C3 symmetric tris(phosphonate)-1,3,5-triazine ligand: homopolymetallic complexes and its radical anion

The ligand 2,4,6-tris(dimethoxyphosphonate)-1,3,5-triazine L has been synthesized and its single crystal X-ray structure determined. The occurrence of PO⋯π intermolecular interactions, suggested by the short PO⋯triazine distances of 3.16–3.35 A, is observed. The electrochemical reduction of the ligand shows its electron acceptor character by the formation of a stable radical anion. The hyperfine structure observed in the EPR spectra, combined with a theoretical DFT study, evidences the full delocalization of the unpaired electron mainly on the triazine core, with some participation of the phosphonate groups. Theoretical calculations are in agreement with the experimental values of the hyperfine coupling constants of 11.81 G for Aiso–31P and 1.85 G for Aiso–14N. Homopolymetallic complexes, formulated as {L[Cu(hfac)2]3} (1), 1∞{L2[Co(hfac)2]3} (2) and 1∞{L2[Mn(hfac)2]3} (3) (hfac = hexafluoroacetylacetonate), have been synthesized and structurally characterized.