scholarly journals NMR Structural Study of the Prototropic Equilibrium in Solution of Schiff Bases as Model Compounds

Molecules ◽  
2013 ◽  
Vol 19 (1) ◽  
pp. 459-481 ◽  
Author(s):  
David Ortegón-Reyna ◽  
Cesar Garcías-Morales ◽  
Itzia Padilla-Martínez ◽  
Efren García-Báez ◽  
Armando Aríza-Castolo ◽  
...  
Keyword(s):  
Schiff Bases ◽  
Structural Study ◽  
Model Compounds ◽  
Prototropic Equilibrium

Synthesis, characterization, structural study and antibacterial activity of the Schiff bases derived from sulfanilamides and related copper(II) complexes

2016 ◽  
Vol 453 ◽  
pp. 238-246 ◽  
Author(s):  
Mehdi Salehi ◽  
Fateme Ghasemi ◽  
Maciej Kubicki ◽  
Asadollah Asadi ◽  
Mahdi Behzad ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Schiff Bases ◽  
Structural Study

Electronic and Molecular Structures of Heteroradialenes: A Combined Synthetic, Computational, Spectroscopic, and Structural Study Identifying IR Spectroscopy as a Simple but Powerful Experimental Probe

2013 ◽  
Vol 68 (1) ◽  
pp. 64-86 ◽  
Author(s):  
Carl-Georg Freiherr von Richthofen ◽  
Bastian Feldscher ◽  
Kai-Alexander Lippert ◽  
Anja Stammler ◽  
Hartmut Bögge ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Schiff Bases ◽  
Structural Study ◽  
Electronic Structures ◽  
Molecular Structures ◽  
Resonance Structure ◽  
Hydrogen Bond Donor ◽  
Donor Acceptor ◽  
Intramolecular Hydrogen

The vicinity of a hydrogen bond donor (O-H) and a hydrogen bond acceptor (C=O or C=N- R) in salicylaldehydes and ortho-Schiff bases results in significant structural variations compared to the monosubstituted derivatives that are reflected in the electronic structure and thus in the spectroscopic properties. This interplay between intramolecular hydrogen bonding and multicenter p- electron delocalization is the origin of the concept of resonance-assisted hydrogen bonding (RAHB). Herein, the complexity is extended from one hydrogen bond donor-acceptor pair in salicylaldehyde and ortho-Schiff bases to three hydrogen bond donor-acceptor pairs in 2,4,6-tricarbonyl- and 2,4,6- triimine-substituted phloroglucinols (1,3,5-trihydroxybenzene), respectively. To evaluate the changes in the molecular and electronic structures, we have performed a comprehensive computational, spectroscopic, and structural study starting from monosubstituted benzene derivatives as references over ortho-disubstituted derivates to the sixfold-substituted derivatives. Whereas in salicylaldehydes, ortho- Schiff bases, and 2,4,6-tricarbonyl-phloroglucinols the phenolic O-protonated tautomers represent the energy minima, the N-protonated tautomers represent the energy minima in 2,4,6-triiminephloroglucinols. The analysis provides a keto-enamine resonance structure with six exocyclic double bonds to be dominant for these species reminiscent of [6]radialenes, which were termed heteroradialenes. These heteroradialenes are non-aromatic alicycles. However, the predominance of this resonance structure does not represent a sudden change going from the 2,4,6-tricarbonyl- to the 2,4,6-triimine-phloroglucinols, but a gradual increase of analogous resonance structure contributions is observed even in salicylaldehyde and ortho-Schiff bases demonstrating some hetero-orthoquinodimethane character. These changes are, besides in the molecular structures, well reflected in the IR spectra, which can therefore be used as a simple tool to probe the electronic structures in these systems. Interruption of the delocalized p system supporting the intramolecular hydrogen bond, i. e. going from 2,4,6-triimine- to 2,4,6-triamine-substituted phloroglucinols, reestablishes an O-protonated aromatic phloroglucinol system.

scholarly journals Comparison in practical applications of crown ether sensor molecules containing an acridone or an acridine unit – a study on protonation and complex formation

2021 ◽  
Author(s):  
Ádám Golcs ◽  
Panna Vezse ◽  
Bálint Árpád Ádám ◽  
Péter Huszthy ◽  
Tünde Tóth
Keyword(s):  
Strong Influence ◽  
Physicochemical Characteristics ◽  
Tautomeric Equilibrium ◽  
Model Compounds ◽  
Practical Applications ◽  
Sensor Applications ◽  
Neutral Aqueous Medium ◽  
Prototropic Equilibrium ◽  
Sensor Molecules ◽  
The Relationship

AbstractCrown ethers containing an acridone or an acridine unit are successfully applied opto- and electrochemical cation sensors. The heteroaromatic unit of these macrocycles can be in different forms during the applications, which have a strong influence on the sensing behavior. Moreover, in the case of acridono-macrocycles a prototropic equilibrium takes place upon complexation, which is effected by the physicochemical characteristics. A Pb2+-selective acridono-18-crown-6 ether and its 9-phenylacridino-analogue were used as model compounds for comparing the different forms of the heterocyclic units of these sensor molecules. Since in most practical sensor applications of the fluorescent hosts a non-neutral aqueous medium is present, studies on complexation and signaling were carried out from the aspect of the relationship among protonation, coordinating ability, complex stability and tautomeric equilibrium. A strong interdependence among these factors was found and limitations of using unsubstituted acridino- and acridono-sensor molecules in comparison with their 9-substituted-acridino-analogues were discussed. This study will hopefully serve as a useful standpoint for future development of ionophore-based sensors containing an acridone or an acridine unit.

An Ultra-Structural Study of Human Melanoma in Vivo and Vitro

1976 ◽  
Vol 34 ◽  
pp. 258-259
Author(s):  
James R. Gaylor ◽  
Fredda Schafer ◽  
Robert E. Nordquist
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Protein Aggregation ◽  
Structural Study ◽  
Human Melanoma ◽  
Protein Matrix ◽  
Early Form ◽  
Endoplasmic Reticulum Protein ◽  
Mitochondrial Origin

Several theories on the origin of the melanosome exist. These include the Golgi origin theory, in which a tyrosinase-rich protein is "packaged" by the Golgi apparatus, thus forming the early form of the melanosome. A second theory postulates a mitochondrial origin of melanosomes. Its author contends that the melanosome is a modified mitochondria which acquires melanin during its development. A third theory states that a pre-melanosome is formed in the smooth or rough endoplasmic reticulum. Protein aggregation is suggested by one author as a possible source of the melanosome. This fourth theory postulates that the melanosome originates when the protein products of several genetic loci aggregate in the cytoplasm of the melanocyte. It is this protein matrix on which the melanin is deposited. It was with these theories in mind that this project was undertaken.

Structural study of LiPO3-TeO2 glasses

1997 ◽  
Vol 222 (1-2) ◽  
pp. 131-136
Author(s):  
K Muruganandam
Keyword(s):  
Structural Study
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