Katsura Mochizuki

Electronic spectra of benzo-substituted phthalocyanines

Various types of 2,3- and 1,2-benzo-substituted zinc-phthalocyanines were prepared to investigate the influence of the substitutions on the electronic states of phthalocyanine (Pc) compounds. The experimental data showed that these compounds can be categorized by their spectral patterns. A simple perturbation method based on the group theory (symmetry-adapted perturbation method) is presented to analyse the spectroscopic changes of Pc compounds caused by the substitutions. This method was tested against the experimental data and gave good agreement.

Tetranuclear nickel(II) complex derived from bis(macrocycle), μ-terephthalato-bis{aqua-7,7′-o-xylylenebis{3,7,11,17-tetraazabicyclo[11.3.1]-heptadeca-1(17), 13,15-trienedinickel(II)}} iodide, {[Ni2(OH2)(L)]2(μ-terephthalato)}I6

Abstract A new o-xylylene linked bis(macrocyclic) dinickel(II) complex was synthesized. A couple of bis(macrocyclic) nickel(II) complexes with the pseudo face-to-face structure captured one terephthalate ion to form the novel tetranuclear nickel(II) complex.

Synthesis, molecular and electronic structure of complexes [LNaMIVNaL](MRu,Os; H3L = 1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane)

The trinuclear complexes [LNaMIVNaL](M = Ru 1, Os 2) where L represents the hexadentate ligand 1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane have been synthesized and 1 has been characterized by X-ray crystallography; complex 1 contains an octahedral MIVS6 central core and two trigonal-prismatic terminal LNa units with an N3S3 donor set; the electronic structure of the MIVS6 core (M = Ru, Os), has been established as S= 1 by temperature-dependent magnetic susceptibility measurements.

Preparation and structural determination of methyl 3-C-p-tolylsulfonyl-2-C-p-tolylthio-β-d-glucopyanoside derivatives and their 5a-carba-dl-analogs having non-chair conformation in solutions

Methyl 4,6-O-benzylidene-2,3-dideoxy-3-C-p-tolylsulfonyl-2-C-p-tolylthio-β-d-glucopyranoside and its 5a-carba-dl-analog exit mainly in a non-chair conformation in solutions, but the latter occupies a chair conformation in a solid state.

HYDROGENATION OF A DELOCALIZED DIIMINATE SIX-MEMBERED CHELATE RING IN TETRAAZAMACROCYCLIC NICKEL(II) COMPLEXES BY SODIUM BOROHYDRIDE IN WATER—EFFECT OF PROTONATION-DEPROTONATION EQUILIBRIA AND STEREOSELECIVE REDUCTION

Abstract Charge delocalized diiminate six-membered chelate rings in the 5,7-dimethyl-1,4,8,11-tetraazacyclotetradecane-4,6-dienatonickel(II) ion(1) and the α,α′-bis(5,7-dimethyl-1,4,8, 11-tetraazacyclotetradeca-4,6-dienato-6-yl)-xylenedinicke(II) ion(2) were hydrogenated in aqueous media by sodium borohydride. In the reduction reactions, control of the pH of the reaction mixture was essential, and the pH of the solution was kept during the reaction at 3 and at 5–6 for hydrogenations of 1 and 2, respectively. The delocalized diiminate chelate ring is in protonation-deprotonation equilibrium with the β diimine form and the pKa of the equilibrium for 2 was determined to be 9.0 for 2a (o-xylylene bridged complex), 9.3 for 2b (m-xylylene bridged complex), and 10.0 for 2c (p-xylylene bridged complex). The appropriate pH values in the hydrogenation reactions were based on the pKa′s. X-ray structure analyses on two reduction products of 1 show that the chirality of the two asymmetric carbons in the cyclam ring is...

Selective synthesis of a novel non-symmetrical bimacrocyclic ligand and its dinickel(II) complex

Abstract A selective synthesis of non-symmetrical bimacrocyclic ligand by using the ‘lariat’ Ni(II) complex is reported. The bimacrocyclic ligand in which only one of the macrocycles has cyanoethyl groups has been synthesized and characterized by 13CNMR and FAB mass spectroscopy. The dinickel(II) complex with the ligand has been isolated as the salt with one chloride and three perchlorates. The visible absorption spectrum of the dinickel(II) complex indicates that one of the Ni(II) ions has a square planar configuration and the other is five-coordinate.

