Synthesis, X-ray structure, Hirshfeld analysis, and DFT studies of a new Pd(II) complex with an anionic s-triazine NNO donor ligand

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY-NC-ND 4.0 https://creativecommons.org/licenses/by-nc-nd/4.0/ Synthesis, X-ray structure, Hirshfeld analysis, and DFT studies of a new Pd(II) complex with an anionic s-triazine NNO donor ligand © 2020 Elsevier B.V. All rights reserved. Accepted version (Final draft) Soliman, Saied M.; Lasri, Jamal; Haukka, Matti; Elmarghany, Adel; Al-Majid, Abdullah Mohammed; El-Faham, Ayman; Barakat, Assem Soliman, S. M., Lasri, J., Haukka, M., Elmarghany, A., Al-Majid, A. M., El-Faham, A., & Barakat, A. (2020). Synthesis, X-ray structure, Hirshfeld analysis, and DFT studies of a new Pd(II) complex with an anionic s-triazine NNO donor ligand. Journal of Molecular Structure, 1217, Article 128463. https://doi.org/10.1016/j.molstruc.2020.128463 2020 Journal Pre-proof Synthesis, X-ray structure, Hirshfeld analysis, and DFT studies of a new Pd(II) complex with an anionic s-triazine NNO donor ligand Saied M. Soliman, Jamal Lasri, Matti Haukka, Adel Elmarghany, Abdullah Mohammed Al-Majid, Ayman El-Faham, Assem Barakat PII: S0022-2860(20)30788-2 DOI: https://doi.org/10.1016/j.molstruc.2020.128463 Reference: MOLSTR 128463 To appear in: Journal of Molecular Structure Received Date: 12 March 2020 Revised Date: 7 May 2020 Accepted Date: 14 May 2020 Please cite this article as: S.M. Soliman, J. Lasri, M. Haukka, A. Elmarghany, A.M. Al-Majid, A. ElFaham, A. Barakat, Synthesis, X-ray structure, Hirshfeld analysis, and DFT studies of a new Pd(II) complex with an anionic s-triazine NNO donor ligand, Journal of Molecular Structure (2020), doi: https:// doi.org/10.1016/j.molstruc.2020.128463. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier B.V. 1 Synthesis, X-ray structure, Hirshfeld analysis, and DFT studies of a new Pd(II) complex with an anionic s-triazine NNO donor ligand Saied M. Soliman 1 *, Jamal Lasri 2 *, Matti Haukka 3 , Adel Elmarghany 4,5 , Abdullah Mohammed Al-Majid, 4 Ayman El-Faham 1,4 , and Assem Barakat 4 * 1 Department of Chemistry, Faculty of Science, Alexandria University, P.O. Box 426, Ibrahimia, Alexandria 21321, Egypt 2 Department of Chemistry, Rabigh College of Science and Arts, P.O. Box 344, King Abdulaziz University, Jeddah, Saudi Arabia 3 Department of Chemistry, University of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä, Finland 4 Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia 5 Chemistry Department, Faculty of Science, Suez Canal University, Ismailia 41522, Egypt * Correspondence: Saied M. Soliman: [email protected] (S.M.S.); Jamal Lasri: [email protected] (J.L.); Assem Barakat: [email protected] (A.B.). 2 Abstract A new Pd(II) complex, [Pd(Triaz)Cl], with the hydrazono-s-triazine ligand, 2,4-di-tertbutyl-6-((2-(4-morpholino-6-(phenylamino)-1,3,5-triazin-2-yl)hydrazono)methyl)phenol, was synthesized by the reaction of PdCl 2 with the organic ligand (1:1) in acetone under isothermal conditions. The molecular structure of the [Pd(Triaz)Cl] complex was determined using FTIR and 1 H NMR spectroscopic techniques, and single-crystal X-ray diffraction. Moreover, using Hirshfeld surface analysis, the percentages of the intermolecular interactions were determined. The obtained values were 60.6%, 11.6%, 8.1%, 3.6%, and 5.0% for the H···H, C···H, O···H, N···H, and Cl···H interactions, respectively. Among them, the O···H, C···H and C···N interactions are considered extremely important. Natural bond orbital calculations have been used to calculate the amount of electron transfer from the ligand to the metal