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The structural and electronic behavior of thiosemicarbazone (TSC)-based metal complexes of Mn (II), Fe (II), and Ni (II) have been investigated. The synthesized metal complexes were characterized using elemental analysis, magnetic susceptibility, molar conductivity, FTIR, and UV–Vis spectroscopy, the computational path helped with further structural investigation. The solubility test on the TSC and its complexes revealed their solubility in most organic solvents. DFT computational analysis was performed, and quantum reactivity parameters of the octahedral optimized complexes were calculated to describe the reactivity via the stability states of the synthesized complexes. FMOs map was generated to confirm similar findings and MEP analysis was applied to elaborate the important electrophilic and nucleophilic sites on the studied surfaces. Also, other important topological analyses such as electron localization function and reduced density gradient, to establish the favorable noncovalent interactions, were studied. In silico molecular docking approach was studied against the gram-positive bacteria Bacillus cereus to predict the potent inhibition behavior of the studied complexes. The findings summarized the inhibition prediction of the most interactive [NiL2Cl2], then [FeL2Cl2] complexes as confirmed by the binding energy values (− 7.1 kacl/mol and − 6.4 kacl/mol, respectively). Another In silico results, with gram-positive bacteria (S. aureus), estimated similar results of the experimental finding, where [MnL2Cl2] (− 9.2 kcal/mol) is the more effective predicted antibacterial inhibitor. Fluorescence microscopy was used to examine the inhibition of bacterial biofilm, and the DPPH assay was used to measure antioxidant activity, followed by an understanding of the behavior of the current complexes toward free radicals' removal. The findings observed less aggregated bacterial strains covered with the studied complexes leading to less dense biofilm covering. [ABSTRACT FROM AUTHOR]

This review basically concerned with the application of different Schiff bases (SB) based fluorimetric (turn-off and turn-on) and colorimetric chemosensors for the detection of heavy metal cations particularly Al(III), Fe(III), and Cr(III) ions. Chemosensors based on Schiff bases have exhibited outstanding performance in the detection of different metal cations due to their facile and in-expensive synthesis, and their excellent coordination ability with almost all metal cations and stabilize them in different oxidation states. Moreover, Schiff bases have also been used as antifungal, anticancer, analgesic, anti-inflammatory, antibacterial, antiviral, antioxidant, and antimalarial etc. The Schiff base also can be used as an intermediate for the formation of various heterocyclic compounds. In this review, we have focused on the research work performed on the development of chemosensors (colorimetric and fluorometric) for rapid detection of trivalent metal cations particularly Al(III), Fe(III), and Cr(III) ions using Schiff base as a ligand during 2020-2022. [ABSTRACT FROM AUTHOR]

This study describes the techniques used for the synthesis and characterization of mononuclear, heterocyclic ligated complexes of Zn(II), Mn(II), and Sn(II). A heterocyclic Schiff base derivative, specifically (E)-2-((benzo[b]thiophen-3-yl)methyleneamino)butanoic acid, has been synthesized by the reaction of benzo[b]thiophene-3-carbaldehyde with 2-aminobutanoic acid. This Schiff base has been reacted with different (M)Cl2 to synthesize the respective metal complexes. For these metal ions, Schiff bases have been proven experimentally to form four-coordinate complexes with 1 : 2 (metal : ligand) ratio. The structural changes of the complexes have been investigated using FT-IR, mass, 1H NMR, 13C NMR spectra, and TGA analysis. The antibacterial efficacy of the Schiff base and its complexes has further been assessed and discussed. Significant amounts of antibacterial and antifungal activity of metal(II) complexes against tetracycline and ketoconazole have been identified. [ABSTRACT FROM AUTHOR]

Two isostructural mononuclear cadmium(II) and nickel(II) complexes [Cd(HL)2(NCS)2]∙4CH3OH (1) and [Ni(HL)2(NCS)2]∙4CH3OH (2), where HL is the zwitterionic form of the Schiff base 2,4-difluoro-6-[(2-pyrrolidin-1-ylethylimino)methyl]phenol (HL), were prepared and characterized by elemental analysis, infrared and electronic spectroscopy, as well as X-ray single crystal determination. In both complexes the metal atoms are in octahedral coordination. The Schiff base ligands are coordinate to the metal atoms through phenolate oxygen and imino nitrogen. Molecules of the complexes are stabilized by hydrogen bonds. The biological assay indicates that the complexes have good antimicrobial activities on the bacteria strains Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

