Hydrophilic and Hydrophobic Channels of Flexible Crystal Lattice: (Guanidinium)2(Benzene-1,4-disulfonate)·n(XC6H5)

The −NH2···[SO3–]– electrostatic hydrogen bonding interaction between guanidinium (G+) and benzene-1,4-disulfonate (BS2–) formed the two-dimensional hydrogen-bonding network linked by benzene pillars, which formed a host–guest crystal with a halobenzene derivative (XC6H5) as a guest. When X = F, the (G+)2(BS2–)·3(FC6H5) crystals were obtained in the same type as the benzene inclusion (G+)2(BS2–)·3(C6H6) crystals. On the contrary, the size of the guest molecule increases for X = Cl and Br, and a hydrophilic channel with nine H2O molecules and a hydrophobic channel with two XC6H5 molecules coexist in (G+)2(BS2–)·2(XC6H5)·9(H2O) crystals. The crystal structure with X = I returned to that of the crystals with FC6H5 as the guest, and the number of guest molecules decreased from three to two. Crystals with hydrophilic channels in a highly symmetric hexagonal lattice appear at X = Cl and Br, which are the boundary region between X = F and I. (G+)2(BS2–)·2(ClC6H5)·9(H2O) crystals changed to guest-free crystals by heat at 373 K, which showed only gate H2O adsorption–desorption behavior at 298 K. The original host–guest crystals were recovered by the vapor diffusion of the ClC6H5–H2O mixture. However, once the crystal is heated to 420 K, it changes to a different host crystal (G+)2(BS2–), where XC6H5 cannot be adsorbed again.