scholarly journals When the Metal Makes the Difference: Template Syntheses of Tridentate and Tetradentate Salen-Type Schiff Base Ligands and Related Complexes

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 483
Author(s):  
Rita Mazzoni ◽  
Fabrizio Roncaglia ◽  
Luca Rigamonti
Keyword(s):  
Schiff Base ◽  
Organic Molecules ◽  
Lone Pair ◽  
Metal Center ◽  
Primary Amines ◽  
Template Effect ◽  
Schiff Base Ligands ◽  
Amine Groups ◽  
The Difference ◽  
The One

The reaction of organic molecules mediated by a metal center (template synthesis) can result in a final connectivity that may differ from the one obtained in the absence of the metal. The condensation of carbonyl fragments with primary amines form C=N iminic bonds, the so-called Schiff bases, which can act as ligands for the templating metal center by means of the lone pair on the nitrogen atom. This review focuses on the template methods for the reaction between a carbonyl compound (mainly salicylaldehyde) and a primary aliphatic diamine able to prevent the double condensation on both amine groups and obtain tridentate N2O ligands. These adducts, still having one free amino group, can further react, yielding tetradentate salen-type Schiff base ligands. A screening over the transition metals able to show such a template effect will be presented, with particular attention to copper(II), together with their peculiar reactivity and the available crystal structure of the metal complexes and related coordination geometries.

scholarly journals Polydentate Schiff Base Ligands and Their La(III) Complexes: Synthesis, Characterization, Antibacterial, Thermal, and Electrochemical Properties

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Ali E. Şabik ◽  
Muharrem Karabörk ◽  
Gökhan Ceyhan ◽  
Mehmet Tümer ◽  
Metin Dığrak
Keyword(s):  
Antimicrobial Activity ◽  
Schiff Base ◽  
Electrochemical Properties ◽  
Antimicrobial Activities ◽  
Nitrogen Atmosphere ◽  
Spectroscopic Methods ◽  
Schiff Base Ligands ◽  
One Step ◽  
The One ◽  
Reversible Transfer

We synthesized the Schiff base ligands H2L1–H2L4 and their La(III) complexes and characterized them by the analytical and spectroscopic methods. We investigated their electrochemical and antimicrobial activity properties. The electrochemical properties of the ligands H2L1–H2L4 and their La(III) complexes were studied at the different scan rates (100 and 200 mV), different pH ranges (), and in the different solvents. The electrooxidation of the Schiff base ligands involves a reversible transfer of two electrons and two protons in solutions of pH up to 5.5, in agreement with the one-step two-electron mechanism. In solutions of pH higher than 5.5, the process of electrooxidation reaction of the Schiff base ligands and their La(III) complexes follows an ECi mechanism. The antimicrobial activities of the ligands and their complexes were studied. The thermal properties of the metal complexes were studied under nitrogen atmosphere in the range of temperature 20–1000°C.

Synthesis, Characterization, and Antibacterial and Cytotoxic Study of Metal Complexes with Schiff Base Ligands

2008 ◽  
Vol 61 (4) ◽  
pp. 288 ◽  
Author(s):  
Lei Shi ◽  
Rui-Qin Fang ◽  
Jia-Yu Xue ◽  
Zhu-Ping Xiao ◽  
Shu-Hua Tan ◽  
...  
Keyword(s):  
Schiff Base ◽  
Metal Complexes ◽  
Cytotoxic Activity ◽  
Cell Line ◽  
Primary Amines ◽  
Tumour Cell Line ◽  
Cytotoxic Activities ◽  
Ionization Mass ◽  
Schiff Base Ligands

