Synthesis and crystal structure of catena-poly[[tetra-μ-acetato-copper(II)]-μ-6-eth­oxy-N2,N4-bis­[2-(pyridin-2-yl)eth­yl]-1,3,5-triazine-2,4-di­amine]

Ayodele, M.J.; Green, T.C.; Warsapperuma, W.A.C.V.; Forbes, M.D.E.; Ostrowski, A.D.

doi:10.1107/S2056989021002164

research communications

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ISSN: 2056-9890

Volume 77| Part 3| March 2021| Pages 319-323

https://doi.org/10.1107/S2056989021002164

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Synthesis and crystal structure of catena-poly[[tetra-μ-acetato-copper(II)]-μ-6-ethoxy-N²,N⁴-bis[2-(pyridin-2-yl)ethyl]-1,3,5-triazine-2,4-diamine]

Mayokun J. Ayodele,^a ^* Travis C. Green,^a W. A. Chathuri V. Warsapperuma,^a Malcolm D. E. Forbes ^a and Alexis D. Ostrowski ^a

^aDepartment of Chemistry, Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA
^*Correspondence e-mail: mayokua@bgsu.edu

Edited by A. M. Chippindale, University of Reading, England (Received 15 February 2021; accepted 23 February 2021; online 26 February 2021)

The title compound, [Cu₂(C₁₉H₂₃N₇O)(C₂H₃O₂)₄]_n, was obtained via reaction of copper(II) acetate with the coordinating ligand, 6-ethoxy-N²,N⁴-bis[2-(pyridin-2-yl)ethyl]-1,3,5-triazine-2,4-diamine. The crystallized product adopts the monoclinic P2₁/c space group. The metal core exhibits a paddle-wheel structure typical for dicopper tetraacetate units, with triazine and pyridyl nitrogen atoms from different ligands coordinating to the two axial positions of the paddle wheel in an asymmetric manner. This forms a coordination polymer with the segments of the polymer created by the c-glide of the P2₁/c setting of the space group. The resulting chains running along the c-axis direction are held together by intramolecular N—H⋯O hydrogen bonding. These chains are further packed by dispersion forces, producing an extended three-dimensional structure.

Keywords: crystal structure; intramolecular hydrogen bonding; dinuclear copper; triazine; acetate.

CCDC reference: 2064738

1. Chemical context

Dinuclear Cu^II groups are recognized for their crucial role as active sites in metalloenzymes and are present in many biological systems (Festa & Thiele, 2011 ; Solomon et al., 2014 ). They often constitute the catalytically active sites involved in the stepwise oxidative conversions of many small molecules (Pham & Waite, 2014 ; Chakraborty et al., 2014 ). A well-known series of metalloenyzmes containing dinuclear copper active sites is that of the polyphenol oxidases (e.g. catechol oxidase) where the catechol is easily oxidized to quinone products (Ravikiran & Mahalakshmi, 2014 ). In recent years, there has been an increased effort to carry over this efficient and selective oxidation into biomimetic models of metalloenzymes (Mahadevan et al., 2000 ; Panda et al., 2011 ; Marion et al., 2012 ).

As part of this quest, significant efforts have been made to identify and better understand the specific structural patterns found at these copper-containing active sites. These patterns have often been found to convey functionalities that define a particular enzyme. This has led to a focus on the basic elements of coordination between the ligands and the metal centers. For example, when designing mimics of catechol oxidase, many model catalysts include the same basic structural elements (Koval et al., 2006 ). These models often contain multidentate ligands with at least five coordinating heteroatoms branched off a central ring, all coordinating to the copper centers. This coordination motif and its orientation often provide a unique accessibility for substrate approach, similar to that found in a type-3 active site (Koval et al., 2006).

In this paper, we report the crystal structure of a biomimetic complex (I) of catechol oxidase synthesized from a multidentate ligand that is coordinated to the copper centers in an unexpected fashion. The complex possesses two nitrogen coordinating heteroatoms from triazine ligands, which coordinate to the copper centers of the paddle-wheel unit at the axial positions. Additional coordination by the terminal pendant pyridine group on the ligand to another copper paddle-wheel unit creates a continuous coordinated chain linkage.

2. Structural commentary

The title compound (I) crystallizes in the space group P2₁/c. The molecular structure of (I) (Fig. 1) includes a dinuclear Cu^II paddle-wheel unit with both metal ions in slightly Jahn–Teller-distorted octahedral environments. The two copper atoms are separated by a Cu1—Cu2 bond distance of 2.7888 (8) Å. As expected in a typical acetate paddle wheel, the acetate groups bridge the Cu atoms in a μ₂-O:O′ mode, with the Cu—O bonds lying in the range 1.927 (3)–2.046 (3) Å (Table 1). The longer Cu—O bonds found for Cu2—O5 [2.046 (3) Å] and Cu2—O9 [2.036 (3) Å] are a consequence of hydrogen-bonding interactions involving the O5 and O9 oxygen atoms (see text below for further details). Two triazine ligands coordinate to the copper-acetate paddle-wheel unit in an asymmetric manner, with one Cu atom coordinated to the triazyl nitrogen, N1, of the central ring on one ligand (green nitrogen in Scheme 1), and the other Cu coordinated to the terminal pyridyl nitrogen, N6, of a second ligand (pink nitrogen in Scheme 1). The two ligands adopt an almost orthogonal orientation to each other. Each of the ligands has their linking alkyl chain adopting a gauche geometry, making the two terminal pyridine rings twist away from the central triazine ring.

