Preparation of one-dimensional coordination polymers of a flexible tripyridyl disulfide with diverse topologies

A novel flexible tripyridyl disulfide ligand (L, 2,6-bis(4-pyridinesulfanylmethyl)pyridine) having a pyridyldithioether backbone was synthesized and its diverse types of one-dimensional (1D) coordination polymers (1-4) with coinage metal (copper and silver) salts were isolated. The complexation with copper(II) nitrate afforded a loop chain type product {[Cu(L)(2)(NO3)(2)]center dot CH2Cl2} n (1), in which twisted Cu2L2 metallacycles in an S-configuration of L share one copper(II) node. The complexations with silver(I) salts (X = NO3-, PF6-, and ClO4-) resulted in three 1D coordination polymers; {[Ag(L)NO3]center dot CH2Cl2}(n) (2, NO3-form), {[Ag(L)(CH3CN)]PF6}(n) (3, PF6-form), and {[Ag(L)ClO4]center dot CH2Cl2}(n) (4, ClO4-form). Both products 2 (NO3-form) and 3 (PF6-form) show a similar Ag2L2 metallacycle-based ribbon structure with a C-configuration of L except for the anion coordination (NO3-) in 2 and the solvent (CH3CN) coordination in 3. Product 4 (ClO4- form) displays a deformed ladder structure; two parallel (Ag-L)(n) chains with an out-of-phase of the S-configuration of L as rails, and the crosslinking Ag-S bonds as rungs. Anion exchange studies revealed that the PF6- in 3 was replaced by NO3- to yield product 2 but the reverse process was not possible. Compared to the free ligand L with a medium photoluminescence (PL) intensity, the silver(I) products showed enhanced emissions while the copper(II) complex was silent.