Synthesis, crystal structures and antimicrobial activity of palladium metal complexes of sulfonyl hydrazone ligands European Journal of Chemistry 11 (4) (2020) 377-384 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.11.4.377-384.2040 European Journal of Chemistry View Journal Online View Article Online Synthesis, crystal structures and antimicrobial activity of palladium metal complexes of sulfonyl hydrazone ligands Samina Karimkha Tadavi 1, Ratnamala Subhash Bendre 2, Satish Vittal Patil 3, Shubha Gaguna 4 and Jamatsing Darbarsing Rajput 5,* 1 Department of Chemistry, Jashbhai Muljibhai Patel Arts, Commerce and Science College, Bhandara, Maharashtra, 441904, India saminatadavi30@gmail.com (S.K.T.) 2 School of Chemical Sciences, Kavayitri Bahinabai Chaudhari North Maharashtra University, Jalgaon, Maharashtra, 425001, India bendrers@rediffmail.com (R.S.B.) 3 School of Life Sciences, Kavayitri Bahinabai Chaudhari North Maharashtra University, Jalgaon, Maharashtra, 425001, India satish.patil7@gmail.com (S.V.P.) 4 Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, 560012, India shu.sg13@gmail.com (S.G.) 5 Department of Chemistry, Faculty of BP Arts, SMA Science and KKC Commerce College Chalisgaon, Maharashtra, 424101, India jamatsingh50@gmail.com (J.D.R.) * Corresponding author at: Department of Chemistry, Faculty of BP Arts, SMA Science and KKC Commerce College Chalisgaon, Maharashtra, 424101, India. e-mail: jamatsingh50@gmail.com (J.D. Rajput). 10.5155/eurjchem.11.4.377-384.2040 Received: 31 August 2020 Received in revised form: 07 November 2020 Accepted: 22 November 2020 Published online: 31 December 2020 Printed: 31 December 2020 Palladium complexes of sulfonyl hydrazone based ligands have been prepared by refluxing with the corresponding ligands and Pd(II) salt in 2:1 ratio. The compounds have been characterized by FT-IR and UV-Vis spectroscopic methods. The crystal structure of the prepared palladium complexes has been determined by single-crystal X-ray crystallographic technique. Crystal data for C40H50N4O6PdS2 (PMHT-Pd(II) complex): triclinic, space group P-1 (no. 2), a = 7.1561(6) Å, b = 12.1300(11) Å, c = 12.6117(17) Å, α = 63.498(11)°, β = 86.694(9)°, γ = 81.451(7)° and Z = 1. The final R1 was 0.0699 (I > 2σ(I)) and wR2 was 0.1834 (all data). Crystal data for C36H42N4O6PdS2 (PTHC-Pd(II) complex): monoclinic, space group P21/n (no. 14), a = 8.6726(2) Å, b = 20.8824(4) Å, c = 10.3351(2) Å, β = 104.429(2)° and Z = 2. The final R1 was 0.0344 (I > 2σ(I)) and wR2 was 0.0840 (all data). Crystal data for C36H42N4O6PdS2 (PTHT-Pd(II) complex): monoclinic, space group P21/n (no. 14), a = 9.7658(2) Å, b = 10.0488(3) Å, c = 18.7714(4) Å, β = 99.602(2)° and Z = 2. The final R1 was 0.0334 (I > 2σ(I)) and wR2 was 0.0832 (all data). Crystal data for C40H50N4O6PdS2 (PMHC-Pd(II) complex): triclinic, space group P-1 (no. 2), a = 10.2070(9) Å, b = 12.1841(13) Å, c = 16.8879(19) Å, α = 109.005(6)°, β = 90.061(5)°, γ = 99.032(5)° and Z = 2. The final R1 was 0.0822 (I > 2σ(I)) and wR2 was 0.2293 (all data). The single-crystal structure data showed a good agreement with the experimental results. The synthesized complexes were screened for their in vitro antibacterial activity against one Gram-negative (Escherichia coli) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and for in vitro antifungal activity against Aspergillus niger, Aspergillus flavus and Aspergillus fumigatus. The PTHC- Pd(II) complex possesses the nearby significant antifungal activity analogous to the standard drug fluconazole against selected fungal strains Aspergillus niger, Aspergillus Flavus and Aspergillus fumigatus as well as the same complex showed the antibacterial activity for Staphylococcus aureus as comparable to standard ofloxacin drug. Sulfonamide Antifungal activity Palladium complex Antibacterial activity Single crystal structure Sulfonyl hydrazine derivative Cite this: Eur. J. Chem. 2020, 11(4), 377-384 Journal website: www.eurjchem.com 1. Introduction Sulfonamides and sulfonyl hydrazones have been shown to be active in several pharmacological tests, demonstrating antibacterial, antitumor, diuretic, antiviral, and antinociceptive activities; and specific enzyme inhibition such