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Article

Synthesis, X-ray Structure, Conformational Analysis, and DFT Studies of a Giant s-Triazine bis-Schiff Base

1
Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
2
Biochemistry of Department, College of Sciences, King Saud University, P.O. Box 22452, Riyadh 11495, Saudi Arabia
3
Laboratory of Plant Biotechnology Applied to Crop Improvement, Faculty of Science of Sfax, University of Sfax, Sfax 3038, Tunisia
4
Department of Chemistry, University of Jyväskylä, FI-40014 Jyväskylä, Finland
5
Department of Chemistry, Faculty of Science, Alexandria University, P.O. Box 426, Ibrahimia, Alexandria 21321, Egypt
*
Authors to whom correspondence should be addressed.
Submission received: 6 November 2021 / Revised: 15 November 2021 / Accepted: 16 November 2021 / Published: 20 November 2021
(This article belongs to the Special Issue New Trends in Crystals at Saudi Arabia)

Abstract

:
The current work involves the synthesis of 2,2′-(6-(piperidin-1-yl)-1,3,5-triazine-2,4-diyl)bis(hydrazin-2-yl-1-ylidene))bis(methanylylidene))diphenol 4, characterization, and the DFT studies of the reported compound. The crystal unit cell parameters of 4 are a = 8.1139(2) Å, b = 11.2637(2) Å, c = 45.7836(8) Å. The unit cell volume is 4184.28(15) Å3 and Z = 4. It crystallized in the orthorhombic crystal system and Pbca space group. The O…H, N…H, C…H, H…H and C…C intermolecular contacts which affect the crystal stability were quantitatively analyzed using Hirshfeld calculations. Their percentages were calculated to be 9.8, 15.8, 23.7, 46.4, and 1.6% from the whole contacts occurred in the crystal, respectively. Conformational analysis was performed using DFT calculations for 17 suggested conformers and the most stable conformer was found to be the one which is stabilized by two intramolecular O-H…N hydrogen bonding interactions. This conclusion was further revealed by natural bond orbital calculations.

Graphical Abstract

1. Introduction

Given the effectual reactivity of TCT (cyanuric chloride, 2,4,6-trichlorotriazine) with a diversity of nucleophiles, it is regularly used in organic synthesis as template to access numerous molecular systems [1,2]. TCT is an important moiety due to its lower price, marketable availability, and the three chlorine atoms can be replaced in stepwise manner [1]. TCT derivatives were reported to have a broad range of biological activities [3]. Some new s-triazine based chalcones and their derivatives were found to work as potent antimicrobial, anti-cancer and anti-malarial agents [4,5,6,7,8,9].
On the other hand, Schiff bases of triazine derivatives are considered as extraordinary class of compounds. The two connected nitrogen atoms (-CH=N-N-) are of distinct nature and the C=N that is conjugated with a lone pair of the second nitrogen are responsible for their properties [10,11,12,13,14,15,16]. This family of compounds are regularly used as polydentate chelating agents that form a diversity of complexes with a range of different metals [17,18,19]. Enormous hydrazones derivatives and their complexes have been used in several applications, such as metal-ions extraction and microdetermination of metal-ion [20]. Moreover, their biological activities have been reported in literatures [21,22,23,24,25]. Many synthesized s-triazine hydrazone derivatives were reported and explored with superior interest in supramolecular and coordination chemistry [26,27], material chemistry [28], and complexation with several metal-ions [29,30,31,32,33].
It is well known that the s-triazine bis-Schiff base compounds could exist in two main structures which are shown in Figure 1. In view of the interesting importance and the diverse structural features of this class of s-triazine based compounds, the present work presents the synthesis, characterization, X-ray single crystal structure investigations combined with Hirshfeld and DFT calculations of a novel giant s-triazine based Schiff base (4). Relative stability of 17 suggested conformers of 4 were also investigated.

2. Materials and Methods

Chemicals were purchased from Sigma-Aldrich Company (Chemie GmbH, 82024 Taufkirchen, Germany). Perkin-Elmer 2400 instrument (PerkinElmer, Inc., 940 Winter Street, Waltham, MA, USA) was used for CHN analyses.

