Synthesis, crystal structure and magnetic properties of a two-dimensional cyanide-based heterometallic coordination polymer with cationic piperazinium ligands: poly[aqua­tetra-μ₂-cyanido-κ⁸C:N-dicyan­ido-κ²C-(piperazinium-κN⁴)cobalt(III)copper(II)]

Cyanide as a bridge can be used to construct homo- and heterometallic complexes with intriguing structures and inter­esting magnetic properties. These ligands can generate diverse structures, including clusters, one-dimensional chains, two-dimensional layers and three-dimensional frameworks. The title cyanide-bridged Cu^II–Co^III heterometallic compound, [Cu^IICo^III(CN)₆(C₄H₁₁N₂)(H₂O)]_n, has been synthesized and characterized by single-crystal X-ray diffraction analysis, magnetic measurement, thermal study, vibrational spectroscopy (FT–IR) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM–EDS). The crystal structure analysis revealed that it has a two-dimensional grid-like structure built up of [Cu(Hpip)(H₂O)]³⁺ cations (Hpip is piperazinium) and [Co(CN)₆]³⁻ anions that are linked through bridging cyanide ligands. The overall three-dimensional supra­molecular network is expanded by a combination of inter­layer O—H...N and N—H...O hydrogen bonds involving the coordinated water mol­ecules and the N atoms of the nonbridging cyanide groups and monodentate cationic piperazinium ligands. A magnetic investigation shows that anti­ferromagnetic inter­actions exist in the title compound.

S1. Introduction

In recent decades, much inter­est has been focused on using cyanide as a bridge to construct homo- and heterometallic complexes with intriguing structures and inter­esting magnetic properties (Dunbar & Heintz, 1997; Ohba & Okawa, 2000; Ni et al., 2005; Kou et al., 2003; Alexandros et al., 2012). It is well known that hexa­cyano­metallate, [Co(CN)₆]^3-, is a good building block for the assembly of multidimensional architectures. The cyanide groups can partly or fully participate in the formation of coordination bonds with various metal ions to generate diverse structures including clusters, one-dimensional (1D) chains, two-dimensional (2D) layers and three-dimensional (3D) frameworks (Tanase & Reedijk, 2006; Shao & Yu, 2014; Mondal et al., 2001; Keene et al., 2011; Sima & Zhang, 2011). However, the further development of cyanide-bridged complex systems is obstructed by the limited availability of cationic assembled units of the general formula [ML_x(H₂O)_m]ⁿ⁺ (M is a divalent transition metal ion and L is a polydentate ligand, such as a polyamine, a Schiff base or a macrocyclic ligand) ( Nemec et al., 2011; Sereda et al., 2008; Samanta et al., 2007; Qin et al., 2013). In recent years, our group, amongst others, have focused on the exploitation of new cyanide-containing building blocks by the introduction of nitro­gen heterocyclic ring compounds as co-ligands. Here, the N-heterocyclic ligands are good molecular building blocks and co-ligands in constructing metal–organic frameworks (MOFs) with inter­esting structures and properties (Piromchom et al., 2013; Sereda & Stoeckli-Evans, 2008; Shen, 2014; Qin et al., 2012). Of the potential N-heterocyclic ligands, piperazine has been investigated relatively infrequently in the field of cyano­metallates. A search of the Cambridge Structural Database (CSD, Version 5.34; Groom & Allen, 2014) revealed 25 crystal structures of monometallic CuCN-based compounds involving piperazine and its derivatives, but only three concerning piperazine itself. Two-dimensional heterometallic cyanide coordination polymers based on protonated piperazine have been reported (Lim et al., 2008; Stocker et al., 1999; Pike et al., 2007). In this paper, we report a cyanide-bridged Cu^II–Co^III heterometallic 2D grid-like structure, in which the protonated piperazine ligand coordinates to the copper centre in a monodentate mode to form cation [Cu(Hpip)(H₂O)]³⁺ building blocks. Moreover, adjacent independent 2D (4,4) layers are further extended into a 3D supra­molecular structure by weak O—H···N and N—H···O hydrogen-bond inter­actions.

S2. Experimental

All chemicals were analytically pure and were obtained from commercial sources and used without further purification. Elemental analyses were performed on a Vario EL—II analyzer. FT–IR spectra were recorded from KBr pellets in the range 4000–400 cm^-1 on a PerkinElmer Spectrum BX FT–IR spectrometer. Powder X-ray diffraction (PXRD) data were measured using a Bruker D8 Advance diffractometer. Magnetic measurements were made with Quantum Design SQUID MPMS XL-5 instruments. The diamagnetic correction for each sample was applied using Pascal's constants. A scanning electron microscope Energy-disperse X-ray spectroscopy (SEM–EDS) analysis was carried out on a JSM-7500F equipped with an EDAX CDU leap detector. The thermogravimetric analysis (TG–DTA) was carried out inder an air atmosphere using SETARAM LABSYS equipment at a heating rate of 10 K min^-1.

S2.1. Synthesis and crystallization

A mixture of CuCl₂·2H₂O (0.068 g, 0.4 mmol), K₃[Co(CN)₆] (0.133 g, 0.4 mmol), piperazine (0.073 g, 0.9 mmol) in a molar ratio of 1.0:1.0:2.25 and CH₃CN (3 ml) and water (3 ml) was sealed in a 15 ml Teflon-lined stainless steel container (pH ≈ 7.5) and heated to 433 K for 6 d. After cooling to room temperature at a rate of 5 K h^-1, and filtration, red bar-shaped crystals were recovered in a yield of 40% (based on CuCl₂·2H₂O). Analysis calculated for C₁₀H₁₃CoCuN₈O: C 31.30, H 3.41, N 29.20%; found: C 31.23, H 3.56, N 29.18%. IR (KBr disk, cm^-1): ν(N—H) 3369 (w), 3342 (w); ν(O—H) 3304 (w), 3286 (w); ν(C—H) 2966 (w), 2923 (w), 2874 (w); ν(C≡N) 2174 (s), 2114 (s); δ(H—O—H) 1586 (m), 1580 (m).

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. H atoms bonded to C atoms or to N atoms of the piperazine ligand were placed in calculated positions and refined using a riding model, with C—H = 0.97 Å and N—H = 0.91 (NH) or 0.90 Å (NH₂). The isotropic displacement parameters of these H atoms were constrained to 1.2U_eq of their parent atoms. Water H atoms were located by difference Fourier synthesis. They were constrained to ride on their parent O atom with rotation about the Cu—O bond, with O—H = 0.88 Å and U_iso(H) = 1.5U_eq(O).