as carbonic anhydrase, c-secretase HIV protease, metalloproteinase, and hormone regulation among others [1,2]. Although a large number of antimicrobial drugs are existing commercially, the requirement for more effective ones continues to exist, because the most common bacteria are resistant to available drugs [3]. Due to their significant pharmacology applications and widespread use in medicine, these compounds have gained importance in bioinorganic and metal-based drug chemistry [4,5]. To find better compounds, some metal sulphonamides have attracted much attention due to the fact that the complexes showed more activity than both free ligands and the corresponding metallic salts [6]. Some metal sulfonamide complexes have attracted much attention due to the fact that shows greater biological activity than the sulfonamide ligands or metallic salts [7,8]. In our previous studies, we reported a series of novel hydrazone and sulfonyl hydrazine linkages containing carvac- rol, thymol, and eugenol derivatives, thereafter anticancer and ABSTRACT RESEARCH ARTICLE KEYWORDS http://dx.doi.org/10.5155/eurjchem.11.4.377-384.2040 http://www.eurjchem.com/ http://dx.doi.org/10.5155/eurjchem.11.4.377-384.2040 mailto:saminatadavi30@gmail.com mailto:bendrers@rediffmail.com mailto:satish.patil7@gmail.com mailto:shu.sg13@gmail.com mailto:jamatsingh50@gmail.com mailto:jamatsingh50@gmail.com http://www.eurjchem.com/ https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.11.4.377-384.2040&domain=pdf&date_stamp=2020-12-31 378 Tadavi et al. / European Journal of Chemistry 11 (4) (2020) 377-384 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.377-384.2040 Figure 1. The molecular structure of PMHT-Pd(II) complex with atom numbering scheme. Figure 2. The molecular structure of PTHC-Pd(II) complex with atom numbering scheme. antioxidant activities were tested using sulforhodamine B (SRB) assay and 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay (DPPH), respectively. Molecular docking studies of all derivatives against the active site of human Heme oxygenase-1 indicated that interaction with the number of amino acid residues of human Heme oxygenase-1 was crucial for antioxidant activity. In the present study, reporting four palladium(II) complexes of sulfonyl hydrazine derivatives of carvacrol, thymol based nitrogen, and oxygen-containing donor ligands. The sulfonyl hydrazides have explored to synthesize new Schiff bases, as it involves two chemical parts as well as biological key moieties viz. sulfonyl groups and hydrazines and have a connection with some other important chemical classes; sulfonamides (O2S-N) and azomethines (C=N) [9]. The struc- tures of all synthesized palladium(II) complexes have been examined using FT-IR and UV-Vis spectrophotometric methods and finalized by single-crystal X-ray crystallographic technique. The synthesized complexes were screened for their in vitro antibacterial activity against one Gram-negative (Escherichia coli) and two Gram-positive (Bacillus subtilis and Staphylo- coccus aureus) bacterial strains and for in vitro antifungal activity against Aspergillus niger, Aspergillus flavus and Aspergillus fumigatus. 2. Experimental 2.1. Materials and methods All solvents and palladium metal salt were purchased from Aldrich and used without further purification. FT-IR spectra were recorded as KBr pellets on a Shimadzu FT-IR-8400 spectrometer. The electronic spectra were recorded as DMF solution on the Shimadzu UV-2400 series spectrophotometer. 2.2. Single-crystal X-ray diffraction data collection The crystals of PMHC-Pd(II) complex were grown by slow evaporation of chloroform solvent by dissolving 0.5 g of the compound at 7-10 °C. The X-ray single crystal diffraction data were recorded on a Bruker APEX II κ-CCD diffractometer. A suitable crystal was selected and mounted on a Bruker APEX-II CCD diffractometer. The data were collected with MoKα (λ = 0.71073 Å) radiation for PMHC-Pd(II) complex. The cell refine- ment and data reduction were performed using APEX2/SAINT [10] and SAINT/XPREP [11], respectively. The structure has solved by using SHELXS [12] and refined by SHELXL [13]. The suitable crystals of PMHT-Pd(II), PTHC-Pd(II), and