Abstract
The stability and electronic structure of B(7)Si(3) (q) (q = +, 0, -, 2- and 3-), Li(3)B(7)Si(3) and Li(3)B(10)H(3) clusters have been investigated through a comprehensive isomer search, with a focus on the perfect triangular planar isomer T(+) of B(7)Si(3) (+). Despite its double aromaticity, this form is thermodynamically unstable. Two strategies for the stabilization of the triangular form are proposed: (i) sequential addition of σ electrons and (ii) incorporation of Li atoms to reduce excessive negative charge. The former reveals that the addition of up to four electrons gradually improves its stability, with T(2-) being the most favourable isomer in this charged state. The latter strategy leads to the star form emerging as a global minimum of the ternary Li(3)B(7)Si(3) cluster, which is significantly more stable. To elucidate the origin of these stabilizations, ring current maps and AdNDP, ELF(σ) and ETS-NOCV analyses were employed. Results show a shift from the dominant σ aromaticity in T(+) to a more balanced σ-π aromatic character in Li(3)B(7)Si(3), akin to benzene. The AdNDP analysis reveals that T(+) possesses four σ delocalized bonds, whereas Li(3)B(7)Si(3) contains only three, serving as one of the indicators of reduced σ-delocalization. ELF(σ) analysis further revealed an enhanced peripheral σ delocalization in Li(3)B(7)Si(3), highlighting the critical role of edge-localized electrons in stabilizing planar aromatic clusters.