New vanadium complexes with 6,6-dimethy1-2,2:′6′,2-terpyridine in terms of structure and biological properties

Reactions of 6,6 ''-dimethy1-2,2':6',2 ''-terpyridine ligand L and VX3 (X = Cl, Br) in aerobic conditions result in formation of two new mononuclear coordination compounds: [VOLCl2] 1 and [VO2L](2)Br-2 center dot 3H(2)O(2), as revealed by means of single crystal X-ray analyses. The final form of vanadium complex in the solid state, either oxido (V(IV)) or dioxido (V(V)), was found to be contingent on the size of applied halide, as demonstrated by direct V-X interaction for small chloride (1) or ionic interaction for bulkier bromide (2). Depending on crystallization conditions, [VOLCl2] 1 forms polymorphic green or yellow crystals from MeCN or MeOH respectively. Compounds were characterized by elemental analysis, spectrometric (ESI-MS), electrochemical, (cyclic voltammetry) spectroscopic methods (UV-VIS, FTIR, EPR) and evaluated in terms of biological properties. Their cytotoxic activity was investigated in MIT assay and supported by absorption titration spectra suggesting the possible mechanism of action going through intercalative binding mode. On the basis of high binding constants K-bind = 4.4 x 10(5) M-1 (1) and K-bind = 1.0 X 10 M-1 (2) the relationship between structure of the complex and DNA interaction could be established, highlighting indirect impact of counterions on the final structure formation and thus biological activity. Flow cytometry analysis further confirmed the DNA binding based mechanism of action. What is more, compounds 1 and 2 are first reported cytotoxically active vanadium systems with 2,2':6',2 ''-terpyridine scaffolded family towards T47D cell line. (C) 2015 Elsevier Ltd. All rights reserved.