ion and to evaluate the Pd-N, Pd-O, and Pd-Cl coordination bonding interactions. Keywords: S-triazine; Hydrazone; Pd(II) complex; Hirshfeld surface analysis; NBO 3 Introduction s-Triazine is a heterocyclic motif for multiple synthetic and natural products [1]. Being an important scaffold, s-triazine derivatives have been extensively studied in both pharmaceutical and coordination chemistry [2,3]. Some of these derivatives, e.g., 2-amino-4morphlino-s-triazine, and hexamethylmelamine, exhibited a wide range of pharmaceutical features such as antitumor activity [4], antioxidant [5], antiviral [6], herbicidal, antimicrobial, and antibacterial [7] properties. Furthermore, the syntheses of various mono-, di-, and trisubstituted s-triazines derivatives from cyanuric chloride have been reported with remarkable pharmaceutical activities [8-13] In particular, hydrazine-based s-triazines derivatives have shown potency activities as anticancer agents for A431 ( epidermoid carcinoma ) and A549 (lung carcinoma) compared to Lapatinib, HKI-272, and AST-1306 as standard references [14]. In addition, they have been used as inhibitors for wtEGFR, EGFR, and mTOR receptors [15,16]. Recently, our research group has reported several complexes bearing NNN-tridentate ligands derived from s-triazine with divalent metal ions, such as Co(II) [17], Ni(II) [18], Cd(II) [19a] and Mn(II) [19b]. Furthermore, s-triazine ligands have been used for recovering Pd(II) from strongly acidic solutions [20]. In this work, we studied the structural aspects of a new Pd(II) complex, [Pd(Triaz)Cl], which contains the hydrazono-s-triazine ligand (HTriaz) 2,4-di-tert-butyl-6-((2-(4-morpholino-6- (phenylamino)-1,3,5-triazin-2-yl)hydrazono)methyl)phenol (Scheme 1). Both molecular and supramolecular structures were investigated using X-ray crystallography, FTIR 1 H NMR spectra, Hirshfeld surface analysis, and DFT calculations. The anti-cancer activity was also explored against two cancer cell lines including breast cancer (MCF-7) and human prostate cancer (PC3). 4 Scheme 1. Synthesis of the [Pd(Triaz)Cl] complex. Experimental General FTIR spectra were measured on a PerkinElmer Spectrum 100 FT-IR spectrophotometer (PerkinElmer Inc., Waltham, MA, USA). 1 H NMR spectra of HTriaz and [Pd(Triaz)Cl] were recorded on DMSO-d 6 using a JEOL 400 MHz spectrometer (JEOL Ltd., Tokyo, Japan) at room temperature. Mass spectra were recorded on JMS-600 H JEOL spectrometer ( JEOL Ltd., Tokyo, Japan) . Synthesis of the ligand (E)-2,4-di-tert-butyl-6-((2-(4-morpholino-6-(phenylamino)-1,3,5triazin-2-yl)hydrazono)methyl)phenol (HTriaz) The ligand ( HTriaz ) was prepared as previously reported [21]. Synthesis of [Pd(Triaz)Cl] complex Palladium(II) chloride (21.1 mg, 0.119 mmol) was added to 20 mL of an acetone solution of (HTriaz) (60.0 mg, 0.119 mmol). The reaction mixture was stirred at 50 °C for 4 days. Afterwards, the mixture was filtered and maintained at room temperature to allow for the slow evaporation of the solvent, yielding the final product [Pd(Triaz)Cl] as reddish-brown block crystals. 1 H NMR (400 MHz, DMSO-d 6 , ppm): δ 10.84 (s, 1H, NH), 8.22 (s, 1H, NH), 7.97 (s, 1H, CH=N), 7.60 (d, 2H, J HH = 8.1 Hz, phenyl), 7.39 (t, 2H, J HH = 7.6 Hz, phenyl), 7.30 (s, 1H, C 6 H 2 ), 7.22 (s, 1H, C 6 H 2 ), 7.13 (t, 1H, J HH = 7.6 Hz, phenyl), 3.74 (d, 4H, J HH = 4.5 Hz, 5 morpholine), 3.68 (d, 4H, J HH = 5.0 Hz, morpholine), 1.37 (s, 9H, tert-butyl), 1.26 (s, 9H, tert-butyl). IR (KBr) cm −1 : 3435 (NH), 3263, 3102, 2956, 2856, and 1626 (C=N), and 1579 (C=C). LC-MS (ESI + -MS): 627.43 [M] + . Anal. calcd. for C 28 H 36 ClN 7 O 2 Pd: C, 52.18; H, 5.63; N, 15.21. Found: C, 52.15; H, 5.59; N, 15.25. X-Ray structural determinations The crystal of [Pd(Triaz)Cl] was immersed in cryo-oil, mounted in a loop, and measured at 170 K. XRD data were collected on a Bruker Kappa Apex II diffractometer with MoKα radiation. For cell refinement and data reduction, the Denzo-Scalepack [22] software package was used. A numerical absorption correction (SADABS [23]) was applied to the data before structure solution. The structure of [Pd(Triaz)Cl] was solved by intrinsic phasing using the SHELXT software [24]. Structural refinement was then performed using the SHELXL-2017 package [24] and the SHELXLE [25] graphical user interface. A disordered acetone molecule of as solvent of crystallization in [Pd(Triaz)Cl] was disordered over two sites sharing locations of C28 and C28B carbon atoms. The occupancy ratio of the disordered components was 0.51/0.49. The NH hydrogen atoms were located from the difference Fourier map and isotropically refined. The rest of the hydrogen atoms were geometrically positioned and constrained to ride on their parent atoms with C-H = 0.95–0.99 Å and U iso = 1.2–1.5 eq (parent atom). Topology analyses were performed using the Crystal Explorer 17.5 program [26] to determine the contribution percentages of the different intermolecular interactions in the crystal structure of [Pd(Triaz)Cl]. Computational details Density functional theory (DFT) single point calculations were performed using the Gaussian 09 software package [27] with the MPW1PW91 and Wb97XD methods [28] combined with the cc-PVTZ and cc-PVTZ-PP [29] basis sets for nonmetal atoms and Pd, respectively. The multiplicity of the system was set to be 1 because the well known fact that tetra-coordinated 6 Pd(II) complexes are square planar and diamagnetic. The natural charge populations and interaction energies between the donor atoms and the central metal ion, Pd(II), were computed using NBO 3.1 [30] program. Results and discussion Synthesis and characterization of [Pd(Triaz)Cl] The Pd(II) complex, [Pd(Triaz)Cl], was synthesized as shown in Scheme 1 and characterized by FTIR, and 1 H NMR spectroscopy, ESI + -MS, elemental analysis, and single crystal X-ray diffraction. The FTIR spectrum of the Pd(II) complex [Pd(Triaz)Cl] exhibits signals characteristic for the functional groups as follow: NH (3435), C=N (1628), and C=C (1579 cm −1 ). In the 1 H NMR spectrum, the five phenyl protons were observed as doublet, triplet, and triplet at δ 7.60, 7.39, and 7.13 ppm with coupling constants (J HH ) of 8.1, 7.6, and 7.6 Hz (integrations 2:2:1), respectively. Furthermore, the two protons of the tetra substituted phenyl ring (C 6 H 2 ) were observed as two singlets at δ 7.30 and 7.22 ppm. The eight morpholine protons were then detected as doublets at δ 3.74 and 3.68 ppm with coupling constants (J HH ) of 4.5 and 5.0 Hz, respectively. The signals of the two tert-butyl groups were detected as singlets at δ 1.37 and 1.26 ppm. The two NH protons, which appeared at δ 11.30 and 9.34 ppm in the (HTriaz) ligand, were slightly shifted in the Pd(II) complex to δ 10.84 and 8.22 ppm. The CH=N proton was observed at δ 8.28 ppm in (HTriaz); however, it was detected at δ 7.97 ppm in the Pd(II) complex (Figs. 1–3). 7 Fig. 1. 1 H NMR spectrum of the (HTriaz) ligand in DMSO-d 6 . 14 Fig. 7 2D fingerprint plot (left) and d norm map (right) of the O···H contacts of [Pd(Triaz)Cl]. Fig. 8. Decomposed d norm (−0.06 to 3.72) and FP plots of the C···H (orange) and C···N (black) contacts of [Pd(Triaz)Cl]. 