Organic Schiff Base Research Articles

Substituent effect on the chemical and biological properties of diisatin dihydrazone Schiff bases: DFT and docking studies

According to the considered role of lipophilicity-hydrophobicity on organic Schiff base hydrazones, different substituents of phenyl, ethyl, and methyl groups were inserted in the synthetic strategy of diisatin dihydrazones (L1–4). The biochemical enhancement was evaluated depending on their inhibitive potential of the growth power of three human tumor cells, fungi, and bacteria. The biochemical assays assigned the effected role of different substituents of phenyl, ethyl, and methyl groups on the effectiveness of their diisatin dihydrazone reagents. The interacting modes with calf thymus DNA (i.e. Ct-DNA) were studied via viscometric and spectrophotometric titration.The organo-reagent L1 with the oxalic derivative assigned a performed inhibitive action for the examined microbes and the human tumor cell lines growing up over the terephthalic (L4) > malonic (L2) > succinic (L3) ones. From Kb = binding constant, and ∆Gb≠ = Gibb’s free energy values, the binding of interaction within Ct-DNA was evaluated for all compounds (L1–4), in which L1, L3, and L4 assigned the highest reactivity referring to the covalent/non-covalent modes of interaction, as given for (L1–4), 14.32, 13.28, 10.87, and 12.41 × 107 mol−1 dm3, and −45.17, −43.24, −43.75, and −44.05 kJ mol−1, respectively. DFT and docking studies were achieved to support the current work.

SYNTHESIS, CHARACTERIZATION, AND ANTIBACTERIAL EVALUATION OF DIVALENT METAL COMPLEXES WITH SCHIFF BASES DERIVED FROM 4- ANISALDEHYDE AND ARGININE

In the present study, a new Schiff base, 5-Guanidino-2-[(4-methoxy-benzylidene)-amino]-pentanoic acid, and its metal (II) complexes were synthesized. Structural characterization was done using FTIR, UV-visible spectral analysis, molar conductance, and melting/decomposition temperature determination. Spectral studies revealed the ligand to be bidentate, coordinating with the metal through the carboxylic oxygen and azomethine nitrogen. The antibacterial activity (in vitro) against Escherichia coli and Staphylococcus aureus strains was studied using the agar well diffusion method. The results indicated that the free ligand exhibited no biological activity, whereas the cadmium complex (C28H38CdN8O6) proved to be the best antibacterial agent (up to 27 mm diameter inhibition zone against E. coli), followed by the Mn (II) complex and the Ni (III) complex having the least activity against both Escherichia coli and Staphylococcus aureus. This means that metal chelation significantly affected the anti-bacterial behavior of the organic Schiff base. This study contributes to the growing body of knowledge in the field of bioinorganic chemistry and may have potential implications for pharmaceutical and biomedical applications.

Efficient Photocatalytic System based on Schiff‐Base Type Hybrid Polymers for Energy Conversion and Water Treatment

AbstractIn this contribution, a new Schiff‐base hybrid cross‐linked polymer (TFPT‐SHCP) derived from triazine derivatives and silsesquioxanes was developed, and its photocatalytic performance was systematically investigated. Compared with traditional organic Schiff base catalysts, in TFPT‐SHCP, organic inorganic hybrid silsesquioxanes monomers at the molecular level can serve as a sturdy host backbone, bringing structural ultrastability to the final material. And their excellent strength and durability make them have good application prospects in water treatment. Furthermore, the introduction of triazine derivatives with excellent photoelectric performance and the construction of −C=N‐ result in excellent photocatalytic performance of TFPT‐SHCP. The as‐prepared TFPT‐SHCP exhibits excellent degradation capacity of various organic pollutants under visible light catalysis, with degradation rate constants for Congo Red (CR), rhodamine B (RB) and tetracycline hydrochloride (TH) reaching 0.302 min−1, 0.121 min−1, 0.161 min−1, respectively. Under simulated outdoor conditions, dye solutions with concentrations up to 500 ppm can be degraded to complete decolorization within 5 weeks. This work demonstrates the enormous potential of POSS‐based Schiff base materials as a platform for visible light catalysts, paving the way for the pre design and functionalization of related materials in the future.

