A novel proton transfer compound (HABT)(+)(Hdipic)(-) (1) obtained from ABT and H(2)dipic and its metal complexes (2-5) have been prepared and characterized by spectroscopic techniques. Single crystal X-ray diffraction method has also been applied to 2 and 5. While complex 2 has a distorted octahedral conformation, 5 exhibits a distorted square pyramidal structure. The structures of 3 and 4 might be proposed as octahedral according to experimental data. All compounds were also evaluated for their in vitro inhibition effects on hCA I and II for their hydratase and esterase activities. Although there is no inhibition for hydratase activities, all compounds have inhibited the esterase activities of hCA I and II. The comparison of the inhibition studies of 1-5 to parent compounds indicates that 1-5 have superior inhibitory effects. The inhibition effects of 2-5 are also compared to inhibitory properties of the metal complexes of ABT and H(2)dipic, revealing an improved transfection profile.