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Two different effective-core-potential methodologies, augmented with extra polarization functions are used at the MP2 level of theory to investigate the isomers of I-containing peroxides of the type XOOI, XIO2, IXO2, XOIO and IOXO (X=Cl, Br, I). The reliability of the results is checked against the all-electron calculations of Misra and Marshall [J. Phys. Chem. A, 102 (1998) 9056] for the IOOI family. Contrary to what has been well established for the chlorine and bromine analogs, the present study confirms the interesting observation that the I-containing peroxide isomers, XOOI, are not the most stable structures in each subfamily. [Copyright &y& Elsevier]

Two different effective-core-potential methodologies, augmented by extra polarization functions were used to investigate a number of iodine triatomics of the type XOI, XIO and IXO (X = Cl, Br, I). The procedures were tested first on the well-studied ClOCl, BrOBr, ClOBr and IOI systems and they were shown to reproduce the full-electron calculation results with reasonable consistency. The results exhibit the same tendencies as the corresponding Cl and Br analogues and produce the greater stability for the isomer with the least electronegative atom in the middle. [Copyright &y& Elsevier]

Abstract: Ab initio calculations have been performed for both H-atom and Cl-atom abstraction reactions by the hydroxyl radical. Geometry optimization and vibrational frequencies analysis were performed for reactants, transition state and products at the MP2(full)/cc-pVTZ level of theory. On the basis of the ab initio data, the rate constants have been deduced over a wide temperature range, 200–2000 K, using conventional transition state theory, including Wigner tunneling correction and the hindered rotor approximation. Calculated transition state rate constants with Wigner tunneling correction are in good agreement with experimental results. The tunneling contribution becomes important at ambient temperatures, resulting in the exhibited non-Arrhenius behavior of the rate constant. [Copyright &y& Elsevier]

The non-coordinative interactions between the compounds [(η 6 -cym)Ru(pqx)Cl]Cl, ( 1 )Cl, [(η 6 -cym)Ru(pbqx)Cl]Cl, ( 2 )Cl (cym is 1-methyl-4-(1-methylethyl)benzene, pqx is 2-(2′-pyridyl)quinoxaline and pbqx is 2-(2′-pyridyl)benzo[ g ]quinoxaline), with the self-complementary oligonucleotide duplex d(5′-CGCGCG-3′) 2 in 100 mM phosphates buffer and 50 mM NaCl, were studied by means of NMR spectroscopic techniques. The compounds ( 1 )Cl and ( 2 )Cl were found to be stable in aqueous media without being hydrolyzed, preserving their saturated coordination sphere (η 6 -arene-2N-Cl). Based on NMR techniques it was found that both ( 1 ) and ( 2 ) interact with the hexamer with the outer side of the chelating ligand L, causing elongation or disruption of the oligonucleotide Watson-Crick (W-C) hydrogen bonds. Since both compounds are highly cytotoxic, it can be concluded that their cytotoxic activity could be owed to this type of interactions, or non-coordinative interactions with other biomolecules. [ABSTRACT FROM AUTHOR]

Abstract: In this work, magnetometry and EPR spectroscopy studies on the binuclear Mn(II) complex [Mn2{(OPPh2)2N}4] (1) established antiferromagnetic interactions between the two S =5/2 Mn(II) centers being at 3.378Å from each other. The magnitude of the J AB coupling constant, in the framework of the formalism, was determined to be −4.5±0.5cm−1, by the temperature dependence of the magnetic susceptibility of 1. This value is comparable with the one of the previously studied [Mn2{(OPPh2)[OP(OEt)2]N}4(H2O)2] complex (−3.5cm−1), which bears similar type of ligands. The antiferromagnetic nature of the coupling within the binuclear Mn2O4 core of 1 was unequivocally confirmed also by EPR studies on frozen CH2Cl2 solutions at various temperatures. Density functional broken-symmetry calculations confirmed the above experimental findings and provided J AB values in close agreement with the experiment. Comparisons with literature binuclear Co(II) or Mn(II) complexes were made. [Copyright &y& Elsevier]

Abstract: The Zero Field Splitting (ZFS) parameters of the mononuclear Mn(II) (S =5/2) compound [Mn(Ac4Ph)2], where HAc4Ph stands for 4-phenyl-2-acetylpyridine thiosemicarbazone, are determined by dual mode X-band and high field/high frequency electron paramagnetic resonance spectroscopy. Density functional theory (DFT) calculations reproduce both the sign and absolute value of the axial parameter D of the ZFS tensor, whose distribution is quantitatively correlated to distribution on geometrical elements of the complex. [Copyright &y& Elsevier]

Abstract: Ab initio calculations were conducted for both reaction pathways of the CH3Br and OH system. Geometry optimization and vibrational frequencies analysis were performed for reactants, pre-reaction complex, transition states, post-reaction complex and products at the MP2(full)/6-311+G(d,p), MP2(full)/6-311+G(3df,2pd) and MP2(full)/cc-pVTZ levels of theory. Energetic results were further refined by CCSD(T,full) calculations, using optimized geometric parameters of the MP2(full)/cc-pVTZ level, i.e., CCSD(T,full)/cc-pVTZ//MP2(full)/cc-pVTZ. Based on MP2(full)/cc-pVTZ and CCSD(T,full)/cc-pVTZ//MP2(full)/cc-pVTZ data, rate constants were deduced in the 200–2000K temperature range, using conventional transition state theory and Wigner tunneling correction. Calculated rate constants, including tunneling corrections, were found to be in excellent agreement with experimental results. [Copyright &y& Elsevier]

Abstract: The C-terminal blocked tetrapeptides SHHK– and SAHK–, which represent the fragments produced from the hydrolysis of the hexapeptides’ –TASHHK–, –TESHHK–, and –TESAHK– complexes with Ni(II), were synthesized and their interactions with Ni(II) ions were studied potentiometrically and spectroscopically. Both tetrapeptides interact strongly with Ni(II) ions leading to square-planar complexes with 4N {NH2,2N−,Nim} coordination. The stability of the Ni–SHHK– complex is about 2 orders of magnitude higher than the Ni–SAHK– complex. Spectroscopic evidence and theoretical predictions suggest the positioning of the free imidazole ring, in the Ni–SHHK– complex, above the coordination plane, explaining the extra stability of the complex. [Copyright &y& Elsevier]