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Electronic Transitions in Conformationally Controlled Peralkylated Hexasilanes
Author(s) -
Kanazawa Yuki,
Tsuji Hayato,
Ehara Masahiro,
Fukuda Ryoichi,
Casher Deborah L.,
Tamao Kohei,
Nakatsuji Hiroshi,
Michl Josef
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201600633
Subject(s) - chemistry , nanotechnology , stereochemistry , crystallography , chemical physics , computational chemistry , materials science
The photophysical properties of oligosilanes show unique conformational dependence due to σ‐electron delocalization. The excited states of the SAS, AAS, and AEA conformations of peralkylated n ‐hexasilanes, in which the SiSiSiSi dihedral angles are controlled into a syn (S), anti (A), or eclipsed (E) conformation, were investigated by using UV absorption, magnetic circular dichroism (MCD), and linear dichroism spectroscopy. Simultaneous Gaussian fitting of all three spectra identified a minimal set of transitions and the wavenumbers, oscillator strengths, and MCD B terms in all three compounds. The results compare well with those obtained by using the symmetry‐adapted‐cluster configuration interaction method and almost as well with those obtained by time‐dependent density functional theory with the PBE0 functional. The conformational dependence of the transition energies and other properties of free‐chain permethylated n ‐hexasilane, n ‐Si 6 Me 14 , was also examined as a function of dihedral angles, and the striking effects found were attributed to avoided crossings between configurations of σσ* and σπ* character.