15 DFT studies Natural population analysis The divalent Pd ion was coordinated with two negatively charged ligand groups (Cl − and Triaz − ). Their charges as isolated ions were +2, −1, and −1, respectively. Because of the interaction between the Pd(II) ion (Lewis acid) and the ligand groups (Lewis bases), part of the negative charge was transferred from ligand to the Pd(II) (Table 3). The chloride ion transferred 0.506–0.520 e − to Pd(II); however, the anionic organic ligand transferred almost all of its negative charge to the metal center (0.963–0.974 e − ). Therefore, Triaz − has a net charge very close to zero (−0.026 to −0.037 e − ) and the charge of Pd(II) decreased to 0.505– 0.530 e − . Table 3. Natural charges at the Pd(II) atom, and the coordinated Cl − and Triaz − . Atom MPW1PW91 WB97XD Pd 0.5053 0.5303 Cl¯ −0.4797 −0.4937 Triaz‾ −0.0256 −0.0367 Using natural bond orbital (NBO) calculations, the strength of the interactions between the Pd(II) center and ligand donor atoms was estimated (Table 4). The interaction energy of the Pd-N(hydrazone) was significantly higher than that for the Pd-N(s-triazine). There is only one anti-bonding natural orbital (LP*(6)) from the Pd(II) that contributes in the interaction with the N1 lone pair filled nonbonding natural orbital. The LP*(6) NBO has mainly a sorbital character with some contribution from p-orbitals and very little contribution from dorbitals. This can be inferred from the nearly spherical shape of the isodensity surface shown in Fig. 9. Similarly, the Pd-N(hydrazone) bonds are attributed to the interaction of the filled lone pair NBO from the corresponding nitrogen atom with the empty LP*(5)Pd anti-bonding NBO. The orbital contributions of LP*(5)Pd are very similar to LP*(6)Pd; however, the former has lesser p-orbital character compared to the latter. The LP*(6) NBO contributed to all of the Pd-N, Pd-O, and Pd-Cl interactions. The Pd-O coordination interaction was 16 attributed to the overlap between the LP(3)O filled NBO and LP*(5)Pd empty anti-bonding NBO. The net interaction energy of the Pd-O bond was 193.41 and 168.99 kcal/mol, using WB97XD and MPW1PW91 methods, respectively. The Pd-Cl coordination was attributed to the mixed interactions between the filled NBOs of the Cl − ligand and the anti-bonding NBOs of the Pd(II) central metal ion (Table 4). Fig. 9 shows the anti-bonding NBOs of Pd(II), and their corresponding occupancies and energies are listed in Table 5. The filled donor NBOs of the isolated ligand have almost 2.0 e − , which are significantly lowered in the complex because of the interactions with the Pd(II) anti-bonding NBOs. The latter have almost zero occupancy in the free (isolated) Pd(II) and increased up to 0.4662 e − in LP*(5)Pd because of the electron donation from the ligand donor atoms to the metal ion. Table 4. The donor ( NBO i )-acceptor ( NBO j ) interaction energies of Pd-N, Pd-O, and Pd-Cl coordination interactions. NBO i NBO j WB97XD MPW1PW91 LP(1)O1 LP*(5)Pd1 13.75 15.38 LP(1)O1 LP*(7)Pd1 20.41 20.00 LP(2)O1 LP*(8)Pd1 6.06 4.47 LP(3)O1 LP*(5)Pd1 116.79 97.98 LP(3)O1 LP*(6)Pd1 8.53 7.23 LP(3)O1 LP*(7)Pd1 27.87 23.93 O1→Pd1 193.41 168.99 LP(1)N7 LP*(5)Pd1 118.81 101.16 LP(1)N7 LP*(6)Pd1 11.98 10.74 LP(1)N7 LP*(7)Pd1 27.60 24.05 N7→Pd1 158.39 135.95 LP(1)N1 LP*(6)Pd1 104.23 90.88 N1→Pd1 104.23 90.88 LP(1)Cl1 LP*(5)Pd1 5.24 5.64 LP(1)Cl1 LP*(6)Pd1 4.16 4.78 LP(1)Cl1 LP*(7)Pd1 5.18 4.30 LP(2)Cl1 LP*(5)Pd1 9.63 9.38 LP(2)Cl1 LP*(6)Pd1 9.83 10.04 LP(3)Cl1 LP*(5)Pd1 1.50 1.21 LP(3)Cl1 LP*(6)Pd1 1.22 0.91 LP(3)Cl1 LP*(8)Pd1 7.17 5.68 Cl1→Pd1 43.93 41.94 17 Table 5. Occupancy and energy of the different NBOs included in the Pd-O, Pd-Cl, and Pd-N interactions. MPW1PW91 WB97XD NBO Occupancy Energy Occupancy Energy LP(1)O1 1.9428 −0.5755 1.9435 −0.6305 