The first coordination compound of deprotonated 2-bromo­nicotinic acid: crystal structure of a dinuclear paddle-wheel copper(II) complex

Politeo, N.; Pisačić, M.; Đaković, M.; Sokol, V.; Kukovec, B.-M.

doi:10.1107/S2056989020000390

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ISSN: 2056-9890

Volume 76| Part 2| February 2020| Pages 225-230

https://doi.org/10.1107/S2056989020000390

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The first coordination compound of deprotonated 2-bromonicotinic acid: crystal structure of a dinuclear paddle-wheel copper(II) complex

Nives Politeo,^a Mateja Pisačić,^b Marijana Đaković,^b Vesna Sokol ^a ^* and Boris-Marko Kukovec ^a

^aDepartment of Physical Chemistry, Faculty of Chemistry and Technology, University of Split, Ruđera Boškovića 35, HR-21000 Split, Croatia, and ^bDepartment of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
^*Correspondence e-mail: vsokol@ktf-split.hr

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 19 December 2019; accepted 13 January 2020; online 17 January 2020)

A copper(II) dimer with the deprotonated anion of 2-bromonicotinic acid (2-BrnicH), namely, tetrakis(μ-2-bromonicotinato-κ²O: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-bromonicotinic acid in water. The copper(II) ion in 1 has a distorted square-pyramidal coordination environment, achieved by four carboxylate O atoms in the basal plane and the water molecule 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-bromonicotinate ligands in the syn-syn coordination mode. In the extended structure of 1, the cluster molecules 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 R²₂(8) and R²₂(16) loops and a tetrameric R⁴₄(16) loop. The Hirshfeld surface analysis was also performed in order to better illustrate the nature and abundance of the intermolecular contacts in the structure of 1.

Keywords: crystal structure; copper(II); 2-bromonicotinic acid; dinuclear paddle-wheel cluster; hydrogen-bond motif.

CCDC reference: 1977430

1. Chemical context

Copper(II) carboxylates have been studied extensively because of their structural diversity and related possible applications. The origin of this diversity is in the variable donating ability of the carboxylate oxygen atoms and in the nature of the other coordinated ligands (Iqbal et al., 2013 ; Song et al., 2009 ). The structural diversity of copper(II) carboxylates depends strongly on the inclusion of additional coligands (e.g. hydroxy, alkoxy and azide ions), which are able to mediate magnetic coupling between the copper(II) ions and to enable ferromagnetic and antiferromagnetic interactions via their various bridging modes (Zhang et al., 2012 ; Ma et al., 2014 ).

Copper(II) carboxylates can find applications as biologically active agents (Fountoulaki et al., 2011 ; Lim et al., 2009 ), as electrochemical (Bharathi et al., 2006 ; Bharathi et al., 2007 ), luminescent (Mei et al., 2016 ) and magnetic materials (Rigamonti et al., 2013 ; Cejudo et al., 2002 ; Colacio et al., 1999 ) and in the construction of MOFs. Copper(II) carboxylates can exhibit various magnetic properties – from the expected paramagnetic behavior (due to the d⁹ electronic configuration of the metal ion) to ferromagnetic and antiferromagnetic behavior, depending on the ligand coordination modes and copper(II) coordination environments (Rigamonti et al., 2013; Cejudo et al., 2002; Colacio et al., 1999). The metal–metal interaction in copper(II) carboxylates is also an important factor that can affect their magnetic properties and the structure (Rigamonti et al., 2013; Cejudo et al., 2002; Colacio et al.. 1999; Ozarowski et al., 2015 ; Poppl et al., 2008 ; Sarma et al., 2008 ).

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 (HKUST-1) 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 (almost 900) have been reported and deposited in the Cambridge Structural Database (CSD, Version 5.40, searched October 2019; Groom et al., 2016 ). However, metal complexes of nicotinic acid derivatives have been much less explored. For example, no metal complexes of 2-bromonicotinic acid (2-BrnicH) have been reported so far.

