Density Functional Theory Studies On Intermolecular Interaction Of Aza-calix[4]arene With RDX

It is essential to decrease explosive sensitivity and dispose explosive waste water in energetic materials field. Because the aza-calix[4]arene derivatives are prone to be synthesized as well as N atom and the ring of calixarene can offer electron to form host-guest complex with electron acceptor, an new thought is offered that one complex in which intermolecular interaction is the strongest is chosen from twelve aza-calix[4]arene derivative (amido, nitryl, azido substituted) complexes with RDX to decrease the explosive sensitivity and dispose the explosive waste water.Since the selectivity order obtained from interaction energies might be reversed after taking into account the solvent effects, the onsager solvent model is employed for twelve complexes in aqueous solution. The results and conclusions are briefly as follow:1. Twelve fully optimized structures of complexes have been obtained at B3LYP/6-311++G** level. The minimum energy points, at which the harmonic frequency analyses have been carried out and the complexes have no imaginary frequency, at the molecular energy hypersurface have been obtained. The hydrogen-bond interactions have been verified in the host-guest complexes by the structural criterion of hydrogen bonds. And the order of intermolecular interaction energy has been evaluated by the structural character of hydrogen bond.2. The intermolecular interaction energies have been calculated at MP2(FC)/6-311++G** level with basis set superposition error correction (BSSE) and zero point energy correction (ZPEC) for twelve complexes. The intermolecular interaction energy and deformation energy have been analyzed, and the order of hydrogen-bond energy in twelve complexes has been obtained.3. Natural bond orbital (NBO) analysis has been performed at B3LYP/6-311++G** level. Electrons transfer from RDX to the aza-calix[4]arene derivatives for complexes (h),(k) and (l), while electrons transfer for the others reversely;and the order of E(2) of every complex reveals the order of hydrogen-bond interaction, as is in accordance with the results of structures.4. AIM analysis has been employed for twelve complexes at B3LYP/6-311++G** level. The results show that the electronic density values of bond saddle point are all in the range of 0.002– 0.034 a.u, and the Laplacian▽2ρ(rc) values (positive) are all in the range of 0.024– 0.139 a.u which Popelier suggested. Thus, the intermolecular hydrogen-bond interactions have been firmed in the host-guest complexes. The order of intermolecular interaction energy has been obtained by electronic densityρvalues, as is in accordance with the results of energies and NBO analysis.5. Temperature effect has been performed from 263 to 398 K for twelve complexes at B3LYP/6-311++G** level. The results show that the lower temperature is propitious to formation of the complex. Compared to the Gibbs free energy in 298.15 K, possibility of the formation of these complexes follows the order of (j)<(h)<(k)<(l)<(g)<(e)<(i)<(b)<(f)<(a)<(d)<(c), as is in accordance with the results of structures, energies and NBO analysis.6. Solvent effect has been employed in the range of 38.25– 47.25 for theεvalue of twelve complexes at B3LYP/6-311++G** level. The results show that the intermolecular interaction energies in the gas are akin to in aqueous phases. The solvent has little effect for the formation of the complex.According to the calculated results, it can be concluded that m-amido-substituted tetra- aza-calix[2]arene[2]-triazine 8 is available for eliminating RDX from explosive waste water.