Thermal and Spectral Studies of Transition Metal Complexes of 2-Bromo-3-Hydroxynaphthalene-1,4-Dione: Evaluation of Antibacterial Activity Against Six Bacterial Strains

Umar Ali Dar,1

Sunita Salunke-Gawali,1*Email

Dnyaneshawar Shinde,2

Sujit Bhand1

Surekha Satpute3

1Department of Chemistry, Savitribai Phule, Pune University, Pune- 411007, Maharashtra State, India

2Department of Chemistry, P.D.E.A’s, Prof Ramkrishna More College, Akurdi, Pune 411044, Maharashtra, India

3Department of Microbiology, Savitribai Phule Pune University, Pune 411007, Maharashtra, India

E-mail: sunita.salunke@unipune.ac.in (Sunita Salunke-Gawali)

Abstract

Synthesis, thermal, spectral, electrochemical, and magnetic properties of transition metal complexes of 2-bromo-3-hydroxynaphthalene-1,4-dione(abbreviated as L) are discussed. The complexes viz, [Zn(L)2(H2O)2]; ZnL, [Cu(L)2(H2O)2]; CuL, [Ni(L)2(H2O)2]; NiL, [Co(L)2(H2O)2]; CoL, are resulted from the reactions of L with respective metal chlorides in methanol. The carbonyl frequency (1633 cm-1) of the ligand remains the same in ZnL, whereas it is observed at a higher wavenumber (17 cm-1) in CuL and lower wavenumber (3 cm-1) in NiL and CoL. The thermal decomposition of the complexes was studied by thermogravimetry.  Powder X-ray diffraction studies further analyzed the respective metal oxide formed in TG studies. Redox potentials of all complexes are determined by cyclic voltammetry studies. It is difficult to reduce or oxidize the ligand after complexation. The frozen solution (DMSO) spectrum (133 K) of CuL shows four 63Cu hyperfine lines in the gregion with A║ = ~155 G in CuL. The ligand, as well as all-metal complexes, showed considerable antibacterial activity against six strains viz. Staphylococcus aureus NCIM 2079, Bacillus subtilis NCIM 2423, Escherichia coli NCIM 2065, Proteus Vulgaris NCIM 2027, Pseudomonas aeruginosa MTCC 2297, P. putida MTCC 2463.

Thermal and Spectral Studies of Transition Metal Complexes of 2-Bromo-3-Hydroxynaphthalene-1,4-Dione: Evaluation of Antibacterial Activity Against Six Bacterial Strains