Table 1
Selected bond lengths (Å)

Cu1—O6	1.939 (3)	Cu2—O1	1.927 (3)
Cu1—O3	1.946 (3)	Cu2—O4	1.926 (3)
Cu1—O10	2.026 (3)	Cu2—O9	2.035 (3)
Cu1—O2	2.062 (3)	Cu2—O5	2.047 (3)
Cu1—N6i	2.147 (3)	Cu2—N1	2.180 (3)
Cu1—Cu2	2.7889 (8)
Symmetry codes: (i) x, −y + $[{1\over 2}]$ , z − $[{1\over 2}]$

Figure 1
Molecular structure of (I) drawn with 50% probability displacement ellipsoids. symmetry code (i) x, −y + $[{1\over 2}]$ , z − $[{1\over 2}]$ ; (ii) x, −y + $[{1\over 2}]$ , z + $[{1\over 2}]$ . Key: carbon, gray; nitrogen, blue; copper, light green; oxygen, red.

3. Supramolecular features

The copper centers and ligands are linked into a coordination polymer as a consequence of the presence of the c-glide in the P2₁/c space group. Intramolecular hydrogen-bonding interactions (Table 2) are observed for only one of the two triazine ligands coordinating to the paddle wheel, as shown in Fig. 2. These occur between the N4—H1⋯O5 and N5—H2⋯O9 atoms at (H⋯A) distances of 1.89 and 1.99 Å, respectively, with the hydrogens on the nitrogen atoms of the ortho branches off the triazine ring pointing towards the oxygen atoms of two of the acetate groups of the paddle wheel. Closely packed arrays of one-dimensional chains, hypothesized to be held together by dispersion forces, form an extended two-dimensional network in the bc plane (Fig. 3), which, with further packing, forms an extended three-dimensional structure. The 1D chains are separated from each other by 4.486 (1) Å, as shown in Fig. 4.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N4—H1⋯O5	0.88	1.89	2.767 (4)	171
N5—H2⋯O9	0.88	1.99	2.857 (4)	168

Figure 2
A packing diagram of (I)

viewed along the a axis showing the one-dimensional network. The N—H⋯·O hydrogen bonds are shown with the dashed light-blue lines. Key: carbon, gray; nitrogen, blue; copper, light green; oxygen, red.

Figure 3
The two-dimensional array of the coordinating networks of (I) viewed along the a axis.

Figure 4
Separated planes of the neighboring one-dimensional networks viewed slightly off the c axis. Key: carbon, gray; nitrogen, blue; copper, light green; oxygen, red.

4. Database survey

A structure survey was carried out on the Cambridge Structural Database (CSD version 5.41, update of August 2020; Groom et al., 2016 ). Search results show that although 1,3,5-triazine-2,4-diamine-derivative complexes with copper, ruthenium and rhodium have been reported (Singh et al., 2010 ; Chu et al., 2011 ; Massoud et al., 2011 ; Chakraborty et al., 2014), none of these complexes contains a copper(II) acetate [Cu₂(OAc)₄L₂] paddle wheel, as is found in compound (I). In all the previously reported structures, each ligand is coordinated to the metal using at least four of the nitrogen heteroatoms present. The structure of compound (I) presented here is rather different, as each ligand is coordinated to copper through only one nitrogen heteroatom. In addition, whilst some of the previously reported derivatives contain ortho-branched tertiary amines, compound (I) contains secondary amines.

5. Synthesis, crystallization and catalytic activity

The triazine ligand (Fig. 5, c) was synthesized by substituting all three chlorines on the cyanuric chloride ring (Fig. 5, a) (Razgoniaev et al., 2016 ). The first substitution was completed by chilling 40 mL (0.69 mol) of ethanol in an ice bath. Cyanuric chloride (5.00 g, 27 mmol) and sodium bicarbonate (2.35 g, 28 mmol) were added to the chilled ethanol and stirred in an ice bath for 45 minutes. The reaction mixture was then taken out of the ice bath, stirred at room temperature for 3.5 h and then poured over 20 mL of ice. The resulting precipitate was collected by vacuum filtration. The second and third substitutions were completed by taking the product from step 1 (2.30 g, 12 mmol) (Fig. 5, b) and dissolving it in CHCl₃. The solution was chilled in an ice bath. 2-(2-Aminoethyl)pyridine (3.60 g, 29 mmol) and N,N-diisopropylethylamine (DIPEA) (3.80 g, 29 mmol) were dissolved in CHCl₃ and added dropwise to the chilled solution. The reaction was stirred at room temperature for 1 h and stirred at reflux for 12 h. The final product was purified by removing the solvent and taking up the residue in chilled DMF. The product was collected by vacuum filtration and washed at least three times with 15 mL of chilled DMF. The product was obtained as a white powder [yield: 1.75g, 4.8 mmol (40% yield)] and was characterized using ¹H NMR.

Figure 5
Synthesis of 6-ethoxy-N²,N⁴-bis(2-(pyridin-2-yl)ethyl)-1,3,5-triazine-2,4-diamine.

