TY - JOUR
T1 - Photodissociation of Bis(S-benzyl-1,2-diphenyl-1,2-ethylenedithiolato)metal (Ni, Pd, Pt) Complexes
AU - Ohkoshi, Shin Ichi
AU - Ohba, Yasunori
AU - Iwaizumi, Masamoto
AU - Yamauchi, Seigo
AU - Ohkoshi-Ohtani, Miharu
AU - Tokuhisa, Keiichi
AU - Kajitani, Masatsugu
AU - Akiyama, Takeo
AU - Sugimori, Akira
PY - 1996/12/1
Y1 - 1996/12/1
N2 - Bis(S-benzyl-1,2-diphenyl-1,2-ethylenedithiolato)metal (Ni,Pd,Pt) (1a-c) complexes are known to undergo photochemical reactions that produce the corresponding neutral free metal dithiolene M(S2C2Ph2)2 (3a-c) complexes in solution. The reaction mechanisms of these photoreactions were examined by means of EPR and UV/vis absorption techniques. In the first step of the reaction the photodissociation of a C-S bond occurs to yield one benzyl radical and the monobenzyl dithiolene complex radical (2a-c). Both radicals were observed by timeresolved electron paramagnetic resonance (TREPR). The benzyl radical was also trapped by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl). Analysis of the TREPR signals shows that the radicals are produced from the excited triplet states of 1a-c within 100 ns. From the analyses of time-resolved and steady state EPR data, and absorption spectra, the intermediate complex radicals (2a-c) were assigned as [M(S2C2Ph2){S2(CH 2Ph)C2Ph2}] (M = Ni, Pd, Pt). Spin densities on the central metals were determined from their anisotropic g values and hyperfine coupling constants by comparing the data with those of [M(S2C2Ph2)2]-. A correlation between the spin density and the decay time of the intermediate complexes (2a-c) was pointed out. The second step of the reaction was found to be the dissociation of a second benzyl substituent, which occurs in the dark. The reaction rate was discussed in terms of the spin density (ρM) on the metal and the S-C(benzyl) bond order (ρsρc)1/2 of the intermediate radicals, 2a-c.
AB - Bis(S-benzyl-1,2-diphenyl-1,2-ethylenedithiolato)metal (Ni,Pd,Pt) (1a-c) complexes are known to undergo photochemical reactions that produce the corresponding neutral free metal dithiolene M(S2C2Ph2)2 (3a-c) complexes in solution. The reaction mechanisms of these photoreactions were examined by means of EPR and UV/vis absorption techniques. In the first step of the reaction the photodissociation of a C-S bond occurs to yield one benzyl radical and the monobenzyl dithiolene complex radical (2a-c). Both radicals were observed by timeresolved electron paramagnetic resonance (TREPR). The benzyl radical was also trapped by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl). Analysis of the TREPR signals shows that the radicals are produced from the excited triplet states of 1a-c within 100 ns. From the analyses of time-resolved and steady state EPR data, and absorption spectra, the intermediate complex radicals (2a-c) were assigned as [M(S2C2Ph2){S2(CH 2Ph)C2Ph2}] (M = Ni, Pd, Pt). Spin densities on the central metals were determined from their anisotropic g values and hyperfine coupling constants by comparing the data with those of [M(S2C2Ph2)2]-. A correlation between the spin density and the decay time of the intermediate complexes (2a-c) was pointed out. The second step of the reaction was found to be the dissociation of a second benzyl substituent, which occurs in the dark. The reaction rate was discussed in terms of the spin density (ρM) on the metal and the S-C(benzyl) bond order (ρsρc)1/2 of the intermediate radicals, 2a-c.
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M3 - Article
AN - SCOPUS:0001104080
VL - 35
SP - 4569
EP - 4574
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 16
ER -