untitled European Journal of Chemistry 8 (3) (2017) 252‐257 European Journal of Chemistry ISSN 2153‐2249 (Print) / ISSN 2153‐2257 (Online)  2017 Atlanta Publishing House LLC ‐ All rights reserved ‐ Printed in the USA http://dx.doi.org/10.5155/eurjchem.8.3.252-257.1598 European Journal of Chemistry Journal webpage: www.eurjchem.com Synthesis, spectral characterization, thermal analysis and DFT computational studies of 2‐(1H‐indole‐3‐yl)‐5‐methyl‐1H‐benzimidazole and their Cu(II), Zn(II) and Cd(II) complexes Jabbar Saleh Hadi 1,*, Zuhair Ali Abdulnabi 2 and Adil Muala Dhumad 1 1 College of Education for Pure Science, Basrah University, Basrah, 61004, Iraq 2 Marine Science Center, Basrah University, Basrah, 61004, Iraq * Corresponding author at: College of Education for Pure Science, Basrah University, Basrah, 61004, Iraq. Tel.: +964.771.0822193. Fax: +964.771.0822193. E‐mail address: jshalkabi2@gmail.com (J.S. Hadi). ARTICLE INFORMATION ABSTRACT DOI: 10.5155/eurjchem.8.3.252-257.1598 Received: 09 June 2017 Received in revised form: 02 July 2017 Accepted: 23 July 2017 Published online: 30 September 2017 Printed: 30 September 2017   Cu(II), Zn(II) and Cd(II) metal complexes were obtained by using ligand (2‐(1H‐indol‐3‐yl)‐5‐ methyl‐1H‐benzo[d]imidazole) derived from 4‐methyl‐1,2‐phenelyenediamine and indole‐3‐ carboxaldehyde. The ligand and its metal complexes were characterized by elemental analysis, Mass Spectrometry, FT‐IR, 1H NMR, 13C NMR, TG and molar conductance measure‐ ments. The non‐electrolytic behaviour of complexes is confirmed by low molar conductance value. The presence of lattice and coordinated water molecules is confirmed by thermal analysis. Thermodynamic parameters (E, ΔH, ΔS and ΔG) were calculated by using Coats‐ Redfern method. The density function theory (DFT) calculation at the B3LYP/LanL2DZ method with 6‐311+G(d,p) basis set are used to investigate the electronic structure of the ligand and their complexes with Cu(II), Zn(II) and Cd(II) metals. HOMO‐LUMO energies of the mentioned compounds have been computed by using DFT/B3LYP calculation method with 6‐ 311+G(d,p) basis set and LanL2DZ basis set for Cu(II), Zn(II) and Cd(II) metal complexes. Mulliken charge distributions of the investigated compounds were also computed with same level of method. KEYWORDS Metal complex Benzamidazole Indol carboxaldehyde HOMO‐LUMO energies Coats‐Redfern method Density function theory Cite this: Eur. J. Chem. 2017, 8(3), 252‐257 1. Introduction The benzimidazole is as a class of heterocyclic compound, consisting of a benzene ring fused to an imidazole ring [1‐3]. There are different methods of preparing them using various reagents such as, carboxylic acid, esters, amides, aldehydes etc., when reacted with o‐phenylenediamine and their deriva‐ tives, afforded the benzimidazoles. Methods of benzimidazoles synthesis from the condensation of 1,2‐phenylenediamine with aromatic aldehydes under oxidative condition are simple and efficient method and the reactions give high yields in short time and easy in isolation. The reaction carried out in air under reflux or in room temperature in presence an oxative reagent such as H2O2 [3], Pb(OAC)2 [4], or in presence a catalyst such as cupric acetate [5]. The complexes of transition metals with benzimidazole have been extensively studied due to the ability of benzimidazoles as excellent N‐donor ligands [6]. Most of benzimidazoles possess antibacterial, fungicide, antihelmintic and antitumor activity [7]. The numbering system for benzimidazoles is given in Scheme 1 [3]. Substi‐ tution at 2 position of benzimidazole ring is very important for their pharmacological effect [8]. Scheme 1 2. Experimental 2.1. Apparatus FT‐IR spectra were recorded in the range 4000‐500 cm‐1 using KBr disc on Shimadzu FT‐IR 8400S spectrometer. 