The continued development of solar sources of energy necessitates the design of coordination frameworks capable of inducing charge separation (CS). We present a bioinspired approach that leverages the relationship between the coordination and redox chemistry of copper to promote CS in the excited state. Twisted intramolecular charge transfer (TICT) ligands were prepared which could stabilize copper in two oxidation states and are capable of undergoing photoinduced conformational changes that may be transferred to a bound CuI ion. These frameworks intend to drive conformational changes at CuI from tetrahedral to square pyramidal, favoring the formation of CuII and consequently facilitating CS in the excited state from CuI to a ligand radical cation. These CuCl(dpaaR) (dpaaR = dipicolylaminoacetophenone) complexes have been structurally characterized by X-ray diffraction, NMR, EPR, and IR spectroscopies. Their electronic structures were also examined by cyclic voltammetry and UV-Vis absorption and emission spectroscopies. Excited state dynamics were investigated by fs and ns optical transient absorption and photoluminescence spectroscopies. The presence of a TICT chromophore and an o-chelate capable of relaying the conformational dynamics of the chromophore to CuI were essential to observing CS. These data suggest that linking the conformational reorganization of a ligand to the coordination geometry of copper enables improved CS in copper coordination complexes.

Improved charge separation through conformational control of a copper coordination complex

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