RESUMEN
Three L-Tryptophan based chiral Schiff bases namely, 2-((5-chloro-2-hydroxybenzylidene)amino)-3-(1H-indol-3-yl)propanoic acid (i), 2-((5-bromo-2-hydroxybenzylidene)amino)-3-(1H-indol-3-yl) propanoic acid (ii) and 2-((2-hydroxy-5-iodobenzylidene)amino)-3-(1H-indol-3-yl)propanoic acid (iii) were synthesized and their corrosion inhibition behaviour on corrosion of carbon steel in 1 M hydrochloric acid (HCl) solution was investigated by means of weight loss and electrochemical techniques. The inhibitory action of Schiff bases was found to be mixed-type, it's adsorption on carbon steel surface obeys the Langmuir adsorption isotherm and involves both physisorption and chemisorption mechanisms. Quantum chemical calculations predicted an inhibition order of iii > ii > i, is in good agreement with the experimental order. The impact of halide substitution on Schiff bases towards its anti-corrosion ability was explored.
RESUMEN
In this work boehmite was used as an acid-base bifunctional catalyst for aldol condensation reactions of aromatic aldehydes and ketones. The catalyst was prepared by simple sol-gel method using Al(NO3)3·9H2O and NH4OH as precursors. The catalyst has been characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), UV-visible spectroscopy (DRS), BET surface area analyses. Boehmite is successfully applied as catalyst for the condensation reaction between 4-nitrobenzaldehyde and acetone as a model substrate giving α, ß-unsaturated ketones without any side product. The scope of the reaction is extended for various substituted aldehydes. A probable mechanism has been suggested to explain the cooperative behavior of the acidic and basic sites. The catalyst is environmentally friendly and easily recovered from the reaction mixture. Also the catalyst is reusable up to 3 catalytic cycles.
RESUMEN
A crystalline supramolecular photocatalyst is prepared through metal-induced self-assembly of perylene diimide with imidazole groups at the imide position (PDI-Hm). Exploiting the metal-coordination ability of imidazole, a crystalline assembly of copper-coordinated PDI-Hm (CuPDI-Hm) in a nanorod shape is prepared which displays an outstanding photocatalytic oxygen evolution rate of 25,900â µmol g-1 h-1 without additional co-catalysts. The imidazole-copper coordination, along with π-π stacking of PDI frameworks, guides the arrangement of PDI-Hm molecules to form highly crystalline assemblies. The coordination of copper also modulates the size of the CuPDI-Hm supramolecular assembly by regulating the nucleation and growth processes. Furthermore, the imidazole-copper coordination constructs the electric field within the PDI-Hm assembly, hindering the recombination of photo-induced charges to enhance the photoelectric/photocatalytic activity when compared to Cu-free PDI-Hm assemblies. Small CuPDI-Hm assembly exhibits higher photocatalytic activity due to their larger surface area and reduced light scattering. Together, the Cu-imidazole coordination presents a facile way for fabricating size-controlled crystalline PDI assemblies with built-in electric field enhancing photoelectric and photocatalytic activities substantially.
RESUMEN
Selective detection and determination of silver ions are tricky due to the poor reactivity and the interference of various metal ions and halides. Only a few cases have been reported concerning sulfur-based functionality. This work proposes silver-selective probes exhibiting peculiar colorimetric and photothermal responses without the need for sulfur-functional groups. Tetrakis(4-dialklyaminophenyl)1,4-phenylenediamine containing hexyl and methoxytriethyleneglycol substituents, PTS1 and PTS2, respectively, are selectively oxidized by silver ions to form dicationic diimmonium salts. The resulting quinone diimminium salts show strong absorption in the near-infrared (NIR) region with intense color changes. The striking color change is observed from pale brown to intense olive green with immediate responses. PTS1 shows a higher binding constant and nanomolar detection limit, whereas PTS2 shows a sub-micromolar detection limit. Job's plot studies reveal the stoichiometric ratio as 1:2 (PTS1: Ag+). Due to the strong NIR absorption of the oxidized PTS probes, the temperature rise is monitored, after adding silver ions, by a thermal camera and in-contact thermal sensors. The concentration of the actual samples can be determined based on a calibration plot with a temperature change as a function of silver ion concentration. The current results offer highly selective and ultrasensitive probes for silver ions under multiple detection mediums, including naked eye and photothermal detection.