The hexadentate ligand N,N',N''-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane (tachpyr) forms stable metal complexes from the salts M(ClO 4 ) 2 .6H 2 O (M=Zn 2 + and Cd 2 + ) and Hg(ClO 4 ) 2 in methanol or ethanol. The complexes [Zn(tachpyr)](ClO 4 ) 2 .CH 3 OH (1.CH 3 OH), [Cd(tachpyr)](ClO 4 ) 2 (2) and [Hg(tachpyr)](ClO 4 ) 2 (3) have been isolated, and their solid state structures have been determined and analyzed. The coordination sphere changes from octahedral to trigonal-prismatic geometry with increasing metal radius. The trigonal twist angles (α) are 43.7(2) o in compound 1.CH 3 OH, range between 11.0(4) o and 21.7(2) o in compound 2 and range between 3.1(3) o and 5.5(2) o in compound 3. To accommodate larger metal ions there is also a slight outward expansion of the triaminocyclohexane nitrogens, which leads to a reduction in the average cyclohexyl ring C-C-C-C torsion angles (β) with concomitant flattening of the ring. The torsion angles (β) in 1.CH 3 OH are 52.3(6) o and 52.4(6) o , range between 46.1(9) o and 52.7(9) o in compound 2 and range between 45.1(6) o and 52.9(7) o in compound 3.