Our goal was to prepare 2-bromonicotinate copper(II) complexes for the above-mentioned significance of copper(II) carboxylates. The syntheses were carried out in aqueous solution to ensure that water molecules (either coordinated and/or hydrated) would be present in their crystal structures, enabling the formation of hydrogen-bonded frameworks. Furthermore, we wanted to explore the type and occurrence of hydrogen bond motifs within the obtained frameworks.

In this work, we report the synthesis and characterization of the first metal complex with 2-bromonicotinic acid – a dinuclear paddle-wheel copper(II) cluster, [Cu(H₂O)(2-Brnic)₂]₂ (1). Although similar dinuclear paddle-wheel copper(II) carboxylates with coordinated water molecules in the axial positions are well-established and have been extensively studied, there are only a few examples of such compounds that are analogous to 1, containing nicotinate 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 ).

2. Structural commentary

The asymmetric unit of 1 consists of a copper(II) ion coordinated by a water molecule and by two deprotonated O-monodentate 2-bromonicotinate ligands (Fig. 1). The coordination environment of the copper(II) ion can be described as a distorted square pyramid as τ amounts to 0 [τ = (α − β) / 60° (α and β are the largest angles), τ = 0 for an ideal square pyramid and 1 for an ideal trigonal bipyramid; Addison et al., 1984 ]. The basal plane of the pyramid is defined by four carboxylate O atoms [O2, O4, O3ⁱ and O5ⁱ; symmetry code: (i) −x + 1, −y + 2, −z + 1] from four 2-bromonicotinate ligands while its apical position is occupied by the aqua atom O1 (Fig. 2). The two symmetry-related copper(II) ions are connected into a centrosymmetric paddle-wheel dinuclear cluster [with a Cu⋯Cu contact length of 2.6470 (11) Å] via four O,O′-bridging 2-bromonicotinate ligands in the syn–syn coordination mode (Phetmung & Nucharoen, 2019 ). This Cu⋯Cu interaction is slightly longer than the sum of the covalent radii of Cu atoms (2.64 Å; Cordero et al., 2008 ). The Cu⋯Cu contact length in 1 is also somewhat longer than those in related paddle-wheel copper(II) clusters with nicotinic acid derivatives (Jun, Lu et al., 2013; Jun, Wei-Ping et al., 2013; Adhikari et al., 2016), but almost equal to that seen in the paddle-wheel copper(II) cluster with 2-chloronicotinic acid (Moncol et al., 2007). The Cu—O_c and Cu—O_w (c = carboxylate, w = water) bond lengths are comparable with literature values (Moncol et al., 2007; Jun, Lu et al., 2013; Jun, Wei-Ping et al., 2013; Adhikari et al., 2016).

Figure 1
The asymmetric unit of 1, with the atomic numbering scheme. The displacement ellipsoids are drawn at the 40% probability level.

Figure 2
The dinuclear cluster of 1 with selected atoms labeled [symmetry code: (i) −x + 1, −y + 2, −z + 1].

The copper(II) ion in 1 is situated nearly at the center of the basal plane with an out-of-plane deviation of 0.209 (2) Å in the direction of the apical Cu1—O1 bond (Fig. 2). The square-pyramidal coordination environment around the copper(II) ion is distorted, as indicated by the angles for the cis [88.95 (17)–103.05 (15)°] and trans [167.76 (17)–167.80 (15)°] pairs of ligating atoms. There is also a small tetragonal elongation because of the Jahn–Teller effect: Cu1—O1 [2.120 (4)] is somewhat longer than the other four Cu—O bond lengths [1.950 (4)–1.979 (4) Å].