Tailored Schiff-Base nanocomposite: Unveiling its synergistic potential for colorimetric sensing, heavy metal ion removal, and antibacterial efficacy

The removal of hazardous chemicals and species from water, soil, and air is a key problem in environmental remediation, and various materials have been investigated in this area. The quest for the best material for an environmental application is still unending. Metal oxide-based Schiff-Base nanocomposites, an alternative to conventional materials that combine the advantages of metal oxide and nanoparticles, may open new possibilities for overcoming this challenge. Because of their extraordinarily high surface-to-volume ratio, these materials are ideal for environmental remediation. Organic Schiff base (SB) and its SB-NC nanocomposite were synthesized and characterized using FTIR spectroscopy, XRD, SEM, and TGA/DTA. FT-IR spectra and XRD patterns confirmed the synthesis of Schiff-Base (SB) and its nanocomposite (SB-NC). TGA/DTA indicated the loss of weight % because of solvent evaporation and SB-NC breakdown. The as-prepared Schiff-Base nanocomposite was used for colorimetric sensing of metal ions in an aqueous solution. Among various metal ions, Cr(VI) and Cd(II) showed a positive colour response. Furthermore, to check the versatility of the prepared compound, adsorptive capacity was examined for the same metal ions Cr(VI) and Cd(II). The nanocomposite’s adsorptive efficacy was further evaluated by several critical factors (for example, solution pH, contact time, initial concentration, and adsorbent/adsorbate dose). The antibacterial activities of SB and SB-NC were studied towards Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria, and the results show that synergistic effects have significantly increased the antibacterial activities of the SB-NC.

Synthesis and characterization of copper(II) norcraugsodine complexes: Their in vitro binding studies with therapeutic targets (ct-DNA/tRNA/BSA), cleavage, and cytotoxicity profile

Amaryllidaceae alkaloid are well known for their myriad pharmacological properties such as Alzheimer's dementia, antimicrobial, and antitumor. The therapeutic potency of this bio-pharmacophore was attributed to the presence of its versatile ring structure and carbon skeleton of alkaloid group. Herein, we have reported the synthesis of Cu(II) norcraugsodine Schiff base complexes 1 and 2 and their characterization by analytical, and spectroscopic methods. The comprehensive biological evaluation was done by carrying out interaction studies with therapeutic intracellular targets, ct-DNA, tRNA and BSA protein using complementary biophysical techniques. The corroborative results of binding experiments revealed that both complexes exhibit high propensity against ct-DNA (4.98 × 104 M−1 and 6.19 × 104 M−1) as compared to tRNA (2.00 × 104 M−1 and 3.21 × 104 M−1), attenuating the effect of ligand scaffold on therapeutic potency of drug candidates, and the order of binding was found to be 2 > 1 > SBL. To gain mechanistic insight of inhibition, DNA cleaving ability of complexes was evaluated by gel electrophoretic assay, the complexes were treated in presence of various activator and scavengers. The cleavage was found to be concentration-dependent exhibiting inhibition in presence of pre‑hydroxyl radical scavenger (EtOH), implicating that the cleavage was mediated by discernible hydrolytic pathway. The complexes and the ligand SBL were evaluated for the cytotoxicity response against four resistant cancer cell lines, both the complexes showed much enhanced potency as compared to ligand SBL against most of the cell lines, while complex 2 was more active than 1 towards resistant breast cancer cell line MDA-MB-231. All these studies reconfirmed that on complexation with copper, the therapeutic potency was enhanced multifold as compared to free organic Schiff base.

Structural, electronic and optical properties of synthesized schiff base compound-validation with a computational method

