The novel hydrazone ligand 2-hydroxy 4-methoxy benzylidene 2-hydroxy benzhydrazide [HL] was prepared by condensing 2-hydroxy benzhydrazide and 2-hydroxy 4-methoxy benzaldehyde in methanol solvent. The Cu-II complexes [Cu(HL)(NO3)].1/3H2O (1a), [{Cu (HL)}2 (μ-SO4)].12/3H2O(2a), [Cu(HL)(H2O) Cl](3a) were synthesized by refluxing Cu-II salts CuNO3.3H2O CuSO4.5H2O and CuCl2.2H2O with methanol solution of [HL] and characterized by spectral techniques (FT-IR,1H-NMR,13C–NMR,UV-Visible, PXRD study).The complexes are further characterized by thermo gravimetric(TG)analysis, molar conductivity, elemental analysis and magnetic susceptibility measurement study. FT-IR spectra provides valuable information about different coordination sites. UV-Visible spectroscopy reflect LMCT bands from 242718- 261780 cm-1 and d-d bands in the range of 143884-156250 cm-1 in addition to n-π*and π -π*transition in all complexes. Square planar to square pyramidal geometry was proposed for all complexes as illustrated in magnetic, electronic and spectroscopic data. X-ray powder diffraction analysis reveals crystalline nature for all complexes. The experimental results of TGA analysis are in good agreement with spectroscopic data of complexes. A comparison of spectroscopic and physicochemical data are very useful in creating correct assignments and understanding of structure of complex. The ligand act as tribasic tridentate chelating through the phenolate oxygen, azomethine nitrogen and oxygen of enolate donar functionality with copper-II ion. The antibacterial potential of synthesized complex catalysts was evaluated against human pathogenic bacteria such as Bacillus subtilties, Bacillus cereus, Escherichia coli, Pseudomonas velgaris,and Staphylococcus aureus etc. Also, the Cu (II) complexes demonstrate significant antioxidant activity. The catalytic performance in alcohol oxidation using hydrogen peroxide as a green oxidant is also investigated.
Research Article
Novel Cu-II Complexes of 2-Hydroxy 4-Methoxy Benzylidene 2-Hydroxy Benzhydrazide: Synthesis, Spectral Characterization, Thermal, Antimicrobial, Antioxidant and Catalytic activity Study
https://doi.org/10.21203/rs.3.rs-5304396/v1
This work is licensed under a CC BY 4.0 License
You are reading this latest preprint version
Transition metal complexes
catalysis
ligand
UV-Visible spectroscopy
The novel hydrazone Schiff base and their Cu-II complexes were synthesized.
The ligand and metal complexes were confirmed by different spectral techniques.
The thermal study of complexes support proposed structural geometry for synthesized metal chelates.
These complexes shows potential antibacterial and antioxidant activity.
These complexes also shows catalytic activity in alcohol oxidation.
The coordination chemistry of hydrazones is very prominent due to their role as excellent polydentate chelating ligands proficient in forming a coordination complexes with d and f block metals in different oxidation states.[1] Hydrazones and their metal complexes array varies biological activities as antibacterial, antioxidant, anticancer, antiviral, antitumor, antiparasitic and anti-inflammatory reagent.[2–8] When hydrazone metal complex is put in an application on host body, hydrogen bond is come in to existence in between nitrogen of azomethine and microbial cells of microbes affecting expected cellular activities. Further in metal complexes due to emergence of chelate rings, lipophilic character of metal is increased and polarity gets decreased, it breaks permeability barrier of cells influencing their usual cell processes.[9]Metal complexes of hydrazone are accepted for their pharmacological applications. Biological activities of hydrazones and their metal complexes are assessed by many researchers. Some derivatives of hydrazones are influential anticancer and antitumor agents.[10–13 ]
Hydrazones are performing commanding role in analytical applications. They are demonstrated to be impressive anti-corrosion agent due to presence of N-N bonding and immine bond in their structure developing its adsorption capacity. Anticorrosion potential of some hydrazone complexes was communicated by Lagaz,H. and Khamaysa O.M.A.et.al [14–15] They can convey sensor, luminescence, fluorescence applications, supramolecular order, optoelectronic properties [16–20] and also functional in estimation of metal ions by spectrofluorometric and spectrophotometric analysis.[21–22]
In organic chemistry novel methods, catalysts, solvents, oxidants are constantly searched for oxidation of organic molecules.[23] Several homogeneous and heterogeneous methods are reported for catalytic oxidation of alcohols [24] In pharmaceutical industry as well as in preparation of flavors and fragrances oxidation products of alcohol are very efficient[25].Hence to develop new catalytic system that works under mild condition and proceed using green oxidants like H2O2 paying attention of all researchers in chemical sciences because this process is environmental friendly.[26]In several cases solvent free oxidation, microwave assisted oxidation of alcohol give better yield. [27–28] Copper complexes generally catalyze various oxidation reactions.[29] large number of catalysts have been reported but copper containing complexes are very active catalysts [30–31].So we extended our research program focusing concentration on isolation of industrially and medicinally important novel metal complexes for their biological estimation and industrial application.
The present study is designed to study the segregation and inspection of Cu-II complexes of 2-hydroxy 4-methoxy benzylidene 2-hydroxy benzhydrazide. In current work, Antimicrobial and free radical scavenging activity of new synthesized complexes are determined. The Catalytic activity of new complexes is also measured in oxidation of benzyl alcohol at different reaction condition using H2O2 as green oxidant.
Materials and methods
2-hydroxy 4-methoxy benzaldehyde, 2-hydroxy benzhydrazide, Copper nitrate trihydrate, Copper chloride dihydrate, Copper sulphate pentahydrate and benzyl alcohol procured from spectrochem, Mumbai. The solvent methanol, acetonitrile in highly pure form purchased from loba chemicals.1H-NMR and 13C-NMR spectral analysis of ligand was performed in DMSO-d6 solvent on Bruker 400.13MHZ instrument. Chemical shifts are recorded in ppm with tetra methyl silane as internal standard. Bruker (ALPHA) FT-IR spectrophotometer operating within 400–4000 cm− 1 notify IR frequencies. Shimadzu UV -2100 Spectrophotometer record electronic transitions in DMF solvent. LC/MS spectra of ligands and complexes were measured on AB Sciex 3200 Q Trap model in 10% DMSO solution in isopropanol and water. TGA analysis of all complexes were performed with universal TA instrument, USA (SDT Q600). The CHN elemental analysis was performed using vario EL III CHNS elemental analyzer at the SAIF Kochi, India. Metal content in complexes can be determined gravimetrically. PXRD Study is carried out by D-8 Bruker AXS diffractometer using CuKᾳ radiation (λ = 1.54A0). Catalytic activity was measured by treating oxidized product with 2, 4 DNP reagent and taking weight of produced precipitate. Antibacterial activity was determined with the help of agar diffusion method and antioxidant activity was recorded using DPPH scavenging assay. All synthetic work was performed in air free atmosphere.