PTHT-Pd(II) for X-ray crystallography analysis were obtained by slow evaporation of chloroform at room temperature. The X-ray single crystal diffraction data were recorded on an Oxford Xcalibur Eos (Nova) CCD diffractometer using MoKα radiation (λ = 0.71073 Å). A suitable crystal was selected and mounted on the diffractometer. The structures are solved by direct methods and refined by full-matrix least-squares on F2 using the SHELXT software package [14]. All geometrical data were calculated using PLATON [15]. Molecular structure and packing diagrams were generated using OLEX2 and MERCURY, respectively [16,17]. The molecular structure of the complexes with the atomic numbering scheme is shown in Figures 1-4. The crystallographic parameters, data collection, and refinement data for the complexes are given in Table 1. The bond lengths, bond angles, and hydrogen bonds for all complexes are given in Tables 2-4, respectively. Tadavi et al. / European Journal of Chemistry 11 (4) (2020) 377-384 379 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.377-384.2040 Table 1. Crystal data and structure refinement for palladium complexes. Compound PMHT-Pd(II) complex PTHC-Pd(II) complex PTHT-Pd(II) complex PMHC-Pd(II) complex CCDC 1887978 1887979 1887980 1888204 Empirical formula C40H50N4O6PdS2 C36H42N4O6PdS2 C36H42N4O6PdS2 C40H50N4O6PdS2 Formula weight 853.36 797.25 797.25 853.36 Temperature (K) 298.15 293(2) 293(2) 293(2) Crystal system Triclinic Monoclinic Monoclinic Triclinic Space group P-1 P21/n P21/n P-1 a (Å) 7.1561(6) 8.6726(2) 9.7658(2) 10.2070(9) b (Å) 12.1300(11) 20.8824(4) 10.0488(3) 12.1841(13) c (Å) 12.6117(17) 10.3351(2) 18.7714(4) 16.8879(19) α (°) 63.498(11) 90 90 109.005(6) β (°) 86.694(9) 104.429(2) 99.602(2) 90.061(5) γ (°) 81.451(7) 90 90 99.032(5) Volume (Å3) 968.8(2) 1812.70(7) 1816.32(8) 1958.1(4) Z 1 2 2 2 ρcalc (g/cm3) 1.463 1.461 1.458 1.447 μ (mm-1) 0.639 0.677 0.676 0.632 F(000) 444.0 824.0 824.0 888.0 Crystal size (mm3) 0.25 × 0.2 × 0.2 0.25 × 0.2 × 0.2 0.25 × 0.2 × 0.2 0.25 × 0.2 × 0.2 Radiation MoKα (λ = 0.71073) MoKα (λ = 0.71073) MoKα (λ = 0.71073) MoKα (λ = 0.71073) 2Θ range for data collection (°) 6.798 to 52.734 6.744 to 52.724 6.894 to 52.744 4.046 to 49.998 Index ranges -8 ≤ h ≤ 8 -14 ≤ k ≤ 15 -15 ≤ l ≤ 15 -10 ≤ h ≤ 10 -26 ≤ k ≤ 26 -12 ≤ l ≤ 12 -12 ≤ h ≤ 12 -12 ≤ k ≤ 12 -23 ≤ l ≤ 23 -12 ≤ h ≤ 12 -14 ≤ k ≤ 14 -20 ≤ l ≤ 20 Reflections collected 11772 30464 22204 27355 Independent reflections 3939 [Rsigma = 0.0913] 3695 [Rsigma = 0.0246] 3714 [Rsigma = 0.0312] 27355 [Rsigma = 0.1141] Data/restraints/parameters 3939/0/249 3695/0/231 3714/0/235 27355/57/527 Goodness-of-fit on F2 1.057 1.093 1.055 1.046 Final R indexes [I≥2σ (I)] R1 = 0.0699 wR2 = 0.1623 R1 = 0.0344 wR2 = 0.0809 R1 = 0.0334 wR2 = 0.0788 R1 = 0.0822 wR2 = 0.1942 Final R indexes [all data] R1 = 0.1022 wR2 = 0.1834 R1 = 0.0394 wR2 = 0.0840 R1 = 0.0409 wR2 = 0.0832 R1 = 0.1278 wR2 = 0.2293 Largest diff. peak/hole (e Å-3) 1.45/-1.13 0.41/-0.26 0.42/-0.27 1.72/-2.30 Figure 3. The molecular structure of PTHT-Pd(II) complex with atom numbering scheme. Figure 4. The molecular structure of PMHC-Pd(II) complex with atom numbering scheme. 380 Tadavi et al. / European Journal of Chemistry 11 (4) (2020) 377-384 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.377-384.2040 Table 2. Bond lengths for palladium complexes. Atom Atom Length (Å) Atom Atom Length (Å) Atom Atom Length (Å) Atom Atom Length (Å) PMHT-Pd(II) complex Pd1 O111 1.988(4) O11 C2 1.310(6) C3 C2 1.433(8) C14 C15 1.517(9) Pd1 O11 1.988(4) N11 C20 1.312(7) C4 C5 1.362(8) C5 C6 1.394(9) Pd1 N111 2.001(4) N11 N12 1.416(7) C4 C16 1.515(8) C8 C7 1.415(8) Pd1 N11 2.001(4) C20 C3 1.425(8) C2 C1 1.440(8) C10 C11 1.379(9) S1 N12 1.690(5) C9 C8 1.403(8) C1 C14 1.521(8) C7 C12 1.393(8) S1 O13 1.442(5) C9 C10 1.390(8) C1 C6 1.368(8) C7 C18 1.516(9) S1 O12 1.423(5) C9 C19 1.518(8) C14 C13 1.525(8) C12 C11 1.374(9) S1 C8 1.783(6) C3 C4 1.443(8) PTHC-Pd(II) complex Pd1 O1 1.9811(16) O1 C5 1.319(3) C1 C9 1.519(4) C15 C16 1.375(5) Pd1 O12 1.9810(16) N1 C7 1.299(3) C1 C2 1.368(4) C15 C18 1.505(5) Pd1 N12 1.9809(19) N1 N2 1.427(3) C9 C8 1.521(4) C15 C14 1.385(4) Pd1 N1 1.9809(19) C6 C7 1.431(3) C9 C10 1.498(5) C12 C13 1.382(4) S1 N2 