| Autor: |
Yuen JM; Department of Chemistry , Washington University , St. Louis , Missouri 63130-4889 , United States., Diers JR; Department of Chemistry , University of California , Riverside , California 92521-0403 , United States., Alexy EJ; Department of Chemistry , North Carolina State University , Raleigh , North Carolina 27695-8204 , United States., Roy A; Department of Chemistry , Washington University , St. Louis , Missouri 63130-4889 , United States., Mandal AK; Department of Chemistry , Washington University , St. Louis , Missouri 63130-4889 , United States., Kang HS; Department of Chemistry , Washington University , St. Louis , Missouri 63130-4889 , United States., Niedzwiedzki DM; Photosynthetic Antenna Research Center , Washington University , St. Louis , Missouri 63130-4889 , United States., Kirmaier C; Department of Chemistry , Washington University , St. Louis , Missouri 63130-4889 , United States., Lindsey JS; Department of Chemistry , North Carolina State University , Raleigh , North Carolina 27695-8204 , United States., Bocian DF; Department of Chemistry , University of California , Riverside , California 92521-0403 , United States., Holten D; Department of Chemistry , Washington University , St. Louis , Missouri 63130-4889 , United States. |
| Abstrakt: |
Panchromatic absorbers that have robust photophysical properties enable new designs for molecular-based light-harvesting systems. Herein, we report experimental and theoretical studies of the spectral, redox, and excited-state properties of a series of perylene-monoimide-ethyne-porphyrin arrays wherein the number of perylene-monoimide units is stepped from one to four. In the arrays, a profound shift of absorption intensity from the strong violet-blue (B y and B x ) bands of typical porphyrins into the green, red, and near-infrared (Q x and Q y ) regions stems from mixing of chromophore and tetrapyrrole molecular orbitals (MOs), which gives multiplets of MOs having electron density spread over the entire array. This reduces the extensive mixing between porphyrin excited-state configurations and the transition-dipole addition and subtraction that normally leads to intense B and weak Q bands. Reduced configurational mixing derives from moderate effects of the ethyne and perylene on the MO energies and a more substantial effect of electron-density delocalization to reduce the configuration-interaction energy. Quantitative oscillator-strength analysis shows that porphyrin intensity is also shifted into the perylene-like green-region absorption and that the ethyne linkers lend absorption intensity. The reduced porphyrin configurational mixing also endows the S 1 state with bacteriochlorin-like properties, including a 1-5 ns lifetime. |
