Why do disilanes fail to fluoresce?

0376088 - ÚOCHB 2012 RIV CZ eng J - Journal Article
MacLeod, M. K. - Michl, Josef
Why do disilanes fail to fluoresce?
Collection of Czechoslovak Chemical Communications. Roč. 76, č. 12 (2011), s. 2085-2116. ISSN 0010-0765
Institutional research plan: CEZ:AV0Z40550506
Keywords : excited states * relaxed excited state * excited state potential energy minima * molecular orbitals
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 1.283, year: 2011

In contrast to longer peralkylated oligosilanes, many of which fluoresce efficiently, disilanes and trisilanes exhibit no detectable fluorescence even at low temperatures. This is especially striking in the case of disilanes, whose S-1-S-0 transition is quite strongly allowed, and which must have very efficient electronic excited state deactivation mechanisms. To identify them, we examine the lowest excited singlet state potential energy surface S-1 of Si2Me6 with TDDFT (B3LYP/TZVP, PBE0/TZVP and BHLYP/TZVP) and ab initio (RICC2/TZVP and RIADC(2)/TZVP) methods and identify several shallow minima and nearby funnels. Relaxed excited state structures show strong valence rehybridization relative to the ground state, allowing optimal accomodation of the simultaneous presence of a negative and a positive charge in their Lewis structures. Efficient decay pathways and relations to longer oligosilanes are discussed.
Permanent Link: http://hdl.handle.net/11104/0208585