1.684(3) C6 C5 1.418(3) C4 C3 1.368(4) C12 C17 1.387(4) S1 O3 1.427(2) C6 C1 1.431(3) C4 C11 1.506(4) C13 C14 1.376(4) S1 O2 1.427(2) C5 C4 1.415(4) C2 C3 1.401(4) C16 C17 1.386(4) S1 C12 1.757(3) PTHT-Pd(II) complex S1 O3 1.423(2) O1 C1 1.320(3) C1 C2 1.425(4) C12 C17 1.376(4) S1 O2 1.423(2) N1 N2 1.421(3) C6 C5 1.379(4) C5 C4 1.392(4) S1 C13 1.745(3) N1 C7 1.298(3) C6 C9 1.511(4) C15 C16 1.388(4) S1 N2 1.689(3) C13 C14 1.384(4) C2 C7 1.419(4) C17 C16 1.380(4) Pd1 O1 1.9745(17) C13 C12 1.383(4) C2 C3 1.434(4) C9 C8 1.523(5) Pd1 O13 1.9745(17) C14 C15 1.370(4) C3 C4 1.353(4) C9 C10 1.524(4) Pd1 N1 1.980(2) C1 C6 1.419(3) C3 C11 1.503(4) C16 C18 1.501(4) Pd1 N13 1.980(2) PMHC-Pd(II) complex C1 C2 1.490(14) C12 C13 1.477(15) N1 S1 1.661(10) Pd1 N24 1.976(8) C2 C3 1.415(13) C13 C14 1.404(14) N2 Pd1 1.976(8) Pd1 O34 1.964(7) C2 C7 1.376(14) C13 C18 1.402(15) N3 S2 1.666(9) Pd2 N45 1.969(8) C3 C4 1.425(13) C14 C15 1.368(16) N4 Pd2 1.969(8) Pd2 O65 1.958(7) C3 O3 1.323(11) C15 C16 1.381(16) O3 Pd1 1.964(7) C8 C9 1.62(3) C4 C5 1.423(13) C15 C20 1.522(15) O4 S2 1.446(9) C8 C10 1.46(2) C4 C11 1.464(13) C16 C17 1.367(15) O5 S2 1.401(8) C8 C9' 1.47(2) C5 C6 1.376(14) C17 C18 1.406(15) N1 N2 1.408(12) C8 C10' 1.57(3) C5 C8 1.536(14) C17 C19 1.515(15) C11 N2 1.233(11) S1 O2 1.423(9) C6 C7 1.376(15) C18 S1 1.781(11) O6 Pd2 1.958(7) S1 O1 1.442(8) 1 -x, 1-y, -z, 2 1-x, -y, -z, 3 -x, 1-y, -z, 4 2-x, -y, -z; 5 1-x, -y, 1-z. 2.3. Synthesis of ligands The synthesis of sulfonyl hydrazone based ligands was prepared by multistep process reaction. In the first step, the synthesis of ortho formyl phenolic monoterpenoids (ortho formyl thymol (2-hydroxy-3-isopropyl-6-methylbenzaldehyde) or ortho formyl carvacrol (2-hydroxy-6-isopropyl-3-methyl- benzaldehyde)) was carried out using a previously reported method [18-20]. In the second step, synthesis of substituted sulfonyl hydrazides (2,4,6-trimethylbenzenesulfonohydrazide and 4-methylbenzenesulfonohydrazide) [19] was carried out in which hydrazine hydrate (0.25 mol, 2.5 equiv.) was added dropwise to a solution of 4-methylbenzene-1-sulfonylchloride or 2,4,6-trimethyl benzene sulfonyl chloride (0.1 mol, 1 equiv..) in THF (100 mL) at 0 °C under inert atmosphere. After stirring for 0 to 5 °C for 30 min, ice-cold ethyl acetate (200 mL) was added to the cooled reaction mixture and the mixture was washed repeatedly with ice-cold 10% aqueous sodium chloride (5 × 150 mL). The organic layer was dried over sodium sulphate at 0 °C, and was then added slowly to a stirring solution of hexane (1.2 L) during 5 min. Substituted benzene sulfonyl hydrazide precipitated as a white solid and was collected by vacuum filtration. The filter cake was washed with hexane (2 × 50 mL) and then dried in vacuo, yielding the substituted sulfonyl hydrazides compound as a white solid. In the third step, the synthesis of phenolic monoterpenoid-based sulfonyl hydrazones [21] was carried out, in which the hydrazone derivatives (N'-(2-hydroxy-6-isopropyl-3-methylbenzylidene)- 4-methylbenzenesulfonohydrazide (PTHC), N'-(2-hydroxy-3- isopropyl-6-methylbenzylidene)-4-methylbenzenesulfonohyd razide (PTHT), N'-(2-hydroxy-6-isopropyl-3-methylbenzylide ne)-2, 4, 6-trimethylbenzenesulfonohydrazide (PMHC), N'-(2- hydroxy-3-isopropyl-6-methylbenzylidene)-2, 4, 6-trimethyl benzenesulfonohydrazide (PMHT)) were prepared by the reaction of equimolar quantities of substituted benzene sulfonyl hydrazide and ortho formyl thymol or ortho formyl carvacrol. Each reactant was dissolved in a minimum amount of ethanol, and then they were mixed, adding 2-3 drops of acetic acid. The reaction mixture was refluxed for 2 h, then cooled to room temperature and poured into ice-cold water. The solid product obtained was collected by filtration and then dried in a drying oven at 70 °C. The product was crystallized from ethanol and dried to obtain the pure product [21]. 2.4. Common procedure for the synthesis of sulfonyl hydrazone based on palladium metal complexes The complexes were prepared by a general procedure, palladium(II) chloride solution in 0.1 M (1 mmol) taken and treated with an equal volume of water. The hot methanolic solution of ligand (2 mmol) was added drop by drop to the hot palladium(II) chloride solution. The reaction mixture was stirred at room temperature for 30 min and then continued with constant reflux for 5 h. The green-coloured precipitated products were collected, washed for several times with water and cold methanol to remove impurities, and dried at room temperature (Scheme 1] [22]. 