¹H NMR (CDCl₃, 500 MHz): δ ppm, 8.6 (d, 2H, Ar—H, a); 7.7 (m, 2H, Ar—H, b); 7.2 (m, 4H, Ar—H, c); 6.6 (m, 2H, NH, d); 4.5 (m, 2H, O—CH₂, g); 4.4 (m, 4H, N—-CH₂–, e); 3.1 (m, 4H, –N—CH₂, f); 1.4 (d, 3H, –CH₃, h)

Crystal formation of [Cu₂(C₁₉H₂₃N₇O)₂(C₂H₃O₂)₄]_n (I). The triazine ligand (339.4 mg, 1.0 mmol) was dissolved in chloroform (20 mL) and a stoichiometric amount of copper(II) acetate (367.3 mg, 1.0 mmol) was dissolved in methanol (20 mL). The two solutions were mixed, and the resulting solution was placed in an ether diffusion chamber for at least four days. Green crystals of (I) were filtered off and washed with methanol. The melting point of the crystals was 639–643 K.

Catalytic activity of [Cu₂(C₁₉H₂₃N₇O)₂(C₂H₃O₂)₄]_n (I)

The catechol, 1,4-dihydroxybenzene, was used to test the catalytic activity of compound (I). This catechol is cheap and has good solubility in water. 2 mL of 10⁻⁴ M of compound (I) in a chloroform: methanol (1:1) solution was placed in a cuvette and 10 µL of a 1 M solution of the catechol injected. The conversion of the catechol into its quinone derivative (benzoquinone) was monitored by measuring the absorbance at 403 nm over a period of time. Fig. 6 shows a continuous increment in absorption at this wavelength, indicating the formation of the product.

Figure 6
Plot of change in absorbance intensity at 403 nm vs time indicating the catalytic oxidation of catechol by (I).

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. All hydrogen atoms attached to methyl carbons were placed in geometrically calculated positions (C—H = 0.98 Å) and refined using a riding model with displacement parameters [U_iso(H) = 1.5U_eq(C)]. All other carbon–bound hydrogens were placed in geometrically calculated positions (C—H = 0.95–0.99 Å) and were refined as part of a riding model with U_iso(H) = 1.2U_eq(C). Nitrogen-bound hydrogens were located in a difference-Fourier map and refined using a riding model with fixed displacement parameters [U_iso (H) = 1.2U_eq(N)], with the N—H bond distance equal to 0.88 Å.

Table 3
Experimental details

Crystal data
Chemical formula	[Cu₂(C₁₉H₂₃N₇O)(C₂H₃O₂)₄]
M_r	728.70
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	8.1495 (8), 21.964 (2), 17.5750 (17)
β (°)	101.457 (4)
V (Å³)	3083.2 (5)
Z	4
Radiation type	Cu Kα
μ (mm⁻¹)	2.25
Crystal size (mm)	0.09 × 0.08 × 0.07

Data collection
Diffractometer	Bruker AXS D8 Quest CMOS diffractometer
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.621, 0.754
No. of measured, independent and observed [I > 2σ(I)] reflections	32494, 5992, 5118
R_int	0.064
(sin θ/λ)_max (Å⁻¹)	0.618

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.059, 0.128, 1.12
No. of reflections	5992
No. of parameters	411
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.47, −0.58
Computer programs: APEX2 (Bruker, 2014 ), SAINT (Bruker, 2013 ), SHELXS97 (Sheldrick, 2008 ), SHELXL2014/7 (Sheldrick, 2015 ) shelXle (Hübschle et al., 2011 ), Mercury (Macrae et al., 2020 ), SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 2064738

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989021002164/cq2041sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989021002164/cq2041Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989021002164/cq2041Isup3.cdx

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015) shelXle (Hübschle et al., 2011); molecular graphics: Mercury (Macrae et al., 2020); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010).

catena-Poly[[tetra-µ-acetato-copper(II)]-µ-6-ethoxy-N²,N⁴-bis[2-(pyridin-2-yl)ethyl]-1,3,5-triazine-2,4-diamine] top

Crystal data top

[Cu₂(C₁₉H₂₃N₇O)(C₂H₃O₂)₄]	F(000) = 1504
M_r = 728.70	D_x = 1.570 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54178 Å
a = 8.1495 (8) Å	Cell parameters from 9834 reflections
b = 21.964 (2) Å	θ = 3.3–72.4°
c = 17.5750 (17) Å	µ = 2.25 mm⁻¹
β = 101.457 (4)°	T = 100 K
V = 3083.2 (5) Å³	Block, green
Z = 4	0.09 × 0.08 × 0.07 mm

Data collection top

Bruker AXS D8 Quest CMOS diffractometer	5118 reflections with I > 2σ(I)
Radiation source: I-mu-S microsource X-ray tube	R_int = 0.064
ω and phi scans	θ_max = 72.4°, θ_min = 3.3°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −9→10
T_min = 0.621, T_max = 0.754	k = −27→27
32494 measured reflections	l = −21→21
5992 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.059	H-atom parameters constrained
wR(F²) = 0.128	w = 1/[σ²(F_o²) + 14.2144P] where P = (F_o² + 2F_c²)/3
S = 1.12	(Δ/σ)_max < 0.001
5992 reflections	Δρ_max = 0.47 e Å⁻³
411 parameters	Δρ_min = −0.58 e Å⁻³

