Photodissociation of Bis(S-benzyl-1,2-diphenyl-1,2-ethylenedithiolato)metal (Ni, Pd, Pt) Complexes

Shin Ichi Ohkoshi, Yasunori Ohba, Masamoto Iwaizumi, Seigo Yamauchi, Miharu Ohkoshi-Ohtani, Keiichi Tokuhisa, Masatsugu Kajitani, Takeo Akiyama, Akira Sugimori

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24 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)4569-4574
Number of pages6
JournalInorganic chemistry
Issue number16
Publication statusPublished - 1996 Dec 1

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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