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Article

Synthesis, X-ray Structure of Two Hexa-Coordinated Ni(II) Complexes with s-Triazine Hydrazine Schiff Base Ligand

by
Eman M. Fathalla
1,*,
Morsy A. M. Abu-Youssef
1,*,
Mona M. Sharaf
2,
Ayman El-Faham
1,
Assem Barakat
3,
Matti Haukka
4 and
Saied M. Soliman
1,*
1
Department of Chemistry, Faculty of Science, Alexandria University, P.O. Box 426, Ibrahimia, Alexandria 21321, Egypt
2
Protein Research Department, Genetic Engineering and Biotechnology Research Institute, City of Scientific Research and Technological Applications, Alexandria, P.O. Box 21933, Egypt
3
Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
4
Department of Chemistry, University of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä, Finland
*
Authors to whom correspondence should be addressed.
Inorganics 2023, 11(5), 222; https://doi.org/10.3390/inorganics11050222
Submission received: 9 May 2023 / Revised: 19 May 2023 / Accepted: 19 May 2023 / Published: 21 May 2023
(This article belongs to the Special Issue 10th Anniversary of Inorganics: Coordination Chemistry)
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Versions Notes

Abstract

:
The hydrazine s-triazine ligand (E)-4,4’-(6-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)-1,3,5-triazine-2,4-diyl)dimorpholine (DMPT) was used to synthesize two new Ni(II) complexes via a self-assembly technique. The two complexes were synthesized by a one-pot synthesis strategy and characterized by elemental analysis, FTIR and single-crystal X-ray diffraction analysis to be [Ni(DMPT)(H2O)3](NO3)2.3H2O (1) and [Ni(DMPT)(H2O)3](NO3)2.H2O (2). The structures of both complexes were very similar regarding the coordination sphere and counter anions, but differ only in the number of the crystal water molecules. In the case of complex 1, there are three water molecules instead of one H2O molecule as in complex 2. In the two complexes, the DMPT ligand acts as a neutral tridentate NNN-chelate via three Ni–N coordination interactions. The coordination sphere of the Ni(II) ion is completed by three water molecules. As a result, the two complexes exhibit distorted octahedral geometry. The Hirshfeld surfaces around each entity in both complexes have been computed. Subsequently, their corresponding intermolecular interactions were quantified separately. Because the number of crystal water molecules is different in both complexes, their monomeric units are connected differently in their crystal structures where the crystal water molecules act as both hydrogen bond donor and acceptor. The polar O…H interactions are the most dominant in all entities of both complexes. As a result, strong O…H interactions are the driving force in the crystal packing of both complexes, and this is attributed to the presence of the nitrate anions and water molecules. The antimicrobial activity of the free ligand and complex 1 were determined against two selected fungal species, Gram-negative and Gram-positive bacterial strains. The free ligand was found to be inactive against all microbial species. On the other hand, the Ni(II) complex 1 was found active against the Gram-positive bacterial species Bacillus subtilis and also the Gram-negative bacterial species Escherichia coli. The respective inhibition zone diameter of the Ni(II) complex was 12 and 11 mm, respectively.

1. Introduction

Schiff base ligands are an important class of organic chelating ligands which have been widely used for the synthesis of a large number of metal complexes. Schiff bases have become a significant class of ligands that are widely used in coordination chemistry and are considered as privileged multitopic ligands. There is a wide range of potential uses for Schiff bases and their metal complexes, including luminescent probes [1], catalysis [2,3,4,5], dye and polymer industry, analytical chemistry, agriculture [6,7,8], magneto-structural chemistry, food industry, agrochemical and biological fields [9,10], and also as antitumor, antifungal and antimicrobial agents [11,12,13,14,15,16,17,18,19,20,21,22]. Hydrazones Schiff bases are among these important chelating ligands which have drawn particular interest from researchers because of their known chelating ability beside their structural flexibility, which can add stiffness to the skeletal structure of the synthesized metal complexes [23,24,25,26,27]. In addition, the nitrogen–nitrogen covalent bond that exists in the azomethine group of hydrazones increases its ability to synthesize stable metal complexes. Additionally, hydrazones and related compounds play a significant part in enhancing the toxicity and selectivity aspects of some anticancer agents by building drug carrier systems using proper carrier proteins [28].
On the other hand, the majority of the first row of transition metals and their complexes have biological necessities and a variety of known bioactivities. One of these transition metals is nickel, which exists in the nickel (II) form as the most stable oxidation state [29,30,31]. Ni(II) complexes are one of these crucial transition metal complexes which have different coordination geometries, including tetrahedral [32], square planar [32,33], trigonal bipyramidal [34] and octahedral [35], where the square planar and octahedral geometries are the most prevalent. Each nickel (II) complex with a particular ligand has unique chemical and physical characteristics, which makes their investigation both fascinating and challenging. Its significance in bioinorganic chemistry expands with the identification of the nickel enzyme, urease [36,37]. The ability of nickel complexes to permeate into the microbial cells and impact the enzyme activity has led to the discovery of numerous nickel complexes with broad-spectrum efficacy against many pathogens [38,39,40,41,42,43,44].
In our previous work, the X-ray structure and biological evaluations of the three metal complexes, [Mn(DMPT)Cl2], [Cu(DMPT)Cl2]. H2O and [Cu(DMPT)(NO3)2] were presented. In continuation to our previous study, the present work aims to synthesize two novel Ni(II) complexes using the hydrazine s-triazine ligand DMPT [45] shown in Figure 1. The synthesized complexes were characterized by different analytical techniques such as FTIR, single-crystal X-ray diffraction (SCXRD) and elemental analysis. Hirshfeld surface analysis is performed to describe and quantify the intermolecular interactions in their crystal structures. Additionally, an assessment of their antibacterial activity against six harmful microorganisms was performed.