Water contamination by hazardous heavy metal ions and organic compounds causes environmental damage towards aquatic species and human health. Thus the evolution of highly selective, affordable, rapid and effective analytical tools for the removal and detection of toxic heavy metal ions and organic compounds in aqueous environments is a challenging objective. Electrochemical detection of metal ions and organic compounds is a very useful and effective method, where modified electrodes with metal nanocomposite particles are used. Materials with high porosity, low-charge transfer resistance and large electroactive area are desirable for electrode modification in order to act as an efficient electrochemical sensor. It has been established that natural polysaccharide-based graft copolymers with acrylic monomers can be efficiently used as 'bio-template' for preparing mono and bimetallic/metal oxide composite nanoparticles for sensing and catalytic applications. This is because of the fact that polysaccharide-based graft copolymers are eco-friendly in nature and have the potential to act as reducing and stabilizing agents. The bio-template-based metal/metal oxide nanocomposites are successfully used for the electrochemical sensing of some heavy metal ions, like Hg2+, Cd2+, Th4+, Zn2+, Pb2+, etc., and toxic phenolic compounds, and also show efficient catalytic application in azo dye degradation and p-nitrophenol reduction. The developed electrochemical sensors are selective, sensitive and effective for the detection of toxic heavy metal ions in real water samples. Here we summarize the various investigations carried out using metal/metal oxide nanocomposite particles (mono and bimetallic) in electrochemical sensing of toxic heavy metal ions and catalytic applications. [ABSTRACT FROM AUTHOR]

New cyclotriphosphazene derivatives featuring amide–Schiff base linkages with a hydrazine bridge and different terminal ends, such as decyl alkyl chains and hydroxy groups, were successfully synthesized and characterized. Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and CHN elemental analysis were used to characterize the structures of these compounds. The formation of hydrazine-bridged cyclotriphosphazene derivatives with amide–Schiff base linkages was confirmed by the FTIR spectra, showing a primary amine band for the amide linkage around ~3300 cm−1 and a band for the Schiff base linkage near ~1595 cm−1. This was further supported by NMR analysis, which displayed an amide proton (H-N-C=O) at ~δ 10.00 ppm and an azomethine proton (H-C=N) within the δ 8.40–8.70 ppm range. The 31P NMR spectra of cyclotriphosphazene compounds display a singlet at ~δ 8.20 ppm, indicating an upfield shift that suggests the complete substitution of all phosphorus atoms with identical side chains. Furthermore, CHN analysis verified the purity of the synthesized compounds, with a percentage error below 2%. The introduction of hydrazine bridges and amide–Schiff base linkages into the cyclotriphosphazene core significantly enriches the molecular structure with diverse functional groups. These modifications not only improve the compound’s stability and reactivity, but also expand its potential for a wide range of applications.

Organometallic drug development is still in its early stage, but recent studies show that organometallics having iron as the central atom have the possibility of becoming good drug candidates because iron is an important micro-nutrient, and it is compatible with many biological systems, including the human body. Being an eco-friendly Lewis acid, iron can accept the lone pair of electrons from imino(sp2)-nitrogen, and the resultant iron–imine complexes with iron as a central atom have the possibility of interacting with several proteins and enzymes in humans. Iron–imine complexes have demonstrated significant potential with anticancer, bactericidal, fungicidal, and other medicinal activities in recent years. This article systematically discusses major synthetic methods and pharmacological potentials of iron–imine complexes having in vitro activity to significant clinical performance from 2016 to date. In a nutshell, this manuscript offers a simplistic view of iron complexes in medicinal inorganic chemistry: for instance, iron is presented as an "eco-friendly non-toxic" metal (as opposed to platinum) that will lead to non-toxic pharmaceuticals. The abundant literature on iron chelators shows that many iron complexes, particularly if redox-active in cells, can be quite cytotoxic, which can be beneficial for future targeted therapies. While we made every effort to include all the related papers, any omission is purely unintentional. [ABSTRACT FROM AUTHOR]

