Copper(II) acetate structures with benzimidazole derivatives

Copper(II) acetate structures with benzimidazole derivatives

Accepted Manuscript Research paper Copper(II) acetate structures with benzimidazole derivatives Oleg Semyonov, Konstantin A. Lyssenko, Damir A. Safin ...

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Accepted Manuscript Research paper Copper(II) acetate structures with benzimidazole derivatives Oleg Semyonov, Konstantin A. Lyssenko, Damir A. Safin PII: DOI: Reference:

S0020-1693(18)31076-4 https://doi.org/10.1016/j.ica.2018.12.054 ICA 18721

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Inorganica Chimica Acta

Received Date: Revised Date: Accepted Date:

12 July 2018 26 November 2018 31 December 2018

Please cite this article as: O. Semyonov, K.A. Lyssenko, D.A. Safin, Copper(II) acetate structures with benzimidazole derivatives, Inorganica Chimica Acta (2018), doi: https://doi.org/10.1016/j.ica.2018.12.054

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Copper(II) acetate structures with benzimidazole derivatives Oleg Semyonov a,b, Konstantin A. Lyssenko c, Damir A. Safin *,d a b

Limited Liability Company «NIOST», Kuzovlevski trakt 2, 634067, Tomsk, Russian Federation Department of Technology of Organic Substances and Polymer Materials, National Research Tomsk

Polytechnic University, Lenin ave. 43, 634050, Tomsk, Russian Federation c

A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova Str. 28,

119991, Moscow, Russian Federation d

Institute of Chemistry, University of Tyumen, Perekopskaya Str. 15a, 625003, Tyumen, Russian Federation

Abstract The evaluation of 2-phenylbenzimidazole (LI) and 2-(2-iodophenyl)-5-chlorobenzimidazole (LII) as basic ligand precursors in the synthesis of novel copper(II) acetate structures is described. A reaction of Cu(OAc)2 with LI and LII in aqueous alcoholic solution in the presence of acetic acid leads to heteroleptic mononuclear complexes [Cu(OAc)2LI2] (1) and [Cu(OAc)2LII2]·2AcOH (2·2AcOH), respectively. According to single-crystal X-ray diffraction and FTIR spectroscopy, a monodentate and an anisobidentate coordination mode of the OAc– anion was established in 1 and 2·2AcOH, respectively. The structures of both 1 and 2·2AcOH are stabilized by classic intermolecular H-bonds yielding a simplified underlying network with the uninodal 4-connected topology sql/Shubnikov tetragonal plane net and with the binodal 2,4-connected topology 2,4L2, respectively. The former structure also contains intermolecular π⋯π stacking interactions. LI was found to be emissive in the solid state at room temperature with the emission band centered at 420 nm due to intraligand π*→π and π*→n transitions. The CIE chromaticity diagram quantified the blue color of the emission.

Keywords: Coordination chemistry; Copper acetate; Benzimidazole; Crystal structure; Hirshfeld surface analysis; Optical properties

* Corresponding author. E-mail address: [email protected], [email protected] (D. A. Safin).