2. Results and Discussion

2.1. Synthesis and Characterizations

The self-assembly of the organic ligand (DMPT) [45] and Ni(NO3)2.6H2O in ethanol lead to the formation of two new crystalline Ni(II) complexes in the same pot (Scheme 1). The two complexes 1 and 2 were distinguished very clearly as green and turquoise crystals, respectively. Additionally, both complexes are separated easily from the reaction pot as the green crystals of 1 were formed on the glass beaker’s walls, while turquoise crystals of 2 were collected from the bottom of the beaker. FTIR data of the ligand DMPT and its two complexes were compared in Figure S1 (Supplementary Data). The FTIR spectra of DMPT showed the ν(C=N) modes at 1523 and 1492 cm−1. These bands are shifted to higher wavenumbers of 1593 and 1572 cm−1 in the case of 1, while appeared as a split band at 1575 and 1607 cm−1 in the case of 2, indicating the coordination of the Ni(II) ion in the two complexes via the nitrogen atoms of azomethine, triazine and pyridine moieties of DMPT. The broad band at 3382 cm−1 in complex 1 and 3327 cm−1 in complex 2 confirms the presence of water molecules in the two complexes. Additionally, the (N–O) stretches of the nitrate group in the two complexes appeared at the same frequency at 1385 cm−1.

