Crystal structure of 4-(dimethylamino)pyridin-1-ium-2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine (2:1) water undeca-solvate European Journal of Chemistry 11 (3) (2020) 255-260 European Journal of Chemistry ISSN 2153-2249 (Print) / ISSN 2153-2257 (Online) – Copyright © 2020 The Authors – Atlanta Publishing House LLC – Printed in the USA. This work is published and licensed by Atlanta Publishing House LLC – CC BY NC – Some Rights Reserved. http://dx.doi.org/10.5155/eurjchem.11.3.255-260.2019 European Journal of Chemistry View Journal Online View Article Online Crystal structure of 4-(dimethylamino)pyridin-1-ium-2,5-dichloro-3,6- dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine (2:1) water undeca-solvate Alebel Nibret Belay 1,*, Johan Andries Venter 2 and Orbett Teboho Alexander 2 1 Department of Chemistry, Bahir Dar University, P.O. Box 79, Bahir Dar, Ethiopia alebel.nibret@bdu.edu.et (A.N.B.) 2 Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa venterja@ufs.ac.za (J.A.V.), alexandero@ufs.ac.za (O.T.A.) * Corresponding author at: Department of Chemistry, Bahir Dar University, P.O. Box 79, Bahir Dar, Ethiopia. e-mail: alebel.nibret@bdu.edu.et (A.N. Belay). 10.5155/eurjchem.11.3.255-260.2019 Received: 06 August 2020 Received in revised form: 27 August 2020 Accepted: 29 August 2020 Published online: 30 September 2020 Printed: 30 September 2020 The structure of the title compound, 4-(dimethylamino)pyridin-1-ium-2,5-dichloro-3,6- dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine water undeca-solvate, C57H87Cl5N12O21, obtained from interaction between chloranilic acid (caH2), and dimethyl aminopyridine (DMAP) has been determined by single crystal X-ray diffraction. The title compound, (DMAPH)5(ca)2.5·(DMAP)·11H2O, crystallized in the triclinic crystal system with space group, P1� (no. 2), a = 13.3824(15) Å, b = 13.4515(17) Å, c = 19.048(2) Å, α = 86.014(4)°, β = 88.821(4)°, γ = 86.367(4)°, V = 3413.3(7) Å3, Z = 2, T = 100(2) K, μ(MoKα) = 0.294 mm-1, Dcalc = 1.414 g/cm3, 59413 reflections measured (3.76° ≤ 2Θ ≤ 56°), 16405 unique (Rint = 0.0517, Rsigma = 0.0589) which were used in all calculations. The final R1 was 0.0460 (I ≥ 2σ(I)) and wR2 was 0.1271 (all data). Using supramolecular chemistry principles, proton donors (chloranilic acid) and acceptor (DMAP) were combined to generate a multicomponent hydrogen-bonded system. Due to the presence of protonated bases (DMAPH+), the dominant interactions are the N+-H···O hydrogen bonds, whereas the negative charges of an acceptor from the chloranilate dianion (ca2-) are delocalized. Additionally, three sets of water clusters in the title compound were identified, namely a cyclic pentamer, a linear, and an acute-shaped trimer water cluster. It was further observed that strong hydrogen bond interactions occurred between the solvated aqua molecule(s) acting as a proton donor and the neutral DMAP acting as a proton acceptor. The crystal packing is further stabilized by O-H···Cl and C-H···Cl weak halogen interactions. The lattice metric strength is further held by observed π-π stacking interactions (centroid-centroid) with inter centroid distances between sets of the DMAPH rings of 3.624(3), 3.642(4), 3.739(3), 3.863(3) and 3.898(3) Å, respectively. Water cluster Chloranilic acid Hydrogen bond Co-crystal structure π-π Stacking interaction 4-Dimethylaminopyridine