Coordination properties of axially unfixed chiral dipyridine ligands towards metal and ammonium ions
摘要:
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. (C) 2011 Elsevier Ltd. All rights reserved.