As a follow-up to the previous post, if I run a HF/6-31G* calculation on the formate anion, the HOMO matches the Huckel HOMO and the LUMO macthes the Huckel LUMO. Douglas E. Stack Assistant Professor Department of Chemistry University of Nebraska at Omaha Omaha, NE 68182-0109 (402) 554-3647 (402) 544-3888 (fax) destack ( ( at ) ) unomaha.edu