Computational studies on C24H8, C28H12, and C32H16 isomers in which the cubane, pentaprismane, or hexaprismane cages are linked by four CC bonds

Quantum-chemical calculations on C24H8, C28H12, and C32H16 isomers in which the cubane, pentaprismane, or hexaprismane cages are linked by four CC bonds have been performed using density functional theory (DFT) method. The geometric structures, energies, vibrational frequencies, and vertical ionization energy as well as vertical electron affinity of various isomers have been obtained at the B3LYP/6-31G∗∗ level of theory. Meanwhile, the present paper has also computed the enthalpies of formation for different isomers so as to evaluate their stability from a thermodynamic point of view. There exists two different isomers for C28H12 and C32H16 in which the prismane (pentaprismane or hexaprismane) cages are parallel or perpendicular to each other. It has been concluded that the isomer in which the prismane (pentaprismane or hexaprismane) cages are perpendicular is more stable and has relatively smaller heat of formation.