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Two new metal-organic frameworks (MOFs), namely [Mn3(atpa) 3(dmf)2] and [Mn2(tpa)2(dmf) 2], were prepared in N,N-dimethylformamide (dmf) from manganese(II) nitrate and two dicarboxylic acid ligands, 2-aminoterephthalic acid (H 2atpa) and terephthalic acid (H2tpa). The molecular structures of these MOFs are compared to two related coordination polymers, namely [Mn3(atpa)2(Hatpa)2] and [Mn 3(tpa)3-(def)2], which were obtained in N,N-diethylformamide (def), to examine the effect of slight ligand or solvent changes on the framework architecture. The four Mn-based MOFs were used as effective Lewis catalysts for the cyanosilylation of acetaldehyde. The four heterogeneous catalytic systems can be re-used without any apparent loss of activity., Support from the Graduate Research School Combination “Catalysis” and the European Cooperation in the Field of Science and Technology (COST) program Action D35/0011, the Spanish Consejo Superior de Investigaciones Científicas (CSIC), as well as from the Spanish Ministerio de Ciencia y Innovación, for access to BM16 at the European synchrotron radiation facility (ESRF) through grant number 16-01-723, are acknowledged. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

A new iron(III) coordination compound exhibiting a two-step spin-transition behavior with a remarkably wide [HS-LS] plateau of about 45 K has been synthesized from a hydrazino Schiff-base ligand with an N,N,O donor set, namely 2-methoxy-6-(pyridine-2-ylhydrazonomethyl)phenol (Hmph). The single-crystal X-ray structure of the coordination compound {[Fe(mph)(2)](ClO(4))(MeOH)(0.5)(H(2)O)(0.5)}(2) (1) determined at 150 K reveals the presence of two slightly different iron(III) centers in pseudo-octahedral environments generated by two deprotonated tridentate mph ligands. The presence of hydrogen bonding interactions, instigated by the well-designed ligand, may justify the occurrence of the abrupt transitions. 1 has been characterized by temperature-dependent magnetic susceptibility measurements, EPR spectroscopy, differential scanning calorimetry, and (57)Fe Mossbauer spectroscopy, which all confirm the occurrence of a two-step transition. In addition, the iron(III) species in the high-spin state has been trapped and characterized by rapid cooling EPR studies.

The reactions of the ligand 2-(2-pyridyl)benzthiazole (pbt) with CuBr 2 and ZnCl 2 in acetonitrile produce the complexes [Cu(pbt)Br 2] ( 1) and [Zn(pbt)Cl 2] ( 3), respectively. When complex 1 is dissolved in DMF, complex 2 is obtained as light-green crystals. The reaction of pbt with CuBr 2 in DMF also yields the complex [Cu(pbt)Br 2(dmf)] ( 2) (dmf = dimethylformamide). Complexes 1- 3 were characterized by X-ray crystallography. Complexes 1 and 3 have distorted tetrahedral coordination environments, and complex 2 is constituted of two slightly different copper centers, both exhibiting distorted trigonal bipyramidal geometries. Complexes 1 and 2 cleave phiX174 phage DNA, both in the presence and the absence of reductant. The free ligand pbt does not show any DNA-cleaving abilities. The poor solubility of complex 3 makes it not applicable for biological tests. The occurrence of DNA breaks in the presence of various radical scavengers suggests that no diffusible radicals are involved in the DNA cleavage by complex 1, as none of the scavengers inhibit the cleavage reaction. The DNA-cleavage products are not religated with the enzyme T4 DNA ligase, which is an additional proof that the cleavage is nonhydrolytic. Most probably the cleaving reaction involves reactive oxygen species, which could not be trapped, leading to an oxidative mechanism. An easy oxidation of Cu (II)(pbt)Br 2 to Cu (III) in DMF and the reduction of the same to Cu (I), under similar electrochemical conditions may lead to the in situ activation of molecular oxygen, resulting in the formation of metal solvated nondiffusible radicals able to prompt the oxidative cleavage of DNA. Complex 1 and the pure ligand exhibit remarkable cytotoxic effects against the cancer cell lines L1210 and A2780 and also against the corresponding cisplatin-resistant mutants of these cell lines.