Quantum Chemical Study On The Weak Interaction Of Nitric Oxide Dimer

Weak interactions between molecules (also called unbounded interactions) are widespread in nature. Particularly in the lives , weak interactions plays a pivotal role. Nitric oxide is a free radical molecule, experimentations shows that it can form a dimer by the interaction between molecules. Intermolecular weak interaction studies of nitric oxide dimer can deepen our understanding mechanism of the weak interaction, and master the law of the non-hydrogen bonding weak interaction.In this paper, we optimize the structures of nitric oxide and nitric oxide dimer, and determine that the acyclic cis-ONNO 1A1 is the stable dimer through comparison of energy by quantum chemical calculation (Gaussian03). In condition of considering basis set superposition error ,we get the interaction energy between two molecules is 31.121926558586 KJ/mol. We protract the frontier orbitals by using population analysis, it shows that the dimer's frontier orbitals is formed by two monomer's frontier orbitals. Further analysis gives us that the monomer frontier orbitals occupied by the free radicals electron form the dimer frontier orbital through covalence mode is the main reason of weak interaction between molecules. The natural bond orbital analysis result tell that the interaction between monomers is mainly occurred between the single electron of one N side and the anti N-O bond belong to the other molecule. We may conclude that the free radical molecule's single electron makes a key effect on the weak interaction of nitric oxide dimer system.