A copper(II) paddle-wheel structure of tranexamic acid: di­chloro-tetra­kis­[μ-4-(ammonio­meth­yl)cyclo­hexane-1-carboxyl­ato-O,O′]dicopper(II) dichloride hexa­hydrate

Tranexamic acid [systematic name: trans-4-(amino­meth­yl)cyclo­hexane-1-carb­oxy­lic acid], is an anti­fibrinolytic amino acid that exists as a zwitterion [trans-4-(ammonio­meth­yl)cyclo­hexane-1-carboxyl­ate] in the solid state. Its reaction with copper chloride leads to the formation of a compound with a copper(II) paddle-wheel structure that crystallizes as a hexa­hydrate, [Cu(2)Cl(2)(C(8)H(15)NO(2))(4)](2+)·2Cl(−)·6H(2)O. The asymmetric unit is composed of a copper(II) cation, two zwitterionic tranexamic acid units, a coordinating Cl(−) anion and a free Cl(−) anion, together with three water mol­ecules of crystallization. The whole structure is generated by inversion symmetry, with the Cu⋯Cu axle of the paddle-wheel dication being located about a center of symmetry. The cyclo­hexane rings of the zwitterionic tranexamic acid units have chair conformations. The carboxyl­ate groups that bridge the two copper(II) cations are inclined to one another by 88.4 (8)°. The copper(II) cation is ligated by four carboxyl­ate O atoms in the equatorial plane and by a Cl(−) ion in the axial position. Hence, it has a fivefold O(4)Cl coordination sphere with a perfect square-pyramidal geometry and a τ (5) index of zero. In the crystal, the paddle-wheel dications are linked by a series of N—H⋯Cl hydrogen bonds, involving the coordinating and free Cl(−) ions, forming a three-dimensional network. This network is strengthened by a series of N—H⋯O(water), O(water)—H⋯Cl and O(water)—H⋯O hydrogen bonds.