2.1. Synthesis of 2,2′-(6-(piperidin-1-yl)-1,3,5-triazine-2,4-diyl)bis(hydrazin-2 -yl-1-ylidene))bis(methanylylidene))diphenol; 4

2,4-Dihydrazinyl-6-(piperidin-1-yl)-1,3,5-triazine (10 mmoles) was added portionwise to a hot solution of 2-hydroxybenzaldehyde (10 mmoles) in ethanol (100 mL) containing acetic acid (2–3 drops; Scheme 1). After complete addition, the reaction was heated under reflux for 6h and then was left cooling at room temperature and then filter the pure pale-yellow solid (the complete reaction was followed by TLC (ethyl acetate-hexane 2:1). The product was left to dry and then recrystallized from ethanol. Yield 95%; mp 263–265 °C; 1H NMR (DMSO-d6): δ = 1.52 (brs, 4H, 2CH2), 1.63 (brs, 2H, CH2), 3.80 (brs, 2H, CH2), 6.87–6.95 (m, 4H, Ar), 7.37–7.41 (m, 2H, Ar), 7.21–7.26 (m, 2H, Ar), 8.29 (s, 2H,CH=N), 11.20 (brs, 2H, NH), 12.15 (brs, 2H, OH) ppm; 13C NMR (DMSO-d6): δ = 24.3, 25.6, 43.6, 116.1, 118.9, 130.3, 143.9, 157.4, 162.8, 164.2 ppm; Anal. Calc. for C22H24N8O2 (432.49 g/mol): C, 61.10; H, 5.59; N, 25.91. Found: C, 61.23; H, 6.61; N, 25.74.

2.2. X-ray Structure Determinations

The crystal of 4 was immersed in cryo-oil, mounted in a loop at 120 K, and the data were collected on a Rigaku Oxford Diffraction Supernova diffractometer using Cu Kα radiation. The CrysAlisPro(v.1.171.40.67a) [34] software package was used for cell refinement and data reduction. A gaussian absorption correction (CrysAlisPro [34]) was applied to the intensities before structure solution. The structure was solved by intrinsic phasing (SHELXT [35]) method. Structural refinement was carried out using SHELXL(2018/3) [36] software with SHELXLE [37] graphical user interface. The NH and OH hydrogen atoms were located from the difference Fourier map and refined isotropically. All other hydrogen atoms were positioned geometrically and constrained to ride on their parent atoms, with C-H = 0.95–0.99 Å and Uiso = 1.2·Ueq(parent atom). The CIF data are given in details in Supplementary data and crystal structure measurement and refinments details are summarized in Table 1. Crystal Explorer 17.5 program [38] was used for Hirshfeld surface analysis.

3. Computational Details

Density functional calculations (DFT) at the B3LYP method and using 6-31G(d,p) basis sets were performed to optimize the molecular structure of the suggested 17 conformers of the studied s-triazine bis-Schiff base (Figure 2). For this task, Gaussian 09 package was used [39,40]. All optimized structures are local minimum as indicated from the absence of any imaginary vibrational mode. The calculated energies and thermodynamic parameters of the suggested conformers were used to predict the most stable form. NBO 3.1 program [41] was used for natural bond orbital analysis.