S3. Results and discussion

S3.1. Crystal structure

The crystal structure analysis of compound (I) revealed that it has a cyanide-bridged two-dimensional (2D) grid-like layer structure, in which each [Co(CN)₆]^3- anion unit links to four adjacent [Cu(Hpip)(H₂O)]³⁺ cations through four µ₂-cyanide groups. Compound (I) crystallizes in the orthorhombic space group Pbcm (Table 1), and the asymmetric unit contains half a crystallographically independent Cu^II centre, half a Co^III centre, three cyanide groupss, half a terminal water molecule and half a protonated piperazine cation (Fig. 1). The Co^III atom lies on a twofold rotation axis and shows an o­cta­hedral geometry, coordinated by four µ₂-cyanide C atoms and two terminal cyanide C atoms. The Co1—C bond lengths are in the range 1.892 (3)–1.900 (3) Å and the corresponding cis- and trans-L—Co1—L (L = cyanide) angles are in the ranges 88.35 (13)–92.20 (13) and 178.01 (11)–179.22 (18)°, respectively, suggesting a distorted o­cta­hedral geometry. The Cu^II centres lie on crystallographic mirror planes but also adopt o­cta­hedral coordination geometry, with each coordinated by four µ₂-cyanide N atoms, one terminal N atom from a protonated piperazine cation and one O atom from a coordinated water molecule.The Cu1—N(cyanide) bond lengths in the equatorial plane are in the range 2.100 (3)–2.107 (3) Å. The axial bond lengths Cu1—N4 and Cu1—O1W of 2.239 (4) and 2.138 (3) Å, respectively, may be attributed to strong Jahn–Teller effects. The corresponding cis- and trans-L—Cu1—L (L = N or O) angles are in the ranges 85.36 (10)–94.53 (10) and 179.18 (13)–179.86 (12)°, respectively, also suggesting a distorted o­cta­hedral geometry. The cyanide groups in complex (I) have versatile bonding modes and can act as mono- or bidentate bridged ligands. The bridged C1—N1, C2—N2 and monodentate C3—N3 distances of 1.146 (4), 1.144 (4) and 1.148 (5) Å are typical C≡N bond lengths for such cyanide ligands. According to the literature, the Co—C and C≡N bond-length ranges given are well matched with the corresponding values in reported complexes such as [Cu(dmpn1)₂]₃[Co(CN)₆]₂·12H₂O, [Cu(dmpn2)₂]₂[Co(CN)₆]ClO₄·3H₂O and [(CuL)[Co(CN)₆](CuL)]ClO₄·3.5H₂O {L = (3E,5E)-N¹,N⁴-bis­[(pyridin-2-yl)methyl­ene]butane-1,4-di­amine; Mondal et al., 2001; Samanta et al., 2007}. For the piperazine ligand, the N5—C5/C5^iv bond lengths [1.494 (5) Å] are a little longer than the N4—C4/C4^iv bond lengths [1.476 (4) Å] and the C5—N5–C5^iv angle [111.7 (4)°] is a little wider than the C4—N4—C4^iv angle [109.3 (4)°] [symmetry codes: (iv) x, y, ∓1/2]. These values are similar to those in [Cu₂(CN)₃(Hpip)] (Stocker et al., 1999), where the protonated N—C bond lengths (1.490 and 1.486 Å) are a little longer than the neutral N–C- bond lengths (1.466 and 1.468 Å) and the corresponding C—N—C angles (111.2 and 110.5°) also show similar differences. The above results confirm that the piperazine is protonated in (I) as the protonation of noncoordinated N atom may engender a change in the geometry of the piperazine. In contrast, in (CuCN)₂(pip), the N—C bond lengths (1.471 Å) are identical and the C—N—C angles (109.7°) are also alike (Stocker et al., 1999). From reported structures of copper(I) cyanide networks with bridging piperazine ligands, the piperazine ligands have neutral or protonated modes and act as bidentate–bridged or monodentate–terminal ligands, respectively. For example, in [Cu₂(CN)₃(Hpip)] (Stocker et al., 1999), the protonated piperazine ligands act as monodentate ligand bonding to Cu atoms and compensating for the negative charge, however, in (CuCN)₂(pip) (Stocker et al., 1999) and (CuCN)₂₀(piperazine)₇ (Pike et al., 2007), they act as bridging spacers between two Cu atoms.

Similar to [Cu₂(CN)₃(Hpip)], the cationic [Cu(Hpip)(H₂O)]³⁺ unit of (I) formed by protonated piperazine linking to the metal Cu^II centre, contains a protonated piperazine ligand that exhibits a monodentate coordination mode and acts as a charge-compensator. It should be noted here that the piperazine is also essential for the generation of complex (I) because it also acts as a pH regulator under the solvothermal reaction conditions used. Each [Co(CN)₆]^3- unit is connected to four neighbouring [Cu(Hpip)(H₂O)]³⁺ cation units, while each [Cu(Hpip)(H₂O)]³⁺ cation unit is in turn linked to four neighbouring [Co(CN)₆]^3- anion units. The bridging by µ₂-cyanide ligands combines to form a netural 2D (4,4) square-grid corrugated layer (Fig. 2). It is noted that although this 2D structure is analogous to Hofmann-type clathrates, the structural features are different. The Hofmann-type and its analouges are built by CN-binding between square-planar or tetra­hedral tetra­cyano­metallate(II) units and o­cta­hedral metal(II) units combined with auxiliary ligands. Hofmann-type complexes are determined by the general formula [ML₂M'(CN)₄] (M^II = Mn, Fe, Co, Ni, Cu, Zn or Cd; M'^II = Ni, Pd or Pt; L is a monodentate ligand) (Černák & Abboud, 2000; Tokoro et al., 2007; Potočňák et al., 2007).

S3.2. Topology

To better understand this network from a topological point of view, the centres of the Co^III and Cu^II ions are considered as four-connected nodes and the µ₂-cyanide fragments as linkers. In this description, compound (I) has 4-connected uninodal Shubnikov tetra­gonal plane net with short Schläfli symbol {4⁴.6²}, as indicated by using TOPOS software (Blatov, 2006). The basic units in the layer are 12-membered [Cu₂Co₂(CN)₄] rings in which the different nodes are linked by cyanide ligands to form nonplanar 2D (4,4) sheets (Fig. 3). These layers are packed in an offset ABAB fashion to generate a 3D supra­molecular structure through a range of O1W—H1WA···N3ⁱ, O1W—H1WB···N3ⁱⁱ and N5—H5A···O1Wⁱⁱⁱ [symmetry codes: (i) -x, -y+2, -z+1; (ii) -x, -y+2, z-1/2; (iii) -x+1, y-1/2, -z+1/2] hydrogen bonds involving the coordinated terminal water molecules, the N atoms of the nonbridging cyanide groups and the terminal N atoms of protonated piperazine cation (Figs. 4 and 5, and Table 2). Until now, only a few examples of cyanide-bridged Cu^II–Co^III heterometallic coordination compounds with a polyamine as a co-ligand have been investigated. For example, the cyanide-bridged complexes [Cu(dmpn1)₂]₃[Co(CN)₆]₂·12H₂O and [Cu(dmpn1)₂]₂[Co(CN)₆]·ClO₄·3H₂O (dmpn1 is 1-di­methyl­amino-2-propyl­amine) are built up from two complementary building blocks, viz. [Co(CN)₆]^3- and [Cu(dmpn1)₂]²⁺ ions (Mondal et al., 2001). The trinuclear heterobimetallic compound [(CuL)[Co(CN)₆](CuL)]ClO₄·3.5H₂O {L is (3E,5E)-N¹,N⁴-bis­[(pyridin-2-yl)methyl­ene]butane-1,4-di­amine} is constructed with two adjacent (CuL)²⁺ cations through two trans-cyanide N atoms of [Co(CN)₆]^3- anions (Samanta et al.,2007). The compound [{(Cu(dien))₂Co(CN)₆}_n][Cu(dien)(H₂O)Co(CN)₆]_n·5nH₂O (dien is di­ethyl­enetri­amine) consists of one-dimensional cationic {[(Cu(dien))₂Co(CN)₆]_n}ⁿ⁺ chains and discrete binuclear anionic [(H₂O)(dien)Cu–NC–Co(CN)₅]^- units (Ferbinteanu et al., 1999).

