THEORETICAL-STUDY OF THE [AL,H,C,N](+) POTENTIAL-ENERGY SURFACE COMBINED WITH EXPERIMENTAL INVESTIGATIONS ON AL(HCN)(+)

The prospect of interconversion of HCN, attached to Al+, into HNC has been studied in a combined experimental - theoretic al approach. Low-pressure equilibrium measurements at 298 K between Al(H2O)(+) and Al(HCN)(+) in a Fourier-transform ion cyclotron resonance mass spectrometer lead to the determination of the bond dissociation energy BDE(Al+-HCN) = 28 +/- 6 kcal/mol. Comparison with the theoretically derived values of BDE(Al+-HCN) 29.1 kcal/mol (0 K) and 28.6 kcal/mol (298 K), obtained with a refined GAUSSIAN-2 (G2) procedure, shows very good agreement. Ln addition, the G2 stabilities, relative to separated Al+ and HCN, of the following [Al,H,C,N](+) isomers have been computed (in kcal/mol): Al(HCN)(+) (1), -29.1; Al(HNC)(+) (2), -14.4; H-Al+-CN (3), +11.7; H-Al+-NC (4), +8.8. The interconnecting transition structures have been located, and the possible isomerization pathways will be discussed.