Synthesis of Ligand
The investigated hydrazone (HL) 2-hydroxy 4-methoxy benzylidene 2-hydroxy benzhydrazide was synthesized using reported procedure. [32] A 1mmol methanol solution of 2-hydroxy 4-methoxy benzaldehyde (0.152 gm) and 2-hydroxy benzhydrazide (0.152 gm) were refluxed for 2 hrs in presence of 2 drops of glacial acetic acid as catalyst at room temperature. White crystals were separated. They were filtered and washed with methanol, recrystallized from DMF and dried in vacuum desiccators over CaCl2.
Yield, 77.19%; Anal.calcd for C15H14N2O4: Calcd. C, 62.93; H, 4.92; N, 9.78.Found C, 62.40; H, 4.45; N, 9.50% ;FTIRcm− 1(KBr pellets):3450 ν(O-H),3198ν(N-H),1629 ν(C = O),1614 ν(C = N),919 ν(N-N);LCMs, Molecular ion peak(M+):m/z,285.1; 1HNMR,(400 MHZ,DMSO-d6 ,δ ppm),11.89(2H,s,-OH),11.53(1H,s,-NH),8.48(1H,s,-CH = N),6.40–7.96 (m, ArH),3.73(3H,s,-OCH3);13C NMR (100 MHZ,DMSO-d6,δ ppm) :55.52(C7),101.82(C2), 106.72(C10), 111.79(C4),116.92(C12),117.77(C6),119.07(C13)128.32(C14),132.36(C5),136.23(C15),150.82(C8),160.23(C1),160.27(C3), 162.66(C11), 165.16(C9),UV-Visible (DMF ,nm): 210,342.
Synthesis of Metal Complex
All metal complexes were prepared according to reported procedure [33]. During formation of each complex 1mmol hot methanol solution of ligand (0.285gm) and 1mmol methanol solution of metal salts [CuSO4.5H2O (0.249 gm), CuCl2.2H2O (0.170 gm), Cu (NO3)2.3H2O (0.241gm)] were refluxed together for 4 hrs forming green colored Cu-II complexes. The solid product obtained was filtered off, washed with methanol and dried in vacuum desiccators over CaCl2. The physical data of ligand and complexes are represented in Table 1.
| Complex | Molecular formula | Molecular weight (gm) | Colour | Yield % | M.P.0c | Elemental analysis C H N M | Molar conductance sm2mol− 1 | |||
|---|---|---|---|---|---|---|---|---|---|---|
| HL | C15H14N2O4 | 286.28 | White | 77.19 | 270 | 62.40(62.93) | 4.45(4.92) | 9.50(9.78) | - | - |
| 1a | C15H14N3O8Cu | 415.28 | Green | 74.25 | ˃300 | 42.60(43.38) | 3.15(3.39) | 9.75(10.11) | 14.95(15.27) | 8.0 |
| 2a | C30H26N4O13Cu2S | 820.69 | Green | 71.70 | ˃300 | 44.05(43.90) | 3.32(3.19) | 6.90(6.83) | 16.05(15.46) | 9.6 |
| 3a | C15H14N2O5CuCl | 401.28 | Green | 75.86 | ˃300 | 44.25(44.89) | 4.25(3.51) | 7.20(6.98) | 16.05(15.81) | 12.5 |
Biological Activities
Antimicrobial Potential
Synthesized complexes were examined for antimicrobial property towards pathogenic microbes like Escherichia coli, Bacillus cerus, Bacillus subtilties, Staphylococcus aureus and Pseudomonas Vulgaris employing agar diffusing method. [34] 7x105cells mL-1 of respective bacterial suspension were spread across the nutrient agar medium. Agar well diffusion method was utilized to deliver the synthesized hydrazone complexes 1a, 2a, and 3a (1 mg mL-1 in DMSO) to the culture plates. Following that, wells of 0.7 cm diameters were formed and loaded with the samples. The increasing concentration (100, 200 and 400 µg/ml) of the sample were used for diffusion. Plates containing samples were kept at 4°C for a few hours in order to allow them to disperse more effectively. Further plats were placed in incubator for 24 hours at 37°C.Anti-microbial activity was determined as zone of inhibition of the drug incorporated in well after 24 hours of incubation.
Antioxidant Activity Study
DPPH radical scavenging potential of synthesized hydrazone complexes was determined utilizing 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals scavenging assay [35]. 1 mL of the relevant samples at varied concentration range (100–500 µg mL-1) were mixed with 2 mL of 1.0 mmol L− 1 DPPH reagent prepared in methanol. Then, reaction mixture kept in dark for the incubation at 37°C for 30 minutes. Further absorbance of the reaction mixtures was recorded at 570 nm by using spectrophotometer (UV-1800, Shimadzu, Japan). The prepared DPPH radical was used having absorbance 0.9–1.1 .The following equation was used to determine the efficiency of the sample to scavenge the DPPH free radical in %:
% RSA = A control - A sample / A control × 100
A control- Absorbance of control; A sample- Absorbance of sample
General Oxidation Procedure
Oxidation reaction was performed in air free atmosphere at 500c. During oxidation 25 ml R.B. Flask was charged with 1mmol of substrate (benzyl alcohol), 10ml CH3CN solvent and 2.5mg catalyst, after adding 1.5 mmol H2O2, reaction mixture was stirred for 4 hours. The oxidized products were treated with 2, 4 DNP reagent to precipitate only benzaldehyde formed. [36] This precipitate was dried at room temperature and weighed. Finally from the weight of precipitate yield was determined.