2.5. Antimicrobial activity The agar well diffusion method was used for the determi- nation of antimicrobial activity of the synthesized compounds against three fungal and three bacterial strains. The fungal strains Aspergillus niger (ATCC 6275), Aspergillus flavus (ATCC 6202), Aspergillus fumigates (ATCC 36606), and bacterial strains Escherichia coli (ATCC 35218), Staphylococcus aureus (ATCC 25923), Bacillus subtilis (ATCC 23857) were obtained from the National Chemical Laboratory, Pune, India. Tadavi et al. / European Journal of Chemistry 11 (4) (2020) 377-384 381 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.377-384.2040 Table 3. Bond angles for palladium complexes. Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) Atom Atom Atom Angle (°) PMHT-Pd(II) complex O111 Pd1 O11 180.0(3) C5 C4 C3 118.1(5) C1 C14 C13 114.3(5) O111 Pd1 N11 88.72(16) C5 C4 C16 120.5(5) C15 C14 C1 110.9(5) O111 Pd1 N111 91.28(16) O11 C2 C3 123.9(5) C15 C14 C13 110.7(5) O11 Pd1 N111 88.72(16) O11 C2 C1 117.2(5) C4 C5 C6 121.7(6) O11 Pd1 N11 91.28(16) C3 C2 C1 118.8(5) C9 C8 S1 118.3(4) N11 Pd1 N111 180.0 C2 C1 C14 118.6(5) C9 C8 C7 121.4(5) N12 S1 C8 103.4(3) C6 C1 C2 118.0(6) C7 C8 S1 119.8(5) O13 S1 N12 102.9(3) C6 C1 C14 123.4(6) C11 C10 C9 121.7(6) O13 S1 C8 110.1(3) N11 C20 C3 127.6(5) C1 C6 C5 123.0(6) O12 S1 N12 110.9(3) N11 N12 S1 113.5(4) C8 C7 C18 126.3(6) O12 S1 O13 118.1(3) C8 C9 C19 124.3(5) C12 C7 C8 116.7(6) O12 S1 C8 110.2(3) C10 C9 C8 118.1(5) C12 C7 C18 117.0(6) C2 O11 Pd1 128.7(4) C10 C9 C19 117.5(5) C11 C12 C7 122.9(6) C20 N11 Pd1 125.2(4) C20 C3 C4 116.6(5) C10 C11 C17 121.0(6) C20 N11 N12 113.5(5) C20 C3 C2 123.2(5) C12 C11 C10 118.9(6) N12 N11 Pd1 121.3(3) C2 C3 C4 120.2(5) C12 C11 C17 120.2(6) C3 C4 C16 121.4(6) PTHC-Pd(II) complex O11 Pd1 O1 180.0 C4 C5 C6 119.4(2) C10 C9 C8 111.2(3) N1 Pd1 O1 90.24(8) C6 C1 C9 121.9(2) C5 C4 C11 119.0(2) N11 Pd1 O12 90.24(8) C2 C1 C6 118.7(2) C3 C4 C5 119.2(3) N1 Pd1 O12 89.76(8) C2 C1 C9 119.3(2) C3 C4 C11 121.8(3) N11 Pd1 O1 89.76(8) C1 C9 C8 113.6(3) C1 C2 C3 121.1(3) N11 Pd1 N1 180.0 C10 C9 C1 110.9(3) C16 C15 C18 120.7(3) N2 S1 C12 106.31(12) C7 C6 C1 118.3(2) C16 C15 C14 118.5(3) O3 S1 N2 105.46(13) C5 C6 C7 121.8(2) C14 C15 C18 120.8(3) O3 S1 C12 108.96(15) C5 C6 C1 119.8(2) C13 C12 S1 119.4(2) O2 S1 N2 103.41(15) N1 C7 C6 126.2(2) C13 C12 C17 120.3(3) O2 S1 O3 121.18(15) N1 N2 S1 113.82(17) C17 C12 S1 119.8(2) O2 S1 C12 110.31(15) O1 C5 C6 125.0(2) C4 C3 C2 121.6(3) C5 O1 Pd1 125.76(15) O1 C5 C4 115.6(2) C14 C13 C12 119.9(3) C7 N1 Pd1 126.01(17) N2 N1 Pd1 119.16(15) C15 C16 C17 121.9(3) C7 N1 N2 114.8(2) C13 C14 C15 120.9(3) C16 C17 C12 118.6(3) PTHT-Pd(II) complex O3 S1 C13 110.00(13) N1 N2 S1 112.72(17) C7 C2 C3 117.6(2) O3 S1 N2 103.53(13) C1 C6 C9 119.0(2) N1 C7 C2 125.6(3) O2 S1 O3 121.67(13) C5 C6 C1 117.5(3) C2 C3 C11 121.6(3) O2 S1 C13 108.95(13) C5 C6 C9 123.4(2) C4 C3 C2 118.5(3) O2 S1 N2 105.22(13) C1 C2 C3 119.5(2) C4 C3 C11 119.9(3) N2 S1 C13 106.23(12) C7 C2 C1 122.8(2) C17 C12 C13 119.8(3) O1 Pd1 O13 180.0 C14 C13 S1 120.2(2) C6 C5 C4 122.5(3) O1 Pd1 N1 89.90(8) C12 C13 S1 119.4(2) C14 C15 C16 121.6(3) O11 Pd1 N13 89.90(8) C12 C13 C14 120.0(3) C12 C17 C16 121.0(3) O11 Pd1 N1 90.10(8) C15 C14 C13 119.3(3) C6 C9 C8 110.4(3) O1 Pd1 N13 90.10(8) O1 C1 C6 116.2(2) C6 C9 C10 114.0(3) N1 Pd1 N13 180.0 O1 C1 C2 123.8(2) C8 C9 C10 111.3(3) C1 O1 Pd1 126.22(16) C6 C1 C2 120.0(2) C3 C4 C5 121.7(3) N2 N1 Pd1 118.84(15) C7 N1 N2 114.9(2) C15 C16 C18 121.0(3) C7 N1 Pd1 126.16(19) C17 C16 C18 120.7(3) C17 C16 C15 118.3(3) PMHC-Pd(II) complex C3 C2 C1 120.2(9) C18 C13 C14 116.4(10) N21 Pd1 N2 180.0 C7 C2 C1 121.7(10) C15 C14 C13 122.6(11) O3 Pd1 N2 91.2(3) C7 C2 C3 118.0(10) C14 C15 C16 118.4(11) O3 Pd1 N24 88.8(3) C2 C3 C4 120.5(9) C14 C15 C20 120.8(12) O31 Pd1 N24 91.2(3) O3 C3 C2 116.0(9) C16 C15 C20 120.7(12) O31 Pd1 N2 88.8(3) O3 C3 C4 123.5(9) C17 C16 C15 122.8(11) O3 Pd1 O34 180.0 C3 C4 C5 