3. Supramolecular features

The extended structure of 1 features strong O—H⋯O and O—H⋯N hydrogen bonds, weak C—H⋯O hydrogen bonds (Table 1) and anion–π interactions [C1—Br1⋯Cg1; where Cg1 is the centroid of the pyridine ring N1/C1–C5; Br1⋯Cg1 = 3.629 (2) Å; C1—Br1⋯Cg1 = 103.27 (17)°]. The strong hydrogen bonds link the cluster molecules into an infinite two-dimensional hydrogen-bonded network lying parallel to the (001) plane (Fig. 3), with the anion–π interactions consolidating the layered network. The layers are assembled into a three-dimensional network by the C—H⋯O bonds.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H11⋯O3ⁱ	0.82 (1)	2.07 (2)	2.868 (5)	165 (6)
O1—H12⋯N1ⁱⁱ	0.82 (1)	2.02 (2)	2.816 (6)	166 (6)
C11—H11A⋯O1ⁱⁱⁱ	0.93	2.51	3.403 (8)	161
Symmetry codes: (i) x+1, y, z; (ii) -x+1, -y+1, -z+1; (iii) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ .

Figure 3
A fragment of the infinite two-dimensional hydrogen-bonded network of 1 viewed along the c axis. The cluster molecules are connected by O—H⋯O and O—H⋯N hydrogen bonds (represented by the dotted lines) within the network.

There are some distinctive hydrogen-bonded ring motifs within the layered network of 1 (Fig. 4). The dimeric $[R_{2}^{2}]$ (8) motif is formed between symmetry-related molecules (indicated in brown and green) via two water molecules and two carboxylate O atoms, the dimeric $[R_{2}^{2}]$ (16) motif is formed between symmetry-related molecules (indicated in brown and blue) via two water molecules and two pyridine N atoms, while the tetrameric $[R_{4}^{4}]$ (16) motif is formed by symmetry-related molecules (indicated in blue, brown, red and green) via two water molecules and two pyridine N atoms (Fig. 4). The water molecules participate in the formation of motifs as both single- and double-proton donors [single in the $[R_{2}^{2}]$ (8) and $[R_{2}^{2}]$ (16) motifs and double in the $[R_{4}^{4}]$ (16) motif], while the carboxylate O and pyridine N atoms participate as single-proton acceptors exclusively. These hydrogen-bonded motifs in 1 are quite different from those in the crystal structures of related paddle-wheel copper(II) clusters with nicotinate derivatives (Jun, Lu et al., 2013; Jun, Wei-Ping et al., 2013; Adhikari et al., 2016). This difference is not surprising in the case of copper(II) clusters with 2-ethoxynicotinate and 2-(naphthalen-2-ylmethylsulfanyl)nicotinate because the presence of water molecules of crystallization drastically affects the crystal packing (Jun, Wei-Ping et al., 2013; Adhikari et al., 2016). The difference in the hydrogen-bonded ring motifs in the case of the copper(II) cluster with 2-methoxynicotinate (Jun, Lu et al., 2013) can be attributed to the different supramolecular arrangement of the cluster molecules, which are connected into a hydrogen-bonded chain, as opposed to a hydrogen-bonded network in the case of 1. Furthermore, it seems that the substituents in the nicotinate derivatives (methoxy group versus bromine atom) have a great influence on the supramolecular assemblies and on the hydrogen-bond motif types in the respective crystal packings because of the difference in the proton-acceptor abilities of the two substituents.

Figure 4
The distinctive hydrogen-bonded ring motifs (represented by dotted lines) found within the layered network of 1, viz. the dimeric $[R_{2}^{2}]$ (8) and $[R_{2}^{2}]$ (16) motifs and the tetrameric $[R_{4}^{4}]$ (16) motif. The various symmetry-related cluster molecules are shown in blue, brown, red and green (see text).

