Intercalation-Induced Ordered Nanostructure in the Interlayer Modified with Methylviologen by Molecular Dynamics Simulation

Intercalation of phenol in montmorillonite, a representative layered material, has historically been investigated, and modification of the interlayer with methylviologen (Mont-MV) results in color change due to formation of a charge-transfer complex. Its detailed nanostructure, however, has yet been revealedowing to its small gallery height and poor crystallinity. In the present study, we performed molecular dynamics simulation to investigate structural changes in Mont-MV by the intercalation of phenol. The value of the basal spacing of Mont-MV was wellconsistent with that reported experimentally, and the MV cationswere distributed horizontally. Successive intercalation of phenolrevealed that the interlayer swelled nonlinearly and both the MVcations and phenol molecules were tilted, which were roughlyparallel to each other. The obtained ordered nanostructure was similar to that reported in the charge-transfer complex crystal of the MV cation and the naphthol derivative. Thus, the parallel orientation in the interlayer was found to be the key for the color reaction. Combined with the fact that the phenol molecules interacted with the Mont layers, the role of the MV cation was found to be that of a pillar for providing sufficient gallery height, and the formation of the charge-transfer complex is the secondarily derived function.