119.3(9) C16 C17 C18 117.6(10) C5 C8 C9 104.8(15) C3 C4 C11 120.5(9) C18 C17 C19 124.7(11) C5 C8 C10' 108.0(16) C5 C4 C11 120.2(9) C13 C18 C17 122.1(10) C10 C8 C5 115.9(16) C4 C5 C8 124.7(9) C13 C18 S1 120.1(9) C10 C8 C9 111.9(18) C6 C5 C4 118.0(10) C17 C18 S1 117.8(9) C9' C8 C5 120.6(17) C6 C5 C8 117.2(9) N2 N1 S1 119.8(7) C9' C8 C10' 113(2) C5 C6 C7 122.3(10) C11 N2 N1 117.4(9) N1 S1 C18 102.8(5) C2 C7 C6 121.8(10) C11 N2 Pd1 125.5(7) O2 S1 C18 110.7(5) N2 C11 C4 129.7(10) N1 N2 Pd1 116.6(6) O2 S1 N1 110.1(5) C14 C13 C12 115.9(10) O1 S1 N1 103.4(5) O2 S1 O1 119.3(6) C18 C13 C12 127.7(10) C3 O3 Pd1 128.8(6) O1 S1 C18 109.2(5) 1 -x, 1-y, -z, 2 1-x, -y, -z, 3 -x, 1-y, -z, 4 2-x, -y, -z. Standard solutions of antifungal (Fluconazole, 25 mg/mL) and antibacterial (Ofloxacin, 25 mg/mL) agents were taken as positive control and the negative control used as DMSO. All synthesized complexes were dissolved to prepare stock solutions of 25 mg/mL in DMSO. The bacterial strain culture and fungal spore suspension were adjusted to give a final concentration of 107 cfu/mL. About 25 mL of media (Potato Dextrose Agar) was poured into Petri plates and inoculated with the respective test organisms. Wells 6 mm in diameter were made with a borer in solid agar and loaded with 40 µL of the test compounds. All fungal and bacterial strains were incubated at 28 °C. The average diameter of the inhibition zone surrounding the wells was measured in mm (Tables 5 and 6) [19,23]. 382 Tadavi et al. / European Journal of Chemistry 11 (4) (2020) 377-384 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.377-384.2040 Table 4. Hydrogen bonding for palladium complexes. D-H…A d(D-H) d(H…A) d(D…A) ∠(DHA) Symmetry PMHT-Pd(II) complex N(12)-H(12)...O(11) 0.74(8) 2.24(7) 2.803(7) 134(7) -x, 1-y, -z C(15)-H(15C)...O(11) 0.96 2.57 3.126(8) 117 C(18)-H(18A)...O(12) 0.96 1.92 2.722(10) 139 C(19)-H(19A)...O(13) 0.96 2.40 3.026(9) 122 PTHC-Pd(II) complex N(2)-H(2)...O(1) 0.79(3) 2.20(3) 2.818(3) 136(3) 1-x, -y, -z C(11)-H(11A)...O(1) 0.96 2.24 2.718(4) 109 PTHT-Pd(II) complex N(2)-H(2)...O(1) 0.76(3) 2.24(3) 2.833(3) 136(3) -x, 1-y, -z C(8)-H(8B)...O(1) 0.96 2.58 3.121(4) 116 C(12)-H(12)...O(2) 0.93 2.59 2.941(4) 103 PMHC-Pd(II) complex C(39)-H(39A)...O(4) 0.96 1.90 2.724(15) 142.8 N(1)-H(1)...O(3) 0.85(4) 1.93(8) 2.660(11) 142(10) 2-x, -y, -z N(3)-H(3)...O(6) 0.84(4) 1.90(6) 2.675(10) 152(10) 1-x, -y, 1-z S O OH N N OH S O O H N N OH S O OH N N OH OH N H N O O S Pd PMHT- Pd(II) PMHC-Pd(II)PTHC-Pd(II) PTHT-Pd(II) PMHT PTHC PTHT PdCl2 O N H N O O S O NN H O O S S O O H NN O S O O N H N O Pd PdCl2 PMHC PdCl2 PdCl2 S O O H N N O S O O N H N O Pd S O O H NN O S O O N H N O Pd Scheme 1. Reaction scheme for the synthesis of palladium(II) complexes. Tadavi et al. / European Journal of Chemistry 11 (4) (2020) 377-384 383 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.377-384.2040 Table 5. Comparison of zone of inhibition values (in mm) of palladium(II) complexes and standard drug against different antibacterial strains *. Compound E. coli S. aureus B. subtilis PMHC-Pd(II) 10 6 10 PMHT-Pd(II) 8 12 8 PTHC-Pd(II) 10 16 12 PTHT-Pd(II) 6 4 4 Ofloxacin 30 30 32 * Concentration in 25 mg/mL. Table 6. Comparison of the zone of inhibition values (in mm) of palladium(II) complexes and standard drug against different fungal strains *. Compound A. niger A. flavus A. fumigatus PMHC-Pd(II) 12 16 10 PMHT-Pd(II) 10 14 12 PTHC-Pd(II) 32 30 32 PTHT-Pd(II) 26 24 26 Fluconazole 36 38 36 * Concentration in 25 mg/mL. 3. Results and discussion 3.1. Synthesis and characterization The palladium(II) complexes synthesized by the reaction of PdCl2 salt and ligand in a 1:2 molar ratio. The complexes are less soluble in common organic solvents, like alcohols, acetonitrile, hexane, acetone, and soluble in DMF and chloroform. In the UV- visible spectra, the Pd(II) complexes showed a broad d-d transition band near 450-438 nm assignable to 1A1g→ 1B1g transition for square planar. A relatively strong charge transfer band has been observed in the spectra of all Pd(II) complexes in the region 309-280 nm [24]. The IR spectra of the complexes are related with those of the free ligands to define the coordination sites that may get involved in