Abstract: The tristhiourea tripodal metal complexes are a group of coordination compounds having a transition metal linked by coordinate covalent bods to a chelating agent. The chelating agent has a tris-(6-amino-2-pyridylmethyl)amine (TAPA) backbone and three thiourea ligands bonded to the three legs of the TAPA backbone, respectively. The transition metal bonds to the amino groups of the TAPA backbone, and the thiourea ligands hydrogen bond to the anion guest remote from the transition metal. The chelating agent has a symmetrical C3v tripodal cavity that is selective for tetrahedral anions. The transition metal is selected from the group consisting of cadmium, manganese, cobalt, nickel, copper, and zinc. The tristhiourea tripodal metal complexes may be used in colorimetric sensors, selectively permeable membranes, filtration media for separating tetrahedral anions (such as phosphate and perchlorate) from mixtures, and similar applications.