The synthesis of 16 metal complexes from four Schiff bases prepared from 5-chloro-2-hydroxybenzaldehyde and primary amines has been described. The synthesized Schiff base ligands and their complexes were characterized by elemental analyses, spectroscopic (UV, IR, 1H and 13C NMR, electrospray ionization-mass spectrometry) methods, and magnetic and conductance measurements. Furthermore, complexes 1a, 1b, 3d, 4a, and 4d were characterized by X-ray diffraction analysis. After the structural characterization, all the compounds were tested in vitro for their antibacterial (Bacillus subtilis, Escherichia coli, Pseudomonas fluorescens, and Staphylococcus aureus) activities. The cytotoxic activities of the synthesized compounds were evaluated in vitro against human chronic myeloid leukaemia cells (K562) and a human nasopharyngeal epidermoid tumour cell line. The results indicated that most of the complexes showed good cytotoxic activity against human cancer cell lines but weak cytotoxic activity against a human normal cell line (L02). Among the compounds tested, the cobalt complexes 1a, 2a, 3a, and 4a showed the most favourable antibacterial and cytotoxic activities.

Solvent-Free Synthesis and Characterization of the Zn(II) Complexes with Amino Acid Schiff Base

2012 ◽  
Vol 455-456 ◽  
pp. 740-745
Author(s):  
W. Zhong ◽  
Guo Qing Zhong ◽  
Y. Zhang ◽  
Q. Zhong
Keyword(s):  
Schiff Base ◽  
Amino Acid ◽  
Zinc Ion ◽  
Solvent Free ◽  
Schiff Base Ligands ◽  
Coordination Numbers ◽  
Percentage Mass Loss ◽  
One Step ◽  
The One ◽  
Amino Acid Schiff Base

Three zinc (II) complexes of the amino acid Schiff base were synthesized by the one step reaction of amino acid with aldehyde, zinc acetate in solvent-free. The compositions and structures of the complexes were characterized by elemental analyses, FTIR, XRD, TG-DSC. The compositions of the complexes are ZnL•nH2O (L = sal-leu, sal-ala, van-leu; sal = salicylaldehyde; van = vanillic aldehyde; leu = leucine; ala = alanine). Infrared spectra of the complexes indicate that the Schiff base ligands are formed, zinc ion is coordinated to the Schiff base ligands as terdentate with O, O and N donors from carboxylic, phenolic and imino groups respectively, the coordination numbers of zinc ion is four. The possible pyrolysis reactions in the thermal decomposition process of the complexes, the experimental and calculated percentage mass loss are also given.

scholarly journals Ten-Coordinate Lanthanide [Ln(HL)(L)] Complexes (Ln = Dy, Ho, Er, Tb) with Pentadentate N3O2-Type Schiff-Base Ligands: Synthesis, Structure and Magnetism

2020 ◽  
Vol 6 (4) ◽  
pp. 60 ◽  
Author(s):  
Tamara A. Bazhenova ◽  
Ilya A. Yakushev ◽  
Konstantin A. Lyssenko ◽  
Olga V. Maximova ◽  
Vladimir S. Mironov ◽  
...  
Keyword(s):  
Schiff Base ◽  
Single Molecule ◽  
Magnetic Measurements ◽  
Magnetic Behavior ◽  
Molecular Structures ◽  
Magnetic Characteristics ◽  
Terbium Complex ◽  
Schiff Base Ligands ◽  
The Difference ◽  
Lanthanide Salts

A series of five neutral mononuclear lanthanide complexes [Ln(HL)(L)] (Ln = Dy3+, Ho3+ Er3+ and Tb3+) with rigid pentadentate N3O2-type Schiff base ligands, H2LH (1-Dy, 3-Ho, 4-Er and 6-Tb complexes) or H2LOCH3, (2-Dy complex) has been synthesized by reaction of two equivalents of 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))dibenzohydrazine (H2LH, [H2DAPBH]) or 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))di-4-methoxybenzohydrazine (H2LOCH3, [H2DAPMBH]) with common lanthanide salts. The terbium complex [Tb(LH)(NO3)(H2O)2](DME)2 (5-Tb) with one ligand H2LH was also obtained and characterized. Single crystal X-ray analysis shows that complexes 1–4 have the composition {[Ln3+(HL)−(L)2−] solv} and similar molecular structures. In all the compounds, the central Ln3+ ion is chelated by two interlocked pentadentate ligands resulting in the coordination number of ten. Each lanthanide ion is coordinated by six nitrogen atoms and four oxygen atoms of the two N3O2 chelating groups forming together a distorted bicapped square antiprismatic polyhedron N6O4 with two capping pyridyl N atoms in the apical positions. The ac magnetic measurements reveal field-induced single-molecule magnet (SMM) behavior of the two dysprosium complexes (with barriers of Ueff = 29 K at 800 Oe in 1-Dy and Ueff = 70 K at 300 Oe in 2-Dy) and erbium complex (Ueff = 87 K at 1500 Oe in 4-Er); complex 3-Ho with a non-Kramers Ho3+ ion is SMM-silent. Although 2-Dy differs from 1-Dy only by a distant methoxy-group in the phenyl ring of the ligand, their dynamic magnetic properties are markedly different. This feature can be due to the difference in long-range contributions (beyond the first coordination sphere) to the crystal-field (CF) potential of 4f electrons of Dy3+ ion that affects magnetic characteristics of the ground and excited CF states. Magnetic behavior and the electronic structure of Ln3+ ions of 1–4 complexes are analyzed in terms of CF calculations.

Use of a Lyophilized Reference Plasma to Compare Coagulation Test Procedures

1975 ◽  
Vol 34 (02) ◽  
pp. 426-444 ◽  
Author(s):  
J Kahan ◽  
I Nohén
Keyword(s):  
Oral Anticoagulant Therapy ◽  
Repeated Measurements ◽  
Test Procedures ◽  
Coagulation Activity ◽  
Close Relationship ◽  
Measured Activity ◽  
Test Materials ◽  
The Difference ◽  
The Stability ◽  
The One

SummaryIn 4 collaborative trials, involving a varying number of hospital laboratories in the Stockholm area, the coagulation activity of different test materials was estimated with the one-stage prothrombin tests routinely used in the laboratories, viz. Normotest, Simplastin-A and Thrombotest. The test materials included different batches of a lyophilized reference plasma, deep-frozen specimens of diluted and undiluted normal plasmas, and fresh and deep-frozen specimens from patients on long-term oral anticoagulant therapy.Although a close relationship was found between different methods, Simplastin-A gave consistently lower values than Normotest, the difference being proportional to the estimated activity. The discrepancy was of about the same magnitude on all the test materials, and was probably due to a divergence between the manufacturers’ procedures used to set “normal percentage activity”, as well as to a varying ratio of measured activity to plasma concentration. The extent of discrepancy may vary with the batch-to-batch variation of thromboplastin reagents.The close agreement between results obtained on different test materials suggests that the investigated reference plasma could be used to calibrate the examined thromboplastin reagents, and to compare the degree of hypocoagulability estimated by the examined PIVKA-insensitive thromboplastin reagents.The assigned coagulation activity of different batches of the reference plasma agreed closely with experimentally obtained values. The stability of supplied batches was satisfactory as judged from the reproducibility of repeated measurements. The variability of test procedures was approximately the same on different test materials.

Conductivity Studies of Schiff Base Ligands Derived from O-Phenylenediamine and Their Co(II) and Zn(II) Complexes

2015 ◽  
Vol 12 (2) ◽  
pp. 13
Author(s):  
Muhamad Faridz Osman ◽  
Karimah Kassim
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Fourier Transform ◽  
Schiff Base ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Impedance Spectroscopy ◽  
Ftir Spectroscopy ◽  
Coordination Complexes ◽  
Frequency Range ◽  
Schiff Base Ligands

The coordination complexes of Co(II) and Zn(II) with Schiff bases derived from o-phenylenediamine and substituted 2-hydroxybenzaldehyde were prepared All compounds were characterized by Fourier transform infrared (FTIR) spectroscopy and Nuclear magnetic resonance (NMR) spectroscopy elemental analyzers. They were analyzed using impedance spectroscopy in the frequency range of 100Hz-1 MHz. LI and L2 showed higher conductivity compared to their metal complexes, which had values of 1.3 7 x 10-7 and 6.13 x 10-8 S/cm respectively. 

Tetranuclear Copper and Mononuclear Nickel Complex of the Schiff Base of (3Z)-3-Hydrazonobutan-2-One Oxime with Different Aromatic Carbonyl Compounds: Synthesis, Single Crystal X-Ray Structure, Catecholase Activity, Phenoxazinone Synthase Activity, Catalytic Study for the Homocoupling of Benzyl Amines

2019 ◽  
Author(s):  
Swaraj Sengupta ◽  
Sahanwaj Khan ◽  
Shyamal K. Chattopadhyay ◽  
Indrani Banerjee ◽  
Tarun K. Panda ◽  
...  
Keyword(s):  
Schiff Base ◽  
Single Crystal ◽  
Copper Complex ◽  
Carbonyl Compounds ◽  
Nickel Complex ◽  
Schiff Base Ligands ◽  
X Ray ◽  
Phenoxazinone Synthase ◽  
Catecholase Activity ◽  
Aromatic Carbonyl Compounds

Synthesis and characterisation of one trinuclear copper complex, ([Cu<sub>3</sub>L<sub>3</sub>O]ClO<sub>4</sub>) (<b>1</b>) and one nickel complex ([Ni(L'H)<sub>2</sub>(dmso)<sub>2</sub>](ClO<sub>4</sub>)<sub>2</sub>) (<b>2</b>) with Schiff base ligands: (3Z)-3-((Z)-(1-(thiophen-2-yl)ethylidene)hydrazono)butan-2-one oxime (LH) and 1-(pyridin-2-yl)ethylidene)hydrazono)butan-2-one oxime (L<sup>'</sup>H). <b>1</b> shows high catecholase activity and has also been tested as a catalyst for the synthesis of benzylimine. <b>2 </b> shows phenoxazinone synthase activity.

The Demand For Money in Pakistan: Reply (Notes and Comments)

1975 ◽  
Vol 14 (3) ◽  
pp. 370-375
Author(s):  
M. A. Akhtar
Keyword(s):  
Interest Rates ◽  
Money Demand ◽  
Strong Support ◽  
Physical Capital ◽  
Careful Examination ◽  
Demand For Money ◽  
Weak Support ◽  
Complementarity Hypothesis ◽  
The Difference ◽  
The One

I am grateful to Abe, Fry, Min, Vongvipanond, and Yu (hereafter re¬ferred to as AFMVY) [1] for obliging me to reconsider my article [2] on the demand for money in Pakistan. Upon careful examination, I find that the AFMVY results are, in parts, misleading and that, on the whole, they add very little to those provided in my study. Nevertheless, the present exercise as well as the one by AFMVY is useful in that it furnishes us with an opportunity to view some of the fundamental problems involved in an empi¬rical analysis of the demand for money function in Pakistan. Based on their elaborate critique, AFMVY reformulate the two hypo¬theses—the substitution hypothesis and the complementarity hypothesis— underlying my study and provide us with some alternative estimates of the demand for money in Pakistan. Briefly their results, like those in my study, indicate that income and interest rates are important in deter¬mining the demand for money. However, unlike my results, they also suggest that the price variable is a highly significant determinant of the money demand function. Furthermore, while I found only a weak support for the complementarity between money demand and physical capital, the results obtained by AFMVY appear to yield a strong support for that rela¬tionship.1 The difference in results is only a natural consequence of alter¬native specifications of the theory and, therefore, I propose to devote most of this reply to the criticisms raised by AFMVY and the resulting reformulation of the two mypotheses.

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