From Ordinary to Blue Emission in Peralkylated n-Oligosilanes: The Calculated Structure of Delocalized and Localized Singlet Excitons

0438225 - ÚOCHB 2015 RIV US eng J - Journal Article
MacLeod, M. K. - Michl, Josef
From Ordinary to Blue Emission in Peralkylated n-Oligosilanes: The Calculated Structure of Delocalized and Localized Singlet Excitons.
Journal of Physical Chemistry A. Roč. 118, č. 45 (2014), s. 10538-10553. ISSN 1089-5639. E-ISSN 1520-5215
Institutional support: RVO:61388963
Keywords : polysilane high polymers * density functional methods * molecular orbital methods
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 2.693, year: 2014

Excited singlet state structures believed to be responsible for the Franck-Condon-allowed and the strongly Stokes-shifted (blue) emissions in linear permethylated oligosilanes (SinMe(2n+2)) have been found and characterized with time-dependent density functional (TD-DFT) methods for chain lengths 4 <= n <= 16. For chain lengths with n > 7, the S1 relaxed structures closely resemble the S0 equilibrium structures where all valence angles are tetrahedral and all backbone dihedral angles are transoid. At chain lengths with n < 8 more strongly distorted structures with one long Si-Si bond built from silicon 3p orbitals are encountered. The large Stokes shift is due more to a large destabilization of the ground state than the relaxation in the S1 excited state. For n > 7, both types of minima were located, exactly reproducing the borderline between the large-radius and the small-radius self-trapped excitons known from experiments.
Permanent Link: http://hdl.handle.net/11104/0241682