Well-designed strategy to construct helical silver(I) coordination polymers from flexible unsymmetrical bis(pyridyl) ligands: syntheses, structures, and properties.

In this Article, self-assembly of AgX (X = NO3(-) and ClO4(-)) salts and four flexible unsymmetrical bis(pyridyl) ligands, namely, N-(pyridin-2-ylmethyl)pyridin-3-amine (L1), N-(pyridin-3-ylmethyl)pyridin-2-amine (L2), N-(pyridin-4-ylmethyl)pyridin-2-amine (L3), and N-(pyridin-4-ylmethyl)pyridin-3-amine (L4), results in the formation of eight helical silver(I) coordination polymers, [Ag(L)(NO3)]n [L = L1 (1), L2 (2), L3 (3), L4 (4)] and [Ag(L)(ClO4)]n [L = L1 (5), L2 (6), L3 (7), L4 (8)], which have been characterized by elemental analysis, IR, TG, PL, and powder and single-crystal X-ray diffraction. The alternating one-dimensional (1-D) left- and right-handed helical chains are included in achiral complexes 1-3 and 5-8. By contrast, the ligand L4 only alternately bridges Ag(I) cation to form the 1-D right-handed helical chain in complex 4. The pitches of these helical chains locate in the range 5.694(5)-17.016(6) Å. Meanwhile, the present four unsymmetrical bis(pyridyl) ligands in the eight complexes present diverse cis-trans and trans-trans conformation and facilitate the construction of helical structures. Moreover, the solid-state luminescent emission intensities of the perchlorate-containing complexes are stronger than those of nitrate-containing complexes at room temperature.