Metallation of a cyclic chlorophyll hetero-dyad, and the optical properties of synthetic metallo-dyads

摘要

A cyclic chlorophyll hetero-dyad 1-H_2H_2, prepared by double ester linking of two structurally different pyropheophorbide-a moieties through 3-CH_2OCO-13~2' and 17~2-COOCH_2-3', was metallated with zinc and copper to give mono and di-metallated complexes 1-MH_2 or 1-H_2M and 1-MM. The metallation proceeded stepwise and regioselectively, with predominant synthesis of one of the two mono-metallated complexes 1-MH_2 as intermediate. The di-zinc complex produced, 1-ZnZn, was demetallated exclusively via the same mono-zinc complex 1-ZnH_2 as was the major intermediate during metallation. Visible and/or circular dichroism spectra of 1-H_2H_2, 1-MH_2, 1-H_2M, and 1-MM (M = Ni, Cu, or Zn) were measured in organic solvents. Intramolecular interaction of chlorin chromophores is discussed and compared with that of the corresponding monomeric species.