4. Results and Discussion

4.1. Crystal Structure Description

The X-ray structure of 4 is shown in Figure 3. The compound crystallized in the orthorhombic crystal system and Pbca space group with unit cell parameters of a = 8.1139(2) Å, b = 11.2637(2) Å, c = 45.7836(8) Å, and unit cell volume of 4184.28(15) Å3 while Z = 4. Some bond distances and angles are depicted in Table 2.
It is well known that the s-triazine bis-Schiff base compounds could exist in two main structures which are shown in Figure 1. The solid-state structure of 4 indicated that the conformation of the two hydrazine arms are quite different and exists in Form 2 rather than Form 1. A main reason for the extrastability of Form 2 is the less steric among the salicylidene moieties. In Form 1, strong repulsion between the two salicylidene arms makes this option is not sterically favored situation.
In addition, this molecular conformation of the bis-Schiff base s-triazine is found stabilized by two strong intramolecular O-H…N hydrogen bonding interactions between the OH group of the salicylidene moiety acting as hydrogen bond donor with the nitrogen atom of the azomethine group as a hydrogen bond acceptor. The donor-acceptor distances are 2.648(3) and 2.608(1) Å for the O1-H1...N1 and O2-H2...N8 intramolecular O-H…N hydrogen bonds, respectively. Additionally, there are two weak intramolecular C-H…N hydrogen bonds which are C10-H10B...N3 and C14-H14A...N4 with donor-acceptor distances of 2.785(2) and 2.746(2) Å, respectively. More details regarding the hydrogen bond parameters are listed in Table 3. The intramolecular hydrogen bonding interactions are presented as turquoise dotted lines in the upper part of Figure 4, while the red dotted lines represent the intermolecular hydrogen bonding interactions.
The supramolecular structure of 4 is controlled by strong N7-H7...O2 hydrogen bonding interaction with a hydrogen-acceptor distance of 1.996(2) Å and donor-acceptor distance of 2.918(1) Å. In addition, the molecules are further connected by weak C-H...O interactions (Table 3). Presentation of the molecular packing is given in Figure 4 (lower part).

4.2. Analysis of Molecular Packing

The Hirshfeld surfaces of 4 are shown in Figure 5. The most important contacts having interaction distances shorter than the van der Waals (vdW) radii sum of the two interacting atoms are labeled A to E in the dnorm map. The O…H, N…H, C…H, H…H, and C…C contacts are the most important in the crystal stability. The interaction distances obtained from the Hirshfeld calculations are depicted in Table 4.
The percentage contributions for all possible interactions in the crystal are presented graphically in Figure 6. The O…H, N…H, C…H, H…H and C…C contributed by 9.8, 15.8, 23.7, 46.4, and 1.6% from the whole fingerprint area, respectively. As can be seen from Figure 5, all these interactions appeared as red colour regions in the dnorm where the contact distances are shorter than vdW sum of the interacting atoms.
In addition, the decomposed fingerprint plot gave good indication on the importance of these contacts (Figure 7). For example, the O…H interactions appeared as very sharp spikes indicating strong interactions. The presence of some short C…C contacts as red spots in the dnorm with red/blue triangle in the shape index and flat green area in curvedness map revealed very well the presence of π-π stacking interactions. The shortest C…C contacts are C16…C21 (3.348 Å) and C16…C22 (3.235 Å).

4.3. Conformational Analysis

The structure of the 17 suggested conformers were calculated and the optimized geometries are shown in Figure 8. The total energies and thermodynamic parameters of the of the studied s-triazine bis-Schiff base are depicted in Table 5. The results indicated that conformer 4 is the most stable thermodynamically as this conformer has the lowest energy among the studied conformers which is found in accord with the reported X-ray structure of this compound. The second and third most stable conformers are 4I and 4L, respectively. These conformers are energetically higher than the most stable one by only 0.2951 and 2.2345 kcal/mol, respectively. A clear common reason for the extrastabilty of these three conformers is the presence of two intramolecular O-H…N hydrogen bonds in the three structures (Figure 8). On the other hand, some of the other conformers showed one intramolecular O-H…N hydrogen while the others did not show any intramolecular O-H…N hydrogen bond. The conformers 4B, 4K, and 4N were the highest energetically as these conformers did not comprise any intramolecular O-H…N hydrogen bond. The relative energies of the studied conformers are presented graphically in Figure 9.

