Experimental And Theoretical Studies On The Intercalated Structure Of Acid Orange 7-Pillared Layered Double Hydroxide

The structure and properties of acid orange 7-pillared layered double hydroxide(AO7-LDH)have been studied with both experimental characterizations and theoretical calculations.The intercalated structure, infrared absorption and thermal stability of AO7-LDH have been revealed through experimental characterization.From the theoretical aspect,both the host-guest and guest-guest interaction models of AO7-LDH have been built based on density functional theory(DFT).Furthermore,a strategy named combinational calculation of molecular fragments(CCMF)has been put forward to study the electronic structure of AO7-LDH.Mg/Al-AO7-LDH has been prepared by coprecipitation method with Mg/Al starting ratio of 2.XRD patterns indicate the product has the typical intercalated structure with a large gallery height of 1.79 nm.IR spectrum displays that the product has the characteristic absorption bands of both AO7 anion and the Mg/Al layer,well convincing the successful intercalation. TG-DTA curves demonstrate clearly that the thermal stability of AO7 can be enhanced by nearly 130℃when it is intercalated into LDHs. From the electronic structures of Mg/Al-lamella and AO7 anion investigated by B3LYP and B3PW91 methods at the levels of LANL2DZ, 6-31G(d,p)and 6-311++G(d,p),the host-guest interaction model can be built. The calculated results show that the combination of AO7 anion and lamella is favored in terms of energy and molecular frontier orbitals.According to the size of AO7 anions,they should be vertical-arranging in the interlayer space, forming an interdigitated structure.The guest-guest interaction of AO7-LDH has been modeled as the aggregation of AO7 anions.In order to eliminate the electrostatic repulsion effect,a proton is introduced into the sulfonate group to form a charge-neutral molecular HAO7.An azo- and hydrazone-form dimer with parallel-displaced aromatic stacking are obtained at the level of B3LYP/6-31G(d,p),respectively, which can well reflect the aggregation state of the interlayer AO7 anions.Finally,the CCMF strategy is put forward to deal with the complicated large systems using quantum chemical method.Its applicability in AO7-LDH system can be proved by the highly approximation between the theoretical and experimental interlayer distance values.More importantly,it may be extended to other supramolecular systems having complicate interactions as AO7-LDH.