4. Hirshfeld surface analysis

The Hirshfeld surface analysis of 1 was performed using CrystalExplorer17.5 (Wolff et al., 2012 ). Normalized contact distances, d_norm, were plotted with standard color settings: regions highlighted in red represent shorter contacts, while longer contacts are shown in blue (Fig. 5). The fingerprint plots show distances from each point on the Hirshfeld surface to the nearest atom inside (d_i) and outside (d_e), and are presented for all contacts and for the contributions of two primary contacts, O—H⋯O and O—H⋯N hydrogen bonds (Fig. 6). The percentage contributions of all other selected contacts are presented as a pie chart (Fig. 6).

Figure 5
Hirshfeld surfaces on the molecule of 1. Regions highlighted in red represent shorter contacts, while longer contacts are blue.

Figure 6
The fingerprint plots showing distances from each point on the Hirshfeld surface to the nearest atom inside (d_i) and outside (d_e), presented for all contacts and for contributions of O—H⋯O and O—H⋯N hydrogen bonds in 1. The percentage contributions of all other selected contacts are shown in a pie chart.

5. PXRD and thermal analysis

The PXRD analysis was used to confirm the bulk content of 1 (see Fig. S1 in the supporting information). The experimental and calculated PXRD traces of 1 are in very good agreement, confirming the phase purity of 1.

The thermal stability of 1, as determined from the TG curve, is up to 140°C (Fig. S2 in the supporting information). The two coordinated water molecules (observed mass loss 3.9%, calculated 3.7%) were released at 176°C (endothermic peak at the DSC curve). The thermal decomposition of 1 continues via two consecutive steps (observed mass losses 10.6% and 24.7%) in the temperature range of 190–390°C (exothermic peak at 195°C), which corresponds to the release of approximately one and a half 2-bromonicotinate ligands (calculated mass loss 31.2%). The decomposition finishes with the release of another two 2-bromonicotinate ligands (observed mass loss 46.7%, calculated 41.6%) in the final step (temperature range of 390–600°C). The observed residue (13.3%) at 600°C, remained after total decomposition of 1, corresponds to CuO. The experimental mass fraction of copper (10.7%) matches nicely with the calculated mass fraction (13.1%).

6. Materials and methods

All chemicals for the synthesis were purchased from commercial sources (Merck) and used as received without further purification. The IR spectrum was obtained in the range 4000–400 cm⁻¹ on a Perkin–Elmer Spectrum Two^TM FTIR-spectrometer in the ATR mode. The PXRD trace was recorded on a Philips PW 1850 diffractometer, Cu Kα radiation, voltage 40 kV, current 40 mA, in the angle range 5–50° (2θ) with a step size of 0.02°. Simultaneous TGA/DSC measurements were performed at a heating rate of 10°C min⁻¹ in the temperature range 25–800°C, under an oxygen flow of 50 mL min⁻¹ on an Mettler–Toledo TGA/DSC 3+ instrument. Approximately 2 mg of the sample was placed in a standard alumina crucible (70 µl).

7. Synthesis and crystallization

2-Bromonicotinic acid (0.0502 g; 0.2485 mmol) was dissolved in distilled water (5 ml) with the addition of a drop of concentrated ammonia solution and then mixed and stirred with an aqueous copper(II) chloride dihydrate solution (0.0220 g; 0.1290 mmol in 2 ml of distilled water). The pH of the obtained solution was adjusted to 6–7 by adding an ammonia solution dropwise. The clear solution was left to evaporate slowly at room temperature for a month until blue crystals of 1, suitable for X-ray diffraction measurements, were obtained, which were collected by filtration, washed with ethanol and dried in vacuo. Yield: 0.0209 g (17%). Selected IR bands (ATR) (ν, cm⁻¹): 3432 [ν(O—H)], 3065 [ν(C—H)], 1623[ν(C=O)), 1385 [ν(C—N)_pyridine] (Fig. S3, Table S1 in the supporting information).

8. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The C-bound H atoms were placed geometrically (C—H = 0.93 Å) and refined as riding atoms. The water-molecule H atoms were found in difference-Fourier maps and refined with the O—H distances restrained to an average value of 0.82 Å using DFIX and DANG instructions. The constraint U_iso(H) = 1.2U_eq(carrier) was applied in all cases. The highest difference peak is 1.00 Å away from Br2 and the deepest difference hole is 0.78 Å away from the same atom.