4.4. Optimized Geometry

The calculated structure of 4 is shown in Figure 10. Few differences between the experimental and optimized structures were detected where the deviations in bond distances not exceed 0.02 Å (Table S1; Supplementary Data). These deviations could be attributed to the crystal packing effects. Generally, there are good correlations between the calculated bond angles and distances with the experimental measurements (Figure 11).
The studied system comprised CHNO skeleton where the oxygen and nitrogen atoms as well as the majority of carbon atoms are negatively charged (Figure 12). The morpholine oxygen atoms and the s-triazine N-atoms have the highest negative charge. The studied compound is polar molecule (2.7591 Debye) and the dipole moment vector is shown in Figure 13 (left part). The red regions in molecular electrostatic potential reveal high electron density related to hydroxyl oxygen atoms and the aryl moieties. In contrast, the blue regions are related to the atomic sites with lowest electron density which is close to the NH protons.
It is clear that the HOMO and LUMO levels are mainly distributed over the π-system of 4 (Figure 13). As a result, the HOMO→LUMO excitation is mainly a π-π* transition. The HOMO→LUMO excitation energy is 4.1536 eV. In addition, the reactivity indices include ionization potential (I = −EHOMO), electron affinity (A = −ELUMO), chemical potential (μ = −(I + A)/2), hardness (η = (I − A)/2), as well as electrophilicity index (ω = μ2/2η) [42,43,44,45,46,47]. The calculated values of these descriptors are 5.5391, 1.3856, −3.4624, 4.1536, and 1.4431, respectively.

4.5. NBO Analysis

The intramolecular charge transfer (IMCT) plays very important rule in the stability of compound. In this regard, the different IMCT processes (σ-σ*, π→π*, n→σ* and n→π*) in 4 were calculated [48,49] and their stabilization energies (E(2)) are listed in Table 6. The maximum interaction energy due to the σ-σ* intramolecular charge transfer (IMCT) is 5.99 kcal/mol for the BD(1)N7-C23→BD*(1)N9-C40. The π→π*, n→π* and n→σ* IMCT processes have higher interaction energies with maximum E(2) values of 48.26, 71.52, and 24.48 kcal/mol for the BD(2)N5-C24→BD*(2)N7-C23, LP(1)N8→BD*(2)N5-C24, and LP(1)N3→BD*(1)O1-H56 IMCT, respectively. Interestingly, the presence of LP(1)N3→BD*(1)O1-H56 and LP(1)N10→BD*(1)O2-H55 IMCT processes with high E(2) values of 24.48 and 23.08 kcal/mol, respectively confirmed the stability of conformer 4 via intramolecular O-H…N hydrogen bonding interactions.

5. Conclusions

The synthesis and X-ray structure of the new 2,2′-(6-(piperidin-1-yl)-1,3,5-triazine-2,4-diyl)bis(hydrazin-2-yl-1-ylidene))bis(methanylylidene))diphenol giant s-triazine bis-Schiff base were presented. Among the suggested 17 conformers, 4 was found to be the most stable one in agreement with the reported X-ray structure. Generally, conformers with larger number of intramolecular O-H…N hydrogen bonding interactions are the most stable. The presence of intramolecular O-H…N hydrogen bonds was further revealed by NBO calculations. Using Hirshfeld calculations, the O…H, N…H, C…H, H…H, and C…C intermolecular contacts are the most important in the crystal stability. Their percentages were calculated to be 9.8, 15.8, 23.7, 46.4, and 1.6% from the whole contacts occurred in the crystal, respectively. MEP, HOMO, LUMO, dipole moment, and natural charges were also presented.

Supplementary Materials

The following are available online at https://0-www-mdpi-com.brum.beds.ac.uk/article/10.3390/cryst11111418/s1, Table S1: The calculated and experimental bond distances and angles, Table S2: Bond lengths [Å] and angles [°] for 4, Table S3: Anisotropic displacement pa-rameters (Å2 × 103) for 4. The anisotropic displacement factor exponent takes the form: −2p2[h2 a*2U11 + ... + 2 h k a* b* U12], Table S4: Hydrogen coordinates (× 104) and isotropic displacement parameters (Å2 × 103) for 4, Table S5: Torsion angles [°] for 4, Figure S1: 1H and 13C NMR spectra of 4.

Author Contributions

Conceptualization, A.E.-F., S.M.S. and Z.M.A.; synthesis and characterization, A.E.-F. and Z.M.A.; X-ray crystal structure determination, M.H.; computational investigation, S.M.S.; writing original manuscript, A.E.-F., M.H., Z.M.A., M.I.A.-Z., A.B.B. and S.M.S.; revision and editing, A.E.-F., M.H., Z.M.A., M.I.A.-Z., A.B.B. and S.M.S. All authors have read and agreed to the published version of the manuscript.

