Mononuclear five-coordinate cobalt(II) complexes with N₄-coordinate pyrazole based ligand and pseudohalogens: synthesis, structures, DNA and protein binding study

Abstract

A series of mononuclear five-coordinate cobalt(II) complexes, [Co(dbdmp)(X)]Y, where dbdmp = N,N-diethyl-N′,N′-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine, X = /NCO⁻/NCS⁻ and Y = //, have been synthesized and characterized by microanalyses and spectroscopic techniques. Crystal structures of [Co(N₃)(dbdmp)]PF₆ (1), [Co(N₃)(dbdmp)]ClO₄ (3), [Co(NCO)(dbdmp)]PF₆ (4), [Co(NCO)(dbdmp)]ClO₄ (6), and [Co(NCS)(dbdmp)]ClO₄ (9) have been solved by single-crystal X-ray diffraction studies and showed that all the complexes have distorted trigonal bipyramidal geometry; counter anion containing complexes [Co(N₃)(dbdmp)]PF₆ and [Co(NCO)(dbdmp)]PF₆ have chiral space groups. The binding ability of synthesized complexes with CT-DNA and bovine serum albumin (BSA) has been studied by spectroscopic methods and viscosity measurements. The experimental results of absorption titration of cobalt(II) complexes with CT-DNA indicate that the complexes have ability to form adducts and they can stabilize the DNA helix. The cobalt(II) complexes exhibit good binding propensity to BSA protein.

A series of five-coordinate cobalt(II) complexes, [Co(dbdmp)(X)]Y, where dbdmp = N,N-diethyl-N′,N′-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine, X = /NCO⁻/NCS⁻ and Y = //, have been synthesized and characterized. All the complexes have distorted trigonal bipyramidal geometry. DNA and protein binding of the complexes were investigated by absorption and fluorescence spectroscopy studies.

Keywords:

• Tetradentate ligand
• Cobalt(II)
• Pseudohalides
• Structures
• DNA
• BSA binding

Acknowledgments

Financial support from UGC in the form of major research project (F.No. 39-720/2010(SR)) is gratefully acknowledged. A. Solanki thanks UGC for BSR fellowship. We thank Dr P. Paul and Dr E. Suresh of Central Salt and Marine Chemicals Research Institute, Bhavnagar, for spectroscopy and X-ray studies, IIT Roorkey and DST PURSE program, Department of Chemistry, the M.S. University of Baroda, Vadodara, for single-crystal X-ray diffraction study. We thank Mr Hemant Mande of M.S. University of Baroda for helping in crystallography. We also thank one of the reviewers for suggestions on crystallography.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed http://dx.doi.org/10.1080/00958972.2015.1085515.