Synthesis, structural and theoretical studies on new morpholino acetamide ligand and rare earth metal complexes and corrosion Inhibition Effect

doi:10.21203/rs.3.rs-1679269/v1

A series of new complexes of the general formula [Ln(H₂L)Cl₂]Cly.4H₂O (Ln = Er and Ta) and [Yb(H₂L)(H₂O)₂]Cl₃, H₂L = N,N'-((ethane-1,2-diylbis(sulfanediyl))bis(2,1-phenylene))bis(2-morpholinoacetamide) are synthesized and characterized. The physical properties of these complexes are investigated including melting point, color, and percent yield. At room temperature, complexes exhibit similar solution absorption spectra in the UV–Vis region. As shown by thermal analysis, the complexes lose water molecules first, then anions, and finally ligand molecules, leaving a metal oxide residue. The complexes were resulted from monomolar coordination of neutral tetradentate ligand through the amide nitrogen and sulfur, with octahedral geometries. Ligand and its Ta(V) complex are structurally characterized by X-ray powder diffraction. Their optical band gaps demonstrated the ligand and complexes have semiconducting property. Aluminum alloys (AlSi) corrosion inhibition was investigated in 1 M HCl using potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). The inhibition efficiency was 96.36% at 500 ppm inhibitor in 1 M HCl.. Multiple bonding patterns were discovered in molecular docking simulations of the drugs against SARS-CoV-2 (6Y84) and E. coli DNA gyrase (5MMN). The binding energy of complexes revealed active compounds capable of inhibiting SARS-CoV-2 and E. coli DNA gyrase. The antioxidant activity of the ligand and its Ln-complexes was investigated, yielding some surprising results.

Finally, it is worthy to note that, the biochemical outcomes revealed that these complexes may be promising antibacterial agents.

Lanthanide

antimicrobial activity

antioxidant activity

X-ray diffraction

Density Functional Theory (DFT)

Corrosion inhibition

Electrochemical

Aluminum alloys

Heterocyclic compounds are the most prevalent type of organic chemical, containing nitrogen, Sulphur, or oxygen atoms together with carbon. They are abundant in nature, plus highly significant biological substances, such as nucleic acids, vitamins, antibiotics, hormones, pigments, and alkaloids, are heterocyclic compounds. Furthermore, heterocyclic compounds come in a wide range of properties, and approximately of them be able to employ as medications, insecticides, herbicides, dyes, or plastics. Morpholine has the chemical formula NH(CH₂CH₂)₂O. and is a typical six-membered aliphatic heterocyclic molecule. It has a heterocyclic ring, which is found in a variety of biological and pharmacological substances.[1]

Amides functional groups are found in a range of synthetic, medicinally important molecules and biologically active natural products, including peptides, polymers, and anti-inflammatory compounds and so forth .[2][3][4][5][6]The enormous effort that has gone into developing synthetic methods for amide compounds demonstrates the relevance of these molecules.

It is well known that many acyclic diamide ligands have a strong ion selectivity for lithium over sodium and other alkali metal ions.[7][8] Furthermore, adding an amide linkage to a polyether crown compound has been shown to change the binding characteristics of the compound, favoring alkali and alkaline earth metal cations, because the amide linkage provides two possible binding atoms: nitrogen and oxygen. [9][10][11]

Lanthanide complexes are used in medicine as magnetic resonance imaging (MRI) contrast agents and as radiotherapeutic medicines. Lanthanide complexes by organic ligands have obtained use in electroluminescent devices and diodes, lasers, cathode ray tubes, sensors, dosimeters, biological fluoro immunoassays, organic light emitting diodes (OLEDS), imaging agents, display applications, decoration purposes, and telecommunication because of their catalytic, magnetic, and luminescent properties. Various types of organic ligands have been used to create and manufacture lanthanide complexes with desired functionalities. Furthermore, lanthanides play an intriguing, but poorly understood, biological role as trace components in living organisms. [12]

The chemistry of lanthanide coordination has gotten a lot of attention recently. Their unique and unusual molecular structures can be used in a range of techniques, including biological research, catalysis, luminescence, and magnetism, demonstrating the importance and potential utility of this field of study.[13]

Tantalum is the chemical 'twins' of the vanadium triad of the periodic table, and their near-identical physical and chemical qualities make them infamously hard to isolated from one another and from their naturally happening ores. The lanthanide contraction of the elements, as well as their identical ionization energies, have been attributed to this parallelism in behavior [14].

Titanocene dichloride, butotitane and related titanium compounds have reached up to second stage clinical trials. Adverse effects during these trials were the early decomposition of the products in the serum, their low solubility in the nearly neutral aqueous environment, and the inability to fully determine the mechanism of their biological action.[15]

Heterocyclic compounds come in a wide range of properties, and some of them can be utilised as medications, insecticides, herbicides, dyes, and anticorrosion agents [16][17]. Morpholine has the chemical formula NH (CH₂CH₂)₂O and is a typical six-membered aliphatic heterocyclic molecule, which is found in a variety of biological, pharmacological, and anticorrosion chemicals. Acid solutions, such as hydrochloric acid and sulfuric acid, are commonly used to remove rust and scale from gas and oil pipelines, boilers, storage tanks, and condenser tubes, although they can cause major corrosion in metal-based equipment [18][19]. Acid anti-corrosion inhibitors are now routinely utilized to minimize metal dissolving rates[16] [17]. Morpholine used to inhibition the corrosion for iron, brass and aluminum in aggressive media [20][21][22].

In light of the foregoing facts, and in order to maintain our interest in this subject. [8][23] Metal ions are crucial for plants, animals, and humans to live an extended and healthy survival. Their essential function in biological systems has extensive been recognized. They are needed for life to survive, and their lack can result in growth problems, severe dysfunction, cancer, or death. Catalysis, materials production, photochemistry, and biological systems all advantage from transition metal complexes. For the development of new medications, medicinal inorganic chemistry can take advantage of the features of metal ions. Metals and their salts have been used for medical purposes throughout history.Now we are occupied in a project focused towards the synthesis of novel acyclic diamides containing two soft donor sulfur atoms as well as two morpholine moieties aiming at studying its lanthanide complexes as example of rare earth metals. The primary goal of the present research is to study detailed bulk compositions of morpholino acetamide ligand and complexes through the thermal and spectral behavior of the synthesized complexes. Antimicrobial and antioxidant properties in vitro were also studied. Docking tests were also carried out to see how the synthesized chemicals interacted with SARS-CoV-2 (6Y84) and E. coli DNA gyrase (5MMN).The synthesized morpholine ligand was tested as anticorrosion inhibitor in acid medium and promising results were found.

Materials and Chemicals

Aluminum silicon alloys (AlSi) have the following chemical composition (wt. %): Si-9.89, Fe-1.10, Cu-1.99, Mn-0.22, Cr-0.037, Zn-2.44, Ca-0.004, Ni-0.269 and Al-balance was used in the experiments. The corrosive acidic solution is 1 M HCl which was prepared from HCl (37%, AR grade) supplied by Merck using deionized water. The concentration range of the corrosion inhibitor is from 100 ppm to 500 ppm.

Instruments

Sigma-Aldrich, Fluka, and Merck provided spectroscopic level reagents and solvents. As mentioned in our earlier work, we had used all of the apparatus.[24][25][26] AlSi, saturated calomel electrode (SCE), and a platinum wire were used as working, reference, and counter electrodes, respectively, in a three-electrode electrochemical cell. The corrosion inhibition behavior was investigated using electrochemical techniques such as PP, and EIS.

PP was measured at a 5 mV/s scan rate. The corrosion current was calculated using the Stern-Geary method. The inhibition efficiency (IE_PP) and θ were estimated using i_corr as follows:

$${\text{I}\text{E}}_{\left(PP\right)}={\theta }\times 100=\left(1-\frac{{\text{I}}_{\text{c}\text{o}\text{r}\text{r}\left(\text{i}\text{n}\text{h}\right)}}{{\text{I}}_{\text{c}\text{o}\text{r}\text{r}\left(\text{f}\text{r}\text{e}\text{e}\right)}}\right)\times 100 \text{E}\text{q}. \left(1\right)$$

EIS was documented at an open-circuit voltage (OCV) with a modest alternating voltage (10 mV) spanning the frequency range of 100 kHz–20 mHz after immersing the electrode in the test for 1 hour at 25 ^oC. Inhibition efficiency (IE_(EIS)), and θ were calculated from the following Eq. 2 [27]:

$${\text{I}\text{E}}_{\left(\text{E}\text{I}\text{S}\right)}={\theta }\times 100=\left[\frac{{\text{R}}_{\text{c}\text{t}\left(\text{i}\text{n}\text{h}\right)}-{\text{R}}_{\text{c}\text{t}\left(\text{u}\text{n}\text{h}\right)}}{{\text{R}}_{\text{c}\text{t}\left(\text{i}\text{n}\text{h}\right)}}\right]\times 100 \text{E}\text{q}. \left(2\right)$$

R_ct(inh) and R_ct(unh) are charge transfer resistances in the presence and absence of an inhibitor, respectively.

Gamry 3000 potentiostat/galvanostat/ZRA was used to measure these approaches, and Echem Analyst 7 was used to interpret the data.[16][18][17][28]

Antioxidant assays

The antioxidant activity of the extract was measured in triplicate at Al-Azhar University's Regional Center for Mycology and Biotechnology (RCMB) using the DPPH free radical scavenging test, with average values used.

DPPH Radical Scavenging Activity

A newly manufactured (0.004% w/v) methanol solution of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was prepared and kept in the dark at 10 ºC .The test chemical was prepared into a methanol solution. In 3 ml of DPPH solution, a 40 uL aliquot of the methanol solution was inserted. A UV-visible spectrophotometer was used to take instantaneous absorbance values (Milton Roy, Spectronic 1201). The decline in absorbance at 515 nm was monitored constantly, with data collected at 1 min intervals until the absorbance levelled off (16 min). The absorbance of the DPPH radical (control) and the reference chemical ascorbic acid was also measured. Totally the tests were reiterated three times and the results were averaged. The DPPH radical's percentage inhibition (PI) was approximated using the formula:

PI = [{(AC- AT)/ AC} x 100] (1)

Where AC = Absorbance of the control at t = 0 min and AT = absorbance of the sample + DPPH at t = 16 min.

Graphic plots of the dosage response curve were used to estimate the 50% inhibitory concentration (IC₅₀), which is the concentration needed to inhibit DPPH radical by 50%.[29][30][31][32]

Preparations of ligand and lanthanide complexes

Synthesis of ligand

N,N'-((ethane-1,2-diylbis(sulfanediyl))bis(2,1-phenylene))bis(2-chloroacetamide) (3)

A solution of bis(amine) 1 (2.63 g, 10 mmol ) in DMF (20 ml) was added chloroacetyl chloride (2) (2.24 g, 20 mmol). The reaction mixture was stirred at 100^oC for 2h, then left was cooled to room temperature and crushed ice was added.[33] The solid obtained was collected by filtration, dried and crystallized from DMF/ethanol as colorless crystals to give 3, (65%); mp. 162–164°C. IR (KBr): n 3433 (NH), 1682 (C=O) cm^–1. ¹H NMR (CDCl₃): d 2.87 (s, 4H, 2CH₂S), 4.22 (s, 4H, 2CH₂Cl), 7.09 (t, 2H, J = 7.5 Hz, ArH`s), 7.36-7.48 (m, 4H, ArH), 8.41 (d, 4H, J = 8.4 Hz, ArH`s), 9.62 (s, 2 H, NH) ppm. Anal. Calcd for C₁₈H₁₈Cl₂N₂O₂S₂(429.37): C, 50.35; H, 4.23; N, 6.52%. Found: C, 50.40; H, 4.20; N, 6.71%.

N,N'-((ethane-1,2-diylbis(sulfanediyl))bis(2,1-phenylene))bis(2-morpholinoacetamide) (5)

A mixture of each of bis(2-chloroacetamide) 3 (4.3 g, 10 mmol), morpholine (4) (1.74 g, 20 mmol) in acetone (50 ml) was heated under reflux for 2h, The solvent was then removed in vacuo.[33] Crushed ice was added to the reaction mixture and the solid obtained was collected by filtration and crystallized from dioxane as colorless crystals to give 5 as in scheme 1, (73%); mp. 200-202 °C. IR (ν, cm^-1, KBr): 3222 (NH), 1677 (C=O), 1428 (C-N) stretching, 804 (C-N) heterocycle, 1198 (C-O), 759 (C-S) stretching
cm^–1. ¹H NMR (d, ppm, CDCl₃): 2.61 (s, 8H, 4CH₂N), 2.87 (s, 4H, 2CH₂S), 3.17 (s, 4H, COCH₂N), 3.75 (t, J = 4.5 Hz, 8H, 4OCH₂), 7.03 (t, J = 7.2 Hz, 2H, ArH`s), 7.33-7.039 (m, 4H, ArH`s), 8.46 (d, J = 8.1 Hz, 2H, ArH`s), 10.25 (s, 2H, NH) ppm. Anal. Calcd for C₂₆H₃₄N₄O₄S₂(530.70 g/mol): C, 58.79; H, 6.41; N, 10.55; S, 12.06 %. Found: C, 58.67; H, 6.33; N, 10.43; S, 12.01%.