A new iron(III) complex (Et3NH)2[Fe(L)2](ClO4)·MeOH (1) where H2L = 2-{(E)-[2-hydroxyphenyl)imino]methyl}phenol has been synthesised and characterised by single crystal XRD, elemental analysis and DC magnetic susceptibility measurements. The dianionic ligands L2− coordinate in a tridentate fashion with the Fe(III) through their deprotonated phenolic oxygens and azomethine nitrogen atoms, resulting in a trans-FeO4N2 chromophore. Variable-temperature magnetic measurements were performed between 300 and 5 K under an applied field of 0.1 T and show that 1 is in the high spin state (S = 5/2) over the whole measured temperature range. This is confirmed by Mössbauer spectroscopy at 77 and 300 K.

Schiff-base fluorescent chemosensor (E)-N-(4-(dimethylamino)benzylidene)quinolone-3-amine (DBQA) was synthesized and characterized by FT-IR,1H NMR,13C NMR, ESI-MS spectrometry and Single X-ray crystallographic studies. The synthesized chemosensor (DBQA) was used for the detection of Fe3+ successfully. UV-visible and fluorescence spectra of (DBQA) exhibits a ratiometric behaviour along with a bathochromic shift upon the successive addition of Fe3+. The fluorescence spectra of chemosensor (DBQA) were recorded followed by addition of concentrations of different metal ions and NH3. The chemosensor (DBQA) showed a favourable linear relationship between the fluorescence intensity and concentration of Fe3+ ion. DBQA exhibits a ratiometric response and illustrates high sensitivity (with a detection limit of 0.4 ​μM) and good selectivity for the Fe3+ ion over other transition metal ions. DBQA shows 0.6 ​μM detection limit for NH3 along with ratiometric behaviour also. The association constant (Ka) of chemosensor (DBQA) was found to be 1.455×102 ​M-1/2 for Fe3+. The mechanism of sensing of the present ratiometric fluorescent chemosensor (DBQA) was explained by ICT (Intra-molecular charge transfer) using DFT calculations. The interaction model of chemosensor (DBQA) with Fe3+ was determined to be 2:1 stoichiometry using Job's plot analysis and ESI-MS spectra which further confirms DFT studies. Moreover, tested DBQA ​+ ​Fe3+ was showed that remarkable anticancer activity against the HCT116 colon cancer cells by MTT assay. Novelty and importance of DBQA as it can be investigate, test or analyse of detect Fe3+ rapidly as compared to other tested ions. Lastly, DBQA can be investigate, test or analyse of Fe3+ in environmental and biological samples.

2-(((2,7-Dihydroxynaphthalen-1-yl)methylene)amino)-3′,6′-bis(ethylamino)-2′,7′-dimethylspiro[isoindoline-1,9′-xanthen]-3-one was synthesized using Rhodamine 6G hydrazide (prepared using literature methods) and commercially available 2,7-dihydroxynaphthalene-1-carbaldehyde via imine condensation. Structural characterization was performed using FT-IR, 1H-NMR, 13C-NMR, X-ray, and HRMS. This Schiff base shows promise as a ligand for the colorimetric analysis of uranium in water.

A new cobalt(III) complex with a pentadentate Schiff base was synthesized using a reaction of 2,2′-{(2-hydroxypropane-1,3-diyl)bis(nitriloeth-1-yl-1-ylidene)}diphenol (H3L) and cobalt(II) acetate in a methanolic solution. This synthesis resulted in the isolation of dinuclear compound [CoIII2L2] (1), which was characterized using elemental analyses and XRF, FTIR, and TG/DSC techniques. The molecular structure of the complex was confirmed using single-crystal X-ray diffraction. The structure of 1 consists of a centrosymmetric dimer in which two crystallographically equivalent cobalt(III) ions are bridged by two alkoxido oxygen atoms. In addition, each metal center is coordinated by two Schiff bases.

In this short note, we elaborate on a synthetic method for a new terpyridine Schiff base-bearing vanillin motif. The structure of the product was confirmed via 1H and 13C-NMR spectroscopy and FT-IR spectroscopy. Due to the peculiar coordination nature and optical property of the synthesized compound, this work presents a promising colorimetric sensing molecular compound.

