In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Marcin Ptaszek of the Department of Chemistry at University of Maryland, Baltimore County, is developing an understanding of roles of electronic coupling on photochemical properties in biomimetic arrays for solar energy conversion. Natural photosynthesis remains the main inspiration for designing artificial systems for solar energy conversion. The arrays of strongly interacting pigments are the key components in the initial process of photosynthesis, i.e. solar radiation harvesting and initial charge separation. In order to gain a deeper understanding of the fundamental processes in photosynthesis and to establish the key design principles for development of artificial solar energy conversion systems, with efficiency comparable to (or better than) that observed for photosynthesis, the series of model arrays are prepared and characterized. This project combines advanced organic synthesis, spectroscopy, photochemistry and computational chemistry, therefore provides diverse educational opportunities for students at various levels. Special emphasis is devoted to involve students from underrepresented groups in science, and students from high schools.
Excitonically coupled photo- and redox active molecules are the key components in photosynthetic arrays responsible for light harvesting and charge separation. The extent in which excitonic coupling determines the photophysical mechanisms underlying the highly efficient charge separation in photosynthetic arrays, and therefore its potential benefits for artificial photosynthesis, is not fully understood. The goal of the proposed research is to determine structure-photophysics relationships in excitonically coupled hydropoprhyrin arrays in order to develop an understanding of the role of an excitonic coupling in natural and artificial solar energy conversion systems. A series of dyads, composed of hydroporphyrins, i.e. synthetic analogs of photosynthetic pigments, featuring various modes of electronic interactions, are prepared, and the effect of varied electronic coupling on the physical properties of resulting arrays are determined. Subsequently, it is determined to what extent strength and mode of electronic coupling in hydroporphyrin dyads affect the energy and electron transfer dynamics in multicomponent arrays. Four specific aims are realized: (1) Determination of how molecular geometry and type of electronic interactions affect photophysical properties in excitonically coupled hydroporphyrin dyads; (2) Determination of effects of redox properties, metalation, and vibrational properties of hydroporphyrins as well as electronic asymmetry on photochemical properties of excitonically coupled dyads; (3) Determination of the role of excitonic coupling in electron transfers dynamics; and (4) Determination of energy and electron transfer dynamics in bio-inspired reaction center models.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