S3.3. IR analysis

The most prominent features in the IR spectrum of compound (I) are the strong sharp absorption bands at 2147 and 2114 cm^-1, which indicate the existence of two types of cyanide groups. The lower wavenumber band of 2114 cm^-1 can be assigned to a terminal cyanide ligand, while the higher band at 2147 cm^-1 is attributed to the stretching vibration of a linear bridging cyanide ligand (Sharpe, 1976; Mondal et al., 2001; Samanta et al., 2007). The multiple bands in the range 3369–3286 cm^-1 are attributed to the ν(O—H) and ν(N—H) stretching vibrations. Compared with the usual reports for free ν(N—H) stretching vibrations of piperazine groups at 3430 cm^-1, this peak shifts to lower wavenumber in (I) presumably due to hydrogen-bonding inter­actions (Stocker et al., 1999). Additional absorption bands around 2966–2874 cm^-1 are ascribed to the vibration of the C—H groups of piperazine (Li et al., 2010). Sharp bands at 1586 and 1580 cm^-1 for complex (I) may be attributed to hydrogen-bonding inter­actions (Mondal et al., 2001; Samanta et al., 2007).

S3.4. SEM, EDS and XRPD analyses

SEM examination indicates that crystals of the pristine compound (I) possess a bar shape and relatively clean surface. EDS analysis clearly exhibits signals arising from the heterometallic Cu^II and Co^III atoms that exist in (I). This gives rise to a Cu–Co molar ratio is 0.98:1.03 in compound (I), which is largely in agreement with the single-crystal diffraction data (Fig. 6). The XRPD of compound (I) was measured to check the bulk purity. The recorded and simulated XRPD patterns are quite similar, confirming the bulk purity of compound (I).

S3.5. Thermogravimetric analysis

In order to examine the thermal stabilities of compound (I), thermogravimetric (TG) and differential thermal analyses (DTA) were carried out under an air atmosphere and under a pressure of 1 atm at a heating rate of 10 K min^-1. As shown in Fig. 7, the TG curve shows that compound (I) is stable up to 563 K. The DTA curve shows one exothermic peak (calculated 708 K). The first weight loss of 25.0% within the range 563–623 K corresponds to the removal of the protonated piperazine ligand and one water molecule (calculated 27.3%). This is followed by decomposition of the framework. Within the temperature range 623–873 K, the continuous removal of cyanide groups gives an unstable inter­mediate that is slowly oxidized in air upon further heating. The weight of the solid residue (found 43.30%; calculated 42.3%) is consistent with mixture of CuO (tenorite) and Co₂O₃ phases. The residue observed in the TG analysis of (I) is thus in agreement with previously reported compounds. For example, the cyanide-bridged heteronuclear complexes [Cu(dmpn1)₂]₃[Co(CN)₆]₂·12H₂O, [Cu(dmpn1)₂]₂[Co(CN)₆]·ClO₄·3H₂O (dmpn1 is 1-di­methyl­amino-2-propyl­amine; Mondal et al., 2001) and {[Cu^II(dmpn2)₂]₃[Co^III(CN)₆]₂·6H₂O}_n (dmpn2 = 2,2-di­methyl-1,3-di­amino­propane; Biswas et al., 2014), in which the final decomposition products were identified as CuO and Co₂O₃ phases. For other types of heterometallic compounds, e.g. [Ni(bpy)₃][Cu(CN)₃]·4.5H₂O and [Cu(bpy)₂(CN)]₂[Ni(CN)₄]·4H₂O (Kočanová et al., 2010), the solid residues are formed of a mixture of CuO and NiO.

S3.6. Magnetic investigation

The temperature dependence of the magnetic susceptibility of compound (I) in the temperature range 2–300 K under an applied field of 1000 Oe was measured on a Quantum Design SQUID MPMS XL-5 (Fig. 8). In compound (I), Co^III atoms with a d⁶ configuration are diamagnetic because the six d electrons are all paired under an o­cta­hedral crystal field of [Co(CN)₆]^3-. The χ_mT value at 300 K is 0.399 cm³ K mol^-1 for compound (I), which is slightly larger than that expected 0.375 cm³ K mol^-1 for an uncoupled Cu^II ion with g = 2.0. The χ_mT value decreases slowly with decreasing temperature until 25 K. After that, the χ_mT value rapidly decreases with lowering temperature down to a value of 0.11 cm³ K mol^-1 for compound (I) at 2.0 K. The fitting of Curie–Weiss law in the temperature range 50–300 K gives C = 0.408 cm³ K mol^-1 and θ = -8.60 K, and this gives rise to an average g value of 2.08 for (I). The negative θ values indicate that anti­ferromagnetic coupling dominates these systems. The field-dependent magnetization at 2 K increases slowly and linearly with the applied field, and no saturation is observed. The magnetization value at the highest field of 50 KOe is 0.77 Nβ for compound (I), close to the saturation value of 1.0 Nβ expected for one spin-only Cu^II species (Fig. 9). This observation suggests a weak anti­ferromagnetic inter­action between the Cu^II ions through the diamagnetic –NC—Co—CN– bridge. As far as we known, a number of examples of bimetallic systems containing diamagnetic [Co(CN)₆]^3- bridging ligands between paramagnetic ions with only e_g-type magnetic orbitals have been reported so far. For compounds PPh₄[Ni(pn)₂][Co(CN)₆]·H₂O (Ohba et al., 1998), [Ni(en)₂]₃[Co(CN)₆]₂·2H₂O (Ohba et al., 1997), [{Cu(dien)₂Co(CN)₆}_n][Cu(dien)(H₂O)Co(CN)₆]_n·5H₂O (Ferbinteanu et al., 1999), [(CuL)[Co(CN)₆](CuL)]ClO₄·3.5H₂O {L is (3E,5E)-N¹,N⁴-bis­[(pyridin-2-yl)methyl­ene]butane-1,4-di­amine; Samanta et al., 2007}, {[Cu^II(dmpn2)₂]₃[Co^III(CN)₆]₂·6H₂O}_n (Biswas et al., 2014) and [Cu(en)₂Li(H₂O)][Co(CN)₆] (en is ethyl­enedi­amine; Sima & Zhang, 2011), showing very weak anti­ferromagnetic coupling, as expected from the diamagnetic long chain –NC—Co—CN– bridges. In addition, we also note several copper(II) system compounds with diamagnetic [M(CN)₄]^2- (M = Ni, Pd or Pt) and diamagnetic [Ag(CN)₂]^- bridging ligands. For example, compounds [Cu(bpy)₂(CN)]₂[Ni(CN)₄]·4H₂O (Kočanová et al., 2010), [Cu(dpt)Pd(CN)₄]_n, {[Cu₂(medpt)₂Pd(CN)₄](ClO₄)₂·3H₂O}_n, {[Cu₂(dien)₂Pd(CN)₄](ClO₄)₂·2CH₃OH}_n, {[Cu₂(iPrdien)₂Pd(CN)₄](ClO₄)₂·2H₂O}_n (dpt is 3,3'-imino­bis­propyl­amine, medpt is 3,3'-di­amino-N-methyl­dipropyl­amine; dien is di­ethyl­enetri­amine and iprdien is N'-iso­propyldi­ethyl­enetri­amine; Manna et al., 2007), and [Cu(NH₃)₂Ag₂(CN)₄] (Vlček et al., 2007), which also present weak anti­ferromagnetic exchange inter­actions.