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	0.21566 (7)	0.28042 (3)	0.63661 (3)	0.01910 (15)
N1	0.4958 (4)	0.41259 (15)	0.85305 (17)	0.0176 (6)
C1	0.5128 (4)	0.39364 (18)	0.9280 (2)	0.0182 (7)
O1	0.1575 (3)	0.39851 (14)	0.75122 (17)	0.0280 (6)
Cu2	0.36793 (7)	0.35695 (3)	0.75666 (3)	0.01962 (15)
N2	0.6024 (4)	0.42400 (16)	0.98968 (18)	0.0221 (7)
C2	0.5743 (5)	0.46537 (17)	0.8439 (2)	0.0187 (7)
O3	0.2721 (4)	0.33954 (14)	0.56345 (16)	0.0275 (6)
N3	0.6693 (4)	0.49737 (16)	0.90069 (19)	0.0238 (7)
C3	0.6778 (5)	0.47284 (18)	0.9713 (2)	0.0222 (8)
O4	0.5758 (3)	0.31407 (14)	0.76057 (17)	0.0285 (7)
N4	0.4395 (4)	0.34253 (15)	0.94256 (18)	0.0214 (7)
H1	0.3869	0.3209	0.9030	0.026*
C4	0.7996 (6)	0.4807 (2)	1.1067 (2)	0.0296 (9)
H4A	0.6922	0.4644	1.1162	0.036*
H4B	0.8360	0.5137	1.1445	0.036*
O5	0.2767 (4)	0.28468 (14)	0.80890 (16)	0.0282 (6)
N5	0.5563 (4)	0.48814 (15)	0.76969 (18)	0.0199 (7)
H2	0.5024	0.4661	0.7309	0.024*
C5	0.9278 (6)	0.4313 (2)	1.1184 (3)	0.0359 (11)
H5A	0.8852	0.3962	1.0859	0.054*
H5B	0.9517	0.4190	1.1731	0.054*
H5C	1.0307	0.4462	1.1039	0.054*
O6	0.1639 (3)	0.22284 (13)	0.71209 (15)	0.0236 (6)
N6	0.0755 (4)	0.27169 (15)	1.04225 (17)	0.0192 (7)
C6	0.6206 (5)	0.5454 (2)	0.7528 (3)	0.0292 (9)
H6A	0.6606	0.5424	0.7033	0.035*
H6B	0.7179	0.5558	0.7942	0.035*
C7	0.4917 (6)	0.5963 (2)	0.7464 (3)	0.0347 (10)
H7A	0.4418	0.5961	0.7933	0.042*
H7B	0.5484	0.6359	0.7443	0.042*
N7	0.3853 (6)	0.6155 (2)	0.6104 (2)	0.0441 (10)
C8	0.3538 (6)	0.5897 (2)	0.6751 (3)	0.0352 (10)
O9	0.3976 (4)	0.40096 (14)	0.65835 (16)	0.0295 (7)
C9	0.2070 (7)	0.5581 (3)	0.6758 (3)	0.0451 (12)
H9	0.1891	0.5392	0.7220	0.054*
O10	0.4582 (3)	0.25350 (14)	0.66345 (16)	0.0269 (6)
C10	0.0865 (7)	0.5545 (3)	0.6082 (4)	0.0547 (15)
H10	−0.0154	0.5334	0.6077	0.066*
C11	0.1158 (7)	0.5817 (3)	0.5421 (3)	0.0512 (14)
H11	0.0348	0.5806	0.4951	0.061*
C19	−0.0735 (5)	0.2493 (2)	1.0075 (2)	0.0266 (9)
H19	−0.1127	0.2134	1.0283	0.032*
C18	−0.1729 (5)	0.2754 (2)	0.9435 (2)	0.0298 (9)
H18	−0.2779	0.2580	0.9207	0.036*
C17	−0.1163 (5)	0.3274 (2)	0.9132 (2)	0.0289 (9)
H17	−0.1805	0.3459	0.8680	0.035*
C16	0.0351 (5)	0.3525 (2)	0.9492 (2)	0.0268 (9)
H16	0.0747	0.3889	0.9300	0.032*
C15	0.1289 (5)	0.32336 (17)	1.0141 (2)	0.0189 (8)
C14	0.2967 (5)	0.34749 (18)	1.0542 (2)	0.0219 (8)
H14A	0.3140	0.3380	1.1103	0.026*
H14B	0.2977	0.3923	1.0485	0.026*
C13	0.4415 (5)	0.32016 (19)	1.0209 (2)	0.0229 (8)
H13A	0.5495	0.3310	1.0550	0.027*
H13B	0.4319	0.2752	1.0199	0.027*
C12	0.2675 (8)	0.6108 (3)	0.5462 (3)	0.0560 (16)
H12	0.2893	0.6288	0.5000	0.067*
C20	0.5797 (5)	0.27124 (19)	0.7137 (2)	0.0214 (8)
C21	0.7455 (5)	0.2386 (2)	0.7185 (3)	0.0311 (10)
H21A	0.7259	0.1988	0.6933	0.047*
H21B	0.7992	0.2331	0.7731	0.047*
H21C	0.8185	0.2630	0.6923	0.047*
O23	0.7747 (4)	0.50524 (13)	1.02788 (16)	0.0286 (7)
C23	0.1705 (6)	0.1901 (2)	0.8418 (3)	0.0322 (10)
H23A	0.0889	0.1602	0.8159	0.048*
H23B	0.1251	0.2110	0.8823	0.048*
H23C	0.2746	0.1692	0.8653	0.048*
C22	0.2058 (5)	0.23605 (18)	0.7830 (2)	0.0217 (8)
C26	0.3480 (5)	0.38767 (19)	0.5880 (2)	0.0227 (8)
C25	−0.1298 (5)	0.4153 (2)	0.7018 (3)	0.0346 (10)
H25A	−0.1744	0.4304	0.6493	0.052*
H25B	−0.1082	0.4497	0.7379	0.052*
H25C	−0.2114	0.3878	0.7178	0.052*
C24	0.0304 (5)	0.38149 (19)	0.7023 (2)	0.0236 (8)
C27	0.3794 (6)	0.4337 (2)	0.5296 (3)	0.0368 (11)
H27A	0.3726	0.4138	0.4791	0.055*
H27B	0.4911	0.4513	0.5466	0.055*
H27C	0.2950	0.4660	0.5249	0.055*
