TIMPZ: An Exquisite Building Block for Metal/Hydrogen Coordination Polymers

The novel polynitrogenated ligand tetra‐[4(5)‐imidazoyl]pyrazine (TIMPZ, 1) and its pincer complex of FeII are described. This ligand has an outstanding ability to aggregate in 1D‐superstructures by means of hydrogen bonding or metal chelation. TIMPZ shows an unprecedented conformational control over the supramolecular assembly. Metal or hydrogen coordination switches the conformation of peripheral rings driving the assembly preferences. For [Fen(TIMPZ)n+1]2n+ complexes, UV/Vis spectroscopy shows a bathochromic shift of the main visible absorption band with higher “n” values. TIMPZ also has hydrogen‐bond triggered excited‐state intramolecular proton transfer (ESIPT) fluorescence, which is completely inhibited by chelation with transition metals. Polynitrogenated ligand TIMPZ shows an unprecedented conformational control over the supramolecular assembly triggered by metal or hydrogen coordination. [Fen(TIMPZ)n+1]2n+ pincer complexes and 1D coordination polymers feature bathochromic shift of the main visible absorption band with increasing “n” values. (TIMPZ)n 1D aggregates as large as 22 units, showing ESIPT fluorescence, were detected.