CB₄Se₅: a planar tetracoordinate carbon CB₄ core stabilized by peripheral Se/Se₂ bridges

Replacing one of the peripheral Se with a Se-2 bridge is an effective strategy to flatten the C-4v CB4Se4 cluster. The global minimum of CB4Se(5) contains one fan-shaped planar tetracoordinate carbon (ptC) CB4 core, possessing double 2 pi + 6 sigma aromaticity. The peripheral Se-2 bridge is dexterous and crucial for the stability of CB4Se5.