Abstract
A 6-chloro-nicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4'-bi-pyridine (4,4'-bpy), namely, catena-poly[[[tetra-aqua-nickel(II)]-μ-4,4'-bi-pyridine-κ2 N:N'] bis-(6-chloro-nicotinate) tetra-hydrate], {[Ni(C10H8N2)(H2O)4](C6H3ClNO2)2·4H2O} n or {[Ni(4,4'-bpy)(H2O)4](6-Clnic)2·4H2O} n , (1), was prepared by the reaction of nickel(II) sulfate hepta-hydrate, 6-chloro-nicotinic acid and 4,4'-bi-pyridine in a mixture of water and ethanol. The mol-ecular structure of 1 comprises a one-dimensional polymeric {[Ni(4,4'-bpy)(H2O)4]2+} n cation, two 6-chloro-nicotinate anions and four water mol-ecules of crystallization per repeating polymeric unit. The nickel(II) ion in the polymeric cation is octa-hedrally coordinated by four water mol-ecule O atoms and by two 4,4'-bi-pyridine N atoms in the trans position. The 4,4'-bi-pyridine ligands act as bridges and, thus, connect the symmetry-related nickel(II) ions into an infinite one-dimensional polymeric chain extending along the b-axis direction. In the extended structure of 1, the polymeric chains of {[Ni(4,4'-bpy)(H2O)4]2+} n , the 6-chloro-nicotinate anions and the water mol-ecules of crystallization are assembled into an infinite three-dimensional hydrogen-bonded network via strong O-H⋯O and O-H⋯N hydrogen bonds, leading to the formation of the representative hydrogen-bonded ring motifs: tetra-meric R 2 4(8) and R 4 4(10) loops, a dimeric R 2 2(8) loop and a penta-meric R 4 5(16) loop.
Highlights
Functional coordination polymers have attracted great interest in recent years, mostly due to their aesthetics and many interesting properties such as catalytic, magnetic and luminescent, potential for use in gas storage and separation, molecular sensing (Mueller et al, 2006; Bosch et al, 2017; Zhang et al, 2015; Zeng et al, 2014, 2016; Douvali et al, 2015; Xu et al, 2017; Zhou et al, 2017)
The design of functional coordination polymers with the desired structures is not always straightforward and is strongly dependent on the experimental conditions including the type of solvents, starting metal salts, additional ligands, temperature, hydrothermal conditions and pH value (Li et al, 2016; Zhou et al, 2016; Gu et al, 2016)
The nickel(II) ion in the polymeric {[Ni(4,40-bpy)(H2O)4]2+}n cation is octahedrally coordinated by four water molecule O atoms (O1, O2, O1i and O2i) [symmetry code: (i) Àx + 1, Ày + 1, Àz + 1] and by two 4,40-bipyridine N atoms (N1 and N1i) in the trans position (N1i—Ni1—N1 = 180)
Summary
Functional coordination polymers have attracted great interest in recent years, mostly due to their aesthetics and many interesting properties such as catalytic, magnetic and luminescent, potential for use in gas storage and separation, molecular sensing (Mueller et al, 2006; Bosch et al, 2017; Zhang et al, 2015; Zeng et al, 2014, 2016; Douvali et al, 2015; Xu et al, 2017; Zhou et al, 2017). The design of functional coordination polymers with the desired structures is not always straightforward and is strongly dependent on the experimental conditions including the type of solvents, starting metal salts, additional ligands, temperature, hydrothermal conditions and pH value (Li et al, 2016; Zhou et al, 2016; Gu et al, 2016). The crystal structures of only three metal complexes of 6-chloronicotinate (6-Clnic) are known so far (Xia et al, 2012a,b; Li et al, 2006). We have reported the synthesis, crystal structure and properties of a one-dimensional nickel(II) coordination polymer with mixed ligands: 6-fluoronicotinate as the main ligand and 4,40-bipyridine (4,40bpy) as the supporting ligand (Politeo et al, 2020). We were not able to prepare the desired nickel(II) coordination polymer under these experimental conditions, but instead we obtained a 6-chloronicotinate salt of a onedimensional cationic nickel(II) coordination polymer with 4,40-bipyridine, namely the title compound, {[Ni(4,40bpy)(H2O)4](6-Clnic)2Á4H2O}n, (1)
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