2.2. X-ray Structure Description

The molecular structure of complex 1 was confirmed by crystal X-ray diffraction to be [Ni(DMPT)(H2O)3](NO3)2.3H2O. The crystal system of 1 is monoclinic and the space group is P21/n. The unit cell parameters are a = 11.4900(2) Å, b = 17.6794(3) Å, c = 14.1294(2) Å and β = 90.110(1)°. In the unit cell, there are four molecules of the abovementioned formula and its volume is 2870.19(8) Å3, while the calculated density is 1.563 mg/m3. The asymmetric formula is one [Ni(DMPT)(H2O)3](NO3)2.3H2O molecule (Figure 2).
The inner sphere of this complex comprised a hexa-coordinated Ni(II) ion with one DMPT and three water molecules, while the outer sphere composed of two nitrate counter ions and three crystal water molecules. It is clear from Figure 2 that the DMPT ligand acts as a neutral tridentate NNN-chelate via three Ni–N coordination interactions which are the Ni(1)–N(2), Ni(1)–N(1) and Ni(1)–N(4) bonds. Their respective Ni–N distances are 2.0031(12), 2.1002(13) and 2.2608(12) Å, respectively. It is clear that the Ni–N(hydrazone) is the shortest interaction. In contrast, the Ni–N(s-triazine) is the longest Ni–N bond. The chelate angles N(2)–Ni(1)–N(1) and N(2)–Ni(1)–N(4) are determined to be 77.93(5) and 76.47(4)°, respectively, while the trans-N(1)–Ni(1)–N(4) is determined to be 154.38(5)°. On the other hand, the coordination sphere of the Ni(II) ion is completed by three water molecules. The equatorial Ni1–O2 bond, which is trans to the Ni–N(hydrazone) bond, is the shortest interaction with the water molecules. The two axial Ni1–O3 and Ni1–O4 bonds are slightly longer than the equatorial Ni–O bond. The corresponding Ni–O distances are 2.0466(12) and 2.0764(12) Å, respectively (Table 1). The distorted octahedron comprised the four atoms N1, N2, N4 and O2 as corners for the distorted square as a basal plane, while the two oxygens O1 and O3 are apical.
As clearly seen from Figure 2, the solid state structure of complex 1 comprised a large number of coordinated and hydration water molecules which participate significantly with the nitrate counter anions in the molecular packing of this monomeric complex. The important hydrogen bond contacts are shown in Figure 3A and the corresponding geometric parameters are depicted in Table 2. The nitrate counter ions as hydrogen bond acceptor connect the monomeric complex units via short hydrogen bonding interactions with the free and coordinated water molecules. In this supramolecular structure, the free water molecules act as both hydrogen bond donors as well as hydrogen bond acceptors while the coordinated H2O molecules are only hydrogen bond donors. In addition, the oxygen atom of the morpholine substituents and one of the free triazine N-atoms (N5) participated in the molecular packing of complex 1 as hydrogen bond acceptors (Figure 3B).
On the other hand, the structure of complex 2 was found very similar to that for 1 regarding the coordination sphere and counter anions but differ only in the number of the crystal water molecules. In case of complex 2, there is one water molecule instead of three H2O molecules in complex 1. Additionally, this complex crystallized in the less symmetric triclinic crystal system and P-1 space group. The unit cell parameters are a = 8.3135(2) Å, b = 10.9175(2) Å, c = 15.7611(4) Å, α = 71.119(1)°, β = 80.188(1)° and γ = 84.58(1)°. In the unit cell there are two molecules of the asymmetric formula [Ni(DMPT)(H2O)3](NO3)2.H2O and its volume is 1332.20(5) Å3 while the calculated density is 1.594 mg/m3 (Figure 4).
The structure of the coordination sphere of complex 2 comprised one tridentate DMPT molecule and three water molecules. Similar to complex 1, the Ni–N(hydrazone) bond is the shortest Ni–N interaction with the organic ligand compared to the Ni–N(s-triazine) and Ni–N(pyridine) bonds. The respective Ni–N distances are 2.0079(18) Å, 2.1031(18) and 2.1907(18) Å. The N(2)–Ni(1)–N(1) and N(2)–Ni(1)–N(8) angles are 78.11(7) and 77.95(7)°, respectively, while the trans N(1)–Ni(1)–N(8) is 156.03(7)°. The hexa-coordination environment of the Ni(II) is completed by the three Ni(1)–O(2), Ni(1)–O(3) and Ni(1)–O(1) bonds. The respective Ni–O distances are 2.0378(17), 2.0409(17) and 2.0652(16) Å, respectively (Table 3). Additionally, the equatorial Ni1–O2 bond is the shortest Ni–O bonds. The results of these geometric parameters are similar to those for complex 1 and the NiN3O3 coordination environment of the Ni(II) ion could be described as a distorted octahedron.
The supramolecular structure of complex 2 is controlled only by a significant number of O…H interactions (Table 4), which are considered as another major difference between the two complexes. In this case, there is one crystal water molecule, and hence, the monomeric units are connected differently in the crystal structure compared to 1. While the hydrazone NH group participated in the hydrogen bond network of 1 by only the N(3)–H(3)…O(8) hydrogen bond, there are two significant N–H…O hydrogen bonds in complex 2, which are the N(3)–H(3)...O(6) and N(3)–H(3)...O(7). Additionally, the crystal water molecule is both a hydrogen bond donor and acceptor in this complex via O(3)–H(3A)...O(12), O(12)–H(12C)...O(11) and O(12)–H(12D)...O(9) hydrogen bonds (Figure 5A). In addition, the two morpholine moieties and the nitrate counter anions participated in the hydrogen bonding interactions as hydrogen bond acceptors via their oxygen atoms. A view of the packing scheme is shown in Figure 5B.
In the studied complexes, we noted the presence of another common intermolecular interaction between the nitrate anion and the π-system of the organic ligand (DMPT). It is clearly seen from Figure 6 that the presence of short C6…O9 (3.108 Å) and C8…O6 (3.208 Å) contacts revealed this observation very well.

2.3. Hirshfeld Analysis

The results of the X-ray crystal structure analysis were accurately mirrored by the Hirshfeld surface analysis, which also provided a novel visual way to understand intermolecular interactions via the colors of various regions [46,47]. The Hirshfeld (HF) surfaces and the 2D fingerprint (FP) plots of complexes 1 and 2 were analyzed. As shown from X-ray studies, the asymmetric unit in complex 1 consists of one [Ni(DMPT)(H2O)3]2+ cationic complex unit as the inner sphere and two nitrate anions in addition to three crystallized water molecules in the outer sphere. On the other hand, there is only one water molecule present in an asymmetric unit of complex 2. Hence, the Hirshfeld surfaces around each entity in both complexes have been computed (Figure 7). Using fingerprint plot, it is possible to decompose all intermolecular interactions and the percentage of all these contacts could be easily obtained. Subsequently, their corresponding intermolecular interactions were quantified separately in Figure 8.
According to the aforementioned data, both complexes (1 and 2) are very close in their intermolecular interactions. It is clear that the interactions involving hydrogen atoms are the most dominant, mainly the hydrogenic H…H and the polar O…H interactions in all entities, except nitrate anions, in which the O…H interaction is the only most prevalent one (Figure 8). This suggests that strong O…H interactions is the driving force in the formation of the crystal packing in both complexes, and this is attributed to the presence of the nitrate anions and water molecules.
For the [Ni(DMPT)(H2O)3]2+ cation (E1 and E1` in complexes 1 and 2, respectively), the most significant contact is the O…H interaction, which contributed by 35.1 and 33.5% in E1 and E1`, respectively. Additionally, the H…H, N…H and C…H contacts contributed 42.3, 7.8 and 11.1% in E1, respectively. The corresponding values in E1` are 43.3, 8.5 and 11.9%, respectively. These short interactions appeared as sharp spikes in the FP plots (Figure 9), indicating strong interactions between the [Ni(DMPT)(H2O)3]2+ and the neighboring units (Figure 10 and Table 5). In the entity E1 of complex 1, the shortest O…H interactions are O13…H2B (1.710Å), O12…H2A (1.749 Å) and O14…H1A (1.656 Ǻ). On the other hand, the O12…H3A (1.713 Å) and O4…H1A (1.749 Å) in the E1` entity of complex 2 are the most significant O…H contact. A summary of the significant short interactions around the [Ni(DMPT)(H2O)3]2+ in both complexes is shown in Table 5.
For the outer-sphere nitrate anions (E2 and E3 in 1, while E2`and E3` in 2), the O...H contact is the most dominant, which contributed 92.5% (E2), 86.6% (E3), 92.3% (E2`) and 89.6% (E3`) of the total HF surface area (Figure 11). The shortest contacts which appeared in the dnorm maps as red spots are O7…H14B (1.829Å) and O11…H3B (1.779 Å) in complex 1, while O10…H2B (1.794 Å) and O6…H3B (1.784 Å) in complex 2 (Table 5).
For the water of crystallization (E4:E6 in 1 and E4` in 2), the O…H and H…H interactions represent almost all the 2D fingerprint area (Figure S2, Supplementary Data). The decomposed dnorm maps exemplify relatively short O…H and H…H interactions that appear as dark red spots (Figure 12). The shortest O…H contacts in 1 are O13…H2B (1.710 Å), O14…H1A (1.656 Å) and O12…H2A (1.749 Å), while O12…H3A (1.713 Å) in 2. For the H…H interaction, the shortest contacts are H13D…H2B (2.152Å), H14A…H1A (2.118 Å) and H12D…H3A (2.151Å), as shown in Table 5.

