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In this study, a new Schiff base, (E)-2-(2-aminophenylthio)-N-(thiophen-2-yl-methylene) benzenamine was synthesized for selective detection of Hg2+. This Schiff base was characterized by proton nuclear magnetic resonance (1HNMR), carbon-13 nuclear magnetic resonance (13CNMR), and Fourier-transform infrared (FTIR) spectroscopy. Binding interaction between (E)-2-(2-aminophenylthio)-N-(thiophen-2-yl-methylene)benzenamine and various metal ions has been studied by UV–Vis spectroscopic measurements and shows promising coordination towards Hg2+ and almost no interference from other metal ions (Ag+, Mn2+, Fe3+, Al3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Fe2+ and Cr3+).This Schiff base exhibiting detection limit of 3.8 × 10− 8 M. The Schiff base newly synthesized in this study was successfully applied to the determination of Hg2+ in water samples. In addition to the experimental study, a theoretical study was conducted using Gaussian 09 program to support the experimental findings. FTIR, NMR, bond angle, bond length, torsional angles, and structural approximation were studied using theoretical consideration. [ABSTRACT FROM AUTHOR]

Removal of contaminants via adsorption and catalysis have received a significant interest as energy and money-saving solutions for treating the world's wastewater. Metal–organic frameworks (MOFs), a newly discovered class of porous crystalline materials, have demonstrated tremendous promise in the removal and destruction of contaminants for water purification. In order to improve the interactions of MOFs with the target pollutants for their selective removal and degradation, the Schiff base functionalities emerged as promising active sites. Through pre- and post-synthetic alterations, Schiff base functionalities are integrated into the pore cages of MOF adsorbent materials. To understand the adsorptive/catalytic mechanism, potential interactions between the Schiff base sites and the target pollutants are discussed. Based on cutting-edge techniques for their synthesis, this paper examines current developments in the creation of Schiff base–functionalized MOFs as innovative materials for adsorptive removal and catalytic degradation of contaminants for water remediation. [ABSTRACT FROM AUTHOR]

Pillar-layered metal-organic frameworks (PL-MOFs) are advanced crystalline porous substances built using metal ions, oxygen- and nitrogen-donor linkers. The pillar-layered strategy emerged as a very effective way to incorporate the Schiff base functionalities into pore cages of MOFs by using N-donor Schiff base pillar ligands. The Schiff base functionalities provide active sites for enhanced performance in sensing, catalysis, adsorption, extraction, and gas separation areas. Although the PL-MOFs have gained remarkable advances in the last few decades, Schiff base PL-MOFs have been reviewed to a lesser extent up to this point. In this way, a review summing up their performance is profoundly expected. This review covered the recent developments connected with Schiff base PL-MOFs, including synthesis and applicability in various potential fields. It also included the challenges and forthcoming pathways for fulfilling the research and development needs of Schiff base PL-MOFs. [ABSTRACT FROM AUTHOR]

Abstract—In this work, we have reported the synthesis of macrocyclic ligand and its nanostructured mononuclear Mn(II) and Cu(II) complexes using the sonication method. The spectral and elemental analyses have been done using UV–Vis spectroscopy, Fourier transform infrared (FT-IR) Spectroscopy, mass spectrometry, and carbon, hydrogen, and nitrogen elemental (CHN) analyses. The average size and surface morphological analysis of the synthesized nanocomplexes was evaluated using powder X-ray diffraction (XRD) and the field emission scanning electron microscopy (FE-SEM), respectively. The roughness of the nanostructured complexes was generalized by various statistical factors based on fractal studies. The results of the optical absorption data showed that the complexes have direct and indirect energy gap bands in the photon energy range from 2.33–4.31 eV. The various dispersion parameters like the refractive index, absorption index, dielectric constant, and optical conductivity were calculated and interpreted for the nanostructured complexes. The analysis of photoluminescent (PL) spectra showed that with the excitation wavelength of 260 and 460 nm, a strong band at 521 and 542 nm for Mn(II) and Cu(II), respectively, was observed in the emission spectrum. The obtained results indicate that the complexes can act as a promising candidate as green emitting light materials in electroluminescent and optoelectronic devices. The synthesized nanocomplexes were screened in vitro against fungal strains (Candida albicans and Aspergillus niger) and gram-positive bacterial strains (Listeria, Enterococcus faecalis, Bacillus subtilis and Staphylococcus aureus and gram-negative bacteria strains (Escherichia coli, Salmonella enterica, Acinetobacter calcoaceticus, Serratia marcescens) by the two-fold serial dilution method. The fractal and antimicrobial studies showed that Cu(II) complex is an excellent candidate to act as an antimicrobial agent. [ABSTRACT FROM AUTHOR]

