9,21,22-Triaza-2,11-dithia[3.3](2,6)pyridino(2,9)phenanthrolinophane: a five-donor macrocycle functioning as a bidentate ligand

9,21,22-Triaza-2,11-dithia[3.3](2,6)pyridino(2,9)phenanthrolinophane 4 was prepared from a cyclization reaction of 2,6-bis(mercaptomethyl)pyridine 5 and 2,9-bis(bromomethyl)phenanthroline 6. Results from 1H NMR analysis are inconclusive but those derived from semi-empirical molecular orbital PM3 calculations support a preference for a syn conformation for 4. The conformation barrier for interconversion between two syn isomers of 4 was estimated to be 36.5 kJ mol−1 on the basis of a dynamic 1H NMR study. The manganese(II) and zinc(II) complexes of 4 were prepared and the metal to ligand ratios were found to be 1:1 and 2:1, respectively, by elemental analyses. Results from an 1H NMR analysis of the zinc(II) complex of 4 suggest that only the two nitrogen atoms of the phenanthroline moiety participate in the co-ordination.