Organic molecules have a profound impact on present-day technologies due to their structure, molecular interactions, ease of modification, and synthesis. The motivation of the present study is to synthesize a dielectric material at room temperature to accurately determine the optical properties the refractive index and dielectric constant and validate it using a computational method. Organic Schiff base compounds are synthesized in equimolar ratios with the host molecule Biphenyl-4-carboxaldehyde and guest molecules a family of distinct anilines using ultrasonication method. The advantages of this method over other conventional methods are a shorter reaction time, lower operating temperature, and easy work up with fewer amounts of solvents. Molecular aspects of synthesized Schiff bases were established by spectroscopic techniques i.e., IR, proton NMR and powdered x-ray diffraction methods showed that these results are consistent with the expected structure. Optical properties the refractive index and dielectric constant were recorded with a spectroscopic ellipsometer. Studies of computational methods provided optimized molecular structures with minimum energy with wavenumbers in agreement with recorded spectra. Quantum mechanical descriptors provide information on electronic and optical properties and help to visualize the corresponding changes in electron density using the Gaussian 16 package. The results of spectroscopic studies are in agreement with computed studies indicating that synthesized Schiff bases are active dielectric materials with major role of nitro compounds best suitable for optical and electronic properties with increased dielectric constant, refractive index and reduced energy.

Comments on “Growth dynamics and molecular structural analysis of dimethylketo thiosemicarbazone single crystals for frequency conversion applications–Optical and thermal characterization”

The authors of the title paper (J Mol Struc1239 (2021) 130463) report to have synthesized for the first time dimethylketo thiosemicarbazone (DMKT) and determined its single crystal structure. In contrast to this claim, the so-called DMKT is not a new organic Schiff base, but in fact, the commercially available acetone thiosemicarbazone, whose single crystal structure reported in 1974, is archived in the Cambridge Structural Database (CSD). In this letter to the Editor, we highlight the importance of compound nomenclature as well as deposition of single crystal structure data in the CSD by taking DMKT as an example.

Slow magnetic relaxation of a {MnIIINaI}n zig-zag chain based single ion magnet

The synthesis using organic Schiff base ligands H2valen, and organic sulfonate ligands Na(4-HBS) in conjunction with Mn(Ac)3⋅2H2O, produces a one-dimensional coordination polymer with the formula {[Mn(valen)Na(4-HBS)2]⋅2CH3OH}n(1) [H2valen=6,6′-((1E,1′E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))bis(2-methoxyphenol); Na(4-HBS)= Sodium 4-hydroxybenzenesulfonate]. Single crystal X-ray diffraction analysis reveals that complex 1 consist of neutral chains with one [Mn(valen)Na]2+ and two 4-HBS−moieties, in which the Mn(III) adopts an elongated octahedral geometry and Na(I) adopts a distorted pentagonal pyramid geometry, respectively. Magnetic investigations indicate the important magnetic anisotropy in the six-coordinated Mn(III) with the zero-field splitting parameter D = -3.2 cm−1. AC measurements suggest that complex 1 displays characteristics of slow magnetic relaxation under a 2000 Oe DC field, indicative of single ion magnet (SIM) behaviour. The effective energy barriers and the pre-exponential factor for complex 1 are determined to be 10.5 cm−1, and 1.36 × 10−7 s, respectively. This research reports not only a rare Mn(III) SIM molecular complex but also provide a potential approach to construct SIM chains.

Study of the reaction mechanism in hydrogen production using metal-free Schiff base as a catalyst

Understanding the hydrogen evolution reaction and its mechanism is crucial for numerous practical applications in the realm of green energy. The development and discovery of new technologies or alternatives hold great significance in generating hydrogen at a low cost. In this study, we propose a novel catalyst, N, N'-bis(2-hydroxy-1-naphthaldehyde)-o-phenylenediamine ([naph]2-o-ph), which is a Schiff base, for hydrogen production. The novelty lies in utilizing the organic Schiff base system and the proposed mechanism for hydrogen evolution, involving protonation and electron exchange on the Schiff base. Both experimental and theoretical results highlight the high capability of the Schiff base in generating hydrogen, providing valuable insights for potential applications in water electrolysis.

Pendant Modification of Poly(methyl methacrylate) to Enhance Its Stability against Photoirradiation.

