Structural chemistry of polycyclic heteroaromatic compounds. Part XI. Photoelectron spectra and electronic structures of tetracyclic hetarenes of the triphenylene type |
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Authors: | Rademacher P Heinemann C Jänsch S Kowski K Weiss M E |
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Affiliation: | 1. V. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, Kyiv, Ukraine;2. Institute of Organic Chemistry NAS of Ukraine, Kyiv, Ukraine;1. Université de Lorraine, UMR CNRS 7565, Structure et Réactivité des Systèmes Moléculaires Complexes, Equipe 5 (MIC), Campus Bridoux, rue du Général Delestraint, 57070 Metz Cedex, France;2. Université de Lorraine, UMR CNRS 7565, Structure et Réactivité des Systèmes Moléculaires Complexes, Equipe 3 (HECRIN), 1 Boulevard Arago, 57078 Metz Technopôle, France;3. Université de Lorraine, EA 4632-Laboratoire de Chimie et Physique Approche Multi-échelle des Milieux Complexes, 1 boulevard Arago, 57078 Metz Cedex 3, France;1. Department of Chemistry, Chemistry Institute for Functional Materials, Pusan National University, Kuemjeong-Ku, Busan 690-735, Republic of Korea;2. Department of Chemistry, The Catholic University of Korea, Bucheon 420-743, Republic of Korea |
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Abstract: | The UV photoelectron spectra of several tetracyclic heteroaromatic compounds (2-9) which are pi-isoelectronic with triphenylene (1) have been recorded and analysed making use of semiempirical AM1 and PM3 as well as ab initio/DFT B3LYP calculations. In one series of compounds (2-7), the peripheral benzene rings of 1 are successively substituted by thiophene rings that are either [b]- or [c]-annellated with the central benzene unit. In 2-7 only marginal shifts are found for most of the IPs of electrons. In the benzotrithiophenes 5-7, a systematic variation is displayed by IP(pi7). Compared to 1, the pi electron system of benzo[c]trithiophene (7) is approximately two times as much destabilized as in the isomers 5 and 6 with [b]annellated thiophene rings. The IP[n(S)] values of the thiophene derivatives 2-7 indicate that these orbitals are clearly destabilized relative to thiophene. The same holds for the n(O) orbital of the furane derivative 9 in comparison with that of furane. In 9, only the higher pi MOs (pi7-pi9) are destabilized whereas the lower levels (pi1-pi4) are stabilized, and those in between (pi5-pi6) remain essentially unshifted. In the pyrrole derivative 8, all pi MOs are substantially destabilized by about 0.5-1.6 eV relative to 1. |
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