Modified pyridine–triazole and 2,2′-bipyrimidine ligands generating robust titanium complexes constructed around a TiO4N2 core

International audience; The synthesis and characterization of novel chelate nitrogen ligands with phasmidic tails (pyridine-triazole ligand 1b; 2,2'bipyrimidine ligands 2b and 3b) is reported, as well as their titanium (IV) coordination complexes. The analogous ligands 1a, 2a and 3a with methoxy substituents instead of the tails were also synthesized, together with titanium complexes that could be crystallographically characterized. A good agreement is noticed between analytical data of the complexes in solution (NMR) and in the solid state (X-ray diffraction). The complexes are overall stable on phases like alumina or silica, so that they could be characterized by TLC and sometimes chromatographied. Supramolecular architectures were generated from an equimolar solution of titanium (IV) isopropoxide, ligand 1a and a polyphenol ligand 5-H4, leading to a double-stranded helicate characterized by MS, NMR and crystallography, which was then converted into a trinuclear complex as shown by MS and NMR DOSY data. The liquid-crystalline behaviour of the ligands 1b, 2b and 3b incorporating the long alkyl tails, and of the complexes derived from these ligands, has been investigated.