1Hand 13C NMR spectra were recorded on Bruker 400 spectrometer (400 MHz for 1H NMR and 100 MHz for 13C NMR) using DMSO‐ d6 as a solvent and TMS as an internal reference. Mass spectrum for the ligand was recorded on Agilent Technologies‐ 5975C (EI, 70 eV). The thermal analyses (TG and DTG) were carried out in dynamic nitrogen atmosphere (20 mL/min) with a heating rate of 10 °C/min using a Perkin‐Elmer thermal analyzer. Hadi et al. / European Journal of Chemistry 8 (3) (2017) 252‐257 253 Scheme 2 The TLC type silica gel 60F254 was used to monitor the reaction and the spots were visualized by UV lamp Black‐Ray‐ B‐100A. Molar conductance of the freshly prepared solutions (1×10‐3 M in DMSO) was measured at room temperature using W.T.W‐Conductivity meter. The metal content of the prepared complex was found by a Buck 210 BGP model atomic absorption spectrometer after digestion in nitric acid. Elemental analyses for C, H and N were performed using a Leco CHNS‐932 Analyzer. 2.2. Materials and methods 2.2.1. Material 4‐Methyl‐1,2‐phenelyenediamine from Merck and used after recrystallization from hexane. Indol‐3‐carboxaldehyde from Himedia and used as supplied various metal (II) acetate were of Fluka, all other solvents are of analytical grade. 2.2.2. Synthesis 2.2.2.1. Synthesis of ligand, 2‐(1H‐indol‐3‐yl)‐5‐methyl‐1H‐ benzo[d]imidazole An ethanolic solution (15 mL) of 5 mmole (0.725 g) of indole‐3‐carboxaldehyde and ethanolic solution (10 mL) of 5 mmole (0.61 g) of 4‐methyl‐1,2‐phenelyene diamine mixed and refluxed in presence of 2 drops of concentrated sulphuric acid [2] for 2h with continuous stirring. The orange precipitate which separated filtered hot and washed with hot ethanol and then with ether several times and dried at 70 °C in oven. The crude product was recrystallized from DMF:H2O (1:10, v:v). Color: Reddish orange. Yield: 70%. M.p.: 235‐237 °C. FT‐IR (KBr, , cm‐1): 3400 (N‐H, Benz.), 3128 (N‐H, Indole), 3047 (Ar‐H), 2920, 2866 (CH3), 1633 (C=N). 1H NMR (400 MHz, DMSO‐d6, δ, ppm): 2.30 (s, 3H, CH3), 7.05‐8.33 (m, 8H, Ar‐H), 11.00 (s, 1H, NH‐indole), 11.86 (s, 1H, NH‐imidazole). 13C NMR (100 MHz, DMSO‐d6, δ, ppm): 149.50 (C16), 136.29 (C2), 135.99 (C10), 133.71 (C14), 130.22 (C11), 126.16 (C3), 125.98 (C7), 125.51 (C13), 122.22 (C6), 121.31 (C4), 120.13 (C5), 118.74 (C9), 118.18 (C12), 111.62 (C1), 105.22 (C8), 21.19 (C15). MS (EI, m/z (%)): 247.2 (M+, 100). Anal. calcd. for C16H13N3: C, 77.71; H, 5.30; N, 16.99. Found: C, 77.63; H, 5.44; N, 17.04 %. 2.2.2.2. Synthesis of [Cu(L)H2O.CH3COO].H2O (LCu) Ethanolic solution (20 mL) of 1 mmole (0.247 g) of ligand was add to a hot ethanolic solution (20 mL) of Cu(CH3COO)2 (0.199 g). The resulting mixture color change immediately to black and then refluxing for 3 h., the precipitate was filtered and washed with hot ethanol several time, then dried to afford green powder. Color: Green. Yield: 72%. M.p.: > 300 °C. FT‐IR (KBr, , cm‐1): 3400 (N‐H, Benz.), 1616 (C=N). Anal. calcd. for C18H19N3O4Cu: C, 53.39, H, 4.73, N, 10.38, Cu, 15.69. Found: C, 51.97; H, 4.87; N, 10.69; Cu, 16.43%. Λm (S.m2.mol‐1): 6.1. 