Tripodal naphthalene ether ligand: Solid-state anion recognition and fluorescence studies

The simple tripodal amine ligand Tris-[2-(naphthalen-1-yloxy)-ethyl]-amine (L1) was screened for anion recognition. Four crystal structures confirmed the inorganic as well as organic anion recognition in the solid state. Solid-state structures are results of supramolecular self-assembly and 3D molecular network involves C–H⋯O and C–H⋯π bonding in the crystal lattice. In the solid state, it forms a strong C–H⋯Cl and C–H⋯O type interactions with the anions. This anion recognition was also confirmed by steady state fluorescence spectroscopy. In complex 4, L1 is confined between 2D hydrogen bonded sheet formed by pyromellitic acid anion. L1 shows unusually high selectivity toward nitrate in solution resulting in both a dramatic color change and a concomitant quenching of luminescence.