Synthesis of the lanthanide complexes

The complexes of H₂L ligand were made (scheme 2) using the reaction of 1:1 molar mixture of warm DMF solution (60 °C) of the appropriate metal chloride (0.144 g ErCl₃·6H₂O, 0.15g YbCl₃·6H₂O, 0.14 g TaCl_5, 0.38 mmol) and H₂L (0.2g, 0.38 mmol). The resulting mixture was agitated under reflux for 1 hour whereupon the complexes precipitated. They were collected using filtration and purified using diethyl ether washing numerous times.

[Er(H₂L)Cl₂]Cl.4H₂O complex

Yield 80%; mp. 225 °C. IR (ν, cm^-1, KBr): 3244 (NH), 1662 (C=O), 1455 (C-N) stretching, 808 (C-N) heterocycle, 1207 (C-O), 767 (C-S) stretching, 682 (M-S), 467 (M-N) cm^–1. Anal. Calcd: C, 35.58; H, 4.79; N, 6.39; S, 7.30; Er, 19.08 %. Found: C, 35.36; H, 4.61; N, 6.00; S, 7.22; Er, 19.00%.

[Yb(H₂L)(H₂O)₂]Cl₃ complex

Yield 81%; mp. 211 °C. IR (ν, cm^-1, KBr): 3238 (NH), 1666 (C=O), 1429 (C-N) stretching, 803 (C-N) heterocycle, 1198 (C-O), 760 (C-S) stretching, 937 and 864 H₂O stretching, 683 (M-S), 467 (M-N)
cm^–1. Anal. Calcd.: C, 36.86; H, 4.49; N, 6.62; S, 7.56; Yb(III), 20.44%. Found: C, 36.71; H, 4.44; N, 6.47; S, 7.31; Yb(III), 20.11%

[Ta(H₂L)Cl₂]Cl₃.4H₂O complex

Yield 79%; mp. 238 °C. IR (ν, cm^-1, KBr): n 3230 (NH), 1688 (C=O), 1464 (C-N) stretching, 815 (C-N) heterocycle, 1200 (C-O), 762 (C-S) stretching, 612 (M-S), 458 (M-N) cm^–1. ¹H NMR (CDCl₃): d 2.67 (s, 8H, 4CH₂N), 2.89 (s, 4H, 2CH₂S), 3.18(s, 4H, COCH₂N), 3.77 (t, J = 4.5 Hz, 8H, 4OCH₂), 7.04 (t, J = 7.2 Hz, 2H, ArH`s), 7.35-7.04 (m, 4H, ArH`s), 8.52 (d, J = 8.1 Hz, 2H, ArH`s), 10.25 (s, 2H, NH) ppm. Anal. Calcd : C, 32.45; H, 4.37; N, 5.82; S, 6.66; Ta, 18.80%. Found: C, 32.22; H, 4.30; N, 5.55; S, 6.31; Ta, 18.62%

Elemental and molar conductance analyses

The results of the elemental analyses (C, H, N, and S) agreed well with the anticipated chemical makeup of the compounds (Table 1). In addition, elemental studies revealed that the ligand H₂L is coordinated in a 1:1 molar ratio. The Ln complexes' molar conductance measurements in DMSO ranged from 70–130 Ω^-1mol^-1cm². [Er(H₂L)Cl₂]Cl.4H₂O, [Yb(H₂L)(H₂O)₂]Cl₃and [Ta(H₂L)Cl₂]Cl₃.4H₂O complexes have molar conductivity values of 70, 110 and 165 Ω^-1mol^-1cm². The complexes' values revealed that they were ionic, and they were electrolytes of the types 1:1, 1:3, and 1:3 electrolytes, respectively.[34][35]

Mass spectrometry (MS)

Using the MS method, the production of the H₂L and its Ln complexes was confirmed. The mass spectrum of H₂L is exposed in Figure 1a. The molecular ion peak was found at m/z = 532.05 amu, which agree with the molecular weight of H₂L and confirms the production of H₂L (calculated 530.70 g/mol).

Similarly, the mass spectra of [Er(H₂L)Cl₂]Cl.4H₂O, [Yb(H₂L)(H₂O)₂]Cl₃and [Ta(H₂L)Cl₂]Cl₃.4H₂O complexes were exposed in Figure 1. In the mass spectra of complexes, the molecular ion peaks at m/z = 876.31 amu (calculated 876.80 g/mol), 846.39 amu (calculated 846.50 g/mol) and 961.42 amu (calculated 961.40 g/mol) for [Er(H₂L)Cl₂]Cl.4H₂O, [Yb(H₂L)(H₂O)₂]Cl₃and [Ta(H₂L)Cl₂]Cl₃.4H₂O complexes, respectively, gives the evidence for the coordination of Ln ions with the ligand [32].

Infrared spectral study

Infrared spectra of the complexes were obtained to prove their structures. The vibration frequencies of the morpholino acetamide ligand and its Ln complexes, as well as their tentative assignments, are presented in Table 2 of the experimental part.

Comparisons by the vibrational frequencies of the free ligand and its metal complexes supported the designations. the infrared spectra of the complexes have four distinct properties. The first is a shift in the stretching frequencies of the band around 767–760 cm^-1 in the metal complexes because of ν(C-S) compared with free H₂L ligand at 759 cm^-1,Which is reliable with the appearance of new weakly to medium bands in the region of 404–411 cm^-1, which could be attributed to the stretching frequencies of ν(M-S) bands, conﬁrmed that, the chelation to the metal ions is accomplished by thiol-Sulphur atoms.[36]

The second feature, the morpholino acetamide ligand shows strong and broad band in the region of 3222 cm^-1 assigned to νN–H vibration. In the complexes, the stretching frequencies of this band was shifted around 3230- 3244 cm^-1 indicating coordination of N atom of secondary amino group and crystalline or coordinated water molecules related with the complex. The band at 1428 cm^-1 assigned to νC-N in ligand is shifted of the stretching frequencies of the band around 1429-1464 cm^-1 showing the coordination of nitrogen. The presence of a band in the far IR range at 458-467 cm^-1attributed to v(M–N) further supports the relationship with N atom [37][38][39][40].

The third feature, the absorption band due to the carbonyl oxygen of amide was showed at 1677 cm⁻¹ in the ligand. But, In the complexes, this band shifted to frequencies about 11–15 cm⁻¹ indicating an H-bond between the ligand and the carbonyl C=O with the NH proton [12].

