New heteroleptic paddlewheel complexes cis-[Rh2(μ-form)2(μ-np)2][BF4]2, where form = p-ditolylformamidinate (DTolF) or p-difluorobenzylformamidinate (F-form) and np = 1,8-napthyridyine, and cis-Rh2(μ-form)2(μ-npCOO)2 (npCOO– = 1,8-naphthyridine-2-carboxylate), were synthesized and characterized. The complexes absorb strongly throughout the ultraviolet (300 nm, ε = 20,300 M−1cm−1) and visible regions (640 nm, ε = 3,500 M−1cm−1), making them potentially useful new dyes with panchromatic light absorption for solar energy conversion applications. Blocking the axial positions in is-Rh2(μ-form)2(μ-npCOO)2 results in longer singlet and triplet lifetimes, and the the energy of the latter was determined from triplet energy transfer quenching studies. The excited state oxidation potentials of the triplet states of complexes are estimated to be –0.5 V vs Ag/AgCl, such that they are able to reduce electron acceptors and inject electrons into TiO2 upon excitation with low energy light.

Excited states of new bimetallic complexes for solar energy applications

255th National Meeting (2018)

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