Table 2
Experimental details

Crystal data
Chemical formula	[Cu(H₂O)(C₆H₃BrNO₂)₂]₂
M_r	967.13
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	7.5596 (2), 9.7402 (3), 20.5332 (7)
β (°)	94.345 (3)
V (Å³)	1507.56 (8)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	6.77
Crystal size (mm)	0.59 × 0.42 × 0.33

Data collection
Diffractometer	Oxford Diffraction Xcalibur2 diffractometer with Sapphire 3 CCD detector
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku, 2018 )
T_min, T_max	0.288, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	19205, 2622, 2392
R_int	0.028
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.050, 0.134, 1.06
No. of reflections	2622
No. of parameters	205
No. of restraints	3
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement

Δρ_max, Δρ_min (e Å⁻³)	1.34, −2.06
Computer programs: CrysAlis PRO (Rigaku, 2018), SHELXT (Sheldrick, 2015a ), SHELXL2018/3 (Sheldrick, 2015b ) and Mercury (Macrae et al., 2008 ).

Supporting information

CCDC reference: 1977430

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989020000390/hb7877sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989020000390/hb7877Isup2.hkl

PXRD, TG-DSC, IR data. DOI: https://doi.org/10.1107/S2056989020000390/hb7877sup3.docx

checkCIF report

Computing details top

Data collection: CrysAlis PRO (Rigaku, 2018); cell refinement: CrysAlis PRO (Rigaku, 2018); data reduction: CrysAlis PRO (Rigaku, 2018); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2008) and CrystalExplorer17.5 (Wolff et al., 2012); software used to prepare material for publication: SHELXL2018/3 (Sheldrick, 2015b).

Tetrakis(µ-2-bromonicotinato-κ²O:O')bis[aquacopper(II)](Cu—Cu) top

Crystal data top

[Cu₂(C₆H₃BrNO₂)₄(H₂O)₂]	F(000) = 932
M_r = 967.13	D_x = 2.131 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.5596 (2) Å	Cell parameters from 7938 reflections
b = 9.7402 (3) Å	θ = 4.6–32.5°
c = 20.5332 (7) Å	µ = 6.77 mm⁻¹
β = 94.345 (3)°	T = 296 K
V = 1507.56 (8) Å³	Prism, green–blue
Z = 2	0.59 × 0.42 × 0.33 mm

Data collection top

Oxford Diffraction Xcalibur2 diffractometer with Sapphire 3 CCD detector	2392 reflections with I > 2σ(I)
ω–scan	R_int = 0.028
Absorption correction: multi-scan (CrysAlisPro; Rigaku, 2018)	θ_max = 25.0°, θ_min = 4.3°
T_min = 0.288, T_max = 1.000	h = −8→8
19205 measured reflections	k = −11→11
2622 independent reflections	l = −24→24

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.050	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.134	w = 1/[σ²(F_o²) + (0.0666P)² + 10.4972P] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max = 0.001
2622 reflections	Δρ_max = 1.34 e Å⁻³
205 parameters	Δρ_min = −2.06 e Å⁻³
3 restraints