A Schiff base functionalized Cu(II)-based metal–organic framework (MOF) denoted as Cu-L, was developed via a solvothermal method using low-cost starting material, i.e., Schiff base linker, 4,4'-(hydrazine-1,2-diylidenedimethylylidene)dibenzoic acid (L). Good crystallinity and thermal stability of synthesized Cu-L was confirmed by the crystallographic and thermogravimetric studies. An excellent photoluminescent properties of Cu-L ensure their suitability for the ultrafast detection of Fe3+ ions and nitrobenzene via a turn-off quenching response. The remarkable sensitivity of Cu-L towards Fe3+ ions and nitrobenzene was certified by the low limit of detection (LOD) of 47 ppb and 0.004 ppm, respectively. With incorporated free azine groups, this MOF could selectively capture Fe3+ ions and nitrobenzene in aqueous solution. The plausible mechanistic pathway for the quenching in the fluorescence intensity of the Cu-L in the presence of Fe3+ ions and nitrobenzene have been explained in detail through the density functional theory calculations, photo-induced electron transfer (PET), fluorescence resonance energy transfer (FRET), and competitive energy adsorption. This present study open a new avenue to synthesize novel crystalline MOF-based sensing materials from cheap Schiff base linkers for fast sensing of toxic pollutants. [ABSTRACT FROM AUTHOR]

A Schiff base bis(thiophen-2-yl-methylene)benzene-1, 4-diamine (L) was synthesized and used for selective and sensitive detection of Fe3+. L exhibited enhanced fluorescence response at excitation of 365 nm and emission wavelength of 440 nm for Fe3+. The formation of a 1:1 complex between L and Fe3+ was suggested by Job's plot by fluorescence titration and from optimized structures using Density functional theory (DFT). The fluorescence intensity was directly proportional to concentration of Fe3+ (R2 = 0.999) with the detection limit of 3.8 × 10–7 M and the binding constant of 1.20 × 104 M−1 at pH = 6.0. The probe was used to detect Fe3+ in different water samples with the percentage recovery of 99.7–103%. The interference of the other cations are < 5%. [ABSTRACT FROM AUTHOR]

By using Schiff base tricarboxylate ligand 5-(4-carboxybenzylideneamino)isophthalic acid (H3CIP), a new imine functionalized copper metal organic framework (MOF) has been synthesized solvothermally. It was fully characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and elemental mapping techniques. The as-synthesized MOF has been utilized as fluorescent probe for detection of nitro aromatic explosives (NAEs). The results show that the copper MOF can be developed into highly selective and sensitive sensor for detection of TNP in the aqueous medium via the "turn-off" quenching response. The linear fitting of the Stern-Volmer plot for TNP offered large quenching constant of 1.07 × 104 M−1 for Cu-MOF indicating the high sensitivity of the sensing process. Outstanding sensitivity of prepared material towards TNP detection was further validated by the low detection limit of 80 ppb (0.35 µM). The detailed mechanistic studies for their mode of action and density functional theory (DFT) calculations reveals that photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) processes, as well as electrostatic interactions (i.e. H-bonding) are the key factors for the turn-off response toward TNP by this fluorescent sensor. Thus, this new LMOF owing to their high water stability and remarkable functional features are potential candidates which can be developed into selective and sensitive TNP detection devices. [ABSTRACT FROM AUTHOR]