LP(2)O1 1.7117 −0.2829 1.7186 −0.3335 LP(3)O1 1.6309 −0.4595 1.6390 −0.5106 LP(1)N1 1.6532 −0.4398 1.6604 −0.4862 LP(1)N7 1.6303 −0.4641 1.6368 −0.5104 LP(1)Cl1 1.9739 −0.4264 1.9751 −0.4851 LP(2)Cl1 1.9689 −0.7465 1.9703 −0.7951 LP(3)Cl1 1.9663 −0.2911 1.9681 −0.3683 LP*(5)Pd1 0.4662 0.0215 0.4607 0.0584 LP*(6)Pd1 0.1617 0.4265 0.1640 0.4942 LP*(7)Pd1 0.1059 0.2893 0.1075 0.3447 LP*(8)Pd1 0.0644 0.1112 0.0637 0.1653 LP*(5)Pd1 LP*(6)Pd1 LP*(7)Pd1 LP*(8)Pd1 Fig. 9. Anti-bonding NBOs of Pd(II) contributing in the interactions with the NBOs of the donor ligand groups. Antiproliferative activity 18 The anti-cancer activity of the synthesized metal complex [Pd(Triaz)Cl], was further explored against two cancer cell lines (MCF-7 and PC3) followed by MTT assay. Initially, the cytotoxicity of starting ligand (HTriaz) was previously examined and reported which possess very week activity against the MCF-7 breast cancer and HCT-116 colon cancer [21]. The results shown for the antiproliferative activity of the [Pd(Triaz)Cl], 18.23% inhibition against PC3 cell line at 50μg/mL. On the other hands, exhibited 7.1% inhibition when used 30μg/mL against the MCF-7 breast cancer. It can be concluded that both ligand and its Pd-(II) complex have week activity against tumor. Conclusions A Pd(II) complex, [Pd(Triaz)Cl], with a NNO-donor chelate derived from hydrazono-striazine ligand was synthesized and its molecular structure investigated using different spectroscopic techniques and single-crystal X-ray diffraction combined with Hirshfeld topology analysis. The latter was performed to describe the supramolecular structure of the complex. The neutral square planar [Pd(Triaz)Cl] complex comprised one mono-negative tridentate ligand, Triaz − , and one chloride ion, Cl − , in the inner sphere. The O ··· H, C ··· H, and C ··· N interactions are the most important ones, controlling the molecular packing of the complex. DFT calculations with the aid of NBO analysis were used to describe the Pd-N, PdO and Pd-Cl coordination interactions. Due to the week anti-cancer activity for the metal complex and the ligand further investigation and screen for different cancer lines well be carried out in the future. Acknowledgments The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for providing funding to this Research group NO (RGP −257). The authors thank the Deanship of Scientific Research and RSSU at King Saud University for their technical support. 19 References 1. Blotny, G. (2006). Recent applications of 2,4,6-trichloro-1,3,5-triazine and its derivatives in organic synthesis. Tetrahedron, 62(41), 9507-9522. 2. Shah, D. R., Modh, R. P., Chikhalia, K. H. (2014). Privileged s-triazines: structure and pharmacological applications. Future Med. Chem., 6(4), 463-477. 3. Ramírez, J., Stadler, A. M., Brelot, L., Lehn, J. M. (2008). Coordinative, conformational and motional behaviour of triazine-based ligand strands on binding of Pb (II) cations. Tetrahedron, 64(36), 8402-8410. 4. Hedayatullah, M., Lion, C., Slimane, A. B., Da Conceiçao, L., & Nachawati, I. (1999). Synthesis of reactive s-triazines bearing a cage system derived from adamantane as precursors of hexamethylmelamine analogues. Heterocycles, 51(8), 1891-1896. 5. Vančo, J., Švajlenová, O., Račanská, E., Muselík, J., & Valentová, J. (2004). Antiradical activity of different copper (II) Schiff base complexes and their effect on alloxan-induced diabetes. J. Trace Elem. Med. Bio., 18(2), 155-161. 6. Jarrahpour, A., Khalili, D., De Clercq, E., Salmi, C., Brunel, J. M. (2007). Synthesis, antibacterial, antifungal and antiviral activity evaluation of some new bis-Schiff bases of isatin and their derivatives. Molecules, 12(8), 1720-1730. 