Solvatochromism of Copper(II) Complexes Derived from Trifluoroacetylacetone and Dinitrogen Ligands

Abstract

Mixed ligand copper(II) complexes of the empirical formula [Cu (L)(TFAA)]X, where L represents 2,2´-bipyridine (Bipy), 1,10´-phenanthroline (Phen), or 4,7-diphenyl-1,10´- phenanthroline (Dphen), TFAA is 1,1,1-Trifluoro-2,4-pentanedione, and X is the counter ion (BF4 - or ClO4 -), were synthesized and characterized by spectroscopic, magnetic, molar conductance, elemental, and thermal analysis. Solvatochromic studies revealed that all the complexes showed bathochromic shifts. A square planar geometric structure is proposed for the perchlorate and tetrafluoroborate complexes. Spectral properties supported a square planar structure provided by the N2O2 chromophores. The mixed ligand copper complexes exhibited promising catalytic activity in the decomposition of hydrogen peroxide via the first-order reaction; the catalytic efficiency of perchlorate complexes was greater than that of tetrafluoroborate complexes. Potentiometric analyses of the aqueous mixed ligand copper complexes were carried out. The protonation constants of the free ligands and the stability constants of the complexes were determined using pH titration. The sequence of the stability of ternary complexes with respect to their ligands decreased in the order: Bipy˃ Phen˃ Dphen. The kinetic and thermodynamic parameters were calculated using the Coat- Redfern equation. The stability of the complexes was observed to be in line with the results obtained from the potentiometric analyses. The synthesized complexes were examined for their antimicrobial activity against two pathogenic bacteria (Staphylococcus aureus)as Grampositive bacteria and (Pseudomonas fluorescens) as Gram-negative bacteria and one type of fungus (Fusarium oxysporum). The results indicated that the complexes exhibited higher antimicrobial activity than the ligands. It was also observed that perchlorate complexes had higher activity than tetrafluoroborate, and the growth of inhibitory activity of the complexes followed the order Bipy˃ Phen˃ Dphen.