Electro- and photochemical properties of a (mu-alkoxo)bis(mu-carboxylato)diruthenium complex having two tetraphenylporphinato zinc(II) moieties

The novel (mu-alkoxo)bis(mu-carboxylato)diruthenium complex K[Ru(2)(dhpta)(mu-O(2)C-p-ZnTPP)(2)] 3 was prepared by simple ligand substitution reaction. Strong antiferromagnetic interaction between two Ru(III) ions of 3 was observed with a coupling constant of -425 approximately -404 cm(-1). The cyclic voltammogram of 3 can be explained in terms of superposition of those of ZnTPP-p-CO(2)H and K[Ru(2)(dhpta)(mu-O(2)CPh)(2)] 2, indicating no significant electrochemical interaction. The large conproportionation constant estimated from the reduction potentials for Ru(III)Ru(III) and Ru(II)Ru(III) indicates great stability of the mixed-valence state. The mixed-valence species [Ru(II)Ru(III)(dhpta)(mu-O(2)C-p-ZnTPP)(2)](2-) 4 was prepared by controlled potential electrolysis. The electronic absorption spectrum of 4 was quite similar to that of [Ru(II)Ru(III)(dhpta)(mu-O(2)CCH(3))(2)](2-) which is a typical Class II complex. The fluorescence from the S(2) state of the ZnTPP unit of 3 was significantly (78%) quenched. The electron transfer from the ZnTPP unit to Ru(III) ions in 3 is a plausible mechanism, even though energy transfer could not be ruled out completely. The free energy change for electron transfer, Delta G(CS), was estimated to be ca.-1.1 eV, which is similar to typical values for the reorganization energy lambda in polar solvents. Hence, the electron transfer scheme is situated almost at the top of the Marcus parabola, enabling ultrafast electron transfer.     

Aryl Oxalate Derivatives as Convenient Precursors for Generation of Aryloxyl Radicals

The use of aryloxy oxalyl chlorides (AOCs), aryloxy oxalyl tert-butyl peroxides (AOBs), and diaryl oxalates (DAOs) for unimolecular generation of phenoxyl-based radicals under solution and rigid matrix conditions is described. AOCs are usable for photochemical generation of phenoxyl radicals, but are only conveniently stable as precursors when 2,6-di-tert-butylated derivatives are used. AOBs may be used as thermal precursors to aryloxyl radicals, since they typically decompose within 2-3 h at 60-85 degrees C to give phenols. (1)H-NMR solution kinetic studies find that DeltaH() = 31 kcal/mol, and DeltaS() = +3.4 cal/mol-K for decomposition of phenoxyoxalyl tert-butyl peroxide, consistent with substantial concertedness in peroxide bond cleavage. AOBs and the more stable DAOs are also convenient photochemical phenoxyl radical precursors. AOBs yield phenoxyl radicals more readily by photolysis than do corresponding DAOs, but the DAOs have fewer side reactions that can quench the product phenoxyl radicals.     

Internal rotational motion of the chloromethyl group of the jet-cooled benzyl chloride molecule

The mass-resolved resonance enhanced two-photon ionization spectra of jet-cooled benzyl chloride were measured. Some low-frequency vibronic bands around the S1-S0 origin band were assigned to transitions of the internal rotational mode of the chloromethyl group. The internal rotational motion was analyzed by using the one-dimensional free rotor approximation. The conformation in the S1 state was found to be that in which the C-Cl bond lies in orthogonal to the benzene plane. For the species with m/e 126, the transition energy of the internal rotational bands corresponded well to the potential energy values of V2 = 1900 cm(-1) and V4 = 30 cm(-1) in the S1 state and the reduced rotational constant B values 0.50 and 0.47 cm(-1) in the S0 and S1 states, respectively. The B values obtained for the chlorine isotopomer (m/e 128) were slightly different. The S1 potential barrier height was found to be about 3 times larger than that for the S0 state. Molecular orbital calculations suggest that the difference between energies of the HOMO and LUMO with respect to the rotation of the chloromethyl group correspond approximately to the potential energy curve obtained for the S1 state.     