chelation. The absence of ν(OH) in the IR spectrum of the complex confirms that the ligands are coordinated in its deprotonated form. The very strong C=N stretch for free ligands around 1615-1630 cm- 1, shifted to lower frequency upon coordination of azomethine, in good agreement with data described previously for the related Pd(II) complexes. Another two strong bands at 1585 and 1445 cm-1 compared to the theoretical bands of 1595 and 1500 cm-1, are because of ν(C=C) and a mixture of ν(C=C) and ν(C=N), respectively. The Pd(N2O2) exhibits a band at 3080 cm- 1 due to CH stretch of aromatic rings and the calculated values are 3017-3093 cm-1. The ligands coordinate through nitrogen’s of C=N group and the oxygen’s of C–O is further supported by the appearance of a lower-intensity band in 530-503 cm-1 [25- 28]. 3.2. X-ray crystallographic analysis The single-crystal X-ray crystallographic studies of all complexes are agreed well with the proposed structure of the complexes. The presented structures illustrate that the complexes are formed by the deprotonation of tetradentate sulfonyl hydrazone based ligands (Figures 1-4). The crystal structures indicate that two nitrogen and two oxygen atoms are coordinated to the central palladium ion after elimination of two hydrogens from the ligands and all palladium ions lie on an inversion center and adopt a slightly distorted square planar geometry while the bond lengths and bond angles have to fall within the expected range comparable to reported values [29]. All the structures of complexes adopt the trans configuration with two attached ligands with palladium(II) ion. Pd-O [1.988(4), 1.9811(16), 1.9745(17), 1.964(7) Å] and Pd-N [2.001(4), 1.9809(19), 1.980(2), 1.976(8) Å] bond lengths for all complexes are in the expected ranges [26]. The C-O bond lengths are C(2)-O(11) 1.310(6), C(5)-O(1) 1.319(3), C(1)-O(1) 1.320(3), C(3)-O(3) 1.323(11) Å for PMHT-Pd(II), PTHC-Pd(II), PTHT-Pd(II) and PMHC-Pd(II) complexes, respectively, are longer than the C=O bond distance (1.221 Å) and slightly shor- ter than the C-O bond distance (1.362 Å) [30]. This indicates the existence of electron delocalization over the six-member chelate rings (Pd-O-C-C-C-N) due to the coordination of the oxygen and nitrogen atoms with the palladium(II) ion. In the case of PTHC-Pd(II) and PTHT-Pd(II) complexes, the Pd-N distances for both complexes are 1.9809(19) and 1.980(2) Å which are next to the sum of the covalent radii in ranges of palladium and nitrogen and these confirm signifying strong coordination through the azomethine nitrogen [31]. The values for C=N 1.299(1) Å, C-O 1.319(1) Å, N-N 1.427(6) Å, and S-O 1.427(2) Å for both complexes are near about same. The O-Pd- O and N-Pd-N angles for both complex (PTHC-Pd(II): O(1)- Pd(1)-O(1)i (i 1-x, -y, -z), N(1)-Pd(1)-N(1)i (i 1-x, -y, -z) and PTHT-Pd(II): O(1)-Pd(1)-O(1)ii (ii -x, 1-y, -z), N(1)-Pd(1)-N(1)ii (i -x, 1-y, -z)) are 180°. The torsion angles for both complexes are near close in the series. Both the complexes show the N- H···O and C-H···O type intramolecular hydrogen bonding. In PMHC-Pd(II) and PMHT-Pd(II) complexes, the Pd-N distances are Pd(1)-(N2) 1.976(8) Å and Pd(1)-N(11) 2.001(4) Å, respectively, and the Pd-O bond distances are Pd(1)-O(3) 1.964(7) Å and Pd(1)-O(11) 1.988(4) Å, respectively. Similarly, the C=N double bond distance of C(11)-N(2) and N(11)-C(20) are 1.233(11) and 1.312(7) Å for PMHT-Pd(II) and PMHC-Pd(II) complexes, respectively. The phenolic single bond C-O distances are C(2)-O(11) 1.310(6) Å, and C(3)-O(3) 1.323(11) Å for PMHC-Pd(II) and PMHT-Pd(II) complexes, respectively. The N-N bond length values are N(11)-N(12) 1.416(7) Å and N(1)-N(2) 1.408(12) Å for PMHC-Pd(II) and PMHT-Pd(II) complexes, respectively. The S-O bond lengths for both complexes are near about 1.42(2) Å. The bite angles for both complex O(11)-Pd(1)-N(11) and O(3)-Pd(1)-N(2) are 91.28(16)° and 91.2(3)° for PMHT-Pd(II) and PMHC-Pd(II) complexes, respectively, so the bite angles of the complex deviate slightly from the ideal angle 90°. The PMHC-Pd(II) and PMHT-Pd(II) complexes show the N-H···O and C-H···O type molecular hydrogen bonding [22,32]. 