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Title: The effect of structural changes on charge transfer states in a light-harvesting carotenoid-diaryl-porphyrin-C{sub 60} molecular triad

We present a detailed study of charge transfer (CT) excited states for a large number of configurations in a light-harvesting Carotenoid-diaryl-Porphyrin-C{sub 60} (CPC{sub 60}) molecular triad. The chain-like molecular triad undergoes photoinduced charge transfer process exhibiting a large excited state dipole moment, making it suitable for application to molecular-scale opto-electronic devices. An important consideration is that the structural flexibility of the CPC{sub 60} triad impacts its dynamics in solvents. Since experimentally measured dipole moments for the triad of ∼110 D and ∼160 D strongly indicate a range in structural variability in the excited state, studying the effect of structural changes on the CT excited state energetics furthers the understanding of its charge transfer states. We have calculated the variation in the lowest CT excited state energies by performing a scan of possible variation in the structure of the triad. Some of these configurations were generated by incrementally scanning a 360° torsional (dihedral) twist at the C{sub 60}-porhyrin linkage and the porphyrin-carotenoid linkage. Additionally, five different CPC{sub 60} conformations were studied to determine the effect of pi-conjugation and particle-hole Coulombic attraction on the CT excitation energies. Our calculations show that configurational changes in the triad induces a variation of ∼0.6 eVmore » in CT excited state energies in the gas-phase. The corresponding calculated excited state dipoles show a range of 47 D–188 D. The absorption spectra and density of states of these structures show little variation except for the structures where the porphyrin and aryl conjugation is changed.« less
Authors:
 [1] ; ;  [2] ;  [1] ;  [3]
  1. Computational Science Program, University of Texas at El Paso, El Paso, Texas 79968 (United States)
  2. Department of Physics, The University of Texas at El Paso, El Paso, Texas 79968 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
22304397
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 20; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTRA; CAROTENOIDS; DENSITY; DIPOLE MOMENTS; ELECTRONIC EQUIPMENT; EV RANGE; EXCITATION; EXCITED STATES; FULLERENES; PARTICLES; PORPHYRINS; SOLVENTS