Starting from its measured structure, the electronic structures and optical absorptions of CdSe single source precursor, cadmium bis(diselenophosphinate) (CSP), have been studied by means of density functional theory calculations. In contrast to covalent bonding in ligand-free cadmium selenide, the Cd-Se bonds in CSP are featured by the coordination of the 4p electrons of Se atoms, resulting in low net charge on Cd and blue shifted electron transitions. The ligands not only stabilize the CdSe core but also affect the HOMO-LUMO transition. Computations were extended to the corresponding ZnSe and CdS complexes and came to similar conclusions. (C) 2013 Elsevier B.V. All rights reserved.