S4. Conclusions

A new cyanide-bridged heterometallic Cu^II–Co^III coordination polymer [Cu^IICo^III(CN)₆(Hpip)(H₂O)], (I), has been synthesized by the reaction of CuCl₂·2H₂O with K₃[Co(CN)₆] and piperazine under solvothermal conditions. X-ray diffraction analysis reveals a two-dimensional layer structure constructed by [Cu(Hpip)(H₂O)]³⁺ cations and [Co(CN)₆]^3- anions, in which the [Cu(Hpip)(H₂O)]³⁺ cation is formed by protonated piperazine as charge-balance agent binding to the copper centre. These layers are further packed in an ABAB fashion through O—H···N and N—H···O hydrogen-bonding inter­actions to generate a 3D supra­molecular structure. In addition, magnetic investigations show that anti­ferromagnetic inter­actions exist in compound (I).

Structure description

In recent decades, much inter­est has been focused on using cyanide as a bridge to construct homo- and heterometallic complexes with intriguing structures and inter­esting magnetic properties (Dunbar & Heintz, 1997; Ohba & Okawa, 2000; Ni et al., 2005; Kou et al., 2003; Alexandros et al., 2012). It is well known that hexa­cyano­metallate, [Co(CN)₆]^3-, is a good building block for the assembly of multidimensional architectures. The cyanide groups can partly or fully participate in the formation of coordination bonds with various metal ions to generate diverse structures including clusters, one-dimensional (1D) chains, two-dimensional (2D) layers and three-dimensional (3D) frameworks (Tanase & Reedijk, 2006; Shao & Yu, 2014; Mondal et al., 2001; Keene et al., 2011; Sima & Zhang, 2011). However, the further development of cyanide-bridged complex systems is obstructed by the limited availability of cationic assembled units of the general formula [ML_x(H₂O)_m]ⁿ⁺ (M is a divalent transition metal ion and L is a polydentate ligand, such as a polyamine, a Schiff base or a macrocyclic ligand) ( Nemec et al., 2011; Sereda et al., 2008; Samanta et al., 2007; Qin et al., 2013). In recent years, our group, amongst others, have focused on the exploitation of new cyanide-containing building blocks by the introduction of nitro­gen heterocyclic ring compounds as co-ligands. Here, the N-heterocyclic ligands are good molecular building blocks and co-ligands in constructing metal–organic frameworks (MOFs) with inter­esting structures and properties (Piromchom et al., 2013; Sereda & Stoeckli-Evans, 2008; Shen, 2014; Qin et al., 2012). Of the potential N-heterocyclic ligands, piperazine has been investigated relatively infrequently in the field of cyano­metallates. A search of the Cambridge Structural Database (CSD, Version 5.34; Groom & Allen, 2014) revealed 25 crystal structures of monometallic CuCN-based compounds involving piperazine and its derivatives, but only three concerning piperazine itself. Two-dimensional heterometallic cyanide coordination polymers based on protonated piperazine have been reported (Lim et al., 2008; Stocker et al., 1999; Pike et al., 2007). In this paper, we report a cyanide-bridged Cu^II–Co^III heterometallic 2D grid-like structure, in which the protonated piperazine ligand coordinates to the copper centre in a monodentate mode to form cation [Cu(Hpip)(H₂O)]³⁺ building blocks. Moreover, adjacent independent 2D (4,4) layers are further extended into a 3D supra­molecular structure by weak O—H···N and N—H···O hydrogen-bond inter­actions.

All chemicals were analytically pure and were obtained from commercial sources and used without further purification. Elemental analyses were performed on a Vario EL—II analyzer. FT–IR spectra were recorded from KBr pellets in the range 4000–400 cm^-1 on a PerkinElmer Spectrum BX FT–IR spectrometer. Powder X-ray diffraction (PXRD) data were measured using a Bruker D8 Advance diffractometer. Magnetic measurements were made with Quantum Design SQUID MPMS XL-5 instruments. The diamagnetic correction for each sample was applied using Pascal's constants. A scanning electron microscope Energy-disperse X-ray spectroscopy (SEM–EDS) analysis was carried out on a JSM-7500F equipped with an EDAX CDU leap detector. The thermogravimetric analysis (TG–DTA) was carried out inder an air atmosphere using SETARAM LABSYS equipment at a heating rate of 10 K min^-1.

The crystal structure analysis of compound (I) revealed that it has a cyanide-bridged two-dimensional (2D) grid-like layer structure, in which each [Co(CN)₆]^3- anion unit links to four adjacent [Cu(Hpip)(H₂O)]³⁺ cations through four µ₂-cyanide groups. Compound (I) crystallizes in the orthorhombic space group Pbcm (Table 1), and the asymmetric unit contains half a crystallographically independent Cu^II centre, half a Co^III centre, three cyanide groupss, half a terminal water molecule and half a protonated piperazine cation (Fig. 1). The Co^III atom lies on a twofold rotation axis and shows an o­cta­hedral geometry, coordinated by four µ₂-cyanide C atoms and two terminal cyanide C atoms. The Co1—C bond lengths are in the range 1.892 (3)–1.900 (3) Å and the corresponding cis- and trans-L—Co1—L (L = cyanide) angles are in the ranges 88.35 (13)–92.20 (13) and 178.01 (11)–179.22 (18)°, respectively, suggesting a distorted o­cta­hedral geometry. The Cu^II centres lie on crystallographic mirror planes but also adopt o­cta­hedral coordination geometry, with each coordinated by four µ₂-cyanide N atoms, one terminal N atom from a protonated piperazine cation and one O atom from a coordinated water molecule.The Cu1—N(cyanide) bond lengths in the equatorial plane are in the range 2.100 (3)–2.107 (3) Å. The axial bond lengths Cu1—N4 and Cu1—O1W of 2.239 (4) and 2.138 (3) Å, respectively, may be attributed to strong Jahn–Teller effects. The corresponding cis- and trans-L—Cu1—L (L = N or O) angles are in the ranges 85.36 (10)–94.53 (10) and 179.18 (13)–179.86 (12)°, respectively, also suggesting a distorted o­cta­hedral geometry. The cyanide groups in complex (I) have versatile bonding modes and can act as mono- or bidentate bridged ligands. The bridged C1—N1, C2—N2 and monodentate C3—N3 distances of 1.146 (4), 1.144 (4) and 1.148 (5) Å are typical C≡N bond lengths for such cyanide ligands. According to the literature, the Co—C and C≡N bond-length ranges given are well matched with the corresponding values in reported complexes such as [Cu(dmpn1)₂]₃[Co(CN)₆]₂·12H₂O, [Cu(dmpn2)₂]₂[Co(CN)₆]ClO₄·3H₂O and [(CuL)[Co(CN)₆](CuL)]ClO₄·3.5H₂O {L = (3E,5E)-N¹,N⁴-bis­[(pyridin-2-yl)methyl­ene]butane-1,4-di­amine; Mondal et al., 2001; Samanta et al., 2007}. For the piperazine ligand, the N5—C5/C5^iv bond lengths [1.494 (5) Å] are a little longer than the N4—C4/C4^iv bond lengths [1.476 (4) Å] and the C5—N5–C5^iv angle [111.7 (4)°] is a little wider than the C4—N4—C4^iv angle [109.3 (4)°] [symmetry codes: (iv) x, y, ∓1/2]. These values are similar to those in [Cu₂(CN)₃(Hpip)] (Stocker et al., 1999), where the protonated N—C bond lengths (1.490 and 1.486 Å) are a little longer than the neutral N–C- bond lengths (1.466 and 1.468 Å) and the corresponding C—N—C angles (111.2 and 110.5°) also show similar differences. The above results confirm that the piperazine is protonated in (I) as the protonation of noncoordinated N atom may engender a change in the geometry of the piperazine. In contrast, in (CuCN)₂(pip), the N—C bond lengths (1.471 Å) are identical and the C—N—C angles (109.7°) are also alike (Stocker et al., 1999). From reported structures of copper(I) cyanide networks with bridging piperazine ligands, the piperazine ligands have neutral or protonated modes and act as bidentate–bridged or monodentate–terminal ligands, respectively. For example, in [Cu₂(CN)₃(Hpip)] (Stocker et al., 1999), the protonated piperazine ligands act as monodentate ligand bonding to Cu atoms and compensating for the negative charge, however, in (CuCN)₂(pip) (Stocker et al., 1999) and (CuCN)₂₀(piperazine)₇ (Pike et al., 2007), they act as bridging spacers between two Cu atoms.

