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

Abstract

Reaction of Cu(NO3)2·3H2O and 2-hydroxy-3-methoxybenzaldehyde (HL) in methanolic medium results [CuL2]·4H2O (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⋯O interaction and exhibits intense fluorescence (λex=270nm, λem=311, 328, 355 and 367nm) in methanolic solution at room temperature with a fluorescence quantum yield Φs=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.