1. Introduction Copper is vital for many processes in biological systems. It is an essential element in the structures of enzymes [1,2]. Particularly, a relatively simple trans-bis(acetate)bis(imidazole)copper(II) provides the strongest antitumor activity in treatment of the mouse melanoma cancer cell line B16 [3]. In general, complexes of Cu(OAc)2 with imidazole-based ligands are of ever growing interest and have been examined for copper proteins [4–7]. Furthermore, a number of such copper(II) complexes possess antitumor [3,8] and superoxide dismutase activities [9]. The Cu(OAc)2-derived complexes with imidazole and with Nmethylimidazole have been reported [3,10]. The former complex is monomeric and constructed from the CuN2O2 chromophore in a trans-square planar arrangement [3], while the latter one exhibits a dimeric structure, where two OAc– act as monodentate bridging ligands and metal atoms are in a distorted square pyramidal environment [10]. Using 2-methylimidazole and 1,2-dimethylimidazole in the reaction with Cu(OAc)2 also leads to the formation of monomeric structures with the square-planar CuN2O2 coordination core; however the monodentate imidazole derived ligands are coordinated in a cis-configuration [11]. Interestingly, interaction of 2-ethylimidazole with Cu(OAc)2 produces a dimeric structure, constructed from two CuNO3 chromophores, linked via two OAc– anions [12]. On the other hand, non-covalent interactions (e.g. H-bonding, π⋯π stacking, C–H⋯π interaction, (di)halogen interactions, etc.) are crucial for the self-assembled architectures in supramolecular chemistry [13–16]. As such, non-covalent interactions is one of the most powerfull tools to design and tune the final structure and properties (e.g. electronic, magnetic, optic, sorption and catalytic) of metal-organic hybrid materias [17–20]. Furthermore, supramolecular synthons are vital for coordination polymers and, particularly, for metal-organic frameworks (MOFs) [21,22]. MOFs exhibiting a three-dimensional structure have been a growing area of research [21,22]. Among MOFs, the so-called zeolitic imidazolate frameworks (ZIFs) are a relatively new class of compounds that are topologically isomorphic with zeolites [23–25]. ZIFs are constructed from metal atoms/ions and imidazolate/imidazole linkers. Thus, the coordination chemistry of imidazole derivatives are of great importance and attracts particular interest. In this work we report for the first time the synthesis, complete spectroscopic and X-ray structural characterization of Cu(OAc)2 complexes with 2-phenylbenzimidazole (LI) and 2-(2-iodophenyl)-5chlorobenzimidazole (LII) ligands, namely [Cu(OAc)2LI2] (1) and [Cu(OAc)2LII2]·2AcOH (2·2AcOH). Our

main goal was to explore how LI and LII interacts with Cu(OAc)2 under certain experimental conditions as well as to study the observed intermolecular interactions in the solid state of the resulting complexes. Furthermore, optical properties in the solid state were also in the limelight of this work. It is worthy to note, that the products formed upon interaction of Cu(OAc)2 with basic ligands are partially driven by the electronic properties of the ligand. However, the correlation between resulting structures and electronic properties is not straightforward.

2. Results and discussion An in situ reaction of Cu(OAc)2·H2O with LI and LII in aqueoues EtOH in the presence of acetic acid produces mononuclear complexes 1 and 2·2AcOH, respectively (Scheme 1), which were obtained in good yields and were fully characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, single-crystal X-ray diffraction, topological and Hirshfeld surface analyses. All the reported compounds were also examined by solid-state diffuse reflectance spectroscopy and their luminescent properties were studied. Single crystal X-ray diffraction revealed that 1 and 2·2AcOH crystallize in the monoclinic space groups P21/c and P21/n, respectively. The asymmetric unit of 1 contains two halves of two crystallographically independent [Cu(OAc)2LI2] coordination units (Fig. 1), named hereafter as 1-I and 1-II, for Cu(1) and Cu(2), respectively, while the asymmetric unit of 2·2AcOH contains one half of the molecule 2 and one molecule of the lattice AcOH. Notably, the chlorine atom in 2 is disordered over two positions 5 and 6 within the benzimidazole fragment with a ratio of 90.7% and 9.3%. Only the molecule 2 with a major contribution of the chlorine atom will be considered hereafter. The metal atoms in both 1 and 2 occupy almost perfect square environments, composed of two imidazole N-atoms and two O-atoms from the OAc– anions, in a trans-coordination environment (Fig. 1, Table 1). The OAc– ligands in both structures were found in a proximal conformation with the uncoordinated O-atom being in a cis-orientation relative to the copper(II) atom. This is also reflected in the Cu–O–C–O torsion angles, which are significantly lower than 90° in both structures. Notably, the OAc– anions in 1-I and 1-II are coordinated in a monodentate manner as evidenced from the criteria listed in Table 2 [26]. Particularly, the d values are 0.97 and 0.99 Å, and the θ values are 45.2 and 46.8° for 1-I and 1-II,

