Chemistry Faculty Publications

Document Type

Article

Abstract

Photoinduced electron-transfer rate constants were measured for a series of binuclear metallopeptides consisting of a [Ru(bpy)(2)(cmbpy)](2+) electron donor tethered to a Co-III(NH3)(5) electron acceptor by an oligovaline peptide chain (bpy = 2,2'-bipyridine, cmbpy = 4-carboxy-4'-methyl-2,2'-bipyridine). These compounds were shown by H-1 NMR to adopt the conformational properties found within the individual strands of a beta-pleated sheet in both aqueous and methanol solutions. Emission lifetime measurements and HPLC product analysis show that the binuclear donor/acceptor compounds undergo photoinduced electron transfer (ET). The values of k(et) decrease with increasing donor/acceptor distance according to the expression k(et) = k' exp[-beta(r(-)r(0))]. A distance attenuation factor of beta = 1.1 +/- 0.4 Angstrom(-1) is seen both in H2O at 298 K and in an ethanol-methanol glass at 77 K. The ET kinetics obtained at 77 K for 1-3 were single exponential, indicating that the compounds maintain a unique donor/acceptor separation and do nor exist within multiple conformations. The similarity in behavior obtained under very different solvent conditions indicates that the electronic coupling term dominates the distance dependence of k(et).

Publication Date

4-1998

Publication Title

Inorganic Chemistry

Volume

37

Issue

8

Start Page No.

1900

End Page No.

1905

DOI

10.1021/ic970369y

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Chemistry Commons

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