Photostabilization of functional polymeric materials is important for protection against aging and ultraviolet (UV) irradiation. There is, therefore, the impetus to modify polymers to increase their resistance to photodegradation and photooxidation on extended exposure to UV light in harsh conditions. Various polymeric additives have been designed and synthesized in recent years, and their potential as photostabilizers has been explored. Reported here is the effect of pendant functionalization of poly(methyl methacrylate) (PMMA) through organometallic moiety incorporation into the polymer's backbone. The reaction of PMMA with ethylenediamine leads to the formation of an amino residue that can react with salicylaldehyde to produce the corresponding Schiff base. Adding metal chlorides (zinc, copper, nickel, and cobalt) led to the formation of organometallic residues on the polymeric chains. Thin films of modified and unmodified PMMA were produced and irradiated with UV light to determine the effect of pendant modification on photostability. The photostabilization of PMMA was assessed using a range of methods, including infrared spectroscopy, weight loss, decomposition rate constant, and surface morphology. The modified PMMA incorporating organic Schiff base metal complexes showed less photodecomposition than the unmodified polymer or one containing the Schiff base only. Thus, the metals significantly reduced the photodegradation of polymeric materials. The polymer containing the Schiff base-cobalt unit showed the least damage in the PMMA surface due to photoirradiation, followed by those containing nickel, zinc, and copper, in that order.

Synthesis, characterizations of new Schiff base heterocyclic derivatives and their optoelectronic, computational studies with level II & III features of LFPs

Organic Schiff base compounds with luminous characteristics are receiving attention and increasing demand for the imaging of latent fingerprints (LFPs) at crime scenes. Sb1 and Sb2 novel Schiff base heterocyclic compounds were synthesized and confirmed by using analytical and spectroscopic methods. The existence of both donating and accepting groups influenced the appearance of absorption bands at longer wavelength and was recorded using UV-absorption and emission spectrum in solvent media. Compounds Sb1 and Sb2 emit at 576 nm and 646 nm in bathochromic shift respectively. The electrochemical properties were investigated using cyclic voltammetry. Quantum chemical parameters with vibrational frequency have been estimated in density functional theory (DFT), using TD-DFT/CAM (B3LYP) approach employing 6–311++ G (d, p) basis set in the ground state. Theoretical vibrational frequency values were specifically agreed to obtained experimental values. Furthermore, FMOs, MEPs, RDG analyses and Mulliken atomic charges have been calculated. In addition, LFPs images were developed by powder dusting approach on specified materials using synthetic compounds and visualized under Visible and UV light. The level II and III properties of LFPs on the substrate were observed under light-medium with no background interference, therefore these compounds are potential materials for electroluminescent, OLEDs and forensic science applications.

Growth dynamics and molecular structural analysis of Dimethylketo thiosemicarbazone single crystals for frequency conversion applications - Optical and thermal characterization

New organic Schiff base of Dimethylketo thiosemicarbazone (DMKT) was synthesized by condensation process and grown by solvent slow evaporation method in methanol solution. The grown crystal was subjected to a single crystal and powder X-ray diffraction study and to identify that the material crystallized into a triclinic crystal system with a P-1 noncentrosymmetric space group. The X-Ray data reveals that the crystalline network cohesion of this compound. The FT-IR and FT Raman spectral analysis show the vibration behavior of chemical bonds in the grown material. Its optical behavior was examined by UV–VIS spectrum and the DMKT crystal was found to have transparency in the region between 350 nm and 1100 nm. The luminescent emission of the grown material was identified from the fluorescence spectrum. Improvement in the second harmonic generation efficiency of the grown material was studied by the Kurtz and Perry powder method and it shows 26.7 mV of green light emission. The thermal stability and melting point of DMKT were confirmed by various thermal analyses.

Ultrasound-Assisted Synthesis and Crystal Structure of Novel 2D Cd (II) Metal–Organic Coordination Polymer with Nitrite End Stop Ligand as a Precursor for Preparation of CdO Nanoparticles

In the present research, a sonochemical approach was applied to prepare new cadmium(II) coordination 2D polymer, [Cd(L)(NO2)2]n (L = 1,2-bis(1-(pyridin-3-yl)ethylidene)hydrazine) and structurally characterized with various spectroscopic techniques including XRD, elemental analysis, SEM, and IR spectroscopy. The coordination number of cadmium (II) ions is seven (CdN2O5) by two nitrogen atoms from two organic Schiff base ligand and five oxygen of nitrite anions. The 2D sheet structures ended by nitrite anions and the nitrite anion displayed the end-stop role. The comprehensive system showed a three-dimensional structure with several weak interactions. The high-intensity ultrasound is regarded as an easy, environmentally-friendly, and flexible synthetic instrument for the compounds of coordination. CdO NPs was obtained by thermolysing 1 at 180 °C with oleic acid (as a surfactant). Further, the size and morphology of the produced CdO nanoparticles were investigated through SEM.