The reaction of 3-benzoylpyrrolo[2,1-c][1,4]benzoxazin-1,2,4-trione with N-(4-bromophenyl)-1-(4-methoxyphenyl)methanimine under thermolytical conditions afforded 4-benzoyl-2-(4-bromophenyl)-1-(4-methoxyphenyl)-1,2-dihydropyrimidino[4,3-c][1,4]benzoxazine-3,5-dione in a good yield. The reaction proceeded via in situ generation of a reactive intermediate, acyl(imidoyl)ketene. The compound was fully characterized.

In this study, the synthesis of a Schiff base containing metal–organic frameworks (MOFs) of the UiO-67 family has been investigated. MOFs featuring free amine groups were successfully synthesized under mild solvothermal conditions using 2-amino-[1,1′-biphenyl]-4,4′-dicarboxylic acid and 2,2′-diamino-[1,1′-biphenyl]-4,4′-dicarboxylic acid as bridging ligands, resulting in MOFs with amine groups covalently linked to the bridging ligands. Both types of functionalized MOFs were post-synthetically modified with 4-formylbenzonitrile that resulted in imine formation. All the obtained compounds were characterized by PXRD, TGA, DTA, BET, NMR, and FTIR spectroscopy, while stability in water was monitored with SEM, EDS, and UV–VIS spectroscopy.

The Schiff base reaction of imidazole-2-carboxaldehydes with the anion of alanine, leucine and phenylalanine in the presence of nickel(II) ion gives the neutral NiL2 complexes. The Schiff base ligand, L, binds through an imidazole nitrogen, NIm, the amino acid nitrogen, NAA, and a carboxylate oxygen, O, atom. The two N2O ligands bind to the nickel(II) in a meridional fashion with the NIm and O of each ligand in trans positions. These ligands can exist as the anticipated aldimine, Im − CH = NAA − CH(R) − CO2−, or the ketimine, Im − CH2NAA = C(R) − CO2−, tautomer. Tautomerization of the initially formed aldimine Schiff base results in movement of the hydrogen atom of the alpha carbon of the amino acid to the aldehyde carbon, CAld, atom of the imidazole carboxaldehyde with resultant relocation of the imine double bond in the reverse direction. Ten structures of the structurally unprecedented ketimine tautomer, prepared from imidazole-2-carboxaldehydes and a pyrazole-3-carboxaldehyde, were presented. The structural data supported the formation of the ketimines in each case, while the aldimine tautomer was observed with imidazole-4-carboxaldehydes. A rationale of this can be explained on the basis of charge distribution in the likely intermediate in the tautomerization.

The article presents the synthesis and properties of two new Schiff bases of resorcinarene derivatives. The Schiff bases were obtained by the reaction of formylresorcinarene with aromatic (o-aminophenol) and aliphatic (N,N-dimethyldiaminoethane) amines in chloroform. The synthesized Schiff bases exist in equilibrium of several tautomers, as evident from the IR, UV, NMR spectra and cyclic voltammetry data analysis. In DMF, methanol, and acetonitrile, the tautomeric equilibrium is shifted toward the enol-imine tautomers.

The two complexes, [Ni(DPPT)2](NO3)2*1.5H2O (1) and [Ni(DPPT)(NO3)Cl].EtOH (2), were synthesized using the self-assembly of (E)-2,4-di(piperidin-1-yl)-6-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)-1,3,5-triazine (DPPT) with Ni(NO3)2*6H2O in the absence and presence of NiCl2*6H2O, respectively. In both cases, the neutral tridentate DPPT ligand is found coordinated to the Ni(II) via three N-atoms from the hydrazone, pyridine and s-triazine rings. Hence, the homoleptic complex 1 has a NiN6 hexa-coordination environment while two NO3− are counter anions in addition to one-and-a-half crystallized hydration water molecules are found acting as an outer sphere. The heteroleptic complex 2 has a NiN3O2Cl coordination sphere where the coordination environment of the Ni(II) is completed by one bidentate nitrate and one chloride ion leading to a neutral inner sphere while the outer sphere contains one crystallized ethanol molecule. Both complexes have distorted octahedral coordination environments around the Ni(II) ion. Using Hirshfeld analysis, the intermolecular contacts H…H and O…H in 1 and the Cl…H, O…H, N…H, H…H, C…H and C…C in 2 are found to be the most important for crystal stability. The antimicrobial activity of complexes 1 and 2 was assessed against different bacterial and fungal strains, and the results were compared with the free ligand as well as the antibacterial (Gentamycin) and antifungal (Ketoconazole) positive controls. Both Ni(II) complexes are better antibacterial and antifungal agents than the free ligand. Interestingly, both Ni(II) complexes have similar antifungal activity against C. albicans compared to Ketoconazole.

