Abstract
Three types of ferric tris(bipyridil) complexes appended a viologen, 1 3+, 2 3+, 3 3+, each having methylene, ethylene, and butylene spacer between ferric tris(bipyridil)- and viologen units, were synthesized and their photoinduced coloration properties were investigated in the thin poly(vinylalcohol) films. Upon photoirradiation, the colorless film of 1 3+ turned to red with increase in the absorption intensity around 530 nm, ascribing the ferrous tris(bipyridil) [Fe(II)bipy 3] complex. The coloration is interpreted in terms of the intramolecular electron transfer from the photogenerated viologen radical cation to the colorless Fe(III)bipy 3, since very little coloration of 4 3+ which has no viologen unit in a molecule was observed even in the presence of N, N′-dipropylviologen. Similar trends of 1 3+ were observed for 2 3+ and 3 3+. The order of absorption intensity around 530 nm is 1 3+> 2 3+> 3 3+ , indicating that the electron transfer from the photogenerated viologen radical cation to Fe(III)bipy 3 is achieved effectively for the complex with a short alkyl spacer.
Published Version
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