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cu1	0.65135 (8)	0.95254 (6)	0.48054 (3)	0.0136 (2)
Br1	0.35523 (10)	0.55987 (8)	0.58074 (4)	0.0462 (2)
Br2	0.97277 (15)	0.95629 (13)	0.67690 (5)	0.0838 (4)
N1	0.1831 (6)	0.4145 (5)	0.4818 (3)	0.0259 (10)
N2	0.8306 (9)	0.8063 (7)	0.7703 (3)	0.0518 (16)
O1	0.8705 (5)	0.8353 (4)	0.45349 (18)	0.0201 (8)
H11	0.969 (4)	0.857 (5)	0.469 (3)	0.024*
H12	0.852 (7)	0.758 (3)	0.466 (3)	0.024*
O2	0.4953 (5)	0.7928 (4)	0.4598 (2)	0.0251 (8)
O3	0.2397 (5)	0.8692 (4)	0.49343 (19)	0.0232 (8)
O4	0.6771 (5)	0.8938 (4)	0.57194 (17)	0.0265 (9)
O5	0.4213 (5)	0.9715 (4)	0.60518 (18)	0.0278 (9)
C1	0.2511 (7)	0.5362 (5)	0.4956 (3)	0.0214 (11)
C2	0.2524 (6)	0.6442 (5)	0.4517 (3)	0.0192 (11)
C3	0.1765 (8)	0.6213 (6)	0.3893 (3)	0.0318 (13)
H3	0.172615	0.691086	0.358327	0.038*
C4	0.1065 (9)	0.4933 (7)	0.3734 (3)	0.0361 (14)
H4	0.056199	0.474885	0.331615	0.043*
C5	0.1132 (8)	0.3943 (6)	0.4210 (3)	0.0314 (14)
H5	0.066424	0.308183	0.410259	0.038*
C6	0.3360 (7)	0.7797 (5)	0.4701 (2)	0.0186 (11)
C7	0.7871 (9)	0.8618 (7)	0.7123 (3)	0.0367 (15)
C8	0.6168 (8)	0.8574 (6)	0.6809 (3)	0.0258 (12)
C9	0.4876 (9)	0.7953 (8)	0.7142 (3)	0.0402 (16)
H9	0.370816	0.793989	0.696302	0.048*
C10	0.5309 (12)	0.7351 (9)	0.7740 (4)	0.054 (2)
H10	0.445567	0.689641	0.796168	0.065*
C11	0.7019 (13)	0.7440 (9)	0.7997 (3)	0.058 (2)
H11A	0.730394	0.704053	0.840298	0.069*
C12	0.5703 (7)	0.9133 (5)	0.6139 (2)	0.0211 (11)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.0134 (3)	0.0128 (3)	0.0144 (3)	0.0004 (2)	0.0001 (2)	0.0006 (2)
Br1	0.0477 (4)	0.0450 (4)	0.0450 (4)	−0.0018 (3)	−0.0018 (3)	0.0041 (3)
Br2	0.0700 (7)	0.1137 (9)	0.0637 (6)	−0.0456 (6)	−0.0206 (5)	0.0186 (6)
N1	0.019 (2)	0.014 (2)	0.045 (3)	0.0007 (18)	0.003 (2)	0.000 (2)
N2	0.066 (4)	0.057 (4)	0.029 (3)	0.007 (3)	−0.021 (3)	0.008 (3)
O1	0.0135 (17)	0.0172 (18)	0.030 (2)	0.0008 (14)	0.0027 (15)	−0.0025 (16)
O2	0.0172 (19)	0.0185 (19)	0.040 (2)	−0.0033 (14)	0.0033 (16)	−0.0058 (16)
O3	0.0155 (18)	0.0173 (18)	0.037 (2)	−0.0026 (14)	0.0034 (16)	−0.0043 (16)
O4	0.031 (2)	0.033 (2)	0.0157 (18)	0.0089 (17)	−0.0009 (16)	0.0044 (16)
O5	0.032 (2)	0.033 (2)	0.0184 (19)	0.0068 (18)	−0.0004 (16)	0.0049 (16)
C1	0.014 (2)	0.017 (3)	0.033 (3)	0.001 (2)	0.003 (2)	−0.001 (2)
C2	0.015 (2)	0.014 (2)	0.029 (3)	−0.0006 (19)	0.001 (2)	−0.001 (2)
C3	0.037 (3)	0.023 (3)	0.034 (3)	−0.005 (2)	−0.007 (3)	0.004 (2)
C4	0.036 (3)	0.032 (3)	0.038 (3)	−0.005 (3)	−0.011 (3)	−0.009 (3)
C5	0.024 (3)	0.017 (3)	0.051 (4)	−0.002 (2)	−0.005 (3)	−0.008 (3)
C6	0.018 (3)	0.016 (3)	0.021 (3)	−0.003 (2)	−0.003 (2)	0.003 (2)
C7	0.048 (4)	0.038 (3)	0.023 (3)	−0.004 (3)	−0.008 (3)	0.001 (3)
C8	0.037 (3)	0.025 (3)	0.015 (3)	0.005 (2)	−0.003 (2)	0.005 (2)
C9	0.045 (4)	0.048 (4)	0.027 (3)	0.003 (3)	0.005 (3)	0.012 (3)
C10	0.071 (5)	0.059 (5)	0.034 (4)	0.010 (4)	0.015 (4)	0.022 (3)
C11	0.089 (6)	0.060 (5)	0.024 (3)	0.007 (5)	0.002 (4)	0.023 (3)
C12	0.031 (3)	0.015 (2)	0.017 (3)	−0.001 (2)	−0.003 (2)	0.000 (2)

