Density Functional Theory Studies On Intermolecular Interaction Of Aza-calix[6]arene With HMX

It is essential to decrease explosive sensitivity and dispose explosive waste water in energetic materials field. Because the aza-calix[6]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[6]arene derivative (amido, nitryl, azido substituted) complexes with HMX 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 energies 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 energies 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 HMX to the aza-calix[6]arene derivatives for complexes (a),(b),(c), (d),(f) and (h), while electrons transfer for the others reversely. The E⁽²⁾ energies follow the order of E_c⁽²⁾>E_f⁽²⁾>E_i⁽²⁾>E_g⁽²⁾>E_b⁽²⁾>E_j⁽²⁾>E_d⁽²⁾>E_h⁽²⁾>E_a⁽²⁾>E_e⁽²⁾>E_l⁽²⁾>E_k⁽²⁾. NBO analysis confirms that, complex (c) is easiest to form hydrogen-bond, as is in accordance with the results of structures and energies analysis.4.Temperature effect has been performed from 263 to 518 K for twelve complexes at B3LYP/6-311++G^** level. The results show that the low 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 (g)<(h)<(i)<(c)<(j)<(f)<(k)<(b)< (d)<(l)<(a)<(e), as is not in accordance with the results of structures, energies and NBO analysis. So the result confirmed that the temperature effect has little effect for the formation of the complex. The formation of the complex would be controled by kinetics.5. 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.6. 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 - 0.034a.u, and the Laplacian (?) values (positive) are all in the range of 0.024 -0.139a.u which Popelier suggested. Thus, the intermolecular hydrogen-bond interactions have been firmed in the host-guest complexes. The order of intermolecular interaction energies has been obtained by electronic densityρvalues, as is in accordance with the results of energies and NBO analysis.According to the calculated results, it can be concluded that p-amido-aza-calix[6]arene is available for eliminating HMX from explosive waste water.