In a generic synthesis approach, all three CsPbX3 (X=Cl, Br and I) perovskite nanocrystals having near unity quantum yields is reported. This has been achieved by injecting the desired amount of ...preformed alkylammonium halide salts which acted as a dual source providing halide ions and the capping agent to an equimolar amount of non‐halide Pb and Cs precursors in a reaction flask at an optimized reaction temperature. The composition sensitivity of Pb to Cs ratio, high temperature reaction, and injection of ammonium halide remained the key parameters for obtaining the high quantum yields. Details of the reaction process, use of different reagents and setting up the reaction parameters are reported.
Three colors: A rational synthesis of CsPbX3 (X=Cl, Br, and I) nanocrystals gives all three perovskites with near unity photoluminescence quantum yield. Careful analysis of the reaction chemistry and the parameters allows a generic reaction to be developed.
We report here the synthesis and structural characterization of a new class of homoleptic terpyridine complexes of Ru(II) containing styrylbenzene moieties to improve room-temperature luminescence ...properties. Solid-state structure determination of 2 was done through single-crystal X-ray diffraction. Tuning of photophysical properties was done by incorporating both electron-donating and electron-withdrawing substituents in the ligand. The complexes exhibit strong emission having lifetimes in the range of 10.0–158.5 ns, dependent on the substituent and the solvent. Good correlations were also observed between Hammett σp parameters with the lifetimes of the complexes. Styrylbenzene moieties in the complexes induce trans–trans to trans–cis isomerization accompanied by huge alteration of their spectral profiles upon treating with UV light. Reversal of trans–cis to trans–trans forms was also achieved on interacting with visible light. Change from trans–trans to the corresponding trans–cis form leads to emission quenching, whereas trans–cis to the corresponding trans–trans form leads to restoration of emission. In essence, “on–off” and “off–on” photoswitching of luminescence was observed. Calculations involving density functional theory (DFT) and time-dependent-DFT methods were performed to understand the electronic structures as well as for appropriate assignment of the absorption and emission bands.
•DFT study on the mechanism of Co(III)-catalysed 3+3 annulations.•Regioselectivity of Co(III) for ligand insertion into Co-C bond.•Energetic Span Model reveals the TDTS of the path.•Effect of level ...of theory on the global activation energy barrier.•Effect of various substituents on various step of reaction.
C-H annulation of anilide with benzylallene under the catalysis of Co(III)-complex has been studied theoretically by employing density functional theory (DFT) to find out the plausible mechanistic path. Our findings reveal that the C-H activation prefers the formation of a four-membered cobalta benzoazetidine intermediate rather than six-membered 1,2,4-cobalta benzoxazine intermediate to generate the product. This fact reveals a new mechanism in contrast to the mechanism proposed earlier. The metal mediated annulation of various anilides include six steps - coordination of substrate with catalyst, N-H metalation, C-H metalation, insertion of benzylallene, proton abstraction and migration insertion. Moreover, it reveals regioselectivity of cobalt for allene insertion. The effect of substituents on the mechanism has also been studied and the high energetic span obtained for this catalytic cycle implies that very high temperature is required for this reaction. It is consistent with the experimental result.
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In a generic synthesis approach, all three CsPbX
(X=Cl, Br and I) perovskite nanocrystals having near unity quantum yields is reported. This has been achieved by injecting the desired amount of ...preformed alkylammonium halide salts which acted as a dual source providing halide ions and the capping agent to an equimolar amount of non-halide Pb and Cs precursors in a reaction flask at an optimized reaction temperature. The composition sensitivity of Pb to Cs ratio, high temperature reaction, and injection of ammonium halide remained the key parameters for obtaining the high quantum yields. Details of the reaction process, use of different reagents and setting up the reaction parameters are reported.
In this paper, the mechanistic studies on the isomerization of hydroxyl and silyl derivatives of bicyclic cyclopropanes under the catalytic action of Zeise’s salt have been reported. The catalytic ...activity of both the monomeric and the dimeric forms of Zeise’s salt has been studied by applying the high-level quantum mechanical method. Results from this investigation reveal that the reaction goes favorably under the catalysis of the dimeric form of Zeise’s salt. The calculated activation barrier for the catalytic process using Zeise’s dimer reveals that the rearrangement occurs with an activation barrier of 19–25 kcal mol–1. Depending on the nature of substituents present on the substrate, formation of various products has been explained. This study also includes the heteronuclear counter part of Zeise’s dimer where one of the Pt-metals is replaced by palladium (Pd) and nickel (Ni) successively. The calculated activation barrier using these heteronuclear catalysts is found to be close enough to that calculated for the catalytic pathway using Zeise’s dimer.
In a generic synthesis approach, all three CsPbX3 (X=Cl, Br and I) perovskite nanocrystals having near unity quantum yields is reported. This has been achieved by injecting the desired amount of ...preformed alkylammonium halide salts which acted as a dual source providing halide ions and the capping agent to an equimolar amount of non‐halide Pb and Cs precursors in a reaction flask at an optimized reaction temperature. The composition sensitivity of Pb to Cs ratio, high temperature reaction, and injection of ammonium halide remained the key parameters for obtaining the high quantum yields. Details of the reaction process, use of different reagents and setting up the reaction parameters are reported.