Cite this: Eur. J. Chem. 2020, 11(3), 255-260 Journal website: www.eurjchem.com 1. Introduction For this study, special attention was paid to choose a strong chelating ligand such as chloranilic acid (caH2) (when deprotonated, a dianionic O,O’-bidentate ligand), which may be used to study the nature and stability of transition metal complexes, especially for hard metals i.e. Nb(V) and Ta(V) [1,2]. Crystal engineers place emphasis on the design and synthesis of preorganized ligands, which can control the structure and hence the properties of these complexes [3,4]. The scientific investigation of multicomponent crystals, involving solvates, salts, and co-crystals, provides the means to change the physicochemical properties of crystals without changing the chemical properties of the molecule of interest. Chloranilic acid and analogues (Scheme 1) represent a subclass of the quinoid compounds which are promising for the synthesis of novel functional materials. caH2 represents a unique multifunctional ligand system because it possesses hydrogen bonding and ionic interaction sites as well as π-π inter- and/or intra-molecular interactions, affording in principle a rich coordination chemistry. It also acts as a strong proton donor and/or acceptor [5,6]. Therefore, the investigation of the initial steps of the solvation process through the study of micro-solvated molecular systems has been an important subject for this field of chemistry [7-9]. This analysis forms part of ongoing research to investigate the mechanism of the reactions of O,O’- and N,O-bidentate ligands with transition metals used in the nuclear industry, such as Hf, Zr, Nb, Ta and some other applications [10-13]. Previ- ously, we have reported on the novel bidentate ligand system, chloranilic acid (caH2), a good proton donor as well as acceptor known to form complexes and co-crystals [14]. The electronic structure of chloranilic acid is susceptible to different degrees of deprotonation and various modes of proton transfer under applied experimental conditions, see Scheme 1. ABSTRACT RESEARCH ARTICLE KEYWORDS http://dx.doi.org/10.5155/eurjchem.11.3.255-260.2019 http://www.eurjchem.com/ http://dx.doi.org/10.5155/eurjchem.11.3.255-260.2019 mailto:alebel.nibret@bdu.edu.et mailto:venterja@ufs.ac.za mailto:alexandero@ufs.ac.za mailto:alebel.nibret@bdu.edu.et http://www.eurjchem.com/ https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.11.3.255-260.2019&domain=pdf&date_stamp=2020-09-30 256 Belay et al. / European Journal of Chemistry 11 (3) (2020) 255-260 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.3.255-260.2019 Table 1. Crystal data and details of the structure refinement for the title compound, (DMAPH)5(ca)2.5·(DMAP)·11H2O. Parameters Compound Empirical formula C57H87Cl5N12O21 Formula weight 1453.64 Temperature (K) 100(2) Crystal system Triclinic Space group P1� a (Å) 13.3824(15) b (Å) 13.4515(17) c (Å) 19.048(2) α (°) 86.014(4) β (°) 88.821(4) γ (°) 86.367(4) Volume (Å3) 3413.3(7) Z 2 ρcalc (g/cm3) 1.414 μ (mm-1) 0.294 F(000) 1532.0 Crystal size (mm3) 0.252 × 0.173 × 0.130 Radiation MoKα (λ = 0.71073 Å) 2Θ range for data collection (°) 3.76 to 56.00 Index ranges -12 ≤ h ≤ 17, -17 ≤ k ≤ 17, -24 ≤ l ≤ 25 Reflections collected 59413 Independent reflections 16405 [Rint = 0.0517, Rsigma = 0.0589] Data/restraints/parameters 16405/0/852 Goodness-of-fit