While, the four feature, the peak at 804 cm^-1 correspond to condensed C-N heterocycles [12][41] and the strong C-O stretching absorptions was found at 1198 cm⁻¹which belongs to morpholino acetamide ring in ligand.[42][43] But, this band slightly shifted in the complexes, suggesting different surrounded environment after complexation.

¹H NMR

Aside from its purity, ¹H NMR spectral data (ppm) for the free ligand using TMS (0 ppm) and DMSO-d₆ solvent corroborated the ligand structure.

The free ligand spectrum (H₂L) observed a singlet signals at 2.61, 2.87 and 3.17 ppm region that can be attributed to the methyl protons (s, 8H, 4CH₂N ), (s, 4H, 2CH₂S) and (s, 4H, COCH₂N), respectively. These signals were observed at 2.67, 2.89 and 3.18 ppm for Ta(V) complex, respectively. Also, the free ligand spectrum showed different signals at 3.75, 7.03, 7.33-7.039 and 8.46 ppm that can be assigned to (t, J = 4.5 Hz, 8H, 4OCH₂), (t, J = 7.2 Hz, 2H, ArH`s), (m, 4H, ArH`s) and (d, J = 8.1 Hz, 2H, ArH`s) protons, respectively. These bands were observed at 3.77, 7.04, 7.35-7.04 and 8.52 ppm for Ta(V) complex, respectively. The ¹H NMR spectrum shows only one shift for the protons of the NH group from 10.25 ppm (the free ligand) to 10.32 ppm in its mononuclear Ta(V) complex [44] [26]. This change can be explained by the role of the NH proton in hydrogen bond formation as well as N binding to metal ions.

Thermal analysis studies (TG and DTG)

Table 3 shows the outcomes of the thermal investigation of the ligand in addition to its Ln complexes. The elimination of the C₂₆H₃₅N₄O₄S₂molecule at T_max 299 and 386 ºC with a mass loss of 98.90% (calcd. 100%).was compatible with the TG curve of ligand referring to two processes.

The [Er(H₂L)Cl₂]Cl.4H₂O complex thermally stable up to 46 ºC, and the decay originated from 46 to 900 ºC and completed in three phases. The first decay step within the 46 to 140 ºC temperature range with a maximum temperature of 65 ºC relates to the loss of 4H₂O with a weight loss of 7.61% (calcd. 8.21%). The 2^nd and 3^rd decay steps within the 140 to 900 ºC temperature range with a maximum temperature of 336 and 577 ºC correspond to loss of 1½Cl₂and C₂₂H₃₅N₄O_2.5S₂ molecules with a weight loss of 63.08% (calcd. 64.50%). The net weight loss was 80.69% (calcd. 82.71%) leaving ½Er₂O₃contaminated with carbon as final residue.

The thermal decay of the [Yb(H₂L)(H₂O)₂]Cl₃ complex proceeded throughout the temperature range from 87 to 900 ºC with three decay phases. The first began at 87 to 234 ºC temperature range with a maximum temperature of 151 ºC and corresponds to lack of 2H₂O and ½Cl₂ (estimated weight loss 7.96%, calcd. 8.45%). The second and third phases at 234 to 900 ºC temperature range with a maximum temperature 342 and 628 ºC reflected the loss of Cl₂and C₂₅H₃₅N₄O_2.5S₂ molecules (found 66.95%, calcd. 66.86%) and this degradation processes are ended with the formation of the ½Yb₂O₃ contaminated with carbon atom as a final product. The metal content is concordant with the proposed structure.

The thermal decay of the [Ta(H₂L)Cl₂]Cl₃.4H₂O complex proceeded throughout the temperature range from 37 to 900 ºC with four decay phases. The first began at 37 to 148 ºC temperature range with a maximum temperature of 70 ºC corresponds to lack of 4H₂O (estimated weight loss 6.84%, calcd. 7.49%). The last three phases at 148 to 900 ºC temperature range with a maximum temperature of 244, 343 and 621 ºC reflected the loss of 2½Cl₂and C₂₆H₃₅N₄O_1.5S₂ molecules (found: 70.99%, calcd. 69.53%) and the final residue of this degradation processes is the formation of ½Ta₂O₅as a final product. The metal content is concordant with the proposed structure.[45]

XRD study

Powder XRD pattern of morpholinoacetamide ligand (H₂L) and Ta(V) complex were detailed in the 2ϴ range from 0 to 80. Figure 2 shows the XRD pattern of morpholinoacetamide ligand (H₂L) and the Ta(V) complex are exposed in Figure 2. The XRD pattern of the Ta(V) complex revealed good defined crystalline peaks revealing that the complex was crystalline in phase with crisp crystalline XRD patterns that differed significantly from the ligand. Crystallinity appears in the Ta(V) complex due to the metallic compound's inherent crystalline nature. the grain size of the Ta(V) complex was estimated using Scherre's equation. Through determining the full width at half maximum of the XRD peaks and relating the relation dXRD = 0.9λ/β(Cosθ), where ‘λ’ is the wavelength, ‘β’ is the full width at half maximum, and ‘θ’ is the peak angle.

The ligand and complex have the average crystallite size of 3.35 to 96.5 nm and 1 nm to 22.7 nm suggesting that morpholinoacetamide ligand (H₂L) and the Ta(V) complex are nanocrystalline compounds, respectively. According to previous researches, the difference between the two XRD shapes may assigned to coordination moiety. [46][47][48][49]

Structural interpretation

Different approaches were used to characterize the structures of the produced Ln complexes, including elemental studies (C, H, N, M), molar conductivity measurements, FT-IR, UV-Vis spectroscopy, ¹H-NMR, mass spectral, and thermal investigations. As a result, as illustrated in Figure 3, the structure of all complexes may be presented.[35]

Electronic transition spectra of ligand and its complexes

In DMF at room temperature, UV/V absorption spectra of the morpholinoacetamide ligand and its complexes were measured (Table 4). The spectra can be found in the appendices. The organic ligand absorption band displayed two bands at 288 and 365 nm, which were ascribed to π–π* and n→π* transitions of the benzene rings and CH=O group, respectively. These bands are red-shifted in Ln complexes, indicating that the ligand is coordinated to the Ln ions.[12] Because the 4f orbitals in lanthanides are buried deep within the atom, ligand vibrations have less of an impact on the broadening effect. At 537nm, a prominent band of Ligand to Metal Charge Transfer emerges.[50]