7. Carter, J. S., Kramer, S., Talley, J. J., Penning, T., Collins, P., Graneto, M. J., Seibert, K., Koboldt, C. M., Masferrer, J., Zweifel, B. (1999). Synthesis and activity of sulfonamidesubstituted 4,5-diaryl thiazoles as selective cyclooxygenase-2 inhibitors. Bioorg. Med. Chem. Lett., 9(8), 1171-1174. 8. Kolesinska, B., Kaminski, Z. J. (2009). The Umpolung of substituent effect in nucleophilic aromatic substitution. A new approach to the synthesis of N,N-disubstituted melamines (triazine triskelions) under mild reaction conditions. Tetrahedron, 65(18), 3573-3576. 9. Khattab, S. N., Khalil, H. H., Bekhit, A. A., Abd El-Rahman, M. M., de la Torre, B. G., El-Faham, A., Albericio, F. (2018). 1,3,5-Triazino peptide derivatives: synthesis, characterization, and preliminary antileishmanial activity. ChemMedChem, 13(7), 725735. 10. Sunduru, N., Gupta, L., Chaturvedi, V., Dwivedi, R., Sinha, S., Chauhan, P. M. (2010). Discovery of new 1,3,5-triazine scaffolds with potent activity against Mycobacterium tuberculosis H37Rv. Eur. J. Med. Chem., 45(8), 3335-3345. 20 11. Zhou, C., Min, J., Liu, Z., Young, A., Deshazer, H., Gao, T., Chang, T., Kallenbach, N. R. (2008). Synthesis and biological evaluation of novel 1,3,5-triazine derivatives as antimicrobial agents. Bioorg. Med. Chem. Lett., 18(4), 1308-1311. 12. Sosič, I., Mirković, B., Turk, S., Štefane, B., Kos, J., Gobec, S. (2011). Discovery and kinetic evaluation of 6-substituted 4-benzylthio-1,3,5-triazin-2 (1H)-ones as inhibitors of cathepsin B. Eur. J. Med. Chem., 46(9), 4648-4656. 13. Garaj, V., Puccetti, L., Fasolis, G., Winum, J. Y., Montero, J. L., Scozzafava, A., Vullo, D., Innocenti, A., Supuran, C. T. (2005). Carbonic anhydrase inhibitors: novel sulfonamides incorporating 1,3,5-triazine moieties as inhibitors of the cytosolic and tumour-associated carbonic anhydrase isozymes I, II and IX. Bioorg. Med. Chem. Lett., 15(12), 3102-3108. 14. Bai, F., Liu, H., Tong, L., Zhou, W., Liu, L., Zhao, Z., Liu, X., Jiang, H., Wang, X., Xie, H., & Li, H. (2012). Discovery of novel selective inhibitors for EGFRT790M/L858R. Bioorg. Med. Chem. Lett., 22(3), 1365-1370. 15. El-Faham, A., Soliman, S. M., Ghabbour, H. A., Elnakady, Y. A., Mohaya, T. A., Siddiqui, M. R., Albericio, F. (2016). Ultrasonic promoted synthesis of novel s-triazineSchiff base derivatives; molecular structure, spectroscopic studies and their preliminary anti-proliferative activities. J. Mol. Struct., 1125, 121-135. 16. Menear, K. A., Gomez, S., Malagu, K., Bailey, C., Blackburn, K., Cockcroft, X. L., Ewen, S., Fundo, A., Le Gall, A., Hermann, G., Sebastian, L., (2009). Identification and optimisation of novel and selective small molecular weight kinase inhibitors of mTOR. Bioorg. Med. Chem. Lett., 19(20), 5898-5901. 17. Soliman, S. M., El-Faham, A. (2019). Synthesis and structural DFT studies of Ni (II) and Co (II) complexes with s-triazine-based di-compartmental ligand. Polyhedron, 165, 162170. 18. Soliman, S. M., El-Faham, A. (2019). Synthesis, molecular structure and DFT studies of two heteroleptic nickel (II) s-triazine pincer type complexes. J. Mol. Struct., 1185, 461468. 19. a) Soliman, S. M., El-Faham, A. (2019). Synthesis and structure diversity of high coordination number Cd (II) complexes of large s-triazine bis-Schiff base pincer chelate. Inorg. Chim. Acta, 488, 131-140 and b) Soliman, S. M., & El-Faham, A. (2018). Synthesis, characterization, and structural studies of two heteroleptic Mn (II) complexes with tridentate N,N,N-pincer type ligand. J. Coord. Chem., 71(15), 2373-2388. 