Crystal structure of diaqua[μ-12,25-dimethyl-3,8,16,21-tetraazatricyclo- [21.3.1.110,14]tetracosa-1(27),10,12,14(28),23,25-hexaene-27,28-diolato- k4N3,N8,O27,O28: k4N16,N21,O27,O28]dicopper(II) bisnicotinate — methanol —water (1:1:3.5), [Cu2(H2O)2(C26H38N4O2)][C6H4NO2]2 · CH3OH · 3.5H2O