The tropocoronand ligand (H2TC-m,n) is a macrocyclic ligand in which two aminotroponiminate rings are connected to one another via polymethylene linker chains of length m and n. Double deprotonation of the ligand yields a dianionic macrocylic species that is capable of binding divalent transition metal ions to form neutral complexes [M(TC-m,n)]. The 2-aminotroponeimine units are bridged by polymethylene linker chains with all four nitrogen atoms of the tropocoronand ligand bonded to a metal atom.