Synthesis and characterization of novel Hg(II) complexes with new Schiff bases

The research included the use of new Schiff's bases to prepare novel mercury (II) complexes as follows:Schiff's bases ligands prepared using aromatic aldehydes and various aromatic primary amines [S1-S6]. Six mercury complexes [H1-H6] were prepared by the interaction of mild moles of organic Schiff's bases with 1 mol of mercury salt (CH3COO)2Hg. The Schiff's bases prepared spectroscopes were diagnosed by the UV–visible spectrum, the infrared spectrum (FT-IR), and the nuclear magnetic resonance spectrum (1H NMR). The reaction mechanism was proposed in light of these results, as it confirmed the validity of the proposed chemical compositions. Metallic complexes prepared spectrally were diagnosed by the UV–visible spectrum, the infrared spectrum and the mass spectrum (Lc-Mass), and analysis of the elements C.H.N.S. The mechanism of interaction was suggested in light of these results, as it confirmed the validity of the proposed chemical compositions, magnetic and electrical conductivity sensitivity of all the prepared complexes was measured. Lc-Mass spectrum results, analysis of the elements C.H.N.S, measurement of molar conductivity, magnetic moment measurements have proven that azomethine compounds interacting with cadmium chloride and mercury acetate are di ligand.

Synthesis and characterization of novel thin films derived from pyrazole-3-one and its metal complex with bivalent nickel ion to improve solar cell efficiency

In this work, an organic ligand and its metal complex with Ni (II) ion was synthesized and used to improve solar cell efficiency. The organic Schiff base ligand, 4-(1, 3-benzodioxol-5-ylmethylideneamino)-1, 5-dimethyl-2-phenylpyrazole-3-one [L], was produced by condensation reaction of 4-aminoantipyrine with piperonaldehyde in absolute ethanol. The synthesized organic ligand [L] was characterized using 1H and 13C NMR, FT-IR, UV–Vis, elemental analysis (C.H.N), X-ray diffraction (XRD), mass spectrum, and atomic force microscope (AFM). The Ni (II) complex [M] was obtained in a molar ratio (2:1) (L:M). The prepared complex was characterized using X-ray diffraction (XRD), magnetic susceptibility measurement, elemental analysis (C.H.N), electrical molar conductivity, Fourier-transform infrared FT-IR, UV–Vis spectroscopy, atomic force microscope (AFM) and flame atomic absorption technique. Results suggested an octahedral geometry around the bivalent Ni (II) ion. Drop casting method was employed to prepare thin films of nanoparticles of the synthesized compounds. The optical, morphological, and structural properties for those particles were also studied and they were used to improve the silicon solar cell after the depositing on the silicon slides. The efficiency of the resulted inorganic solar cell was higher than the organic solar cell.

Synthesis, crystal growth, thermal and laser damage threshold properties of new Schiff base NLO material 4-Nitro-benzoic acid (3-ethoxy-2-hydroxy-benzylidene)-hydrazide

Novel organic Schiff base nonlinear optical material 4-Nitro-benzoic acid (3-ethoxy-2-hydroxy-benzylidene)-hydrazide (NEH) was synthesized and grown as single crystal by slow evaporation technique. The structure and unit cell parameter of NEH was confirmed by single crystal X-ray diffraction analysis and the crystal belongs to orthorhombic crystal system with noncentrosymmetric space group Pna21. Further both carbon and hydrogen NMR spectra confirm the formation of material and the presence of functional group was analyzed by Fourier Transform Infrared (FTIR) analysis. The optical absorption spectrum of the grown crystal shows the material has lower cut off wavelength at 320 nm. Thermal property of NEH was studied by TG/DTA analysis. The second harmonic nonlinear efficiency was accessed by Kurtz-Perry powder technique and it possesses an efficiency of 0.7 times that of standard KDP. The laser damage threshold of NEH crystal was found to be 3.22 GW/cm2.

