Controlled aggregation of multiple guanidinium ions through a hydrogen-bonded network assembly with deprotonated...

A series of five complexes that incorporate the guanidinium ion and various deprotonated forms of Kemp's triacid (H(3)KTA) have been synthesized and characterized by single-crystal X-ray analysis. The complex [C(NH(2))(3)(+)].[H(2)KTA(-)] (1) exhibits a sinusoidal layer structure with a centrosymmetric pseudo-rosette motif composed of two ion pairs. The fully deprotonated Kemp's triacid moiety in 3 [C(NH(2))(3)(+)].[KTA(3-)] (2) forms a record number of eighteen acceptor hydrogen bonds, thus leading to a closely knit three-dimensional network. The KTA(3-) anion adopts an uncommon twist conformation in [(CH(3))(4)N(+)].2[C(NH(2))(3)(+)].[KTA(3-)].2H(2)O (3). The crystal structure of [(nC(3)H(7))(4)N(+)].2[C(NH(2))(3)(+)].[KTA(3-)] (4) features a tetrahedral aggregate of four guanidinium ions stabilized by an outer shell that comprises six equatorial carboxylate groups that belong to separate [KTA(3-)] anions. In 3 [(C(2)H(5))(4)N(+)].20[C(NH(2))(3)(+)].11[HKTA(2-)].[H(2)KTA(-)].17H(2)O (5), an even larger centrosymmetric inner core composed of eight guanidinium ions and six bridging water molecules is enclosed by a crust composed of eighteen axial carboxyl/carboxylate groups from six HKTA(2-) anions.