Synthesis and solvent vapor-induced transformations of crystals of 1D coordination polymers assembled with continuous void space

Abstract

9,9′-Biacridine (L1) has a three-dimensional structure of perpendicularly connected acridine moieties with two coordination sites at either end of the molecules. Crystallization of L1 with silver(I) salts gives various 1D coordination polymers with structures that depend on the crystallization solvents and counter anions used. We synthesized six complexes: [Ag(L1)]n(BF4)n·2nTHF (1a·THF, THF = tetrahydrofuran), [Ag(L1)]n(ClO4)n·2nTHF (1b·THF), [Ag(L1)(CH3OH)]n(BF4)n·1.5n(furan) (1a·Furan), [Ag(L1)]n(BF4)n·nDCM (1a·DCM, DCM = dichloromethane), [Ag(L1)]n(ClO4)n·nDCM (1b·DCM), and [Ag2(L1)(CF3COO)2]n (1c). We also synthesized crystals of phenazine (L2) complexed with silver(I) cations which featured layered structures with no void space. In the crystals of 1a·THF and 1b·THF, a linear channel structure formed, which was filled with THF molecules; however, 1a·DCM and 1b·DCM featured no continuous channel structure and their void space was filled with DCM molecules. 1a·Furan had a zigzag-shaped channel filled with furan molecules. The crystal structures of the complexes were similar regardless of whether tetrafluoroborate or perchlorate anions were included in the structure. The crystal structure of 1c showed a ladder structure with chains of silver(I) cations and trifluoroacetate anions. A reversible crystal-to-crystal structural transformation was observed between the complexes of 1a·THF and 1a·DCM, which was investigated by single crystal and powder X-ray diffraction measurements. Our measurements suggested that solvent molecules in the crystal structure were replaced together with concerted rotation of the 1D chains of the coordination polymers, occurring when the crystals were exposed to the vapor of a different solvent.