3.3. Antimicrobial activity The PTHC-Pd(II) and PTHT-Pd(II) complexes showed the highest antifungal activity than PMHC-Pd(II) and PMHT-Pd(II) complexes (Table 5). The PTHC-Pd(II) complex possesses the very close significant activity comparable to the standard drug fluconazole against the fungal strains Aspergillus niger, Aspergillus flavus, and Aspergillus fumigatus. Such enhanced activity of metal chelates can be described based on the overtone concept and chelation theory. The chelation considerably decreases the polarity of the metal ion because of the partial sharing of its positive charge with donor groups and possible π-electron delocalization over the whole chelate ring. Such chelation could enhance the lipophilic character of the central metal atom, which subsequently favours its permeation through the lipid layer of the cell membrane. The antibacterial activity of all complexes was investigated by screening them against the Gram-negative Escherichia coli and Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis by agar well 384 Tadavi et al. / European Journal of Chemistry 11 (4) (2020) 377-384 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.377-384.2040 diffusion technique (Table 4). The results showed that all complexes possess lesser antibacterial activity. The PTHC- Pd(II) complex showed antibacterial activity for Gram-positive Staphylococcus aureus as comparable to ofloxacin as a standard drug. The low activity of the compound is attributed to its low cell permeability, the suitability of the particle size of the metal ion, and the bulkier organic moieties [26,33,34]. 4. Conclusions The present work has shown the successful synthesis and spectroscopic characterization of the Pd(II) complex of sulfonyl hydrazone-based ligands which acts as a bidentate ligand. Single-crystal X-ray diffraction technique has shown the possi- bilities of hydrogen bonding and intermolecular interaction and it proves the good agreement with experimental synthesis and coordination sites. Antifungal activity results show that PTHC- Pd(II) complex possesses better activity comparable to the standard drug fluconazole against all selected fungal strains and makes it a good drug. Acknowledgements We are also obliged to Sophisticated Analytical Instrumen- tation Facility, Indian Institute of Technology, Madras and Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, for support in solving the crystal structures of PMHC-Pd, PMHT-Pd(II), PTHC-Pd(II) and PTHT-Pd(II) comp- lexes, respectively. Supporting information CCDC-1888204, 1887978, 1887979 and 1887980 contain the supplementary crystallographic 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 interest: 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 Funding for this research was provided by: SAP DSA- I (Grant No. F.4-6/2015/DSA-I (SAP-II). ORCID Samina Karimkha Tadavi http://orcid.org/0000-0002-2772-0329 Ratnamala Subhash Bendre http://orcid.org/0000-0002-2699-4096 Satish Vittal Patil http://orcid.org/0000-0001-6167-2511 Shubha Gaguna http://orcid.org/0000-0001-7112-958X Jamatsing Darbarsing Rajput http://orcid.org/0000-0002-4588-1345 References [1]. 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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/ https://www.ccdc.cam.ac.uk/structures/ mailto:data_request@ccdc.cam.ac.uk mailto:data_request@ccdc.cam.ac.uk http://orcid.org/0000-0002-2772-0329 http://orcid.org/0000-0002-2699-4096 http://orcid.org/0000-0001-6167-2511 http://orcid.org/0000-0001-7112-958X http://orcid.org/0000-0002-4588-1345 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. Materials and methods 2.2. Single-crystal X-ray diffraction data collection 2.3. Synthesis of ligands 2.4. Common procedure for the synthesis of sulfonyl hydrazone based on palladium metal complexes 2.5. Antimicrobial activity 3. Results and discussion 3.1. Synthesis and characterization 3.2. X-ray crystallographic analysis 3.3. Antimicrobial activity 4. Conclusions Acknowledgements Supporting information Disclosure statement Funding ORCID References PrintField10: PrintField11: PrintField12: PrintField13: PrintField14: PrintField15: PrintField16: PrintField17: PrintField20: PrintField21: PrintField22: PrintField23: PrintField24: PrintField25: PrintField26: PrintField27: