Hydrolysis theory for cisplatin and its analogues based on density functional studies.

Hydrolysis of cisplatin, the most widely used anticancer drug in the world, is believed to be the key activation step before the drug reaching its intracellular target DNA. To obtain an accurate hydrolysis theory for this important class of square-planar Pt(II) complexes, three typical reactions, i.e., the first and second hydrolyses of cisplatin and the hydrolysis of [Pt(dien)Cl](+) (dien = diethylenetriamine), were studied at the experimental temperature with the solvent effect using mPW1PW91/SDD from a comprehensive methodological study on the Hartree-Fock (HF) ab initio method, electron correlation methods, pure density functional theory (DFT) methods, and hybrid HF-DFT methods with several basis sets. The true five stationary states in the second-order nucleophilic substitution (S(N)2) pathway for the hydrolysis process, namely, reactant (R) --> intermediate 1 (I1) --> TS --> intermediate 2 (I2) --> product (P) were obtained and characterized theoretically for the first time. The most remarkable structural variations and the associated atomic charge variations in the hydrolysis process were found to occur in the equatorial plane of the five-coordinate trigonal-bipyramidal (TBP)-like structures of I1, TS, and I2. The reaction with the TS structure of smaller L-M-E angle and more lengthened M-L and M-E bonds was found to have a smaller Gibbs free energy change and accordingly the better hydrolysis yield. It is found that the sum of the three concentric angles in the TBP's equator is near 360 degrees in I1 and I2 and is almost 360 degrees in TS in each reaction. The associated energy profiles again demonstrated a typical S(N)2 reaction curve. The computed forward and backward reaction enthalpy (Delta H(++)) and reaction entropy (Delta S(++)) in the rate-determining step I1 --> TS --> I2 are in good agreement with the experiments. Natural bonding orbital population analysis shows that the charge-separating extent follows the same order of Delta G in studied reactions. Comparing with the computational results of gas-phase reactions, it can be concluded that the solvent effect should be considered to obtain an accurate hydrolysis picture. The most affected structural parameters after solvation are related to the equatorial plane of the TBP-like geometry. The results provide theoretical guidance on detailed understanding on the mechanism of the hydrolysis of cisplatin, which could be useful in the design of novel Pt-based anticancer agents.

A mixed-valence manganese(III)-manganese(IV) di-mu-oxo complex, [(cyclam)MnO]2(ClO4)2(NO3).

The title dinuclear di-mu-oxo-bis[(1,4,8,11-tetraazacyclotetradecane-kappa(4)N)manganese(III,IV)] diperchlorate nitrate complex, [Mn(2)O(2)(C(10)H(24)N(4))(2)](ClO(4))(2)(NO(3)) or [(cyclam)MnO](2)(ClO(4))(2)(NO(3)), was self-assembled by the reaction of Mn(2+) with 1,4,8,11-tetraazacyclotetradecane in aqueous media. The structure of this compound consists of a centrosymmetric binuclear [(cyclam)MnO](3+) unit, two perchlorate anions and one nitrate anion. While the low-temperature electron paramagnetic resonance spectra show a typical 16-line signal for a di-mu-oxo Mn(III)/Mn(IV) dimer, the magnetic susceptibility studies also confirm a characteristic antiferromagnetic coupling between the electronic spins of the Mn(IV) and Mn(III) ions.

Terephthalaldehyde bis(thiosemicarbazone) bis(dimethylformamide) solvate.

The thiosemicarbazone molecule in C(10)H(12)N(6)S(2).2C(3)H(7)NO has -1 symmetry. The thiosemicarbazone moiety and the benzene ring are essentially coplanar, with mean and maximum deviations of 0.03 and 0. 11 A, respectively. The dimethylformamide molecules bridge the thiosemicarbazone moieties, forming two-dimensional sheets through N-H.O hydrogen bonds.

Tetraaquabis[2-(4-pyridyl)ethanesulfonato-N]zinc(II).

The title compound, [Zn(C(7)H(8)NO(3)S)(2)(H(2)O)(4)], has an octahedral coordination around the central Zn atom composed of two axial N atoms from the pyridine ligands and four equatorial O atoms of water molecules, forming a monomeric centrosymmetric complex. The two Zn-N bond distances are 2.102 (3) A, while the four Zn-O bond distances range from 2.114 (2) to 2.167 (2) A. Packing is determined by hydrogen bonds formed by the water molecules. The sulfonate group does not take part in coordination to the Zn atom.

Pyridine-4-carbaldehyde azine.

In the crystal structure of the title compound, C(12)H(10)N(4), the pyridine ring makes a dihedral angle of 1.12 (9) degrees with the mean plane of the complete almost planar and crystallographically centrosymmetric molecule. There are stacks of parallel molecules along the a-axis direction, with alternate stacks having a herring-bone arrangement relative to each other and an interplanar spacing of 3.551 A.

A convenient route to synthesize the fully conjugated bimetallic complex (Bu4N)2[tto[Ni(dmit)2]] (tto = tetrathiooxalate, C2S4(2-), and dmit = 1,3-dithiole-2-thione-4,5-dithiolate, C3S5(2-) and the crystal structure of a new crystal form.

A novel route for the conversion of (Bu4N)2[Ni(dmit)2] to (Bu4N)2[tto[Ni(dmit)2]] is reported here. This provides a much more efficient way of synthesizing (Bu4N)2[tto[Ni(dmit)2]] than the literature method. During the process, the conversion of dmit2- to tto2- was realized for the first time. This new synthesis should facilitate further research on the conducting bimetallic complexes [C]x[tto[Ni(dmit)2]]. In addition, a new crystal form of (Bu4N)2[tto[Ni(dmit)2]]. In addition, a new crystal form of (Bu4N)2[tto[Ni(dmit)2]] was determined by X-ray crystallographic analysis.