respectively. The same values for the OAc– ligands in 2 are 0.61 Å and 28.5°, respectively, and are on the border between for the monodentate and anisobidentate coordination modes (Table 2). The Cu–N and Cu–O bond lengths in 1 and 2 are ~1.93–2.00 Å (Table 1). The Cu∙∙∙O separations in 2 are ~2.59 Å, while the same separations in 1 are significantly longer and ~2.92 Å (Table 1). The bond lengths between the carboxyl С-atom and the coordinated acetate O-atom are about 0.05 and 0.01 Å longer than those between the carboxyl С-atom and uncoordinated O-atom in 1-I and 1-II, respectively, while these distances are very similar in 2 (Table 1). The phenyl and phenylene fragments in 1-I, 1-II and 2, respectively, deviate significantly from the benzimidazole planes with the most significant deviation observed in 2 (Fig. 1, Table 1). This is obviously due to the presence of ortho-iodine substituent in LII. The lattice of 1 is constructed from discrete molecules linked via N–H∙∙∙O hydrogen bonds formed between the imidazole NH H-atoms and the uncoordinated carboxylate O-atoms of neighboring molecules and vice versa (Fig. 2, Table 3). The intermolecular H-bonding leads to the 2D network, which, from a topological point of view, is assembled from the 4-connected [Cu(OAc)2LI2] nodes and can be classified as a uninodal 4-connected topology sql/Shubnikov tetragonal plane net defined by the point symbol of (44∙62) (Fig. 3). This 2D network is further stabilized by intermolecular π⋯π stacking interactions (Fig. 2, Table 4), formed between the imidazole and benzo aromatic rings arising from adjacent molecules. The crystal packing of 2·2AcOH is mainly dictated by the AcOH lattice molecules. Strong classic N– H∙∙∙O and O–H∙∙∙O hydrogen bonds were determined between the imidazole NH H-atoms and the carbonyl O-atoms as well as the OH protons of the acid molecules and the weakly coordinated acetate O-atoms (Fig. 2, Table 3). The intermolecular H-bonding in 2·2AcOH also yield a 2D network. However, from a topological point of view, this network is now assembled from the 4- and 2-connected [Cu(OAc)2LII2] and AcOH nodes, respectively and can be classified as a binodal 2,4-connected topology 2,4L2 defined by the point symbol of (84∙122)(8)2 (Fig. 3). Further simplification of this topology by removing 2-connected bridging AcOH nodes yields a uninodal 4-connected topology sql/Shubnikov tetragonal plane net defined by the point symbol of (44∙62) as it was observed in 1 (Fig. 3). Notably, the Cambridge Structural Database (CSD) contains seven crystal structures with the ligand LI of which only three structures with metals (CuI [27], RuII [28] and IrIII [29]) and no structures with the ligand LII.

The carboxylate coordination modes can firmly be assigned via IR spectroscopy using the following trend: chelating < bridging < ionic < monodentate, where  = asym(OCO) – sym(OCO) [30–33]. The  value of the Na-salt of the same carboxylate is used as a reference for comparison of the  value of the studied carboxylate complexes. With all this in mind we have thorougly examined IR spectra of both complexes. The FTIR spectrum of 1 revealed a band at 1563 cm–1 with two shoulders at 1600 and 1542 cm–1 for asym(OCO) and a band at 1395 cm–1 for sym(OCO) (Fig. 4). The  = 205 cm–1 value for 1-I is higher than that for NaOAc ( = 164 cm–1) [34], indicating a monodentate coordination mode of OAc–. We have also assigned a monodentate coordination mode of the second OAc– from the molecule 1-II as evidenced from the  = 168 cm–1 value. The FTIR spectrum of 2·2AcOH is much more complicated with respect to the asym(OCO) and sym(OCO) bands due to the presence of both OAc– and AcOH species (Fig. 4). The spectrum revealed an intense band at 1570 cm–1 with a shoulder at 1560 cm–1 accompanied with a band at 1522 cm–1 for asym(OCO) and an intense band at 1400 cm–1 with a number of shoulders at 1415–1485 cm– 1