Geometric parameters (Å, º) top

Cu1—O5ⁱ	1.950 (4)	O5—C12	1.261 (7)
Cu1—O4	1.958 (4)	C1—C2	1.386 (8)
Cu1—O3ⁱ	1.978 (4)	C2—C3	1.381 (8)
Cu1—O2	1.979 (4)	C2—C6	1.499 (7)
Cu1—O1	2.120 (4)	C3—C4	1.384 (9)
Cu1—Cu1ⁱ	2.6470 (11)	C3—H3	0.9300
Br1—C1	1.875 (6)	C4—C5	1.371 (9)
Br2—C7	1.870 (7)	C4—H4	0.9300
N1—C1	1.314 (7)	C5—H5	0.9300
N1—C5	1.334 (8)	C7—C8	1.396 (9)
N2—C7	1.326 (8)	C8—C9	1.374 (9)
N2—C11	1.331 (11)	C8—C12	1.496 (7)
O1—H11	0.815 (10)	C9—C10	1.378 (9)
O1—H12	0.815 (10)	C9—H9	0.9300
O2—C6	1.245 (6)	C10—C11	1.362 (12)
O3—C6	1.254 (6)	C10—H10	0.9300
O4—C12	1.239 (7)	C11—H11A	0.9300

O5ⁱ—Cu1—O4	167.76 (17)	C2—C3—C4	119.2 (6)
O5ⁱ—Cu1—O3ⁱ	89.64 (17)	C2—C3—H3	120.4
O4—Cu1—O3ⁱ	89.35 (17)	C4—C3—H3	120.4
O5ⁱ—Cu1—O2	88.95 (17)	C5—C4—C3	118.3 (6)
O4—Cu1—O2	89.47 (17)	C5—C4—H4	120.9
O3ⁱ—Cu1—O2	167.80 (15)	C3—C4—H4	120.9
O5ⁱ—Cu1—O1	98.06 (16)	N1—C5—C4	123.6 (5)
O4—Cu1—O1	94.05 (15)	N1—C5—H5	118.2
O3ⁱ—Cu1—O1	103.05 (15)	C4—C5—H5	118.2
O2—Cu1—O1	89.15 (15)	O2—C6—O3	126.2 (5)
O5ⁱ—Cu1—Cu1ⁱ	87.08 (12)	O2—C6—C2	116.3 (5)
O4—Cu1—Cu1ⁱ	80.69 (12)	O3—C6—C2	117.5 (4)
O3ⁱ—Cu1—Cu1ⁱ	87.92 (11)	N2—C7—C8	124.0 (6)
O2—Cu1—Cu1ⁱ	79.91 (11)	N2—C7—Br2	114.0 (5)
O1—Cu1—Cu1ⁱ	167.85 (11)	C8—C7—Br2	121.9 (5)
C1—N1—C5	117.1 (5)	C9—C8—C7	116.7 (5)
C7—N2—C11	117.0 (7)	C9—C8—C12	119.4 (5)
Cu1—O1—H11	118 (4)	C7—C8—C12	123.9 (5)
Cu1—O1—H12	105 (4)	C8—C9—C10	120.1 (7)
H11—O1—H12	107 (4)	C8—C9—H9	120.0
C6—O2—Cu1	127.8 (3)	C10—C9—H9	120.0
C6—O3—Cu1ⁱ	118.1 (3)	C11—C10—C9	118.3 (7)
C12—O4—Cu1	126.8 (3)	C11—C10—H10	120.9
C12—O5—Cu1ⁱ	119.1 (3)	C9—C10—H10	120.9
N1—C1—C2	124.5 (5)	N2—C11—C10	123.9 (6)
N1—C1—Br1	116.2 (4)	N2—C11—H11A	118.1
C2—C1—Br1	119.3 (4)	C10—C11—H11A	118.1
C3—C2—C1	117.3 (5)	O4—C12—O5	126.3 (5)
C3—C2—C6	120.9 (5)	O4—C12—C8	117.6 (5)
C1—C2—C6	121.8 (5)	O5—C12—C8	116.0 (5)