on F2 1.003 Final R indexes [I ≥ 2σ(I)] R1 = 0.0460, wR2 = 0.1052 Final R indexes [all data] R1 = 0.0847, wR2 = 0.1271 Largest diff. peak/hole (e Å-3) 0.38/-0.34 Cl Cl HO O O OH -H+ Cl Cl HO O O O Cl Cl O HO O O -H+ Cl Cl O O O O Cl Cl O O O O Cl Cl O HO O O Cl Cl O O O O Cl Cl O O O O Scheme 1. Dissociation of chloranilic acid (caH2) to the monoanion (caH-) and dianions (ca2-), with resonance structures shown in brackets (pKa1 = 0.76 and pKa2 = 2.58) [15]. Intramolecular electron delocalizations in the mono- and di-anions are also shown. Herein, we report the synthesis and characterization of a new co-crystal structure of the hydrous 1:2 multi-hydrate compound of chloranilic acid with 4-N,N-dimethyl amino- pyridine (DMAP), which was investigated by single-crystal X- ray diffraction at 100(2) K (Table 1). During crystallization, there were four components invol- ved: the 4-(dimethylamino)pyridin-1-ium cations (DMAPH+) which combine in a 2:1 ratio with the 2, 5-dichloro-3, 6-dioxo cyclohexa-1,4-diene-1,4-bis(olate)dianion (trivial name chlora- nilate dianion) (ca2-), one DMAP, and 11 water molecules. Herein, the determination of the structure of the title compound forms part of our systematic investigation concerning π-π stacking interactions, infinite hydrogen bond networks, and halogen bond networks within this interesting bidentate ligand system. 2. Experimental All the chemicals and solvents used were of analytical grade purchased from Sigma-Aldrich, South Africa. Reagents were used as received without further purification. The infrared spectra of the complexes were recorded on a Bruker Tensor 27 Standard System spectrophotometer utilizing a He-Ne laser at 632.6 nm in a range of 4000-600 cm-1. The sample was analysed as solid-state species via Attenuated Total Reflection (ATR) mode infrared spectrophotometry and the data was recorded at room temperature. No solution or KX (where X = I, Cl, Br) solid salt pellets were utilized because halogen interaction was expected from the solution cell and the KX pellet preparation technique. The 1H and 13C NMR spectra were recorded on a Bruker Fourier 300 MHz (1H: 300.18 MHz; 13C: 75.48 MHz) (5 mm, 13C/1H high-resolution NMR probe equipped with Z- gradient coil) nuclear magnetic resonance spectrometer operating at 25 °C. Chemical shifts are reported relative to tetramethylsilane (TMS) as an internal standard using the CD3OD or the solvent peaks, (1H NMR: 3.31 ppm; 13C NMR: 49.1 ppm) peaks. The abbreviations s = singlet and d = doublet are used throughout. Belay et al. / European Journal of Chemistry 11 (3) (2020) 255-260 257 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.3.255-260.2019 Table 2. Selected bond lengths and angles of (DMAPH)5(ca)2.5·(DMAP)·11H2O. Bond lengths (Å) C2A-O1A 1.265(1) C4A-Cl2A 1.732(1) C3A-O2A 1.246(1) C7A-Cl3A 1.742(1) C5A-O3A 1.254(1) C10A-Cl4A 1.735(2) C6A-O4A 1.242(1) C14A-Cl5A 1.736(1) C8A-O5A 1.252(1) C5B-N1B 1.341(1) C9A-O6A 1.255(1) C10B-N4B 1.344(1) C11A-O7A 1.253(1) C19B-N5B 1.338(1) C12A-O8A 1.241(1) C26B-N8B 1.342(1) C13A-O9A 1.251(1) C33B-N10B 1.363(1) C15A-O10A 1.249(1) C40B-N12B 1.341(1) C1A-Cl1A 1.738(1) Bond angles (°) C3B-N2B-C7B 119.83(2) C28B-N7B-C24B 120.09(2) C12B-N3B-C13B 120.17(2) C35B-N9B-C31B 114.85(2) C17B-N6B-C21B 120.25(2) C42B-N11B-C38B 120.52(2) 25 oC / 6 hr 1. MeCN 2. THF+2 NN H3C H3C H O O Cl O O Cl N N CH3 CH3 H NN H3C H3C H 1 23 4 5 6 (DMAPH+) (ca2-) 1 2 34 5 6 O O Cl O O Cl Scheme 2. Representation of ligands (DMAPH+ and ca2-, (2:1)) and the reaction for the formation of [(DMAPH)2(ca)]. 