Bis-chelated-(3-methoxy-2-oxo-benzaldehyde)-copper(II) complex: Synthesis, crystal structure, fluorescence property, DFT calculation, and catecholase activity

Reaction of Cu(NO3)(2)center dot 3H(2)O and 2-hydroxy-3-methoxybenzaldehyde (HL) in methanolic medium results [CuL2]center dot 4H(2)O (1) [L- = 3-methoxy-2-oxo-benzaldehyde]. The complex was characterized by elemental analysis, IR, single crystal X-ray structure determination and DFT calculation. The X-ray single crystal structure determination reveals that 1 is a discrete mononuclear four coordinated complex with the metal in square planar coordination geometry and four lattice water molecules. The complex form dimer around the center of symmetry with short Cu center dot center dot center dot O interaction and exhibits intense fluorescence (lambda(ex) = 270 nm, lambda(em) = 311, 328, 355 and 367 nm) in methanolic solution at room temperature with a fluorescence quantum yield Phi(s) = 3.5. The complex 1 was tested with several aromatic compounds such as m-toluidine, aniline, nitrobenzene and o-nitrotoluene, and the results show that a pronounced fluorescence quenching and enhancement is observed in the presence of nitrobenzene and m-toluidine, respectively. Catecholase activity of 1 has been investigated in methanol medium by UV-Vis spectrophotometric study using 3,5-di-tert-butylcatechol (3,5-DTBC) as model substrate reveals that 1 is active for catalyzing aerobic oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ). The optimized geometry from density functional theory (DFT) study shows a good agreement with X-ray structural data. The electronic and IR spectrum of this compound is compared with result obtained by employing DFT and time dependent density functional theory (TD-DFT) calculation. (C) 2014 Elsevier Ltd. All rights reserved.