Crystal structure of catena-poly[[silver(I)-μ-N-(pyridin-2-ylmethyl)pyridine-3-amine-κ2 N:N′] trifluoromethanesulfonate]

The reaction of AgI with the unsymmetrical ligand N-(pyridine-2-ylmethyl)pyridine-3-amine afforded right- and left-handed helical chains. The AgI atom of the right-handed helical chain adopts a slightly distorted linear coordination geometry, while that of the left-handed helical chain displays a bent geometry.

In the asymmetric unit of the title compound, {[Ag(C 11 H 11 N 3 )]CF 3 SO 3 } n , there are two Ag I atoms, two N-(pyridine-2-ylmethyl)pyridine-3-amine ligands (A and B) and two CF 3 SO 3 À anions. Both Ag I atoms are bridged by two pyridine N atoms from two symmetry-related A or B ligands, forming right-or left-handed helical chains, respectively. The Ag I atom of the right-handed helical chain adopts a slightly distorted linear coordination geometry  ], while that of the left-handed helical chain adopts a bent geometry  ]. Both helical chains have the same pitch length

Chemical context
A few silver coordination polymers based on unsymmetrical dipyridyl ligands composed of two terminal pyridines with different substituted-nitrogen positions have been reported Zhang et al., 2013). In an extension of investigations on Ag I coordination polymers with unsymmetrical dipyridyl ligands, the title compound was prepared by the reaction of silver trifluorometanesulfonate with N-(pyridine-2-ylmethyl)pyridine-3-amine. The structure of title compound is related to that of the perchlorate salt (Moon & Park, 2014;Zhang et al., 2013).

Structural commentary
The molecular components of the title structure are shown in Fig. 1. The asymmetric unit contains two Ag I atoms (Ag1 and Ag2), two N-(pyridine-2-ylmethyl)pyridine-3-amine (Lee et ISSN 1600-5368 al., 2013) ligands (A and B) and two trifluoromethanesulfonate anions. The Ag1 atom is coordinated by two pyridine N atoms from two symmetry-related A ligands giving a geometry which is slightly distorted from linear [N1-Ag1-N2 = 170.69 (14) ], forming a right-handed helical chain, while the Ag2 atom is coordinated by two pyridine N atoms from two symmetry-related B ligands in a bent arrangement  ], forming a left-handed helical chain. Two pyridine rings coordinating to the Ag1 and Ag2 atoms are tilted by 14.1 (3) and 28.9 (2) , respectively, with respect to each other.

Synthesis and crystallization
The ligand (N-(pyridin-2-ylmethyl)pyridine-3-amine) was prepared according to a procedure described by Lee et al. (2013). Crystals of the title compound suitable for X-ray analysis were obtained by vapour diffusion of diethyl ether into a DMSO solution of the white precipitate afforded by the reaction of the ligand with silver(I) hexafluoridophosphate in the molar ratio 1:1 in methanol.

Refinement details
Crystal data, data collection and structure refinement details are summarized in

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.