2.1. Synthesis of 4-(dimethylamino)pyridin-1-ium-2,5- dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine (2:1) water undeca-solvate (DMAPH)5(ca)2.5·(DMAP)·11H2O 2, 5-Dichloro-3, 6-dihydroxy-2, 5-cyclohexadiene-1,4-dione (caH2) (0.0750 g, 0.3591 mmol) was dissolved in tetrahydro furan (5 mL), and treated with 4-N,N-dimethylaminopyridine, DMAP (0.0876 g, 0.7172 mmol) in acetonitrile (5 mL) at room temperature. The resulting mixture was stirred for 6 h, and the volatile material was removed in vacuo (Scheme 2). Color: Deep purple powder. Yield: 0.13 g, 78.5%. FT-IR (ATR, ν, cm-1): 1750- 3089 (N-H···O). UV/Vis (CH3OH, λmax, nm, (ε)): 524 (1.755×103 M-1cm-1). 1H NMR (300 MHz, CD3OD, δ, ppm): 8.11 (d, 4H, py), 6.98 (d, 4H, py), 3.26 (s, 12H, CH3). 13C NMR (75 MHz, CD3OD, δ, ppm): 166.47 (C=O; C-OH, caH2), 158.35, 138.58, 107.57 (py) 106.79 (C-Cl, caH2). 2.2. Crystal growth Cuboid crystals of the title compound, 4-(dimethylamino) pyridin-1-ium-2, 5-dichloro-3, 6-dioxocyclohexa-1,4-diene-1,4- bis(olate) 4-dimethylaminopyridine (2:1) water undeca-solvate were grown from a solution of the product in a mixture of acetonitrile and methanol (3:2, v:v) using a slow evaporation technique; the solution was left to stand at 255 K for a few days and crystals suitable for X-ray diffraction were obtained. 2.3. Single-crystal X-ray data collection, reduction, and refinement X-ray intensity data was collected on a Bruker X8 Apex II 4K Kappa CCD area detector diffractometer, equipped with a graphite monochromator and MoKα fine focus sealed tube (λ = 0.71073 Å, T = 100(2) K and 298(2) K) operated at 2.0 kW (50 kV, 40 mA). The initial unit cell determinations and data collection were done using the APEX2 [16] software package. The collected frames were integrated using a narrow-frame integration algorithm and reduced with the Bruker SAINT Plus and XPREP software packages [17], respectively. Analysis of the data showed no significant decay during the data collection. The data was corrected for absorption effects using the multi-scan technique SADABS [18] and the structure was solved by the direct methods package SIR-97 [19] and refined using the WinGX [20] software incorporating SHELXL [21]. The aromatic H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H = 0.93 Å and Uiso(H) = 1.2Ueq(C), for methyl C-H of 0.96 Å (C-H) [Uiso(H) = 1.5 Ueq]. The highest peak (0.38 e.Å-3) is located 0.63 Å from C4B and the deepest hole (-0.33 e.Å-3) is situated 0.26 Å from H11D. All non-hydrogens were refined anisotropically. Hydrogens were placed geometrically at calculated positions on their carrier atoms and refined with a riding model. That is, the hydrogen atoms of 11 solvated water molecules found in the compound were nicely refined and all atoms are best fit the electron density from the Fourier map. Refinement of F2 against all reflections. The weighted R-factor wR2 and goodness-of-fit S are based on F2, the conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2σ (F2) is used only for calculating R factors (gt) 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. Non- hydrogen atoms were refined with anisotropic displacement parameters. The graphics were done using the DIAMOND and OLEX2 [22,23] program with 50% probability displacement ellipsoids for all non-hydrogen atoms. 