Imidazole and tetrazole derivatives are widely used as clinical drugs since they possess a variety of pharmaceutical function. Zinc and iron are essential trace elements of the human body, with less toxicity and good biocompatibility. In this paper, two new essential metal mononuclear complexes [M(H2tmidc)2(H2O)2]·2H2O (M = Zn (1), Fe (2)) were synthesized through the reaction of 2-((1H-tetrazol-1-yl)methylene)-1H-imidazole-4,5-dicarboxylic acid (H3tmidc) and ZnSO4·7H2O or FeSO4·7H2O. The crystal structures were determined by means of the X-ray single crystal diffraction technique. Results from fluorescence investigations show that both complexes could interact with BSA as well as HSA through the static quenching mechanism. van der Waals forces and hydrogen bonds play important roles in the interaction of complexes and BSA/HSA since both ΔH and ΔS values are negative. The results of molecular docking are consistent with those in experimental studies. Furthermore, the anticancer activity of H3tmidc and both complexes against Eca-109 were preliminarily evaluated and the results show that both complexes have better anticancer activity than the corresponding ligand H3tmidc.

C6H8CdN2O7, monoclinic, P21/c (no. 14), a = 7.3428(15) Å, b = 11.272(2) Å, c = 12.764(4) Å, β = 118.73(2)°, V = 926.4(4) Å3, Z = 4, Rgt(F) = 0.0261, wRref(F2) = 0.0609, T = 293(2) K.

C21H22N12O7Hg, monoclinic, P2/n (no. 13), a = 13.655(3) Å, b = 8.7038(17) Å, c = 23.260(5) Å, β = 102.51(3)°, V = 2698.8(10) Å3, Z = 4, Rgt(F) = 0.0446, wRref(F2) = 0.0875, T = 293(2) K.