O2	0.0277 (3)	0.33809 (13)	0.65513 (16)	0.0266 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.0161 (3)	0.0253 (3)	0.0143 (3)	−0.0009 (2)	−0.0007 (2)	−0.0005 (2)
N1	0.0139 (15)	0.0243 (16)	0.0138 (15)	−0.0021 (12)	0.0008 (12)	−0.0017 (12)
C1	0.0110 (17)	0.0250 (19)	0.0163 (17)	−0.0009 (14)	−0.0030 (14)	−0.0010 (15)
O1	0.0175 (14)	0.0345 (16)	0.0296 (15)	0.0046 (12)	−0.0009 (12)	−0.0067 (13)
Cu2	0.0149 (3)	0.0259 (3)	0.0164 (3)	0.0012 (2)	−0.0010 (2)	−0.0024 (2)
N2	0.0208 (17)	0.0287 (18)	0.0148 (15)	−0.0047 (14)	−0.0014 (13)	−0.0028 (13)
C2	0.0170 (18)	0.0208 (19)	0.0171 (18)	0.0004 (15)	0.0007 (14)	−0.0018 (14)
O3	0.0283 (15)	0.0351 (16)	0.0170 (13)	−0.0067 (13)	−0.0004 (11)	0.0017 (12)
N3	0.0239 (17)	0.0250 (17)	0.0206 (16)	−0.0049 (14)	−0.0004 (14)	−0.0031 (13)
C3	0.0186 (19)	0.026 (2)	0.0202 (19)	−0.0064 (16)	0.0002 (15)	−0.0073 (16)
O4	0.0178 (14)	0.0355 (17)	0.0275 (15)	0.0056 (12)	−0.0067 (12)	−0.0104 (13)
N4	0.0218 (17)	0.0290 (18)	0.0120 (15)	−0.0071 (14)	−0.0002 (12)	0.0005 (13)
C4	0.030 (2)	0.034 (2)	0.021 (2)	−0.0058 (18)	−0.0044 (17)	−0.0054 (17)
O5	0.0323 (16)	0.0338 (16)	0.0166 (13)	−0.0089 (13)	0.0003 (12)	−0.0003 (12)
N5	0.0167 (16)	0.0249 (17)	0.0165 (15)	−0.0057 (13)	−0.0009 (12)	−0.0026 (13)
C5	0.024 (2)	0.053 (3)	0.028 (2)	0.004 (2)	−0.0022 (18)	0.000 (2)
O6	0.0234 (14)	0.0269 (15)	0.0195 (14)	−0.0029 (12)	0.0020 (11)	−0.0010 (11)
N6	0.0144 (15)	0.0258 (17)	0.0152 (15)	0.0028 (13)	−0.0022 (12)	−0.0001 (13)
C6	0.028 (2)	0.032 (2)	0.025 (2)	−0.0065 (18)	−0.0003 (17)	0.0027 (18)
C7	0.039 (3)	0.032 (2)	0.033 (2)	−0.003 (2)	0.007 (2)	0.0005 (19)
N7	0.049 (3)	0.044 (2)	0.036 (2)	0.014 (2)	0.003 (2)	0.0086 (19)
C8	0.041 (3)	0.031 (2)	0.033 (2)	0.008 (2)	0.007 (2)	0.0016 (19)
O9	0.0346 (17)	0.0309 (16)	0.0219 (15)	−0.0077 (13)	0.0028 (12)	0.0004 (12)
C9	0.044 (3)	0.051 (3)	0.040 (3)	0.000 (2)	0.006 (2)	0.000 (2)
O10	0.0175 (14)	0.0353 (16)	0.0261 (15)	0.0030 (12)	−0.0002 (11)	−0.0075 (12)
C10	0.037 (3)	0.068 (4)	0.057 (4)	0.002 (3)	0.002 (3)	−0.003 (3)
C11	0.040 (3)	0.061 (4)	0.044 (3)	0.016 (3)	−0.012 (2)	0.002 (3)
C19	0.021 (2)	0.034 (2)	0.025 (2)	−0.0007 (17)	0.0031 (16)	0.0018 (17)
C18	0.0158 (19)	0.041 (3)	0.029 (2)	0.0032 (18)	−0.0046 (16)	0.0009 (19)
C17	0.026 (2)	0.036 (2)	0.021 (2)	0.0077 (18)	−0.0056 (17)	0.0028 (17)
C16	0.026 (2)	0.029 (2)	0.024 (2)	0.0035 (17)	0.0000 (17)	0.0035 (17)
C15	0.0206 (19)	0.0204 (18)	0.0150 (17)	0.0046 (15)	0.0017 (14)	0.0003 (14)
C14	0.027 (2)	0.0220 (19)	0.0143 (17)	−0.0018 (16)	−0.0007 (15)	0.0003 (14)
C13	0.021 (2)	0.029 (2)	0.0162 (18)	0.0005 (16)	−0.0021 (15)	0.0053 (15)
C12	0.063 (4)	0.065 (4)	0.036 (3)	0.025 (3)	0.000 (3)	0.015 (3)
C20	0.0137 (18)	0.029 (2)	0.0205 (19)	−0.0004 (16)	0.0012 (15)	0.0004 (16)
C21	0.017 (2)	0.037 (2)	0.039 (2)	0.0025 (18)	0.0039 (18)	−0.008 (2)
O23	0.0324 (16)	0.0295 (15)	0.0208 (14)	−0.0093 (13)	−0.0021 (12)	−0.0029 (12)
C23	0.038 (3)	0.034 (2)	0.025 (2)	−0.003 (2)	0.0090 (19)	0.0050 (18)
C22	0.0155 (18)	0.028 (2)	0.0220 (19)	−0.0007 (15)	0.0037 (15)	0.0027 (16)
C26	0.0173 (19)	0.030 (2)	0.0201 (19)	−0.0008 (16)	0.0017 (15)	0.0037 (16)
C25	0.018 (2)	0.038 (3)	0.046 (3)	0.0055 (18)	0.0033 (19)	−0.007 (2)
C24	0.0156 (19)	0.029 (2)	0.026 (2)	0.0016 (16)	0.0032 (16)	0.0020 (17)
C27	0.043 (3)	0.039 (3)	0.028 (2)	−0.003 (2)	0.008 (2)	0.007 (2)
O2	0.0192 (14)	0.0328 (16)	0.0254 (15)	0.0036 (12)	−0.0016 (11)	−0.0059 (12)