A new ion-selective polyvinyl chloride membrane electrode based on Schiff base [N,N′-bis(1-hydroxynaphthalene-2-carbaldehyde)-o-phenylenediamine] as an ionophore is successfully worked out as sensor for Zn(II) ions. The electrode shows excellent potentiometric response characteristics and displays a linear emf versus log[Zn2+] response over a wide concentration range of 1.0 × 10–7‒0.1 M with nernstian slope of 29.0 ± 0.1 mV/decade with the detection limit of 1.8 × 10–8 M. The sensor exhibits the advantages of fast response time (<10 s). The lifetime of the sensor is about 3 months. It was used as an indicator electrode in the potentiometric titration of Zn(II) with EDTA and for the determination of Zn(II) in pharma samples. The results were validated by using quantum mechanical density functional theoretical calculations. Theoretical studies proved prominent affinity of ligand towards Zn(II) ion. [ABSTRACT FROM AUTHOR]

Schiff bases and their metal complexes have become well-known for catalytic (e.g., in various synthetic processes) and biological properties (e.g., antifungal, antibacterial, anti-malarial, and antiviral characteristics) since their discovery by Hugo Schiff in 1864. As synthetic compounds, they are employed as versatile tools in numerous applications such as fluorescent turn-on/turn-off sensors for the determination of diverse analytes (e.g., metallic components). As such, they can offer a way to identify toxic ions and/or to provide their speciation in environmental media. This review covers a broad range of Schiff bases that are used in sensing applications for metallic cations and anions in various kinds of environmental and biological media. [ABSTRACT FROM AUTHOR]

