The crystal and molecular structures of 1, [Cu(en)2(mtpo)2], C16H26CuN12O2, and 2, [Cu(dach)2(OH2)2](mpto)2, C24H42CuN12O4, (where Hmpto is 4,7-dihydro-5-methyl-7-oxo-[ 1,2,4]triazolo- [1,5-a]-pyrimidine, en is 1,2-ethylenediamine and dach is cis-1,2-diaminocyclohexane) have been determined at room temperature. The blue crystals of 1 are triclinic, space group P1̄ with unit cell dimensions a = 8.507(2) Å, b = 9.544(1) Å, c = 6.976(1) Å, α = 110.16(1)°, β= 103.65(2)°, γ = 81.24(1)°, Z = 1 and Dx = 1.554 Mg m-3 and the purple crystals of 2 are monoclinic, space group C2/c with unit cell dimensions a = 16.531(5) Å, b = 12.691(7) Å, c= 15.153(6) Å, β= 112.64(2)°, Z = 4 and DX = 1.418 Mg m-3. The structures were solved by direct methods and refined by a full-matrix least-squares procedure on F to final R = 0.034 using 1994 reflections for 1 and R = 0.038 using 1849 reflections for 2. In the structure of centrosymmetric 1, two mpto anions form Cu . . . N(3) distances of 2.629(3) Å above and below an essentially square planar CuN4 geometry. By contrast, in centrosymmetric 2, the weak Cu . . . mpto contacts are replaced by weak Cu . . . OH2 contacts such that the anions do not associate with the copper center. The study demonstrates two new coordination modes for mtpo. The respective structures are stabilised by extensive intra- and intermolecular hydrogen bonding contacts.