Copper(II) and cobalt(III) pyridoxal thiosemicarbazone complexes with nitroprusside as counterion: syntheses, electronic properties, and antileukemic activity.

In this paper the syntheses of new pyridoxal thiosemicarbazone copper(II) and cobalt(III) complexes with nitroprusside as a counterion and tests on the antileukemic activity of three of these complexes toward human cell lines U937 and CEM are reported. Nitroprusside was chosen in order to test if its ability to release NO can increase the biological activity already shown by these complexes. The compounds were characterized by spectroscopic and magnetic methods and by single-crystal X-ray diffraction.

Selective Metal-Assisted Oxidative Cleavage of a C-N Bond: Synthesis and Characterization of the Mononuclear Iron(III) [Fe(BPG)Cl(2)] Complex and Its Two [Fe(BPA)Cl(3)] and [Fe(BPE)Cl(3)] Derivatives.

A new example of a site-selective metal-assisted oxidative cleavage of a C-N bond is reported. This phenomenon occurs in the nitrogen-centered tetradentate tripodal BPG ligand (BPG = (bis(2-pyridylmethyl)amino)acetate), which combines one carboxylate and two pyridines as pendant groups, when coordinated to iron(III). The corresponding iron(III) [Fe(BPG)Cl(2)] complex (1) is transformed to the iron(III) [Fe(BPA)Cl(3)] complex (2) with the tridentate BPA ligand (BPA = bis(2-pyridylmethyl)amine) retaining only two pyridine pendant groups, while the initial BPG carboxylate group is transformed to glyoxylic acid. The [Fe(BPA)Cl(3)] complex (2) has been fully characterized as well as another, [Fe(BPE)Cl(3)] (3), formed with the tridentate BPE ligand (BPE = methyl (bis(2-pyridylmethyl)amino)acetate) which, in addition to two pyridines, presents an ester group. The crystal structures of these two complexes have been resolved. The asymmetric unit of complex 2 has been characterized by two mononuclear neutral molecules linked by two hydrogen bonds. (Crystal data for 2: orthorhombic, Pna2(1), a = 15.603(8) Å, b = 8.485(4) Å, c = 22.752(11) Å, alpha = beta = gamma = 90 degrees, V = 3012(3) Å(3), Z = 8, R = 0.0582 [2813 reflections with I > 2sigma(I)], and R(w) = 0.1430.) Complex 3 is symmetric with the iron center, the amine nitrogen, one choride and the three atoms of the carboxylate group in special positions in the mirror plane. (Crystal data for 3: orthorhombic, Pmn2(1), a = 10.418(4) Å, b = 12.952(5) Å, c = 7.353(3) Å, alpha = beta = gamma = 90 degrees, V = 992.2(7) Å(3), Z = 2, R = 0.0500 [513 reflections with I > 2sigma(I)], and R(w) = 0.1231.) Redox potentials corroborate the structural features (E degrees = -38 mV for 1, -19 mV for 2, and +145 mV for 3 vs SCE in acetonitrile). Preliminary studies of the [Fe(BPG)Cl(2)] complex have shown that it reacts in its reduced form with dioxygen.