2.2.2.3. Synthesis of [Zn(L)H2O.CH3COO] (LZn) Ethanolic solution of 1 mmole (20 mL) of ligand and a hot ethanolic solution of 1 mmole Zn(CH3COO)2 (0.219 g) was refluxed for 6 h, the precipitate was filtered and washed with hot ethanol several time. The brown precipitate was collected and dried. Color: Brown. Yield: 45%. M.p.: >300 °C. FT‐IR (KBr, , cm‐1): 3400 (NH, Benzimidazole), 1627 (C=N). Anal. calcd. for C18H21N3O5Zn: C, 50.90; H, 4.98; N, 9.89; Zn, 15.39. Found: C, 49.47; H, 5.13; N, 10.18; Zn, 16.07%. Λm (S.m2.mol‐1): 3.2. 1H NMR (400 MHz, DMSO‐d6, δ, ppm): 11.63 (s, 1H, NH‐ benzimidazole), 8.72‐6.97 (m, 8H, Ar‐H), 2.35 (s, 3H, CH3). 2.2.2.4. Synthesis of [Cd(L)H2O.CH3COO] (LCd) Ethanolic solution of 1 mmole of ligand and a hot ethanolic solution of Cd(CH3COO)2 1 mmole (0.266 g) was refluxed for 4 h and the mixture filtered hot, the precipitate washed with hot ethanol and the obtained solid dried. Color: Brown. Yield: 37%. M.p.: > 300 °C. FT‐IR (KBr, , cm‐1): 3400 (NH, benzimi‐dazole), 1621 (C=N). Anal. calcd. for C18H19N3O4Cd: C, 47.64; H, 4.22; N, 9.26;Cd, 24.77. Found: C, 46.22; H, 4.34; N, 9.51; Cd, 24.81%. Λm (S.m2.mol‐1): 4.6. 2.2.3. Computational details All computations were performed using the Gaussian09 software package [9]. Full geometry optimizations were carried out using the Density Function Theory at B3LYPlevel for studied ligand and their Cd(II), Cu(II) and Zn(II) complexes [10,11]. LANL2DZ is a basis set for post‐third‐row atoms which uses effective core potentials in order to reduce computational cost [12]. Properties and HOMO‐LUMO energies of the ligand and their complexes was calculated by the LanL2DZ basis set for the Cd, Cu and Zn atoms and the 6‐ 311+G(d,p) higher basis set level for N, O, C and H atoms. Mulliken charge distributions of the investigated compounds were also computed at same level of method. 3. Results and discussion 3.1. Characterization of ligand The benzimidazole ligand, 2‐(1H‐Indol‐3‐yl)‐5‐methyl‐1H‐ benzo[d]imidazole, was formed according to the mechanism of Scheme 2. The ligand insoluble in hexane, benzene, toluene, diethyl ether and chloroform; sparingly soluble in methanol and ethanol and very soluble in DMSO and DMF. The ligand exhibits two bands for νN‐H the first is a strong and a broad at 3400 cm‐1 attributed to νN‐H of benzimidazole moiety [13,14], the second at 3128 cm‐1 weak and broad attributed to νN‐H of indole moiety. The weak band at 3047 cm‐1 attributed to νC‐H aromatic and the bands at 2920 and 2866 cm‐1 attributed to νC‐H asym and sym stretching of CH3 group. The strong band at 1633 cm‐1 attributed to νC=N stretching mode. The mass spectrum confirms the proposed formula where the molecular ion peak (100%) at 247.2 m/z, which is fit the molecular weight and the high relative abundance gives an idea of the stability of molecular ion (Figure 1). The 1H NMR spectrum of ligand shows a signal at δ 11.86 ppm attributed to NH proton of benzimidazole moiety [14,15], another single signal at δ 11.00 ppm attributed to NH proton of indole moiety [16,17]. 