Crystal structure of bis-(1,10-phenanthroline-κ2N,N')(1,3-thia-zole-2-thiol-ato-κ2S2,N)nickel(II) hexa-fluorido-phosphate 1,4-dioxane sesquisolvate.

The title salt, [Ni(C3H2NS2)(C12H8N2)2]PF6·1.5C4H8O2, was the unexpected product on making an attempt to prepare an [Ni(2-mercapto-thia-zol-ate)(1,10-phenanthroline)]+ complex by reaction of [NiCl2(1,10-phen-an-throline)] with 2-mercapto-thia-zolate. In the resulting complex, the 2-mercapto-thia-zolate anion acts as a chelating ligand, which coordinates to the NiII ion with the thia-zolyl N and thiol-ate S atoms. In the crystal, π-π stacking inter-actions between the coordinating 1,10-phenanthroline mol-ecules of adjacent complexes result in a zigzag chain running parallel to the c axis. Weak C-H⋯X (X = O, F) hydrogen-bonding inter-actions between the chains and 1,4-dioxane solvent mol-ecules and PF6- counter-anions lead to the formation of sheets parallel to the ac plane.

pH-Dependent structural diversity of a 2-pyridinemethanol Cu complex and its relatively strong magnetic exchange coupling via hydrogen bonding.

The diversity of the self-assembled structures of a Cu complex via hydrogen bonding, including a square planar unit, is reported. The Cu complex forms two self-assembled structures by hydrogen bonding, depending on the acidity of the recrystallization conditions. A linear chain structure can be produced under acidic conditions, and a three-dimensional network structure is observed under basic conditions. The linear chain structure is constructed from intermolecular sharing of a hydrogen atom between two 2-pyridinemethanolate units, with an OO distance of 2.412(1) Å and an O-H-O bond angle of 170(3)°. The linear chain structure exhibits relatively strong magnetic coupling (J = -9.91(2) cm-1) via hydrogen bonding between Cu atoms; this coupling was also confirmed by electron spin resonance experiments. Thermochromic behavior was also observed for the complex.

Bis[(5-bromo-pyridin-2-yl)methano-lato-κ(2) N,O]copper(II) monohydrate.

In the title compound, [Cu(C6H5BrNO)2]·H2O, the Cu(II) ion has a square-planer N2O2 coordination environment. Slipped π-π stackings [centroid-centroid distances: 3.625 (3), 3.767 (3), 3.935 (3) and 4.255 (3) Å] between pyridine rings and Cu⋯π inter-actions (centroid-to-Cu(II) distance: 3.56 Å) between Cu(2+) ions and pyridine rings lead to a layered arrangement parallel to (010). Inter-molecular Br⋯O inter-actions [Br⋯O distances: 2.904 (3) and 3.042 (3) Å] and O-H⋯O hydrogen bonds form a three-dimensional network structure.

Bis(2,2'-bipyridine)(pyridin-2-olato)ruthenium(II) hexa-fluorido-phosphate benzene hemisolvate.

In the title compound, [Ru(C(5)H(4)NO)(C(10)H(8)N(2))(2)]PF(6)·0.5C(6)H(6), the Ru(2+) cation has a distorted octa-hedral RuN(5)O coordination environment. This complex is more distorted than the closely related ruthenium complex containing a pyridine-2-thiol-ate ligand [Santra et al. (1997 ▶). J. Chem. Soc. Dalton Trans. pp. 1387-1393]. The distortion is caused by the difference in size between the O and S atoms. The benzene solvent mol-ecule is situated on a twofold rotation axis.

Tris(pyridin-2-yl-methanol)nickel(II) hexa-fluoridophosphate trifluoro-acetate.

In the crystal structure of the title complex, [Ni(C(6)H(7)NO)(3)](PF(6))(C(2)F(3)O(2)), the Ni(II) ion is in a slightly distorted octa-hedral NiO(3)N(3) coordination geometry with each of the three N and three O atoms in a meridional coordination. In the crystal, the complex mol-ecules and the trifluoro-acetate anions are connected via O-H⋯O hydrogen bonding into layers parallel to the ab plane.

Novel 2-mercaptopyridine-ruthenium complex exhibiting electrochemically induced linkage isomerization switched on/off by protolysis.

