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 = Image omitted./NCO super(-)/NCS super(-) and Y = Image omitted./Image omitted./Image omitted., have been synthesized and characterized by microanalyses and spectroscopic techniques. Crystal structures of Co(N sub(3))(dbdmp)PF sub(6) (1), Co(N sub(3))(dbdmp)ClO sub(4) (3), Co(NCO)(dbdmp)PF sub(6) (4), Co(NCO)(dbdmp)ClO sub(4) (6), and Co(NCS)(dbdmp)ClO sub(4) (9) have been solved by single-crystal X-ray diffraction studies and showed that all the complexes have distorted trigonal bipyramidal geometry; Image omitted. counter anion containing complexes Co(N sub(3))(dbdmp)PF sub(6) and Co(NCO)(dbdmp)PF sub(6) 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.