Transition metal complexes of buparvaquone as potent new antimalarial agents 1.: Synthesis, X-ray crystal-structures, electrochemistry and antimalarial activity against Plasmodium falciparum

New Cu(II), N(II), Co(II), Fe(II), and Mn(II) metal complexes of buparvaquone {3-trans(4-tert.-butylcyclohexyl)methyl-2-hydroxy1,4-naphthoquione) (L1H) have been synthesized and characterized using IR, electron paramagnetic resonance (EPR) spectroscopy, microanalytical methods and single crystal X-ray diffraction methods. The single crystal structures were determined for ligand L1H [space group P-1 with a =6.2072(14) Angstrom, b= 10.379 (2) Angstrom, c= 13.840 (3) Angstrom, V = 878.7(3) Angstrom(3), Z = 2, D-calcd. = 1.234 mg/m(3)] and copper complex (Cu(L1)(2)(C2H5OH)(2)] C1 [space group I2la with a=17.149(14) Angstrom, b = 9.4492(8) Angstrom, c = 26.946(3) Angstrom, V = 4335.3(7)Angstrom(3), Z = 4, D-calcd. = 1.233 mg/m(3)]. All the metal complexes along with the parent ligand have been studied for their electrochemical properties using cyclic voltammetric techniques. The compounds were tested for their in vitro antimalarial activity against Plasmodium falciparum strains. A correlation between the antimalarial activity and the redox property of these complexes is presented. The ocpper complex C1 exhibits significantly higher growth inhibitory activity both in vitro and in vivo than the parent ligand. (C) 2003 Elsevier Science Inc. All rights reserved.