A ruthenium complex [ruthenium bis(2,2'-bipyridine)(2-mercaptopyridine)(pyridine)](PF6)2 was crystallographically characterized from its deprotonated form and was electrochemically investigated. In the deprotonated complex, the 2-mercaptopyridine ligand coordinates to the Ru atom only by the S atom; therefore, the N atom of the 2-mercaptopyridine ligand can be protonated. In a CH3CN solution, the complex shows a reversible redox couple attributed to RuIII/II-S. The addition of a base to the CH3CN solution of the complex gives irreversible voltammograms, implying electrochemically induced linkage isomerization between RuII-S and RuIII-N. Analysis of the observed cyclic voltammograms gave the equilibrium and rate constants for linkage isomerization: KIINS = 1.2 x 1018, KIIINS = 0.64, kIINS = 5 x 10 s(-1), kIISN = 4 x 10-17 s(-1), kIIINS = 0.26 s(-1), and kIIISN = 0.40 s(-1).

Diffusional behavior of poly(beta-benzyl L-aspartate) in the rodlike, random-coil, and intermediate forms as studied by high field-gradient 1H NMR spectroscopy.

The diffusion coefficients of poly(beta-benzyl L-aspartate)(PBLA) with the alpha-helix (rodlike) form in chloroform and the random-coil form in a mixture of chloroform and trifluoroacetic acid have been measured as a function of the PBLA concentration (C(PBLA)) by using high field-gradient 1H NMR. The PBLA concentration range for the former is from 0.11 to 9.20 wt % and for the latter it is from 0.20 to 25.2 wt %. From these experimental results, it is found that the diffusion coefficient of PBLA in the rodlike form is much smaller than that of PBLA in the random-coil form at the same PBLA concentration. This implies that the small diffusion coefficients of PBLA in the rodlike form as compared with those in the random-coil form come from the relatively large radius of gyration Rg. Further, it is found that the diffusional behavior of PBLA in the rodlike form is different in the three PBLA concentration regions, that is, region 1 (C(PBLA) = 0.11 approximately 0.39 wt %), region 2 (C(PBLA) = 0.39 approximately 0.86 wt %), and region 3 (C(PBLA) = 0.86 approximately 9.20 wt %). In the random-coil form, the diffusion is different in the two PBLA concentration regions, that is, region I (C(PBLA) = 0.20 approximately 1.03 wt %) and region II (C(PBLA) = 1.03 approximately 25.2 wt %). These diffusional behaviors in the rodlike form and in the random-coil form can be reasonably explained by Tinland-Maret-Rinaudo theory and de Gennes theory, respectively. Further, transitional change from the rodlike form to the random-coil form is discussed on the basis of the diffusional behavior.

Structural characterization of poly(diethylsiloxane) in the crystalline, liquid crystalline and isotropic phases by solid-state 17O NMR spectroscopy and ab initio MO calculations.

The structure of poly(diethylsiloxane) (PDES) has been characterized using solid-state NMR of (17)O. The sample studied had a weight-average molecular weight of 2.45 x 10(5). The sample was prepared by utilizing the cationic ring-opening polymerization of (17)O-enriched hexacyclotrisiloxane. Solid-state NMR of (17)O-enriched PDES was measured on the low-temperature beta(1) phase, the high-temperature beta(2) phase, the two-phase system consisting of the liquid crystal and isotropic liquid phase and the isotropic phase. From these data, the molecular structure and dynamics of PDES in the various phases were characterized via the chemical shifts of (17)O, and electric field gradient parameters were determined from NMR and ab initio molecular orbital (MO) calculations. In addition to the solid-state NMR of (1)H, (13)C and (29)Si previously reported on these samples, knowledge of the dynamic behavior of PDES as inferred from the NMR of (17)O in the present study was enhanced significantly. Further, the potential of combining the experimental NMR of (17)O with ab initio MO calculations to characterize the dynamics of polymers containing oxygen is demonstrated.

A study of conformational stability of poly(L-alanine), poly(L-valine), and poly(L-alanine)/poly(L-valine) blends in the solid state by (13)C cross-polarization/magic angle spinning NMR.

13C cross-polarization/magic angle spinning (CP/MAS) NMR and (1)H T(1rho) experiments of poly(L-alanine) (PLA), poly(L-valine) (PLV), and PLA/PLV blends have been carried out in order to elucidate the conformational stability of the polypeptides in the solid state. These were prepared by adding a trifluoroacetic acid (TFA) solution of the polymer with a 2.0 wt/wt % of sulfuric acid (H(2)SO(4)) to alkaline water. From these experimental results, it is clarified that the conformations of PLA and PLV in their blends are strongly influenced by intermolecular hydrogen-bonding interactions that cause their miscibility at the molecular level.