Geometric parameters (Å, º) top

Cu1—O6	1.939 (3)	C7—H7B	0.9900
Cu1—O3	1.946 (3)	N7—C12	1.332 (7)
Cu1—O10	2.027 (3)	N7—C8	1.342 (6)
Cu1—O2	2.063 (3)	C8—C9	1.384 (8)
Cu1—N6ⁱ	2.148 (3)	O9—C26	1.256 (5)
Cu1—Cu2	2.7887 (8)	C9—C10	1.385 (8)
N1—C2	1.349 (5)	C9—H9	0.9500
N1—C1	1.362 (5)	O10—C20	1.250 (5)
C1—N4	1.320 (5)	C10—C11	1.369 (9)
C1—N2	1.356 (5)	C10—H10	0.9500
O1—C24	1.264 (5)	C11—C12	1.380 (9)
Cu2—O1	1.928 (3)	C11—H11	0.9500
Cu2—O4	1.927 (3)	C19—C18	1.374 (6)
Cu2—O9	2.036 (3)	C19—H19	0.9500
Cu2—O5	2.046 (3)	C18—C17	1.379 (6)
Cu2—N1	2.179 (3)	C18—H18	0.9500
N2—C3	1.308 (5)	C17—C16	1.384 (6)
C2—N3	1.336 (5)	C17—H17	0.9500
C2—N5	1.377 (5)	C16—C15	1.397 (5)
O3—C26	1.257 (5)	C16—H16	0.9500
N3—C3	1.343 (5)	C15—C14	1.505 (5)
C3—O23	1.344 (5)	C14—C13	1.539 (6)
O4—C20	1.255 (5)	C14—H14A	0.9900
N4—C13	1.459 (5)	C14—H14B	0.9900
N4—H1	0.8800	C13—H13A	0.9900
C4—O23	1.463 (5)	C13—H13B	0.9900
C4—C5	1.492 (6)	C12—H12	0.9500
C4—H4A	0.9900	C20—C21	1.516 (5)
C4—H4B	0.9900	C21—H21A	0.9800
O5—C22	1.256 (5)	C21—H21B	0.9800
N5—C6	1.416 (5)	C21—H21C	0.9800
N5—H2	0.8800	C23—C22	1.513 (6)
C5—H5A	0.9800	C23—H23A	0.9800
C5—H5B	0.9800	C23—H23B	0.9800
C5—H5C	0.9800	C23—H23C	0.9800
O6—C22	1.259 (5)	C26—C27	1.499 (6)
N6—C19	1.340 (5)	C25—C24	1.500 (6)
N6—C15	1.344 (5)	C25—H25A	0.9800
N6—Cu1ⁱⁱ	2.148 (3)	C25—H25B	0.9800
C6—C7	1.522 (6)	C25—H25C	0.9800
C6—H6A	0.9900	C24—O2	1.261 (5)
C6—H6B	0.9900	C27—H27A	0.9800
C7—C8	1.515 (7)	C27—H27B	0.9800
C7—H7A	0.9900	C27—H27C	0.9800