The title compound, N′1,N′4-bis(2-(7,8-dimethyl-2,4-dioxo-3,4-dihydrobenzo[g]pteridin-10(2H)-yl)ethylidene)succinohydrazide (1), was obtained by the reaction of formylmethylflavin and succinic acid dihydrazide. The product 1 was characterized by 1H-NMR, 13C-NMR, HRMS and UV.

A synthesis of 2-((4-phenyl-5-(2-(p-tolylamino)ethyl)-4H-1,2,4-triazol-3-yl)thio)-N’-(1-phenylethylidene)acetohydrazide from 2-[(3-{2-[(4-methylphenyl)amino]ethyl}-4-phenyl-4,5-dihydro-1H-1,2,4-triazol-5-yl)sulfanyl]acetohydrazide and acetophenone is reported. The title compound has been tested to possess 1.5-fold higher antioxidant ability than the control, butylated hydroxytoluene, as determined by a Ferric reducing antioxidant power assay.

This paper explores a dual inhibition of main protease (Mpro) and nonstructural protein 10/nonstructural protein 16 (NSP16) methyltransferase complex as the key targets for COVID-19 therapy. These are based on the new Schiff-base ligand that was obtained from the condensation of (4-chloro-3-methyl phenyl) hydrazine with 2-pyridine-carboxaldehyde and its novel Schiff-base metal complexes. These include Ni(II), Pd(II), Pt(II), Zn(II), and Hg(II). The newly synthesized compounds have been characterized using FT-IR, 1H NMR, 13C NMR, and elemental analysis. The results suggested that the Schiff-base ligand is coordinated as a bidentate ligand through the nitrogen atoms of the azomethine group and pyridyl ring. In addition, the biological activity of the prepared complexes was examined against Pseudomonas aeruginosa and Staphylococcus aureus, and the results showed that the Zn(II) complex has the highest activity compared with other compounds. The active sites were found by looking at the molecular electrostatic potential (MEP) maps of the above ligands and complexes. The activity of the compound and its Ni(II) and Zn(II) complexes against Mpro and NSP10/ NSP16 was investigated using a molecular docking approach. They showed excellent binding energies ranging from −5.9 to −7.2 kcal/mol and −5.8 to −7.2 for Mpro and NSP16, respectively. All conformers of the metal complexes were docked with the active site of the NSP16 receptor, showing a binding affinity of 100%. According to our knowledge, this was the first report of these metal complexes as dual inhibitors for Mpro and NSP16 of SARS-CoV-2.

The newly synthesized biphenyldicarboxylic acid Schiff base and its complexes with Cu(II) were synthesized, and their spectroscopic and structural analysis was performed. The reaction of the ligand and copper(II) acetate in different solvents resulted in the formation of two solvatomorphic complexes, one with MeOH, and the other with DMF molecules, in the crystal lattice. The differences in the results of the thermal analysis could be explained by the different polarities of the solvents present. SC-XRD analysis revealed that the ligand is coordinated as a dianion, in a pentadentate manner, through two phenoxide oxygen atoms, two azomethine nitrogen atoms, and with the oxygen atom of one carboxylate functioning as a bridge that connects the monomeric units. The coordination polyhedron was described with several parameters obtained from different methods of calculation. The presence of different solvents in the crystal structure results in differences in the H-bond networks, and an overall different crystal packing of the structural units in the obtained complexes.

A novel approach was carried to prepare trans-CuCl2L2 complex with the ligand L, (E)-(4-chlorophenyl)-N-(3-phenyl-4H-1,2,4-triazol-4-yl)methanimine which was formed in situ during the reaction of CuCl2 with 4-(4-chlorobenzylideneamino)-5-phenyl-2H-1,2,4-triazole-3(4H)-thione. The synthesized compounds were characterized by applying various spectroscopic techniques. The crystal structure of the complex was unambiguously determined using X-ray analysis indicating square planar geometry. Intermolecular H-bonds govern the supramolecular structure of the copper complex. Aromatic rings are stacked in an offset packing due to occurrence of π–π interactions. The structure is further corroborated with a detailed computational investigation. A thione–thiol tautomerism for the triazole compound was also studied. The Schiff base 1,2,4-triazole copper chloride complex is expected to have high anticancer activity.

