Electronic Transitions in Conformationally Controlled Tetrasilanes with a Wide Range of SiSiSiSi Dihedral Angles

0431050 - ÚOCHB 2015 RIV DE eng J - Journal Article
Tsuji, H. - Fogarty, H. A. - Ehara, M. - Fukuda, R. - Casher, D. L. - Tamao, K. - Nakatsuji, H. - Michl, Josef
Electronic Transitions in Conformationally Controlled Tetrasilanes with a Wide Range of SiSiSiSi Dihedral Angles.
Chemistry - A European Journal. Roč. 20, č. 30 (2014), s. 9431-9441. ISSN 0947-6539. E-ISSN 1521-3765
Institutional support: RVO:61388963
Keywords : conformational effects * electronic spectra * SAC-CI calculations * silicon * UV/Vis spectroscopy
Subject RIV: CC - Organic Chemistry
Impact factor: 5.731, year: 2014

Unlike p-electron chromophores, the peralkylated n-tetrasilane sigma-electron chromophore resembles a chameleon in that its electronic spectrum changes dramatically as its silicon backbone is twisted almost effortlessly from the syn to the anti conformation (changing the SiSiSiSi dihedral angle omega from 0 to 180 degrees). A combination of UV absorption, magnetic circular dichroism (MCD), and linear dichroism (LD) spectroscopy on conformationally controlled tetrasilanes 1-9, which cover fairly evenly the full range of angles omega, permitted a construction of an experimental correlation diagram for three to four lowest valence electronic states. The free chain tetrasilane n-Si4Me10(10), normally present as a mixture of three enantiomeric conformer pairs of widely different angles w, has also been included in our study. The spectral trends are interpreted in terms of avoided crossings of 1B with 2B and 2A with 3A states, in agreement with SAC-CI calculations on the excited states of 1-7 and conformers of 10.
Permanent Link: http://hdl.handle.net/11104/0235750