Energy Transfers in Monomers, Dimers, and Trimers of Zinc(II) and Palladium(II) Porphyrins Bridged by Rigid Pt-Containing Conjugated Organometallic Spacers

Abstract

A series of linear monomers (spacer-M(P)), dimers (M(P)-spacer-M'(P)), and trimers (M(P)-spacer-M'(P)-spacer-M(P)) of spacer/metalloporphyrin systems (M' = Zn, M = Zn, Pd, P = porphyrin, and spacer = trans-C(6)H(4)C[triple bond]CPtL(2)C[triple bond]CC(6)H(4)- (L = PEt(3))) including mixed metalloporphyrin compounds, were synthesized and characterized. The S(1) and T(1) energy transfers Pd(P)*-->Zn(P) occur with rates of approximately 2 x 10(9) s(-1), S(1), and 0.15 x 10(3) (slow component) and 4.3 x 10(3) s(-1) (fast component), T(1). On the basis of a literature comparison with a related dyad, the Pt atom in the conjugated chain slows down the transfers. The excitation in the absorption band of the trans-C(6)H(4)C[triple bond]CPtL(2)C[triple bond]CC(6)H(4)- spacer in the 300-360 nm range also leads to T(1) energy transfer (spacer* --> M(P); M = Zn, Pd) with rates of 10(4) s(-1).