The impetus for research into hydrogels based on selectively oxidized polysaccharides has been stimulated by the diversity of potential biomedical applications. Towards the development of a hemostatic wound dressing in this study, we creatively combined the (hemi)acetal and Schiff base bonds to prepare a series of multifunctional cryogels based on dialdehyde pullulan and dopamine. The designed structures were verified by NMR and FTIR spectroscopy. Network parameters and dynamic sorption studies were correlated with environmental scanning microscopy results, thus confirming the successful integration of the two components and the opportunities for finely tuning the structure–properties balance. The viscoelastic parameters (storage and loss moduli, complex and apparent viscosities, zero shear viscosity, yield stress) and the structural recovery capacity after applying a large deformation were determined and discussed. The mechanical stability and hemostatic activity suggest that the optimal combination of selectively oxidized pullulan and dopamine can be a promising toolkit for wound management.

In recent decades, concerns about increasing biological and environmental contamination have necessitated the development of chemosensors with high selectivity, sensitivity, and cost-effectiveness. In principle, the sensing performance can be affected by the functional group(s) of receptor, the charge of the metal ion(s), and the electron configuration of the sensing molecule(s)e and metal ion(s). Fine controlling of the substituents can influence the electron density of the receptor to enhance the binding affinity to metal ions, which is an effective way to improve the photophysical properties of the sensors. This review explores the effect of functional group modification on the performance of various chemosensors represented by Pt(dithiolene)-based complexes (2012–2021). Then, recently developed Schiff base chemosensors (2014–2021) are discussed. The Schiff base is a good platform for controlling electron configuration due to a facile synthesis of various organic structures (aldehyde or ketone groups with primary amine derivatives). The discussion focuses on the detection type, physicochemical and optical properties, and applications of these chemosensors.

In the reaction of zinc(II) sulfate and the chloride salt of 2-acetylpyridine-aminoguanidine, two types of complex were obtained, i.e., [Zn(H2O)6](H2L)2(SO4)3·3H2O and [Zn(L)H2O(SO4)]·H2O, depending on the presence of LiOAc as the deprotonating agent. The physicochemical, structural, and photoluminescence properties of the complexes were examined. In the first complex, obtained in the absence of LiOAc, the Schiff base had the role of a counter-ion in its doubly protonated form, while in the presence of LiOAc, upon deprotonation, coordination takes place, and thus the Schiff base acts as a tridentate N3 ligand. In the latter complex, the ligand is coordinated through pyridine, azomethine, and the imino nitrogen of the aminoguanidine residue, leading to formation of two fused five-membered chelate rings. Both the examined complexes, as well as the ligand itself, show high photoluminescence.

Herein, we report the chromatography-free synthesis of 2-hydroxy-3-octyloxybenzaldehyde by the alkylation of 2,3-dihydroxybenzaldehyde as a promising precursor for new SalEn-type complexes with transition metals. The structure of the product is elucidated by means of 1H and 13C-NMR spectra, high-resolution mass spectrometry with electrospray ionization (ESI-HRMS) and Fourier-transform infrared spectroscopy (FTIR).

After making a new series of spiro[cycloalkane]pyridazinones with high Fsp3 character available, the new target was to synthesize derivatives comprising nitrogen-containing heterocycles, such as triazolo or tetrazolo rings. The corresponding thioxo derivatives (1a,b) seemed to be good starting materials for the synthesis of tetrazolo derivatives. The reaction of the pyridazinethiones (1a,b) with hydrazine surprisingly resulted in Schiff bases (3a,b) deriving from the reaction of hydrazones (2a,b) with acetone.