2.4. Antimicrobial Assay

The antimicrobial activity of the free ligand and complex 1 were determined against selected Gram-positive, Gram-negative bacterial strains and two fungal species. The results of the inhibition zone diameters were collected in Table 6. The results indicated that both the ligand and its Ni(II) complex are inactive toward both fungal species: A. fumigatus and C. albicans. On the other hand, the Ni(II) complex was found active against the Gram-positive bacterial species B. subtilis, but not active against S.aureus. The inhibition zone diameter of the Ni(II) complex is 12 mm and the minimum inhibitory concentration is 1250 μg/mL. Additionally, the Ni(II) complex is active against the Gram-negative bacterial species E. coli, but is found inactive against P. vulgaris. The inhibition zone diameter of the Ni(II) complex is 11 mm and the minimum inhibitory concentration is 1250 μg/mL. Interestingly, the free ligand was found inactive against both Gram-positive and Gram-negative bacteria species. The higher antibacterial activity of the Ni(II) complex against B. subtilis and E. coli compared to the free Schiff base ligand (DMPT) might be attributed to the ability of the metal chelates to inhibit the respiration mechanism of the microbial organisms, which make them unable to manufacture their own proteins, preventing the organism from growing further [48]. On the other hand, the studied Ni(II) complex has a lower antimicrobial activity than the gentamycin as a positive control. It is worth to note that the Cu(II) and Mn(II) complexes of DMPT ligand [45] are better antimicrobial agents and have broader antibacterial spectra than the corresponding Ni(II) complex.

3. Materials and Methods

3.1. Physical Measurements

All the chemicals were bought from Sigma-Aldrich and used without additional purifications. CHN analyses were carried out using a PerkinElmer 2400 Elemental Analyzer. The amount of Ni was determined with the aid of a Shimadzu atomic absorption spectrophotometer (AA-7000 series, Shimadzu, Ltd., Tokyo, Japan). FTIR spectra were recorded at the Central Lab, Faculty of Science, Alexandria University, using a Bruker Tensor 37 FTIR spectrophotometer (Bruker Company, Berlin, Germany) in KBr pellets at 4000–400 cm−1

3.2. Preparation of DMPT

3.2.1. Synthesis of Ligand (DMPT) [45]

s-Triazine hydrazine derivative (2 mmol, 563 mg) mixed with 2-acetylpyridine (2 mmol, 242 mg) in ethanol (20 mL in the presence of a drop of acetic acid and then refluxed overnight; the reaction was monitored by (TLC 2% MeOH/CHCl3 then 50:50 EtOAc/n-hexane). After evaporation 1/3 of the solvent the desired product was precipitated as white powered materials and then filtered and washed with a small quantity of ethanol to afford the requisite ligand (DMPT).
Ligand (DMPT): m.p: 230 °C; 1H NMR (400 MHz, CDCl3) δ 8.54 (d, J = 4.6 Hz, 1H), 8.20 (d, J = 8.1 Hz, 1H), 8.08 (s, 1H), 7.67 (t, J = 8.0 Hz, 1H), 7.20 (dd, J = 7.3, 4.9 Hz, 1H), 3.81 (q, J = 8.2, 6.4 Hz, 8H), 3.72 (t, J = 4.8 Hz, 8H), 2.40 (s, 3H) ppm. 13C NMR (101 MHz, CDCl3) δ 165.36, 164.61, 155.63, 148.48, 147.51, 139.00, 136.27, 123.68, 119.89, 66.95, 43.75 ppm. IR (KBr, cm−1): 3442 ν (N–H), 2962, 2895, 2855 ν(C–H), 1606, 1584 ν(C=N), 1523, 1492 ν(C=C), 1256 ν(C–N).

