Coordination properties of axially unfixed chiral dipyridine ligands towards metal and ammonium ions

New chiral dipyridine ligands with an axially unfixed 1,1′-biphenyl bridge were prepared via homocoupling of bromophenyl pyridines. The conformeric ratios of the free ligands in solution and their coordination properties towards metal ions were studied by NMR spectroscopy. X-Ray crystallography of the silver(I) and copper(I) complexes showed 1:1 metal to ligand complexes and S planar chirality. Interestingly, the biphenyl ligands show a 1:2 stepwise binding towards most ammonium ions tested with strong fluorescence enhancement, but a selectively 1:1 binding towards l-ornithine methyl ester hydrochloride with no fluorescence enhancement.

Coordination properties of new chiral dipyridine ligands with an axially unfixed 1,1′-biphenyl bridge towards metal and ammonium ions were studied. X-Ray crystallography of the silver(I) and copper(I) complexes show a 1:1 metal to ligand complex and S planar chirality. But the biphenyl ligands show a 1:2 stepwise binding towards most of the ammonium ions tested with strong fluorescence enhancement.Figure optionsDownload as PowerPoint slideResearch highlights
► Preparation of new chiral dipyridine ligands with an axially unfixed 1,1′-biphenyl bridge.
► Crystal structures of silver(I) and copper(I) complexes show 1:1 Complex and S planar chirality.
► The ligands show 1:2 stepwise binding with ammonium ions with fluorescence enhancement.