Iron(II)-Schiff base complexes are a well-studied class of spin-crossover (SCO) active species due to their ability to interconvert between a paramagnetic high spin-state (HS, S = 2, 5T2) and a diamagnetic low spin-state (LS, S = 0, 1A1) by external stimuli under an appropriate ligand field. We have synthesized two mononuclear FeII complexes, viz., [Fe(L1)2](ClO4)2.CH3OH (1) and [Fe(L2)2](ClO4)2.2CH3CN (2), from two N6–coordinating tridentate Schiff bases derived from 2,6-bis[(benzylimino)methyl]pyridine. The complexes have been characterized by elemental analysis, electrospray ionization–mass spectrometry (ESI-MS), Fourier-transform infrared spectroscopy (FTIR), solution state nuclear magnetic resonance spectroscopy, 1H and 13C NMR (both theoretically and experimentally), single-crystal diffraction and magnetic susceptibility studies. The structural, spectroscopic and magnetic investigations revealed that 1 and 2 are with Fe–N6 distorted octahedral coordination geometry and remain locked in LS state throughout the measured temperature range from 5–350 K.

A mononuclear Co(II) complex of a Schiff base ligand derived from 5-Bromo-vanillin and 4-aminoantipyrine, that has a compressed tetragonal bipyramidal geometry and exhibiting field-induced slow magnetic relaxation, has been synthesized and characterized by single crystal X-ray diffraction, elemental analysis and molecular spectroscopy. In the crystal packing, a hydrogen-bonded dimer structural topology has been observed with two distinct metal centers having slightly different bond parameters. The complex has been further investigated for its magnetic nature on a SQUID magnetometer. The DC magnetic data confirm that the complex behaves as a typical S = 3/2 spin system with a sizable axial zero-field splitting parameter D/hc = 38 cm−1. The AC susceptibility data reveal that the relaxation time for the single-mode relaxation process is τ = 0.16(1) ms at T = 2.0 K and BDC = 0.12 T.

Three new Schiff bases of isoniazid were synthesized using microwave-assisted synthesis and conventional condensation with aromatic aldehydes. Synthesized compounds were characterized using elemental analysis, IR, NMR, and Mass spectroscopy. Synthesized compounds were evaluated for antiproliferative activity against MCF-7 cell line. The IC50 values were from 125 to 276 µM. The compounds were also evaluated for antibacterial activity against Staphylococcus aureus and Escherichia coli. Results showed that the synthesized compounds produce significant antibacterial activity in vitro. Inhibition of compounds ranged from 13 to 18 mm.

A novel Cu(II) complex based on the Schiff base obtained by the condensation of ortho-vanillin with gamma-aminobutyric acid was synthesized. The compounds are physico-chemically characterized by elemental analysis, HR-ESI-MS, FT-IR, and UV-Vis. The complex and the Schiff base ligand are further structurally identified by single crystal X-ray diffraction and 1H and 13C-NMR, respectively. The results suggest that the Schiff base are synthesized in excellent yield under mild reaction conditions in the presence of glacial acetic acid and the crystal structure of its Cu(II) complex reflects an one-dimensional polymeric compound. The molecular structure of the complex consists of a Cu(II) ion bound to two singly deprotonated Schiff base bridging ligands that form a CuN2O4 chelation environment, and a coordination sphere with a disordered octahedral geometry.

A tetranuclear dysprosium Schiff base complex was isolated by reacting dysprosium chloride with 2-hydroxy-3-methoxybenzaldehyde and 2-(aminomethyl)pyridine in-situ under basic conditions. The isolated Dy(III) complex was characterized by elemental analyses, single crystal X-ray diffraction and molecular spectroscopy. The complex crystallizes in the triclinic space group P-1 with unit cell parameters of a = 10.2003 (4), b = 13.8602 (5), c = 14.9542 (6), α = 94.523 (3), β = 109.362 (4), and γ = 99.861 (3). The magnetic properties of 1 have been investigated by DC and AC susceptibility measurements. The DC measurements reveal weak exchange coupling of antiferromagnetic nature. In the AC measurement, the complex shows a slow relaxation of magnetization in the absence of an external magnetic field.