254 Hadi et al. / European Journal of Chemistry 8 (3) (2017) 252‐257 Figure 1. The mass spectrum of ligand. Figure 2. The 1H NMR‐d6 spectrum of ligand. Figure 3. The 13C NMR spectrum of ligand. The aromatic protons appear in the expected region as multiples signals in the range δ 7.05‐8.33 ppm. The methyl protons appear as a singlet signal at δ 2.30 ppm. The 1H NMR spectrum of ligand as shown in Figure 2. The 13C NMR spectrum shows a signal at δ 21.19 ppm attributed to methyl carbon and a signal at δ 149.5 ppm to C=N (Figure 3) [18]. All signals attributed to aromatic carbon are listed experimental section together with the numbering system of the ligand. 3.2. Characterization of the metal complexes The Zn(II), Cu(II) and Cd(II) complexes are stable, non‐ hygroscopic and having high melting points (>300 °C). These complexes are insoluble in common organic solvent but they soluble in DMF and DMSO except Cd(II) complex also insoluble in DMSO. The elemental analysis CHN and the metal ratio in the complexes are in agreement with suggested formula which indicates that the ligand associates with metal (ions) in 1:1 molar ratio. The molar conductance measurements indicate their non‐electrolytic nature. To elucidation the site of binding between ligand and metal ions, IR spectroscopy gives good evidence when com‐ pared the IR spectrum of ligand with IR spectra of complexes, the band at 3400 cm‐1 which attributed to stretching vibration of N‐H (benzimidazole) in free ligand, this remain unchanged in the complexes spectra, indicating that this group in not participating in coordination but the band at 3128 cm‐1 which attributed to N‐H of indol moiety in free ligand is totally disappearance. This data is suggested that the deprotonation and participating through the nitrogen atom of indole. The band at 1633 cm‐1 which attributed to C=N in free ligand is shifted to a lower wave number side (∆ν = 6‐17 cm‐1) in all complexes indicates the participation of the C=N group in coordination to the metal ions through the lone pair of electrons on the nitrogen atom [17]. The 1H NMR spectrum of Zn complex (diamagnetic) (Figure 4) when compared with the ligand spectrum, shows only the signal of benzamidazole N‐H at δ 11.63 ppm which Hadi et al. / European Journal of Chemistry 8 (3) (2017) 252‐257 255 Table 1. Kinetic parameters of the complexes using the Coats‐Redfern equation. r2ΔG(kJ/mol) ΔS(kJ/mol.K)ΔH (kJ/mol)E (kJ/mol) A (1/s) Step Compound 0.937109.469 ‐0.244419.51822.5781.307891st [Cu(L)H2O.CH3COO].H2O 0.945 157.319 ‐0.2046 47.234 51.707 2.2971×1022nd 0.917177.180 ‐0.234239.46844.3567.151073rd 0.944287.944 ‐0.1341159.444167.4091.9666×106 4th 0.949 111.267 ‐0.2631 13.129 16.230 0.14027 1st [Zn(L)H2O.CH3COO] 0.959158.006 ‐0.206749.89754.2451.7367×102 2nd 0.977221.018 ‐0.1374115.608121.6199.9223×105 3rd 0.966109.760 ‐0.218928.09631.19728.45531st [Cd(L)H2O.CH3COO] 0.980 134.777 0.0600 163.501 167.475 1.372×1016 2nd 0.956174.745 ‐0.29407.743612.4665.187×10‐3 3rd 0.949219.254 ‐0.173195.818101.7461.3452×104 4th indicated that this group not participation in complex formation while the signal at δ 11.00 ppm in ligand spectrum which attributed to NH proton (indole moiety) is totally absent in the complex spectrum which indicated the deprotonation of NH group and subsequently the replacement of proton by metal. Figure 4. The 1H NMR spectrum of Zn complex. 