21 20. a) Zhang, A., Xu, L., Lei, G. (2016). Separation and complexation of palladium( II ) with a new soft N-donor ligand 6,6′-bis(5,6-dinonyl-1,2,4-triazin-3-yl)-2,2′-bipyridine (C9-BTBP) in nitric acid medium, New J. Chem., 40, 6374-6383; b) Xu, L., Zhang, A., Pu, N., Lu, Y., Yang, H., Liu, Z., Ji, Y. (2019). Unusual complexation behaviors of R-BTPs with water molecule and Pd( II ) caused by electronic modulation of substituents on BTP backbone: new insights into palladium separation under the framework of minor actinides’ partitioning, New J. Chem., 43, 9052-9065; c) Xu, L., Zhang, A., Pu, N., Xu, C., Chen, J. (2019). Preparation and characterization of a novel macroporous silica-bipyridine asymmetric multidentate functional adsorbent and its application for heavy metal palladium removal, J. Hazard. Mat., 376, 188-199; d) Xu, L., Zhang, A., Lu, Y., Yang, H. & Liu, Z. A. (2016). Phenanthroline-derived ligand and its complexation with Pd(II): from ligand design, synthesis and Pd(II) complexes structures to its application, RSC Adv, 6, 99859-99866; e) Zhang, A., Wang, X. , Chai, Z. (2010). Synthesis of a macroporous silica‐based derivative of pyridine material and its application in separation of palladium, AICHE Journal, 56(12), 3074-3083. 21. Barakat, A., El-Senduny, F. F., Almarhoon, Z., Al-Rasheed, H. H., Badria, F. A., AlMajid, A. M., Ghabbour, H. A., El-Faham, A. (2019). Synthesis, X-ray crystal structures, and preliminary antiproliferative activities of new s-triazine-hydroxybenzylidene hydrazone derivatives. Journal of Chemistry, 2019 Article ID 9403908, 10. 22. Otwinowski, Z., Minor, W. Processing of X-ray Diffraction Data Collected in Oscillation Mode, Academic Press, New York, pp. 307-326, 1997. In Methods in Enzymology, Volume 276, Macromolecular Crystallography, Part A, Carter, C. W., Sweet, J., Eds.; Academic Press: New York, USA, 1997; pp 307-326. 23. Sheldrick, G. M. SADABS - Bruker Nonius scaling and absorption correction -, Bruker AXS, Inc.: Madison, Wisconsin, USA, 2012. 24. Sheldrick, G. M. (2015). Crystal structure refinement with SHELXL. Acta Crystallogr. C, C71, 3-8. 25. Hübschle, C. B., Sheldrick, G. M. Dittrich, B. (2011). ShelXle: a Qt graphical user interface for SHELXL. J. Appl. Cryst. 44, 1281-1284. 26. Turner, M. J., McKinnon, J. J., Wolff, S. K., Grimwood, D. J., Spackman, P. R., Jayatilaka, D., & Spackman, M. A. Crystal Explorer17 (2017) University of Western Australia. http://hirshfeldsurface.net. 22 27. Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A. et al., (2009) Gaussian, Inc., Wallingford CT, 2009. 28. a) Chai, J. D. & Head-Gordon, M. (2008). Long-range corrected hybrid density functionals with damped atom–atom disperson corrections. Phys. Chem. Chem. Phys., 10, 6615; b) Adamo C., Barone, V. (1998). Exchange functionals with improved long-range behavior and adiabatic connection methods without adjustable parameters: The mPW and mPW1PW models, J. Chem. Phys., 108, 664-75. 29. a) https://bse.pnl.gov/bse/portal; b) Feller, D. (1996). The role of databases in support of computational chemistry calculations. J. Comp. Chem., 17, 1571-1586; c) Schuchardt, K. L., Didier, B.T., Elsethagen, T., Sun, L., Gurumoorthi, V., Chase, J., Li, J., & Windus, T. L. (2007). Basis set exchange: A community database for computational sciences, J. Chem. Inf. Model., 47,1045-1052. 30. NBO Version 3.1, E.D. Glendening, A.E. Reed, J.E. Carpenter, F. Weinhold, NBO Version 3.1, CI, University of Wisconsin, Madison, 1998. Highlights • The new Pd(II) complex [Pd(Triaz)Cl] bearing hydrazono-s-triazine ligand explored. • The molecular structure assigned by X-ray single crystal technique. • Molecular insights were also investigated.