Strong lone pair•••π interactions between amine and tri-s-triazine derivatives: A theoretical investigation

For a better understanding of the interesting lone pair center dot center dot center dot pi (lp center dot center dot center dot pi) interaction, MP2 and CCSD(T) calculations have been carried out to investigate the nitrogen lp center dot center dot center dot pi interactions between amine and tri-s-triazine derivatives. New strong attractive lp center dot center dot center dot pi interactions are observed when the lone pairs of NH3 and NMe3 point toward the large pi system, tri-s-triazine ring. At the CCSD(T)/6-311++G(d,p)//MP2/6-311G(d,p) level, the BSSE corrected interaction energy of the C6N7H3 center dot center dot center dot NH3 complex is -6.3 kcal mol(-1),-which is larger than those of the most previously reported lp center dot center dot center dot pi systems. The substitution effects on interaction energy of the present studied systems were studied to probe how to manipulate lp center dot center dot center dot pi interaction and obtain stronger one. The results indicate that the very strong lp center dot center dot center dot pi interaction can form between electron-rich amines and electron-deficient large aromatic ring. But the lp center dot center dot center dot pi interactions between the electron-deficient amine such as NF3 and aromatic ring are very weak. The C6N7F3 center dot center dot center dot NMe3 complex has interaction energy of -9.8 kcal mol(-1). This interaction is much stronger than previously reported lp center dot center dot center dot pi bindings. The AIM analysis of the nine studied complexes shows that their molecular graphs are obvious different from previously reported benzene center dot center dot center dot amine complexes and X-H/pi systems, which may result from the tri-s-triazine ring's characteristic. (c) 2013 Elsevier B.V. All rights reserved.