细胞色素C的薄层光谱电化学研究

细胞色素C(Cyt. C)在电极界面上的电子传递十分缓慢,只有在适当的电子迁移中介体(Mediator)或促进剂(Promoter)参与下才能以较快的速度进行反应,本文报道了以4,4′-二硫基联吡啶(PySSPy)作电极反应促进剂,用薄层光谱电化学技术研究细胞色素C在金微网栅薄层透光电极界面上的电化学过程,测定了电极反应的热力学参数E~(o′)及n,并与循环伏     

A complete series of copper(II) halide complexes (X = F, Cl, Br, I) with a novel Cu(II)-C(sp3) bond

A complete series of copper(ii) halide complexes [CuX(tptm)](X = F (), Cl (), Br (), I (); tptm = tris(2-pyridylthio)methyl) with a novel Cu(II)-C(sp(3)) bond has been prepared by the reactions of [Cu(tptm)(CH(3)CN)]PF(6)(.PF(6)) with corresponding halide sources of KF or n-Bu(4)NX (X = Cl, Br, I), and the trigonal bipyramidal structures have been confirmed by X-ray crystallography and/or EPR spectroscopy. The iodide complex easily liberates the iodide anion in acetonitrile forming the acetonitrile complex as a result. The EPR spectra of the complexes showed several superhyperfine structures that strongly indicated the presence of spin density on the halide ligands through the Cu-X bond. The results of DFT calculations essentially matched with the X-ray crystallographic and the EPR spectroscopic results. Cyclic voltammetry revealed a quasi-reversible reduction wave for Cu(II)/Cu(I) indicating a trigonal pyramidal coordination for Cu(I) states. A coincidence of the redox potential for all [CuX(tptm)](0/+) processes indicates that the main oxidation site in each complex is the tptm ligand.     

Positive working resists sensitive to visible light,I: poly(tert-butyl and 2-phenylpropyl-2 methacrylates) sensitized with diphenyliodonium salt — p-aminobenzylidene dye system

Visible-light-sensitive positive type resists have been developed. The chemistry to form images is based on the cleavage of side chain ester bonds of poly(methacrylates) catalyzed by an acid which is generated on sensitized photodecomposition of a diphenyliodonium (DPI) salt. Homopolymers and copolymers of tert-butyl methacrylate (BMA) and 2-phenylpropyl-2 methacrylate (PPMA) were used as acid labile polymers. Exposure of thin films of the poly(methacrylates) containing DPI salt and p-dimethylaminobenzylidene derivatives to an Ar laser beam emitting 488 nm light and subsequent heat treatment resulted in solubility alteration of the polymers, which became soluble in a protic solvent system. Considerable reduction of film thickness was observed after heating an image-wise exposed thin film of PPMA polymers. The minimum exposure energies of 488 nm light for the positive image formation were 60 mJ/cm² and 40 mJ/cm² for BMA and PPMA homopolymers, respectively.     

Experimental and Computational Studies of Charge-Transfer and Reduction Products of 1, 4, 5, 8, 9, 11-Hexaazatriphenylene-Hexacarbonitrile: HAT-(CN)<Subscript>6</Subscript>

The compounds HAT-(CN)₆ · C₇H₈ · CH₃CN, 1, {[(Cp)₂Co][PF₆]}₃HAT-(CN)₆, 2, {([n-Bu₄N][I])₃HAT-(CN)₆]₂} · 3C₆H₆, 3, were prepared and characterized by X-ray crystallography (HAT-CN₆ = hexaazatriphenylene-hexacarbonitrile). The bonding in the neutral form of HAT-CN₆, (1), is compared to the co-crystallized examples of (HAT-CN₆) with [Cp₂Co][PF₆] (2) and [n-Bu₄N][I] (3). In the case of (3), the structure consists of layers of HAT-CN₆ molecules and four positions of three partially occupied I^- anions, one of which participates in a columnar stacking arrangement with HAT-CN₆. The nearly black color of crystals of (3) as compared to the light green color of (1) and the dark green color of (2) indicates that significant charge-transfer is occurring between the I^- ion and the HAT-CN₆ molecules. In addition to investigating the structures of various HAT-CN₆ containing samples, the one- and two-electron reduction products K[HAT-(CN)₆] and K₆[HAT-CN₆] were prepared by treatment of HAT-CN₆ with appropriate equivalents of K metal and EPR studies were undertaken. The results support the conclusion that the mono-radical is a typical S = 1/2 species and that the doubly-reduced species is a di-radical with a triplet ground state. Density functional theory calculations were carried out on the neutral, mono-anionic, and di-anionic forms of HAT-CN₆ to deduce the ground state geometry and spin state of each molecule. The theoretical results are in accord with the lowest energy ground state of [HAT-CN₆]^2- being a triplet state.     

Parity violation in a single domain of spin-triplet Sr2RuO4 superconductors

We observed an unconventional parity-violating vortex in single domain Sr₂RuO₄ single crystals using a transport measurement. The current–voltage characteristics of submicron Sr₂RuO₄ show that the induced voltage has anomalous components which are even functions of the bias current. The results may suggest that the vortex itself has a helical internal structure characterized by a Hopf invariant (a topological invariant). We also discuss that the hydrodynamics of such a helical vortex causes the parity violation to retain the topological invariant.