Point-Dipole Approximation of the Exciton Coupling Model Versus Type of Bonding and of Excitons in Porphyrin Supramolecular Structures

• Published in: Chemistry : a European journal Vol. 7; no. 13; pp. 2733 - 2737
• Main Authors: Ribó, Josep M., Bofill, Josep M., Crusats, Joaquim, Rubires, Raimon
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag GmbH 02.07.2001; WILEY‐VCH Verlag GmbH
• Subjects: electronic structure; porphyrinoids; solid-state chemistry; UV/Vis spectroscopy
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/1521-3765(20010702)7:13<2733::AID-CHEM2733>3.0.CO;2-Q

The application of the exciton coupling model to interacting porphyrin chromophores is discussed. Covalently bonded systems and ionic or electrostatically bonded homoassociates require different orientations of the transition dipole moments in order to explain the experimental results: according to the symmetry of the assembly for covalently bonded porphyrins, and assuming isolated chromophores for ionic bonded porphyrins. Further, for covalently bonded systems, an extended exciton coupling has been demonstrated, but the ionic systems are in agreement with non‐extended couplings. The relation of these facts to a molecular description of solid‐state Wannier–Mott or Frenkel excitons is briefly discussed. For the design and supramolecular engineering of nanodevices it is necessary to have simple reliable models that relate the structural and electronic models used in organic chemistry with those used in chemical physics and solid‐state physics and chemistry. The application of the point‐dipole approximation of the exciton coupling model and its relation to the solid‐state type of excitons is described.