for sym(OCO) (Fig. 4). The calcd value can be related with parameters r and θOCO obtained from single-crystal X-ray

diffraction using the empirical equation calcd = 1818.1r + 16.47(θOCO – 120) + 66.8 (r is the difference between the two C–O bond lengths in Å; θOCO is the OCO angle in °) [35]. The calcd values for 1-I and 1-II were found to be 215 and 181 cm–1 and are in good agreement with the experimental  values obtained from the corresponding FTIR spectrum. The calcd value for 2·2AcOH is 94 cm–1 and can also be found among the experimental  values obtained from the FTIR spectrum. This value is significantly lower than that for NaOAc and can tentatively be assigned to a chelating (aniso)bidentate coordination mode. Thus, both the single-crystal X-ray analysis and FTIR spectroscopy testify to a monodentate and an anisobidentate coordination mode of the OAc– anion in the structures of complexes. Optical properties of all the reported compounds were for the first time examined by diffuse reflectance spectroscopy. Pure solid powders were used to avoid matrix and environment effects. The Kubelka-Munk treatment [36–38] was applied to the obtained data. The spectra of LI and LII contain a broad band with maxima in the UV region (Fig. 5). These bands are due to intra-ligand transitions. The spectrum

of LI also exhibits a shoulder at 375–600 nm (Fig. 5). This shoulder explains the observed beige colour of this compound and most likely due to the formation of supramolecular aggregates between the planar molecules via π∙∙∙π stacking [39–41]. The spectra of 1 and 2·2AcOH are characterized by two distinct regions (Fig. 5). Bands in the UV region are also explained by intra-ligand transitions, while the second range at about 450–1000 nm originates from the d–d transition [42]. Among all herein reported compounds, it was found that only LI is luminescent in the solid state under ambient conditions. The spectrum exhibits a broad emission band with the maximum at 420 nm (Fig. 6), which can be assigned to the intra-ligand π*→π and π*→n transitions. The chromaticity coordinates for LI were found using the CIE chromaticity diagram [43,44] and are (0.19, 0.16). These values are in the blue region of the diagram (Fig. 6). The crystal structures of 1-I and 2 were examined by the Hirshfeld surface analysis [45–47] to study intermolecular interactions. We have also found the enrichment ratios (E) [48] of these interactions to establish the propensity of two species to be in contact. For 1-I the intermolecular H⋯H (56.1%), H⋯C (21.6%) and H⋯O (12.7%) are major contributors. The latter two contacts in 2 each occupy a similar proportion of the total Hirshfeld surface area as in 1-I (Table 5), while a proportion of the H⋯H contacts is significantly lower (29.9%). This is obviously explained by the presence of the H⋯Cl (11.7%) and H⋯I (13.0%) contacts in 2. The shortest H⋯H and H⋯C contacts are shown in the corresponding fingerprint plots of 1-I and 2 at de + di ≈ 2.2 and 2.7 Å (Fig. 7 and 8). The shortest H⋯O contacts in the plots of 1-I and 2 are shown as two sharp spikes at de + di ≈ 1.6– 1.9 Å (Fig. 7 and 8) and correspond to the N–H⋯O and O–H⋯O hydrogen bonds (Table 3). Furthermore, the shortest H⋯Cl and H⋯I contacts in the fingerprint plot of 2 were found as two broad spikes at de + di ≈ 2.9 and 3.2 Å (Fig. 8). 1-I is further described by a negligible proportion of the C⋯C and C⋯N contacts (Table 5), which are shown as the area on the diagonal at de = di ≈ 1.7–2.2 Å (Fig. 7) and correspond to π⋯π stacking interactions (Table 4). The H⋯H, H⋯O and C⋯C contacts in 1-I as well as H⋯X (X = C, N, O, Cl, I) and C⋯O contacts in 2 are favoured as evidenced from the corresponding enrichment ratios, which are larger than unity (Table 5). The H⋯C contacts in 1-I as well as H⋯H and Cl⋯I contacts in 2 are much less favoured (E = 0.70–0.82).

