Guest to framework photoinduced electron transfer in a cobalt substituted RWLC-2 metal organic framework

Abstract

Photoinduced electron transfer (PET) between donors and acceptors in porous materials is a key element in the development of light harvesting applications. Metal organic frameworks (MOFs) are ideal materials for PET processes due to their tunable pore size and diversity in framework building units. Here, PET between excited [Ru(2,2′-bipyridine)₃]²⁺ (RuBpy) and Co-carboxylate clusters composing the metal building blocks of a RWLC-2 metal organic framework is described. The lifetime of the RuBpy decreases from ∼600 ns in deaerated solution to 9.5 ns (k_ET ∼ 1 × 10⁸ s⁻¹) when encapsulated within CoRWLC-2. The decrease in lifetime is attributed to PET between the ³MLCT of RuBpy to the Co ion cluster composing the MOF building blocks. A fit of the lifetime vs. temperature data to the semi-empirical Marcus equation gives a reorganizational energy of 1.6 eV and an electronic coupling factor (H_AB) of 0.006 eV.