Drei Farben: Eine rationale Synthese von CsPbX3‐Nanokristallen (X=Cl, Br und I) ergibt alle drei Perowskite mit einer Photolumineszenz‐Quantenausbeute nahe eins. Eine sorgfältige Analyse der Reaktion und ihrer Parameter ermöglicht die Entwicklung einer allgemeingültigen Synthesemethode.
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•Experimental and theoretical study on photoisomerization and aggregation behavior of Ru(II)-terpyridine complexes.•Polyaromatic and heteroaromatic moieties increase the emission ...characteristics via aggregation.•On-off and off-on emission switching is viable upon shining alternatively with visible and UV light.•Decrease in rate constant and quantum yield of photoisomerization with an increase in extent of aggregation.•DFT and TDDFT calculations are performed to interpret experimental spectral bands.
An array of styrylphenyl-conjugated Ru(II)-terpyridine complexes have been designed and detailed investigation of their photophysical and electrochemical characteristics have been carried off. The compounds by virtue of the presence of polyaromatic units exhibit both aggregation-induced emission quenching and enhancement. Styrylphenyl units allow the trans–trans to trans–cis photoisomerization in the free- as well as aggregated form of the complexes upon irradiation with visible light which can be reverted back by shining with UV light. Hence, “on–off” and “off–on” switching of emission occurs upon consecutive treatment of complexes with different light sources. The rate constant and quantum yield of photoisomerization in both free and aggregated forms have been calculated and is found to decrease upon increase in extent of aggregation. Theoretical analysis through density functional theory (DFT) and time-dependent DFT methods was also carried out for appropriate band assignment and to have some insight for the occurrence of photoisomerization process.
Stilbene-appended polyaromatic terpyridine systems display both blue-shifted emission enhancement and red-shifted emission quenching upon aggregation. The free as well as aggregated forms undergo ...trans → cis isomerization upon treating with visible light with significant alteration in their spectral behaviors and act as ‘on-off’ and ‘off-on’ emission switches upon successive exposure to light and keeping in the dark.
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•We designed in this work a new series of stilbene-appended terpyridine systems covalently coupled with anthracene, naphthalene and pyrene moieties which can exhibit multiple yet controllable photo-switching behaviors under divergent conditions.•Upon aggregation, these emissive compounds display either remarkable blue-shifted emission enhancement or emission quenching with red-shift, depending upon the nature of solvent.•Both free- as well as aggregated forms of the compounds undergo trans → cis isomerization upon treating with visible light, accompanied with significant alteration in their spectral behaviors. The reverse cis → trans process is also achieved on keeping the photolyzed solutions in dark. Hence, ‘on-off’ and ‘off-on’ emission switching is feasible upon successive exposure to light and keeping in dark.•A gradual decrease in rate constant and quantum yield of photoisomerization was observed with increase in extent of aggregation.•DFT and TD-DFT calculations are also carried out to interpret experimental spectral bands of the compounds.
We designed in this work a new series of stilbene-appended terpyridine systems covalently coupled with anthracene, naphthalene and pyrene moieties which can exhibit multiple yet controllable photo-switching behaviors under divergent conditions. Upon aggregation, these emissive compounds display either remarkable blue-shifted emission enhancement or emission quenching with red-shift, depending upon the nature of solvent. Both free- as well as aggregated forms of the compounds undergo trans → cis isomerization upon treating with visible light, accompanied with significant alteration in their spectral behaviors. The reverse cis → trans process is achieved on keeping the photolyzed solutions in dark. Hence, ‘on-off’ and ‘off-on’ emission switching is feasible upon successive exposure to light and keeping in dark. A gradual decrease in rate constant and quantum yield of photoisomerisation was observed with increase in extent of aggregation. Additionally, DFT and TD-DFT calculations are also carried out to interpret experimental spectral bands of the compounds.
Ru(II) complexes comprising of a stilbene appended terpyridine motif and a pyridyl‐bis‐benzimidazole unit were utilized to mimic multiple Boolean and Fuzzy logic operations. Two imidazole NH motifs ...in the outer sphere of the complexes can lead to substantial variation of their spectral characteristics upon interaction with anions. We previously demonstrated that reversible trans‐cis isomerization of the complexes upon UV light irradiation gives rise to substantial alteration in their absorption and emission spectral profiles. Here, the major objective is to mimic multiple Boolean logic operations (NOR and IMPLICATION gates) as well as complicated functions of key‐pad lock, half‐subtractor and traffic signal by using the spectral responses of the complexes upon the action of light, acid and a set of anionic inputs. Fuzzy logic is also implemented to fabricate an infinite‐valued logic system based on their spectral outputs upon the action of multiple inputs.
Ru(II)‐terpyridine complexes possessing stilbene and bis‐benzimidazolyl‐pyridine units mimic multiple advanced Boolean and Fuzzy logic functions by using their spectral responses upon the action of light, acid and selected anions.
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