Planar ten-membered 10-π-electron aromatic (CH)₅(XH)₅ {X = Ge, Sn} systems

Being monocyclic planar, benzene retains 6π Hückel aromatic backbone. However, for larger analogues, the repulsion between vicinal C-H bonds makes them nonplanar, as for [10]-annulene. Thus, on this basis, a planar 10-π-aromatic C₁₀H₁₀ is unreachable. A detailed structural comparison among the C₃H₃⁺, C₄H₄²⁺, C₅H₅^-, C₆H₆, C₇H₇⁺, C₈H₈²⁺, C₉H₉^-, and C₁₀H₁₀ systems supports that the repulsion between vicinal C-H bonds is the primary reason for the loss of planarity, despite the favorable aromatic electron count. In this respect, here we have discussed ten-membered monocyclic planar 10-π-aromatic, (CH)₅(XH)₅ {X = Si, Ge, Sn} systems, modeled by using DFT. From NBO analysis and the overall magnetic behavior it is shown that (CH)₅(GeH)₅, (CH)₅(SnH)₅ molecules are promising planar 10-π-aromatic system. Thus, such species represent plausible Hückel aromatic rings retaining a ten-membered backbone as discussed here, which may lead to the characterization of novel species expanding the chemistry of larger aromatic rings. We believe that the present study may open new avenues in the formation of 10-π-aromatic species. Graphical abstract Molecular modeling in quest of a planar 10-membered 10-π-electron aromatic system.