Funding

Deanship of Scientific Research at King Saud University for funding (RGP-070).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding this work through research group No (RGP-070).

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. The general structure of s-triazine bis-Schiff base.
Figure 1. The general structure of s-triazine bis-Schiff base.
Crystals 11 01418 g001
Scheme 1. Synthesis of 4.
Scheme 1. Synthesis of 4.
Crystals 11 01418 sch001
Figure 2. The suggested conformers of the s-triazine bis-Schiff base; 4.
Figure 2. The suggested conformers of the s-triazine bis-Schiff base; 4.
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Figure 3. X-ray structure with thermal ellipsoids at 50% probability level for 4.
Figure 3. X-ray structure with thermal ellipsoids at 50% probability level for 4.
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Figure 4. Hydrogen bond contacts (upper) and molecular packing (lower) of 4.
Figure 4. Hydrogen bond contacts (upper) and molecular packing (lower) of 4.
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Figure 5. The dnorm maps for the important interactions in 4. A: O…H, B: N…H; C: H…C; D: H…H, and E: C…C contacts.
Figure 5. The dnorm maps for the important interactions in 4. A: O…H, B: N…H; C: H…C; D: H…H, and E: C…C contacts.
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Figure 6. Intermolecular interactions and their percentages in 4.
Figure 6. Intermolecular interactions and their percentages in 4.
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Figure 7. Full and decomposed fingerprint plots for the important interactions in 4.
Figure 7. Full and decomposed fingerprint plots for the important interactions in 4.
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Figure 8. The optimized geometries of the suggested conformers of 4. The intramolecular O-H…N hydrogen bonds are presented by black dotted line.
Figure 8. The optimized geometries of the suggested conformers of 4. The intramolecular O-H…N hydrogen bonds are presented by black dotted line.
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Figure 9. Relative energy of the suggested conformers of 4 compared to the most stable one.
Figure 9. Relative energy of the suggested conformers of 4 compared to the most stable one.
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Figure 10. The calculated structure (left) of 4 and its overlay with the experimental one (right).
Figure 10. The calculated structure (left) of 4 and its overlay with the experimental one (right).
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Figure 11. Correlations between the calculated and experimental geometric parameters.
Figure 11. Correlations between the calculated and experimental geometric parameters.
Crystals 11 01418 g011
Figure 12. The natural atomic charges in 4.
Figure 12. The natural atomic charges in 4.
Crystals 11 01418 g012
Figure 13. The MEP, HOMO, and LUMO of 4.
Figure 13. The MEP, HOMO, and LUMO of 4.
Crystals 11 01418 g013
Table 1. Crystal Data of 4.
Table 1. Crystal Data of 4.
CCDC2118553
