Syntheses and Characterizations of Platinum Complexes with New Pyrene-based Salicylaldiminato-type Ligand Substituted at 7-Position of Pyrene

Many experimental data show that bulky substituents on the molecules enhance solubility, catalytic activity, and photophysical properties due to the prevention of π-π stacking in metal salicylaldimines. In order to understand the effect of bulkiness of substituents on the properties of the obtained molecules, the author researched and synthesized two new pyrene-based salicylaldiminato-type ligands that were substituted at 7-position and functionalized on imine group with bulky substituents. After the introduction of the tert-butyl group at 7-position of pyrene by Friedel-Crafts reaction, the syntheses of new ligands 1-hydroxy-2-[((2,6-dimethylphenyl)-imino)methyl]-7-(tert-butyl)-pyrene 3, 2-hydroxy-1- [((2,6-dimethylphenyl)imino)methyl]-7-(tert-butyl)-pyrene 4 and corresponding platinum complexes 3(Pt), 4(Pt) were performed in the different ways with the synthetic processes of the complexes 1(Pt) and 2(Pt). The new ligands and complexes were characterized by 1H NMR, IR spectroscopy, mass spectroscopy, elemental analysis and X-ray diffraction, only for 3(Pt). In addition to measurements of the absorption and emission spectra, TDDFT calculations using the B3LYP functions were also performed. The complexes 3(Pt) and 4(Pt) exhibit good solubility and red-shift in absorption and emission spectra because of tert-butyl group at 7-position of pyrene and extension of the delocalized π-orbitals to the 2,6-dimethylphenyl on imine group. The change of functional groups also induces the upfield shift of the protons affected by ring currents of phenyl groups Ar-3, Ar-4 on imine groups. Introduction of t-butyl groups in pyrene moieties can stabilize radical forms in oxidation processes.

Catechol-Containing Schiff Bases on Thiacalixarene: Synthesis, Copper (II) Recognition, and Formation of Organic-Inorganic Copper-Based Materials

For the first time, a series of catechol-containing Schiff bases, tetrasubstituted at the lower rim thiacalix[4]arene derivatives in three stereoisomeric forms, cone, partial cone, and 1,3-alternate, were synthesized. The structure of the obtained compounds was proved by modern physical methods, such as NMR, IR spectroscopy, and HRMS. Selective recognition (Kb difference by three orders of magnitude) of copper (II) cation in the series of d-metal cations (Cu2+, Ni2+, Co2+, Zn2+) was shown by UV-vis spectroscopy. Copper (II) ions are coordinated at the nitrogen atom of the imine group and the nearest oxygen atom of the catechol fragment in the thiacalixarene derivatives. High thermal stable organic-inorganic copper-based materials were obtained on the base of 1,3-alternate + Cu (II) complexes.

Silver(I)-Catalyzed Tandem Reaction of Enynones and 4-Alkynyl Isoxazoles: Regioselective Synthesis of Highly Functionalized 4H-furan[3,4-c]pyrroles

The work reports a silver(I)-catalyzed tandem reaction of enynones with 4-alkynyl isoxazoles. The reaction occurred via yne-enones bearing imine group as a key intermediate. The subsequent tandem cyclization of the...

Evaluation of the of a numder of natural and modified polysaccharides on the microviscosity of rat erythrocyte membranes using the spin probe method

Based on the pharmacokinetics of nitazole, proprietary oral administration of the rabbit analyzes various aspects of its use as auxiliary substances in the preparation of dosage forms with controlled absorption of starch, carboxymethyl starch, dialdehyde starch, sodium alginate and chitosan. Our analysis of pharmacokinetic curves revealed a correlation between the presence and magnitude of the negative charge in the polymer of starch derivatives and an increase in the bioavailability of nitazole, the absorption rate estimated by tmax and from the equations describing the curves in the framework of the single-particle absorption model. It can be assumed that the change in the bioavailability of nitazole in the presence of starch derivatives is associated with the ion-ion or ion-dipole interaction of the positively charged imine group of nitazole and negatively charged groups of starch derivatives. Obviously, in the mechanism of absorption of nitazole, the limiting stage is the stage of dissolution of nitazole in the stomach.Since the absorption of nitazole may also depend on the microviscosity of the membranes of the cells of the walls of the stomach, the effect of the above polysaccharides on the microviscosity of the membranes of red blood cells as model cells has been studied. However, the work revealed a noticeable effect of only chitosan on the microviscosity of erythrocyte membranes, in which there was some immobilization of the conformational mobility of the lipid bilayer of the cell membranes upon binding of the oppositely charged chitosan to the surface of the erythrocyte membranes. The remaining negatively charged polysaccharides did not significantly affect the microviscosity of the membranes, apparently due to the processes of electrostatic repulsion from red blood cell cells. The totality of the data obtained has expanded our knowledge about the mechanisms of the possible effect of high molecular weight polysaccharides on the bioavailability of various drugs when creating drugs with controlled absorption.

One-Component Urethane Sealants Synthesis

It is proposed to synthesize one-component light-resistant urethane compositions using aldimines as crosslinking agents and methyl iodide as an activating agent to obtain sealants. The effect of the methyl iodide activator and the quaternized complex of the imine group and temperature on the cure time of the sealants was investigated. The influence of the polyether molecular weight and the structure of aldimines fillers on the physical and mechanical properties of the obtained sealants was studied.

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

A number of p-pyridinyl oxime carbamate derivatives were prepared upon the reaction of the corresponding oximes with isocyanates. These novel compounds reacted photochemically in the presence of supercoiled plasmid DNA. Structure–activity relationship (SAR) studies revealed that the substituent on the imine group was not affecting the extend of the DNA damage, whereas the substituent of the carbamate group was critical, with the halogenated derivatives to be able to cause extensive single and double stranded DNA cleavages, acting as “synthetic nucleases”, independently of oxygen and pH. Calf thymus–DNA affinity studies showed a good-to-excellent affinity of selected both active and non-active derivatives. Preliminary theoretical studies were performed, in an effort to explain the reasons why some derivatives cause photocleavage and some others not, which were experimentally verified using triplet state activators and quenchers. These theoretical studies seem to allow the prediction of the activity of derivatives able to pass intersystem crossing to their triplet energy state and thus create radicals able to damage DNA. With this study, it is shown that oxime carbamate derivatives have the potential to act as novel effective photobase generating DNA-photocleavers, and are proposed as new leads for “on demand” biotechnological applications in drug discovery and medicine.

Synthesis of unsymmetrical 1,8-naphthyridine-based ligands for the assembly of tri-and tetra-nuclear copper(ii) complexes

Exploring copper(ii) coordination from a new unsymmetrical naphthyridine-based ligand leads to the preparation of tetranuclear and trinuclear complexes. During the complexation, one imine group is oxidized to an amide group.

Green Synthesis of new heterocyclic hydrazones, spectroscopic characterization

The present project analyses the synthesis of three hydrazones with new structures by Green Chemistry, for its later spectroscopic characterization. Hydrazones are organic compounds with interesting properties, such as being solids with specific melting points and colors depending on their structure. Hydrazones and substituted derivatives are a group of versatile compounds and leading molecules because they are potential bioactive agents with an ample spectrum of pharmacological activities. It is important to note that these properties are a consequence of the presence of the imine group that possess high electronic density. The objective is the synthesis of heterocyclic hydrazones derived from furan and thiophencarbaldehyde with novel structures that allow the synthesis of optimized compounds with biomedical applications. Synthesis, purification and characterization of organic compounds was designed to combat illnesses with maximum positive effects and minimum toxicity, in order to evaluate their activity in specific cell lines.

Cinnamaldehyde-loaded chitosan nanoparticles: characterization and antimicrobial activity

Due to its wide spectrum activity and low toxicity, chitosan has shown to be a promising molecule to be applied in food science and technology. Meanwhile, cinnamaldehyde (the main component in cinnamon flavor) has shown potential uses as a strong antimicrobial compound. To improve the antimicrobial activity of chitosan, we have prepared N-acylated chitosan nanoparticles, with cinnamaldehyde as acylating reagent. The properties of the modified material were compared against the ones of the unmodified chitosan nanoparticles. Modification of the material was characterized by means of FT-IR spectroscopy with the identification of the imine group formed due to the addition of cinnamaldehyde (soft band appearance in the range of 1630-1660 cm-1 ). Meanwhile, 1H NMR analysis was used to quantify the modification. Nanoparticles of both, the modified and the unmodified chitosan, were characterized by TEM and DLS analysis showing a higher diameter size and a reduced zeta potential for the cinnamaldehyde loaded material than the chitosan nanoparticles. Finally, their activity was tested against E. coli and L. monocytogenes by measuring the minimal inhibitory concentration, showing a greater activity when the nanoparticles were functionalized (with an observed increase of the activity with the higher loading of cinnamaldehyde). This works evidence that the N-acylated chitosan nanoparticles have promising and potential use in food preservation.