title: Electronic Structure and Absorption Properties of Strongly Coupled Porphyrin-Perylene Arrays.
abstract: Porphyrin-perylene arrays are ideal candidates for light-harvesting systems capable of panchromatic absorption. In this work, we employ density functional theory (DFT) and time-dependent DFT to investigate the unique UV-vis absorption properties exhibited by a series of ethynyl-linked porphyrin-perylene arrays that were previously synthesized and characterized spectroscopically [Chem. Commun. 2014, 50, 14512-5]. We find that the ethynyl linker is responsible for strong electronic coupling of porphyrin and perylene subunits in these systems. Additionally, these arrays exhibit a low barrier to rotation around the ethynyl linker (<1.4 kcal/mol per one perylene substituent), which results in a wide range of molecular conformations characterized by different porphyrin-perylene dihedral angles being accessible at room temperature. The best match between the calculated and experimental UV-vis spectra is obtained by averaging the calculated UV-vis spectra over the range of conformations defined by the porphyrin-perylene dihedral angles. Finally, our calculations suggest that the transitions in the lower energy region (550-750 nm) can be assigned to the excitations originating from the porphyrin subunit; the mid-energy region transitions (450-550 nm) are assigned to the perylene-centered excitations, while the high-energy transitions (350-450 nm) involve contributions from both porphyrin and perylene subunits.
authors: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors: Judah S
authors: JS
authors: High
authors: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors: Kyle A
authors: KA
authors: Virgil
authors: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors: Elena
authors: E
authors: Jakubikova
mesh_terms: D004583:Electrons; D004735:Energy Transfer; D008027:Light; D008968:Molecular Conformation; D015394:Molecular Structure; D010569:Perylene / Q000737:chemistry*; D010777:Photochemistry; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D011166:Porphyrins; D010569:Perylene