3. Results and discussion 3.1. Molecular structure To complete the structural characterization, the exact molecular structure of the title compound was obtained by X- ray diffraction analysis. The structure of 4-(dimethylamino) pyridin-1-ium-2, 5-dichloro-3, 6-dioxocyclohexa-1,4-diene-1,4- bis(olate) 4-dimethylpyridine (2:1) water undeca-solvate is shown in Figure 1. The selected bond lengths and angles of (DMAPH)5(ca)2.5·(DMAP)·11H2O are given in Table 2. The title compound, (DMAPH)5(ca)2.5·(DMAP)·11H2O crystallizes in the triclinic space group, P1� , with Z = 2. The asymmetric unit of this compound contains five 4-(dimethylamino)pyridin-1-ium cati- ons (DMAPH+) and one 4-N,N-dimethylaminopyridine (DMAP); two and a half 2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4- bis(olate) dianion (trivial name chloranilate dianion) entities; as well as one half of a chloranilate dianion (ca2-), sitting on an 258 Belay et al. / European Journal of Chemistry 11 (3) (2020) 255-260 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.3.255-260.2019 Table 3. The selected hydrogen bond distances and angles of (DMAPH)5(ca)2.5·(DMAP)·11H2O. D-H···A d(D-H) (Å) d(H···A) (Å) d(D···A) (Å) D-H···A (°) O7W-H7WA···O8W 0.85 1.90 2.753 176(3) O1-H1A···O10W 0.85 1.86 2.695 170 O1-H1B···O7A 0.85 1.97 2.822 175 O7W-H7WB···O5A 0.85 1.92 2.767 176(2) N2B-H2B···O1A 0.94 2.04 2.793 135 N2B-H2B···O2A 0.94 2.01 2.821 143 O5W-H5WA···O1A 0.85 1.99 2.842 171 O5W-H5WB···O6W 0.85 1.86 2.707 173(2) O4W-H4WA···O3W 0.85 1.91 2.755 172(3) O4W-H4WB···O5W 0.85 1.95 2.783 168 N6B-H6B···O5A 0.85 2.32 2.964 133 N6B-H6B···O6A 0.85 1.96 2.734 151 O6W-H6WA···Cl5Ai 0.85 2.81 3.463 136 O6W-H6WA···O10Ai 0.85 2.13 2.905 152 O6W-H6WB···O7W 0.85 1.89 2.730 1.73 O1W-H1WA···N9B 0.85 2.06 2.898 167 O1W-H1WB···Cl2Aii 0.85 2.76 3.263 119 O1W-H1WB···O2Aii 0.85 2.23 3.044 161 O10W-H10A···O4Aiii 0.85 2.08 2.877 157 O10W-H10B···O11Wiv 0.85 1.87 2.710 168 O8W-H8WA···O4W 0.85 1.93 2.774 172 N11B-H11B···O9Av 0.89 2.20 2.913 137 N11B-H11B···O10A 0.89 1.99 2.758 144 O11W-H11C···O9A 0.85 1.97 2.812 172(3) O11W-H11D···O1 0.85 1.88 2.715 167 O8W-H8WB···O3Aii 0.85 2.02 2.859 169 O2W-H2WA···Cl4Avi 0.85 2.82 2.821 121 O2W-H2WA···O6Avi 0.85 2.01 2.013 164 O2W-H2WB···O1W 0.85 2.03 2.029 172 O3W-H3WA···O1Avii 0.85 2.18 2.964 154 O3W-H3WB···O2W 0.85 1.89 2.729 170 N7B-H7BA···O7A 0.94 2.03 2.821 141 N7B-H7BA···O8A 0.94 2.05 2.815 138 N3B-H3BA···O3A 0.92 2.18 2.902 135(2) N3B-H3BA···O4A 0.92 1.99 2.789 145 C12B-H12B···O7Wviii 0.93 2.57 3.188 124 C21B-H21B···O8W 0.93 2.61 3.257 128 C29B-H29B···Cl3Aix 0.96 2.98 3.929 170 C37B-H37A···Cl1Ax 0.96 2.92 3.718 141(2) Symmetry code: (i) -x +1, -y +1, -z, (ii) x+1, y, z, (iii) x, y +1, z, (iv) -x +1, -y +1, -z, (v) -x, -y +2, -z, (vi) -x +2, -y +1, -z +1, (vii) -x +2, -y, -z +1, (viii) x -1, y, z, (ix) x +1, y, z +1, (x) -x, -y +1, z -1. Figure 1. The molecular structure of (DMAPH)5(ca)2.5·(DMAP)·11H2O. Thermal ellipsoids are drawn at 50% probability displacements. The atom numbering is shown and water molecules have been omitted for clarity. inversion center and its symmetry generated counterparts are linked by the network of extended hydrogen bonds to the 4- (dimethylamino)pyridin-1-ium cations (DMAPH) and solvated aqua cluster