O6—Cu1—O3	178.22 (12)	N7—C8—C9	122.0 (5)
O6—Cu1—O10	89.15 (12)	N7—C8—C7	115.2 (5)
O3—Cu1—O10	90.05 (13)	C9—C8—C7	122.8 (4)
O6—Cu1—O2	91.34 (12)	C26—O9—Cu2	130.9 (3)
O3—Cu1—O2	88.55 (13)	C8—C9—C10	119.2 (5)
O10—Cu1—O2	149.63 (11)	C8—C9—H9	120.4
O6—Cu1—N6ⁱ	91.50 (12)	C10—C9—H9	120.4
O3—Cu1—N6ⁱ	90.27 (12)	C20—O10—Cu1	132.2 (3)
O10—Cu1—N6ⁱ	111.64 (12)	C11—C10—C9	119.3 (6)
O2—Cu1—N6ⁱ	98.70 (12)	C11—C10—H10	120.3
O6—Cu1—Cu2	90.00 (8)	C9—C10—H10	120.3
O3—Cu1—Cu2	88.25 (9)	C10—C11—C12	117.6 (5)
O10—Cu1—Cu2	74.51 (8)	C10—C11—H11	121.2
O2—Cu1—Cu2	75.12 (8)	C12—C11—H11	121.2
N6ⁱ—Cu1—Cu2	173.68 (9)	N6—C19—C18	123.6 (4)
C2—N1—C1	114.8 (3)	N6—C19—H19	118.2
C2—N1—Cu2	123.6 (2)	C18—C19—H19	118.2
C1—N1—Cu2	121.4 (2)	C19—C18—C17	118.3 (4)
N4—C1—N2	117.1 (3)	C19—C18—H18	120.9
N4—C1—N1	119.0 (3)	C17—C18—H18	120.9
N2—C1—N1	123.9 (3)	C18—C17—C16	119.3 (4)
C24—O1—Cu2	119.6 (3)	C18—C17—H17	120.3
O4—Cu2—O1	178.75 (13)	C16—C17—H17	120.3
O4—Cu2—O9	90.60 (13)	C17—C16—C15	119.0 (4)
O1—Cu2—O9	89.29 (13)	C17—C16—H16	120.5
O4—Cu2—O5	90.00 (13)	C15—C16—H16	120.5
O1—Cu2—O5	89.47 (13)	N6—C15—C16	121.5 (4)
O9—Cu2—O5	149.80 (12)	N6—C15—C14	117.1 (3)
O4—Cu2—N1	88.00 (12)	C16—C15—C14	121.3 (4)
O1—Cu2—N1	93.23 (12)	C15—C14—C13	112.3 (3)
O9—Cu2—N1	105.92 (12)	C15—C14—H14A	109.1
O5—Cu2—N1	104.28 (11)	C13—C14—H14A	109.1
O4—Cu2—Cu1	89.33 (9)	C15—C14—H14B	109.1
O1—Cu2—Cu1	89.44 (9)	C13—C14—H14B	109.1
O9—Cu2—Cu1	75.77 (8)	H14A—C14—H14B	107.9
O5—Cu2—Cu1	74.05 (8)	N4—C13—C14	111.2 (3)
N1—Cu2—Cu1	176.85 (9)	N4—C13—H13A	109.4
C3—N2—C1	114.3 (3)	C14—C13—H13A	109.4
N3—C2—N1	125.5 (3)	N4—C13—H13B	109.4
N3—C2—N5	117.0 (3)	C14—C13—H13B	109.4
N1—C2—N5	117.5 (3)	H13A—C13—H13B	108.0
C26—O3—Cu1	119.9 (3)	N7—C12—C11	124.6 (6)
C2—N3—C3	113.3 (3)	N7—C12—H12	117.7
N2—C3—N3	128.1 (3)	C11—C12—H12	117.7
N2—C3—O23	119.2 (4)	O10—C20—O4	125.2 (4)
N3—C3—O23	112.7 (3)	O10—C20—C21	117.7 (4)
C20—O4—Cu2	118.7 (2)	O4—C20—C21	117.1 (3)
C1—N4—C13	123.3 (3)	C20—C21—H21A	109.5
C1—N4—H1	118.4	C20—C21—H21B	109.5
C13—N4—H1	118.4	H21A—C21—H21B	109.5
O23—C4—C5	111.1 (4)	C20—C21—H21C	109.5
O23—C4—H4A	109.4	H21A—C21—H21C	109.5
C5—C4—H4A	109.4	H21B—C21—H21C	109.5
O23—C4—H4B	109.4	C3—O23—C4	117.1 (3)
C5—C4—H4B	109.4	C22—C23—H23A	109.5
H4A—C4—H4B	108.0	C22—C23—H23B	109.5
C22—O5—Cu2	132.8 (3)	H23A—C23—H23B	109.5
C2—N5—C6	123.2 (3)	C22—C23—H23C	109.5
C2—N5—H2	118.4	H23A—C23—H23C	109.5
C6—N5—H2	118.4	H23B—C23—H23C	109.5
C4—C5—H5A	109.5	O5—C22—O6	124.7 (4)
C4—C5—H5B	109.5	O5—C22—C23	117.2 (4)
H5A—C5—H5B	109.5	O6—C22—C23	118.1 (4)
C4—C5—H5C	109.5	O9—C26—O3	125.0 (4)
H5A—C5—H5C	109.5	O9—C26—C27	116.9 (4)
H5B—C5—H5C	109.5	O3—C26—C27	118.1 (4)
C22—O6—Cu1	118.3 (3)	C24—C25—H25A	109.5
C19—N6—C15	118.2 (3)	C24—C25—H25B	109.5
C19—N6—Cu1ⁱⁱ	116.8 (3)	H25A—C25—H25B	109.5
C15—N6—Cu1ⁱⁱ	124.9 (2)	C24—C25—H25C	109.5
N5—C6—C7	112.9 (4)	H25A—C25—H25C	109.5
N5—C6—H6A	109.0	H25B—C25—H25C	109.5
C7—C6—H6A	109.0	O2—C24—O1	125.2 (4)
N5—C6—H6B	109.0	O2—C24—C25	117.9 (4)
C7—C6—H6B	109.0	O1—C24—C25	116.9 (4)
H6A—C6—H6B	107.8	C26—C27—H27A	109.5
C8—C7—C6	112.3 (4)	C26—C27—H27B	109.5
C8—C7—H7A	109.2	H27A—C27—H27B	109.5
C6—C7—H7A	109.2	C26—C27—H27C	109.5
C8—C7—H7B	109.2	H27A—C27—H27C	109.5
C6—C7—H7B	109.2	H27B—C27—H27C	109.5
H7A—C7—H7B	107.9	C24—O2—Cu1	130.7 (3)
C12—N7—C8	117.3 (5)