3.3. Thermal degradation 3.3.1. Thermal degradation of [Cu(L)(H2O)(CH3COO)].H2O The TG/DTG curve of the [Cu(L)(H2O)(CH3COO)].H2O shows the four steps decomposition. The first step in the range 50‐125 °C (DTGmax = 95 °C) with mass loss 4.93% (theoretical 4.45%) which indicates the presence of one lattice water molecule. The second step with mass loss 4.89% (theoretical 4.66%) which attributed to one coordinated water molecule [19]. The third and fourth steps take place in fast rate (Figure 5) starting from 275 °C to the final temperature 800 °C. The residual part 28%, may be attributed to the CuO polluted with carbon [19,20]. Figure 5. TG/DTG curve of copper complex. 3.3.2. Thermal degradation of [Zn(L)(H2O)(CH3COO)].2H2O The TG/DTG curve of the zinc complex shows three steps of degradation, the first step 8.49% (theoretical 8.49%) weight loss in the range 50‐169 °C corresponds to two lattice water molecules [20]. The second step in the range 185‐345 °C with mass loss 20.2% (theoretical 20.1%) which represent the loss of both acetate and coordinated water together. The last step begin at 350 °C and end at 600 °C to afford the final degradation of ligand and the final product is ZnO 19.72% (theoretical 19%) [19,20]. 3.3.3. Thermal degradation of [Cd(L)(H2O)(CH3COO)].H2O The TG/DTG curve of the cadmium complex shows four steps decomposition and similar to the Cu complex, where the first step 50‐150 °C (DTGmax = 100 °C) with mass loss 3.83% (theoretical 3.97%) which indicated the presence of one lattice water molecule [20]. The second and third steps in the range 170‐410 °C with total mass loss 17.77% (theoretical 17.93%) equivalent to one coordinated water molecule and acetate. The fourth step starting from 415 to 800 °C and the final residue 27.85% (theoretical 28.25%) which indicated that the final product is cadmium (II) oxide. 3.4. Kinetic and thermodynamic analysis The thermal dehydration and decomposition of the complexes were studied using Coats‐Redfern method [20,21]. 2 Wf log A×R 2×R×T EWf‐Wtlog =log 1‐ ‐ T θ×E E 2.303×R×T                  (1) where Wf and Wt are weight at the end step and at any temperature, respectively; E, activation energy; R, Gas constant (8.314×10‐3 kJ/mole); Ɵ, heating rate and A, pre‐ exponential factor. The decomposition steps of all complexes show a best fit for first order in all steps. The correlation coefficient (r2) was computed using the least square method by plotting the left hand side of Coats‐Redfern equation versus 1000/T (Figure 6). The activation energy and the exponential factor were calculated from the slope and intercept, respectively. ∆H, ∆S and ∆G for all steps were calculated by using the Equation (2‐4). ΔH = ΔE – R×T (2) ΔS = R × ln (A×h/KB×TS) (3) ΔG = ΔH – T×ΔS (4) whereas, h, Planck constant (6.6262×10‐34 J.s);KB, Boltzman constant (1.3806×10‐23 J/K) and TS (Tmax from DTG curve). The thermokinetic data are summarized in Table 1. From this result, the high activation energy for all complexes indicated the high stability of the complexes. In general, the activation energy of the second steps are higher than first step, this indicated that the dehydrated complexes are more stable, in addition the positive value of ∆H means that the decompo‐ sition process are endothermic. The negative values of ∆S indicated that the complexes more ordered than the reactants. All values of ∆G are positive which indicate that all steps are non‐spontaneous [20]. 