title: Excited states of porphyrin isomers and porphycene derivatives: a SAC-CI study.
abstract: Excited states of free-base porphyrin isomers, porphycene (Pc), corrphycene (Cor), and hemiporphycene (hPc), were studied by the Symmetry-Adapted Cluster (SAC)/SAC-Configuration Interaction (CI) method. The absorption peaks of the porphyrin isomers were assigned on the basis of the SAC-CI spectra. The X, Y, X', and Y' bands of the porphyrin isomers, which have weak intensities, are identified. The differences in the Q-band absorptions among the isomers were clearly explained by the four-orbital model. In Cor and hPc, the wave function of the B-band corresponds to the mixture of the four-orbital excitations and the optically forbidden excitation of free-base porphin (P), due to the molecular symmetry lowering in the isomers. The B-band character is described by the five-orbital model in Pc and the six-orbital model in Cor and hPc. Two tetrazaporphycenes and two ring-extended (dibenzo) porphycenes were designed, and the Q-band transition moment was successfully controlled. These examples show that the control of the four-orbital energy levels is the guiding principle for pigment design in porphyrin compounds.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
authors.forename: Jun-ya
authors.initials: JY
authors.lastname: Hasegawa
authors.forename: Koji
authors.initials: K
authors.lastname: Takata
authors.forename: Tomoo
authors.initials: T
authors.lastname: Miyahara
authors.forename: Saburo
authors.initials: S
authors.lastname: Neya
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Frisch
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakatsuji
mesh_terms: D004563:Electrochemistry; D007536:Isomerism; D011166:Porphyrins / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D011166:Porphyrins; C051407:porphycene