Solid-state structures of group 1 and group 2 metal 1,5-naphthalenedisulfonates: systematic investigation of lamellar three-dimensional networks constructed by metal arenedisulfonate

Abstract

Seven Group 1 and Group 2 1,5-naphthalenedisulfonates (1,5-nds) have been synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and thermal gravimetric analysis. For Group 1 metal complexes, with M = Li+ (1), Na+ (2) and K+ (3), all crystallize in the same space group (P21/c) with the same composition, [M 2(1,5-nds)(H2O)2]. They adopt similar three-dimensional packing arrangements with the metal–sulfonate inorganic layers pillared by naphthalene rings. However, the coordination behavior of three metal cations toward the SO_3^- group and water molecule are different, resulting in different architectures for the inorganic portion. For Group 2 complexes with M = Mg2+ (4), Ca2+ (5), Sr2+ (6) and Ba2+ (7), Mg2+ shows no direct coordination by the SO_3^- group while Ca2+ is coordinated by four SO_3^- groups and a two-dimensional network is formed. Complexes (6) and (7) are isostructural, adopting the same three-dimensional, inorganic–organic pillared framework as seen for (1)–(3). The coordination behavior of the metal cations in these structures neatly illustrates the increase in coordination strength with decreasing charge/radius ratio for Group 1 and Group 2 metal cations with large organic anions.