DFT calculations

the ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O complex by donning optimized molecular geometry and geometrical parameters, such as bond lengths, bond angles, HOMO energy, and LUMO energy, were calculated using the B3LYP and 6-31G basis set with no symmetry constraints. Gauss view 5.0 version software was used to visualize the optimized molecular structure, HOMO-LUMO, and MEP surface. The absence of the imagined confirms the achievement of a true energy minimum of the molecular structure. Figure 4 appears the optimized molecular geometry of the ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O , per the atomic numbering in the ground state.[51]

Mulliken charge analysis

The Mulliken atomic charge indicates the charge density distribution of the ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O. The distribution of charges in the ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O was used to calculate the polarizability, dipole moment, and chemical reactivity of a molecule. The Mulliken atomic charges were estimated using the B3LYP using the basis set 6-31G, as shown in Figure 5 and Table 5.[51]

Bond lengths and bond angles

The B3LYP/6-31G-calculated geometrical parameters (bond lengths and angles) were matched to the experimental parameters and found to be extremely good replicated. Tables 6 and 7 show the findings of the study.[51] In the morpholinoacetamide ligand, The bond lengths of C(19) - S(8), C(7) - S(9), C(21) – N(29) and C(11) - N(31) were 1.85, 1.85, 1.43 and 1.41 Å, respectively,. . When they were coordinated to the Ta(V) ion, they displayed a little elongation and were found to be 1.91, 1.94, 1.65 and 1.68 Å, respectively. The ligand (H2L) in the Ta(V) complex was coordinated by two nitrogen and two sulphides, with two chloride ions filling the remaining two places. The bond angles in the Ta(V) coordination sphere were examined using the octahedral geometry, as previously indicated. The lowering of the metal chloride angle is responsible for intramolecular hydrogen interactions.[26]

Frontier molecular orbitals (FMO) studies

The FM orbitals are the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of a structure. The charge transfer collaboration also chemical reactivity of a ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O are determined by investigations of frontier molecular orbitals (HOMO and LUMO).

Figure 6 shows the HOMOs with LUMOs computed for ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O applying the B3LYP/6-31G level of theory. Table 8 shows the estimated energies of the frontier molecular orbitals as well as the energy gap of the ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O .

The ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O stability is confirmed by the negative HOMO and LUMO energy values. The HOMO-LUMO energy gap represents the molecule's chemical strength and reactivity. In a ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O with a narrow energy gap, the extent of intramolecular electron transfer from the donor to the acceptor is larger.[51]

Molecular properties

Using Koopman's theorem, the HOMO and LUMO energy values were utilized to calculate molecular properties for example ionization potential (= −E_HOMO), electron affinity (= −E_LUMO), electronegativity (χ), global hardness (η), global softness (S), electrophilicity index (ω), and chemical potential (μ).The greater value of ionization potential also minor value of the electron affinity implies higher stability of the ligand matched to the [Ta(H₂L)Cl₂]Cl₃.4H₂O complex with a minor value of ionization potential and greater value of electron affinity. The above discussed global reactivity descriptors of the molecules have been computed through the B3LYP/6-31G method, which was described in Table 8. The magnitude of global hardness and softness provides the ligand stability. In the same way, the [Ta(H₂L)Cl₂]Cl₃.4H₂O with a negative value of chemical potential, on the other hand, does not decompose into elements.[51]

Molecular electrostatic potential

The molecular electrostatic potential (MEP) surface, which depicts the 3D picture of the charge distribution between the ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O provided information regarding the interactions between them. The MEP surface of the ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O were computed using the B3LYP level of theory with the basis set 6-31G and are shown in Figure 7. Hydrogen bonding interactions, nucleophilic reactions, and electrophilic sites can all be estimated using the MEP.The varied colors on the MEP surface represent different electrostatic potential values.. The red color represents electron-rich regions, the blue color represents electron-poor regions, and the white color represents zero electrostatic potential. Really, it is clear that in the ligand nitrogen atoms exposed as red region reacts with electrophilic sites, hydrogen atoms of a methyl group of the ligand exposed as blue region react with nucleophilic sites.[51]

Electrochemical study

Figure 8 shows PP curves for AlSi corrosion in 1 M HCl solutions in the absence and presence of different amounts of morpholinoacetamide ligand at 298 K. Extrapolation of linear sections of anodic and cathodic curves to the relevant corrosion potential yielded the corrosion current density (Icorr), anodic, and cathodic and Tafel slopes (Ecorr). The equation was used to compute the percentage inhibition efficiency ${\text{I}\text{E}}_{\left(PP\right)}$and the degree of surface covering (θ). Table 9 summarizes the electrochemical characteristics derived from Tafel polarization curves.

The current density was lower in the presence of morpholinoacetamide ligand than in its absence, as shown in Table 1. With higher morpholinoacetamide ligand concentrations, the percent inhibition efficiency rose. Morpholinoacetamide molecules are adsorbed on the metal surface, as evidenced by this. With higher morpholinoacetamide inhibitor concentrations, the inhibition became more significant. By raising the inhibitor concentration, Tafel lines are moved to more negative and positive potentials than the blank curve. In each case, the shift in Ecorr values was less than 85 mV, indicating that morpholinoacetamide ligand is a mixed type inhibitor.[52][53][54]

Figure 9 shows Nyquist plots of AlSi in 1 M HCl solutions in the absence and presence of various amounts of morpholinoacetamide ligand at 298 K. The difference in the Nyquist plots at low and high frequencies was used to obtain the charge transfer resistance (Rct) values.[17] As a result, according to the equation, the inhibition efficiency, ${\text{I}\text{E}}_{\left(\text{E}\text{I}\text{S}\right)}$, and the degree of surface coverage of morpholinoacetamide ligand may be estimated from the charge-transfer resistance. Table 10 shows the computed inhibition efficiency values, ${\text{I}\text{E}}_{\left(\text{E}\text{I}\text{S}\right)}$. The value of Rct grew as the concentration of morpholinoacetamide ligand increased. The creation of an insulating protective coating at the metal/solution contact is responsible for increasing Rct values.

Figure 9b and 9c shows a Bode plot throughout the entire frequency range, demonstrating that the rise in impedance values is dependent on morpholinoacetamide ligand concentrations. When the concentration of morpholinoacetamide ligand reaches 500 ppm, the impendence values approach the maximum, indicating effective inhibition corrosion protection. As the concentration of morpholinoacetamide ligand reaches high levels, the phase angle increases, implying effective inhibition corrosion protection.[55][56][35]

Antioxidant activity

DPPH scavenging activities

Figure 10 shows the plots of DPPH scavenging effect (%) for lanthanide complexes, which are concentration dependent. As shown in Table 11, the values of IC50 of Er(III) and Yb(III) complexes for DPPH scavenging effect are 923.81 and 1086.92 µg/ml, respectively. This order of IC50 is opposite to the abilities of scavenging effects for DPPH scavenging.[57] In antioxidant activity investigation, the role of DPPH radical scavenging reports for antioxidant estimation of the substances under study is regarded a dependable also repeatable method. With the DPPH radical at varied concentrations, the ligand and its complexes were tested pro free radical scavenging properties.

