A colorimetric and turn-on fluorescent sensor for cyanide and acetate-based Schiff base compound of 2,2'-((1E,11E)-5,8-dioxa-2,11-diazadodeca-1,11-diene-1,12-diyl)bis(4-((E)-phenyldiazenyl)phenol).

A novel Schiff base-based sensor (L) has been designed, synthesized, and developed as a fluorescent and colorimetric sensor for cyanide and acetate. This L exhibited a quick response with rapid sensitivity to CN- and AcO- through a remarkable color change from yellow to red which was detectable by the naked eyes. It also sensed CN- and AcO- in a fluorescent way via an enhancement in fluorescence intensity. The interaction between L and anions (CN- and AcO-) was investigated by using UV-Vis studies, and 1H NMR titration. The theoretical DFT calculations were also employed to support the results, which displayed good agreement with the experimental value acquisition. As the detection limit for cyanide and acetate were 2.1 × 10-9 M and 1.7 × 10-9 M; respectively, low concentrations of these anions could be detectable in the proposed L sensor. In addition, L showed significant reversibility of CN- detection by using Cu2+ as a proper reagent with two different sensing methods including color change and UV-Vis. Last but not least, L could be applied to rapidly detect CN- in a wide range of pH. As a result, the proposed sensor is promising to identify cyanide and acetate in practical applications in medical, biological, and chemical fields.

Thermoresponsive and antibacterial two-dimensional polyglycerol-interlocked-polynipam for targeted drug delivery.

Two-dimensional polymeric networks are a new class of polymers with interesting physicochemical and biological properties. They promise a wide range of future biomedical applications including pathogen interactions, drug delivery, bioimaging, photothermal, and photodynamic therapy, owing to their unique features, such as high surface area and multivalent interactions at nano-biointerfaces. In this work, a thermosensitive two-dimensional polymeric network consisting poly(N-isopropylacrylamide) (pNIPAM) chains that are mechanically interlocked by a polyglycerol platform was synthesized and used for bacteria incapacitation. Two-dimensional hyperbranched polyglycerol (2D-hPG) was synthesized by a graphene-assisted strategy and used for encapsulation of azobisisobutyronitrile (AIBN). Radical polymerization of N-isopropylacrylamide by encapsulated AIBN resulted in thermoresponsive platforms with ~ 500 nm lateral size and 20-50 nm thickness. Due to its porous structure, 2D-PNPG was able to efficiently load antibiotics, such as tetracycline (TC) and amoxicillin (AMX). The rate of release of antibiotics from 2D-PNPG and the antibacterial activity of the system correlated with the variation of temperature as a result of the thermosensitivity of 2D-PNPG. This study shows that two-dimensional polymers are efficient platforms for future biomedical applications including drug delivery and bacteria incapacitation. Graphical abstract: Thermoresponsive two-dimensional nanomaterials with the ability of loading therapeutic agents and antibacterial activity are synthesized and characterized.

Design and synthesis of curcumin nanostructures: Evaluation of solubility, stability, antibacterial and antioxidant activities.

By coupling a quaternary pyridinium compound and curcumin (CM), a new antimicrobial agent called CP was obtained. The poor water-solubility was the most important limiting factor in the use of CM and CP. To address this problem, a hydrophilic hyperbranched polyglycerol (PG) was synthesized and reacted with CM and CP via Schiff base reaction to form two new macromolecules. Due to the presence of polymer, the solubility and stability of CM and CP increased significantly in aqueous media. Since the new macromolecules were including the hydrophilic polymeric and curcumin hydrophobic units, they self-assembled into spherical nanostructures, which were characterized by Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images. The synthetic nanostructures exhibited a controlled release of curcumin unit in the acidic environment. In vitro experiments showed that the new macromolecules are potent antibacterial and antioxidant agents.

Co-delivery of doxorubicin and curcumin by a pH-sensitive, injectable, and in situ hydrogel composed of chitosan, graphene, and cellulose nanowhisker.