The novel hydrazone ligand [HL] was synthesized by refluxing equimolar amount of 2-hydroxy 4-methoxy benzaldehyde and salicyl hydrazide in methanol solvent for 2 hours.(Reaction scheme 1)Synthesis of of similar type of hydrazone Schiff bases was also reported by Rahim F.et.al.[32] Three Cu-II complexes of ligand were synthesized by condensing 1mmole metal salt and ligand solution in methanol solvent. Ligand is tribasic, tridentate (i.e.enolate form) coordinate to metal through ONO donor sites. These complexes are green coloured, stable and having high melting point. These are insoluble in solvents like methanol, ethanol, benzene, chloroform etc. but soluble in DMSO and DMF solvent. Complexes shows low values of molar conductance showing non electrolyte nature of these complexes. The geometry at copper center is square planar for complex 1a and square pyramidal for complex 2a and 3a.[37]
FT-IR Spectral Discussion of ligand and complexes
Infrared spectra have emerged as the most useful tool for understanding ligand metal interaction. Mode of bonding was studied by comparing the IR spectra of free ligand with spectra of metal complexes. The coordination sites were designated from frequency shift of different groups in metal complexes with respect to free ligand. Prominent transitions in IR Spectra of ligand and complexes are depicted in Table 2 The free ligand (HL) reflect signal at 3450 cm− 1 for ν (O-H) group. The disappearance of this signal in all complexes indicate coordination of phenolate oxygen atom to metal center. [38],[39] This is further strengthened by the shifting of ν(C-O)phenolic frequency by 4 to13 cm− 1 in complexes from 1298 cm− 1 in ligand. The spectra of ligand revealed IR frequency at 1614 cm− 1due to ν(C = N) vibrations this band is shifted to lower frequency and appeared at 1605, 1607,1603 cm− 1 in complexes 1a-3a respectively signifying donation of lone pair of electrons of azomethine nitrogen to metal center. This is further supported by upward shift of ν (N-N) vibrational frequency from 919 cm− 1 in ligand to 971–980 cm− 1 in complexes. A prominent Peak is observed for HL at 3198 cm− 1 due to ν(N-H) stretching vibrations and at 1629 cm− 1 for ν(C = O) vibrations respectively. The ν(N-H) and ν(C = O) vibrations are not seen in complexes and appearance of the new bands at 1250, 1262, 1233cm− 1 are attributed to the ν(C-O) (enolate) group coordinated to metal after deprotonation i.e. Carbonyl moiety is destroyed during complexation. [40],[41]The presence of bridging sulphato group in dimeric complex 2a is further detected by strong peak at 1145cm− 1for ν(S-O) vibrations. The two bands are seen in nitrato complex 1a at 1298 cm− 1 and 1380 cm− 1confirming the presence of coordinated nitrate group.[42]The complex 1a and 2a exhibits IR frequency band at 3451cm− 1 and 3432 cm− 1due to lattice water molecules while chloro complex 3a shows stretching frequency at 889 cm− 1due to coordinated water molecule.[41]It is further supported by TG analysis. Appearance of medium bands in the region 450–510 cm− 1 and 550–605 cm− 1 attributed to M-N and M-O stretching vibrations respectively.[43] Thus ligand coordinate to metal center using nitrogen of azomethine, phenolate oxygen and enolate oxygen atom respectively.
| Compound | ν (OH) | ν(N-H) | ν (C = N) | ν (C = O)/ν(C-O)enolic | ν(N-N) | ν(H2O) lattice/ coordinated | ν(M-N) | ν(M-O) |
|---|---|---|---|---|---|---|---|---|
| C15H14N2O4 | 3450 | 3198 | 1614 | 1629 | 919 | - | - | - |
| C15H14N3O8Cu | - | - | 1605 | 1250 | 965 | 3451 | 450 | 605 |
| C30H26N4O13Cu2S | - | - | 1607 | 1262 | 970 | 3432 | 475 | 599 |
| C15H14N2O5CuCl | - | - | 1603 | 1233 | 971 | 889 | 474 | 602 |
NMR Spectral Discussion of ligand and complexes
1H and 13C NMR Spectra of Ligand HL are displayed in Fig. 1–2. They are recorded in DMSO solution to ascertain the molecular structure of ligand and complexes.1H NMR spectra of ligand HL displayed characteristic singlet peaks at 11.89 and 11.53 ppm which are attributed to the phenolic –OH and hydrazide group. The azomethine proton reflect singlet at 8.48 ppm and aromatic protons noticed as multiplets in 6.40–7.96 ppm range. The signal for methoxy protons is detected as singlet at 3.73 ppm. [44]The 13C NMR spectra of ligand revealed 165.16 ppm chemical shift for carbonyl carbon (C9). The C11 and C1 carbons of aromatic ring attached to hydroxyl group shows 162.66 ppm and 160.23 ppm chemical shift respectively. The chemical shift of azomethine carbon (C8) are seen at 150.82 ppm.The C3 carbon for C-OCH3 group records 160.27 ppm chemical shift. While remaining carbons C2, C4, C5, C12, C13, C14, C15 displayed chemical shift from 101.82-136.23 ppm in aromatic region. The methoxy carbon (C7) reflect chemical shift at 55.52 ppm. [45–46].1H and 13C NMR spectra of complexes were not recorded due to paramagnetic nature of copper complexes.[47],[41]
Mass Spectral discussion of ligand and complexes
Mass spectra of complexes give an idea about presence of mononuclear/multinuclear complexes. The molecular ion peak observed in mass spectra is equivalent to molecular weight of complexes.[43] The molecular ion peak observed for ligand at 285.1(C15H13N2O4+) exactly match with the value calculated from atomic masses (C,H,N,O).Major fragments of stable species observed for ligand are 165,136,110.9,95.Mass spectrum of nitrato complex 1a gives molecular ion peak at 413.0 m/z and base peak at 94.9 m/z. It also give prominent complex ion peak at 409.1m/z. Other stable fragments observed at 348.0 and 285.2 m/z. The chloro complex 3a give M + 2 peak at 403.0 m/z. The base peak and complex ion peak is observed at 381.9 m/z with 100% intensity. Some stable fragments recorded are 346.2 and 285.2 m/z. etc. While dimeric sulphato complex 2a shows molecular ion peak at 818.0 m/z corresponding to their molecular weights and base peak at 693.2 m/z with 100% intensity. It also give stable peak for complex ion at 789.1m/z, Other stable species observed are 408.9,48.1,285.1m/z etc.