This is due to a high amount of the corresponding random contacts (Table 5). Finally, the remaining contacts are very impoverished with the enrichment ratios being 0.21–0.45 (Table 5).

3. Conclusions In summary, we have designed and fully characterized new Cu(OAc)2-derived complexes with the 2phenylbenzimidazole (LI) and 2-(2-iodophenyl)-5-chlorobenzimidazole (LII), namely [Cu(OAc)2LI2] (1) and [Cu(OAc)2LII2]·2AcOH (2·2AcOH), respectively. The nature of the imidazole-based ligand influences the coordination mode of the OAc– ligand. Single-crystal X-ray diffraction and FTIR spectroscopy revealed a monodentate and an anisobidentate coordination mode of the OAc– anion in 1 and 2·2AcOH, respectively. The structures of both 1 and 2·2AcOH are stabilized by classic intermolecular H-bonds yielding a simplified underlying network with the uninodal 4-connected topology sql/Shubnikov tetragonal plane net and with the binodal 2,4-connected topology 2,4L2, respectively. The former structure is additionally stabilized by intermolecular π⋯π stacking interactions. LI alone was found to be emissive in the solid state under ambient conditions with the emission band centered at 420 nm due to the intra-ligand π*→π and π*→n transitions. The blue color of the emission was established with the CIE chromaticity diagram.

4. Experimental 4.1. Materials Ligands LI and LII were synthesized as described elsewhere [49,50]. All other reagents and solvents were commercially available and used as without further purification.

4.2. Synthesis of 1 and 2·2AcOH To an aqueous ethanol solution (1:2 v/v, 1.5 mL) containing Cu(OAc)2·2H2O (0.022 g, 0.1 mmol) was added LI or LII (0.039 or 0.071 g, respectively; 0.2 mmol). The resulting mixture was adjusted to pH ~6 with dilute acetic acid and then stirred at 70 °C for 20 min. Then it was filtered from unreacted particles. The crystalline product was collected after slow evaporation at room temperature for about a week. 1. Blue plate-like crystals. Yield: 0.049 g (86%). Anal. Calc. for C30H26CuN4O4 (570.11) (%): C 63.20, H 4.60 and N 9.83; found: С 63.32, Н 4.53 and N 9.89.

2·2AcOH. Blue block-like crystals. Yield: 0.092 g (91%). Anal. Calc. for C34H30Cl2CuI2N4O8 (1010.90) (%): C 40.40, H 2.99 and N 5.54; found: С 40.49, Н 2.91 and N 5.60.

4.3. Physical measurements FTIR spectra were recorded on a VARIAN Excalibur HE 3600 spectrometer. Diffuse reflectance spectra were obtained with a Analytik Jena SPECORD 200 spectrometer using polytetrafluoroethylene (PTFE) as a reference. Spectra were measured on pure solids to avoid matrix effects. Eventual distortions in the Kubelka-Munk spectra that could result from the study of pure compounds have not been considered because no comparison with absorption spectra was necessary. The solid-state emission spectra were obtained with a VARIAN Cary Eclipse fluorescence spectrophotometer. Microanalyses were performed using a ElementarVario EL III analyzer.

4.4. Topological analysis Topological analysis was performed with the ToposPro software [51] following the concept of the simplified underlying net [51–53]. For the generation of such underlying supramolecular nets, the classic hydrogen bonds were considered. The obtained simplified nets were then classified from the topological viewpoint [51–55].

