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

• Published in: Polyhedron 2011-04, Vol.30 (6), p.1149-1156
• Main Authors: Sham, Kiu-Chor, Lee, Chi-Sing, Chan, Ka-Yee, Yiu, Shek-Man, Wong, Wing-Tak, Kwong, Hoi-Lun
• Format: Article
• Language: English
• Subjects: Ammonium ions binding; Chiral ligand; Copper complex; Dipyridine ligand; Metal binding; Silver complex
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2011.01.017

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. [Display omitted] ► 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. 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.