Electronic Spectral Discussion and magnetic susceptibility measurement study
The electronic spectral data and magnetic moment values of metal complexes are summarized in table.3 while electronic spectra of ligand and complexes are shown by Fig. 4 Electronic spectra for ligand (HL) gives intense band at 210 nm due to n-π*transitions of non-bonding electrons of carbonyl and azomethine linkages and π-π*transitions are observed at 342 nm due to resonance in benzene ring.[45]These bands are strong due to intraligand transitions. In metal complexes these bands are displayed at 240–315 nm at new possition.[46–47] In copper hydrazone complexes 1a-3a, in addition to these bands ,LMCT transitions are also seen at 261740–263157 cm− 1.[48]The broad d-d band at 156250 cm− 1,154798 cm− 1 and 143884 cm− 1 for nitrato (1a),sulphato (2a) and chloro(3a) complex assign 2B1g→2A1g, 2Eg\(\:\leftarrow\:\)2B1g, 2B1g→2B2g transition corresponds to square planar and square pyramidal geometry[49],[50] It was further supported by magnetic susceptibility measurement study. Magnetic moments observed for complex 1a and 3a are 1.71 B.M. and 1.74 B.M. give support to suggested square planer and square pyramidal geometry.[51] while magnetic moments reflected by binuclear sulphato complex 2a is 1.51 B.M. indicating some metal-metal interaction.[42]
| Compound | µeffective (B.M.) | Absorption Maxima(cm− 1) | Spectral assignments |
|---|---|---|---|
| C15H14N2O4(HL) | - | 476190 | n-π* |
| 292397 | π-π* | ||
| C15H14N3O8Cu (1a) | 1.71 | 408163 | n-π* |
| 322580 | π-π* | ||
| 263157 | LMCT | ||
| 243902 | LMCT | ||
| 156250 | d-d transition | ||
| C30H26N4O13Cu2S (2a) | 1.51 | 404163 | n-π* |
| 333333 | π -π* | ||
| 261780 | LMCT | ||
| 243902 | LMCT | ||
| 154798 | d-d transition | ||
| C15H14N2O5CuCl(3a) | 1.74 | 416666 | n-π* |
| 317460 | π -π* | ||
| 263157 | LMCT | ||
| 242718 | LMCT | ||
| 143884 | d-d transition |
TG Analysis of copper complexes
Thermal analysis was found to be suitable for the detection of coordinated and lattice water molecules in metal Complexes. It gives information about different fragments of complex and its thermal stability. It also support the geometry structure of proposed metal chelates. Structure of compounds deduced from spectral and analytical data coincides well with results of thermal data.TG analysis is carried out in an atmosphere of N2 from 250c- 8000c temperature [42],[52].In copper complex 1a 1.40% (calcd. 1.44%) weight loss was observed from 250c to1000c suggesting presence of lattice water molecule(1/3H2O)In second stage of decomposition 53.45% (Calcd 52.28%) of organic moiety (C8H11O3) and nitrate ion were loosed rapidly in between 360.140c-428.680c .Thermal degradation of complex continues upto 7000c loosing 12.56% (calcd 12.77%) of complex moiety (C2N2H),leaving 32.60% (calcd 33.59%) of metal oxide contaminated with carbon atoms as residue at 7000c.[42]In copper complex 2a first weight loss of 3.90% ( calculated 3.65%) was observed in between 250c-1100c shows the presence of lattice water molecule.(\(\:1\frac{2}{3}\)H2O) In next stage 57.80% (calcd 57.75%) organic part (C21H17N2O5) and sulphate group of complex get disintegrated in temperature range 354.260c-437.380c.The remaining organic moiety 21.32%(C9H7N2O2) and residue of Cu2O 17.42% were not decomposed upto 8000c suggesting metal ligand bonds are very strong.[42],[53]Presence of lattice water molecules were further supported by results of IR spectra. Complex 3a shows first stage of decomposition with weight loss of 12.15% (calcd 13.20%) from temperature range 214.720c to 295.030c suggesting loss of coordinated water molecule and chloro group. In second stage of decomposition 34.00%(calcd-33.66%) of ligand portion (C7H5NO2) get disintegrated in between 295.03-394.390c and in last stage of decomposition 29.71%(calcd-28.17%) ligand moiety(C8H7N) get disintegrated up to 7800c.Thus 63.71% (calcd 61.83%) ligand part disintegrated giving 22.60% (calcd 23.81%) metal oxide residue in the form of CuO2.[35]TG-DTA curves of copper complexes are depicted in fig-5-7 while thermo gravimetric data is represented in Table 4
| Compound | Temp.range (0c) | % mass loss Exptl. Calcd. | Decomposition assignments | |
|---|---|---|---|---|
| C15H14N3O8Cu (1a)/[Cu (HL) (NO3)] .\(\:\frac{1}{3}\)H2O(1a) | 25–100 | 1.40 | 1.44 | Lattice water molecule.(\(\:\frac{1}{3}\)H2O ) |
| 360–428 | 53.45 | 52.58 | Organic moiety (-C8H11O3)and nitrate ion(-NO3) | |
| 428–700 | 12.56 | 12.77 | Organic moiety (-C2N2H) | |
| At 700 | 32.60 | 33.59 | Metal oxide residue CuO + 5C | |
| C30H26N4O13Cu2S (2a)/[{Cu(HL)}2(μ-SO4)] .1 \(\:\frac{2}{3}\) H2O(2a) | 25–110 | 3.90 | 3.65 | Lattice water molecule.(1\(\:\frac{2}{3}\)H2O ) |
| 354–437 | 57.80 | 57.75 | Organic moiety and sulphate ion. (-C21H17N2O9S) | |
| 437–800 | - | - | Remaining Organic moiety(C9H7N2O2) and Cu2O metal oxide residue is not decomposed up to 8000c | |
| C15H14N2O5CuCl(3a)/[Cu (HL) (Cl )(H2O)] (3a) | 214–295 | 12.15 | 13.20 | Coordinated chloro group and water molecule |
| 295–394 | 34.00 | 33.66 | Organic moiety (-C7H5NO2) | |
| 394–780 | 29.71 | 28.17 | Organic moiety (C8H7N) | |
| At 780 | 22.60 | 23.81 | Metal oxide residue (CuO2) | |
Schematic thermal degradation of complex [Cu (HL) (NO3)].\(\:\frac{1}{3}\)H2O(1a)
Schematic thermal degradation of complex [{Cu (HL)} 2(µ-SO4)] 1.\(\:\frac{2}{3}\)H2O (2a)
Schematic thermal degradation of complex [Cu (HL) (Cl) (H2O)] (3a)
X-Ray powder diffraction study
Crystalline and amorphous nature of ligand (HL) and copper complexes were derived from X-ray powder diffraction study. Hydrazone ligand and copper complexes 1a-3a were examined by using powder XRD technique over 2ө range at a wavelength of 1.54Ao.Crystallite size of the ligand and complexes were calculated from Scherer’s equation using the XRD line broadening method. FWHM of more intense diffraction peaks was used to calculate crystallite size with the help of Scherer’s equation dXRD=0.9 \(\:{\lambda\:}\) /FWHM cosө [54–55] Micrographs of hydrazone ligand and Cu-II complexes shows well defined peaks showing its crystalline nature. Particle size of ligand was found to be 51.25 nm while Cu-II complexes shows 31.33, 28.20 and 35.25 nm size respectively.
