Theoretical study of reaction channels for the weakly bound complex systems created with HF, CO 2 , and various amines

This investigation conducted reaction channels of weakly bound complexes CO 2 …HF, CO 2 …HF…NH 3 , CO 2 …HF…NH 2 CH 3 , CO 2 …HF…NH(CH 3 ) 2 , and CO 2 …HF…N(CH 3 ) 3 systems, using the Gaussian 98 package at the B3LYP/6‐311++G (3df,2pd) level. The syn‐fluoroformic acid or syn‐fluoroformic acid plus NH 3 or amine conformers are more stable than the related anti‐fluoroformic acid or anti‐fluoroformic acid plus NH 3 or amine conformers. However, the above‐mentioned weakly bound complexes are more stable than both the related syn‐ and anti‐type fluoroformic acid or acid plus NH 3 or amine conformers and their related decomposed into CO 2 + HF or CO 2 + NHR 3 F (RH, CH 3 ) combined molecular systems. Five reaction channels of the weakly bound complexes exist. Each channel includes weakly bound complexes and their related above‐mentioned systems. Moreover, each reaction channel contains two transition states. The transition state between the weakly bound complex and anti‐fluoroformic acid type structure (T 13 ) is significantly higher than that of internal rotation (T 23 ) between syn‐ and anti‐FCO 2 H (or FCO 2 H…NR 3 ) structures. However, the above‐mentioned T 13 can significantly decrease its energy by adding the third molecule NH 3 or NR 3 (RH or CH 3 ). The more CH 3 that is substituted in NR 3 of the reaction channel, the lower the activation energy of the transition state in the system is affected. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005