molecules. There are five protonated DMAPH+ moieties (out of six) inducing a positive charge population in the unit cell which effectively balances with the ligand co- crystal (cf. Figures 1-3). Therefore, due to the presence of protonated bases (DMAPH+), the dominant interactions are the N+-H···O hydrogen bonds, whereas the negative charges of an acceptor from the chloranilate dianion (ca2-) are delocalized. It was found that the guest donor, DMAP, co-crystallizes with chloranilic acid (caH2) through hydrogen bonding between protonated DMAPH+ and the dianion of chloranilic acid acting as an acceptor to the nitrogen donor group of the DMAP, via an infinite network of N-H···O hydrogen-bonds (cf. Figure 2A). Additionally, we found a strong hydrogen bond interaction between the solvated aqua molecules acting as a proton donor and the neutral DMAP (unprotonated DMAP) acting as a proton Belay et al. / European Journal of Chemistry 11 (3) (2020) 255-260 259 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.3.255-260.2019 (A) (B) Figure 2. (A) Molecular structure of (DMAPH)5(ca)2.5·(DMAP)·11H2O showing the head-to-tail network of infinite intermolecular interactions, with water molecules omitted. (B) Water clusters shown with respective hydrogen interactions with other atoms omitted for clarity. Non-hydrogen atoms are drawn at 50% probability displacement ellipsoids are used. The red dashed lines indicate O-H···O, O-H···N, N-H···O, C-H···O, and O-H···Cl, C-H···Cl, hydrogen and halogen interactions, respectively, as well as cyclic pentamer (V) and linear (IV) and acute shaped (VI) trimer water clusters. The roman numerical of I, II, and III indicates half a ligand with only one charge, protonated DMAPH and neutral DMAP, respectively. Figure 3. Molecular structure of (DMAPH)5(ca)2.5·(DMAP)·11H2O showing the head to tail network of infinite intermolecular interactions. The blue dashed lines indicate the π-π stacking interaction [centroid-centroid = 3.624(3) Å (i), 3.642(4), 3.739(3) Å (ii), 3.863(3) and 3.898(3) Å] distance between two DMAPH+ rings on N6B-C21B and symmetrically generated N6B-C21B, N2B-C7B and N6B-C21B, N2B-C7B and N11B-C42B as well as N3B-C13B and symmetrically generated N3B-C13B, N7B-C28B and N3B-C13B, N11B-C42B [Symmetry codes: (i) -x, 1-y, 1-z, (ii) 1-x, 1-y, 1-z]. H atoms are omitted for clarity. acceptor; O-H···O, O-H···N, N-H···O, and C-H···O hydrogen- bonds and O-H···Cl and C-H···Cl halogen bonds (cf. the Figure 2A, and 2B and Table 3). This generates infinite hydrogen- and halogen bonding networks. Hydrogen and halogen bonds are used as “supramolecular glue” in the construction of these molecular architectures and water solvent molecules as connectors and/or stabilizers. The crystal packing is reinforced by the formation of an extensive network of halogen and hydrogen bonds as with similar work reported earlier. 