Biological Activity
Antimicrobial Potential
To illustrate biomedical potential of produced molecules the antibacterial potency was investigated against human pathogenic microorganisms. Antimicrobial property was determined using the agar well diffusion technique on a nutrition medium in the Petri dish. Measurements were made of the zone of inhibition (mm) for every type of microbe’s species (Table 5 and Fig. 8) While the microbes used in this activity are pathogenic to humans, some are food pathogens (B. cereus and E. coli). The manufactured pharmacological molecules are effective towards all of these microbes, they might be used in product wrapping materials to inhibit pathogenic microorganisms which extend the shelf life of packed goods [56]
Gram-positive bacteria such as Bacillus cereus have higher inhibitory zone than Gram -negative (Pseudomonas vulgaris and Escherichia coli) bacteria because they have outer lipid membrane made of polysaccharides showing more antigenic properties. Ligand shows lower activity than metal complexes suggesting coordination of metal to ligand. [9]The antibacterial potential of synthetic medicines has been linked to a number of factors. Ionization, which forms an ionic link
| Sr. No. | Microorganisms | Zone of inhibition (mm) for synthesized drug molecules (µg/ml) | |||
|---|---|---|---|---|---|
| [Cu (HL) (NO3) ].\(\:\frac{1}{3}\)H2O(1a) | [{Cu(HL) }2(μ-SO4)].1 \(\:\frac{2}{3}\)H2O(2a) | [Cu (HL) (Cl )(H2O)] (3a) | Ligand HL | ||
| 1. | Bacillus subtilties | 16 ± 0.10 | 17 ± 0.51 | 15 ± 0.57 | 12 ± 0.70 |
| 2. | Bacillus cereus | 19 ± 0.9 | 20 ± 12 | 18 ± 0.21 | 14 ± 0.21 |
| 3. | Escherichia coli | 14 ± 0.5 | 15 ± 0.57 | 14 ± 0.7 | 11 ± 0.32 |
| 4. | Pseudomonas velgaris | 15 ± 0.53 | 16 ± 0.9 | 14 ± 0.8 | 10 ± 0.91 |
| 5. | Staphylococcus aureus | 14 ± 0.81 | 15 ± 0.7 | 14 ± 1.1 | 10 ± 0.35 |
with the negative biological membranes, is among the mechanisms evidenced in several investigation. When drug molecules interact with a microbial surface, the cell structure is damaged, allowing intracellular proteins to escape. Further, reactive groups come into contact with trenches in the membrane and cellular components are released externally. [57]Other biological processes used by pharmacological molecules to restrict microbes include endogenous ROS generation and lowered expression of cellular oxidative genes in bacteria, DNA damage, protein degradation, lipid peroxidation, and cellular hydrophilic/hydrophobic diminution also responsible for the inhibition of bacterial growth [58]
Antioxidant Activity
The measurement of free radical scavenging capacity requires the removal of DPPH ions with hydrogen-donating, molecules and the generation of non-radicals DPPH-H in the reaction solution. Colour intensity of the DPPH solution get changed from dark to light in response to the decrease in absorbance of the test sample demonstrated that the compound has antioxidant potential [59]
In this experiment, the potential of synthetic compounds to scavenge radicals was investigated. Ability of test samples to scavenge DPPH radicals enhanced as the concentration of the samples raised. Where at lowest concentration of 100 µg, the DPPH scavenging activity of 1a is (12 ± 2%), 2a (14.66 ± 2.5%) and 3a (10 ± 1%) respectively. Scavenging activity against free radicals increases in direct proportion to concentration in the sample under investigation. At higher concentration of 500 µg, the radical scavenging activity were 1a (86.33 ± 2.51%), for 2a (90.36 ± 4.16%) and for 3a (82 ± 4.5%) percent respectively as illustrated in Fig. 9.
Catalytic Activity
Copper complexes frequently shows catalytic activity in oxidation reaction.[37]Catalytic activity was measured at 500c in MeCN medium using hydrogen peroxide as oxidant. Cu-II compounds (2.5mg) 1a-3a were taken in round bottom flask in presence acetonitrile (10ml) as solvent. Substrate benzyl alcohol 1mmol was added and after addition of hydrogen peroxide 1.5 mmol reaction get started. (Reaction scheme 3) We obtained 90%, 88% and 91% (Table 6, entry1-3) yields for complexes 1a, 2a and 3a.No reaction product was observed for reaction under study in absence of catalyst and oxidant.
From observed results, complex 3a is active catalyst. So different parameters like role of solvent, amount of catalyst and time was checked for complex 3a.Effect of solvent on reaction under study was observed by taking CH3CN, DMF and DMSO solvents and it was found that acetonitrile is better solvent for the reaction. (Table 7, entry 3) It is medium coordinating solvent with low donar number and high dielectric constant. [45]
| Entry | Complex | Substrate | Yield |
|---|---|---|---|
| 1 | 1a | Benzyl alcohol | 90 |
| 2 | 2a | 88 | |
| 3 | 3a | 91 |
Reaction condition: Solvent CH3CN (10ml); Complex (2.5mg); Temperature (500c) ; H2O2 (1.5mmol); Time 4hrs
Activity of catalytic system was examined by taking different amount of catalyst. Complete conversion was observed when 2.5mg of Cu-II complex was used.(Table 7,entry 3) Rate of conversion was increased with increasing amount of catalyst.(Table 7,entry 1–4 ) The reaction under study for 3 mg of catalyst ,less reaction product is observed.(Table 7,entry 4) It means at high concentration over oxidation takes place converting benzaldehyde into benzoic acid and consequently the yield get decreased. We have also observed effect of time on particular oxidation reaction. If time of reaction increased yield of product get increased. We obtained 91% (Table 7, entry 3) yield after four hours. But yield get decreased (Table 7, entry 7) for reaction operated at five hours, suggesting over oxidation of product benzaldehyde. So choosing right amount of catalyst, solvent, time is necessary to achieve high yield in this particular catalytic reaction. Better results are observed when substrate, oxidant and catalyst are used in 1:1.5:2.5 ratio in this particular catalytic system. Oxidation of benzyl alcohol gives excellent yield like other reported catalytic systems. [44]The melting point of product (benzaldehyde 2, 4 DNP hydrazone) obtained by reacting 2,4 DNP reagent with oxidized product benzaldehyde is 2500c.The mechanism of oxidation of benzyl alcohol to benzaldehyde proceeds through formation of peroxo complex with Cu-II hydrazone complex, it is indicated from previous reports and results of catalytic activity study.[33],[37]
| Entry | Catalyst(mg) | Time (hr) | Temperature (0c) | Solvent | Yield% |
|---|---|---|---|---|---|
| 1 | 1 | 4 | 50 | CH3CN | 58 |
| 2 | 2 | 4 | 50 | CH3CN | 79 |
| 3 | 2.5 | 4 | 50 | CH3CN | 91 |
| 4 | 3 | 4 | 50 | CH3CN | 72 |
| 5 | 2 | 1 | 50 | CH3CN | 41 |
| 6 | 2 | 2 | 50 | CH3CN | 55 |
| 7 | 2 | 5 | 50 | CH3CN | 72 |
| 8 | 2 | 3 | 50 | DMF | Trace |
| 9 | 2 | 3 | 50 | DMSO | Trace |
Hydrazone ligand 2-hydroxy 4-methoxy benzylidene 2-hydroxy benzhydrazide and its three Cu-II complexes [Cu (HL) (NO3)].\(\:\frac{1}{3}\)H2O (1a), [{Cu (HL)} 2(µ-SO4)].1\(\:\frac{2}{3}\)H2O (2a), [Cu (HL) (H2O) Cl] (3a) were successfully synthesized. These complexes were characterized by FT-IR, UV-Visible, 1HNMR, 13C NMR, LC-MS, PXRD study and thermal analysis. The antibacterial, antioxidant and catalytic activity of synthesized complexes were reported. The observed results are outlined as below.