empirical formulaC22H24N8O2
Fw432.49
temp (K)120(2)
λ (Å)1.54184
Crystal systemOrthorhombic
space groupPbca
a (Å)8.1139(2)
b (Å)11.2637(2)
c (Å)45.7836(8)
V (Å3)4184.28(15)
Z8
ρcalc (Mg/m3)1.373
μ (Mo Kα) (mm−1)0.762
No. reflns.29,199
Unique reflns.4404
Completeness to θ = 67.684°99.9%
GOOF (F2)1.047
Rint0.0345
R1 a (I ≥ 2σ)0.0374
wR2 b (I ≥ 2σ)0.0911
a R1 = Σ||Fo| − |Fc||/Σ|Fo|. b wR2 = [Σ[w(Fo2 − Fc2)2]/Σ[w(Fo2)2]]1/2.
Table 2. Selected bond lengths [Å] and angles [°] for 4.
Table 2. Selected bond lengths [Å] and angles [°] for 4.
AtomsDistanceAtomsDistance
O1-C11.3578(14)N4-C91.3477(15)
O2-C221.3624(16)N5-C151.3379(15)
N1-C71.2882(15)N5-C81.3445(15)
N1-N21.3697(13)N6-C91.3493(15)
N2-C81.3691(15)N6-C101.4657(15)
N3-C81.3291(15)N6-C141.4707(15)
N3-C91.3622(15)N7-C151.3565(15)
N4-C151.3394(15)N7-N81.3622(14)
AtomsAngleAtomsAngle
C7-N1-N2116.50(10)C10-N6-C14114.56(10)
C8-N2-N1121.50(10)C15-N7-N8120.60(10)
C8-N3-C9113.29(10)C16-N8-N7117.41(10)
C15-N4-C9113.93(10)O1-C1-C2118.15(11)
C15-N5-C8112.03(10)O1-C1-C6121.81(11)
C9-N6-C10122.81(10)C2-C1-C6120.03(11)
C9-N6-C14121.91(10)C3-C2-C1120.06(12)
Table 3. Hydrogen bonds for 4 [Å and °].
Table 3. Hydrogen bonds for 4 [Å and °].
D-H...Ad(D-H)d(H...A)d(D...A)<(DHA)
O1-H1...N10.958(2)1.789(2)2.648(1)147.6(2)
O2-H2...N80.92(2)1.80(2)2.608(1)145.0(2)
N7-H7...O2 i0.927(2)1.996(2)2.918(1)173.9(2)
C7-H7A...N3 ii0.952.613.494(1)155.0
C10-H10B...N30.992.352.7846(15)106.0
C12-H12B...O1 iii0.992.573.2842(15)129.0
C14-H14A...N40.992.292.7459(16)107.0
C20-H20...N5 iv0.952.523.4165(18)158.0
i 1/2 − x, 1/2 + y, z; ii 1/2 − x, −1/2 + y, z; iii 3/2 − x, 1/2 + y, z and iv −1/2 + x, 1/2 − y, 1 − z.
Table 4. Intermolecular interactions in 4.
Table 4. Intermolecular interactions in 4.
ContactDistanceContactDistance
H12A…C52.747H2A…N42.522
H7A…C92.499H7A…N32.488
H7A…C92.494H20…N52.394
H16…C222.756O2…H71.914
H15…C212.509O1…H32.533
C16…C213.348H1…H12B2.155
C16…C223.235H21…H162.294 a
a longer distances compared to the vdWs radii sum.
Table 5. The calculated energies and thermodynamic properties of the studied conformers.
Table 5. The calculated energies and thermodynamic properties of the studied conformers.
Param.44A4B4C4D4E4F4G4H
E a−1441.3046−1441.2844−1441.2635−1441.2841−1441.286847−1441.290592−1441.272653−1441.276378−1441.272801
ZPVE a0.45350.45260.45170.45250.4523380.4526150.4518410.4520840.451863
Etot a−1440.8511−1440.8318−1440.8118−1440.8316−1440.8345−1440.8380−1440.8208−1440.8243−1440.8209
∆E b0.000012.088224.652512.236010.40448.227818.999016.814018.9203
H a−1440.8229−1440.8031−1440.7827−1440.8029−1440.805625−1440.80919−1440.791531−1440.795082−1440.791662
∆H b0.000012.378725.216712.527410.81188.574819.655817.427619.5736
G a−1440.9125−1440.8946−1440.8756−1440.8942−1440.897779−1440.900977−1440.884482−1440.887956−1440.884582
∆G b0.000011.219723.163511.43689.22117.214417.565015.385017.5022
S c188.6180192.5080195.5080192.2760193.953193.183195.632195.469195.568
4I4J4K4L4M4N4O4P
E a−1441.3044−1441.2844−1441.2638−1441.3010−1441.2878−1441.2597−1441.2747−1441.2672
ZPVE a0.45380.45260.45180.45340.45260.45150.45210.4516