Structure and properties of an oxalato-bridged dinickel(II) complex with a tetraazamacrocycle bearing an aminomethyl pendant arm, 5-aminomethyl-5R(S),12R(S)-dimethyl-1,4,8,11-tetraazacyclotetradecane

The oxalato-bridged dinickel(II) complex with the title ligand, [Ni2(L a H)2(μ-ox)](ClO4)2·2H2O (1), was prepared and its structure was determined by X-ray crystallography, as well as that of the monomeric nickel(II) complex, [Ni(L a H)ox]ClO4·3H2O (2). In Complexes 1 and 2, the ligand, L a , is folded along the N(4)–Ni(1)–N(11) axis. The antiferromagnetic coupling between the two nickel(II) centers in 1 was revealed and the coupling constant, J = −17.4 cm−1, and g = 2.11 were estimated. It was found that the oxalato-bridged dimer 1 was readily converted to the mononuclear cis-nickel(II) complex [NiL a (OH2)](ClO4)2 (3a), in basic aqueous solution. In [NiL a (CH3CN)]I2 (3b), which was derived from 3a, the aminomethyl pendant arm is coordinated to the Ni(II) ion and L a is folded along the N(1)–Ni(1)–N(8) axis.

Structures and short contacts of F⋯O(nitro) and H⋯O(nitro) in 2,2-di(4-nitrophenyl)hexafluoropropane and 2,2-di(4-nitrophenyl)propane

Abstract 2,2-Di(4-nitrophenyl)hexafluoropropane ( 1 ) and 2,2-di(4-nitrophenyl)propane ( 2 ) were synthesized and their crystal structures were determined. The crystals of both diarylpropanes have helical conformations with unsymmetrical ring-twist angles, φ A =46.7, φ B =33.5° for 1 , and φ A =64.9, φ B =31.8°, for 2 . In contrast, density functional theory calculations indicate symmetrical, helical C 2 states for both 1 ( φ A = φ AB =43.1°) and 2 ( φ A = φ B =51.5°). Intermolecular π–π-stacks along the a -axis of the crystals are composed of a pair of nitrophenyl rings oriented in opposite directions. Short contacts of O(nitro)⋯F and O(nitro)⋯H(Me) within the sum of van der Waals radii were also found in 1 and 2 , respectively.

Studies on pyrazines. Part 34.1 Synthetic approach, stability and tautomerism of 2,6-dihydroxypyrazines

Demethylation of 2,6-dimethoxy-3,5-diphenylpyrazine with iodotrimethylsilane gives the corresponding 2,6-dihydroxy- and 2-hydroxy-6-methoxy-pyrazines, whilst the 3-methyl-5-phenyl analogue affords only monohydroxy compounds. In contrast, 2,6-dimethoxy-3,5-dimethylpyrazine decomposes completely under the demethylation conditions. Hydrolysis of 2,6-diacetoxypyrazines succeeds only in the formation of 2,6-dihydroxy-3,5-diphenylpyrazine. The stability of 2,6-dihydroxypyrazines is discussed on the basis of observations made in the synthetic approach. In addition, it has been established, on the basis of UV spectral analysis, that the 2-hydroxy-6-methoxypyrazines obtained in our work exist predominantly in the hydroxypyrazine form rather than as 1,2-dihydropyrazin-2-ones.

Monoepoxidation of Humulene 2,3-Epoxide to Humulene 2,3: 6,7-Diepoxides. Observation of the Rotation of the Double Bond Plane by 1H NMR Spectral Analysis and Conformation

The reaction of (6E,9E)-humulene 2,3-epoxide (7) with m-CPBA produced two known humulene 2,3;6,7-diepoxides (8 and 9), and careful analysis of the 1 H NMR of 7 at various temperatures suggested an equilibrium of four possible conformations, CT, CC, TC and TT, over 0°C together with free rotation of the 9,10-double bond plane in 8 at 85°C.