1 .Ligand behave as tribasic, tridentate and coordinate to metal through enolate oxygen, azomethine nitrogen and phenolate oxygen.
2 .FT-IR, electronic spectra and magnetic moment data inferred square planar geometry to complex 1a and square pyramidal geometry for complexes 2a and 3a respectively.
3. Crystallite size of complexes (1a-3a) is evaluated from powder X-ray diffraction study.
4. The thermal studies of the reported complexes (1a-3a) show good accord with the proposed structure and geometry obtained from analytical and spectral data.
5. The Complex 1a and 3a are monomeric while complex 2a is dimeric in nature.
6. The antibacterial and antioxidant screening of ligand and its metal complexes shows the good potential activities. These complexes also shows catalytic activity in benzyl alcohol oxidation.
Author Contribution
Sangeeta Korane is lead author contributed for idea, conceptualization, data acquisition and writing the manuscript. Babasaheb Bhosale contributed for final editing of draft, and characterization. Amol Jadhav contribted for analysis, data acquisition.
Acknowledgements
The authors acknowledge the NMR network (Instrumentation center) in Punyashlok Ahilyadevi Holkar Solapur University, Maharashtra, India. I also thanks the Shivaji University, Kolhapur, and Maharashtra, India for giving facility of PXRD spectra.
- Abu-Dief AM, El-khatib RM, El-Sayed SM, lzahrani S, Alkhatib F, Gehad El-Sarrag G, Ismael M (2021) Tailoring, structural elucidation, DFT calculation, DNA interaction and pharmaceutical applications of some aryl hydrazone Mn(II), Cu(II) and Fe(III) complexes. J Mol Struct 1244:131017. https://doi.org/10.1016/j.molstruc.2021.131017
- Santiago PHO, Santiago MB, Martins CHG, Gatto CC (2020) Copper II Zinc II complexes with hydrazine: Synthesis, crystal structure, Hirschfield surface and antibacterial activity. Inorg Chim acta 508:119632
- Taxak B, Devi J, Kumar S, Asija S (2023) Exploring the antimalarial, antioxidant and antimicrobial properties of newly synthesized diorganotin(IV) complexes with ONO-donor hydrazone ligands. Inorg Chem Commun 158:111473
- Fekri R, Salehi M, Asadi A, Kubicki M (2019) Synthesis, characterization, anticancer and antibacterial evaluation of Schiff base ligands derived from hydrazone and their transition metal complexes. Inorg Chim Acta 484:245–254
- Rogolino D, Carcelli M, Bacchi A, Compari C, Contardi L, Fisicaro E, Gatti A, Sechi M, Stevaert A, Naesens L (2015) A versatile salicylhydrazonic ligand and its metal complexes as antiviral agents. J Inorg Biochem 159:9–17
- Li D, Fan M, Wang H, Zhu Y, Yu B, ORCID logoP Z, logo H ORCID, H (2024) Facile synthesis of a hydrazone-based zinc(II) complex for ferroptos is-augmented sonodynamic therapy. Chem Sci 15:10027–10035
- Almendras I, Huentupil Y, Novoa N, Roussel P, Melis DR, Smith GS, Arancibia R (2019) Trinuclear Ni(II), Pd(II) and Cu(II) complexes containing the 2-hydroxy-benzaldehyde-ferrocenyl-sulfonylhydrazone ligand: Synthesis, structural characterization and antiplasmodial evaluation. Inorg Chim Acta 496:119050
- Kendur U, Chimmalagi GH, Patil SM, Gudasi KB, Frampton CS, Mangannavar CV, Muchchandi IS (2018) Mononuclear late first row transition metal complexes of ONO donor hydrazone ligand: Synthesis, characterization, crystallographic insight, in vivo and in vitro anti-inflammatory activity. J Mol Struct 1153:299–310
- Bhaskar RS, Aswar AS (2020) Synthesis, characterization and antimicrobial studies of novel ONO donar hydrazone schiff base complexes with some divalent metal (II) ions. Arab J Chem 13:6559–6567
- Sathyadevi P, Krishnamoorthy P,Jayanthi E,Butorac RR,Cowley AH,Dharmaraj N (2012) Studies on the effect of metal ions of hydrazone complexes on interaction with nucleic acids, bovine serum albumin and antioxidant properties. Inorg Chim Acta 384:83–96
- Mo QY, Deng J, Liu Y, Huang Li GZ, Yu P, Gou Y, Yang F (2018) Mixed-ligand Cu(II) hydrazone complexes designed to enhance anticancer activity. Eur J Med Chem 156:368–380
- Balsa LM, Ferraresi-Curotto V, Lavecchia MJ, Echeverría GA, Piro OE, García-Tojal J, Pis-Diez R, González-Baró (2021) Anticancer activity of a new copper(II) complex with a hydrazone ligand. Structural and spectroscopic characterization, computational simulations and 3D breast cancer cell models. Dalton Trans 50:9812–9826ORCID logo AC, and León ORCID logo IE
- AY B, Sahin O, Demir BS, Saygideger Y, LopezdeLuzuriaga JM, Mahmoudi G, Safin DA (2020) Antitumour effects of novel nickel -hydrazone complexes in lung cancer cells. New J Chem 44:9064–9072
- Lgaz H, Chung I, Albayati MR, Chaouiki A, Salghi R, Mohamed SK (2020) Improved corrosion resistance of mild steel in acidic solution by hydrazone derivatives: An experimental and computational study. Arab J of chemistry13:2934–2954
- Khamaysa OMA, Selatnia I,Lgaz HSA, Lee H,ZeghacheH,Benahmed M, Ali IH,Mosset P (2021) Hydrazone-based green corrosion inhibitors for API grade carbon steel in HCl :insights from electrochemical, XPS and computational studies. Colloids Surf A 626:127047
