65013-17-4Relevant academic research and scientific papers
Axial Substitution Reaction of Substituted Pyridine on Chloro(5,10,15,20-tetraphenylporphinato)chromium(III) in Toluene with Special Reference to the Substituent Effect
Inamo, Masahiko,Sugiura, Sachio,Fukuyama, Hiroshi,Funahashi, Shigenobu
, p. 1848 - 1854 (1994)
Equilibria and kinetics for the axial substitution reaction of pyridine and substituted pyridines (L) coordinated to chloro(5,10,15,20-tetraphenylporphinato)chromium(III) by 1-methylimidazole as an entering ligand in toluene have been studied spectrophotometrically..Equilibrium constants, rate constants, and activation parameters for the substitution of L from the six-coordinated complex have been obtained.It has been demonstrated that equilibrium constants of the substitution reaction depend on the basicity of the axial ligands and that a good linear relationship between the activation parameters and the basicity of L is in accord with the reaction mechanism with a limiting dissociative activation mode.
Effect of a Sterically Hindered Imidazole Ligand on the Molecular Structure and Axial Ligand Substitution Reaction of the Chromium(III) Porphyrin Complex
Inamo, Masahiko,Nakajima, Kiyohiko
, p. 883 - 891 (1998)
A structural, thermodynamic, and kinetic study of a chromium(III) complex of 5,10,15,20-tetraphenyrporphyrin, [Cr(tpp)(Cl)(L)], where L represents an imidazole ligand, is presented. The present study is aimed at elucidating the effect of a steric strain induced by the 2-methyl substituent of the imidazole ligand on the molecular structure and the dynamics of an axial ligand-substitution reaction. Crystals of the 1-methylimidazole complex [Cr(tpp)(Cl)(1-Meim)] (1) and 1,2-dimethylimidazole complex [Cr(tpp)(Cl)(1,2-Me2im)] (2) were obtained from a dichloroethane-toluene mixture containing a slight excess of imidazole ligand in the monoclinic space group Cc, Z = 4, a = 18.306(2), b= 13.311(2), c = 21.391(5) A, β= 120.05(1) A, V = 4512(1) A3, and in the orthorhombic space group P2i2i2i, Z = 4, a = 9.926(1), b = 17.902(3), c = 25.247(4) , V = 4486(1) A3, respectively. The axial Cr-Nim bond lengths for 1 and 2 are 2.103(4) and 2.139(5) A, respectively. A steric hindrance has been demonstrated by a 0.036 A increase in the Cr-Nim bond length and a tilting and tipping of the imidazole ligand of 2 from the symmetrical position observed in 1. The substitution reaction of the axial pyridine ligand of [Cr(tpp)(Cl)(py)] by various imidazole ligands was studied spectrophotometrically in dichloromethane or in toluene. A steric effect due to the 2-methyl substituent of the imidazole ligand was observed along with an increase in the ligand-dissociation rate and a decrease in the binding constant of the imidazole ligand to the metalloporphyrin. These results were examined in terms of steric interactions between the axial ligand and the porphyrin core.
Effect of the axial halogen ligand on the substitution reactions of chromium(III) porphyrin complex
Okada, Kikuko,Sumida, Atsumi,Inagaki, Rie,Inamo, Masahiko
, p. 473 - 477 (2013/01/13)
The thermodynamics and kinetics of the substitution reaction of the chromium(III) complex of 5,10,15,20-tetraphenylporphyrin, [Cr(TPP)(X)(L)] (X = F, Cl, Br), where L represents a non-charged ligand such as H2O, pyridine, or 1-methylimidazole, was investigated. The present study aimed to elucidate the effect of the axial halogen ligand, X on the substitution reaction of the ligand trans to X. The substitution reaction of the axial pyridine ligand of [Cr(TPP)(X)(Py)] by 1-methylimidazole was studied spectrophotometrically in dichloromethane, and it was found that the reaction proceeds via a limiting dissociative mechanism and the activation enthalpy of the dissociation of pyridine is much smaller for the fluorine complex, [Cr(TPP)(F)(Py)], than for the chlorine complex, [Cr(TPP)(Cl)(Py)], i.e., ΔH? = 57.5 ± 1.1 and 97.2 ± 1.4 kJ mol-1, respectively. These results are discussed in terms of the trans effect of the halogen ligand on the axial ligand substitution reaction of [Cr(TPP)(X)(L)], and it is concluded that the strength of the bond shows the tendency of Cr-F > Cr-Cl > Cr-Br, leading to the strong trans effect of the F- ligand.
Femtosecond time-resolved photo-absorption studies on the excitation dynamics of chromium(III) porphyrin complexes in solution
Inamo, Masahiko,Okabe, Chie,Nakabayashi, Takakazu,Nishi, Nobuyuki,Hoshino, Mikio
, p. 167 - 172 (2008/09/21)
The electronic relaxation dynamics of the excited states of the chromium(III) tetraphenylporphyrin complexes, [Cr(TPP)(Cl)(L)] (L = H2O, pyridine, 1-methylimidazole), in toluene were studied by using femtosecond time-resolved absorption spectroscopy. The excited state (4T1) of 1-methylimidazole and pyridine complexes given by a very rapid intersystem crossing from 4S1 to 4T1 decays to establish the 4T1 ? 6T1 equilibrium in several hundred picoseconds. The 4T1 state of [Cr(TPP)(Cl)(H2O)] exhibits a biexponential decay composed of the photodissociation process of the axial H2O ligand and the decay of the photolyzed intermediate to the ground state of [Cr(TPP)(Cl)].