Similar to [Cu₂(CN)₃(Hpip)], the cationic [Cu(Hpip)(H₂O)]³⁺ unit of (I) formed by protonated piperazine linking to the metal Cu^II centre, contains a protonated piperazine ligand that exhibits a monodentate coordination mode and acts as a charge-compensator. It should be noted here that the piperazine is also essential for the generation of complex (I) because it also acts as a pH regulator under the solvothermal reaction conditions used. Each [Co(CN)₆]^3- unit is connected to four neighbouring [Cu(Hpip)(H₂O)]³⁺ cation units, while each [Cu(Hpip)(H₂O)]³⁺ cation unit is in turn linked to four neighbouring [Co(CN)₆]^3- anion units. The bridging by µ₂-cyanide ligands combines to form a netural 2D (4,4) square-grid corrugated layer (Fig. 2). It is noted that although this 2D structure is analogous to Hofmann-type clathrates, the structural features are different. The Hofmann-type and its analouges are built by CN-binding between square-planar or tetra­hedral tetra­cyano­metallate(II) units and o­cta­hedral metal(II) units combined with auxiliary ligands. Hofmann-type complexes are determined by the general formula [ML₂M'(CN)₄] (M^II = Mn, Fe, Co, Ni, Cu, Zn or Cd; M'^II = Ni, Pd or Pt; L is a monodentate ligand) (Černák & Abboud, 2000; Tokoro et al., 2007; Potočňák et al., 2007).

To better understand this network from a topological point of view, the centres of the Co^III and Cu^II ions are considered as four-connected nodes and the µ₂-cyanide fragments as linkers. In this description, compound (I) has 4-connected uninodal Shubnikov tetra­gonal plane net with short Schläfli symbol {4⁴.6²}, as indicated by using TOPOS software (Blatov, 2006). The basic units in the layer are 12-membered [Cu₂Co₂(CN)₄] rings in which the different nodes are linked by cyanide ligands to form nonplanar 2D (4,4) sheets (Fig. 3). These layers are packed in an offset ABAB fashion to generate a 3D supra­molecular structure through a range of O1W—H1WA···N3ⁱ, O1W—H1WB···N3ⁱⁱ and N5—H5A···O1Wⁱⁱⁱ [symmetry codes: (i) -x, -y+2, -z+1; (ii) -x, -y+2, z-1/2; (iii) -x+1, y-1/2, -z+1/2] hydrogen bonds involving the coordinated terminal water molecules, the N atoms of the nonbridging cyanide groups and the terminal N atoms of protonated piperazine cation (Figs. 4 and 5, and Table 2). Until now, only a few examples of cyanide-bridged Cu^II–Co^III heterometallic coordination compounds with a polyamine as a co-ligand have been investigated. For example, the cyanide-bridged complexes [Cu(dmpn1)₂]₃[Co(CN)₆]₂·12H₂O and [Cu(dmpn1)₂]₂[Co(CN)₆]·ClO₄·3H₂O (dmpn1 is 1-di­methyl­amino-2-propyl­amine) are built up from two complementary building blocks, viz. [Co(CN)₆]^3- and [Cu(dmpn1)₂]²⁺ ions (Mondal et al., 2001). The trinuclear heterobimetallic compound [(CuL)[Co(CN)₆](CuL)]ClO₄·3.5H₂O {L is (3E,5E)-N¹,N⁴-bis­[(pyridin-2-yl)methyl­ene]butane-1,4-di­amine} is constructed with two adjacent (CuL)²⁺ cations through two trans-cyanide N atoms of [Co(CN)₆]^3- anions (Samanta et al.,2007). The compound [{(Cu(dien))₂Co(CN)₆}_n][Cu(dien)(H₂O)Co(CN)₆]_n·5nH₂O (dien is di­ethyl­enetri­amine) consists of one-dimensional cationic {[(Cu(dien))₂Co(CN)₆]_n}ⁿ⁺ chains and discrete binuclear anionic [(H₂O)(dien)Cu–NC–Co(CN)₅]^- units (Ferbinteanu et al., 1999).

The most prominent features in the IR spectrum of compound (I) are the strong sharp absorption bands at 2147 and 2114 cm^-1, which indicate the existence of two types of cyanide groups. The lower wavenumber band of 2114 cm^-1 can be assigned to a terminal cyanide ligand, while the higher band at 2147 cm^-1 is attributed to the stretching vibration of a linear bridging cyanide ligand (Sharpe, 1976; Mondal et al., 2001; Samanta et al., 2007). The multiple bands in the range 3369–3286 cm^-1 are attributed to the ν(O—H) and ν(N—H) stretching vibrations. Compared with the usual reports for free ν(N—H) stretching vibrations of piperazine groups at 3430 cm^-1, this peak shifts to lower wavenumber in (I) presumably due to hydrogen-bonding inter­actions (Stocker et al., 1999). Additional absorption bands around 2966–2874 cm^-1 are ascribed to the vibration of the C—H groups of piperazine (Li et al., 2010). Sharp bands at 1586 and 1580 cm^-1 for complex (I) may be attributed to hydrogen-bonding inter­actions (Mondal et al., 2001; Samanta et al., 2007).

