Accounting for the differences in the structures and relative energies of the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I4 2+, the Se-I pi-bonded Se2I4 2+, and their higher-energy isomers by AIM, MO, NBO, and VB methodologies.
Brownridge S, Crawford MJ, Du H, Harcourt RD, Knapp C, Laitinen RS, Passmore J, Rautiainen JM, Suontamo RJ, Valkonen J. Inorg Chem. 2007 Feb 5; 46(3):681-99.