Hiroshi Tomizawa

Vibrational spectroscopic study of light-induced metastable states of ethylenediaminenitrosylruthenium(II) complexes

Abstract Light-induced metastable states were found in trans - and cis -[RuCl(en) 2 NO]Cl 2 , trans - and cis -[RuBr(en) 2 NO]Br 2 , trans -[Ru(H 2 O)(en) 2 NO]Cl 3 , and a mixture of fac - and mer -[RuCl 3 (en)NO]. These states are formed when the polycrystalline samples are irradiated with blue or green laser lines from an Ar ion laser at 77 K. They decay upon irradiation with red light or a rise in temperature. The NO stretching frequency that is observed in the range from 1865 to 1904 cm −1 in the ground (normal) state of each compound shifts to the lower frequency side by approx. 100–140 cm −1 in the metastable states. These characteristics are similar to those of the metastable states of Na 2 [Fe(CN) 5 NO]·2H 2 O, K 2 [RuHCl 5 NO] and K 2 [Ru(NO 2 ) 4 (OH(NO)]. Decay temperatures of the ethylenediaminenitrosyl-ruthenium(II) complexes are notably higher (approx. 230–270 K) than those of the substances examined in earlier studies (approx. 180–190 K).

Electronic effects of the substituent group in 8-quinolinolato ligand on geometrical isomerism for nitrosylruthenium(II) complexes

Abstract The reaction of hydrous nitrosylruthenium trichloride with 2-chloro-8-quinolinol (H2cqn) or 2-methyl-8-quinolinol (H2mqn) in ethyl alcohol, 50 vol.% ethyl alcohol–water, water or acetic acid solution adjusted to pH 5.5 and the reaction of two kinds of geometrical isomers, cis -1 and cis -2[RuX(qn) 2 NO] (X=acetate or Cl; Hqn=H2cqn or H2mqn), with chloride or acetate ion in ethyl alcohol were examined in order to compare the effect of the chloro and methyl groups of the 2-position in 8-quinolinolato ligands on geometrical isomerism for nitrosylruthenium(II) complexes. The thermal and photoinduced reactions for the 2cqn complexes were also compared with those for the 2mqn complexes. The differences in the substituent in the 8-quinolinolato ligand and of the solvents used for the reactions were related to geometrical isomerism of the products. In general, the 2cqn complexes especially favor the cis -2 geometry, while the 2mqn complexes favor the cis -1 and trans geometries. The structures of cis -1[RuCl(2cqn) 2 NO], cis -2[RuCl(2cqn) 2 NO] and trans -[Ru(OEt)(2mqn) 2 NO] (OEt=ethanolate ion) were determined by X-ray diffraction.

Molecular vibrations and structure of the light-induced metastable state of [Fe(CN)5NO]2−

Abstract The molecular structure of the metastable state (MS1) of sodium nitroprusside was studied by polarized Raman spectroscopy and the normal coordinate analysis on 14 NO - and 15 NO -substituted crystals. The downshift of the bending mode of the Fe–(NO) bond upon 15 NO substitution is significantly smaller in MS1 than in the ground state. The normal coordinate analysis indicates that the effect of the N-atom mass on the mode is large in the Fe–N–O linkage but small in the Fe–O–N linkage. The small isotope shift observed in MS1 suggests the Fe–O–N linkage that was proposed in a recent X-ray diffraction study.

Crystal structures of three geometrical isomers of [Ru(OAc)(2mqn)2NO] (OAc = acetate, H2mqn = 2-methyl-8-quinolinol) and their thermal isomerization reactions

Abstract The structures of three geometrical isomers of [Ru(OAc)(2mqn) 2 NO], one trans isomer and two cis isomers ( cis -1 and cis -2), were determined by X-ray diffraction. OAc in the cis - 1 ( 1 ) and cis -2 isomers ( 2 ) is cis to NO and the geometrics of the ligating N and O atoms in the two quinolinolato ligands are in cis (O,O) and trans (N,N) configurations for 1 and in cis (O,O) and cis (N,N) for 2 . In the trans isomer ( 3 ), OAc is trans to NO and the geometry is in trans (O,O) and trans (N,N) configurations. The RuO(OAc) bond for 3 was shorter than those for 1 and 2 , and the RuO(2mqn) bond trans to NO was also shorter than that cis to NO due to a trans -strengthening effect of NO. Reversible thermal isomerization between 1 and 2 , and the irreversible one from 3 to 1 and 2 were observed in deaerated N , N -dimethyl-formamide at higher than 353 K.