3.2.2. Synthesis of Complexes [Ni(DMPT)(H2O)3](NO3)2.3H2O (1) and [Ni(DMPT)(H2O)3](NO3)2.H2O (2)

Equimolar amounts of 15 mL ethanolic solution of Ni(NO3)2.6H2O (29.1 mg, 0.1 mmol) and 15 mL ethanolic solution of organic ligand DMPT (38.4 mg, 0.1 mmol) were added into one pot. The resulting clear green solution was allowed to evaporate slowly and crystallize at room temperature. After one week, green crystals of complex 1 were collected from the walls of the glass beaker, whereas turquoise crystals of 2 were collected from the bottom of the beaker. The crystals were left for drying and used for single-crystal X-ray diffraction measurement.
Complex 1, Anal. Calc. C18H36N10NiO14: C, 32.02; H, 5.37; N, 20.74; Ni, 8.69%. Found: C, 31.61; H, 5.26; N, 20.63; Ni, 8.47%. IR (KBr, cm−1): 3382 ν(O–H) water, 3246 ν (N–H), 2977, 2930, 2860 ν(C–H), 1593, 1572 ν(C=N), 1509 ν(C=C), 1385 ν(N–O),1260 ν(C–N), 785 ρr (H2O), 641ρw (H2O).
Complex 2, Anal. Calc. C18H32N10NiO12: C, 33.82; H, 5.05; N, 21.91; Ni, 9.18%. Found: C, 33.63; H, 4.98; N, 21.75; Ni, 9.09%. IR (KBr, cm−1): 3327 ν(O–H)water, 3247 ν (N–H), 2959, 2929, 2864 ν(C–H), 1607, 1575 ν(C=N), 1509 ν(C=C), 1385 ν(N–O),1259 ν(C–N), 809 ρr (H2O), 634 ρw (H2O).

3.3. X-ray Crystallography

The experimental measurements [49,50,51,52,53,54] for the complexes 1 and 2 are provided in the Supplementary Materials. Crystal data of complexes 1 and 2 are presented in Table S1.

3.4. Hirshfeld Analysis

The Crystal Explorer Ver. 3.1 program [55] was used to perform this analysis.

3.5. Antimicrobial Assay

Using the procedure mentioned in Method S1 (Supplementary Data), the antibacterial activities [56] of DMPT and complexes 1 and 2 toward several microbes were determined.

4. Conclusions

Using analytical and spectroscopic techniques, the structures of the recently synthesized Ni(II) complexes were determined as [Ni(DMPT)(H2O)3](NO3)2.3H2O (1) and [Ni(DMPT)(H2O)3](NO3)2.H2O (2). The structures of complexes 1 and 2 were very similar regarding the coordination sphere and counter anions, but differ only in the number of the crystal water molecules. The inner spheres of both complexes comprised a hexa-coordinated Ni(II) ion with one DMPT and three water molecules with a distorted octahedral coordination environment, while the outer sphere composed of two nitrate counter ions in addition to three crystal water molecules in complex 1 compared to only one crystallized water molecule in complex 2. The DMPT ligand acts as a neutral tridentate NNN-chelate via three Ni–N coordination interactions. The supramolecular structures of 1 and 2 were described on the basis of a Hirshfeld analysis along side an X-ray single-crystal diffraction. The Hirshfeld surfaces around each entity in both complexes have been computed. The hydrogenic H…H and the polar O…H interactions are the most dominant. Additionally, the presence of short C6...O9 (3.108 Å) and C8...O6 (3.208 Å) contacts in complexes 1 and 2, respectively, revealed the presence of anion–π stacking interactions. The organic ligands have no antimicrobial activity against the studied microbes at the applied concentration. In contrast, the Ni(II) complex 1 showed antimicrobial activity against Bacillus subtilis and Escherichia coli.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/inorganics11050222/s1, X-Ray structure determinations; Table S1. Crystal Data; Evaluation of antimicrobial activity [56]; Figure S1. FTIR spectra of complexes 1 and 2 compared to the free ligand DMPT; Figure S2. The 2D fingerprint plots of the major contacts around the water moieties (E4, E5, E6 in complex 1 and E4` in complex 2).

Author Contributions

Conceptualization, M.A.M.A.-Y. and S.M.S.; formal analysis, E.M.F., M.M.S. and M.H.; investigation, E.M.F.; methodology, E.M.F. and A.B.; software, M.H. and S.M.S.; supervision, M.A.M.A.-Y., A.B. and S.M.S.; validation, A.E.-F. and A.B.; Funding acquisition: A.B.; visualization, A.E.-F.; writing—original draft, S.M.S.; writing—review and editing, M.A.M.A.-Y., A.E.-F. and A.B. All authors have read and agreed to the published version of the manuscript.