SEM examination indicates that crystals of the pristine compound (I) possess a bar shape and relatively clean surface. EDS analysis clearly exhibits signals arising from the heterometallic Cu^II and Co^III atoms that exist in (I). This gives rise to a Cu–Co molar ratio is 0.98:1.03 in compound (I), which is largely in agreement with the single-crystal diffraction data (Fig. 6). The XRPD of compound (I) was measured to check the bulk purity. The recorded and simulated XRPD patterns are quite similar, confirming the bulk purity of compound (I).

In order to examine the thermal stabilities of compound (I), thermogravimetric (TG) and differential thermal analyses (DTA) were carried out under an air atmosphere and under a pressure of 1 atm at a heating rate of 10 K min^-1. As shown in Fig. 7, the TG curve shows that compound (I) is stable up to 563 K. The DTA curve shows one exothermic peak (calculated 708 K). The first weight loss of 25.0% within the range 563–623 K corresponds to the removal of the protonated piperazine ligand and one water molecule (calculated 27.3%). This is followed by decomposition of the framework. Within the temperature range 623–873 K, the continuous removal of cyanide groups gives an unstable inter­mediate that is slowly oxidized in air upon further heating. The weight of the solid residue (found 43.30%; calculated 42.3%) is consistent with mixture of CuO (tenorite) and Co₂O₃ phases. The residue observed in the TG analysis of (I) is thus in agreement with previously reported compounds. For example, the cyanide-bridged heteronuclear complexes [Cu(dmpn1)₂]₃[Co(CN)₆]₂·12H₂O, [Cu(dmpn1)₂]₂[Co(CN)₆]·ClO₄·3H₂O (dmpn1 is 1-di­methyl­amino-2-propyl­amine; Mondal et al., 2001) and {[Cu^II(dmpn2)₂]₃[Co^III(CN)₆]₂·6H₂O}_n (dmpn2 = 2,2-di­methyl-1,3-di­amino­propane; Biswas et al., 2014), in which the final decomposition products were identified as CuO and Co₂O₃ phases. For other types of heterometallic compounds, e.g. [Ni(bpy)₃][Cu(CN)₃]·4.5H₂O and [Cu(bpy)₂(CN)]₂[Ni(CN)₄]·4H₂O (Kočanová et al., 2010), the solid residues are formed of a mixture of CuO and NiO.

The temperature dependence of the magnetic susceptibility of compound (I) in the temperature range 2–300 K under an applied field of 1000 Oe was measured on a Quantum Design SQUID MPMS XL-5 (Fig. 8). In compound (I), Co^III atoms with a d⁶ configuration are diamagnetic because the six d electrons are all paired under an o­cta­hedral crystal field of [Co(CN)₆]^3-. The χ_mT value at 300 K is 0.399 cm³ K mol^-1 for compound (I), which is slightly larger than that expected 0.375 cm³ K mol^-1 for an uncoupled Cu^II ion with g = 2.0. The χ_mT value decreases slowly with decreasing temperature until 25 K. After that, the χ_mT value rapidly decreases with lowering temperature down to a value of 0.11 cm³ K mol^-1 for compound (I) at 2.0 K. The fitting of Curie–Weiss law in the temperature range 50–300 K gives C = 0.408 cm³ K mol^-1 and θ = -8.60 K, and this gives rise to an average g value of 2.08 for (I). The negative θ values indicate that anti­ferromagnetic coupling dominates these systems. The field-dependent magnetization at 2 K increases slowly and linearly with the applied field, and no saturation is observed. The magnetization value at the highest field of 50 KOe is 0.77 Nβ for compound (I), close to the saturation value of 1.0 Nβ expected for one spin-only Cu^II species (Fig. 9). This observation suggests a weak anti­ferromagnetic inter­action between the Cu^II ions through the diamagnetic –NC—Co—CN– bridge. As far as we known, a number of examples of bimetallic systems containing diamagnetic [Co(CN)₆]^3- bridging ligands between paramagnetic ions with only e_g-type magnetic orbitals have been reported so far. For compounds PPh₄[Ni(pn)₂][Co(CN)₆]·H₂O (Ohba et al., 1998), [Ni(en)₂]₃[Co(CN)₆]₂·2H₂O (Ohba et al., 1997), [{Cu(dien)₂Co(CN)₆}_n][Cu(dien)(H₂O)Co(CN)₆]_n·5H₂O (Ferbinteanu et al., 1999), [(CuL)[Co(CN)₆](CuL)]ClO₄·3.5H₂O {L is (3E,5E)-N¹,N⁴-bis­[(pyridin-2-yl)methyl­ene]butane-1,4-di­amine; Samanta et al., 2007}, {[Cu^II(dmpn2)₂]₃[Co^III(CN)₆]₂·6H₂O}_n (Biswas et al., 2014) and [Cu(en)₂Li(H₂O)][Co(CN)₆] (en is ethyl­enedi­amine; Sima & Zhang, 2011), showing very weak anti­ferromagnetic coupling, as expected from the diamagnetic long chain –NC—Co—CN– bridges. In addition, we also note several copper(II) system compounds with diamagnetic [M(CN)₄]^2- (M = Ni, Pd or Pt) and diamagnetic [Ag(CN)₂]^- bridging ligands. For example, compounds [Cu(bpy)₂(CN)]₂[Ni(CN)₄]·4H₂O (Kočanová et al., 2010), [Cu(dpt)Pd(CN)₄]_n, {[Cu₂(medpt)₂Pd(CN)₄](ClO₄)₂·3H₂O}_n, {[Cu₂(dien)₂Pd(CN)₄](ClO₄)₂·2CH₃OH}_n, {[Cu₂(iPrdien)₂Pd(CN)₄](ClO₄)₂·2H₂O}_n (dpt is 3,3'-imino­bis­propyl­amine, medpt is 3,3'-di­amino-N-methyl­dipropyl­amine; dien is di­ethyl­enetri­amine and iprdien is N'-iso­propyldi­ethyl­enetri­amine; Manna et al., 2007), and [Cu(NH₃)₂Ag₂(CN)₄] (Vlček et al., 2007), which also present weak anti­ferromagnetic exchange inter­actions.

A new cyanide-bridged heterometallic Cu^II–Co^III coordination polymer [Cu^IICo^III(CN)₆(Hpip)(H₂O)], (I), has been synthesized by the reaction of CuCl₂·2H₂O with K₃[Co(CN)₆] and piperazine under solvothermal conditions. X-ray diffraction analysis reveals a two-dimensional layer structure constructed by [Cu(Hpip)(H₂O)]³⁺ cations and [Co(CN)₆]^3- anions, in which the [Cu(Hpip)(H₂O)]³⁺ cation is formed by protonated piperazine as charge-balance agent binding to the copper centre. These layers are further packed in an ABAB fashion through O—H···N and N—H···O hydrogen-bonding inter­actions to generate a 3D supra­molecular structure. In addition, magnetic investigations show that anti­ferromagnetic inter­actions exist in compound (I).

