Guest Removal from Ring-Banded Guanidinium Organosulfonate Hydrogen-Bonded Frameworks

Abstract

Crystalline fibers of the hydrogen-bonded framework bis(guanidinium) naphthalene-1,5-disulfonate, (G)₂(1,5-NDS), with ethanol guest molecules twist as they grow when deposited from solution under conditions that favor low nucleation densities and high branching rates. Spherulites comprising helicoidal fibers with a pitch of 3.4 ± 0.5 μm display rhythmic concentric variations in interference colors between crossed polarizers. Tightly packed fibers and platelets, systematically change orientations between flat-on and edge-on crystallites with respect to the substrate surface. Mueller matrix imaging reveals periodic oscillations in the absolute magnitude of the linear retardance and an associated bisignate circular retardance. Single-crystal X-ray diffraction data demonstrates that the twisted (G)₂(1,5-NDS)⊃EtOH crystals adopt a bilayer packing motif with ethanol as guest molecules (space group P−1). When the banded spherulite films were subsequently heated at 130°C, the solvated phase was converted to a guest-free crystalline phase (space group P2₁/c). This transition resulted in loss of linear retardance.