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Graphical abstract Synthesis, structure and photophysical properties of Zn(II) Schiff base complexes on 3-methyl-1-phenyl-4-formylpyrazol-5-one basis possessing strong solvent-dependent solid-state fluorescence are described. Abstract The present article reports on the syntheses, crystal structures and luminescence properties of three solvate forms of a zinc(II) complex containing 4-{(E)-[(2-fluorophenyl)imino]methyl}-5-methyl-2-phenyl-2,4-dihydro-3 H -pyrazol-3-one (HL). The reaction of zinc(II)acetate with the HL ligand in ethanol and acetonitrile led to the formation of two solvate analogues [Zn(L) 2 ]·Solv (Solv – ethanol (1) and acetonitrile (2)). The properties of the [Zn(L) 2 ]·Solv complexes were investigated by UV–Vis absorption and fluorescence emission spectroscopy, and the density functional theory calculations. Bader's topological analysis was performed to investigate the electronic peculiarities of Zn(II) polyhedra and non-covalent interactions within crystal packing of studied solvates. [ABSTRACT FROM AUTHOR]

A novel multifunctional probe, L , based on triphenylamine o -hydroxyl Schiff base was constructed for the sequential detection of Zn 2+ /P 2 O 7 4− . Interestingly, probe L also showed two-photon fluorescent “off-on” response to Zn 2+ along with a large effective two-photon absorption cross-section value of 240 GM at 720 nm, a low cytotoxic and a moderate photostability, which made L a good candidate for two-photon fluorescence microscopy imaging and monitoring the fluctuation of exogenous Zn 2+ . [ABSTRACT FROM AUTHOR]

The photo- and electroluminescence properties of solution-processed organic light-emitting diodes (OLEDs) consisting of composites of PVK as a host with [Zn(salophen)] or [Zn(sal-3,4-ben)] as guests were studied. Devices consisted of a single spin-coated active layer. The electro-optical properties (voltage turn-on (V on ), brightness (L max ) and current efficiency (η curr )) of the coordination compounds were better than those of the ligands. This improvement can be explained by the increase of the hole mobility (μ p ) compared to the PVK and PVK:salicylidenes composites. The L max and η curr were three times higher for the PVK:[Zn(sal-3,4-ben)] (V on  = 6.5 V; L max  = 131 cd m −2 ; η curr  = 36 mcd A −1 ) diode than the PVK:[Zn(salophen)] (V on  = 9.5 V; L max  = 52 cd m −2 ; η curr  = 11 mcd A −1 ) due to the increase of the hole mobilities of μ p ([Zn(sal-3,4-ben)]) ∼ 10 2 xμ p ([Zn(salophen)]). Moreover, the PVK:[Zn(sal-3,4-ben)] diode presented L max and η curr comparable to the PVK:8-hydroxyquilinate compounds (Alq 3 and Znq 2 ) prepared using the same procedure which can be explained by the hole mobilities of these composites and photoluminescence quantum yields (PLQY) of the coordination compounds. [ABSTRACT FROM AUTHOR]

Three polar Ni(II)-, Cu(II)- and Zn(II)-complexes (M-SSA) of salicylidene anthranilate sodium salt ligand were synthesized. The ligand (H 2 SSA) and its corresponding metal-complexes are characterized by alternative physico-chemical tools in which H 2 SSA acts as tridentate bi-basic chelating agent. Catalytic potential of M-SSA was investigated in the homogenous oxidation of 1,2-cyclohexene at 80 °C in acetonitrile, water or under solvent-free condition. M-complexes exhibit high catalytic reactivity with high chemoselectivity in acetonitrile. Cu-SSA shows the highest catalytic potential for the oxidation of 1,2-cyclohexene than Ni-SSA or Zn-SSA. The lowest yield of the epoxy-product was obtained in water due to the hydrolysis ring opening reaction affording 1,2-cyclohexanediol. The inhibition performance of H 2 SSA and M-SSA on the carbon steel corrosion (CS) in HCl was studied using electrochemical techniques. The inhibition capability was increased with increasing inhibitor dose. The adsorption of inhibitors on the surface of CS obeyed the Langmuir isotherm paradigm. Surface characterizations (SEM/EDX) revealed that the investigated compounds adsorbed on CS surface and form protective layer that shield the surface from direct corrosion attack. The experimental data have been completed by density functional theory treatment. The obtained theoretical results are exceedingly in agreement with empirical results catalytically and inhibitory. [ABSTRACT FROM AUTHOR]

The reaction of o-lithiated O-aryl N,N-diethylcarbamates with (hetero)aromatic nitriles gives rise to functionalized salicylidene urea derivatives in high yields through a new 1,5-O → N carbamoyl migration. This Snieckus-Fries-type rearrangement nicely complements previously known O → C and O → O related shifts. In addition, when dimethylmalononitrile is used as the electrophilic partner, the carbamoyl shift is preferred over the expected transnitrilation reaction. [ABSTRACT FROM AUTHOR]

Salicyladehyde and 2-hydroxy-1-naphthaldehyde were used as ligands to prepare bis(salicylidene)zinc(II) and bis(2-hydroxy-1-naphthaldehydato)zinc(II) complexes. The bis(2-hydroxy-1-naphthaldehydato)zinc(II) complex was used as a precursor to synthesize zinc oxide nanoparticles via thermal decomposition technique at different temperatures using hexadecylamine (HDA) as a stabilizing agent. The results show that decomposition temperature has a huge effect during the formation of the ZnO nanomaterials. The TEM images of the as synthesized nanoparticles revealed different shapes of the particles as the decomposition temperature was increased from 145 to 190 °C. The diffraction patterns of all ZnO nanoparticles synthesized at various temperatures show hexagonal structures with the lattice parameter of a = b = 3.25 Å and c = 5.20 [ABSTRACT FROM AUTHOR]

Starting with a coordination polymer, {[Cu(L)]2}n (1 where H2L = salicylidene-2-aminophenol), we have explored the ability of polypyridyl ligands (P) to bridge the monomer complex to form nine {[Cu(L)]2(P)} complexes. The identity and solution stability of the [Cu(L)] units has been investigated through a novel combined UV-vis/EPR experiment and it has been found to be a stable supramolecular building unit for the construction of discrete complexes and coordination polymers. The reorganization of [Cu(L)] units to a new coordination polymer on addition of 4,4'-bipyridine markedly changes the connectivity of the structure and the magnitude of the antiferromagnetic interactions through reorientation of the Cu(II) orbitals. We also present the structure of 1, 80 years after its synthesis was first reported. [ABSTRACT FROM AUTHOR]

Three conformationally locked salicylideneaniline derivatives, 1a – 1c , were synthesized and characterized by single-crystal X-ray diffraction. Compound 1a possesses a triply locked configuration, i.e., the intramolecular five-membered-ring C–H⋅⋅⋅N and six-membered-ring O–H⋅⋅⋅N hydrogen bonds and five-membered-ring C(1-6-7-8-9) cyclization, from which the excited-state intramolecular proton transfer takes place, resulting in a record high tautomer emission quantum yield of 0.28 in the solid state. Compared with salicylideneaniline, a substantial increase in the emission quantum yield is also observed for 1b and 1c . Furthermore, compound 1a shows pH-dependent optical properties and a highly reversible response to pH, which makes it good candidate for potential applications in pH sensing. Time-dependent density functional theory calculations are reported on these salicylideneaniline derivatives in order to rationalize their electronic structure and optical properties. [ABSTRACT FROM AUTHOR]

We report the synthesis of a luminescent N-salicylidene aniline derivative, N-salicylidene-4-amino-2-methylbenzotriazole (1), and the study of its polymorphism and photophysical properties. Three phases showing yellow (1-Y), orange (1-O), and red (1-R) fluorescence have been isolated and characterized by thermal and single crystal X-ray analysis. The photoluminescence results from excited-state intramolecular proton transfer process and the quantum yield is strongly dependent on polymorphism (Φ1-Y = 0.87, Φ1-O = 0.11, Φ1-R = 0.028). The poorly emitting 1-R can be easily prepared, converted to the bright 1-Y by grinding, and reverted to 1-R through melting and annealing, giving rise to a luminescence on-off mechano-responsive cycle. The different photophysical properties are explained with the variable p-overlap and molecular conformation changes in the three polymorphs, characterized by a very similar crystal packing. By DFT calculations, the absorption properties were explained as dependent on the torsion angle between the two planar portions of the molecule, which affects the equilibrium between enol and keto forms in the ground state. [ABSTRACT FROM AUTHOR]

The use of N -salicylidene-4-methyl- o -aminophenol in nickel(II) pivalate chemistry has provided access to structurally and magnetically interesting {Ni II 6 Na I 4 } and {Ni II 6 } clusters possessing carbonato and methanediolato(-2) ligands, respectively, with novel coordination modes. [ABSTRACT FROM AUTHOR]

Through the single-nodal copolymerization of MMA (methyl methacrylate) and a vinyl-containing complex monomer [Zn(L)(4-vinyl-Py)Nd(NO 3 ) 3 ] ( 2 ; H 2 L = N , N ′-bis(3-methoxy-salicylidene)ethylene-1,2-diamine; 4-vinyl-Py = 4-vinyl-pyridine) with the both 1 π-π* and 3 π-π* sensitizing approach to Nd 3 + ion, the Zn 2 + -Nd 3 + -containing metallopolymer Poly(MMA- co -2) exhibits good physical properties including an attractive Nd 3 + -centered NIR sensitization efficiency ( Φ L Nd = 1.22% and η = Φ L Nd / Φ Nd Nd = 82%). [ABSTRACT FROM AUTHOR]

Porous materials such as covalent organic frameworks (COFs) are good candidates for molecular sieves due to the chemical diversity of their building blocks, which allows fine-tuning of their chemical and physical properties by design. Tailored synthesis of inherently functional building blocks can generate framework materials with chemoresponsivity, leading to controllable functionalities such as switchable sorption and separation. Herein, we demonstrate a chemoselective, salicylideneanilines- based COF (SA-COF), which undergoes solvent-triggered tautomeric switching. This is unique compared to solid-state salicylideneanilines' counterpart, which typically requires high energy input such as photo or thermal activation to trigger the enol-keto tautomerisim and cis-trans isomerization. Accompanying the tautomerization, the ionic properties of the COF can be tuned reversibly, thus forming the basis of size-exclusion, selective ionic binding or chemoseparation in SA-COF demonstrated in this work. [ABSTRACT FROM AUTHOR]

Herein, star-shaped tris(N-salicylideneaniline)s (TSANs) containing 1,3,4-oxadiazole based and 1,3,4-thiadiazole based arms are synthesized and characterized. The introduction of branched tails at their peripheries has different effects on these tris(N-salicylideneaniline)s, which are dependent on the type of heterocycle. The TSANs bearing 1,3,4-oxadiazole arms with branched tails exhibit a room temperature columnar rectangular phase in comparison to the high temperature columnar hexagonal phase exhibited by their hexadecyloxy chain analogues. In the case of the thiadiazole based TSANs, the compound with hexadecyloxy chains exhibits a columnar rectangular phase over a wide temperature range including room temperature, whereas its branched chain analogue is a liquid. Thus, in the case of star-shaped molecules, the type of peripheral tails not only affects the transition temperature, but also affects the type of self-assembly, which is in contrast to conventional discotic liquid crystals. The introduction of substituted 1,3,4-thiadiazole rings helps in the reduction of their melting points and enhances their mesophase width. The presence of bulky branched tails at their peripheries enhances the intermolecular interactions between the cores of the 1,3,4-oxadiazole based TSANs, which leads to the stabilization of the columnar rectangular phase. The 1,3,4-thiadiazole based TSANs exhibit a columnar rectangular phase even with straight peripheral chains because of the attractive intermolecular interactions of the thiadiazole ring. [ABSTRACT FROM AUTHOR]

N , N′ -bis(salicylidene)-2-(6-(2-aminophenyl)-4-phenylpyridin-2-yl) ( 3 ) was synthesized by condensation reaction of 2,6-bis(2-aminophenyl)-4-phenylpyridine and 2-hydroxybenzaldehyde in EtOH and characterized by its melting point, 1 H, 13 C NMR and molecular mass. The addition of Cr 3+ ion makes the significant increase of its fluorescent intensity at 537 nm in CH 3 CN/H 2 O (95/5%), however, other metal ions have almost no influence on the fluorescence. The reason for this phenomenon might be attributed to the formation of a 1:1 stoichiometric 3 -Cr 3+ complex which inhibits photo-induced electron transfer (PET) process. The 1:1 binding stoichiometry between 3 and Cr 3+ was established using Job’s plot, and the complex structure was proposed by DFT calculation. The association constant ( K a ) was determined to be 8.77 × 10 4 M −1 and the limit of detection (LOD) was calculated to be 2.2 × 10 −7 M. [ABSTRACT FROM AUTHOR]

It is observed that planar Ni(II)–Schiff base complexes of general formulae NiL with L as N, Ń-bis(4-hydroxy salicylidene)ethylenediamine (4-OH-salen) when encapsulated in the supercage of zeolite Y, the complex adopts non-planar geometry. The detailed characterization studies of the 4-OH-Ni-salen complex when compared with Ni-salen complex encapsulated in zeolite Y (Ni-salen-Y) Choudhary et al. (2016) have suggested that the complex undergoes more distortion in order to accommodate itself inside the supercage of zeolite-Y. Optical spectroscopic studies show relatively more blue shifted and intensified d-d transition for 4-OH-Ni-salen complex after encapsulation. We also report the catalytic activities and enhanced magnetization of encapsulated complex though it is diamagnetic in the ‘free’ state. DFT studies of these complexes have been carried out in different spin states and electronic spectra are simulated to have better insight about the geometries adopted by the guest complexes inside the host framework. [ABSTRACT FROM AUTHOR]

The role of different solvent environments in determining the behavior of molecules in solution is a fundamental aspect of chemical reactivity. We present an approach for exploring the influence of solvent properties on condensed-phase dynamics using ultrafast transient absorption spectroscopy in supercritical CO2. Using supercritical CO2 permits adjustment of the density, by varying the temperature and pressure, whereas varying the concentration or identity of a second solvent, the cosolvent, in a binary mixture allows for adjustments of the degree of interaction between the solute and the solvent. Salicylidene aniline, a prototypical excited-state intramolecular proton-transfer system, is the subject of this study. In this system, the decay rate of the transient absorption signal decreases as the fraction of the cosolvent (for both 1-propanol and cyclohexane) increases. The decay rate also decreases with an increase in the viscosity of the mixture, but the effect is much larger for the 1-propanol cosolvent than for cyclohexane. These observations illustrate that the decay rate of the photoexcited salicylidene aniline depends on more than just the solvent viscosity, suggesting that properties such as polarity also play a role in the dynamics. [ABSTRACT FROM AUTHOR]

The photophysical properties of two N -salicylidene p -X-anilines (X C N, COOH) were studied in a series of solvents with varying polarity and proticity by steady state absorption and emission spectroscopy. The two compounds are dually fluorescent in solution due to an excited state proton transfer. The solvatochromic shifts were used to connect the solvent polarity parameter to the dipole moment in excited state using several approaches. The multiparameter Kamlet–Taft and Catalán solvent scales with four parameters have been employed to analyze the specific and non-specific solvent–solute interactions. The absorption spectra are less sensitive to the substitution at the aniline ring and to the solvent properties than the fluorescence spectra. Especially the ratio between the normal and abnormal Stokes shifted fluorescence intensities is dependent on the polarity and hydrogen bonding abilities of the solvent. The increasing solvent viscosity led to a decrease in the ratio of the intensities of the two emissions. [ABSTRACT FROM AUTHOR]

The synthesis and photophysical properties of three tris( N-salicylideneaniline) (TSA) compounds containing 1,3,5-triarylbenzene, -tristyrylbenzene, and -tris(arylethynyl)benzene core units are reported. The TSA compounds underwent efficient excited-state intramolecular proton transfer (ESIPT) in solution and in solid state due to the preformed C= N ⋅⋅⋅H−O hydrogen-bonded motifs of the structures. Steady-state fluorescence emission spectra of the TSA molecules revealed dual bands only in DMSO, and large Stokes shifts in other polar aprotic and protic solvents. Femtosecond transient absorption spectroscopic measurements in THF revealed lifetime values in the range of 14-16 ps for the excited-state keto-tautomer. The TSA compounds are also responsive to metal ions (Cu2+ and Zn2+) in DMSO, exhibit enhanced aggregate-induced emission (AIE) properties in DMSO/water mixtures, and are highly luminescent in the solid state. [ABSTRACT FROM AUTHOR]

Here, we synthesized the salicylidene-aniline (anil) photochromes with thiol group (thiolated Schiff base) to modify silver nanoparticles (AgNPs) surface and their photochromic properties were described. A photochromic response related to the light induced tautomerization of the anils functionality along with bathochromic shift in the absorption band is observed in AgNPs surfaces. We have also examined that enol→keto photoisomerization rate by UV light for functionalized AgNPs are clearly faster than free anils. [ABSTRACT FROM AUTHOR]

Reversible changes induced by a polystyrene matrix on the photochemistry of two derivatives of N -salicylidene aniline were investigated by steady–state and time resolved spectroscopy. The photosensitivity of N -salicylidene- p -cyanoaniline (SA-CN) and N -salicylidene- p -carboxyaniline (SA-COOH) upon insertion in the matrix was tested by irradiation with UV light. The inactive photochromism of N -salicylidene- p -cyanoaniline has been activated via a conformational change from planar to a non-planar geometry, accompanied by fluorescence quenching. The geometry of SA-COOH molecules in polystyrene matrix remained as flat as in crystals, and its photochemistry was unchanged as well, the pure compound being both photochromic and fluorescent. With the help of flash photolysis and time-resolved fluorescence the transient species in the ns–ms timescale were identified. The transient absorption spectra revealed some differences in the short-lived species between the two compounds, suggesting a rich photochemistry for SA-COOH and transient species with much longer lifetime for SA-CN. [ABSTRACT FROM AUTHOR]

A sensitive and selective spectrofluorimetric method has been developed for the rapid determination of europium(III). This method is based on the formation of nonluminous complex between Eu(III) and a Schiff base reagent N, N′-bis (salicylidene)-1,2-phenylenediamine (PABD) and measuring the fluorescence quenching of Eu(III)-PABD complex at λ = 390/577 nm. The fluorescence intensity complex decreased linearly by increasing the Eu(III) concentration in the range of 1.0-13.0 μM. The optimum conditions for the complex formation were determined such as a pH .0 of borate buffer. The limits of detection (LOD) and quantification (LOQ) of Eu(III) were determined and found to be 0.217 and 0.653 μM, respectively. The maximum relative standard deviation of the method for an europium(III) standard of 6.0 μM was 2.07 % ( n = 6). The proposed procedures could be applied successfully for the determination of the investigated metal ion in some spiked water samples with a good precision and accuracy compared to official and reported methods as revealed by t- and F-tests. [ABSTRACT FROM AUTHOR]

New dual photoisomeric cobaloxime complexes composed of salicylidene-3-aminopyridine derivatives and a 2-cyanoethyl group as axial ligands were synthesized. Photoisomerization of the 2-cyanoethyl group in the crystalline state was performed to control the photochromic properties of the salicylidene-3-aminopyridine derivatives. The colors of the three cobaloxime crystals changed from pale yellow to orange or dark red when the crystals were irradiated with UV light. The red crystals returned to their original color when they were irradiated with visible light or kept in the dark. When the crystals were exposed to visible light before UV irradiation, the 2-cyanoethyl group bonded to the cobalt atom isomerized to the 1-cyanoethyl group with retention of the single crystal form. The crystals containing the 1-cyanoethyl group after photoirradiation also showed photochromism on exposure to UV light. However, the lifetime of the photochromic red species after 2–1 isomerization of the cyanoethyl group was significantly different from that before isomerization. The difference is well explained by the cavity volume around the central C–N bond of the salicylidene moiety in the crystal of the red species. [ABSTRACT FROM AUTHOR]

Luminescent discotic liquid crystals based on tris( N -salicylideneaniline)s [TSANs] bearing trans -stilbene fluorophores have been synthesized. Their mesomorphic and photophysical properties were studied. These TSANs existing in the form of C 3h and C s geometrical isomers of the keto-enamine tautomer self-assemble to form the columnar phase and exhibit fluorescence both in solution and mesophase states. These columnar mesophases also exhibit frozen (glassy) columnar phase, which ensures preserved fluorescence intensity, defect free alignment and simultaneous restriction on the motion of ionic impurities. These features make them promising candidates for the use in organic light emitting diodes, particularly as emissive layers. This study also led to an understanding about the dependence of their mesomorphism (mesophase type, stability and thermal range) and photophysical features on the number and pattern of their peripheral substitution, in comparison to the analogous columnar liquid crystalline TSANs reported earlier. [ABSTRACT FROM AUTHOR]

Rod-likestrontium tungstate nanostructures have been successfully prepared via the co-precipitation process by using Sr(Sal) 2 (Sal = salicylidene) and sodium tungstate dehydrate (Na 2 WO 4 ·2H 2 O) as starting materials. The as-prepared rod-like nanostructures were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, Energy Dispersive X-ray microanalysis (EDX), Photoluminescence (PL) spectroscopy, Transmission electron microscopy (TEM), and Scanning Electron Microscopy (SEM). The effect of parameters such as temperature, solvent and surfactant were considered to obtain the best condition. Moreover, adsorption of Rhodamine B (RhB) dye on strontium tungstate nanostructures was investigated and the uptake% was determined to be > 80% in 240 min. [ABSTRACT FROM AUTHOR]

A new computational protocol relying on the use of electrostatic embedding, derived from QM/QM' ONIOM calculations, to simulate the effect of the crystalline environment on the emission spectra of molecular crystals is here applied to the β-form of salicylidene aniline (SA). The first singlet excited states ( S1) of the SA cis-keto and trans-keto conformers, surrounded by a cluster of other molecules representing the crystalline structure, were optimized by using a QM/QM' ONIOM approach with and without electronic embedding. The model system consisting of the central salicylidene aniline molecule was treated at the DFT level by using either the B3LYP, PBE0, or the CAM-B3LYP functional, whereas the real system was treated at the HF level. The CAM-B3LYP/HF level of theory provides emission energies in good agreement with experiment with differences of −20/−32 nm ( cis-keto form) and −8/−14 nm ( trans-keto form), respectively, whereas notably larger differences are obtained using global hybrids. Though such differences on the optical properties arise from the density functional choice, the contribution of the electronic embedding is rather independent of the functional used. This plays in favor of a more general applicability of the present protocol to other crystalline molecular systems. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A selective fluorescent chemosensor was prepared by anchoring pyridine-2-carbaldehyde Schiff base ligand onto mesochannels of organically modified SBA-15 mesoporous silica. The resulting organic-inorganic hybrid mesoporous chemosensor was characterized by X-ray diffraction, Fourier transform IR spectroscopy, transmission electron microscopy, UV-visible diffuse reflectance spectra, and photoluminescence spectra. All the results support the idea that successive attachment of the ligand moiety onto one-pot-modified mesoporous scaffold has not altered its basic hexagonally arranged structure. Upon introducing trace amounts of zinc ions into aqueous solution, remarkable enhancement in the fluorescence was observed. [ABSTRACT FROM AUTHOR]

The solvent extraction of copper(II) from aqueous sulfate solutions was studied using salicylideneaniline and the three isomeric salicylidenetoluidine diluted with chloroform at 25°C. The molecules of these extractants are studied theoretically using ab initio methods at the HF/6–31G(d) level, with theirs parameters optimized to reproduce geometries of these compounds. By a statistical analysis of the extraction data, it was concluded that the extracted species are CuL2with CuL2(HL). This tendency is confirmed from numerical extraction constants for metal cations. The best extraction was according to the following order: HSOT ∼ HSMT ∼HSPT > HSA. [ABSTRACT FROM PUBLISHER]

A potential DNA intercalating Cu(II) complex ([CuL]) of the N,N′-disalicylidene-2,3-diaminopyridine ligand (H 2 L; dianion = L 2 − ) has been synthesized and characterized. The photophysical and the DNA binding behaviors of the neutral [CuL] have been investigated both experimentally and theoretically. Experimental studies reveal that the [CuL] has a quite strong interaction with the Calf Thymus DNA (ctDNA) with K b = (1.53 ± 0.48) × 10 6 . Experimental bathochromism of 4 nm and hypochromism of ∼50% on the absorption band of the [CuL] at 408 nm by intercalation were reproduced by calculations. The competitive displacement experiments were carried out using Methylene Blue (MB) and Ethidium Bromide (EB). Viscosity measurements totally supported the intercalative interaction. Quantum mechanical calculations using time dependent density functional theory (TDDFT) coupled with polarizable continuum model were carried out in the proposed dimer of deoxyguanosine-monophosphate-deoxycytidine, d(GpC) 2 , intercalation pocket. The calculations qualitatively confirmed the intercalative binding. In addition, vertical excitation calculations showed that electronic excitations of H 2 L are affected by the environment and Cu 2+ ion. The electronic transitions of the [CuL] are involved in mostly π – π ∗ transitions but includes significant contribution from the charge transfer. According to the calculations, the electronic spectrum of the [CuL] is sensitive to the DNA intercalation because of the π – π stacking interaction between the DNA base pairs and aromatic rings of the [CuL]. [ABSTRACT FROM AUTHOR]

In this study, several unsymmetrical Schiff bases and their cobalt and manganese complexes have been synthesized and characterized. The unsymmetrical Schiff bases were prepared from reaction of o-phenylendiamine derivatives with 1-hydroxy-2-acetonaphthone and then the product was reacted with the following aldehydes: salicyaldehyde, 2-hydroxynaphthaldehyde, 2-pyridinecarboxaldehyde and 2-qinolinecarboxaldehyde to produce the desired tetradentate unsymmetrical Schiff base ligands H2SL, H2NL, HPYL and HQN, respectively. Reaction of these ligands with cobalt and manganese salts produced complexes of the general formula [M(SL)], [(NL)], [M(PYL)] and [M(QL)]. All the complexes were characterized by elemental analysis, infrared spectroscopy, UV-visible spectroscopy, electrical conductivity and magnetic susceptibility measurements. The prepared complexes were examined for their anti-bacterial activity using gram-positive and gram-negative pathogens. The following complexes showed strong antibacterial activity againstStaphylococcus aureus: MnSL1, MnSL2 and MnSL3. The genotoxic activity of four complexes, which are MnNL1, MnSL1, CoNL1 and CoSL1, were examined using 8-hydroxy-2-deoxy guanosine (8-OHdG) assay in cultured human blood lymphocytes. All examined complexes were found to be genotoxic at examined concentrations (0.1–100 µg/mL), but with variable magnitudes (p < 0.05). The levels of 8-OHdG induced by MnNL1 and MnSL1 were significantly higher than that induced by CoNL1 and CoSL1 ones. In general, the order of mutagenicity of the compounds is MnSL1 > MnNL1 > CoSL1 > CoNL1. In conclusion, some of the prepared complexes showed some biological activities that might be of interest for future research. [ABSTRACT FROM PUBLISHER]

By applying nonequilibrium Green's functions in combination with the density-functional theory, we investigate the electron transport properties of the salicylideneaniline molecule sandwiched between two armchair graphene nanoribbon (AGNR) electrodes. It shows that the width of the AGNR electrodes plays a significant role in the transport properties of the salicylideneaniline molecular junctions. The current–voltage characteristics of the salicylideneaniline molecule sandwiched between 8AGNR electrodes can perform a stable conductance switching behavior at the bias region [1.2 V, 1.6 V] when the molecule translates between the trans -enol form and the trans -keto form. When the electrodes change to 7AGNR, a remarkable negative differential resistance behavior can be found in the salicylideneaniline molecular device at the trans -keto form. That means the salicylideneaniline molecule can perform different functions when it connects to the different AGNR electrodes. [ABSTRACT FROM AUTHOR]

The syntheses, structures, and magnetic properties of four new complex salts, (PPN){[MnIII(salphen)(MeOH)]2[MIII(CN)6]}.7MeOH (Mn2M.7MeOH) (M = Fe, Ru, Os and Co; PPN+ = bis(triphenylphosphoranylidene)ammonium cation; H2salphen = N,N'-bis(salicylidene)-1,2-diaminobenzene), and a mixed metal Co/Os analogue (PPN){[MnIII(salphen)(MeOH)]2[CoIII0.92OsIII0.08(CN)6]}.7MeOH were undertaken. It was found that all compounds exhibit switchable single-molecule magnet (SMM) and exchange-bias behavior depending on the interstitial methanol content. The pristine (PPN){[Mn(salphen)(MeOH)]2[Os(CN)6]}.7MeOH (Mn2Os.7MeOH) behaves as an SMM with an effective barrier for the magnetization reversal, (Ueff/kB), of 17.1 K. Upon desolvation, Mn2Os exhibits an increase of Ueff/kB to 42.0 K and an opening of the hysteresis loop observable at 1.8 K. Mn2Os.7MeOH shows also exchange-bias behavior with magnetic hysteresis loops exhibiting a shift in the quantum tunneling to 0.25 T from zero-field. The FeIII and RuIII analogues were prepared as reference compounds for assessing the effect of the 5d versus 4d and 3d metal ions on the SMM properties. These compounds are also SMMs and exhibit similar effects but with lower energy barriers. These findings underscore the importance of introducing heavy transition elements into SMMs to improve their slow relaxation of the magnetization properties. The (PPN){[MnIII(salphen)(MeOH)]6[CoIII(CN)6]}.7MeOH (Mn2Co.7MeOH) analogue with a diamagnetic CoIII central atom and the mixed Co/Os (PPN){[MnIII(salphen)(MeOH)]2[CoIII0.92OsIII0.08(CN)6]}.7MeOH (Mn6Co/Os.7MeOH) "magnetically diluted" system with a 9:1 Co/Os metal ratio were prepared in order tofurther probe the nature of the energy barrier increase upon desolvation of Mn2Os. In addition, inelastic neutron scattering and frequency-domain Fourier-transform THz electron paramagnetic resonance spectra obtained on Mn2Os.7MeOH and Mn2Os in combination with the magnetic data revealed the presence of anisotropic exchange interactions between MnIII and OsIII ions. [ABSTRACT FROM AUTHOR]

Gas diffusion electrodes (GDEs) modified with N,Nʹ-Bis(salicylidene)-ethylenediamine-cobalt(II) (Cosalen) and conductive carbon black (BP) have been prepared. It is demonstrated that modified BP-Cosalen/GDE electrode is able to catalyze CO reduction in a more efficient and selective manner than that of bulk Cosalen/GDE in 0.5 M KHCO solution. In the presence of 60 wt% of BP, the as-prepared BP-Cosalen/GDE electrode exhibits the highest activity for catalyzing CO reduction reaction, wherever increase or decrease the amount of BP do not benefit to CO reduction. Compared to other BP-Cosalen/GDE electrodes, the BP-Cosalen/GDE60 shows the most positive onset potential, and the maximum current density reaches 21 mA cm. The improved catalytic activity is largely due to the excellent electrical conductivity and the developed pore structure of BP which provides more active phases for the electrochemical reduction of CO. Further analysis of reduction product reveals that the product on BP-Cosalen/GDE60 electrode is formate in 0.5 M KHCO electrolyte. The highest faradaic efficiency reached 27 % along with the production rate of formate as much as 0.44 mM. [ABSTRACT FROM AUTHOR]

Modified electrodes based on films of Schiff base complexes are excellent candidates for sensing applications. The influence of the electrode material, glassy carbon, platinum, gold or indium tin oxide, on the electrodeposition of nickel- N,N’ – bis (salicylidene)-1,3-propanediamine (Ni- Salpn ) films in 1,2-dichloroethane (DCE) was investigated, and their electrochemical behaviour was evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The effect of the electrodeposition potential and electrodeposition time on the electrochemical behaviour of Ni- Salpn was examined using glassy carbon as substrate. The film growth process was investigated using the electrochemical quartz crystal microbalance and UV-vis absorption spectroscopy and structural differences between the Ni- Salpn complex and the Ni- Salpn film were examined by micro-Raman spectroscopy. The results demonstrate that the electrodeposition mechanism is independent of the electrode material, but that the nature of the substrate material influences the rate of film growth, the electrochemical behaviour and the stability of the film-modified electrodes in aqueous solution. Counteranion insertion during oxidation can break the bonds between the complexes in the stacked Ni- Salpn film structure and cause both mass loss and blockage of the redox metal centre activity, but these effects are small in thin films. [ABSTRACT FROM AUTHOR]

A new chiral amphiphilic salicylideneaniline bearing a terminal pyridine was synthesized. It formed reverse vesicles in toluene. The addition of Ag+, however, reversibly transforms these reverse vesicles into left-handed nanohelices accompanied by spontaneous gel formation at room temperature. [ABSTRACT FROM AUTHOR]

Discovery of new polypharmacological antibacterial agents with multiple modes of actions can be an alternative to combination therapy and also a possibility to slow development of antibiotic resistance. In support to this hypothesis, we synthesized 16 compounds by combining the pharmacophores of Chlamydia trachomatis inhibitors and inhibitors of type III secretion (T3S) in gram-negative bacteria. In this study we have developed salicylidene acylhydrazide sulfonamides ( 11c & 11d ) as new antichlamydial agents that also inhibit T3S in Yersinia pseudotuberculosis . [ABSTRACT FROM AUTHOR]

Infrared matrix isolation spectroscopy and DFT/B3LYP/6-311++G(d,p) calculations have been used to characterize the conformational space of the enol-imine and keto-amine tautomers of N-salicylidene-p-carboxyaniline (SCA) in both their E and Z isomeric forms. Monomers of SCA were isolated in an argon matrix (15 K), which was shown to contain only the most stable conformer of the E-enol isomer of the compound. The matrix-isolated E-enol was then subjected to in situ UV irradiation (? = 335; 345 nm, provided by a laser/MOPO system, or ? < 235 nm, provided by a Hg(Xe) broad-band source), and the photoinduced processes probed by infrared spectroscopy. Two photoreaction channels were observed, with a branching ratio of ~1:1, corresponding to E-enol ? Z-enol isomerization and E-enol ? E-keto tautomerization. Both processes were found to be rather effective, with practically complete consumption of the reactant after broad-band irradiation by 1 min only. Identification among the photoproduced species of the Z-enol conformer that differs from the reactant only by E-to-Z isomerization suggests the initial photoproduction of this conformer, which subsequently decays into the lowest energy Z-enol conformer (also identified experimentally). The E-enol ? E-keto tautomerization requires an excited state intramolecular proton transfer and twisting about the exocyclic CC bond of the molecule. These processes most probably take place sequentially. However, in the present study the Z-keto isomer, which should act as intermediate in this sequence of processes, could not be detected, most probably due to its short lifetime under the used experimental conditions. On the contrary, the detailed structural and vibrational characterization of the photoproduced E-keto form was successfully achieved. [ABSTRACT FROM AUTHOR]

Development of a selective and sensitive sensor for Ba 2+ is currently of great importance because of the adverse effects of Ba 2+ on the human body. In this study, we developed an excellent fluorescence chemosensor for Ba 2+ based on 3AP (N-salicylidene-3-aminopyridine). A fluorescence spectrophotometer is utilized to investigate the sensing properties of 3AP , and the results indicate that 3AP shows sensitive and selective detection of Ba 2+ through the enhancement of fluorescence intensity. The detection limit is determined to be 7.08×10 −7 mol/L. Background metal ions, such as Li + , Na + , K + , Cs + , Ca 2+ , Mg 2+ , Mn 2+ , Fe 3+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Pb 2+ , Cd 2+ , Al 3+ and Ag + , exhibit small or no interference with the detection of Ba 2+ . [ABSTRACT FROM AUTHOR]

N-Salicylidene p-aminobenzenesulfonate salts were prepared by in situ condensation of p-aminobenzenesulfonate diallylammonium salt and salicylaldehyde. Modulation of thermo- and photochromism was achieved by varying the alkyl chain length of the diallylammonium counter-cation. A structural-optical properties investigation reveals that both crystal packing and dihedral angle between aromatic rings of the N-salicylidene aniline switch are not sufficient to predict the occurrence of photochromism in the solid state. The available free space around the N-salicylidene p-aminobenzenesulfonate, in addition to the flexibility of the nearby environment, is shown to be of major importance for the cis→ trans isomerisation to occur as well as for the stabilisation of the trans-keto form. Emergence of photochromic properties was determined from the diallylhexylammonium cation within the series of investigated counter-cations. High stability is observed for the trans-keto form of one polymorph of N-salicylidene p-aminobenzenesulfonate diallylhexylammonium salt ( k=2.4×10−7 s−1). [ABSTRACT FROM AUTHOR]

Corrosion inhibition of mild steel in hydrochloric acid solution by salicylidene-4,4′-dimorpholine (SDM) and SDM assembled on nickel oxide nanoparticles (NiONPs) has been studied with gravimetric, electrochemical impedance spectroscopy (EIS) and polarization techniques. Inhibition was found to increase with increasing concentration of the inhibitors. While studying the temperature effect on corrosion behaviour of SDM and SDM assembled on NiONPs, the inhibition efficiency decreases for SDM only but increases for SDM assembled on NiONPs. The adsorption of both the inhibitors on the mild steel surface obeys the Langmuir adsorption isotherm. The activation energy as well as other thermodynamic parameters (Δ H * and Δ S *) for the inhibition process was calculated. EIS analysis results showed that the capacitive loops for SDM assembled on NiONPs were far away from blank when compared with SDM only. Polarization curve shows that the inhibitors are of mixed type. Further, the protective layer formation was confirmed from atomic force microscopy (AFM) results. Various methods such as EIS-MS, 1 H NMR, XRD, FTIR, and DLS were performed for the confirmation of the structure, interaction of SDM with NiONPs and size of NiONPs. [ABSTRACT FROM AUTHOR]

ABSTRACT Two phenoxo-bridged dinuclear copper(II) complexes (Cu2L12, Cu2L22) with N-salicylidene glycine Schiff bases were prepared and evaluated their performance for catalyzing the hydrolysis of p-nitrophenyl picolinate (PNPP). The observations reveal that the as-prepared dinuclear copper(II) complexes exhibited better activity by two to three orders of magnitude rate enhancement in comparison with the autohydrolysis rate of PNPP. Chloro-containing Cu2L22 aroused approximately three times kinetic advantage over chloro-free Cu2L12 at pH 7.0, which is probably contributed to the electron-withdrawing inductive effect of the 5′-chloride group. Moreover, it was found that the pH-responded kinetic behavior displayed an enzyme-like property for the PNPP hydrolysis by the two complexes. [ABSTRACT FROM AUTHOR]

Reactions of aluminium isopropoxide with 2-(o-hydroxyphenyl)-benzoxazole (pbox H) and salicylidene-4-chloroaniline (spca H) in different molar ratios in benzene solution afforded the complexes of the types [(μ-OPri)2Al2(pbox)2(OPri)2] 1, [Al(OPri)(pbox)2] 2, [Al(pbox)3] 3, [(μ-OPri)2Al2(spca)2(OPri)2] 4, [Al(OPri)(spca)2] 5 and [Al(spca)3] 6. All these colored solid complexes are soluble in common organic solvents and were characterized by elemental (C, H, N and Al) analysis, spectroscopic [IR (1H, 13C and 27Al) NMR] and mass spectrometric studies. On the basis of these studies, plausible structures have been tentatively proposed for these complexes. [ABSTRACT FROM AUTHOR]

The Sal-AHA chelates, which include a salicylidene moiety and an α-hydroxy acid moiety, have been shown to form trinuclear [Fe 3 (Sal-AHA) 3 (μ 3 -OR)] − clusters with Fe(III) that are photochemically active. Several minor modifications have been made to the chelate structure to evaluate the effects of different aspects of the chelate design on both the structure and the photochemistry of their Fe(III) complexes. Small steric changes have little effect on either overall structure or photochemistry. Shifting the position of the hydroxy group (α vs. β to the carboxylate), which bridges the irons in the cluster, also does not disrupt the trinuclear structure. However, shortening the length of the carbon chain between the salicylidene and the carboxylate results in loss of the trinuclear structure, forming FeL 2 complexes instead. Factors that are important to the quantum yield in the photochemical reaction include both the position of the hydroxy group with respect to the carboxylate and the number of Fe(III) ions in the complex. [ABSTRACT FROM AUTHOR]

Two trinuclear centrosymmetric hetero-metallic copper(II)–mercury(II) complexes of general formula [(CuL) 2 HgX 2 ] (where X = N 3 − for 1 and 1 ′ or OCN − for 2 and 2 ′) have been synthesized using [CuL] as ‘‘ligand complex” (where H 2 L = N,N′-bis(salicylidene)-1,4-butanediamine) and structurally characterized. Rapid crystallization of both the complexes yielded isomorphous crystals with two independent half molecules ( Z ′ = 1) in 1 and 2 but the crystals that were grown slowly from the same solutions are not isomorphous and contain single half molecule ( 1 ′ and 2 ′) in the asymmetric units ( Z ′ = 0.5). Crystal structure analyses reveal that the complexes have discrete trinuclear entity in which two square planar [CuL] units are bonded to a mercury ion through double phenoxido bridges. The Hg(II) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually trans nitrogen atoms of terminal azide (for 1 and 1 ′) and cyanate (for 2 and 2 ′). Higher Z ′ compounds are stabilized probably due to weak interactions (C–H⋯N/O and C/H⋯π interactions) that help to hold two independent molecules together. [ABSTRACT FROM AUTHOR]

Photoswitchingof simple photochromic molecules attracts substantialattention because of its possible role in future photon-driven molecularelectronics. Here we model the full photoswitching cycle of a minimalphotochromic Schiff base–salicylidene methylamine (SMA). Weperform semiempirical nonadiabatic on-the-fly photodynamics simulationsat the OM2/MRCI level and thoroughly analyze the structural time evolutionand switching efficiency of the system. We also identify and examinein detail the crucial steps in the SMA photochemistry ruled by excited-stateintramolecular proton transfer. The results place the investigatedmodel aromatic Schiff base among the promising candidates for novelphotoswitching molecular materials. Our study also shows the potentialof the semiempirical multireference photodynamics simulations as atool for early stage molecular photodevice design. [ABSTRACT FROM AUTHOR]

In this work, transition metal (M = Cu(II), Mn(II), Co(II), Ni(II)) complexes of tetradentate Schiff base ligand HL: (CHNO) have been introduced to cavity of zeolite-Y by flexible ligand method. These host-guest materials were characterized by several techniques: chemical analysis, diffuse reflectance spectroscopy, Fourier transfer infrared, X-ray diffraction, thermo gravimetric analysis and Burner-Emmet-Taller. The catalytic activity of [M(L)]/NaY (M = Mn, Co, Ni, Cu) was investigated with oxidation of phenol to catechol and hydroquinone with hydrogen peroxide (HO) as oxidant in different solvents. The reactivity of these heterogeneous catalysts was compared with corresponding homogeneous catalysts. The activity of phenol oxidation decreases in the series [Cu(L)]/NaY > [Mn(L)]/NaY > [Co(L)]/NaY > [Ni(L)]/NaY at mild conditions. We considered the effect of different factors on percent of products in oxidation of phenol such as: amount of catalyst, temperature, type of oxidant and solvent. Finally, the kinetic of phenol oxidation with excess HO over [M(L)]/NaY catalysts at several temperatures of 40, 60 and 80 °C was studied. These catalysts were very stable and can be reused for more than three times. Results show that a pseudo-first order with respect to phenol and the catalytic reaction occurred via a radical mechanism. [ABSTRACT FROM AUTHOR]

Acetylenic monomers containing salicylidene Schiff-base groups ( 1a and 1b ) as well as Schiff-base and hydroxy groups ( 1c ) were synthesized and polymerized with [(nbd)RhCl] 2 /Et 3 N catalyst to afford the corresponding polymers 2a – c with high molecular weights ( M n = 2.6–7.2 × 10 5 ) in high yields (75–97%). Polarimetric, circular dichroism (CD), and UV–vis spectroscopic analyses indicated that the polymers formed helical structures with a predominantly one-handed screw sense. The addition of metal ions to salicylidene Schiff-base-containing polymers 2a and 2b produced insoluble polymer/metal complexes through ionic cross-linking as a result of salicylaldimine–metal ion complexation. Polymers 2b and 2c underwent a helix–coil transition upon the addition of HSO 4 − , whereas these polymers did not exhibit responsiveness to other anions, such as F − , Cl − , and Br − . [ABSTRACT FROM AUTHOR]

The reactions of N -(2-carboxyphenyl)salicylideneimine and hydrated praseodymium(III) or neodymium(III) chlorides give 1D complexes with interesting structural and spectroscopic features; the chains possess the singly deprotonated ligand which is in its zwitterionic form. [ABSTRACT FROM AUTHOR]

The aim of the paper was to compare the electrochemical behavior and electroanalytical performance of tubular potentiometric solid-state sensors and screen-printed sensors based on ionic associates of dodecyl sulfate anions with alkylpiridinium cations or cationic complexes copper (II) and N,N’- bis (salicylidene)ethylene diamine (Salen) in sodium alkylsulfates solutions and different objects. [ABSTRACT FROM AUTHOR]