Synthesis, characterization, theoretical investigations and fluorescent sensing behavior of oligomeric azine-based Fe3+Chemosensors

Three azine oligomeric esters were synthesized, characterized by IR, UV, 1H, 13C{1H} and GPC technique, and applied to chemosensor application. The sensitivity response of the oligomers towards the metal ion was evaluated for a metal ion series. The results have shown selective and sensitive “turn off” fluorescence response towards Fe3+ ion in DMF/H2O (1:1, pH: 7.4, fluorophore: 5 μM) solution. The binding stoichiometry and binding constant of the fluorophores were calculated using the Stern–Volmer equation and Benesi–Hildebrand plots, respectively. The quenching of fluorophores on the addition of Fe3+ ion indicates the capability of fluorophore towards quantitative analysis of Fe3+. The dimer of oligomers was theoretically studied using DFT, B3LYP/6-311G level basic set to support and explain the quenching mechanism of LMCT, PET process and to explain the DC, AC electrical studies results. The electrical conductivity measurements of solid-state, I2 doped and undoped oligomers were carried out and the conductivity gradually increases with increase in iodine vapor contact time of oligomers. The electrical conductivity was related with band gap and charge density values of imine nitrogen obtained by Huckel calculations. The dielectric measurements at different temperatures and frequencies were made by two probe method. Among the oligomers, EBHAP has recorded a high dielectric constant at the low applied frequency of 50 Hz at 373 K due to loosely attached π bonds resulting good polarization.

Formation of a macrocycle from dichlorodimethylsilane and a pyridoxalimine Schiff base ligand

The reaction of dichlorodimethylsilane with a polydentate Schiff base ligand derived from pyridoxal and 2-ethanolamine yielded the macrocyclic silicon compound (8E,22E)-4,4,12,18,18,26-hexamethyl-3,5,17,19-tetraoxa-8,13,22,27-tetraaza-4,18-disilatricyclo[22.4.0.010,15]octacosa-1(24),8,10,12,14,22,25,27-octaene-11,25-diol, C24H36N4O6Si2. The asymmetric unit contains the half macrocycle with an intramolecular O—H...N hydrogen bond between the imine nitrogen atom and a neighbouring oxygen atom. The crystal structure is dominated by C—H...O and C—H...π interactions, which form a high ordered molecular network.

Synthesis and Diagnoses of New Metal Ions Complexes derived from Trimethoprim Schiff Bases

A New Schiff base (o-hydroxy benzylidene trimethoprim) derived from trimethoprim (known as a drug) was used as a ligand in this study, has been synthesized by condensation reaction from equal amounts of ortho hydroxybenzaldehyde and trimethoprim. This was then used for the preparation of new complexes by the reaction with Zinc and Manganese salts. The synthesized complexes were in the formula [M(OHTMP)2]X2 in the natural medium and [M(OHTMP)2-H] in basic medium (M=Zn, Mn, OHTMP = o-hydroxy benzylidene trimethoprim X= CH3COO, NO3, Cl2). The prepared complexes were diagnosed and characterized by employing FT-IR, 1H- NMR, CHN element analysis, molar conductivity, Molar refraction and flame atomic absorption techniques. Spectroscopic results proved the chelation behavior of this ligand. It coordinated to the metal ions as a tridentate ligand, via the imine nitrogen, azo methine, and phenolic oxygen atoms. According to the obtained results, octahedral geometry has been suggested for prepared complexes. The biological activities of the prepared ligand and complexes against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Klebsiella spp.) have being conducted. Both, the ligand and complexes showed anti-bacterial activities, beter than that of the Trimethoprim.

Metal Complexes of π-expanded Ligand (5): Synthesis, Structural, and Photophysical Characterizations of Green-Red Luminescent Pyrene-based Salicylaldiminato-type Zinc Complexes

A series of pyrene-based salicylaldimine-type ligands containing n-octyl or cyclohexyl or phenyl groups at imine nitrogen group, 1-hydroxy-2-[(N-substituted-imino)methyl]-pyrenes (octyl 1, cyclohexyl 1b and phenyl 1c), were synthesized and characterized. The ligands reacting with zinc acetate in the presence of sodium acetate gave the bis(salicylaldiminato)-type Zn(II) complexes, [bis[2-[(N-substituted-imino)methyl]-1-pyrenolato-N,O] zinc(II)] (octyl 1(Zn), cyclohexyl 1b(Zn), phenyl 1c(Zn)). The new ligands and complexes were characterized by 1H NMR, IR spectroscopy, mass spectroscopy, elemental analysis, UV-vis spectroscopy, fluorescence spectroscopy, and X-ray diffraction. The influence of the π-extended conjugation of the pyrene-based salicylaldiminato-type ligands coordinated to Zn2+ greatly induces red-shift of the complexes 1(Zn), 1b(Zn) and 1c(Zn) in absorption and emission spectra. These results were confirmed by density-functional theory (DFT) and time-dependent DFT (TDDFT) molecular orbital calculations. Moreover, single crystal structure of simple salicylaldiminato Zn(II) complex 1’b(Zn) was compared to that of the corresponding pyrene-type salicylaldiminato complex 1b(Zn).

A Highly Selective Turn-On Fluorescent Probe for the Detection of Zinc

A novel turn-on fluorescence probe L has been designed that exhibits high selectivity and sensitivity with a detection limit of 9.53 × 10−8 mol/L for the quantification of Zn2+. 1H-NMR spectroscopy and single crystal X-ray diffraction analysis revealed the unsymmetrical nature of the structure of the Schiff base probe L. An emission titration experiment in the presence of different molar fractions of Zn2+ was used to perform a Job’s plot analysis. The results showed that the stoichiometric ratio of the complex formed by L and Zn2+ was 1:1. Moreover, the molecular structure of the mononuclear Cu complex reveals one ligand L coordinates with one Cu atom in the asymmetric unit. On adding CuCl2 to the ZnCl2/L system, a Cu-Zn complex was formed and a strong quenching behavior was observed, which inferred that the Cu2+ displaced Zn2+ to coordinate with the imine nitrogen atoms and hydroxyl oxygen atoms of probe L.

N-Triflination of pyrazolones: A new method for N-S bond formation

A simple method is developed for N-triflination of pyrazolones using CF3SO2Na (Langlois reagent) and phenyliodine(III)bis(trifluoroacetate) (PIFA), which occurs quickly in 5 min. The reaction works at the imine nitrogen centre...

2-({[(2S)-1-Hydroxy-1,1,3-triphenylpropan-2-yl]imino}methyl)-4,6-bis(4-methylphenyl)phenol

The title compound, C42H37NO2, crystallizes in the orthorhombic space group P212121 with one molecule in the asymmetric unit. An intramolecular hydrogen bond orients the phenol hydroxyl group toward the imine nitrogen. The aliphatic alcohol is engaged in a weak intramolecular hydrogen bond with the imine nitrogen.

Pyridinyl Conjugate of UiO-66-NH2 as Chemosensor for the Sequential Detection of Iron and Pyrophosphate Ion in Aqueous Media

A new chemosensor UiO-66-N-Py (Py = 2-methinepyridine, N = imine nitrogen) based on isoreticular UiO-66 (University of Oslo) Metal–Organic Framework (MOF) containing 2-methinepyridine functionalized organic linker was solvothermally synthesized and characterized. This UiO-66-N-Py was very selective and sensitive for detecting the Fe3+ ion and sequential detection of the pyrophosphate (PPi) anion. The limits of detection for the Fe3+ ion and PPi were calculated to be 10 ppb (0.19 μM) and 50 ppb (0.3 μM), respectively. The quenching constant Ksv for Fe3+ and the binding constant for PPi were 1.4 × 105 M−1 and 1.7 × 105 M−1, respectively. The functionalization of UiO-66-NH2 with 2-methinepyridine enhanced its fluorescence emission properties and introduced more binding sites for the analytes. We additionally studied the interaction of the sensor and the analytes with Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This chemosensor also demonstrated a regenerative emission property without loss in the detection ability for six consecutive cycles.