Based on extensive first-principles theory calculations, we present the possibility of an endohedral charge-transfer complex, Cs Ca@B37 (I), which contains a 3D aromatic fullerene-like Cs B373 (II) trianion composed of interwoven boron double chains with twelve delocalized multicenter p bonds (12 mc–2e p, m = 5, 6) over a r skeleton, completing the Bn q borospherene family (q = n 40) in the size range of n = 36–42.
