Kan Wakamatsu

Experimental and theoretical investigations of absolute stereochemistry and chiroptical properties of enantiopure 2,2′-substituted 9,9′-bianthryls

Abstract The absolute stereochemistry of axially chiral 2,2′-X 2 -9,9′-bianthryls (X=COOH, COOMe, and Cl) was determined by X-ray analysis of the (+)-quinidine salt of the diacid to be ( M )-(−) or ( P )-(+). The M isomers of these compounds showed specific rotations of −115, −123, and −32, respectively, in acetone. The circular dichroism (CD) as well as UV spectra of the two M isomers (X=COOMe and Cl) were investigated with the aid of theoretical calculations by the time-dependent DFT (TDDFT) method. The calculations reasonably reproduced the observed CD bands, and suggested a correlation between the signs of p or β ′ bands and the absolute stereochemistry.

Stereogenic Motif Consisting of Rigid Ring and Intraannular Chains: Isolation and Structures of Stereoisomers of 9-Alkyl-1,8-anthrylene−Butadiynylene Cyclic Dimers(1)

Stereoisomers of the title pi-conjugated compounds with intraannular propyl and butyl groups were isolated by chromatography. The high barrier to isomerization is attributed to the steric hindrance between the alkyl chains and the rigid framework.

One-Shot Double Amination of Sondheimer–Wong Diynes: Synthesis of Photoluminescent Dinaphthopentalenes

Photoluminescent diamino-substituted dinaphthopentalenes were synthesized successfully by the treatment of in situ prepared dinaphthocyclooctadiyne with lithium amide. This reaction involves a series of transformations including the nucleophilic addition of the lithium amide to a triple bond of the cyclooctadiyne moiety, transannulation, protonation of the resulting pentalene anion, and the nucleophilic substitution of the pentalene core with the lithium amide. In this procedure, a novel double amination step plays a key role. When the diamino-substituted dinaphthopentalenes were irradiated with UV light in toluene, fluorescence was observed at around 580 nm (ΦF < 0.03).

Macrocyclic 2,7-Anthrylene Oligomers

A macrocyclic compound consisting of six 2,7-anthrylene units was successfully synthesized by Ni-mediated coupling of the corresponding dibromo precursor as a novel π-conjugated compound. This compound was sufficiently stable and soluble in organic solvents due to the presence of mesityl groups. X-ray analysis showed that the molecule had a nonplanar and hexagonal wheel-shaped framework of approximately S6 symmetry. The dynamic process between two S6 structures was observed by using the dynamic NMR technique, the barrier being 58 kJ mol(-1) . The spectroscopic properties of the hexamer were compared with those of analogous linear oligomers.

DFT calculation and X-ray structure of nitrosyl pentaammine chromium complex

Abstract The optimized structures of nitrosyl pentaammine chromium complex [Cr(NO)(NH 3 ) 5 ] 2+ ( A ) at three different spin multiplicities, doublet ( A2 ), quartet ( A4 ), and sextet ( A6 ), were obtained by ab initio calculation at B3LYP/6-31G ∗ (6-31+G ∗ for NO) level of theory. The complex A was most stable at the lowest spin multiplicity (doublet), which is in harmony with the previous magnetic measurement ( μ eff =1.8 BM) of the perchlorate of A , [Cr(NO)(NH 3 ) 5 ](ClO 4 ) 2 ( A ′ ) . The X-ray structure of A ′ was determined: Cr–N(NO), 1.677(6) A; N–O, 1.180(7) A; Cr–N(NH 3 , trans ), 2.140(5) A; Cr–N(NH 3 , cis ), 2.080(6)–2.096(6) A; Cr–N–O, 179.9(6)°. The optimized structure ( A2 ) is in good agreement with the experimental one. The present result shows that the covalent type π bondings between Cr and N(NO), which is ascribed to the overlapping between two π ∗ orbitals of NO and two π orbitals of Cr, cause the extra stabilization of A2 .

TDDFT study of electronic spectra of photochromic dinuclear molybdenum complex

Abstract The time-dependent density functional theory (TDDFT) was applied to the calculation of the electronic spectrum of a dinuclear molybdenum complex, [Mo2(μ-S2)(μ-S2C2R2)2 (S2C2R2)2] (R=H), which was a model for the photochromic complex (R=Ph). The calculated results showed that TDDFT based on B3LYP theory would be useful for the calculation of electronic spectra of molybdenum compounds.

The Free Enthalpy Dependence of Rate Constants of Return Electron Transfer within Photoproduced Geminate Radical Ion Pairs

Electron transfer reactions from l,4-diphenyl-l,3-butadienes to excited singlet anthracenecarbonitriles were studied in acetonitrile by an emission-absorption flash photolysis method. Free radical yields determined were used to establish the relationship between the rate of return electron transfer within photoproduced geminate radical ion pairs and the free enthalpy change of the reaction. A typical bell-shaped relationship was found.

Theoretical study of photochromic dinuclear molybdenum complexes

Abstract In order to elucidate the mechanism of photochromism observed for [Mo 2 (μ-S 2 )(μ-S 2 C 2 Ph 2 ) 2 (S 2 C 2 Ph 2 ) 2 ] ( 1a ), the model complexes of 1a and [Mo 2 (μ-S 2 ) 2 (μ-S 4 )(S 2 C 2 Ph 2 ) 2 ] ( 2a ), in which all phenyl groups are replaced by hydrogens, have been optimized by using ab initio and hybrid DFT (B3LYP) programs. We found that B3LYP/3-21G* afforded the best results, so that the hybrid DFT should be a useful tool for the transition metal complexes. The photochromic property originates from the isomerization at the lowest excited state, and the analysis of its electronic properties suggests that the CT transition from the π-orbitals of the bridged ethylene-1,2-dithiolate ligand to Mo d-orbitals of 1a would trigger the isomerization.

Electron transfer induced isomerization of cis,trans-and trans,trans-1,4-diphenyl-1,3-butadiene

Abstract Irradiation of cis,trans - or trans,trans -1,4-diphenyl-1,3-butadiene with 9,10-dicyanoanthracene as a sensitizer results in predominant cis,trans → trans,trans geometric isomerization in acetonitrile. A cation radical chain mechanism is proposed to be operative.

Dual Emission and Mechanofluorochromism of a V-Shaped π-System Composed of Disulfonyl-Substituted Dibenzocyclooctatetraenes

A series of dibenzocyclooctatetraenes 6 bearing phenylethynyl and phenylsulfonyl groups were synthesized from bromo-substituted formylbenzyl sulfone 4 via cyclic dimerization of 4 and Sonogashira coupling of the resulting dibromocyclooctatetraene 3 with terminal acetylenes. The diamino derivative 6b exhibited dual emission with emission maxima at 436 and 547 nm. Furthermore, in the fluorescence of 6b, solvatofluorochromism was observed in response to solvent polarity, whereas in the solid states, mechanofluorochromism was observed.