Hydrogels are promising carriers for the controlled drug delivery in response to the external stimuli such as pH and temperature. Here, a new hydrogel is designed and synthesized from the cross-linking of graphene, chitosan, and cellulose nanowhisker via Schiff base reaction by a synthetic dialdehyde. The hydrogel presented a flexible structure and responded to altering pH and adding the external stimuli such as benzaldehyde and amino acid cysteine. The synthesized hydrogel was stable under physiological conditions. In vivo test showed that the hydrogel is subcutaneously injectable. Three drug-loaded hydrogels were synthesized, and in vitro drug release study showed a pH-dependent release of drugs in PBS solution.

A review on biological activities of Schiff base, hydrazone, and oxime derivatives of curcumin.

Curcumin (1,7-bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione) is the main pigment present in the turmeric rhizome and shows various biological properties. The synthesis of different derivatives is an effective way to improve the medicinal and biological properties of curcumin. Many researchers have chosen the carbonyl group of curcumin for modification and preparation of new analogues. This review critically surveys a general overview of the literature and summarizes the synthesis and biological activities of Schiff base, hydrazone and oxime derivatives of curcumin over the last decade. These compounds and also their metal complexes possess higher potency in biological activity.

Modification of chitosan and chitosan nanoparticle by long chain pyridinium compounds: Synthesis, characterization, antibacterial, and antioxidant activities.

Chitosan is an antibacterial biopolymer and conjugation of it with other antimicrobial agents can be a valuable method to improve the potential application of the resultant materials in the various industries such as cosmetics, food and packaging materials. In this work, a series of quaternary pyridinium compounds were synthesized; then to achieve developed biological properties, they were attached to the chitosan and chitosan nanoparticles. The formation of chitosan derivatives was evinced by FT-IR, 1H and 13C NMR, UV-vis and EDX spectroscopy. The morphology of samples was detected by FE-SEM, TEM and AFM images. The QAC-chitosan hybrids were investigated for antibacterial activity against two Gram-positive and two Gram-negative bacteria, and they showed a significant effect on the Gram-positive bacteria. DPPH-radical scavenging assay shows mild improvement in antioxidant activity of new chitosan derivatives.

Eco-friendly synthesis of graphene-chitosan composite hydrogel as efficient adsorbent for Congo red.

A simple approach was utilized to synthesize graphene/chitosan-based hydrogel using glutaraldehyde as crosslinking agent in room temperature. The composite aerogel was used for removal of cationic and anionic dyes from aqueous solution. It showed high adsorption capacity towards Congo red as an anionic dye. Adsorption experiments were performed based on various parameters, such as initial Congo red concentration, solution pH and contact time. The kinetics data were analyzed using four different models and the pseudo-second-order model best described the adsorption of Congo red aerogel. The Equilibrium adsorption isotherm data indicated that equilibrium data were fitted to the Langmuir isotherm. The maximum dye adsorption capacity calculated from the Langmuir isotherm equation was 384.62 mg g-1. Moreover, the aerogel was stable and easily recovered, and adsorption capacity was about 100% of the initial saturation adsorption capacity after being used three times.

Synthesis and carbonic anhydrase I, II, VII, and IX inhibition studies with a series of benzo[d]thiazole-5- and 6-sulfonamides.

A series of benzo[d]thiazole-5- and 6-sulfonamides has been synthesized and investigated for the inhibition of several human (h) carbonic anhydrase (CA, EC 4.2.1.1) isoforms, using ethoxzolamide (EZA) as lead molecule. 2-Amino-substituted, 2-acylamino- and halogenated (bromo-and iodo-derivatives at the heterocyclic ring) compounds led to several interesting inhibitors against the cytosolic hCA I, II and VII, as well as the transmembrane, tumor-associated hCA IX isoforms. Several subnanomolar/low nanomolar, isoform-selective sulfonamide inhibitors targeting hCA II, VII and IX were detected. The sharp structure-activity relationship for CA inhibition with this small series of derivatives, with important changes of activity observed even after minor changes in the scaffold or at the 2-amino moiety, make this class of scarcely investigated sulfonamides of particular interest for further investigations.

Synthesis, structural characterization, antimicrobial activities and theoretical investigations of some 4-(4-aminophenylsulfonyl) phenylimino) methyl)-4-(aryldiazenyl) phenol.

