2), [Zn­(LH)­(NO2)2] (3), [Zn­(LH)­(dca)­(OAc)] (4), [Cd2(LH)2­(SCN)4] (5), [Cd­(LH)­(N3)2] (6), [Cd­(LH)­(NO2)2] (7), and [Cd­(LH)­(dca)­(OAc)] (8) [where dca = dicyanamide anion] were synthesized. Five of them (1, 2, 4, 5, 7) were structurally characterized through single-crystal X-ray diffraction analysis. H-Bonding interactions are found to be the major stabilizing factor for crystallization in the solid state. Experimental and computational studies were performed in cooperation to provide a rationalization of the photoluminescence properties of those complexes. The quantum yields are anion-dependent, with enhanced efficiencies in the following order: LH < Cd-SCN­(5) < Cd-dca­(8) < Cd–N3(6) < Cd-NO2(7) < Zn-dca­(4) < Zn–N3(2) < ZnNO2(3) < ZnSCN­(1). By using quantum chemical calculations we rationalized the above trends. Moreover, the diverse lifetimes observed for those eight complexes were also quantitatively explained by considering the subtle competition between different photo-deactivation pathways.