Funding

The authors would like to extend their sincere appreciation to the Researchers Supporting Project (RSP2023R64), King Saud University, Riyadh, Saudi Arabia.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Inorganics 11 00222 g001 550
Figure 1. Structure of DMPT.
Figure 1. Structure of DMPT.
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Inorganics 11 00222 sch001 550
Scheme 1. Synthesis of complexes 1 and 2.
Scheme 1. Synthesis of complexes 1 and 2.
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Figure 2. Asymmetric unit of [Ni(DMPT)(H2O)3](NO3)2.3H2O (1).
Figure 2. Asymmetric unit of [Ni(DMPT)(H2O)3](NO3)2.3H2O (1).
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Inorganics 11 00222 g003 550
Figure 3. All of the important hydrogen bond contacts (A) and 3D H-bonding network (B) in [Ni(DMPT)(H2O)3](NO3)2.3H2O complex.
Figure 3. All of the important hydrogen bond contacts (A) and 3D H-bonding network (B) in [Ni(DMPT)(H2O)3](NO3)2.3H2O complex.
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Inorganics 11 00222 g004 550
Figure 4. Asymmetric unit of the [Ni(DMPT)(H2O)3](NO3)2. H2O complex (2).
Figure 4. Asymmetric unit of the [Ni(DMPT)(H2O)3](NO3)2. H2O complex (2).
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Inorganics 11 00222 g005 550
Figure 5. All of the important hydrogen bond contacts (A) and 3D H-bonding network (B) in [Ni(DMPT)(H2O)3](NO3)2.H2O complex.
Figure 5. All of the important hydrogen bond contacts (A) and 3D H-bonding network (B) in [Ni(DMPT)(H2O)3](NO3)2.H2O complex.
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Inorganics 11 00222 g006 550
Figure 6. The anion–π interactions in complexes 1 and 2.
Figure 6. The anion–π interactions in complexes 1 and 2.
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Figure 7. The dnorm maps of the HF surface for all entities in complexes 1 (A) and 2 (B).
Figure 7. The dnorm maps of the HF surface for all entities in complexes 1 (A) and 2 (B).
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Figure 8. Distribution of the intermolecular interactions for the [Ni(DMPT)(H2O)3]2+ cation (A), outer-sphere nitrate anions (B) and hydrated water molecules (C) in both complexes.
Figure 8. Distribution of the intermolecular interactions for the [Ni(DMPT)(H2O)3]2+ cation (A), outer-sphere nitrate anions (B) and hydrated water molecules (C) in both complexes.
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Figure 9. Decomposed FP plots of the major contacts around the [Ni(DMPT)(H2O)3]2+ cation units E1 and E1` in complexes 1 and 2, respectively.
Figure 9. Decomposed FP plots of the major contacts around the [Ni(DMPT)(H2O)3]2+ cation units E1 and E1` in complexes 1 and 2, respectively.
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Figure 10. The shortest intermolecular interactions around E1 and E1` entities. The red, turquoise and green dotted lines represent the O…H, H…H and N…H contacts, respectively.
Figure 10. The shortest intermolecular interactions around E1 and E1` entities. The red, turquoise and green dotted lines represent the O…H, H…H and N…H contacts, respectively.
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Figure 11. The dnorm maps of the nitrate anions showing the O…H interactions (a) and their corresponding FP plots (b).
Figure 11. The dnorm maps of the nitrate anions showing the O…H interactions (a) and their corresponding FP plots (b).
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Inorganics 11 00222 g012 550
Figure 12. The dnorm maps showing the short contacts between crystal water molecules and other entities. The red, turquoise and green dotted lines represent the O…H, H…H and N…H contacts, respectively.
Figure 12. The dnorm maps showing the short contacts between crystal water molecules and other entities. The red, turquoise and green dotted lines represent the O…H, H…H and N…H contacts, respectively.
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Table
Table 1. Bond distances and angles (Å and °) for the coordination environment of [Ni(DMPT)(H2O)3](NO3)2.3H2O complex.
Table 1. Bond distances and angles (Å and °) for the coordination environment of [Ni(DMPT)(H2O)3](NO3)2.3H2O complex.
BondDistanceBondDistance
Ni(1)–N(2)2.0031(12)Ni(1)–O(3)2.0764(12)
Ni(1)–O(2)2.0242(12)Ni(1)–N(1)2.1002(13)
Ni(1)–O(1)2.0466(12)Ni(1)–N(4)2.2608(12)
BondsAngleBondsAngle
N(2)–Ni(1)–O(2)171.68(5)O(1)–Ni(1)–N(1)92.93(5)
N(2)–Ni(1)–O(1)90.08(5)O(3)–Ni(1)–N(1)87.39(5)
O(2)–Ni(1)–O(1)90.28(5)N(2)–Ni(1)–N(4)76.47(4)
N(2)–Ni(1)–O(3)91.46(5)O(2)–Ni(1)–N(4)111.85(5)
O(2)–Ni(1)–O(3)88.20(5)O(1)–Ni(1)–N(4)88.12(5)
O(1)–Ni(1)–O(3)178.46(5)O(3)–Ni(1)–N(4)92.24(5)
N(2)–Ni(1)–N(1)77.93(5)N(1)–Ni(1)–N(4)154.38(5)
O(2)–Ni(1)–N(1)93.75(5)
Table
Table 2. The hydrogen bond geometric parameters in [Ni(DMPT)(H2O)3](NO3)2.3H2O.