Figure 10 shows the findings of the DPPH radical scavenging activity for the ligand and its complexes based on percent inhibition. A further study of the results reveals that the ligand and its complexes all have good DPPH radical scavenging properties. In general, the metal complexes outperformed the precursor ligand in terms of DPPH radical scavenging. The antioxidant results of the ligand and its complexes can be employed in further research to develop medications for the treatment of pathological diseases appearing from oxidative stress.[34]

Antimicrobial Activity

Figure 11 and Table 12 demonstrate the mean inhibitory activity of the morpholinoacetamide ligand and its complexes against the microorganisms tested. In the development of novel metal-based therapeutic agents., coordination between biologically active ligands and metal ions is critical. The produced ligand and its metal complexes had strong antimicrobial activity against the microorganisms tested, with varying degrees of inhibitory characteristics. All microorganisms were responsive to the ligand N,N'-((ethane-1,2-diylbis(sulfanediyl))bis(2,1-phenylene))bis(2-morpholinoacetamide, Er(III), Yb(III) and Ta(V) complexes with inhibitory zones as show in Table 8. The metal complexes were often more active than the ligand and, in a few cases, had comparable activity to those of the positive control drugs. The Yb(III) complex had inhibitory zones of 12.0-14.0 mm /mg against all the tested microbes with the exception of Aspergillus flavus and Candida albicans. The increased sensitivity of the complexes could be assigned to hyper conjugation of the coordinated aromatic system and increased liposolubility which results in a reduce in the polarity of metal ions and increased delocalization of π-electrons over the complex ring. The latter encouraged metal complex permeation across the lipid layers of the microbial membrane, enhancing antibacterial action. Furthermore, chelation also inhibited a number of cellular enzymes that are required for metabolic processes in bacteria. The Yb(III) complex revealed the best antibacterial activity of all other synthesized compounds and compared helpfully to the activity of ciprofloxacin against some microbes. Figure 12 depicts the biological activity index of these complexes graphically. In the near future, the ligand could be used to develop antimicrobial drugs. [34][25]

Docking

SARS-CoV-2 (6Y84) and E. coli DNA gyrase (5MMN) showed good binding interactions across several attaching mechanisms in molecular docking investigations. To gain a worthier understanding of the interaction of organic ligands and their metal complexes with 6Y84 and 5MMN, molecular docking experiments were carried out to predict the preferred binding sites as well as the molecule's chosen orientation. The minimum energy shape (Figure 10) of Ta(V) complex with reveals that it is well-fitting in order to form hydrogen acceptor bonding with the two proteins. The molecular docked model of the ligand and its metal complexes was shown in Figure 13 and Table 13. They demonstrated electrostatic and partial intercalation between themselves and protein base pairs.[46]Figure 13 shows the 3D structures of SARS-CoV-2 (6Y84) and E. coli DNA gyrase (5MMN) receptors obtained from the Protein Data Bank. The 3D structures of the ligand in addition to its metal complexes were energy lessened plus docked interested in the active binding sites of these receptors. Docking techniques were tested by simulating the PDB crystal structures in silico. The several binding poses that were created were examined and found designate pharmacological targets for therapeutic agents.[12]

Physico-chemical and spectral analyses were used to manufacture and analysis a tetrapodal ligand obtained from N,N'-((ethane-1,2-diylbis(sulfanediyl))bis(2,1-phenylene))bis(2-chloroacetamide) and its new Yb(III), Er(III), and Ta(V) complexes. The ligand was discovered to be tetrapodal, with two nitrogen and two sulphides groups that coordinate to the ligand complexes. In vitro antimicrobial experiments revealed that the tetrapodal ligand, MT, has lower antibacterial activity than mononuclear complexes against the test pathogens. A range of in vitro tests, such as DPPH, were used to assess the ability of test materials to scavenge free radicals.The findings demonstrated that the Er(III) compound has high antioxidant properties. DFT calculations were used to analyse the geometry of the Ta(V) complex. The ligand and its complexes were verified to be inhibitors of 6Y84 and 5MMN by molecular docking experiments.

.

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Table (1)

Analytical and physical data of Schiff base ligand (H₂L) and its metal complexes.

Compound

(Molecular Formula)

Colour

(%yield)

M.p.

(°C)

% Found (Calcd.)

Λ_m

Ω^-1mol^-1cm²

C

H

N

S

M

H₂L

Yellowish white

(73)

201

58.67

(58.79)

6.33

(6.41)

10.43

(10.55)

12.01

(12.06)

----

[Er(H₂L)Cl₂]Cl.4H₂O

Gerry

(80)

225

35.26

(35.58)

4.61

(4.79)

6.00

(6.39)

7.22

(7.30)

19.00

(19.08)

70

[Yb(H₂L)(H₂O)₂]Cl₃

Yellow

(81)

211

36.71

(36.86)

4.44

(4.49)

6.47

(6.62)

7.31

(7.56)

20.11

(20.44)

130

[Ta(H₂L)Cl₂]Cl₃.4H₂O

Buff

(79)

238

32.22

(32.45)

4.30

(4.37)

5.55

(5.82)

6.31

(6.66)

18.62

(18.80)

105

Table (2)

IR spectra of H₂L ligand and its metal complexes.

Assignment	Ѵ(NH) And hydrated H₂O stretching	Ѵ(C=O) stretching	V(C-N) Stretching (Aliphatic)	V(C-N) (Morpholinoacetamide)	V(C-O) (morpholinoacetamide)	V(C-S) stretching	H₂O	Ѵ(M-S)	Ѵ(M-N)
H₂L	3222m	1677 sh	1428 sh	804m	1198 sh	759 sh
[Er(H₂L)Cl₂]Cl.4H₂O	3244s	1662 sh	1455s	808m	1207 sh	767 sh		408	467m
[Yb(H₂L)(H₂O)₂]Cl₃	3238s	1666 sh	1429s	803s	1198 sh	760 sh	937 864	411	467 s
[Ta(H₂L)Cl₂]Cl₃.4H₂O	3230s	1688 sh	1464s	815s	1200 sh	762 sh		404	458 s

sh = sharp, m = medium, br = broad, s = small, w = weak

Table (3)

Thermoanalytical results (TG and DTG) of ligand and lanthanides complexes.

