Pyrene-Based Light-Harvesting Antenna Molecules

Light-harvesting antenna systems (AS) with multiple light-absorbing chromophores play a vital role in absorbing sunlight and transferring the excitation energy to the reaction centers during the photosynthesis process. Learning from nature, a set of simple and artificial pyrene-based light-harvesting antenna systems have been designed and re-examined from the self-developing chemical intermediates, via combining the electron-donating 4,4-dimethoxy-triphenylamine moieties as the antenna for absorbing energy donors and transferring to the reaction center. These pyrene-based light-harvesting antenna systems exhibit a positive correlation between the molar absorption coefficient (epsilon), enhanced photoluminescence efficiency with unchanged emission peak, and two-photon absorption cross-section with an increasing number of antenna of TPA-OMe moieties in solution. Moreover, the excited-state dynamics of these AS indicated that the coexistence of the charge transfer (CT) state and charge separation (CS) state plays a significant role in affecting the emission behavior. The short-lived CS state was affected by the increased TPA-OMe moieties and low polar solvent, which can boost the CS decay to charge recombination (CR), resulting in enhanced emission. On the contrary, the long-lived CS state would overwhelm the CT state in high polar solvent or pyrene-based antenna molecules containing one or two TPA-OMe units.