256 Hadi et al. / European Journal of Chemistry 8 (3) (2017) 252‐257 Table 2. Selected bond lengths and angles for ligand and (Cd, Cu and Zn) complexes from the B3LYP and (B3LYP/LANL2DZ/6‐311+G(d,p) basis set) calculations. Parameters [Cd(L).H2O.CH3COO] [Cu(L).H2O.CH3COO].H2O [Zn(L).H2O.CH3COO] L Calc. Exp. Calc. Exp. Calc. Exp. [22‐24] Calc. Exp. Bond lengths (Å) M‐N25 2.242 2.226 1.916 1.982 2.023 2.037 ‐ ‐ M‐N13 3.503 ‐ 4.515 ‐ 3.581 ‐ ‐ ‐ M‐O37 2.165 ‐ 1.991 ‐ 2.122 2.111 ‐ ‐ M‐O32 2.200 ‐ 1.982 ‐ 2.025 ‐ ‐ ‐ N25‐C26 1.368 1.365 1.382 1.368 1.368 1.370 1.317 ‐ N25‐C14 1.381 1.367 1.397 1.367 1.389 1.360 1.383 ‐ N13‐C12 1.367 1.325 1.332 1.329 1.371 1.320 1.372 ‐ C11‐C26 1.432 ‐ 1.412 ‐ 1.433 ‐ 1.450 ‐ C11‐C12 1.455 ‐ 1.461 ‐ 1.421 ‐ 1.376 ‐ C11‐C3 1.436 ‐ 1.462 ‐ 1.451 ‐ 1.447 ‐ Bond angle (°) C14‐N25‐M 146.23 133.60 122.56 131.80 133.13 130.30 ‐ ‐ C26‐N25‐M 104.94 119.20 130.36 117.50 119.06 121.10 ‐ ‐ C26‐N25‐C14 107.30 107.30 107.009 107.10 107.46 107.70 105.60 ‐ Figure 6. Coats‐Redfern [Cu(L)H2O.CH3COO].H2O step1st.. 3.5. Computational results 3.5.1. Geometrical optimization The visualization of the optimized geometrical structure and atomic labeling of [Cd(L)H2O.CH3COO] complex calculated by the B3LYP/LanL2DZ method with 6‐311+G(d,p) basis set are given in Figure 7. Figure 7. Optimized structures of [Cd(L).H2O.CH3COO] complex calculated by the B3LYP/LanL2DZ method with 6‐311+G(d,p) basis set with atom numbering. The optimized geometric parameters are listed in Table 2. The crystallographic structures of 2‐(1H‐indol‐3‐yl)‐5‐methyl‐ 1H‐benzo[d]imidazole and their Cu(II), Zn(II) and Cd(II) comp‐ lexes is not available in the literature, therefore we compared some bond lengths and bond angles with X‐ray diffraction data of M‐N and N‐C as a general. The optimized bond lengths and bond angles of title ligand and complexes are in good agreement with X‐ray data [22‐24]. N25‐C26 in L‐Zn complex is shorter and C25‐N14 is longer than as expected (1.368 and 1.389 Å, respectively). The angles C14‐N25‐M and C26‐N25 were calculated as 146.23° and 104.94° for Cd complex, while the corresponding angles for Cu and Zn complexes are 122.56° and 130.36° and 133.13°, 119.06°, respectively. 3.5.2. Mulliken population analysis Dipole moment, molecular polarizability and bond proper‐ ties are affected by atomic charges, therefore, the Mulliken atomic charge calculation has an important role in quantum chemistry [25‐27]. Mulliken population analysis was perfor‐ med using DFT/B3LYP calculation method with 6‐311+G(d,p) basis set and LanL2DZ basis set for Cu(II), Zn(II) and Cd(II) metal complexes. Graphical reorientations of Mulliken charge distributions of ligand and L‐Cd, L‐Cu, L‐Zn complexes is shown in Figure 8. As can be seen in Table 3, all the hydrogen atoms have a net positive charge. The obtained atomic charge shows that the Cu atom of [Cu(L)(H2O)(CH3COO)].H2O has lower positive atomic charge (0.494) than the Cd and Zn atoms in the other studied complexes [Cd(L)(H2O)(CH3COO)].H2O and Cd(L)(H2O)(CH3COO)].H2O which obtained 1.032 and 1.033, respectively. The N23 atom has negative atomic charge ‐0.067, ‐0.416, ‐0.428 and ‐0.439 of ligand, Zn, Cd and Cu complexes, respectively. Figure 8. Graphical reorientations of Mulliken charge distributions of ligand L and LCd, LCu, LZn complexes. 