Showing papers on "Schiff base published in 1975"
TL;DR: In this article, the driving forces leading to the formation of ternary Cu2+ complexes are outlined; they are (i) statistical reasons, neutralization of charge in the mixed-ligand complexes, steric factors (bulky groups, ring size of chelates), and formation of π bonds.
Abstract: The driving forces leading to the formation of ternary Cu2+ complexes are outlined; they are (i) statistical reasons, (ii) neutralization of charge in the mixed-ligand complexes, (iii) steric factors (bulky groups, ring size of chelates), and (iv) formation of π bonds. The last point is important for achieving a large stability, as well as for the observation of discriminating qualities. An additional stability increase may possibly be achieved through a direct interaction between the two ligands bound to the same metal ion, i.e. Schiff base formation, hydrogen bonding or a charge-transfer relation. The latter leads to distinct structures, i.e. metal ion-bridged charge-transfer complexes. The relation between stability and structure on the reactivity of mixed-ligand complexes is emphasized. The relevance of the results for mixed-ligand complexes containing metal ions other than Cu2+ is briefly outlined.
301 citations
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76 citations
TL;DR: In this article, Lanthanide adducts with N,N′-bis(salicylidene)-1,3-propylendiamine and N, N′-bi-idene-1, 3-propYLendiamin-2-olo have been prepared, where the molecules of the SCHIFF bases are coordinated with the metal ion.
Abstract: Lanthanide adducts with N,N′-bis(salicylidene)-1,3-propylendiamine and N,N′-bis(salicylidene)-1,3-propylendiamine-2-olo have been prepared. It is noted that the molecules, and not anions, of the SCHIFF bases are coordinated with the metal ion.
Bi- and trinuclear lanthanide complexes with the “complex ligand”, N,N′-1,3-propylen-bis-(salicylideniminato)copper(II), coordinating as a bidentate ligand, have also been isolated.
The compounds have been characterized by elemental analyses, molar conductance, electronic and infrared spectra. Possible structures for the complexes have been proposed.
Verbindungen von Lanthaniden mit SCHIFFschen Basen und Kupferkomplexen von SCHIFFschen Basen
Lanthaniden-Addukte mit N,N′-bis(salicyliden)-1,3-propylendiamin und mit N,N′-bis(salicyliden)-1,3-propylendiamin-2-ol wurden dargestellt. SCHIFFsche Basen sind, in diesen Addukten, in nicht anionischer Form mit dem Metallion gebunden.
Es wurden auch zwei- sowie dreikernige Lanthaniden-Komplexe mit N,N′-1,3-propylen-bis-(salicylideniminato)Kupfer(II), als zweizahnige Liganden, isoliert.
Die untersuchten Verbindungen wurden durch Analyse, elektrische Leitfahigkeit, UV und IR-Spektren charakterisiert. Mogliche Strukturvorschlage werden vorgeschlagen.
74 citations
TL;DR: Stability of thiazolidine-4-carboxylic acids and chain tautomerism are studied in acidic, basic and neutral solution in this article, where it is suggested that this reaction may proceed through a sulfonium ion intermediate.
63 citations
TL;DR: Antibody did effect a small rate enhancement for the pyridoxal-P-catalyzed transamination of L-tyrosine, and these results are discussed in light of current ideas in the mechanisms of enzyme catalysis.
Abstract: Reduced Schiff base compounds of pyridoxal-P and tyrosine, which were used to induce specific antibodies described in the preceding article (V. Raso and B. D. Stolar, Biochemistry, 1975), caused active site-directed inhibition of tyrosine transaminase and tyrosine decarboxylase. The antibodies, studied as analogs of enzymes, were able to bind an unsaturated Schiff base catalytic intermediate, as shown by equilibrium dialysis and absorbance difference spectroscopy. Schiff base formation can proceed while the pyridoxal-P and tyrosine are within the antibody combining site, but the rate of this bimolecular condensation within the sites was not greater than the rate in free solution. Antibody did effect a small rate enhancement for the pyridoxal-P-catalyzed transamination of L-tyrosine. These results are discussed in light of current ideas in the mechanisms of enzyme catalysis.
58 citations
TL;DR: In this paper, the synthesis and characterisation of several dibasic tridentate Schiff base ligands (H2SB) are described, and structural formulas for the isolated ligands are suggested on the basis of infrared, nucle...
Abstract: The synthesis and characterisation of several dibasic tridentate Schiff base ligands (H2SB) are described. Structural formulas for the isolated ligands are suggested on the basis of infrared, nucle...
55 citations
TL;DR: The reaction of 6-aminocaproic acid with pyridoxal-P to form the Schiff base N6-(P-pyrid Oxylidene)-aminocAProic Acid was studied as a model for formation of Schiff base on the holoenzyme.
44 citations
41 citations
TL;DR: In this article, the separation of neutral copper and nickel chelates of two representative Schiff base ligands, N,N'-ethylenebis(acetylacetoneimine) and N, N'-methylene-bis(salicylaldimine), is reported on a column of 10-μm diameter silica.
TL;DR: In this paper, reverse phase partition chromatography is applied to a 10 micron silica-bonded octadecyl hydrocarbon substrate to the separation of neutral tetradentate chelates of copper, nickel and palladium.
Abstract: Reverse phase partition chromatography on a 10 micron silica-bonded octadecyl hydrocarbon substrate is applied to the separation of neutral tetradentate chelates of copper (II), nickel (II) and palladium (II) with a range of non-fluorinated and fluorinated beta-ketoamine and salicylaldimine ligands. Variation of retention and resolution with respect to changes in ligand structure and metal chelated is investigated using acetonitrile, methanol and water solvent systems. Detection limits (254 nm) and linearity ranges of response are indicated.
TL;DR: In this paper, single crystal e.r.t. studies have been done on N,N′-ethylenebis(o-aminobenzylideniminato)nickel(II) and N, N′ -ethylene bis(benzoylacetoniminiato)nikkel (II) doped with the corresponding Co(II and Cu(...
Abstract: Single crystal e.s.r. studies have been done on N,N′-ethylenebis(o-aminobenzylideniminato)nickel(II) and N,N′-ethylenebis(benzoylacetoniminato)nickel(II) doped with the corresponding Co(II) and Cu(...
TL;DR: CNDO/2 calculations on all‐trans and 11‐cis Schiff base and SB‐H+ indicate that, for torsional angles of approximately 80–100° around the 11–12 double bond, QN* < QN, which suggests that it may be possible for the proton to come off the imine nitrogen during isomerization from 11 ‐cis SB‐h+ to all‐ trans SB‐ H+.
Abstract: — The acid dissociation constants of protonated all-trans retinal Schiff base (SB-H+) in a 50% water-methanol solution at 0°C is 6–95 for the ground state and nominally 16–65 for the first excited singlet state, with a potential range of ˜ 12–21. These values are in qualitative agreement with the results of semiempirical MO calculations, which indicate that the total charge density on nitrogen is greater in the first excited singlet than in the ground state (QN* > QN). However, pertinent to vision, CNDO/2 calculations on all-trans and 11-cis Schiff base and SB-H+ indicate that, for torsional angles of approximately 80–100° around the 11–12 double bond, QN* < QN. This result suggests that it may be possible for the proton to come off the imine nitrogen during isomerization from 11 -cis SB-H+ to all-trans SB-H+. The potential consequence of this during isomerization of rhodopsin is the initiation of unfolding of the protein opsin.
01 Mar 1975
TL;DR: The immobilized enzymes obtained were shown to possess higher thermal stability and higher resistance to denaturing agents than the free counterparts, and to be fairly higher than that catalyzed by the respective free enzyme.
Abstract: Production of L-tryptophan, L-tyrosine, or their analogues was attempted using immobilized tryptophanase or β-tyrosinase. The immobilized tryptophanase used in this study was first prepared by the present authors by coupling of free apoenzyme fromEscherichia coli B/1t-7A to pyridoxal 5′-phosphate (PLP) previously bound on Sepharose. This immobilization method involves the formation of Schiff base linkage between 4-formyl group of Sepharose-bound PLP and the α-amino group of the lysine residue of the catalytic center of one subunit of tetrameric apotryptophanase, followed by reductive fixation of the Schiff base linkage with NaBH4. In the case of β-tyrosinase fromEscherichia intermedia having two catalytic centers, however, immobilization by direct coupling to CNBr-activated Sepharose or a bromoacetyl derivative of Sepharose was more suitable than by the coupling to Sepharose-bound PLP. In each case, the affinity for substrate or coenzyme was scarcely affected by the immobilization. The immobilized enzymes thus obtained were shown to possess higher thermal stability and higher resistance to denaturing agents than the free counterparts. The optimal temperature for a short time reaction (10 min) was ca. 70°C for immobilized tryptophanase or 55°C for immobilized β-tyrosinase. In each case the optimal reaction temperature mediated by the immobilized enzyme was fairly higher than that catalyzed by the respective free enzyme. Addition of ethanol (5%, V/V) to the reaction mixtures favored the tryptophanase and β-tyrosinase reactions. The equilibrium of α, β-elimination reactions of L-tryptophan and β-tyrosine lied so far to the synthetic side (70% in tryptophanase and 80% in β-tyrosinase reactions, respectively). By continuous flow methods using these immobilized enzyme columns, L-tryptophan, L-tyrosine, and their analogues, such as L-DOPA and L-5-hydroxytryptophan, were conveniently synthesized in good yields.
TL;DR: In this paper, a new class of mixed ligand complexes of uranium (VI) is reported, which contain hepta-coordinated uranium with irregular pentagonal bipiramidal geometry.
TL;DR: The discovery of these pyridoxal-P dependent reactions of β,γ-unsaturated amino acids lends weight to previous proposals by others that pyridine-P Schiff base derivatives of α-keto acids are intermediates in γ-elimination reactions and inγ,β-isomerization reactions.
Patent•
27 May 1975
TL;DR: Aromatic polyimides with Schiff base end groups are chain-extended (molecular weight increase) by heating the polyimide, preferably in the presence of Lewis acid salts as catalyst as discussed by the authors.
Abstract: Aromatic polyimides with Schiff base end groups are chain-extended (molecular weight increase) by heating the polyimides, preferably in the presence of Lewis acid salts as catalyst. Molecular weights are increased with little or no by-product formation. The polyimides can be shaped and formed prior to the polymerization. The aromatic polyimides appropriate for chain-extending are formed by the reaction of aromatic dianhydrides, aromatic diamines and a Schiff base monoamine such as p-amino-benzylidene-aniline, p-amino-benzylidene-4-vinylaniline and p-aminobenzylidine-4-ethynylaniline.
TL;DR: In this article, the synthesis and characterization of some uranyl complexes containing macrocyclic Schiff base ligands are reported, and these cyclic complexes may act as ligands towards trasition metal ions.
TL;DR: The Schiff base 2,6-pyridinediylbis(N-hydroxyphenylaldimine) is obtained by the condensation of 2, 6-Pyrinedinedicarboxaldehyde with o-aminophenol.
TL;DR: The mass spectrum of the Schiff base formed by the condensation of ethylenediamine and trifluoro-acetylacetone shows that the compound is N,N-ethylenebis(1,1, 1-trifluor-4-iminopentan-2-one) as discussed by the authors.
Abstract: The mass spectrum of the Schiff base formed by the condensation of ethylenediamine and trifluoro-acetylacetone shows that the compound is N,N-ethylenebis(1,1,1-trifluoro-4-iminopentan-2-one). The mass spectra of the nickel(II), palladium(II) and copper(II) chelates of the Schiff base confirm this structure for the ligand. Mechanisms are proposed for some of the fragmentation reactions which occur in the mass spectrometer.
TL;DR: The complexes formed between the lanthanide ions and the Schiff base N-Salicylideneanthranilic acid ( LH 2 ) in the presence of pyridine have been isolated and characterized as discussed by the authors.
TL;DR: In this article, the synthesis and properties of oxotitanium(IV) complexes with tetradentate Schiff bases produced by the condensation of two moles of salicylaldehyde with one mole of optically active 1,2-diamine are described.
TL;DR: In this article, a series of Cu and Cu:Zn coordination compounds of X -salicylaldehyde-amino acid Schiff bases were prepared with X 4OH, H, 5NO 2, 5Cl and glycine, alanine and phenylglycine The magnetic and spectral parameters were obtained and utilized in the calculation of molecular orbital coefficients for these coordination compounds.
TL;DR: In this paper, a tetradentate Schiff base including salen was synthesized, where salen = NN′-ethylenebis(salicylideneiminate).
Abstract: Iron(III) complexes with several tetradentate Schiff Bases [FeLXY]n+ and [Fe salen CN] were synthesized, where L is a tetradentate Schiff Base including salen = NN′-ethylenebis(salicylideneiminate)...