Interfacing High-Energy Charge Transfer States to a Near-IR Sensitizer for Efficient Electron Transfer upon Near-IR Irradiation.

Novel push-pull systems comprised of triphenylamine-tetracyanobutadiene, a high-energy CT species is linked to a near-IR sensitizer, azaBODIPY, for promoting excited state CS. These new systems revealed panchromatic absorption due to combined effect of intramolecular CT, and near-IR absorbing azaBODIPY. Using electrochemical and computational studies, energy levels were established to visualize excited state events. Fs-TA studies were performed to monitor excited state CT events. From target analysis, the effect of solvent polarity, number of linked CT entities, and excitation wavelength dependence in governing the lifetime of CS states was established. Electron exchange between two TPA-TCBD entities in 3 seem to prolong lifetime of the CS state. Importantly, we have been successful in demonstrating efficient CS upon both high-energy CT and low-energy near-IR excitations, signifying importance of these push-pull systems for optoelectronic applications operating in the wide optical window.