Luminescent tetranuclear zinc complexes constructed from a tetradentate Schiff-base ligand derived from 2,3-dihydroxybenzaldehyde

Four compounds, [Zn4L2(HL)2](ClO4)2 center dot 2H2O 1, [Zn4L2(HL)2](NO3)2 center dot 2H2O 2, [Zn4L2(CH3COO)4]center dot 2H2O 3, and [Zn4L2(C(CH3)3COO)4] 4, have been obtained using a Schiff-base proligand, H2L, which was obtained from the condensation of 2,3-dihydroxybenzaldehyde with 2-(aminoethyl)pyridine. Their crystal structures have been solved by single-crystal X-ray diffraction. Compounds 1 and 2 feature {Zn4O6} cores with alternate mono- and bis-phenoxido bridges. Compounds 3 and 4 are constructed from L2- and carboxylato ligands, resulting in neutral linear tetranuclear species. TD-DFT calculations have been carried out to rationalize the electronic spectra of our complexes. The experimental luminescence spectra of the four complexes have been investigated in DMF solutions.