4.5. Single-crystal X-ray diffraction The X-ray diffraction data for 1 and 2·2AcOH were collected on a Bruker APEX2 DUO CCD diffractometer. The intensity data were integrated by the SAINT program [56] and were corrected for absorption and decay using TWINABS [56] for 1 and SADABS [57] for 2·2AcOH. The structures were solved with direct methods and refined by the full-matrix least-squares technique against F2hkl in anisotropic approximation for non-hydrogen atoms with the SHELX [58] software package. The studied crystal of 1 was a twin with the ratio for two major components being of 0.440(1):0.660(1). The twin operation for 1 is a twofold rotation around the c axis. The structure of 2·2AcOH was a non-merohedral twin. The intensities of overlapping reflections for 2·2AcOH (for twin law 1 0 1 0 –1 0 0 0 –1) were corrected with algorithms implemented in the PLATON software package [59]. The ratio for two major

in components 2·2AcOH was 0.380(1) and 0.620(1). The NH and OH hydrogen atoms were found from difference Fourier synthesis and refined isotropically. The positions of other hydrogen atoms were calculated, and all hydrogen atoms were refined in riding model with Uiso(H) = 1.5Ueq(Cm) and 1.2Ueq(Ci), where Ueq(Cm) and Ueq(Ci) are the equivalent thermal parameters of the parent methyl carbon and all other carbon atoms, respectively. Figures were generated using the program Mercury [60]. Crystal data for 1: C30H26CuN4O4, Mr = 570.09 g mol−1, T = 120(2) K, monoclinic, space group P21/c, a = 20.210(4), b = 14.806(3), c = 8.8101(17) Å,  = 102.473(4)°, V = 2574.0(9) Å3, Z = 4, ρ = 1.471 g cm−3, μ(Mo-Kα) = 0.893 mm−1, reflections: 25105 collected, 6209 unique, Rint = 0.071, R1 = 0.0555 (for 4527 observed reflections), R1(all) = 0.0816, wR2(all) = 0.1558. Crystal data for 2·2AcOH: C30H22Cl2CuI2N4O4, 2(C2H4O2), Mr = 1010.86 g mol−1, T = 120(2) K, monoclinic, space group P21/n, a = 15.184(3), b = 7.9909(16), c = 15.765(3) Å,  = 103.26(3)°, V = 1861.8(7) Å3, Z = 2, ρ = 1.803 g cm−3, μ(Mo-Kα) = 2.443 mm−1, reflections: 21392 collected, 4965 unique, Rint = 0.053, R1 = 0.0500 (for 4045 observed reflections), R1(all) = 0.0722, wR2(all) = 0.1150. CCDC 1836318 and 1836319 contain the supplementary crystallographic data. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or email: [email protected]

Acknowledgements This work was supported by Research Resource Center "Natural Resource Management and PhysicoChemical Research" (Institute of Chemistry, University of Tyumen).

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H N N O Cu O N O

LI

O

N H [Cu(OAc)2LI2] (1)

Cu(OAc)2

H N

LII

I

N O Cu O N O

Cl

O

I

Cl

2AcOH

N H

[Cu(OAc)2LII2 ] 2AcOH (2 2AcOH) Scheme 1. Synthesis of complexes 1 and 2·2AcOH.

Fig. 1. Crystal structure of 1-I (top) and 2 (bottom). 50% atomic displacement ellipsoids are shown. Colour code: H =black, C = gold, N = blue, Cl = green, I = purple, Cu = magenta.

Fig. 2. Hydrogen bonds and π∙∙∙π interactions in the crystal structure of 1 (left) and hydrogen bonds in the crystal structure of 2·2AcOH (right). 50% atomic displacement ellipsoids are shown. CH hydrogen atoms were omitted for clarity. Colour code: H =black, C = gold, N = blue, Cl = green, I = purple, Cu = magenta.

Fig. 3. (top) A simplified underlying network of 1 with the uninodal 4-connected topology sql/Shubnikov tetragonal plane net defined by the point symbol of (44∙62). (bottom) A simplified underlying network of 2·2AcOH with the binodal 2,4-connected topology 2,4L2 defined by the point symbol of (84∙122)(8)2 (color code: [Cu(OAc)2LI,II2] = red, AcOH = green).

