An AB Initio Molecular Orbital Study of Neutral Isomers of Silanaphthalenes, Silaanthracenes, and Silaphenanthrenes

Abstract

Ab initio molecular orbital calculations at HF/6-31G* and RMP2-FC/6-31G* levels of theory for geometry optimization and MP4(SDQ)/6-31G* for a single point total energy calculation are reported for three isomers of silanaphthalene, four isomers of silaanthracene, and seven isomers of silaphenanthrene. According to these calculations, 2-silanaphthalene is only 0.4 kcal mol−1 more stable than 1-silanaphthalene. The isomer having Si atom at ring junction is calculated to be 5.8 kcal mol−1 less stable. 1-Silaanthracene is the most stable isomer of silaanthracenes. 2-Silaanthracene and 9-silaanthracene are 0.5 and 1.6 kcal mol−1 less stable than 1-silaanthracene respectively. The isomer with an Si atom at ring junction is 6.7 kcal mol−1 less stable. 1-Silaphenanthrene is the most stable isomer of silaphenanthrenes. 2-Sila-, 4-sila-, and 3-silaphenanthrene are 1.1–2.2 kcal mol−1 less stable than the 1-sila-isomer. Other silaphenanthrenes are less stable by 4.1–6.1 kcal mol−1.