Complex

TG range

(°C)

DTG_max

(°C)

n*

Mass loss Total mass loss

Estim (Calcd) %

Assignment

Residues

H₂L

200-900

299, 386

2

98.90 (100) 98.90 (100)

- loss of C₂₆H₃₅N₄O₄S₂

-----

[Er(H₂L)Cl₂]Cl.4H₂O

46-140

140-900

65

336, 577

1

2

7.61 (8.21)

63.08 (64.50) 80.69 (82.71)

- Loss of 4H₂O.

-Loss of 1½Cl₂and C₂₂H₃₅N₄O_2.5S_2.

½Er₂O₃+4C

[Yb(H₂L)(H₂O)₂]Cl₃

87 -234

234-900

151

342, 628

1

2

7.96 (8.45)

66.95 (66.86) 74.91 (75.31)

-Loss of 2H₂O and ½Cl₂.

-Loss of Cl₂and C₂₅H₃₅N₄O_2.5S₂.

½Yb₂O₃+ C

[Ta(H₂L)Cl₂]Cl₃.4H₂O

37-148

148-900

70

244, 343, 621

1

3

6.84 (7.49)

70.99 (69.53) 77.83 (77.02)

- Loss of 4H₂O.

-Loss of 2½Cl₂and C₂₆H₃₅N₄O_1.5S_2.

½ Ta₂O₅

Table 4

Electronic absorption data of ligand and its lanthanides complexes

compound

λ_max

Band assignment

nm

cm^-1

H₂L

365

288

27397

34722

n→π*

π→π*

[Er(H₂L)Cl₂]Cl.4H₂O

651

537

268

15360

18621

37313

charge-transfer

π→π*

[Yb(H₂L)(H₂O)₂]Cl₃

537

279

18621

35842

charge-transfer

π→π*

[Ta(H₂L)Cl₂]Cl₃.4H₂O

537

286

18621

34965

charge-transfer

π→π*

Table 5

The charge distribution calculated by the Muliken method for ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O complex.

H₂L		[Ta(H₂L)Cl₂]Cl₃.4H₂O
Atom	Mulliken charge	Atom	Mulliken charge
C1	-0.129847	C1	0.128335
C4	-0.127981	C4	0.098444
S7	0.361511	S7	0.106774
S8	0.37303	S8	0.112023
C9	-0.321098	C9	-0.091076
C10	0.023313	C10	0.060457
C11	0.129947	C11	0.198799
C12	0.039951	C12	0.106763
C14	0.093488	C14	0.042838
C15	-0.00311	C15	0.10638
C19	-0.327403	C19	-0.170557
C20	0.027274	C20	0.074887
C21	0.130764	C21	0.244166
C22	0.03463	C22	0.090684
C24	0.063274	C24	0.118843
C25	0.002298	C25	0.0864
N29	-0.267644	N29	-0.141695
N31	-0.243954	N31	-0.087658
C33	0.339291	C33	0.146115
C34	0.435643	C34	0.207456
O35	-0.397384	O35	-0.175003
O36	-0.403766	O36	-0.197035
C37	0.198191	C37	0.134372
C40	0.202891	C40	0.169707
C43	0.145724	C43	0.376512
C44	0.134823	C44	0.165475
C45	0.182302	C45	0.261109
C47	0.306633	C47	0.233545
C51	0.228731	C51	0.218095
C52	0.18346	C52	0.181557
C53	0.162636	C53	0.180376
C55	0.183248	C55	0.16969
N59	-0.458242	N59	-0.031674
N60	-0.392883	N60	-0.020905
O61	-0.46481	O61	-0.140996
O62	-0.444928	O62	-0.194516
		Cl71	-0.172917
		Cl72	-0.150419
		Ta73	0.554649

Table (6)

Selected bond lengths and angles for ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O complex.

bond lengths	H₂L	[Ta(H₂L)Cl₂]Cl₃.4H₂O
C1 – S8	1.91	1.93
C4 – S7	1.91	1.92
S7 – C9	1.85	1.94
S7 – Ta73		2.77
S8- C19	1.85	1.91
S8 - Ta73		3.00
C21 - N29	1.43	1.65
N29 – C34	1.39	1.46
N29 - Ta73		3.28
N31 – C33	1.39	1.46
N31 – C11	1.41	1.68
N31 - Ta73		2.97
Cl71 - Ta73		2.56
Cl72 - Ta73		2.56
bond angles
S (7) – Ta(73) – N(29)		123.142
S (7) – Ta(73) – Cl(71)		125.7499
S (8) – Ta(73) – N(31)		126.9083
S (8) – Ta(73) – Cl(72)		123.7101
N(29) – Ta(73) – Cl(71)		85.5803
N(29) – Ta(73) – Cl(72)		87.789
N(31) – Ta(73) – Cl(71)		86.4494
N(31) – Ta(73) – Cl(72)		85.5338
Cl(72)– Ta(73) – Cl(71)		87.1144

Table 7

Calculated energies of ligand and [Ta(H₂L)Cl₂]Cl₃.4H₂O complex by B3lyP/6.31G(d,p)/lanl2dZ.

Property	H₂L	[Ta(H₂L)Cl₂]Cl₃.4H₂O
sCf energy (a.u.)	-2326.97971951	-1637.91778664
dipole moment (debye)	5.6797	6.6920
Ehomo (eV)	-5.419328	-6.59328
Elumo (eV)	-.908208	-5.493312
ΔE (e.gap)	4.51112	1.099968
electronic chemical potential (μ = Elumo+Ehomo/2)	-3.163768	-6.043296
electronegativity (χ = −μ)	3.163768	6.043296
Chemical hardness (η = Elumo - Ehomo/2)	2.25556	0.549984
electrophilicity index (ω = μ²/2η)	2.21879499	10.0431

Table (8)

Main calculated optical transition with composite ion in terms of molecular orbitals

Compound

Transition

Excitation energy (ev)

λ_maxCalc.

(nm)

λ_maxexp.

(nm)

Oscillating strength

H₂L

HOMO → LUMO

HOMO → LUMO+1

4.31

4.04

287

307

288

365

0.0027

0.0048

[Ta(H₂L)Cl₂]Cl₃.4H₂O

HOMO-4 → LUMO+4

HOMO-5 → LUMO

3.48

2.30

356

538

286

537

0.0149

0.0020

Table (9)

Corrosion parameters obtained from potentiodynamic polarization measurements of AlSi in the absence and presence of different doses of l in 1.0 M HCl.