A simple benzildihydrazone derived colorimetric and fluorescent ‘on–off-on’ sensor for sequential detection of copper(II) and cyanide ions in aqueous solution

Herein, we have developed a simple, environment friendly fluorescent turn-off and colorimetric sensor for the rapid detection of Cu2+ ions in aqueous solution by using organic Schiff base ligand benzildihydrazone-N,N'-bis(2-hydroxy-4-diethylamino-1-formylbenzene) (L). Binding interaction between L and various metal ions was established by UV–vis and fluorescent measurements showing favourable coordination towards Cu2+ and almost no interference with the other metal ions, i.e., Na+, Ba2+, Fe3+, Co2+, Ni2+, Zn2+, Cd2+, Ca2+, Hg2+, Pb2+,Cr3+, Ag+ and Al3+. L exhibited binding-induced colour change from yellow to light red. The obtained L-Cu2+ complex could be used as a new cascade sensor for detecting cyanide anion (CN−). The corresponding detection limits were found to be 7.3×10−10M for Cu2+ (lowest ever known in the family of fluorescent colorimetric Schiff base chemo-sensor) and 1.5×10−7M for CN−. To further assess the analytical performance of this sensing system, the concentrations of Cu2+ and CN−1 ions were determined in real water samples and simulated urine sample.

Evaluating corrosion inhibition property of some Schiff bases for mild steel in 1 M HCl: competitive effect of the heteroatom and stereochemical conformation of the molecule

Corrosion inhibition property due to the heteroatom present in organic Schiff bases and their stereochemical conformation is assessed. Three Schiff bases, namely 2-pyridyl-N-(2′-methylamino/methylthio/methoxy phenyl)methyleneimine are employed.

A combined experimental (XRD, FT-IR, and UV–Vis) and DFT computational studies on (E)-N-[4-bromo-2-(trifluromethoxy)phenyl]-1-(5-nitrothiophen-2-yl) methanimine

ABSTRACT(E)-N-[4-bromo-2-(trifluromethoxy)phenyl]-1-(5-nitrothiophen-2-yl)methanimine, an organic Schiff base compound has been synthesised and characterised by FT-IR, UV-Vis, and X-ray single-crystal determination. The molecular geometry from X-ray experiment in the ground state has been compared using the density functional theory (DFT)/B3LYP with the 6−311++G(d,p) basis set. The calculated results show that the DFT can well reproduce the crystal structure, and the calculated frequencies show good agreement with experimental values. The TD-DFT calculations were carried out using the B3LYP and CAM-B3LYP functionals with the 6−311++G(d,p) basis set to determine the maximum absorbtion wavelength of the UV-Vis spectra for the title compound. In addition, solvent effects on the excitation energies were computed through the integral equation formalism of the polarisable continuum model (IEF-PCM). The energetic and chemical reactivity behaviours of the title compound in solvent media have been examined using the B3LYP method with the 6−311++G(d,p) basis set by applying the IEF-PCM model. The non-linear optical properties are also addressed theoretically. According to the results, the title compound shows non-zero, the first hyperpolarisability value revealing second-order non-linear optic behaviour. Besides, DFT calculations of the molecular electrostatic potential, natural bond orbital analysis, and thermodynamic properties were also performed at B3LYP/6−311++G(d,p) level of theory.

Spectral, thermal and optical properties of N, N′-Bis (4-chlorobenzylidene)-3, 3′-dimethoxybiphenyl-4, 4′-diamine

Abstract One of the novel organic Schiff base materials, N,N′-Bis(4-chlorobenzylidene)-3,3′-dimethoxybiphenyl-4,4′-diamine (CBMPA), was synthesized and molecular structure of CBMPA was confirmed from nuclear magnetic resonance spectral analysis. Functional groups present in the compound were identified using Fourier transform infrared spectroscopy. Thermal studies show that the melting point of the material is at ~189 °C and it has a single-stage weight loss. Optical properties of CBMPA were studied using UV–vis–NIR and fluorescence spectral analyses. Optical nonlinearity of CBMPA was investigated at 532 nm using 5 ns laser pulses, employing an open aperture Z-scan technique. An optical limiting response which arises mostly from reverse saturable absorption was observed, and the effective two-photon absorption coefficient was calculated.