- Su X, Aprahamian I (2014) Hydrazone-based switches, metallo-assemblies and sensors. Chem Soc Rev 43:1963–1981
- Sarıoğlu AO, Bulut Z, Kahraman DT, Semih Güler S, Güngör O, Karaküçük-İyidoğan A, Oruç-Emre, ,EE (2024) Homoleptic metal complexes derived from hydrazones as ligand; synthesis, cytotoxic activity, photoluminescence properties and ADMET studies. J Mol Struct 1303:137496
- Marchetti F, Pettinari R, Verdicchio F, Tombesi A (2022) Role of hydrazone substituents in determining the nuclearity and antibacterial activity of Zn (II) complexes with pyrazolone-based hydrazones. Dalton Trans 51:14165–14181
- SinghY,Patel RN, Patel SK, Jadeja RN,PatelAK,Patel N, Roy H, Kumar P,Butcher RJ,Jasinski JP, Cortijo M, Herrero S (2021) Non-covalent interactions governing the supramolecular assembly of copper(II) complexes with hydrazone-type ligand: Experimental and quantum chemical study. Polyhedron 200:115142
- Sıdır, I,Sıdır YG,Berber H,Demiray F (2019) Electronic structure and optical properties of Schiff base hydrazone derivatives by solution technique for optoelectronic devices: Synthesis, experiment and quantum chemical investigation. J Mol Struct 1176:31–46
- Ariza, JLG,González MLM and González MTM (1984) N,N′-oxalylbis(salicylaldehyde hydrazone) as an analytical spectrophotometric and fluorimetric reagent. Part I. Study of the metal reactivity and application to the determination of aluminium. Analyst 7
- Singh RB, Jain P, Singh RP (1982) Hydrazones as analytical reagents: a review. Talanta 29:77–84
- Bhattacharjee A, Dey S, Roy P (2019) Synthesis, characterization and catalytic properties of dinuclear complexes of copper(II) and nickel(II): Oxidation of cyclohexane, toluene and cyclopentane. Inorg Chim Acta 490:93–103
- Bruggeman DF, Mathew S, Detz RJ, Reek JNH (2021) Comparison of homogeneous and heterogeneous catalysts in dye-sensitized photo electrochemical cells for alcohol oxidation coupled to dihydrogen formation. Sustainable Energy Fuels 5:5707–5716
- Chandra P, Ghosh T, Choudhary N,Mohammad ASM (2020) Recent advancement in oxidation or acceptorless dehydrogenation of alcohols to valorized products using, manganese based catalysts. Coord Chem Rev 411:213241
- Zhao G, Liang L, Wang ELS, Tong R (2021) Fenton chemistry enables the catalytic oxidative rearrangement of indoles using hydrogen peroxide. Green Chem 23:2300–2307
- Aneggi E, Campagnolo F, Segato J, Zuccaccia D, Baratta W, Llorca J, Trovarelli A (2023) Solvent-free selective oxidation of benzyl alcohol using Ru loaded ceria-zirconia catalysts. Mol Catal 540:113049
- Varma RS, Dahiya R (1997) Microwave-assisted oxidation of alcohols under solvent-free conditions using clayfen. Tetrahedron Lett 38:2043–2044
- Anbarasu G, Malathy M, Rajavel R (2017) Synthesis and catalytic properties of copper (II) Schiff-base complex immobilized silica materials. J Porous Mater 24:1253–1261
- Sutradhar M, Kirillova MV, Guedes da Silva MFC, Liu C, Pombeiro AJL (2013) Tautomeric effect of hydrazone Schiff bases in tetranuclear Cu(II) complexes: magnetism and catalytic activity towards mild hydrocarboxylation of alkanes. Dalton Trans 42:16578–16587
- Kügler M, Scholz J, Kronzc A, Siewert I (2016) Copper complexes as catalyst precursors in the electrochemical hydrogen evolution reaction. Dalton Trans 45:6974–6982
- Rahim F, Ullah H, Taha M, Wadood A, Javed MT, Rehman W, Nawaz M, Ashraf M, Ali M, Sajid M, Ali F, Khan MN, Khan KM (2015) Triazinoindole analogs as potent inhibitors of alpha-glucosidase: synthesis,biological evaluation and molecular docking studies. Bioorg Chem 58:81–87
- Balapoor L, Bikas R, Dargahi M (2020) Catalytic oxidation of benzyl-alcohol with H2O2 in the presence of adioxidomolybdenum (VI) complex. Inorg Chim Acta 510:119734
- Cos P, Vlietinck AJ, Berghe DJ, Maes L (2006) Anti-infective potential of natural products: How to develop a stronger in vitro ‘proof-of-concept’. Ethnopharmacol 106:290–302
- Aware C, Patil R, Gaikwad S, Yadav S, Bapat V, Jadhav J (2017) Evaluation of L-dopa,proximate composition with invitro anti-inflammatory and antioxidant activity of Mucuna macrocarpa beans:A future drug for Parkinson treatment. Asian Pac J Biomed 7:1097–1106
- Campbell NR (1936) The use of 2, 4-dinitrophenylhydrazine as a reagent for carbonyl compounds. Analyst 61:391
- Sutradhar M, Alegria ECBA, Guedes da Silva MFC, Martins LM, Pombeiro AJL (2016) Aroylhydrazone Cu-II Complexes in keto form: Structural characterization and catalytic activity towards cyclohexane oxidation. Molecules 21:425
- Tajudeen SS, Kannappan G (2013) Synthetic, structural and pharmacological studies on some isonicotinohydrazide and benzohydrazide analogues. J Pharm Res 7:534–539
- Sambuddha B, Susmita M, Writachito C, Soma S, Ratan G, Butcher RJ, Alexandra S, MZ, Chitra M (2009) Synthesis, X-ray crystal structure,DNA binding,oxidative cleavage activities and antimicrobial studies of two Cu-II hydrazone complexes. Polyhedron 28:2785–2793
- Aswar AS, Bhaskar RS,Salunkhe N, Yaul AR (2015) Bivalent transition metal complexes of ONO donarhydraone ligand:Synthesis, structural characterization and antimicrobial activity. Spectrochim Acta Part A 151:621–627
