<i>Ab initio</i> and DFT studies on the lithium and hydrogen bonded complexes of LiF and HF with σ and <i>n</i>+σ donors

Abstract

<i>Ab initio</i> calculations at the Hartree Fock and MP2 levels and DFT computations at B3LYP level with 6-31 ++G(<i>d,p</i>) basis set reveals that LIF forms complexes With cyclopropane, oxirane and thiirane similar to HF ; but unlike HF complexes , LiF complexes have additional stable forms. LIF/HF complexes of cyclotrisilane are reported anew and these complexes are found to be weaker than the cyclopropane complexes. Calculations confirm earlier observations on HF complexes and predict that LiF complexes are stronger.

Due to bent nature of the C-C bonds, the above bases form much shorter Li and H bonds with LiF and HF. Unusual shortening of LiF bonds in the weaker complexes of oxirane and thiirane suggests the possibility of antilithium bonds. NBO analysis reveals that in cyclopropane and cyclotrisilane complexes, σ (C-C) and σ (Si-Si) electrons are donated respectively; while oxirane prefers a mixed donation of n_σ (O) and n_π (O) electrons , thiirane donates only its n_π (S) electron.