Magnetic and spectral studies on nickel(II) and copper(II) dithiocarbazates derived from isoniazid

Some isonicotinoyldithiocarbazate complexes of nickel(II) and copper(II), of general formulae M(IN-Dtcz)₂, [M(IN-DtczH)₂]Cl₂, and [M(IN-DtczH-Sal)₂]Cl₂ (M?=?Ni(II), Cu(II); INDtcz?=?isonicotinoyldithiocarbazate; IN-DtczH?=?isonicotinoyldithiocarbazic acid; IN-DtczH-Sal?=?salicylaldehyde Schiff base of isonicotinoyldithiocarbazic acid), have been synthesized. These complexes have been investigated by elemental analyses, mass, room temperature infrared and electronic spectra, and variable temperature magnetic susceptibility measurements. The three nickel(II) dithiocarbazates and [Cu(IN-DtczH-Sal)₂]Cl₂ exhibit NS linkage of the ligands, while Cu(IN-Dtcz)₂ and [Cu(IN-DtczH)₂]Cl₂ have ONS binding of the ligands. The nickel(II) dithiocarbazates have [NiN₂S₂] chromophore. Magnetic and solution electronic absorption spectral data reveal square-planar geometry for Ni(IN-Dtcz)₂ and the existence of square-planar–tetrahedral equilibrium for [Ni(IN-DtczH)₂]Cl₂ and [Ni(IN-DtczH-Sal)₂]Cl₂. Copper(II) dithiocarbazates, namely Cu(IN-Dtcz)₂, [Cu(IN-DtczH)₂]Cl₂, with ONS ligands having dimeric or polymeric octahedral structures, and [Cu(IN-DtczH-Sal)₂]Cl₂, with NS binding having dimeric square-planar structure, exhibit antiferromagnetism. Superexchange pathway involving the bridging nitrogen and sulfur of the isonicotinoyldithiocarbazate ligands rather than direct metal–metal exchange is suggested for antiferromagnetic interactions. The spin exchange parameter, ?2J?=?202.14 and 29.26?cm^?1, has been evaluated for [Cu(IN-DtczH)₂]Cl₂ and [Cu(IN-DtczH-Sal)₂]Cl₂, respectively, while it could not be evaluated for Cu(IN-Dtcz)₂ because the slope was negative due to the non-variation of its magnetic moment with temperature. The difference in antiferromagnetic behavior and inconsistency of 2J for [Cu(IN-DtczH-Sal)₂]Cl₂ has been attributed to different electronic and steric factors of the three ligands, that is, isonicotinoyldithiocarbazate, its acid, and salicylaldehyde Schiff-base derivative.     

Preconcentration and Determination of Copper(II) at a Chemically Modified Electrode Containing Salicylaldehyde Thiosemicarbazone

A chemically modified electrode (CME) containing salicylaldehyde thiosemicarbazone (TSCsal) was evaluated for the ability to preconcentrate copper(II) prior to quantification by voltammetry. The CME has been used for the very sensitive and selective analysis of trace amounts of copper(II). A detection limit of 0.1 ppb was obtained by applying anodic stripping voltammetry with a flow system. The parameters that affect the sensitivity and possible interference by other ions or chelating agents have been examined in detail. The CME exhibits high stability and the response could be reproduced for four preconcentration-determination-renewal cycles [10ppbCu(II)] with a 2.87% relative standard deviation. The proposed method has been applied to the determination of copper(II) in tap water, drinking water, and NASS-3 standard reference sea water samples. The results gave satisfactory recoveries.     

Efficient synthesis of functionalized 1,3-dihydroisobenzofurans from salicylaldehydes:Application to the synthesis of escitalopram

An efficient synthesis of substituted 1,3-dihydroisobenzofurans is developed. In this novel route, oaroylbenzaldehydes, as key intermediates, can be obtained by lead tetraacetate oxidation of Naroylhydrazones of salicylaldehydes. The mild and general strategy enables the synthesis of various substituted 1,3-dihydroisobenzofurans in high yields. Moreover, this method can be applied to efficiently synthesize escitalopram.     

Chemical and electrocatalytic cascade cyclization of salicylaldehyde with three molecules of malononitrile: ‘one-pot’ simple and efficient way to the chromeno[2,3-b]pyridine scaffold

А new type of catalytic cascade cyclization was found: the direct ‘one-pot’ simple and efficient transformation of salicylaldehyde and three molecules of malononitrile into the chromeno[2,3-b]pyridine systems. Chemical and electrochemical methods result in direct ‘one-pot’ formation of chromeno[2,3-b]pyridines in 60–90% yields. The implication of electrocatalysis in complex cascade cyclization reaction is an efficient approach to medicinally relevant chromeno[2,3-b]pyridines—the promising small-molecule ligands with pronounced antihistamic, antirheumatic and antiasthmatic activities. The electrocatalytic method is beneficial from the viewpoint of diversity-oriented large-scale processes and represents fast efficient and environmentally benign synthetic concept for cascade reactions strategy.     

Aluminum(III)‐selective PVC Membrane Electrode Based on Salicylaldehyde Salicyloyl Hydrazone

A highly selective PVC membrane electrode for Al³⁺ based on salicylaldehyde salicyloyl hydrazone as a neutral carrier has been prepared and studied. The sensor exhibits a good response for Al³⁺ over a linear range of 9.0 × 10^‐6 to 1.0 × 10^‐1 mol/L, with a Nernstian slope of 20.0 ± 0.2 mV/decade and detection limit of 7.0 × 10^‐6 mol/L. Selectivity coefficients determined by the method of separate solution indicate high selectivity for Al³⁺. The response mechanism was discussed in view of UV‐Vis spectroscopy technique and the A.C. impedance technique. It was used as an indicator electrode in potentiometric titration of Al3+ with EDTA and in the determination of Al³⁺ in real samples. The electrode has a relatively fast response time, long life time and satisfactory stability.     

Synthesis of 2,2-difluoro-2H-chromenes through the tandem reaction of ethyl 3-bromo-3,3-difluoropropionate with salicylaldehyde derivatives

A series of 2,2-difluoro-2H-chromenes were synthesized from the tandem reactions of ethyl 3-bromo-3,3-difluoropropionate with salicylaldehyde derivatives in good yields under basic conditions. In acidic environment defluorination took place during the reaction. A plausible mechanism was proposed based on the experimental results.     

Kinetic Spectrophotometric Determination of Manganese by Use of the Salicylaldehyde-Hydrogen Peroxide System

Abstract

A kinetic method is described for determining trace amounts of manganese(II), based on its catalytic effect on the oxidation of salicylaldehyde by hydrogen peroxide. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 500 nm. The calibration graph is linear in the range 5–100 ng/ml with a relative error of ± 1.2%. The method has been applied to the determination of manganese in natural water.     

Synthesis,characterization and biocidal activities of some metal(II) complexes with diacetyl salicylaldehyde acyldihydrazones

Complexes of diacetyl salicylaldehyde oxalic acid dihydrazone, CH₃COC(CH₃)= NNHCOCONHN=CHC₆H₄(OH),(dsodh) and diacetyl salicylaldehyde malonic acid dihydrazone CH₃COC(CH₃)=NNHCOCH₂CONHN=CHC₆H₄(OH), (dsmdh) of general compositions [M(L)]Cl, [M′(L)Cl], [M(L′)]Cl and [M′(L′)Cl] (where M?=?Co(II), Cu(II), Zn(II), Cd(II) and M′?=?Ni(II); HL?=?dsodh and HL′?=?dsmdh) were prepared and characterized by elemental analyses, molar conductance, magnetic moments, electronic, ESR and infrared spectra and X-ray diffraction data. The magnetic moments and electronic spectra indicate six-coordinate octahedral geometry for Co(II) and square planar geometry for Ni(II) complexes. The ESR spectral data of Cu(II) complexes in DMF solution reveal a tetragonally distorted octahedral geometry. Both ligands bond through >C=O, >C=N and deprotonated phenolate groups in all octahedral complexes and through >C=N and deprotonated phenolate groups in Ni(II) square planar complexes. The lattice parameters for Cu(dsodh) and Co(dsmdh) correspond to an orthorhombic and Ni(dsodh) corresponds to a tetragonal crystal lattice.

The complexes show significant antifungal activity against a number of pathogenic fungi viz. Stemphylium, Myrothecium and Alternaria. The antibacterial activity was studied against Pseudomonas fluorescence (gram ?ve) and Clostridium thermocellum (gram +ve).     

Coordination modes of two flexidentate salicylaldimine ligands derived from N-(3-aminopropyl)morpholine toward zinc and copper

Two flexidentate Schiff-base ligands condensed from salicylaldehyde or 5-chlorosalicylaldehyde with N-(3-aminopropyl)morpholine were prepared in situ and reacted with Zn(II) and Cu(II) salts. Upon complexation, the Schiff bases underwent deprotonation at hydroxyl to act as mono-anionic ligands. When a ligand?:?metal ratio of 2?:?1 was applied, the deprotonated Schiff bases coordinated metal ions through phenolate and imine in a square-planar or tetrahedral geometry. In contrast, 5-chlorosalicylaldimine reacted with the metal ions in a 1?:?1 ratio to form complexes wherein morpholine nitrogen also participates in an N,N,O-tridentate coordination mode. The structures of the complexes were characterized by spectroscopic methods and single-crystal X-ray diffraction.