2.2AcOH II

L

1 I

L 3500

3000

2500

2000

1500

-1

Wavenumber (cm ) Fig. 4. FTIR spectra of LI, LII, 1 and 2·2AcOH.

1000

500

I

L 1

II

L 2.2AcOH

200

300

400

500

600

700

 (nm)

800

900 1000 1100

Fig. 5. Normalised Kubelka-Munk spectra of LI, LII, 1 and 2·2AcOH.

200

250

300

350

400

 (nm)

450

500

550

600

Fig. 6. (top) Room-temperature emission (blue, exc = 300 nm) and excitation (black, em = 420 nm) spectra of LI. (bottom) CIE-1931 chromaticity diagram and the calculated CIE coordinates, located at (0.19, 0.16) for LI (marked by the red circle).

Fig. 7. 2D and decomposed 2D fingerprint plots of observed contacts for 1-I.

Fig. 8. 2D and decomposed 2D fingerprint plots of observed contacts for 2.

Table 1 Selected bond lengths (Å) and angles (°) for 1-I, 1-II and 2. 1-I

1-II

2

Cu–N

1.963(4)

1.998(3)

1.973(5)

Cu–O

1.951(3)

1.936(3)

1.973(3)

Cu∙∙∙O

2.917(3)

2.930(3)

2.587(4)

C–O(–Cu)

1.283(6)

1.272(6)

1.264(6)

C–O(∙∙∙Cu)

1.236(6)

1.258(6)

1.258(7)

N–Cu–N

180.00

180.00

180.00

N–Cu–O

89.26(13), 90.74(13)

89.28(13), 90.72(13)

89.82(17), 90.18(17)

O–Cu–O

180.00

180.00

180.00

N–Cu∙∙∙O

77.86(13), 102.14(13)

76.97(13), 103.03(13)

87.38(17), 92.62(17)

O–Cu∙∙∙O

49.59(12), 130.42(12)

50.07(11), 129.93(11)

55.61(15), 124.39(15)

O∙∙∙Cu∙∙∙O

180.00

180.00

180.00

O–C–O

123.8(4)

125.4(4)

121.0(5)

38.16(19)

38.0(2)

52.6(3)

Bond lengths

Bond angles

Torsion angle Benzimidazole∙∙∙Ph

Table 2 Criteria for assigning carboxylate coordination modes.a d1

M

O

1 d2

R 2

O

d = d2 – d1, θ = θ1 – θ2 Coordination mode

d (Å)

θ (°)

Monodentate

>0.6

>28

Anisobidentate

0.3–0.6

14–28

Bidentate

<0.3

<14

a

Adopted from the values for nitrate ligands [26].

Table 3 Classic hydrogen bond lengths (Å) and angles (°) for 1 and 2·2AcOH.

1a 2b

a

D–H∙∙∙A

d(D–H)

d(H∙∙∙A)

d(D∙∙∙A)

(DHA)

N(2)–H(2N)∙∙∙O(2C)#1

0.82

1.95

2.755(5)

165

N(2A)–H(2NA)∙∙∙O(5)#2

0.82

1.99

2.793(5)

166

O(4C)–H(4OC)∙∙∙O(2C)#1

0.95

1.64

2.552(7)

160

N(2)–H(2N)∙∙∙O(3C)#2

0.85

1.90

2.677(7)

152

Symmetry transformations used to generate equivalent atoms: #1: –x, 1/2 + y, 3/2 – z; #2: 1 – x, 1/2 + y, 3/2 – z. b Symmetry transformations used to generate equivalent atoms: #1: –x, –y, –z; #2: –1/2 + x, 1/2 – y, –1/2 + z.