3.2. Supramolecular features The title compound is stabilized further by a cluster of eleven aqua units. This generates an infinite network of hydrogen bonds which can be characterized as strong and weak hydrogen bond interactions. Different v-shaped bifurcated strong hydrogen bonds are present, which show H3Ba bonded to O3A and O4A, H7Ba bonded to O7A and O8A, H2B bonded to O1A and O2A between protonated DMAPH+ cations and the chloranilate dianion (ca2-) molecules. We identified three sets of water clusters in the title compound, namely a cyclic pentamer (O4W-O5W-O6W-O7W-O8W), a linear trimer (O1W- O2W-O3W) and an acute-shaped trimer (O10W-O1-O11W) water cluster interactions (cf. Figure 2B; V, IV and VI, respectively). The measured angles of the linear trimer and the acute-shaped trimer water clusters are 141.38(1) and 110.99(1)°, respectively. Resulting from the cyclic pentamer water cluster interactions, five different angles between O4W- O5W-O6W, O5W-O6W-O7W, O6W-O7W-O8W, and O7W-O8W- O4W can be observed and are 99.64(9), 108.95(9), 107.92(1), 100.53(9) and 114.26(9)°, respectively. These molecules of water are positioned midway between the protonated DMAPH+ entities and the chloranilate dianions (ca2-), which are each involved in the cyclic pentamer, linear trimer, and acute-shaped trimer, respectively. Such network structures stabilize the crystal lattice. It is especially interesting to note that the water 260 Belay et al. / European Journal of Chemistry 11 (3) (2020) 255-260 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.3.255-260.2019 cluster units are strongly held together by O-H···O and O-H···N interactions with the O···O distance ranging from 2.695(3) to 5.287(5) Å and the O…O···O angle ranging from 99.64(9) to 141.38(1)°. The infinite water clusters are linked by a strong O- H···Cl hydrogen bond. Inter- and intramolecular hydrogen- bonds and halogen-bonds were observed in the range of (i) O- H···O (1.85(2)-1.97(2) Å, (ii) O-H···N (2.06 Å), (iii) N-H···O (1.96(2)-2.32(2) Å, (iv) C-H···O (2.57(3)-2.60(3) Å, and (v) O- H···Cl (2.76(2)-2.81(2) Å, as well as (vi) C-H···Cl (2.92(3)- 2.98(3) Å, respectively (cf. Figure 2). Therefore, the hydrogen bond N+-H···O with a delocalized negative charge of an acceptor from the chloranilate dianion characterizes these systems. However, C-H···Cl interactions involving the chloranilic anion skeleton are very rare (Table 3). In addition to the intermolecular interactions described, the molecules are linked together by symmetry-related π-π stacking interactions (centroid-centroid), with distances between respective sets of DMAPH+ rings 3.624(3), 3.642(4), 3.739(3), 3.863(3) Å and 3.898(3) Å (cf. Figure 3), formed by the DMAPH+ rings labeled as Cg3-Cg3, Cg1-Cg3, Cg1-Cg5, Cg4-Cg2 and Cg2-Cg5, respectively; where Cg1 (N2B-C7B), Cg2 (N3B-C13B), Cg3 (N6B-C21B), Cg4 (N7B-C28B) and Cg5 (N11B- C42B). 4. Conclusions The co-crystalline compound, 4-(dimethylamino)pyridin-1- ium-2, 5-dichloro-3, 6-dioxocyclohexa-1, 4-diene-1, 4-bis(olate) 4-dimethylaminopyridine water undeca-solvate was success- fully synthesized and its structure confirmed by single crystal X-ray diffraction and spectroscopic techniques (FT-IR, 1H and 13C NMR). The molecular structure of this new compound, as determined by single-crystal X-ray diffraction, is stabilized by a cluster of eleven aqua units. This generates an infinite network of hydrogen and halogen bonds which can be characterized as strong and weak interactions. Acknowledgment We acknowledge the University of the Free State, Department of Chemistry, South Africa’s National Research Foundation (NRF) and the World Academy of Science (TWAS) (UIDs 99782) for their financial support. Thanks are also due to Prof. Andreas Roodt (Head of The Inorganic Research Group), his financial support, and helpful discussions as well as Dr. Linette Twigge