- Dongare G, Aswar A (2021) Synthesis, spectral characterization, thermos-kinetic and biological studies of some complexes derived from tridentate hydrazine Schiff base. J Saudi Chem Soc 25:101325
- Seleem SH, El-Inamy GA, Hanafy Fatin I (2011) Ligational behavior of a phenolic Quinolyl hydraone towards copper -II ions. Chem Cent J 5:2
- Alghamdi IA, Abdelbaset M, Mannoubi IEI (2019) Mixed ligand complexes of copper-II and cobalt-II with hydrazones derivatives and ortho-vanillin: Synthesis characterization and antimicrobial activity. Orient J Chem 35 (6)
- Kargar H, Mehrjardi MF, Ardakani RB, Munawar KS, ,Ashfaq M, Tahi NM (2021) )selective oxidation of benzyl alcohols to benzaldehyde catalyzed by dioxomolybdenum Schiff base complex:synthesis,spectral characterization, crystal structure, theoretical and computational studies. Transition Met Chem 46:1–19
- Pourlimardan O, Chamayou AC, Janiak C, Hosseini-Monfared H (2007) Hydrazone Schiff base manganese -II complexes: Syntheses crystal structure and catalytic reactivity. Inorg Chim Acta 360:1599–1608
- Arumugam V, Kaminsky W, Bhuvanesh NSP,Nallasamy D (2015) Palladium II complexes containing ONO tridentate hydrazone for Suzuki-Miyaura coupling of aryl chlorides in aqueous-organic media. RSC Adv 5:59428
- Senqul EE, Goktark T, Topkaya CG,Gap R (2020) Synthesis,characterization and DNA interaction of Cu-II complexes with hydrazone schiff base ligands bearing alkyl quaternary ammonium salts. J chil chem 65:4754–4758
- a)Patel AK, Jadeja RN, Patel N, Patel RN, Butcher RJ, Kumar S, Kumar G (2022) Copper (II) hydrazone complexes derived from(Z)-N’-{(2-hydroxynapthalen-1-yl}methylene)acetohydrazide:Synthesis,spectralcharacterization,electrochemical behavior, density functional study,in vitro catalytic activity and molecular docking. Results in chemistry 4:100244 b) Alias K,Kassum H,Shakir C (2014) Synthesis, physical characterization and biological evaluation of schiff base M (II) complexes. Journal of association of arab universities for basic and applied sciences 15:28–34
- Yallur BC, Krishna PM,Challa M (2021) Bivalent Ni-II,Co-II,Cu-II Complexes of [(E)-[(2-methyl-1,3-thiazol-5,yl)methylidene]amino]thiourea:Synthesis,spectral characterization, DNA and in-vitro antibacterial studies. Heliyon 7:1–12
- Khor ZC, Low ML,Ling I (2020) Schiff Base and their Cu-II Complexes derived from cinnamaldehyde and different hydrazides synthesis and antibacterial properties. J transition metal complexes 3:1–9
- Kolate SS, Waghuide GP,Patil CJ (2020) Cu-II Complexes as an NNO functionalized hydrazone ligand: Synthesis, characterization and biological studies. Rasayan J Chem 13:1008–1013
- Aly SA, Fathalla SK (2020) Preparation, characterization of some transition metal complexes of hydrazone derivatives and their antibacterial and antioxidant activities. Arab J Chem 13:3735–3750
- a) Alzharani AA Three Cu-II hydrazine complexes:synthesis,physicochemical characteristics, stability,thermal analysis and investigation of metal and iodine absorption. Journal of Umm-Al-Quara University for applied sciences 9:455–470 b), Kavitha, N,Anantha PV (2023) (2017) Synthesis, characterization and thermogravimetric analysis of Co(II), Ni(II), Cu(II) and Zn(II) complexes supported by ONNO tetradentate Schiff base ligand derived from hydrazino benzoxazine. Journal of Saudi chemical society 21: 5457–5466
- Dongare G, Aswar A (2023) Synthesis of new heterocyclic N’-(2-hydroxy – 3-methoxybenzylidene)-4-oxopiperidine-1-carbohydrazide and its mononuclear metal II complexes: spectroscopic characterization,fluorescence,DFT,thermos-kinetic and antimicrobial studies. J Mol Struct 1281:135107
- Kumar N, Asija S, Deswal Y, Saroya S,Kumar A (2022) Development of new trientate ligands bearing hydrazone motif and their diorganotin (IV) complexes:synthesis, spectral, antimicrobial and molecular docking studies. Res Chem Intermed 48:5133–5154
- Sathiyanarayanan G, Gandhimathi R, Sabarathnam B, Seghal KG, Selvin J (2014) optimization and production of pyrrolidone antimicrobial agent from marine sponge-associated Streptomyces sp.MAPS15.Bioprocess. Biosyst Eng 37:561–573
- Agarwal H, Menton S, Kumar V (2020) Functionalization of Zinc oxide nanoparticles using Mucuna pruriens and its antibacterial activity. Surf Interfaces 19:100521
- Rajeshkumar S (2016) Synthesis of silver nanoparticles using fresh bark of pongamia pinnata and characterization of its antibactrrial activity against gram positive and gram negative pathogens. ResourTechnol 2:30–35
- Koksal E, Bursal E, Dikici E, Tozoglu F, Gulcin IJ (2011) Antioxidant activity of Melissa officainalis leaves. J Med Plants Res 5:217–222
Schemes 1-3 are available in the Supplementary Files section.
No competing interests reported.
- suplimentryfile.docx
- Graphicalabstract.png
Graphical abstract
- scheme1.png
Reaction Scheme 1 Synthesis of hydrazone ligand (HL)
- scheme2.png
Reaction scheme 2 Synthesis of Copper complexes
- scheme3.png
Reaction scheme 3Oxidation of benzyl alcohol to benzaldehyde in presence of Cu-II complexes.