Table 4 π∙∙∙π interaction distances (Å) and angles (°) for 1.a Complex

Cg(I)

Cg(J)

d[Cg(I)–Cg(J)]

α

β

γ

slippage

1b

Cg(3)

Cg(4)#1

3.557(3)

2.1(3)

12.8

14.0

0.790

Cg(4)

Cg(3)#2

3.557(3)

2.1(3)

14.0

12.8

0.859

Cg(9)

Cg(10)#2

3.567(3)

3.5(3)

12.1

16.3

0.746

Cg(10)

Cg(9)#1

3.567(3)

3.5(3)

16.3

12.1

0.942

a

Cg(I)–Cg(J): distance between ring centroids; α: dihedral angle between planes Cg(I) and Cg(J); β: angle Cg(I) → Cg(J) vector and normal to plane I; γ: angle Cg(I) → Cg(J) vector and normal to plane J; slippage: distance between Cg(I) and perpendicular projection of Cg(J) on ring I. b Symmetry transformations used to generate equivalent atoms: #1 x, 3/2 – y, –1/2 + z; #2 –x, 3/2 – y, 1/2 + z. Cg(3): N(1A)–C(1A)–N(2A)–C(3A)–C(2A), Cg(4): C(2A)–C(3A)–C(4A)–C(5A)– C(6A)–C(7A), Cg(9): N(1)–C(1)–N(2)–C(3)–C(2), Cg(10): C(2)–C(3)–C(4)–C(5)–C(6)–C(7).

Table 5 (top) 2D fingerprint plots of observed contacts for 1-I and 2. (bottom) Hirshfeld contact surfaces and derived “random contacts” and “enrichment ratios” for 1-I and 2.a H

C

N

O

H

C

N

O

Cl

I

Contacts (C, %)a H

56.1







29.9











C

21.6

5.1





22.3

0.0









N

0.7

3.8

0.0



3.2

0.3

0.0







O

12.7

0.0

0.0

0.0

14.1

2.5

0.0

0.3





Cl









11.7

0.7

0.0

0.4

0.0



I









13.0

0.9

0.0

0.0

0.7

0.0

17.8

2.3

6.3

62.1

13.4

1.7

8.8

6.7

7.3

Surface (S, %) 73.6

Random contacts (R, %) H

54.2







38.6











C

26.2

3.2





16.6

1.8









N

3.4

0.1

0.1



2.1

0.5

0.0







O

9.3

2.2

0.3

0.4

10.9

2.4

0.3

0.8





Cl









8.3

1.8

0.2

1.2

0.4



I









9.1

2.0

0.2

1.3

1.0

0.5

Enrichment (E)b H

1.03







0.77











C

0.82

1.59





1.34

0.0









N

0.21







1.52











O

1.37

0.0





1.29

1.04









Cl









1.41

0.39



0.33





I









1.43

0.45



0.0

0.70



a

Values are obtained from CrystalExplorer 3.1 [47].

b

The enrichment ratios were not computed when the “random contacts” were lower than 0.9%, as they are

not meaningful [48].

Graphical abstract

The evaluation of 2-phenylbenzimidazole (LI) and 2-(2-iodophenyl)-5-chlorobenzimidazole (LII) as basic ligand precursors in the synthesis of novel copper(II) acetate structures is described. H N N O Cu O N O

LI

O

N H [Cu(OAc)2LI2] (1)

Cu(OAc)2

H N

LII

I

N O Cu O N O

Cl

O

I

Cl

2AcOH

N H

[Cu(OAc)2LII2 ] 2AcOH (2 2AcOH)

Highlights  Copper(II)

acetate

complexes

with

2-phenylbenzimidazole

(LI)

and

2-(2-iodophenyl)-5-

chlorobenzimidazole (LII) are described.  Heteroleptic mononuclear complexes [Cu(OAc)2LI2] (1) and [Cu(OAc)2LII2]·2AcOH (2·2AcOH) were obtained.  A monodentate and an anisobidentate coordination mode of the OAc– anion was established in 1 and 2·2AcOH, respectively. 

LI was found to be emissive in the solid state at room temperature with the emission band centered at 420 nm.