C2—N1—C1—N4	179.7 (3)	C19—C18—C17—C16	−1.8 (7)
Cu2—N1—C1—N4	−5.0 (5)	C18—C17—C16—C15	1.7 (6)
C2—N1—C1—N2	−0.8 (5)	C19—N6—C15—C16	−1.8 (6)
Cu2—N1—C1—N2	174.5 (3)	Cu1ⁱⁱ—N6—C15—C16	175.6 (3)
N4—C1—N2—C3	177.2 (4)	C19—N6—C15—C14	−179.9 (3)
N1—C1—N2—C3	−2.2 (6)	Cu1ⁱⁱ—N6—C15—C14	−2.6 (5)
C1—N1—C2—N3	3.0 (6)	C17—C16—C15—N6	0.1 (6)
Cu2—N1—C2—N3	−172.2 (3)	C17—C16—C15—C14	178.2 (4)
C1—N1—C2—N5	−177.5 (3)	N6—C15—C14—C13	87.7 (4)
Cu2—N1—C2—N5	7.2 (5)	C16—C15—C14—C13	−90.5 (4)
N1—C2—N3—C3	−1.8 (6)	C1—N4—C13—C14	86.6 (4)
N5—C2—N3—C3	178.8 (3)	C15—C14—C13—N4	69.7 (4)
C1—N2—C3—N3	3.8 (6)	C8—N7—C12—C11	0.4 (9)
C1—N2—C3—O23	−177.8 (3)	C10—C11—C12—N7	−1.7 (9)
C2—N3—C3—N2	−2.0 (6)	Cu1—O10—C20—O4	−1.8 (7)
C2—N3—C3—O23	179.6 (3)	Cu1—O10—C20—C21	178.3 (3)
N2—C1—N4—C13	4.3 (6)	Cu2—O4—C20—O10	0.0 (6)
N1—C1—N4—C13	−176.2 (3)	Cu2—O4—C20—C21	180.0 (3)
N3—C2—N5—C6	−5.8 (6)	N2—C3—O23—C4	4.5 (6)
N1—C2—N5—C6	174.7 (4)	N3—C3—O23—C4	−176.8 (3)
C2—N5—C6—C7	−94.9 (5)	C5—C4—O23—C3	79.3 (5)
N5—C6—C7—C8	−69.1 (5)	Cu2—O5—C22—O6	−5.0 (6)
C12—N7—C8—C9	1.5 (7)	Cu2—O5—C22—C23	174.2 (3)
C12—N7—C8—C7	180.0 (5)	Cu1—O6—C22—O5	1.3 (5)
C6—C7—C8—N7	−87.7 (5)	Cu1—O6—C22—C23	−177.9 (3)
C6—C7—C8—C9	90.8 (6)	Cu2—O9—C26—O3	−4.0 (6)
N7—C8—C9—C10	−2.0 (8)	Cu2—O9—C26—C27	174.7 (3)
C7—C8—C9—C10	179.6 (5)	Cu1—O3—C26—O9	2.4 (6)
C8—C9—C10—C11	0.6 (9)	Cu1—O3—C26—C27	−176.2 (3)
C9—C10—C11—C12	1.1 (9)	Cu2—O1—C24—O2	0.3 (6)
C15—N6—C19—C18	1.7 (6)	Cu2—O1—C24—C25	179.3 (3)
Cu1ⁱⁱ—N6—C19—C18	−175.9 (3)	O1—C24—O2—Cu1	−0.9 (6)
N6—C19—C18—C17	0.1 (7)	C25—C24—O2—Cu1	−179.9 (3)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N4—H1···O5	0.88	1.89	2.767 (4)	171
N5—H2···O9	0.88	1.99	2.857 (4)	168

Selected geometric parameters (Å) top

Cu1—O6	1.939 (3)	Cu2—O1	1.927 (3)
Cu1—O3	1.946 (3)	Cu2—O4	1.926 (3)
Cu1—O10	2.026 (3)	Cu2—O9	2.035 (3)
Cu1—O2	2.062 (3)	Cu2—O5	2.047 (3)
Cu1—N6i	2.147 (3)	Cu2—N1	2.180 (3)
Cu1—Cu2	2.7889 (8)

Symmetry codes: (i) x, -y+1/2, z-1/2

Acknowledgements

We thank Matthias Zeller (Purdue University) for his advice on data collection for the reported crystal structure.

Funding information

Funding for this research was provided by: National Science Foundation (award No. CHE-1900541).

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