Structure and photochemical properties of (mu-alkoxo)bis(mu-carboxylato)diruthenium complexes with naphthylacetate ligands

Two new dinuclear Ru(III) complexes containing naphthalene moieties, K[Ru2(dhpta)(mu-O2CCH2-1-naph)2] (1) and K[Ru2(dhpta)(mu-O2CCH2-2-naph)2] (2) (H5dhpta = 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid, naph-1-CH2CO2H = 1-naphthylacetic acid, naph-2-CH2CO2H = 2-naphthylacetic acid), were synthesized. Complex 2 crystallized as an orthorhombic system having a space group of Pbca with unit cell parameters a = 10.6200(5) A, b = 20.270(1) A, c = 35.530(2) A, and Z = 8. EXAFS analysis of 1 and 2 in the solid states and in solution clarified that the dinuclear structures of 1 and 2 were kept in DMSO solutions. Variable-temperature magnetic susceptibility data indicated that the two Ru(III) centers are strongly antiferromagnetically coupled as shown by the large coupling constants, J = -581 cm(-1) (1) and -378 cm(-1) (2). In the cyclic voltammograms of 1 and 2, one oxidation peak and two reduction peaks which were assigned to the redox reaction of the ruthenium moieties were observed in DMF. The large conproportionation constants estimated from the reduction potentials of Ru(III)Ru(III) and Ru(III)Ru(II) indicated the great stability of the mixed-valent state. The mixed-valent species [Ru(III)Ru(II)(dhpta)(mu-O2CCH2-R)2](2-) (R = 1-naph (6) and R = 2-naph (7)) were prepared by controlled potential electrolysis of 1 and 2 in DMF. The electronic absorption spectra of 6 and 7 were similar to that of [Ru(III)Ru(II) (dhpta)(mu-O2CCH3)2](2-) which is a typical Class II type mixed-valent complex. The fluorescence decay of 1 and 2 indicated that there are two quenching processes which come from the excimer and monomer states. The short excimer lifetimes of 1 and 2 were ascribed to the energy transfer from the naphthyl moieties to the Ru centers. The different excimer ratio between 1 and 2 suggested that the excimer formation is affected by the conformation of the naphthyl moieties in the diruthenium(III) complexes.     

A class number formula for the p-cyclotomic field

Let p be an odd prime number and . Let be the classical Stickelberger ideal of the group ring . Iwasawa [6] proved that the index equals the relative class number of . In [2], [4] we defined for each subgroup H of G a Stickelberger ideal of , and studied some of its properties. In this note, we prove that when mod 4 and [G : H] = 2, the index equals the quotient . Received: 13 January 2006     

Note on the rings of integers of certain tame 2-galois extensions over a number field

For a number fieldF, we prove that any tame D4-extensionN/F has a normal integral basis (NIB) if and only if any tame (2, 2)-extensionK/F has a NIB.     

On the 2-part of the ideal class group of the cyclotomic <Emphasis Type="BoldItalic">Z</Emphasis><Subscript><Emphasis Type="Italic">p</Emphasis></Subscript>-extension over the rationals

Let p be an odd prime number, and $\mbox {\boldmath $\mbox {\boldmath the cyclotomic $\mbox {\boldmath $\mbox {\boldmath -extension over the rationals. We show that the 2-part of the ideal class group of $\mbox {\boldmath $\mbox {\boldmath is trivial for p<500.     

On a Theorem of Childs on Normal Bases of Rings of Integers

Let p be a prime number, F a number field, and the set of all unramified cyclic extensions overF of degree p having a relative normal integral basis. When_p F^x, Childs determined the set in terms of Kummer generators. When p=3 and F is an imaginaryquadratic field, Brinkhuis determined this set in a form whichis, in a sense, analogous to Childs's result. The paper determinesthis set for all p 3 and F with _p F^x (and satisfying an additionalcondition), using the result of Childs and a technique developedby Brinkhuis. Two applications are also given.     

A note on Greenberg's conjecture and the abc conjecture

For any totally real number field and any prime number , Greenberg's conjecture for asserts that the Iwasawa invariants and are both zero. For a fixed real abelian field , we prove that the conjecture is ``affirmative' for infinitely many (which split in if we assume the abc conjecture for .

     

Structural and magnetic properties of vanadyl dichloride solvates: from molecular units to extended hydrogen-bonded solids

The preparation, structural characterization and magnetic properties of three solvent adducts of VOCl(2), trans-VOCl(2)(THF)(2)(H(2)O) (1), trans-VOCl(2)(H(2)O)(2).2Et(2)O (2) and cis-VOCl(2)(MeOH)(3) (3) are described. In these solids, hydrogen bonding among the inorganic complexes is the critical determinant of the formation of extended magnetic networks. Compound forms one-dimensional double chains where alternating monomers from the two branches of the chain are hydrogen bonded via the V-Cl ... H-O-V network (with an axial water molecule and equatorial chloride ions). Magnetic studies indicate no interaction among the vanadyl centers. The paramagnetism of 1 is consistent with the extension of the network from the hydrogen donor site of the axial water, which is orthogonal to the d(xy) magnetic orbital. Compound 2 forms one-dimensional chains with water molecules of adjacent monomers held together by hydrogen bonds to ether molecules (V-O-H ... O(ether) ... H -O-V). The chain network radiates only through the equatorial plane of the complex where the water molecules are located. The presence of the intervening solvent molecule between hydrogen bonds of the primary coordination sphere magnetically insulates metal centers and compound is also a simple paramagnet. Removal of the solvent turns on the magnetic interaction and neighboring spin centers couple antiferromagnetically. Compound 3 forms a layered structure via V-Cl ... H-O-V hydrogen bonding, where all the hydrogen donor sites participate in the formation of the network. The vanadyl spin centers, at distances of 5.5 and 6.5 A from each other, couple antiferromagnetically (J/k=-0.7 K). Thus, magnetic coupling among metal centers is achieved when the hydrogen bond network directly radiates from the coordination plane containing the magnetic orbital. These results further support the utility of hydrogen bond as a viable design element in the construction of low dimensional, magnetic solids.     

A convenient photochemical method to immobilize enzymes

A method to immobilize enzymes photochemically with use of photocrosslinkable poly(vinylalcohol) bearing stilbazolium groups is described. Irradiation of a film of the photosensitive polymer containing enzyme gave water-insoluble, cellophane-like transparent film demonstrating high enzyme activity. The dissolution of enzymes from the film was dependent upon the molecular weight of the proteins and the content of the photocrosslinking unit. It was found that various enzymes are sufficiently entrapped in the photocrosslinked polymer matrix when the content of the photosensitive group is more than about 1.0 mol%.