Electronic Excitations of 1,4-Disilyl-Substituted 1,4-Disilabicycloalkanes: A MS-CASPT2 Study of the Influence of Cage Size

• DOI: 10.1021/jp070010n
• Publication Date: 2007-03-17T10:46:21Z
• Authors: Niclas Sandström; Mari Carmen Piqueras; Henrik Ottosson; Raül Crespo
• Keywords: Cage

We present a multistate complete active space second-order perturbation theory computational study aimed to predict the low-lying electronic excitations of four compounds that can be viewed as two disilane units connected through alkane bridges in bicyclic cage. The analysis has focused on 1,4-disilyl-1,4-disilabicyclo[2.2.1]heptane (1a), 1,4-bis(trimethylsilyl)-1,4-disilabicyclo[2.2.1]heptane (1b), 1,4-disilyl-1,4-disilabicyclo[2.1.1]hexane (2a), and 1,4-bis(trimethylsilyl)-1,4-disilabicyclo[2.1.1]hexane (2b). aim been find out nature lowest with significant oscillator strengths investigate how cage size affects excitation energies transitions. Two different substituents terminal silicon atoms (H CH3) were used order end group effects. calculations show allowed are same character found disilanes but now red-shifted. As is reduced from 1,4-disilabicyclo[2.2.1]heptane 1,4-disilabicyclo[2.1.1]hexane, Si···Si through-space distance decreases approximately 2.70 2.50 Å transitions red-shifted by up 0.9 eV, indicating increased interaction between Si−Si bonds. first ionization potential, which corresponds σ orbitals, lower 1b 2b than Si2Me6 1.2 respectively. Moreover, 2b, have methyl at Si atoms, slightly analogous species 1a 2a.