The azo-azomethine dyes with a different substitution have been designed from the reaction of 4,4'-diaminodiphenyl sulfone with 2-hydroxy-5-(aryldiazenyl)benzaldehyde. The compounds have been characterized by elemental analysis, Mass, IR, UV-Vis, TGA-DTA and NMR spectroscopy. The solvatochromism behaviors, effects of substitution and pH on the electronic absorption spectra of dyes were evaluated. The in vitro antimicrobial activities were also screened for their potential for antibiotic activities by broth micro dilution method. Also, the optimum molecular geometries, molecular electrostatic potential (MEP), nucleus-independent chemical shift (NICS) and frontier molecular orbitals (FMO), vibrational spectra (IR ) and electronic absorption (UV-Vis) spectra of the title compounds have been investigated with the help of DFT and TDDFT methods with 6-311++G(d,p) basis sets and PCM calculations. The results of the calculations show excellent agreement with the experimental value.

Interplay between H⋯O, H⋯X, X⋯O and X⋯X interactions in the complex pairing of formyl halides with hypohalous acids.

Ab initio study of the complexes formed by hypohalous acids (HOX, X=F, Cl, Br and I) with formyl halides (HCOY, Y=F, Cl, Br and I) has been carried out at the MP2/aug-cc-pVDZ computational level. These molecules can do a vast kind of H⋯O, H⋯X, X⋯O and X⋯Y interactions. The nature of the halogen atom in HOX is more important than HCOY in the X⋯Y interactions. Red shift of H-O bonds and blue shift of C-H bonds were observed frequently which are in line with the elongation (weakening) and contraction (strengthening) of related bonds, respectively. The interactions were analyzed with atoms in molecules (AIM) and natural bond orbital (NBO) theories. Results are showing good correlations between structural properties and AIM parameters.

The triazine-based azo-azomethine dyes; synthesis, characterization, spectroscopy, solvatochromism and biological properties of 2,2'-(((6-methoxy-1,3,5-triazine-2,4-diyl)bis(sulfanediyl)bis(2,1-phenylene))bis(azanylylidene)bis(methanylylidene))bis(4-(phenyldiazenyl)phenol).

The macrocyclic azo-azomethine dyes 2,2'-(((6-methoxy-1,3,5-triazine-2,4-diyl)bis(sulfanediyl)bis(2,1-phenylene))bis(azanylylidene)bis(methanylylidene))bis(4-(phenyldiazenyl)phenol) and its derivatives were synthesized and characterized by elemental analysis, mass, FT-IR, UV-vis and NMR spectroscopy. The solvatochromism as well as effects of substitutions on the electronic absorption of these compounds have been studied in the DMSO, DMF, THF, CH3CN, CH3OH and CH3COOH as solvents. Also they positive solvatochromism behaviors are explained on the basis of intramolecular hydrogen bonding, enol-keto tautomeric and dipole moment changes. Compounds having electron donating substituent on the phenyl ring showed good antioxidant activity. However, none of them has a considerable antibacterial activity.

Synthesis, characterization, solvatochromism and biological properties of 2,2'-((1E,1'E)-((1,2,5-oxadiazole-3,4-diyl)bis (azanylylidene))bis(methan-ylylidene))bis(4-(phenyldiazenyl)phenol).

Azo-azomethine dyes 2-((4-amino-1,2,5-oxadiazol-3-ylimino)methyl)-4-(phenyl diazenyl)phenols (2a-h) have been synthesized by condensation reaction of 3,4-diamino-1,2,5-oxadiazole with 2-hydroxy-5-[(E)-(aryldiazenyl)]benzaldehyde (1a-h) in methanol. The structures of dyes have been characterized by elemental analysis, mass, IR, UV-Vis, 1H and 13С NMR spectroscopy. UV-Vis absorption spectra indicated enol-keto tautomeric and positive solvatochromism in compounds 2a-h which is dependent on the substitution, solvent, pH and environment temperature. The synthesized compounds were investigated for their in vitro antioxidant activity by diphenylpicrylhydrazyl assay. Compounds substituted with electron donating groups, such as, alkyl and methoxy groups showed moderate antioxidant activity. The in vitro antibacterial activity of all compounds was determined by disk diffusion method. The test compounds showed varying degree of inhibition against B. cereus and S. aureus strains.

Spectroscopy and solvatochromism studies along with antioxidant and antibacterial activities investigation of azo-azomethine compounds 2-(2-hydroxyphenylimino)methyl)-4-phenyldiazenyl)phenol.

The azo-azomethine compounds 2-(2-hydroxyphenylimino)methyl)-4-phenyldiazenyl)phenol (2a-d) were prepared from the reaction of 2-aminophenol with 2-hydroxy-5-(aryldiazenyl)benzaldehyde (1a-d). The structures of all compounds were then characterized by elemental analysis, mass, infrared, UV-vis, (1)H and (13)C NMR spectroscopy. The electronic absorption spectra indicated enol-keto tautomeric and positive solvatochromism in compounds (2a-d), which is dependent on the substitution, nature of solvent, pH and environment temperature. The compounds (2a-d) were also evaluated for antibiotic activities by disc diffusion method. Compounds 2a and 2b exhibited antibacterial activities against Staphylococcus aureus and Bacillus cereus, but 2c and 2d were found to have no remarkable antibacterial activity. All the compounds (2a-d) also showed antioxidant activity as determined by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) method.

A polyglycerol-polycaprolactone-polycitric acid copolymer and its self-assembly to produce medium-responsive nanoparticles.

A hyperbranched-linear-hyperbranched amphiphile (HLHA) consisting of polyglycerol, polycaprolactone and polycitric acid blocks was synthesized and characterized. The self-assembly of HLHA in aqueous solutions produced nearly monodispersed nanoparticles. The average size of the nanoparticles in aqueous solutions was 120 nm. Spectroscopy and microscopy analysis showed that the nanoparticles change their structure in response to changes in the polarity of the medium in the solution state, so that the hydrophobicity or hydrophilicity of the solvent dominates the structure and properties of the nanoparticles. This property was used to load hydrophobic anticancer drugs inside the nanoparticles and also to deliver them to cancer cells successfully. In addition to the mentioned properties, the efficient uptake and low toxicity enable the prepared nanoparticles to be potential new systems for future cancer therapy.

Spectroscopic and solvatochromism studies along with antioxidant and antibacterial activities investigation of 2-((2-mercaptophenylimino)methyl)-4-(phenyldiazenyl)phenol.

The condensation reaction of 2-hydroxy-5-(aryldiazenyl)benzaldehyde (1a-d) with 2-aminothiophenole affored Schiff base compounds 2-((2-mercaptophenylimino)methyl-4-(-aryldiazenyl)phenol (2a-d). The structures of compounds (2a-d) were characterized by elemental analysis, mass, infrared, UV-vis and NMR spectroscopy. The 2a-d shows enol-keto tautomeric and positive solvatochromism. The antibacterial activities of 2a-d were also evaluated by disc diffusion method. Compound 2b displayed activity against Staphylococcus aureus and Bacillus cereus, 2a and 2c were active against B. cereus but 2d did not exhibit activity against the tested organisms. Among the tested compounds, 2b showed the best antioxidant properties as evaluated by free radical scavenging activity on 1,1-diphenyl-2-picryl-hydrazyl and ferric reducing power determination.

Synthesis and characterization of an azo dibenzoic acid Schiff base and its Ni(II), Pb(II), Zn(II) and Cd(II) complexes.

The new Schiff base 4,4'-(1E,1'E)-(3,3'-(1E,1'E)-(pyridine-2,6-diylbis(azan-1-yl-1-ylid ene))bis(methan-1-yl-1-ylidene)bis(4-hydroxy-3,1-phenylene))bis(diazene-2,1-diyl)dibenzoic acid (1) was prepared from the condensation reaction of 2,6-diaminopyridine with 4-((3-formyl-4-hydroxyphenyl)diazenyl)benzoic acid in methanol. The compound 1 is potentially an N, O multidentate chelating ligand which could form stable complexes with metal ions in 1:1 up to 1:3mol ratio of metal to ligand. The 1:1 complexes of Schiff base 1 with Ni(II), Pb(II), Zn(II) and Cd(II) have been synthesized by its condensation reaction with appropriate salts of metal ions. Structures of Schiff base (1) as well as its complexes with abovementioned metal ions were characterized by elemental analysis, mass, IR, UV-vis., (1)H and (13)С NMR spectroscopy.

Selective dispersive liquid-liquid microextraction and preconcentration of Ni(II) into a micro droplet followed by ETAAS determination using a yellow Schiff's base bisazanyl derivative.

A simple, rapid and sensitive method was developed for the selective separation and preconcentration of Ni(II) using dispersive liquid-liquid microextraction, by a yellow Schiff's base bisazanyl derivative, as a selective complexing agent. In this method, a mixture of 45 µL chloroform (extraction solvent) and 450 µL tetrahydrofuran (dispersive solvent) is rapidly injected by syringe into a 5 mL aqueous sample containing 3% (w/v) sodium chloride and an appropriate amount of the Schiff's base. As a result, a cloudy solution is formed by entire dispersion of the extraction solvent into the aqueous phase. After centrifuging for 5 min at 5000 rpm, the sedimented phase is directly injected into the electrothermal atomic absorption spectrometry for Ni(II) determination. Some important parameters, such as kind and volume of extraction and dispersive solvents, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor for the presented method is 138. The calibration curve was linear over a nickel concentration range of 10-50 ng mL(-1). The detection limit and relative standard deviation were 0.04 ng mL(-1) and 2.1%, respectively. The method was successfully applied to the extraction and determination of Ni(II) in different water samples.

Synthesis, characterization and electrochemical study of synthesis of a new Schiff base (H2cddi(t)butsalen) ligand and their two asymmetric Schiff base complexes of Ni(II) and Cu(II) with NN'OS coordination spheres.

A novel Schiff base (H(2)cddi(t)butsalen) ligand was prepared via condensation of Methyl-2-{N-(2'-aminoethane)}-amino-1-cyclopentenedithiocarboxylate(Hcden) and 3,5-di-tert-butyl-2-hydroxybenzaldehyde. The ligand and Ni(II) and Cu(II) complexes were characterized based on elemental analysis, IR, (1)H NMR, (13)C NMR, UV-Vis spectrometry and cyclic voltammetry. The structure of copper{methyl-2-{N-[2-(3,5-di-tert-butyl-2-hydroxyphenyl)methylidynenitrilo]ethyl}amino-1-cyclopentedithiocarboxylate has been determined by X-ray crystallography. The X-ray results confirm that the geometry of the complex is slightly distorted square-planar structure. The copper(II) ion coordinates to two nitrogen atoms from the imine moiety of the ligand, a sulfur atom the methyl dithiocarboxylate moiety and phenolic oxygen atom.

Competition between hydrogen and dihydrogen bonding: interaction of B2H6 with CH3OH and CH(n)X(3-n)OH derivatives.

Ab initio calculations were used to analyze the interactions between a molecule of B(2)H(6) with CH(3)OH and CH(n)X(3-n)OH (X = F, Cl and n = 0,1,2) derivatives at the MP2/6-311++G(d,p) computational level. Interaction of B(2)H(6) with CH(3)OH occurs through its bridged protons to form a hydrogen bond cluster. On the other hand, CH(n)X(3-n)OH molecules interact with B(2)H(6) by a H(t)...H dihydrogen bond along with a weak H(b)...X interaction. The structures obtained have been analyzed with the atoms in molecules (AIMs) methodology. AIM calculations indicate van der Waal's interactions of X with H(b) of B(2)H(6). The stability of the clusters depends on the type and number of X derivatives.

N-(2-Thienylmethyl-ene)-2-(2-{[2-(2-thienylmethyl-eneamino)phen-yl]sulfan-yl}ethyl-sulfan-yl)aniline.

The asymmetric unit of the title compound, C(24)H(20)N(2)S(4), contains one half-mol-ecule: a crystallographic centre of inversion is located at the mid-point of the two central C atoms. The thio-phene ring is oriented at a dihedral angle of 60.64 (3)° with respect to the benzene ring. In the crystal structure, π-π contacts between thio-phene rings [centroid-centroid distance = 3.581 (1) Å] may stabilize the structure. A weak C-H⋯π inter-action is also present.