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.