Template condensation of formaldehyde with triamines. Synthesis and characterization of nickel(II) complexes with the novel hexaaza macrotricyclic ligands 1,3,6,9,11,14-hexaazatricyclo[12.2.1.16,9]octadecane and 1,3,6,10,12,15-hexaazatricyclo[13.3.1.16,10]eicosane