3.5.3. Total energies, dipole moments and molecular orbitals analysis The HOMO energy represents the ability to donate an electron, LUMO energy as an electron acceptor represents the ability to obtain an electron [28]. The HOMO‐LUMO energy calculations of the title compounds were performed using DFT/B3LYP method with 6‐311+G(d,p) basis set for the ligand and DFT/B3LYP methods with LanL2DZ basis sets for its Cd, Cu and Zn complexes. Furthermore, the orbital shapes (HOMO‐ LUMO) and the energy gap between the HOMO‐LUMO which is a critical parameter to determine molecular electrical transport properties [29] were plotted in 3‐dimensional (3D) by using at B3LYP/6‐311+G(d,p) and B3LYP/ LanL2DZ levels, respectively, are given in Figure 9. The values of the calculated energies, dipole moment and frontier molecular orbital energies of ligand and Cd, Cu and Zn complexes from the B3LYP and B3LYP/LANL2DZ/6‐311+G(d,p) basis set calcula‐ tions are given in Table 4. Hadi et al. / European Journal of Chemistry 8 (3) (2017) 252‐257 257 Table 3. The Mulliken atomic charge distribution of ligand L and LCd, LCu, LZn complexes. Atoms Mulliken atomic charges (Q/e) Atoms Mulliken atomic charges (Q/e) L LCd LCu LZn L LCd LCu LZn 1 C ‐0.418 ‐0.328 ‐0.324 ‐0.333 22 H 0.104 0.232 0.233 0.232 2 C ‐0.676 ‐0.026 ‐0.020 0.023 23 N ‐0.067 ‐0.428 ‐0.439 ‐0.416 3 C 0.872 0.197 0.203 0.224 24 H 0.266 0.333 0.326 0.334 4 C ‐0.794 ‐0.406 ‐0.339 ‐0.411 25 N ‐0.146 ‐0.393 ‐0.393 ‐0.481 5 C ‐0.305 ‐0.231 ‐0.258 ‐0.233 26 C ‐0.189 0.238 0.236 0.250 6 C ‐0.233 ‐0.223 ‐0.211 ‐0.229 27 C ‐0.435 ‐0.770 ‐0.767 ‐0.770 7 H 0.111 0.238 0.251 0.237 28 H 0.155 0.215 0.216 0.214 8 H 0.106 0.207 0.181 0.202 29 H 0.136 0.212 0.218 0.215 9 H 0.122 0.210 0.219 0.209 30 H 0.151 0.218 0.219 0.219 10 H 0.125 0.213 0.225 0.212 31 Cd, Cu, Zn 1.032 0.494 1.033 11 C 0.646 0.098 0.176 0.105 32 O ‐0.832 ‐0.800 ‐0.814 12 C 0.048 ‐0.601 ‐0.404 ‐0.567 33 H 0.454 0.451 0.418 13 N ‐0.120 ‐0.071 ‐0.065 ‐0.241 34 C 0.358 0.400 0.387 14 C ‐0.049 0.165 0.217 0.185 35 O ‐0.438 ‐0.446 ‐0.479 15 C ‐0.629 ‐0.563 ‐0.524 ‐0.554 36 H 0.394 0.389 0.451 16 C 0.666 0.503 0.484 0.501 37 O ‐0.495 ‐0.462 ‐0.459 17 C ‐0.412 ‐0.336 ‐0.320 ‐0.336 38 C ‐0.669 ‐0.690 ‐0.695 18 C ‐0.041 ‐0.355 ‐0.354 ‐0.355 39 H 0.235 0.229 0.237 19 C 0.336 0.214 0.243 0.225 40 H 0.229 0.230 0.235 20 H 0.109 0.239 0.248 0.251 41 H 0.231 0.225 0.237 21 H 0.118 0.228 0.231 0.228 42 H 0.267 0.266 0.306 Table 4. Calculated energies, dipole moment and frontier molecular orbital energies of ligand and Cd, Cu and Zn complexes from the B3LYP and B3LYP/LANL2DZ/6‐311+G(d,p) basis set calculations. Compounds HOMO (eV) LUMO (eV) ΔEH‐L (eV) Dipole (Debye) E [RB3LYP] (a.u.) L ‐0.20202 ‐0.04371 ‐0.15831 5.1212 ‐782.006 LCd ‐0.19029 ‐0.06039 ‐0.12990 6.5635 ‐1134.090 LCu ‐0.19160 ‐0.05127 ‐0.14033 5.2374 ‐1151.646 LZn ‐0.20637 ‐0.04409 ‐0.16228 5.1698 ‐1282.169 Figure 9. Frontier molecular orbitals and the energy gap between the HOMO‐LUMO by using at B3LYP/6‐311+G(d,p) and B3LYP/ LanL2DZ levels of ligand L and LCd, LCu, LZn complexes. The values found for HOMO energy levels are ‐0.20202, ‐0.19029, ‐0.19160 and ‐0.20637eV of ligand, LCd, LCu and LZn complexes, respectively. The LUMO energy level ‐0.04371, ‐0.06039, ‐0.05127 and ‐0.04409 eV of ligand, LCd, LCu and LZn complexes, respectively. References [1]. Walia, R.; Hedaitullah, M.; Naaz, S. F.; Iqbal, K.; Lamba, H. Int. J. Res. Pharm. 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