Synthesis and crystallization

A mixture of CuCl₂·2H₂O (0.068 g, 0.4 mmol), K₃[Co(CN)₆] (0.133 g, 0.4 mmol), piperazine (0.073 g, 0.9 mmol) in a molar ratio of 1.0:1.0:2.25 and CH₃CN (3 ml) and water (3 ml) was sealed in a 15 ml Teflon-lined stainless steel container (pH ≈ 7.5) and heated to 433 K for 6 d. After cooling to room temperature at a rate of 5 K h^-1, and filtration, red bar-shaped crystals were recovered in a yield of 40% (based on CuCl₂·2H₂O). Analysis calculated for C₁₀H₁₃CoCuN₈O: C 31.30, H 3.41, N 29.20%; found: C 31.23, H 3.56, N 29.18%. IR (KBr disk, cm^-1): ν(N—H) 3369 (w), 3342 (w); ν(O—H) 3304 (w), 3286 (w); ν(C—H) 2966 (w), 2923 (w), 2874 (w); ν(C≡N) 2174 (s), 2114 (s); δ(H—O—H) 1586 (m), 1580 (m).

Refinement details

Crystal data, data collection and structure refinement details are summarized in Table 1. H atoms bonded to C atoms or to N atoms of the piperazine ligand were placed in calculated positions and refined using a riding model, with C—H = 0.97 Å and N—H = 0.91 (NH) or 0.90 Å (NH₂). The isotropic displacement parameters of these H atoms were constrained to 1.2U_eq of their parent atoms. Water H atoms were located by difference Fourier synthesis. They were constrained to ride on their parent O atom with rotation about the Cu—O bond, with O—H = 0.88 Å and U_iso(H) = 1.5U_eq(O).

Computing details

Data collection: SMART (Bruker, 2002); cell refinement: SMART (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. The coordination geometry of the metal atoms of compound (I), with displacement ellipsoids drawn at the 50% probability level and with the H atoms shown as spheres of arbitrary radius. [Symmetry codes: (i) x, -y+3/2, -z+1; (ii) x+1, y, z; (iii) x+1, y, -z+1/2; (iv) x, y, -z+1/2.]
	Fig. 2. A view of the (4,4) grid-like layer in compound (I).
	Fig. 3. The 12-membered [Cu2Co2(CN)4] rings form two-dimensional layers with corrugated motifs.
	Fig. 4. A schematic representation of the three-dimensional supramolecular structure formed via hydrogen bonds interactions (broken lines) between the corrugated sheets of compound (I). [Symmetry codes: (i) -x, -y+2, -z+1; (ii) -x, -y+2, z-1/2; (iii) -x+1, y-1/2, -z+1/2.]
	Fig. 5. The stacking of layers along the b-axis direction in compound (I), with hydrogen-bonding interactions (dashed lines) bridging adjoining layers.
	Fig. 6. SEM image and EDS plot for compound (I).
	Fig. 7. TG–DTA curves of comound (I) under an air atmosphere and at a heating rate of 10 K min^-1.
	Fig. 8. Magnetic susceptibility data per formula unit presented as plots of χmT versus T and χm^-1 versus T under an applied 1000 Oe field for compound (I), the red solid line represents the best fit.
	Fig. 9. Field dependence of the magnetization per formula unit at 2 K for compound (I).

Poly[aquatetra-µ₂-cyanido-κ⁸C:N-dicyanido-κ²C-(piperazinium-κN⁴)cobalt(III)copper(II)]

Crystal data

[CuCo(C4H11N2)(CN)6(H2O)]	Dx = 1.731 Mg m^−3
Mr = 383.75	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbcm	Cell parameters from 2274 reflections
a = 7.2703 (4) Å	θ = 2.8–25.9°
b = 14.6512 (7) Å	µ = 2.58 mm^−1
c = 13.8246 (9) Å	T = 293 K
V = 1472.57 (14) Å^3	Bar, red
Z = 4	0.20 × 0.10 × 0.05 mm
F(000) = 772

Data collection

Bruker APEX CCD diffractometer	1571 independent reflections
Radiation source: fine-focus sealed tube	1455 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.018
φ and ω scans	θmax = 26.4°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Bruker, 2002)	h = −9→8
Tmin = 0.626, Tmax = 0.882	k = −18→15
3775 measured reflections	l = −15→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.032	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.108	H-atom parameters constrained
S = 1.10	w = 1/[σ^2(Fo^2) + (0.0542P)^2 + 4.0849P] where P = (Fo^2 + 2Fc^2)/3
1571 reflections	(Δ/σ)max = 0.001
103 parameters	Δρmax = 0.64 e Å^−3
0 restraints	Δρmin = −1.30 e Å^−3

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 F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Co1	−0.22426 (7)	0.7500	0.5000	0.00788 (19)
Cu1	0.27248 (7)	0.80801 (4)	0.2500	0.01455 (19)
N2	−0.5222 (4)	0.80273 (17)	0.35675 (19)	0.0176 (6)
O1W	0.3161 (4)	0.9523 (2)	0.2500	0.0160 (6)
H1WA	0.2887	0.9767	0.3067	0.024*	0.50
H1WB	0.2396	0.9804	0.2106	0.024*	0.50
N4	0.2225 (5)	0.6572 (3)	0.2500	0.0169 (8)
H4	0.0980	0.6510	0.2500	0.020*
N1	0.0662 (4)	0.81306 (18)	0.3569 (2)	0.0183 (6)
N5	0.2876 (6)	0.4602 (3)	0.2500	0.0242 (9)
H5A	0.4111	0.4560	0.2500	0.029*
H5B	0.2416	0.4031	0.2500	0.029*
N3	−0.2223 (5)	0.9356 (2)	0.5995 (3)	0.0330 (8)
C3	−0.2225 (4)	0.8662 (2)	0.5610 (2)	0.0159 (6)
C2	−0.4097 (4)	0.78631 (19)	0.4120 (2)	0.0125 (6)
C5	0.2262 (6)	0.5087 (3)	0.3394 (3)	0.0325 (9)
H5C	0.2787	0.4790	0.3958	0.039*
H5D	0.0933	0.5053	0.3446	0.039*
C1	−0.0422 (4)	0.79049 (19)	0.4122 (2)	0.0134 (6)
C4	0.2859 (5)	0.6081 (2)	0.3371 (3)	0.0244 (8)
H4A	0.2382	0.6388	0.3940	0.029*
H4B	0.4191	0.6109	0.3399	0.029*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co1	0.0066 (3)	0.0122 (3)	0.0049 (3)	0.000	0.000	0.0004 (2)
Cu1	0.0129 (3)	0.0182 (3)	0.0126 (3)	0.00008 (19)	0.000	0.000
N2	0.0147 (13)	0.0220 (13)	0.0162 (13)	−0.0002 (10)	−0.0048 (11)	0.0033 (11)
O1W	0.0226 (16)	0.0118 (13)	0.0135 (14)	0.0020 (12)	0.000	0.000
N4	0.0160 (19)	0.0146 (18)	0.020 (2)	0.0003 (14)	0.000	0.000
N1	0.0173 (13)	0.0216 (13)	0.0158 (13)	−0.0009 (10)	0.0062 (11)	0.0002 (11)
N5	0.023 (2)	0.0141 (18)	0.036 (2)	0.0028 (16)	0.000	0.000
N3	0.0397 (19)	0.0266 (17)	0.0329 (19)	−0.0042 (13)	0.0080 (15)	−0.0150 (15)
C3	0.0129 (14)	0.0214 (16)	0.0135 (15)	−0.0009 (11)	0.0024 (12)	0.0004 (13)
C2	0.0119 (14)	0.0137 (12)	0.0119 (13)	−0.0015 (11)	0.0037 (12)	0.0001 (11)
C5	0.039 (2)	0.0212 (17)	0.037 (2)	0.0059 (15)	0.0135 (18)	0.0073 (17)
C1	0.0131 (14)	0.0147 (13)	0.0125 (13)	0.0015 (11)	−0.0021 (12)	−0.0024 (12)
C4	0.035 (2)	0.0179 (16)	0.0205 (18)	0.0028 (14)	0.0003 (15)	0.0022 (14)

Geometric parameters (Å, º)

Co1—C1	1.892 (3)	O1W—H1WB	0.8799
Co1—C1^i	1.892 (3)	N4—C4	1.476 (4)
Co1—C2	1.893 (3)	N4—C4^iv	1.476 (4)
Co1—C2^i	1.893 (3)	N4—H4	0.9100
Co1—C3	1.900 (3)	N1—C1	1.146 (4)
Co1—C3^i	1.900 (3)	N5—C5^iv	1.494 (5)
Cu1—N2^ii	2.100 (3)	N5—C5	1.494 (5)
Cu1—N2^iii	2.100 (3)	N5—H5A	0.9000
Cu1—N1^iv	2.107 (3)	N5—H5B	0.9000
Cu1—N1	2.107 (3)	N3—C3	1.148 (5)
Cu1—O1W	2.138 (3)	C5—C4	1.521 (5)
Cu1—N4	2.239 (4)	C5—H5C	0.9700
N2—C2	1.144 (4)	C5—H5D	0.9700
N2—Cu1^v	2.100 (3)	C4—H4A	0.9700
O1W—H1WA	0.8837	C4—H4B	0.9700
C1—Co1—C1^i	91.17 (18)	Cu1—O1W—H1WA	111.5
C1—Co1—C2	89.87 (13)	Cu1—O1W—H1WB	111.6
C1^i—Co1—C2	178.01 (11)	H1WA—O1W—H1WB	102.6
C1—Co1—C2^i	178.01 (11)	C4—N4—C4^iv	109.3 (4)
C1^i—Co1—C2^i	89.87 (13)	C4—N4—Cu1	115.5 (2)
C2—Co1—C2^i	89.14 (17)	C4^iv—N4—Cu1	115.5 (2)
C1—Co1—C3	89.96 (13)	C4—N4—H4	105.1
C1^i—Co1—C3	89.50 (13)	C4^iv—N4—H4	105.1
C2—Co1—C3	92.20 (13)	Cu1—N4—H4	105.1
C2^i—Co1—C3	88.35 (13)	C1—N1—Cu1	161.2 (2)
C1—Co1—C3^i	89.50 (13)	C5^iv—N5—C5	111.7 (4)
C1^i—Co1—C3^i	89.96 (13)	C5^iv—N5—H5A	109.3
C2—Co1—C3^i	88.35 (13)	C5—N5—H5A	109.3
C2^i—Co1—C3^i	92.20 (13)	C5^iv—N5—H5B	109.3
C3—Co1—C3^i	179.22 (18)	C5—N5—H5B	109.3
N2^ii—Cu1—N2^iii	89.28 (15)	H5A—N5—H5B	107.9
N2^ii—Cu1—N1^iv	179.86 (12)	N3—C3—Co1	178.7 (3)
N2^iii—Cu1—N1^iv	90.81 (11)	N2—C2—Co1	175.7 (3)
N2^ii—Cu1—N1	90.81 (11)	N5—C5—C4	110.6 (3)
N2^iii—Cu1—N1	179.86 (12)	N5—C5—H5C	109.5
N1^iv—Cu1—N1	89.10 (16)	C4—C5—H5C	109.5
N2^ii—Cu1—O1W	86.05 (9)	N5—C5—H5D	109.5
N2^iii—Cu1—O1W	86.05 (9)	C4—C5—H5D	109.5
N1^iv—Cu1—O1W	94.06 (9)	H5C—C5—H5D	108.1
N1—Cu1—O1W	94.06 (9)	N1—C1—Co1	177.9 (3)
N2^ii—Cu1—N4	94.53 (10)	N4—C4—C5	113.3 (3)
N2^iii—Cu1—N4	94.53 (10)	N4—C4—H4A	108.9
N1^iv—Cu1—N4	85.36 (10)	C5—C4—H4A	108.9
N1—Cu1—N4	85.36 (10)	N4—C4—H4B	108.9
O1W—Cu1—N4	179.18 (13)	C5—C4—H4B	108.9
C2—N2—Cu1^v	169.8 (2)	H4A—C4—H4B	107.7
N2^ii—Cu1—N4—C4	19.8 (3)	C2^i—Co1—C3—N3	31 (14)
N2^iii—Cu1—N4—C4	109.4 (3)	C3^i—Co1—C3—N3	−105 (13)
N1^iv—Cu1—N4—C4	−160.1 (3)	Cu1^v—N2—C2—Co1	3 (5)
N1—Cu1—N4—C4	−70.7 (3)	C1—Co1—C2—N2	96 (4)
O1W—Cu1—N4—C4	−115.4 (2)	C1^i—Co1—C2—N2	−25 (6)
N2^ii—Cu1—N4—C4^iv	−109.4 (3)	C2^i—Co1—C2—N2	−85 (4)
N2^iii—Cu1—N4—C4^iv	−19.8 (3)	C3—Co1—C2—N2	−174 (4)
N1^iv—Cu1—N4—C4^iv	70.7 (3)	C3^i—Co1—C2—N2	7 (4)
N1—Cu1—N4—C4^iv	160.1 (3)	C5^iv—N5—C5—C4	−53.4 (5)
O1W—Cu1—N4—C4^iv	115.4 (2)	Cu1—N1—C1—Co1	−44 (8)
N2^ii—Cu1—N1—C1	−89.3 (8)	C1^i—Co1—C1—N1	117 (8)
N2^iii—Cu1—N1—C1	42 (65)	C2—Co1—C1—N1	−62 (8)
N1^iv—Cu1—N1—C1	90.6 (8)	C2^i—Co1—C1—N1	−122 (7)
O1W—Cu1—N1—C1	−175.4 (8)	C3—Co1—C1—N1	−154 (8)
N4—Cu1—N1—C1	5.2 (8)	C3^i—Co1—C1—N1	27 (8)
C1—Co1—C3—N3	−150 (14)	C4^iv—N4—C4—C5	−55.5 (5)
C1^i—Co1—C3—N3	−59 (14)	Cu1—N4—C4—C5	172.3 (2)
C2—Co1—C3—N3	120 (14)	N5—C5—C4—N4	55.3 (4)

Symmetry codes: (i) x, −y+3/2, −z+1; (ii) x+1, y, z; (iii) x+1, y, −z+1/2; (iv) x, y, −z+1/2; (v) x−1, y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1WA···N3^vi	0.88	1.89	2.737 (4)	160
O1W—H1WB···N3^vii	0.88	1.97	2.737 (4)	144
N5—H5A···O1W^viii	0.90	1.98	2.884 (5)	178

Symmetry codes: (vi) −x, −y+2, −z+1; (vii) −x, −y+2, z−1/2; (viii) −x+1, y−1/2, −z+1/2.