Dynamic structural reconstruction of (guanidinium+)2(benzene-1,4-disulfonate2−) host crystal by guest adsorption

Abstract

Guanidinium (G⁺) and benzene-1,4-disulfonate (BDS²⁻) form a rigid electrostatic cation–anion crystal lattice, which undergoes an interesting dynamic structural reconstruction through guest adsorption–desorption processes with H₂O, pyrrole (Pyrr), pyrazine (Pyz), thiophene (TP), pyridine (Py), 1,4-dioxane (Diox), or aniline (Ani). The host lattice of bis(guanidinium)benzene-1,4-disulfonate, (G⁺)₂(BDS²⁻), which does not contain void spaces initially, changed to host–guest crystals of (G⁺)₂(BDS²⁻)·(guest)_x upon guest adsorption (x = 1, 2, and 3). The cation–anion electrostatic N–H⁺⋯⁻O₃S– hydrogen bonds between the G⁺ cation and BDS²⁻ dianion formed tightly bound two-dimensional (2D) structures. These layers are connected by perpendicular BDS²⁻ dianions, forming the guest adsorption crystalline pores. The adsorption–desorption isotherm for Diox at 298 K indicated the formation of (G⁺)₂(BDS²⁻)·(Diox)₃, which was consistent with the single-crystal X-ray structural analysis. Single crystals of (G⁺)₂(BDS²⁻)·(Py–H₂O)₂ consist of two hydrogen-bonded [(G⁺)₂(BDS²⁻)]₂ bilayers connected by the BDS²⁻ dianions, forming crystalline pores that accommodate 2 Py guest molecules. The H₂O molecules in (G⁺)₂(BDS²⁻)·(Py–H₂O)₂ are lodged in the intralayer, leading to the [(G⁺)₂(BDS²⁻)⋯(H₂O)₂⋯(G⁺)₂(BDS²⁻)] hydrogen-bonded bilayer. The electrostatic cation–anion host lattice of (G⁺)₂(BDS²⁻) responded to the guest adsorption–desorption cycle by a dynamic structural reconstruction. A guest adsorption of polar Ani into (G⁺)₂(BDS²⁻) host changed the crystal symmetry from centric P to acentric P2₁ of (G⁺)₂(BDS²⁻)·(Ani)₃.