The title compound, (N4C6H21)center dot(Co(H2PO4)(HPO4)(2)), was prepared hydrothermally (473 K, 10 days, autogenous pressure), in the presence of the tris(2-aminoethyl)amine as organic template. Its structure is built up from a network of four membered-rings, formed by the vertex linkages between [CoO4] and [H2PO4] tetrahedra with [HPO4] moieties hanging from the Co center. Hydrogen bonds involving the cobalt phosphate units and the triply protonated amine molecule, contribute to the stability of the structure. The IR spectrum shows bands characteristic of the (N4C6H21)(3+) cations and the (H2PO4)(-) and (HPO4)(2-) phosphate anions. The UV-Visible-NIR spectrum confirms the tetrahedral coordination of Co2+ ions. The TGA analysis indicates that the dehydration of (N4C6H21)center dot(Co(H2PO4)(HPO4)(2)) occurs in one step. Magnetic measurements from 4.5 to 305 K show a weak antiferromagnetic character of this compound. (c) 2005 Elsevier Ltd. All rights reserved.