Table 2. The hydrogen bond geometric parameters in [Ni(DMPT)(H2O)3](NO3)2.3H2O.
D–H…AD–H/ÅH…A/ÅD…A/ÅD–H…A/°Symm. Code
C(11)–H(11B)...O(9)#10.992.393.356(2)165.2#1 −x + 3/2, y + 1/2, −z + 1/2
N(3)–H(3)...O(8)#20.88(2)2.07(2)2.9043(18)158.0(19)#2 −x + 1/2, y + 1/2, −z + 1/2
O(1)–H(1A)...O(14)0.82(2)1.82(2)2.6391(19)179(2)
O(3)–H(3A)...O(6)#30.83(3)2.00(3)2.8245(18)170(2)#3 x + 1, y, z
O(12)–H(12C)...O(9)#40.84(3)2.46(3)3.091(2)133(2)#4 x − 1/2, −y + 1/2, z + 1/2
O(12)–H(12C)...O(10)#40.84(3)2.04(3)2.870(2)170(3)#4 x − 1/2, −y + 1/2, z + 1/2
O(12)–H(12D)...O(5)#50.83(3)1.98(3)2.7972(17)169(2)#5 −x + 1, −y, −z + 1
O(3)–H(3B)...O(11)0.85(2)1.91(2)2.7540(18)171(2)
O(13)–H(13C)...N(5)#60.80(3)2.41(3)3.138(2)152(2)#6 −x + 3/2, y − 1/2, −z + 1/2
O(13)–H(13C)...O(6)#30.80(3)2.43(3)2.9541(19)124(2)#3 x + 1, y, z
O(14)–H(14A)...O(12)0.81(3)1.96(3)2.730(2)159(3)
O(2)–H(2A)...O(12)0.80(3)1.93(3)2.7227(18)171(3)
O(2)–H(2B)...O(13)0.84(3)1.85(3)2.6901(18)175(2)
O(1)–H(1B)...O(4)#70.82(3)1.95(3)2.7684(17)171(3)#7 −x + 1, −y + 1, −z + 1
O(14)–H(14B)...O(7)0.81(3)2.01(3)2.810(2)176(3)
O(13)–H(13D)...O(10)#60.83(3)2.05(3)2.861(2)165(3)#6 −x + 3/2, y − 1/2, −z + 1/2
Table
Table 3. Bond distances and angles (Å and °) for the coordination environment of [Ni(DMPT)(H2O)3](NO3)2.H2O complex.
Table 3. Bond distances and angles (Å and °) for the coordination environment of [Ni(DMPT)(H2O)3](NO3)2.H2O complex.
BondDistanceBondDistance
Ni(1)–N(2)2.0079(18)Ni(1)–O(1)2.0652(16)
Ni(1)–O(2)2.0378(17)Ni(1)–N(1)2.1031(18)
Ni(1)–O(3)2.0409(17)Ni(1)–N(8)2.1907(18)
BondsAngleBondsAngle
N(2)–Ni(1)–O(2)172.54(7)O(3)–Ni(1)–N(1)93.97(7)
N(2)–Ni(1)–O(3)94.34(7)O(1)–Ni(1)–N(1)91.21(7)
O(2)–Ni(1)–O(3)90.20(8)N(2)–Ni(1)–N(8)77.95(7)
N(2)–Ni(1)–O(1)88.89(7)O(2)–Ni(1)–N(8)108.09(7)
O(2)–Ni(1)–O(1)87.08(7)O(3)–Ni(1)–N(8)88.99(7)
O(3)–Ni(1)–O(1)174.37(7)O(1)–Ni(1)–N(8)87.17(7)
N(2)–Ni(1)–N(1)78.11(7)N(1)–Ni(1)–N(8)156.03(7)
O(2)–Ni(1)–N(1)95.69(7)
Table
Table 4. The hydrogen bond geometric parameters in [Ni(DMPT)(H2O)3](NO3)2.H2O.
Table 4. The hydrogen bond geometric parameters in [Ni(DMPT)(H2O)3](NO3)2.H2O.
D–H…AD–H/ÅH…A/ÅD…A/ÅD–H…A/°Symm. Code
C(12)–H(12B)...O(7)#10.992.433.122(3)126.9#1 x, y + 1, z
N(3)–H(3)...O(6)#20.88(3)2.06(3)2.930(3)168(3)#2 −x + 1, −y + 1, −z + 1
N(3)–H(3)...O(7)#20.88(3)2.60(3)3.170(3)123(2)#2 −x + 1, −y + 1, −z + 1
O(2)–H(2A)...O(9)0.83(3)1.96(3)2.773(3)168(3)
O(1)–H(1A)...O(4)#30.81(3)1.91(4)2.691(2)161(3)#3 −x + 1, −y + 2, −z + 1
O(1)–H(1B)...O(5)#40.86(4)1.97(4)2.798(2)161(3)#4 x − 1, y, z
O(2)–H(2B)...O(10)#50.82(3)1.96(3)2.775(3)175(3)#5 −x + 1, −y + 1, −z + 2
O(3)–H(3A)...O(12)0.84(3)1.85(4)2.686(3)170(3)
O(3)–H(3B)...O(6)0.82(4)1.95(4)2.757(3)171(4)
O(3)–H(3B)...O(8)0.82(4)2.57(4)3.184(3)134(3)
O(12)–H(12C)...O(11)#60.80(4)2.10(4)2.885(4)165(4)#6 −x + 1, −y, −z + 2
O(12)–H(12D)...O(9)1.01(6)1.91(6)2.841(3)152(5)
Table
Table 5. Distances (Å) of the significant short interactions in both complexes.
Table 5. Distances (Å) of the significant short interactions in both complexes.
Complex 1Complex 2
ContactDistanceContactDistance
O11…H3B1.779O8…H3B2.453
O13…H2B1.710O6…H3B1.784
O12…H2A1.749O9…H2A1.806
O14…H1A1.656O9…H12.533
O5…H12D1.829O12…H3A1.713
O6…H3A1.854O5…H1B1.855
O7…H3A2.439O7…H12B2.371
O4…H1B1.793O4…H1A1.749
O9…H11B2.300O5…H1B1.855
O8…H31.950O10…H2B1.794
O6…H32.528O6…H7B2.573
O11…H3C2.508O8…H42.449
O7…H42.405O6…H7A2.458
O10…H16B2.561O6…H31.937
O11…H16B2.530O7…H32.535
O7…H14B1.829O9…H12D1.932
O8…H14B2.585O11…H12C1.928
O6…H13C2.333O6…C83.208
O9…H12C2.361N10…H2A2.555
O10…H12C1.897N9…H3B2.465
O10…H13D1.903N5…H7C2.588
O11…H13D2.523C5…H18A2.660
O12…H14A1.795C16…H1B2.704
N5…H13C2.251C12…H1A2.593
N10…H16B2.519C9…H12A2.697
N10…H3B2.555C9…H7C2.708
N9…H14B2.536H12D…H3A2.151
C9…H10A2.633
C4…H18A2.706
C17…H12D2.430
H1A…H14A2.118
H2B…H13D2.152
Table
Table 6. Antibacterial and antifungal activities of DMPT and its Ni(II) complex in terms of inhibition zone diameters (mm) and MIC (μg/mL) a.
Table 6. Antibacterial and antifungal activities of DMPT and its Ni(II) complex in terms of inhibition zone diameters (mm) and MIC (μg/mL) a.
MicroorganismDMPT1Control
A. fumigatusNA b (ND) cNA b (ND) c17(156) d
C. albicansNA b (ND) cNA b (ND) c20(312) d
S. aureusNA b (ND) cNA b (ND) c24(9.7) e
B. subtilisNA b (ND) c12 (1250) c26(4.8) e
E. coliNA b (ND) c11 (1250) c30(4.8) e
P. vulgarisNA b (ND) cNA b (1250) c25(4.8) e
a Values outside and inside parentheses for inhibition zone diameter and MIC, respectively. b NA: No activity; c ND: not determined; d ketoconazole and e gentamycin.
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Fathalla, E.M.; Abu-Youssef, M.A.M.; Sharaf, M.M.; El-Faham, A.; Barakat, A.; Haukka, M.; Soliman, S.M. Synthesis, X-ray Structure of Two Hexa-Coordinated Ni(II) Complexes with s-Triazine Hydrazine Schiff Base Ligand. Inorganics 2023, 11, 222. https://doi.org/10.3390/inorganics11050222

