Schiff Base Units Research Articles

Synthesis and characterization of a novel liquid crystalline side chain metallopolymer

The synthesis of a novel kind of form-retaining liquid crystalline crosslinked metallopolymer is reported. Copper(II) is complexed by Schiff's base units as part of a mesogenic side chain polymer. This leads to remarkable antiferromagnetic exchange interactions between the copper centers that are not present in related monomeric model compounds. IR spectroscopic investigations in the region 4000-200 cm -1 , X-ray diffractometry and temperature dependent magnetic susceptibility measurements were carried out to elucidate the structure of this new material. The observed considerably strong antiferromagnetic coupling is assumed to be due to the interactions between the copper centers through oxygen bridges in the polymeric matrix.

Synthesis and characterization of a novel liquid crystalline side chain metallopolymer

The synthesis of a novel kind of form-retaining liquid crystalline crosslinked metallopolymer is reported. Copper(II) is complexed by Schiff's base units as part of a mesogenic side chain polymer. This leads to remarkable antiferromagnetic exchange interactions between the copper centers that are not present in related monomeric model compounds. IR spectroscopic investigations in the region 4000–200 cm−1, X-ray diffractometry and temperature dependent magnetic susceptibility measurements were carried out to elucidate the structure of this new material. The observed considerably strong antiferromagnetic coupling is assumed to be due to the interactions between the copper centers through oxygen bridges in the polymeric matrix.

A novel class of non-chiral banana-shaped liquid crystals with ferroelectric properties

The first banana-shaped molecules without Schiff-base units, with broad regions of a ferroelectric switchable liquid crystalline phase and low melting points, have been obtained.

Synthesis of 4-tert-Butylcalix[4]arenes Bearing Two Schiff-Base Units at the Lower Rim

An approach for synthesis of 4-tert-butylcalix[4]arenes bearing two Schiff base units at the lower rim 4a-u in excellent yields is described. All 21 compounds 4a-u have been achieved by treatment of 1,3-distally substituent 4-tert-butylcalix[4]arene amine 3 with aromatic or heterocyclic aldehydes in ethanol.

Schiff Base p-tert-Butylcalix[4]arenes. Synthesis and Metal Ion Complexation

The article describes the synthesis of Schiff base p-tert-butylcalix[4]arenes 3a-e in which the Schiff base unit bridges two opposite hydroxy groups of p-tert-butylcalix[4]arene (1). The synthesis of 3a-e have been achieved by refluxing p-tert-butylcalix[4] arene 1,3-dicarbaldehyde 2 with appropriate diamino compounds in acetonitrile-methanol. Yields range from 14 to 96%. The complexing properties of 3a-e toward alkali and alkaline earth cations, transition and heavy metals, and lanthanides are reported

Mixed ligand five coordinate cobalt(II) complexes of a polymer‐bound schiff base derived from 2‐aminobenzimidazole

AbstractThe complexes resulting from the interaction of a new Schiff base ligand derived from crosslinked polystyrene bound benzaldehyde and 2‐aminobenzimidazole with a square planar complex [Co(TPP)] (where TPP = meso‐tetraphenylporphyrin), and also with tetrahedral complexes [Co(BPBI)2X2] (where BPBI = 1‐benzyl‐2‐phenylbenzimidazole, X = Cl, Br, or NCS) have been isolated and characterized. The percentages of cobalt and nitrogen in the complexes show that only one Schiff base unit is coordinated to cobalt. Infrared spectra suggest that the bonding of the polymer ligand to cobalt is through the N‐3 atom of the benzimidazole moiety. The EPR spectra indicate that all the complexes are in the low‐spin state and have a square pyramidal environment around cobalt(II). © 1992 John Wiley & Sons, Inc.

A Schiff basep-tent-butylcalix[4]arene. Synthesis and metal ion complexation

This communication describes the synthesis of Schiff base calix[4]arene (1) in which the Schiff base unit bridges two opposite hydroxy groups ofp-tert-butylcalix[4]arene. The synthesis of (1) has been achieved by refluxing in acetonitrile-methanol the appropriate 1,3-dicarbaldehyde-p-tert-butyl-calix[4]arene (4) with 1,3-diaminopropane. The yield of the reaction is 19%. Ligand (1) possesses a compartment containing two nitrogen atoms, four ether-type oxygen atoms, and two ionizable hydroxy groups likely to complex metal cations.

22 Inter-laboratory evaluation of aminotransferase assays: Influence of pyridoxal phosphate on precision of IFCC methods

Three dinuclear complexes formed by the reaction of Gd(hfa)3 (hfa is hexafluoroacetylacetonate) with Schiff base complexes of Cu(II) and Ni(II) have been synthesized and characterized. The crystal structures of the complexes [Gd(hfa)3M(prpen)] {M=Cu(II (1)), Ni(II) (2)} are reported. (H2prpen is the Schiff base derived from the condensation of 2 equiv. of 2-hydroxypropiophenone and 1 equiv. of ethylenediamine.) Both 1 and 2 are discrete dinuclear complexes consisting of an eight coordinate Gd atom which is bridged to four coordinate M(II) via both phenolate oxygen atoms of the prpen ligand. The crystal structure shows there is no tendency toward dimerization between adjacent Cu(II) Schiff base units in 1. Cryomagnetic measurements show a ferromagnetic interaction between Gd(III) and Cu(II) in 1 as predicted by theory with J=1.91 cm−1. The reaction of Gd(hfa)3 with Ni(L) (H2L is the Schiff base derived from the condensation of 1 equiv. each of 5-chlorobenzophenone, 1,2-diaminobenzene, and 5-methyl-4-imidazolecarboxaldehyde) produced Gd(hfa)3Ni(L) (3) in which imidazolate is available to bridge Gd(III) and Ni(II).

Binuclear complexes of copper(II) and zinc(II) halides with bidentate and quadridentate Schiff base complexes

Binuclear complexes of the types CuB,CuCl2, CuB,ZnCl2, ZnB,ZnCl2, and CuL2,CuCl2 have been obtained where BH2 is a quadridentate Schiff base derived from salicylaldehyde and a polyrnethylenediamine and LH is an N-alkylsalicylaldimine. The stereochemistry of the copper atoms in the binuclear complexes is inferred from comparisons of their reflectance spectra with the spectra of the simple copper complexes CuB and CuL2. The structures of the zinc complexes are discussed by reference to near ultraviolet spectra of the ligands and infrared spectra in the 1500-1560 cm-1 region. The evidence suggests that in the complexes of the type MB,M'Cl2 either but not both metal atoms may approach a tetrahedral environment. The chemistry of the complexes ZnB,ZnCl2 is complicated by the possibility of either or both zinc atoms becoming 5 coordinate by addition of solvent molecules; in some of these complexes the zinc chloride appears to be attached to a solvent molecule in a 5-coordinate Schiff base unit, rather than by bridging through phenolic oxygen atoms. The oomplexes CuL2,CuCl2 apparently have a symmetrical binuclear structure based on a trans arrangement of the Schiff base units rather than an unsymmetrical structure resembling that of the complexes CuB,CuCl2. Complexes of the types CuL2,ZnCl2 and ZnL2,ZnCl2 could not be obtained.