Theoretical And Experimental Studies On The Electronic Structure And Photochromism Of Orange Ⅱ-Pillared Layered Double Hydroxide

The structures and properties of orange II-pillared layered double hydroxide have been studied with both experimental characterizations and theoretical calculations. At the same time, the isomerization mechanism of the molecular acid orange 7 has been studied with the theoretical calculations.Zn/Al-LDHs has been prepared by coprecipitation, ion exchange and calcine-recovering methods, respectively. The value of pH is different based on the scale of Zn/Al. XRD patterns indicate that the products have the typical intercalated structure with the interlayer distance of 2.20～2.22 nm. The gallery height is 1.73～1.75 nm which is lager than that of the CO₃-LDHs and NO₃-LDHs. IR spectrum displays that the product has the characteristic absorption bands of both anion and the Zn/Al layer, well convincing the successful intercalation.The geometry structures of orange II anion and Zn/Al-lamella have been optimized with the B3LYP and B3PW91 methods at the levels of LANL2DZ, 6-31G(d, p), respectively. At the same level, the host-guest interaction model can be built. The calculated results show that the combination of the anion and lamella is favored in terms of energy and molecular frontier orbitals. According to the size of orange II anions, they should be vertical-arranging in the interlayer space, forming an interdigitated structure.The isomerization reaction of orange II molecular has been studied based on the DFT. The structures of transition states has been optimized with the B3LYP, B3PW91 methods at the level 6-31G(d, p). At the same level, the vibrational frequencies have been computed. The computed results present that the isomerization reactions of orange II can be completed with the energy barrier is less than 100 kJ·mol^-1. The structures of the end point of IRC are close to that of reactants and products, which well convince the transition states.