LAUSR

Abstract Systematic density functional theory (DFT) calculations and natural bond orbital (NBO) analyses were carried out to understand the reason behind the disappearance of linear and slightly-bent isomer of germasilaallenes and the bond-stretch phenomenon of their cyclic isomer, unusual electronic properties of highly-bent isomers of germasilaallenes. Our results show that in contrast to trisilaallene and trigermaallene, 1,3-digermasilaallene and 1-germadisilaallene do not have stable cyclic isomers, due to increased ring strains. DFT calculations and NBO analyses indicate that the stability of highly-bent isomers of germasilaallenes arise from three parts: p(terminal) → p(central) donor–acceptor interaction, p(terminal)-p(terminal) partial overlapping and the aromatic delocalization along the ring. Different from mono- and di-germasilaallene, DFT and CCSD calculations indicate that there is no stable minimum along the first half, from 180° to 90.0°, of the potential energy surface of trigermasilaallene. For trigermasilaallene, for bending angle α > 120.0°, π-π* orbital delocalization effect dominates the stability and when α