AMA Style

Fathalla EM, Abu-Youssef MAM, Sharaf MM, El-Faham A, Barakat A, Haukka M, Soliman SM. Synthesis, X-ray Structure of Two Hexa-Coordinated Ni(II) Complexes with s-Triazine Hydrazine Schiff Base Ligand. Inorganics. 2023; 11(5):222. https://doi.org/10.3390/inorganics11050222

Chicago/Turabian Style

Fathalla, Eman M., Morsy A. M. Abu-Youssef, Mona M. Sharaf, Ayman El-Faham, Assem Barakat, Matti Haukka, and Saied M. Soliman. 2023. "Synthesis, X-ray Structure of Two Hexa-Coordinated Ni(II) Complexes with s-Triazine Hydrazine Schiff Base Ligand" Inorganics 11, no. 5: 222. https://doi.org/10.3390/inorganics11050222

APA Style

Fathalla, E. M., Abu-Youssef, M. A. M., Sharaf, M. M., El-Faham, A., Barakat, A., Haukka, M., & Soliman, S. M. (2023). Synthesis, X-ray Structure of Two Hexa-Coordinated Ni(II) Complexes with s-Triazine Hydrazine Schiff Base Ligand. Inorganics, 11(5), 222. https://doi.org/10.3390/inorganics11050222

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