C5—N1—C1—C2	1.0 (8)	C11—N2—C7—C8	−0.5 (11)
C5—N1—C1—Br1	−178.0 (4)	C11—N2—C7—Br2	176.5 (6)
N1—C1—C2—C3	0.0 (8)	N2—C7—C8—C9	2.4 (10)
Br1—C1—C2—C3	179.0 (4)	Br2—C7—C8—C9	−174.4 (5)
N1—C1—C2—C6	−178.5 (5)	N2—C7—C8—C12	−176.5 (6)
Br1—C1—C2—C6	0.5 (7)	Br2—C7—C8—C12	6.7 (9)
C1—C2—C3—C4	−1.0 (9)	C7—C8—C9—C10	−3.3 (10)
C6—C2—C3—C4	177.6 (6)	C12—C8—C9—C10	175.6 (6)
C2—C3—C4—C5	0.9 (10)	C8—C9—C10—C11	2.6 (12)
C1—N1—C5—C4	−1.1 (9)	C7—N2—C11—C10	−0.4 (13)
C3—C4—C5—N1	0.2 (10)	C9—C10—C11—N2	−0.7 (14)
Cu1—O2—C6—O3	3.4 (8)	Cu1—O4—C12—O5	2.3 (8)
Cu1—O2—C6—C2	−177.5 (3)	Cu1—O4—C12—C8	179.3 (4)
Cu1ⁱ—O3—C6—O2	−2.0 (7)	Cu1ⁱ—O5—C12—O4	−2.9 (8)
Cu1ⁱ—O3—C6—C2	178.9 (3)	Cu1ⁱ—O5—C12—C8	−179.9 (4)
C3—C2—C6—O2	−87.8 (6)	C9—C8—C12—O4	−138.3 (6)
C1—C2—C6—O2	90.7 (6)	C7—C8—C12—O4	40.6 (8)
C3—C2—C6—O3	91.3 (6)	C9—C8—C12—O5	39.0 (8)
C1—C2—C6—O3	−90.2 (6)	C7—C8—C12—O5	−142.2 (6)

Symmetry code: (i) −x+1, −y+2, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H11···O3ⁱⁱ	0.82 (1)	2.07 (2)	2.868 (5)	165 (6)
O1—H12···N1ⁱⁱⁱ	0.82 (1)	2.02 (2)	2.816 (6)	166 (6)
C11—H11A···O1^iv	0.93	2.51	3.403 (8)	161

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

Funding information

This research was supported by a Grant from the Foundation of the Croatian Academy of Sciences and Arts for 2019 and by the University of Split institutional funding.

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