Abstract
A copper(II) dimer with the deprotonated anion of 2-bromo-nicotinic acid (2-BrnicH), namely, tetrakis(μ-2-bromonicotinato-κ2 O:O')bis[aquacopper(-II)](Cu-Cu), [Cu2(H2O)2(C6H3BrNO2)4] or [Cu2(H2O)2(2-Brnic)4], (1), was prepared by the reaction of copper(II) chloride dihydrate and 2-bromo-nicotinic acid in water. The copper(II) ion in 1 has a distorted square-pyramidal coordination environment, achieved by four carboxyl-ate O atoms in the basal plane and the water mol-ecule in the apical position. The pair of symmetry-related copper(II) ions are connected into a centrosymmetric paddle-wheel dinuclear cluster [Cu⋯Cu = 2.6470 (11) Å] via four O,O'-bridging 2-bromo-nicotinate ligands in the syn-syn coordination mode. In the extended structure of 1, the cluster mol-ecules are assembled into an infinite two-dimensional hydrogen-bonded network lying parallel to the (001) plane via strong O-H⋯O and O-H⋯N hydrogen bonds, leading to the formation of various hydrogen-bond ring motifs: dimeric R 2 2(8) and R 2 2(16) loops and a tetra-meric R 4 4(16) loop. The Hirshfeld surface analysis was also performed in order to better illustrate the nature and abundance of the inter-molecular contacts in the structure of 1.
Highlights
Copper(II) carboxylates have been studied extensively because of their structural diversity and related possible applications
Polynuclear copper(II) carboxylates have gained much interest in recent years (Zhu et al, 2010; Zhang et al, 2010; Sheikh et al, 2013), for example the copper(II) metal–organic framework containing benzene-1,3,5-tricarboxylate (HKUST1) is based on dinuclear paddle-wheel copper(II) moieties, with interesting magnetic properties (Chui et al, 1999; Pichon et al, 2007; Furukawa et al, 2008). These paddle-wheel copper(II) moieties have frequently been used in the design of coordination polymers and MOFs as secondary building units (SBU) (Baca et al, 2008; Roubeau & Clerac, 2008; Bai et al, 2008)
Nicotinic acid has been widely used as a complexing agent for various metal ions and many crystal structures of its metal complexes have been reported and deposited in the Cambridge Structural Database (CSD, Version 5.40, searched October 2019; Groom et al, 2016)
Summary
Copper(II) carboxylates have been studied extensively because of their structural diversity and related possible applications. Polynuclear copper(II) carboxylates have gained much interest in recent years (Zhu et al, 2010; Zhang et al, 2010; Sheikh et al, 2013), for example the copper(II) metal–organic framework containing benzene-1,3,5-tricarboxylate (HKUST1) is based on dinuclear paddle-wheel copper(II) moieties, with interesting magnetic properties (Chui et al, 1999; Pichon et al, 2007; Furukawa et al, 2008). These paddle-wheel copper(II) moieties have frequently been used in the design of coordination polymers and MOFs as secondary building units (SBU) (Baca et al, 2008; Roubeau & Clerac, 2008; Bai et al, 2008). Derivatives [2-chloronicotinate, 2-methoxynicotinate, 2-ethoxynicotinate and 2-(naphthalen-2-ylmethylsulfanyl)nicotinate] as carboxylates (Moncol et al, 2007; Jun, Lu et al, 2013; Jun, Wei-Ping et al, 2013; Adhikari et al, 2016)
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