Adsorptive removal of heavy metal ions from water is an energy- and cost-effective water decontamination technology. Schiff base functionalities can be incorporated into the pore cages of metal-organic frameworks (MOFs) via direct synthesis, post-synthetic modification, and composite formation. Such incorporation can efficiently enhance the interactions between the MOF adsorbent and target heavy metal ions to promote the selective adsorption of the latter. Accordingly, Schiff base-functionalized MOFs have great potential to selectively remove a particular metal ion from the aqueous solutions in the presence of coexisting (interfering) metal ions through the binding sites within their pore cages. Schiff base-functionalized MOFs can bind divalent metal ions (e.g., Pb(II), Co(II), Cu(II), Cd (II), and Hg (II)) more strongly than trivalent metal ions (e.g., Cr(III)). The adsorption capacity range of Schiff base-functionalized MOFs for divalent ions is thus much more broad (22.4–713 mg g−1) than that of trivalent metal ions (118–127 mg g−1). To evaluate the adsorption performance between different adsorbents, the two parameters (i.e., adsorption capacity and partition coefficient (PC)) are derived and used for comparison. Further, the possible interactions between the Schiff base sites and the target heavy metal ions are discussed to help understand the associated removal mechanisms. This review delivers actionable knowledge for developing Schiff-base functionalized MOFs toward the adsorptive removal of heavy metal ions in water in line with their performance evaluation and associated removal mechanisms. Finally, this review highlights the challenges and forthcoming research and development needs of Schiff base-functionalized MOFs for diverse fields of operations. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Progress in design/synthesis of Schiff base functionalized LMOF sensors is summarized. • The superiority of their sensing potential is supported by high sensitivities and selectivities. • They provide synergies of target specific Schiff base and MOFs with large surface areas. • This review is expected to disclose the current status of this research field and challenges. Luminescent metal–organic frameworks (LMOFs) are porous crystalline materials consisting of metal clusters and organic linkers. Although LMOFs belong to a subcategory of MOFs, they are superior to typical MOFs in many ways (e.g., in terms of photostability, sensing ability, ease of use, interactions with target analytes, and rapid detection mechanisms). Schiff bases with various desired functionalities can be incorporated into the pore cages of LMOF materials via pre- and post-synthetic modifications. Such functionalities can be used to favorably provide active sites for the selective detection of various target components (e.g., metal ions, anions, biomolecules, explosives, gases, and light molecular weight solvent molecules). This work reviews the recent progress achieved in the development of Schiff base-functionalized LMOF sensors for diverse target substances based on state-of-the-art approaches available for their synthesis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Owing to high porosity, MOFs emerged as a new class of support materials. • Anchorage of Schiff base complexes onto MOFs enhances their catalytic performance. • Various PSM approaches for Schiff base complex-anchored MOFs are reviewed. • The PSM MOFs are good as both heterogeneous and homogeneous catalysts. • High yield and TOF of Schiff base complex-anchored MOFs affirm their superiority. Metal-organic frameworks (MOFs), built through the interconnection between metal clusters and di- to poly-topic organic linkers, have porous crystalline and tunable structures with many meritful properties such as robustness, high surface area/porosity, and adjustable pore size. As such, MOFs have drawn a great deal of attention in the design of the advanced heterogeneous catalytic materials. As the distribution of the catalytically active sites can be controlled further via post-synthesis modification (PSM), the use of Schiff base for such PSM is considered a promising strategy to develop highly active as well as stable catalysts. The great utility of Schiff base complex-anchored MOF is in fact recognized from various catalytic reactions (e.g., coupling, epoxidation, hydrogenation, and oxidation) through efficient coordination of metal ions. These catalysts are advantageous to overcome the common limitations of both homogeneous catalysis (e.g., poor recyclability as well as reusability) and heterogeneous catalysis (e.g., low activity). This review is hence expected to deliver actionable knowledge for the development of highly effective Schiff base/MOF catalysts via PSM for diverse catalytic applications. [ABSTRACT FROM AUTHOR]

In this study, a quantum chemical model was developed to better account for the properties of a Schiff base, (Z)-1-(thiophen-2-yl-methyleneamino) propane-2-ol, which is derived from thiophene-2-carboxy aldehyde and 1-amino-2-propanol. To predict its molecular structure, the assignment of the vibrational wavelength (for FT-IR) and chemical shift (for 1HNMR) of (Z)-1-(thiophen-2-yl-methyleneamino) propane-2-ol was performed experimentally and theoretically. All of the theoretical calculations were performed using the Gaussian 09 program package. The theoretically and experimentally obtained results were in good agreement (R2 ≥ 0.99). The energies of the highest occupied and lowest unoccupied molecular orbitals were estimated using B3LYP (Becke three-parameter hybrid functional combined with Lee–Yang–Parr correlation functional)/6-311++G (d, p). Optimization of the structure of (Z)-1-(thiophen-2-yl-methyleneamino) propane-2-ol provided information concerning the stable form of the geometry of the molecule, stoichiometry of the complexes, and thermodynamic parameters (e.g., energy and entropy). The results indicate that the Schiff base formed stable complexes with Ni2+. The energy of the complex was much lower than that of the free Schiff base. The charge distribution values of each atom in the Schiff base were in agreement with the Pauling scale for electronegativity and vibrational wavelength. Image 1 • Experimental and Theoretical study of (Z)-1-(thiophen-2-yl-methyleneamino) propane-2-ol was investigated. • The vibrational FTIR wavelength and chemical shift (for 1HNMR) were studied with DFT studies. • (Z)-1-(thiophen-2-yl-methyleneamino) propane-2-ol formed a more stable complex with Ni2+. • Bond lengths and bond angles were calculated to characterize its strength. • HOMO -LUMO energy gap of the Schiff base was calculated. [ABSTRACT FROM AUTHOR]