Inhibitor name	Conc. ppm	−Ecorr mV vsSCE	Icorr (μA cm⁻²)	βa (mV dec⁻¹)	βc (mV dec⁻¹)	CR (mpy)	θ	%
Blank	0	663	14.9	122.8	390.1	17890	--------	--------
H₄L	100	657	3.29	128.6	237.3	3938	0.779	77.90
	200	655	1.33	69.3	177.4	1592	0.9107	91.07
	300	664	1.01	67.1	160.1	1207	0.9322	93.22
	400	677	0.668	75.3	152.7	800	0.9551	95.51
	500	673	0.542	66.60	150.5	649	0.9636	96.36

Table (10)

EIS parameters of AlSi in the absence and presence of different doses of H₄L in 1 M HCl .

Solution	Conc. ppm	R_s (Ω cm²)	R_ct (Ω cm²)	θ	IE_(EIS)%
blank	0	1.67	4.12	-	-
H₄L	100	10.83	9.818	0.5819	58.19
	200	2.72	19.94	0.7941	79.41
	300	3.48	23.03	0.8217	82.17
	400	2.723	32.3	0.8729	87.29
	500	3.181	43.36	0.9053	90.53

Table (11)

Evaluation of antioxidant activity using DPPH scavenging (A) ligand, (b)Er(III), (c) Yb(III) and (d) La(III) complexes.

Sample conc. (µg/ml)	DPPH scavenging %
Sample conc. (µg/ml)	Ligand	Er(III) complex	Yb(III) complex	Ta(V) complex
1280	29.48 ± 1.34	60.96 ± 0.82	54.95 ± 1.29	45.03 ± 0.71
640	21.36 ± 0.62	41.27 ± 0.95	38.54 ± 2.38	31.89 ± 0.65
320	14.93 ± 0.15	28.74 ± 0.38	30.12 ± 1.46	17.28 ± 0.43
160	6.82 ± 0.34	15.28 ± 0.46	22.85 ± 0.63	6.34 ± 0.12
80	3.07 ± 0.11	9.41 ± 0.37	18.29 ± 0.17	1.95 ± 0.19
40	1.25 ± 0.09	4.86 ± 0.28	9.46 ± 0.28	0.38 ± 0.06
20	0.71 ± 0.07	2.39 ± 0.71	3.28 ± 0.06	0.11 ± 0.05
10	0.28 ± 0.23	0.95 ± 0.12	0.97 ± 0.21	0.04 ± 0.03
5	0.13 ± 0.08	0.41 ±0.13	0.23 ± 0.09	0
2.5	0.05 ± 0.02	0.28 ± 0.07	0.09 ± 0.04	0
0	0	0	0	0

Table (12)

Biological activity of morpholinoacetamide ligand (H₂L) and its metal complexes

Inhibition zone diameter (mm/mg sample)						Sample
Fungal species		Bacterial species
Fungal species		G^-		G⁺
*Candida* *albicans*	*Aspergillus* *flavus*	*Pseudomonas aeruginosa*	*Escherichia coli*	*Staphylococcus aureus*	*Bacillus subtilis*
0.0	0.0	0.0	0.0	0.0	0.0	Control: DMSO
--	--	10	6	10	9	Amikacin Antibacterial agent	Standard
9	8	--	--	--	--	ketokonazole Antifungal agent	Standard
0	0	3	2	2	1	H₂L
0	0	9	10	11	10	[Er(H₂L)Cl₂]Cl.4H₂O
0	0	12	12	14	13	[Yb(H₂L)(H₂O)₂]Cl₃
0	0	1	10	10	10	[Ta(H₂L)Cl₂]Cl₃.4H₂O

G: Gram reaction - Solvent: DMSO.

Table 13

Energy values obtained in docking calculations of morpholinoacetamide ligand and its Ln complexes with receptors 5MMN and 6Y84.

COMPOUND	Protien	moiety	Receptor site	Interaction	Distance (A^ο)	E (kcal/mol)
H₂L	5MMN	O 36	NH1 ARG 76	H-acceptor	3.00	-2.4
	5MMN	6-ring	CD PRO 79	pi-H	4.44	-0.8
	6Y84	N 29	SD MET 6	H-donor	3.50	-1.5
		O 22	NH2 ARG 298	H-acceptor	3.37	-1.4
		O 56	N SER 1	H-acceptor	3.04	-6.3
[Er(H₂L)Cl₂]Cl.4H₂O	5MMN	S 8	OD2 ASP 49	H-donor	3.22	-2.8
		S 8	ND2 ASN 46	H-acceptor	3.68	-8.7
		S 8	OD2 ASP 49	ionic	3.22	-3.2
	6Y84	S 8	OD1 ASP 153	H-donor	3.45	-2.8
		S 8	OD2 ASP 153	H-donor	3.05	-1.9
		S12 12	OD2 ASP 153	H-donor	2.84	0.5
		O 21	NH1 ARG 298	H-acceptor	3.10	-1.8
		S 8	OD1 ASP 153	ionic	3.45	-2.1
		S 8	OD2 ASP 153	ionic	3.05	-4.1
		S12 12	OD2 ASP 153	ionic	2.84	-5.7
		ER 69	OD1 ASP 153	ionic	3.04	-4.2
		ER 69	OD2 ASP 153	ionic	1.28	-38.5
[Yb(H₂L)(H₂O)₂]Cl₃	5MMN	O 70	NE2 HIS 83	H-donor	3.00	-8.0
	5MMN	O 54	NH1 ARG 76	H-acceptor	3.14	-0.8
	6Y84	O 70	OD1 ASP 153	H-donor	2.47	-3.2
		O 35	NE ARG 298	H-acceptor	3.16	-2.1
		O 35	NH1 ARG 298	H-acceptor	2.71	-6.1
		O 68	N TYR 154	H-acceptor	2.80	-0.9
[Ta(H₂L)Cl₂]Cl₃.4H₂O	5MMN	CL 70	NH1 ARG 76	H-acceptor	3.10	-9.0
	5MMN	CL 70	NH2 ARG 76	H-acceptor	-6.2	-6.2
	6Y84	CL 70	NZ LYS 102	H-acceptor	3.26	-14.9

Scheme 1 and 2 are available in the Supplementary Files section.

Graphicalabstract.png
Graphical abstractNew stable heterometallic complexes of Ln metal ions (Ln = Ta, Yb, Er) have been synthesized and characterized
scheme1.png
Scheme. 1. Preparation of ligand.
scheme2.png
Scheme. 2. Preparation of Ln complexes.

Synthesis, structural and theoretical studies on new morpholino acetamide ligand and rare earth metal complexes and corrosion Inhibition Effect

Status:

Version 1

Abstract

Figures

Introduction

Experimental

Results And Discussion

Conclusion

References

Tables

Scheme

Supplementary Files

Status:

Version 1