meso-to-meso Sulfide- and Disulf­ide-Bridged Subporphyrin Dimers

Abstract

Treatment of meso-chlorosubporphyrin with controlled equivalents of Na₂S·9H₂O in DMF led to the formation of either meso-to-meso sulfide (S)-bridged dimer 4 or disulfide (SS)-bridged subporphyrin dimer 6. S-bridged dimer 4 displayed a split Soret-like band and a large Stokes shift and became a fully delocalized one-quantum system in the S₁ state, as indicated by femtosecond transient absorption anisotropy measurements and theoretical calculations. Contrastingly, SS-bridged dimer 6 showed a broad but nonsplit Soret-like band, no fluorescence, and very fast S₁ decay with a lifetime of 4 ps, which indicated the presence of a rapid decay channel.

meso-to-meso S-bridged and SS-bridged dimers 4 and 6 are prepared by S_NAr reaction of meso-chlorosubporphyrin. Dimer 4 displays a split Soret-like band and a large Stokes shift, whereas dimer 6 shows weaker interchromophoric interaction. Dimer 4 becomes a one-quantum system in the S₁ state, whereas the S₁ state of 6 displays very fast decay to the ground state with a lifetime of 4 ps.

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