Peculiar Transformations in the CxHxP4-x (x = 0-4) Series

In the current work, we performed a systematic study of the CxHxP4-x (x = 0-4) series using an unbiased CK global minimum and low-lying isomers search for the singlet and triplet P4-C4H4 species at the B3LYP/6-31G** level of theory. The selected lowest isomers were recalculated at the CCSD(T)/CBS//B3LYP/6-311++G** level of theory. We found that the transition from a three-dimensional tetrahedron-like structure to a planar structure occurs at x = 3, where planar isomers become much more stable than the tetrahedral structures due to significantly stronger π bonds between carbon atoms in addition to increasing strain energy at the carbon atom in the tetrahedral environment.