Two new oxidovanadium(V) complexes, (HNEt3)[VVO2L] (1) and [(VVOL)2μ-O] (2), have been synthesized using a tridentate Schiff base ligand H2L [where H2L = 4-((E)-(2-hydroxy-5-nitrophenylimino)methyl)benzene-1,3-diol] and VO(acac)2 as starting metal precursor. The ligand and corresponding metal complexes are characterized by physicochemical (elemental analysis), spectroscopic (FT-IR, UV–Vis, and NMR), and spectrometric (ESI–MS) methods. X-ray crystallographic analysis indicates the anion in salt 1 features a distorted square-pyramidal geometry for the vanadium(V) center defined by imine-N, two phenoxide-O, and two oxido-O atoms. The interaction of the compounds with CT–DNA was studied through UV–Vis absorption titration and circular dichroism methods. The results indicated that complexes showed enhanced binding affinity towards DNA compared to the ligand molecule. Finally, the in vitro cytotoxicity studies of H2L, 1, and 2 were evaluated against colon cancer (HT-29) and mouse embryonic fibroblast (NIH-3T3) cell lines by MTT assay. The results demonstrated that the compounds manifested a cytotoxic potential comparable with clinically referred drugs and caused cell death by apoptosis.

The breakthrough in Ln(III)-based SMMs with Schiff base ligands have been occurred for the last decade on account of their magnetic behavior, anisotropy and relaxation pathways. Herein, we review the synthetic strategy, from a structural point of view and magnetic properties of mono, di, tri and polynuclear Ln(III)-based single-molecule magnets mainly with Schiff bases of Salicylaldehyde origin. Special attention has been given to some important breakthroughs that are changing the perspective of this field with a special emphasis on slow magnetic relaxation. An overview of 50 Ln(III)-Schiff base complexes with SMM behavior, covering the period 2008–2020, which have been critical in understanding the magnetic interactions between the Ln(III)-centers, are presented and discussed in detail.

Condensation of 1,3-diaminopropan-2-ol with 9-ethyl-9H-carbazole-3-carbaldehyde in absolute ethanol under stirring condition resulted in the formation of 1,3-bis{[(E)-(9-ethyl-9H-carbazol-3-yl)methylidene]amino}propan-2-ol within 0.5 in an excellent yield. The structure of the desired Schiff base was physically analyzed via CHN-elemental analysis, TOF-MS, UV-vis, FT-IR, and 1H & 13C-NMR. Computational studies of the structure were performed at the DFT/B3LYP/6-311++G(d) level of theory. Molecular electrostatic potential (MEP), Mulliken charge, IR-B3LYP, and structure optimization were performed.

In the world of science, in particular the section concerning the field of chemistry, when the results encountered during the experiment do not meet our expectations, our shrewdness may play an important role to open up new unexplored fields that could be much more interesting than what we were seeking. In those cases, our research undergoes an unforeseen shift, delivering novel and challenging results that may altogether alter our point of view and our future work. We have then struck serendipity. Specifically, in our investigation linked to palladacycles we have found that the new trends in their reactivity, as well as in their structure, have been, in many cases, related to this experience, broadening our research scope within this field. Herein, we describe our most relevant findings, which have shed new light upon the reactivity of palladacycles, thus opening new routes that lead to novel unexpected structures. Box of surprises: Serendipitous discoveries have long‐since been at the heart of the new advancements in science, and more often than not they provide striking findings that exceed the most promising expectations; thus, serendipity emerges to extend the frontiers of chemistry one step further. Palladacycles have not been strangers to this issue and, herein, some distinguished disclosures are depicted where serendipity yielded remarkable, yet not sought, results. [ABSTRACT FROM AUTHOR]

Two new mononuclear iron(III) Schiff base complexes [Fe( L 1 ) 2 ]SCN (1) and [Fe( L 2 )( HL 3 )]ClO 4 (2) {where HL 1  = 1-((3-amino-2,2-dimethylpropylimino)methyl)naphthalen-2-ol, H 2 L 2  = N,N′-bis(3-ethoxysalicylidene)2,2-dimethyl-1,3-propanediamine and HL 3  = 2-((3-amino-2,2-dimethylpropylimino)methyl)-6-ethoxyphenol} have been synthesized and characterized by elemental and several spectral analyses. Single crystal X-ray structure determination confirmed their structures. Structural features have been examined in details that reveal the formation of interesting supramolecular networks generated through weak non-covalent interaction. Both complexes are able to show catechol oxidase mimicking activity and kinetics of the reactions are monitored spectrophotometrically. [ABSTRACT FROM AUTHOR]