Crystal structure of a one-dimensional looped-chain silver(I) coordination polymer: catena-poly[[silver(I)-bis{μ-4-[1-(5′-isopropyl-[1,1′:3′,1′′-terphenyl]-2′-yl)-1H-imidazol-2-yl]pyridine-κ2 N:N′}] nitrate methanol monosolvate monohydrate]

The reaction of AgI with the pyridylimidazol ligand 4-(1-(5′-isopropyl-[1,1′:3′,1′′-terphenyl]-2′-yl)-1H-imidazol-2-yl)pyridine, afforded a nitrate-free one-dimensional looped-chain polymeric structure. The AgI cation adopts a highly distorted tetrahedral geometry coordinated by two pyridine N atoms and two imidazole N atoms from four individual ligands.


Chemical context
Group-9 metal complexes bearing phenylimidazole-based ligands are considered to be suitable triplet emitters for use in phosphorescent organic light-emitting diodes (PHOLEDs) because of their high efficiency and long-term stability . However, there are relatively few reports of the structures of metal complexes that exhibit coordination of pyridylimidazole (pyim) ligands with an L-type coordination sphere, which is similar to a phenylimidazole system. Recently, Ag I coordination polymers built from pyim ligands have attracted much attention due to their structural diversity and photoluminescence properties which have been shown to depend on the nature of the counter-anion . The structural topology of Ag I is quite sensitive to both the counter-anion and solvent molecules (Durá et al., 2014). Herein, we describe the structure of an Ag I compound with 4-(1-(5 0 -isopropyl-[1,1 0 :3 0 ,1 00 -terphenyl]-2 0 -yl)-1H-imidazol-2yl)pyridine, i-pro-pyim, as the pyim ligand. The coordination ISSN 2056-9890 polymer is obtained by addition of the ligand to AgNO 3 in methanol/acetonitrile. The title nitrate salt is closely related to the perchlorate salt .

Structural commentary
The title compound crystallizes with one Ag I atom, two pyim ligands (A and B), one nitrate anion, one methanol solvent molecule, and two water solvent molecules, each with an occupancy factor of 0.5, in the asymmetric unit. As shown in Fig. 1, the Ag I atom is coordinated by two pyridine N atoms and two imidazole N atoms from four individual i-pro-pyim ligands, giving rise to a highly distorted tetrahedral geometry with bond angles falling in the range of 100.33 (19)-122.76 (19) ( Table 1). The average Ag-N distance is 2.31 Å , similar to that found in the related perchlorate salt .
In the title compound there are two crystallographically independent ligands, A and B, and their conformations are very similar, such that the dihedral angles between the pyridyl and imidazolyl rings in the two ligands are 40.7 (3) and 42.2 (3) , respectively. Moreover, there are intramolecularinteractions between the pyridyl and phenyl rings of both ligand types, N3,C4-C8 and C21-C26 [centroid-to-centroid distance = 3.760 (4) Å ] for A and N6,C33-C37 and C51-C56 [centroid-to-centroid distance = 3.716 (4) Å ] for B.

Figure 3
The two-dimensional supramolecular network formed through intermolecularinteractions (dashed lines). H atoms, nitrate anion and the lattice solvent molecules have been omitted for clarity. rings [symmetry code: (v) Àx + 2, Ày, Àz + 1], resulting in the formation of a two-dimensional supramolecular network propagating parallel to (110) (Fig. 3). No notable interactions are found between the two-dimensional networks. The nitrate anions and lattice solvent molecules occupy the void volume between the layers. The crystal structure of the title compound is further stabilized by weak C-HÁ Á ÁO hydrogen bonds between the looped chains and the lattice solvent molecules/ nitrate anions, and by O-HÁ Á ÁO hydrogen bonds between the lattice methanol/water molecules or the nitrate anions (Table 2).

Synthesis and crystallization
The i-pro-pyim ligand was synthesized according to literature procedures . Crystals of the title compound were obtained by combining AgNO 3 with the i-pro-pyim ligand in a 1:1 molar ratio in a mixture of methanol/acetonitrile (1:1) and allowing the solution to evaporate slowly at room temperature.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ.