Experimental and Theoretical Exploration of ESIPT in a Systematically Constructed Series of Benzimidazole Based Schiff Base Probes: Application as Chemosensors.

Herein, we have utilized 2-(2-hydroxyphenyl)benzimidazole (HBI) to synthesize 3-(1H-benzoimidazol-2-yl)-2-hydroxy-5-methyl-benzaldehyde (HBIA) followed by three Schiff bases by using -ortho (H BIo), -meta (H BIdm) and -para (H BIp) substituted amino benzoic acids and studied their photophysical properties. We have successfully derived molecular structures of HBI, HBIA and H BIdm which reveals that in HBI and HBIA, the phenolic -OH is intramolecularly hydrogen bonded with sp N of benzimidazole group whereas in H BIdm, it is hydrogen bonded with imine C=N of Schiff base moiety, which is responsible for different solid state emission properties of the reported compounds. Extensive experimental and theoretical studies show that for all three Schiff bases, in solution due to activation of C=N isomerization, ESIPT operates through benzimidazole site and displays different emission from the solid state.

A Quinoxaline-Naphthaldehyde Conjugate for Colorimetric Determination of Copper Ion.

This work facilitates detection of bivalent copper ion by a simple Schiff base probe QNH based on a quinoxaline-naphthaldehyde framework. The detailed study in absorption spectroscopy and theoretical aspects and crystal study of the probe and probe-copper complex has been discussed. The detection limit of the probe in the presence of Cu is 0.

Turn on Fluorescence Sensing of Zn Based on Fused Isoindole-Imidazole Scaffold.

Optical chemosensors caused a revolution in the field of sensing due to their high specificity, sensitivity, and fast detection features. Imidazole derivatives have offered promising features in the literature as they bear suitable donor/acceptor groups for the selective analytes in the skeleton. In this work, an isoindole-imidazole containing a Schiff base chemosensor (1-{3-[(2-Diethylamino-ethylimino)-methyl]-2-hydroxy-5-methyl-phenyl}-2H-imidazo[5,1-a]isoindole-3,5-dione) was designed and synthesized.

Strategic Substitution of -OH/-NR (R=Et, Me) Imparts Colorimetric Switching between F and Hg by Salicyaldehyde/Benzaldehyde-Quinoxaline Conjugates.

We herein report two salicyaldehyde-quinoxaline (HQS and HQSN) conjugates and a benzaldehyde-quinoxaline (QBN) conjugate to fabricate selective chemosensors for F and Hg in the micromolar range. This work demonstrates how sensing outcomes are affected by modulating proton acidity by introducing an electron donating group, -NEt , in the probe backbone. Interestingly, the un-substituted probe HQS can selectively detect F , whereas HQSN and QBN are selective for Hg .

Slow Magnetic Relaxation in a Co Dy Trimer and a Co Dy Tetramer.

The combination of Co(III) and Dy(III) with a compartmental Schiff base ligand (H L=3-[(2-Hydroxy-3-methoxy-benzylidene)-amino]-propane-1,2-diol), presenting three different coordinating pockets, has allowed the synthesis of two novel Co(III)-Dy(III) complexes: [Co Dy(HL) ]NO  ⋅ 2CH CN (1), a rare example of trinuclear linear Co Dy complex (and the first with slow relaxation of magnetization in absence of a DC field) and [Co Dy (μ -OH) (HL) (OAc) ] ⋅ 4.6H O (2), the first tetranuclear Co Dy cluster with a rhomb-like structure where the Co(III) ions are connected along the short diagonal of the rhomb. 1 presents two different relaxation processes: a fast relaxation dominated by Quantum tunnelling (QT) and a slow relaxation with an energy barrier of 40 K.

Slow magnetic relaxation and water oxidation activity of dinuclear CoCo and unique triangular CoCoCo mixed-valence complexes.

Construction of efficient multifunctional materials is one of the greatest challenges of our time. We herein report the magnetic and catalytic characterization of dinuclear [CoIIICoII(HL1)2(EtOH)(H2O)]Cl·2H2O (1) and trinuclear [CoIIICoII2(HL2)2(L2)Cl2]·3H2O (2) mixed valence complexes. Relevant structural features of the complexes have been mentioned to correlate with their magnetic and catalytic properties.

Aggregation-Induced Emission-Based Sensing Platform for Selective Detection of Zn : Experimental and Theoretical Investigations.

Fluorescent chemosensors with aggregation induced emission enhancement (AIEE) emerge as promising tools in the field of sensing materials. Herein, we report the design, synthesis and applicability of a Schiff base chemosensor 1-(benzo[1,3]dioxol-4-ylmethylene-hydrazonomethyl)-naphthalen-2-ol (Hbdhn) of AIE characteristics that exhibits highly effective and selective response towards Zn . The sensing effect of Hbdhn was evaluated by means of absorption/emission spectra and corresponding underlying photophysical mechanisms were proposed based on extensive quantum-chemical (TD)DFT calculations.

A quinoxaline-diaminomaleonitrile conjugate system for colorimetric detection of Cu in 100% aqueous medium: observation of aldehyde to acid transformation.

In this work, we have strategically incorporated a quinoxaline derivative and a diaminomaleonitrile moiety to construct a chemosensor, 2-amino-3-[(quinoxalin-2-ylmethylene)-amino]-but-2-enedinitrile (H2qm). The notable feature of this strategy is to generate a highly conjugated Schiff base platform with interesting binding properties. Remarkably, H2qm exhibited a visual sensing ability towards Cu2+ in 100% aqueous medium.

A quick accelerating microwave-assisted sustainable technique: permutated spiro-casing for imaging experiment.

A quick access tool for the one-pot, chromatography-free synthesis of the diversified dihydrospiro[indeno[1,2-b]pyridine-4,3'-indoline or acenaphthylene-1,4'-indeno[1,2-b]pyridine spiro-analogous via sustainable microwave condition in minimal 1:1 (v/v) aqueous ethanol without any metal catalyst is demonstrated here. This permutated spiro-casing was designed as fluorescence probe at physiological pH for selective detection of Zn, even in the presence of other competitive ions and showed a fluorescent enhancement with 1:1 metal/ligand complex. Moreover, this spiro sensor was successfully applied as an effective intracellular Zn imaging agent in the biomedical study of human hepatocellular liver carcinoma cells (HepG2) due to its cell permeability property.

Visual detection of fluoride ion based on ICT mechanism.

A novel chemosensor (HNTS) has been designed for a fast and accurate detection of F in acetonitrile medium. The UV-Vis, H, C NMR experiments and computational calculations demonstrate that HNTS probe offers a potential colorimetric sensor for discriminating F among other relevant anions. The detection limit is as low as 6 μM and a reversible colorimetric switch could be devised by sequential addition of F/Ca.

A versatile quinoxaline derivative serves as a colorimetric sensor for strongly acidic pH.

A facile and reliable method to monitor strongly acidic pH was developed. The sensing mechanism was found to involve the protonation-deprotonation equilibrium of the synthesized probe HQphy (1) (N-phenyl-N'-quinoxalin-2-ylmethylene-hydrazine) within a working range of pH 0.7-2.

A versatile chemosensor for the detection of Al and picric acid (PA) in aqueous solution.

Developing chemosensors for efficient detection of Al3+ and picric acid in water is in high demand but challenging. In this paper, we have demonstrated the potential of a probe, 6,6'-(1E,1'E)-(2-hydroxypropane-1,3-diyl)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(2-methoxyphenol) (H2Vm), as a "switch-on" Al3+ responsive fluorescence chemosensor in water. In addition to the ability of H2Vm to sense Al3+, the Al2-Vm2 complex offers selectivity towards picric acid (PA) in HEPES buffer (pH = 7.

Dihydroindeno[1,2-b]pyrroles: new Al selective off-on chemosensors for bio-imaging in living HepG2 cells.

In this study, a new molecular organic probe has been designed and synthesized by using recyclable, inexpensive and non-toxic polyethylene glycol (PEG-400) as a promoting reaction medium in water under environmentally benevolent conditions. The probe has been explored as a potential chemosensor to detect Al3+ ions using a HEPES buffer (pH = 7.4) solution.

I catalyzed access of spiro[indoline-3,4'-pyridine] appended amine dyad: new ON-OFF chemosensors for Cu and imaging in living cells.

An easy access to an amine-appended spiro[indoline-3,4'-pyridine] ON-OFF chemosensor by a one-pot four-component reaction using commercially available and an environmentally benign catalytic amount of molecular I (10 mol%) in aqueous ethanol at ambient temperature is described. The generated system could be utilized for the selective detection of Cu as it demonstrated a colorimetric naked eye change along with an ON-OFF fluorescence response towards Cu at physiological pH. The sensors exhibited high selectivity for Cu over other common cations with detection limit in the range of 10 (M).

A Schiff base platform: structures, sensing of Zn(ii) and PPi in aqueous medium and anticancer activity.

A reaction of N,N-bis(3-methoxysalicylidene) diethylenetriamine (H2Vd) and Zn(NO)·6HO, ZnBr, ZnI and Cd(NO)·4HO in a methanol solution led to zinc and cadmium complexes of different nuclearities, [Zn(Vd·H)(X)]·CHOH (X = NO, Br, I) [1a, 1b and 1c] and Cd(Vd)(NO) (2). In 1(a-c), two H2Vd ligands bridge the two metal centers whereas in 2, they provide sideways support to two terminal Cd ions, providing an all-oxygen envelope to the central Cd ion. All four compounds were characterized by elemental analysis, FT-IR spectroscopy and single crystal X-ray diffraction analysis.

Co, Co, and a Series of CoLn (Ln = Nd, Sm, Gd, Tb, Dy) Coordination Clusters: Search for Single Molecule Magnets.

We report herein the syntheses and investigation of the magnetic properties of a Co compound, a series of trinuclear CoLn (Ln = Nd, Sm, Gd, Tb, Dy) complexes, and a Co complex. The homometallic Co core was obtained from the reaction of Ln(NO)·xHO/Co(NO)·6HO/Hvab/EtN in a 0.5:0.

Heterometallic Cu(II)-Dy(III) Clusters of Different Nuclearities with Slow Magnetic Relaxation.

The synthesis, structures, and magnetic properties of two heterometallic Cu(II)-Dy(III) clusters are reported. The first structural motif displays a pentanuclear Cu(II)4Dy(III) core, while the second one reveals a nonanuclear Cu(II)6Dy(III)3 core. We employed o-vanillin-based Schiff base ligands combining o-vanillin with 3-amino-1-propanol, H2vap, (2-[(3-hydroxy-propylimino)-methyl]-6-methoxy-phenol), and 2-aminoethanol, H2vae, (2-[(3-hydroxy-ethylimino)-methyl]-6-methoxy-phenol).

Pyridoxal Based Fluorescent Chemosensor for Detection of Copper(II) in Solution With Moderate Selectivity and Live Cell Imaging.

A pyridoxal-based fluorescent probe HL was synthesized for the detection of Cu(2+) in methanol with moderate selectivity. Upon addition of Cu(2+), to the solution of the probe in methanol exhibited a remarkable change in emission at 500 nm. With the limit of detection of 10 μM, the probe could well meet the recommended (less than 32 μM in drinking water) of the World Health Organization (WHO).

Doubly chloro bridged dimeric copper(II) complex: magneto-structural correlation and anticancer activity.

We have synthesized and structurally characterized a new doubly chloro bridged dimeric copper(II) complex, [Cu2(μ-Cl)2(HL)2Cl2] (1) based on a Schiff base ligand, 5-[(pyridin-2-ylmethylene)-amino]-pentan-1-ol). Single crystal X-ray diffraction shows the presence of dinuclear copper(II) centres in a square pyramidal geometry linked by obtuse double chloro bridge. The magnetic study illustrated that weak antiferromagnetic interactions (J = -0.

Bis{2-[(5-hy-droxy-pent-yl)imino-meth-yl]phenolato-κ(2) N,O (1)}copper(II).

In the title compound, [Cu(C12H16NO2)2], the Cu(II) ion, located on a center of inversion, is coordinated by two singly deprotonated Schiff base ligands derived from condensation of salicyldehyde and 1-amino-pentan-5-ol. The imino N and phenol O atoms from both ligands offer a square-planar arrangement around the metal ion. The Cu-N and Cu-O bond lengths are 2.

Syntheses, crystal structures, and spectroscopic and magnetic properties of [Mn2III(H2L1)(Cl4Cat)4.2H2O] and [Mn2III(H2L2)(Cl4Cat)4.2CH3CN.2H2O]infinity: temperature-dependent valence tautomerism in solution.

The synthesis, X-ray data, and electronic structures of two manganese(III) 1D polymers ligated by tetrachlorocatechol, [Mn(2)(III)(H(2)L(1))(Cl(4)Cat)(4).2H(2)O](infinity) (1) and [Mn(2)(III)(H(2)L(2))(Cl(4)Cat)(4).2CH(3)CN.

New route to the mixed valence semiquinone-catecholate based mononuclear FeIII and catecholate based dinuclear MnIII complexes: first experimental evidence of valence tautomerism in an iron complex.

The semiquinone-catecholate based mixed valence complex, [FeIII(bispicen)(Cl4Cat)(Cl4SQ)] x DMF (1), and catecholate based (H2bispictn)[Mn2III(Cl4Cat)4(DMF)2] (2) (bispicen = N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine, bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine, Cl4Cat = tetrachlorocatecholate dianion, and Cl4SQ = tetrachlorosemiquinone radical anion) were synthesized directly utilizing a facile route. Both the complexes have been characterized by single crystal X-ray diffraction study. The electronic structures have been elucidated by UV-vis-NIR absorption spectroscopy, cyclic voltammetry, EPR, and magnetic properties.

Slow magnetic relaxation in a mixed-valence Mn(II/III) Complex: [MnII2(bispicen)2(mu 3-Cl)2Mn(III)(Cl4Cat)2Mn(III)(Cl4Cat)2(H2O)2] infinity.

A layered mixed-valence manganese complex, [Mn(II)(2)(bispicen)(2)(mu(3)-Cl)(2)Mn(III)(Cl(4)Cat)(2)Mn(III)(Cl(4)Cat)(2)(H(2)O)(2)](infinity), is synthesized and characterized structurally. It displays a slow magnetic relaxation and hysteresis effect.