Effect of anion on Ag(I) meso-helical chains formed with 4,4'-dipyridyl ketone: solvent versus anion bridging and anion effects on the strength of ligand binding.

The synthesis and characterisation by IR spectroscopy and elemental analysis of ten new Ag(I)-L complexes are described. Of these complexes, nine are characterised by single crystal X-ray diffraction: {[Ag(L)](CF₃SO₃)·½H₂O}∞ (1), {[Ag(L)](ClO₄)·1/2H₂;)∞ (2), {[Ag₂(L)₂(CH₃CN)](ClC₄)2·H2O)∞ (3), {[Ag₂(L)₂(CH₃CN)₂](ClO₄)₂·CH₃CN)∞ (4), {[Ag₂(L)₂(CH₃CN)₂](PF₆)₂·2CH₃CN)∞ (5), {[Ag(L)₂](CF₃SO₃)₄/2H₂OL (6), {[Ag(L)₂](BF4)∞(7), {[Ag(L)₂](PF6))∞ (8) and {[Ag(L)₂](PF₆)·₂CH₃CN)∞ (9). The primary structures of 1-6 were meso-helical one-dimensional (1D) polymers, while 7 was a helical 1D polymer and 8 and 9 were (4,4) networks. Complexes 1-5 possessed 1:1 metal-to-ligand (M: L) ratios, while complexes 6-9 possessed 1:2 M: L ratios. The meso-helical chains of complexes 1 and 2 were di-μ-bridged at the Ag(I) nodes by the counteranions CF3SC>₃^- and CIO₄^-, respectively, while the meso-helical chains of complexes 3-5 were di-μ-bridged at the Ag(I) nodes by the CH₃CN molecules. The effect of counteranions and solvent molecules on delicate anion-Ag, π-π-stacking and argentophilic interactions was studied through complexes 1-5. The 1D chains of complexes 6 and 7 possessed monodentate L ligand side arms. The uncoordinated N-donors of these side arms were inclined towards the Ag(I) centre of the adjacent chains and demonstrated narrower Ag-Npy-Cg(pyridyl) angles. In the case of complexes 8 and 9, wider Ag-Npy-Cg(pyridyl) angles and stronger N⋯Ag interactions resulted in (4,4) nets. The effects of the size and the nature of the counteranions on the topology were studied through complexes 6-9. [ABSTRACT FROM AUTHOR]