for the NMR data analysis. Many thanks further go to the crystallographic data collection team at the University of the Free State, South Africa. Supporting information CCDC-2021605 contains the supplementary crystallo- graphic data for this paper. These data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/, or by e- mailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-336033. Disclosure statement Conflict of interests: The authors declare that they have no conflict of interest. Author contributions: All authors contributed equally to this work. Ethical approval: All ethical guidelines have been adhered. Sample availability: Samples of the compounds are available from the author. Funding We acknowledge the University of the Free State, Department of Chemistry, South Africa’s National Research Foundation (NRF) and the World Academy of Science (TWAS) (UIDs 99782) for their financial support. ORCID Alebel Nibret Belay http://orcid.org/0000-0003-4175-5656 Johan Andries Venter http://orcid.org/0000-0002-3015-5252 Orbett Teboho Alexander http://orcid.org/0000-0003-4926-8342 References [1]. Kawaguchi, H.; Matsuo, T. J. Organomet. Chem. 2004, 689, 4228-4243. [2]. Bruijnincx, P.; Viciano-Chumillas, M.; Lutz, M.; Spek, A.; Reedijk, J.; van Koten, G.; Klein Gebbink, R. Chem. Eur. J. 2008, 14(18), 5567-5576. [3]. Elhabiri, M.; Haracek, J.; Bünzli, J.; Gary, A. Eur. J. Inorg. Chem. 2004, 51- 62. [4]. Kim, J.; Hong, M.; Ahn J.; Lee, M. Angew. Chem. Int. 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The full terms of this license are available at http://www.eurjchem.com/index.php/eurjchem/pages/view/terms and incorporate the Creative Commons Attribution-Non Commercial (CC BY NC) (International, v4.0) License (http://creativecommons.org/licenses/by-nc/4.0). By accessing the work, you hereby accept the Terms. This is an open access article distributed under the terms and conditions of the CC BY NC License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited without any further permission from Atlanta Publishing House LLC (European Journal of Chemistry). No use, distribution or reproduction is permitted which does not comply with these terms. Permissions for commercial use of this work beyond the scope of the License (http://www.eurjchem.com/index.php/eurjchem/pages/view/terms) are administered by Atlanta Publishing House LLC (European Journal of Chemistry). https://www.ccdc.cam.ac.uk/structures/ mailto:data_request@ccdc.cam.ac.uk http://orcid.org/0000-0003-4175-5656 http://orcid.org/0000-0002-3015-5252 http://orcid.org/0000-0003-4926-8342 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms http://creativecommons.org/licenses/by-nc/4.0 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms 1. Introduction 2. Experimental 2.1. Synthesis of 4-(dimethylamino)pyridin-1-ium-2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine (2:1) water undeca-solvate (DMAPH)5(ca)2.5 (DMAP) 11H2O 2.2. Crystal growth 2.3. Single-crystal X-ray data collection, reduction, and refinement 3. Results and discussion 3.1. Molecular structure 3.2. Supramolecular features 4. Conclusions Acknowledgment Supporting information Disclosure statement Funding ORCID References PrintField10: PrintField11: PrintField12: PrintField13: PrintField14: PrintField15: PrintField20: PrintField21: PrintField22: PrintField23: PrintField24: PrintField25: