Photochromic reactions of reversible coordination of perfluorothionaphthyl radical with flat Ni(II) dithiolate complexes

Abstract

The solutions of perfluoronaphthyl disulfide ((SC10F7)2 = (SNF)2) and flat 1,1′-dithiolate complexes Ni(II) (NiL2) in acetonitrile are shown to be photochromic systems. Absorption of the light pulse of an XeCl excimer laser (308 nm) by these solutions gives new absorption in the visible spectrum region which disappears in a millisecond time domain and the system returns to its original state. The cycle of phototransformations can be repeated many times without degradation of spectral changes in the solution. In the first stage, an excited disulfide molecule dissociates into two perfluorothionaphthyl radicals (•SC10F7 ≡ •SNF). These radicals coordinate at almost diffusion rate constant with NiL2 complexes to form the (SNF)•NiL2 radical complexes to which this new absorption belongs. The (SNF)•NiL2 complexes disappear due to dissociation resulting in a free •SNF radical that either transforms into disulfide upon recombination or reacts again with the initial NiL2 complex. The optical spectra of intermediates and the rate constants of all transformation stages of these species have been determined. © 2002 Elsevier Science B.V. All rights reserved.