Preparation and characterization of cis- and trans-[Ru(OAc)(2mqn)2NO] (OAc=acetate, 2mqn=2-methyl-8-quinolinolate), and their mutual photoisomerization reactions

Abstract A mixture of hydrated nitrosylruthenium(III) chloride and 2-methyl-8-quinolinol (H2mqu) (1:4 molar ratio) in acetic acid aqueous solution adjusted to pH 5.5 and warmed at c. 70 °C for 2 h led to preparation of cis- [Ru(OAc)(2mqn)2NO] which has cis(0,0) and trans(N,N) configuration for the ligating atoms of the 2mqn ligands. The trans isomer was photochemically prepared from the cis isomer in CH2Cl2 using an Xe lamp as the light source. The photoisomerization in deaerated CH2Br2 was examined at −5 to 30 °C using a super high-pressure Hg lamp (436 mm). Quantum yields of the cis to trans and the trans to cis isomerizations were 1–2.5×10−3 and 8–11×10−3, respectively. Solvent effect studies by adding liquid paraffin to the CH2Br2 solution on the photoreaction and the NO scramble on the irradiation in the presence of 15NO gas showed that RuNO bond rupture takes part in the isomerization.

Reaction of hydrous nitrosylruthenium trichloride with 2-pyridinemethanol

The reaction of hydrous nitrosylruthenium trichloride with an excess of 2-pyridinemethanol (H2pm) in boiling ethyl alcohol gave [H 2 2pm][RuCl 3 (2pm)NO] (H 2 2pm=the proton adduct of H2pm, 2pm=2-pyridinemethanolate ion) ( 1 ) and [RuCl 2 (2pm)(H2pm)NO] ( 2 ). [RuCl(2pm) 2 NO] ( 3 ) was isolated by heating complex 2 in boiling water. The reaction of hydrous nitrosylruthenium trichloride with an excess of H2pm in boiling water gave a slight amount of complex 4 , a geometrical isomer of 3 , together with 2 and 3 . Na[RuCl 3 (2pm)NO]·H 2 O ( 5 ) was prepared from 1 by an anion-exchange chromatography. The complexes obtained were {Ru(II)–NO + } type octahedral complexes. The structures of 1 , 2 and 4 were determined by X-ray crystal analysis. The alcoholato oxygen of 2pm in 1 , 2 or 4 coordinates trans to the NO. For [RuCl 3 (2pm)NO] − in 1 , the three Cl atoms are cis to the NO. For 2 , the ligating N atom of the H2pm is trans to the N atom of the 2pm. For 4 , the Cl atom is cis to the NO and the geometry of the ligating N and O atoms of the two 2pm is in cis ( N,N ) and cis ( O,O ) configuration. The proton NMR spectra showed that, for 3 , the Cl atom is cis to the NO and the geometry of the ligating N and O atoms of the two 2pm is in trans ( N,N ) and cis ( O,O ) configuration and the structure of the complex anion in 5 is the same as that in 1 . In 1 , a strong interaction between [H 2 2pm] + and [RuCl 3 (2pm)NO] − through the proton of [H 2 2pm] + was observed in the solid state and reflected on the electric conductivity in DMF. The protonations to 2 and 3 were observed in the aqueous solution. Changes of 2 to 3 at 373 K and of 3 to 2 in the presence of DCl at room temperature were observed in DMSO.

Interaction between the NO+ ligand and trans π-donor ligands in chloro(2-methyl-8-quinolinolato) nitrosyl(8-quinolinolato)-ruthenium(II) complexes

The reaction of [RuCl3(2mqn)NO] (2mqn is 2-methyl-8-quinolinolato ligand whose phenolato oxygen is trans to the NO) with an excess of 8-quinolinol (Hqn) and the reaction of [RuCl3(qn)NO] (phenolato oxygen in the qn is trans to the NO) with an excess of 2-methyl-8-quinolinol give [RuCl(2mqn) (qn)NO] (1) as a major product, in which oxygen of the 2mqn is trans to the NO and the configuration of the ligating nitrogen atoms of the qn and 2mqn is trans(N,N). The methyl group in the 2-position of qn causes the oxygen in the 2mqn to coordinate predominantly in the trans position to the NO1 ligand.