Helical Silver(I)−2,4‘-Bipyridine Chains Organized into 2-D Networks by Metal−Counterion or Metal−Metal Bonding. Structures of [Ag(2,4‘-bipyridine)]X (X^- = NO₃^- or ClO₄^-)

Abstract

Two compounds, [Ag(2,4‘-bpy)]NO3 (1) and [Ag(2,4‘-bpy)]ClO4 (2), were obtained from self-assembly of AgX (X = NO3 -, ClO4 -) with 2,4‘-bipyridine (2,4‘-bpy). 1 crystallizes in the orthorhombic space group Pbca, with a = 11.2884(7) Å, b = 11.3981(10) Å, c = 16.5299(13) Å, and Z = 8, while 2 crystallizes in the monoclinic space group P21 /c, with a = 10.6361(4) Å, b = 9.9896(4) Å, c = 11.2661(6) Å, β = 98.527(4)°, and Z = 4. Both complexes consist of helical [Ag(2,4‘-bpy)]∞ chains that are surrounded by nitrate or perchlorate counterions. Adjacent helical chains are racemic. The AgI atom is linked to two nitrogen atoms of the 2-pyridyl and 4‘-pyridyl groups from two different 2,4‘-bpy ligands as well as to the oxygen atom of the counterion. In 1, another oxygen atom of the counterion is weakly coordinated to the AgI atom of an adjacent chain, thus bridging the helical chains into a wavy 2-D network structure, whereas in 2, adjacent helical chains are linked by the weak ligand-unsupported metal−metal interactions, resulting in an open 2-D network with compressed hexagons as building units. The structures of 1 and 2 imply the role that counterions may play in the framework construction.

Crystal engineering of coordination polymers and architectures using the [Cu(2,2′-bipy)]2+ molecular corner as building block (bipy = 2,2′-bipyridyl)

“…The competition between cyclic species and open-chain oligomers or polymers has been observed in many related systems. As outlined by Fujita, in studying the self-assembly of 15.897 (1) 11.962 (4) 7.430 (5) 8.298 (1) 17.100 (3) 11.555 (5) c/A Ê 10.228 (4) 13.595 (1) 14.509 (4) 14.478 (1) 13.890 (1) 14.220 (6) 20.424 ( 2291.8 (19) 3181.5 (7) 4726.7 (18) 1911.5(13) [(en)Pd(NO 3 ) 2 ] with pyridine-based bridging ligands, systems under kinetic control disfavour cyclization, while thermodynamic conditions facilitate the formation of macrocycles, due to signi®cant entropy effects that favour small cyclic structures over polymeric structures. 6d Cyclization was, therefore, observed to occur more readily in the presence of more labile metal±ligand bonds, at low reagent concentrations and at higher temperatures.…”

“…The 2,4'-bipy ligand is able to act as exo-bidentate with digonal metals as Ag(I), generating chains. 19 With 1, therefore, the only suitable coordination positions could be the two trans axial, but the weakness of the interactions along these directions leads to a different product. Noteworthy the mononuclear complexes are joined into one-dimensional chains (see Fig.…”

Molecular and electronic structure of several 2,3-dithienylquinoxalines and their 2:1 complexes with silver(I) nitrate

“…The nitrates involved in the metal bonding in these complexes show three variations: the nitrate may bind one oxygen to one silver [8], two oxygen to one silver [9,13], or two oxygen on one nitrate group may bridge two silvers on separate molecules [7]. The silver geometry is either linear or bent with the perturbation to non-linear geometries caused by the cation-anion interaction.…”

“…Preliminary observations have shown that weakly coordinating anions such as tend to be located near the silver [6,10]. However, several structures have seen nitrate-silver interactions that lead to: monodentate O-Ag bonding [8]; bidentate nonbridging O-Ag bonding [9,13]; and bidentate bridging bonding [7]. In Ag(1) 2 NO 3 , one nitrito group oxygen is within bonding distance to the silver at a distance of 2.461 (5) Å with the other at a distance of over 3 Å.…”

“…Molecular solids having Ag(L) + and ( ) 2 Ag L + structural units have shown a wide range of structural variation that is guided by a few basic principles. For example, mono-or bis-quinoxaline silver complexes tend to have linear geometries about Ag [6,7]; such complexes with heterocyclic aromatic ligands, tend to interact via π-π stacking interactions building higher dimensional structural networks [8,9]; their counteranions tend to direct extended structures through weak associations with the silver in the complex (e.g. 1 6 PF − , 1 4 BF − ) [6,10] or through direct coordination (e.g.…”