Etot a−1440.8506−1440.8318−1440.8120−1440.8475−1440.8353−1440.8081−1440.8227−1440.8156
∆E b0.295112.105824.51612.23459.910326.944817.839522.2519
H a−1440.8228−1440.8031−1440.7830−1440.8192−1440.8069−1440.7790−1440.7935−1440.7863
∆H b0.020112.374325.02852.291610.036227.509618.435922.9514
G a−1440.9125−1440.8939−1440.8750−1440.9093−1440.8955−1440.8715−1440.8856−1440.8790
∆G b0.009411.641423.54441.978510.651825.702416.855921.0106
S c188.6540191.0780193.5960189.6690186.5540194.6810193.9180195.1290
a A.U. b kcal/mol c Cal/Mol. K.
Table 6. The IMCT processes and E(2) values calculated using NBO method.
Table 6. The IMCT processes and E(2) values calculated using NBO method.
NBOiNBOjE(2)NBOiNBOjE(2)
σ→σ*π→π*
BD(1)O1-H56BD*(1)C11-C125.06BD(2)N3-C21BD*(2)C18-C207.87
BD(1)O2-H55BD*(1)C50-C525.02BD(2)N5-C24BD*(2)N 7-C2348.26
BD(1)N5-C24BD*(1)N 4-C235.63BD(2)N6-C40BD*(2)N 5-C2439.11
BD(1)N7-C23BD*(1)N 9-C405.99BD(2)N7-C23BD*(2)N 6-C4045.32
BD(1)C20-C21BD*(1)N 3-N 45.22BD(2)N10-C41BD*(2)C43-C447.88
BD(1)C41-C43BD*(1)N 9-N105.20BD(2)C11-C12BD*(2)C14-C1625.09
BD(2)C11-C12BD*(2)C18-C2017.00
BD(2)C14-C16BD*(2)C11-C1217.55
BD(2)C14-C16BD*(2)C18-C2024.64
BD(2)C18-C20BD*(2)N 3-C2124.97
BD(2)C18-C20BD*(2)C11-C1221.73
n→σ*n→π*
LP(1)O 1BD*(1)C11-C207.96BD(2)C18-C20BD*(2)C14-C1617.03
LP(1)O 2BD*(1)C43-C528.02BD(2)C43-C44BD*(2)N10-C4124.95
LP(1)N 3BD*(1)O 1-H5624.48BD(2)C43-C44BD*(2)C46-C4817.02
LP(1)N 3BD*(1)N 4-H548.74BD(2)C43-C44BD*(2)C50-C5221.68
LP(1)N 3BD*(1)C21-H229.92BD(2)C46-C48BD*(2)C43-C4424.65
LP(1)N 5BD*(1)N 7-C2313.54BD(2)C46-C48BD*(2)C50-C5217.57
LP(1)N 5BD*(1)N 6-C2412.09BD(2)C50-C52BD*(2)C43-C4417.07
LP(1)N 6BD*(1)N 5-C2411.84BD(2)C50-C52BD*(2)C46-C4825.10
LP(1)N 6BD*(1)N 7-C4013.29LP(2)O 1BD*(2)C11-C1235.52
LP(1)N 7BD*(1)N 5-C2312.74LP(2)O 2BD*(2)C50-C5235.53
LP(1)N 7BD*(1)N 6-C4012.66LP(1)N 4BD*(2)N 3-C2131.38
LP(1)N10BD*(1)O 2-H5523.08LP(1)N 4BD*(2)N 7-C2353.44
LP(1)N10BD*(1)C41-H4210.00LP(1)N 8BD*(2)N 5-C2471.52
LP(1)N10BD*(1)N 9-H538.82LP(1)N 9BD*(2)N 6-C4052.75
LP(1)N 9BD*(2)N10-C4131.48
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Almarhoon, Z.M.; Al-Zaben, M.I.; Ben Bacha, A.; Haukka, M.; El-Faham, A.; Soliman, S.M. Synthesis, X-ray Structure, Conformational Analysis, and DFT Studies of a Giant s-Triazine bis-Schiff Base. Crystals 2021, 11, 1418. https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11111418

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Almarhoon ZM, Al-Zaben MI, Ben Bacha A, Haukka M, El-Faham A, Soliman SM. Synthesis, X-ray Structure, Conformational Analysis, and DFT Studies of a Giant s-Triazine bis-Schiff Base. Crystals. 2021; 11(11):1418. https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11111418

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Almarhoon, Zainab M., Maha I. Al-Zaben, Abir Ben Bacha, Matti Haukka, Ayman El-Faham, and Saied M. Soliman. 2021. "Synthesis, X-ray Structure, Conformational Analysis, and DFT Studies of a Giant s-Triazine bis-Schiff Base" Crystals 11, no. 11: 1418. https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11111418

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