Metal-Free, One-Pot, Rapid Synthesis of Tetrahydropyridines Using Acetic Acid as Solvent and Catalyst at Room Temperature

<div><p></p><p>Acetic acid–promoted, one-pot synthesis of tetrahydropyridines has been developed under metal-catalyst-free conditions via a tandem reaction. High atom economy, good yield, simple procedure, no expensive column chromatography, shorter reaction time, and metal-free and mild reaction conditions are some of the important features of this protocol. The current methodology provides an alternative approach for not only highly substituted tetrahydropyridines (THPs) but also fully substituted tetrahydropyridines (FTHPs) in moderate to good yields. The plausible mechanism for the formation of THPs was greatly promoted by the H⁺ ion coming from acetic acid.</p> <p>[Supplementary materials are available for this article. Go to the publisher's online edition of <i>Synthetic Communications</i>® for the following free supplemental resource(s): Full experimental and spectral details.]</p> </div

(Tetrahydrodibenzo[<i>a</i>,<i>i</i>]phenanthridin-5-yl)phenol as a Fluorescent Probe for the Detection of Aniline

Two (tetrahydrodibenzo­[a,i]­phenanthridin-5-yl)­phenols that differ in their substituents at the para position (P1, R = H and P2, R = NEt2) were designed and synthesized. The presence of a −NEt2 group in probe P2 facilitates the twisted intramolecular charge transfer (TICT) process, making P2 emissive, which distinctly coordinated with boron trifluoride in the presence of different amines with different electronic properties. A substantial increase in emission intensity with increasing viscosity of the surrounding environment and smooth formation of a planar complex with boron and Zn2+ ions concluded the presence of a TICT process. The selective reactivity of P2 toward a tetracoordinated boron complex has been explored as a potential tool for colorimetric and fluorescent discrimination of aromatic primary amines, i.e., anilines. Selective detection of aniline with probe P2 can be viewed through the naked eye, and the corresponding fluorescence turn-on detection limit was found to be 12.65 nM. In addition, the detection of aniline on precoated aluminum-backed thin-layer chromatography plates and Whatman filter paper strips was found to be in good agreement with the color change of P2 in solution and in vapor phase

(Tetrahydrodibenzo[<i>a</i>,<i>i</i>]phenanthridin-5-yl)phenol as a Fluorescent Probe for the Detection of Aniline

Two (tetrahydrodibenzo­[a,i]­phenanthridin-5-yl)­phenols that differ in their substituents at the para position (P1, R = H and P2, R = NEt2) were designed and synthesized. The presence of a −NEt2 group in probe P2 facilitates the twisted intramolecular charge transfer (TICT) process, making P2 emissive, which distinctly coordinated with boron trifluoride in the presence of different amines with different electronic properties. A substantial increase in emission intensity with increasing viscosity of the surrounding environment and smooth formation of a planar complex with boron and Zn2+ ions concluded the presence of a TICT process. The selective reactivity of P2 toward a tetracoordinated boron complex has been explored as a potential tool for colorimetric and fluorescent discrimination of aromatic primary amines, i.e., anilines. Selective detection of aniline with probe P2 can be viewed through the naked eye, and the corresponding fluorescence turn-on detection limit was found to be 12.65 nM. In addition, the detection of aniline on precoated aluminum-backed thin-layer chromatography plates and Whatman filter paper strips was found to be in good agreement with the color change of P2 in solution and in vapor phase

(Tetrahydrodibenzo[<i>a</i>,<i>i</i>]phenanthridin-5-yl)phenol as a Fluorescent Probe for the Detection of Aniline

Two (tetrahydrodibenzo­[a,i]­phenanthridin-5-yl)­phenols that differ in their substituents at the para position (P1, R = H and P2, R = NEt2) were designed and synthesized. The presence of a −NEt2 group in probe P2 facilitates the twisted intramolecular charge transfer (TICT) process, making P2 emissive, which distinctly coordinated with boron trifluoride in the presence of different amines with different electronic properties. A substantial increase in emission intensity with increasing viscosity of the surrounding environment and smooth formation of a planar complex with boron and Zn2+ ions concluded the presence of a TICT process. The selective reactivity of P2 toward a tetracoordinated boron complex has been explored as a potential tool for colorimetric and fluorescent discrimination of aromatic primary amines, i.e., anilines. Selective detection of aniline with probe P2 can be viewed through the naked eye, and the corresponding fluorescence turn-on detection limit was found to be 12.65 nM. In addition, the detection of aniline on precoated aluminum-backed thin-layer chromatography plates and Whatman filter paper strips was found to be in good agreement with the color change of P2 in solution and in vapor phase

Tailoring Interfacial Physicochemical Properties in Cu₂O‑TiO₂@rGO Heterojunction: Insights from EXAFS and Electron Trap Distribution Analysis

In this study, a solution-based synthesis technique was utilized to produce Cu2O nanoparticles (NPs) on TiO2 nanofibers (TNF), which were then subsequently coated with reduced graphene oxide (rGO) nanosheets. In the absence of any cocatalyst, CTNF@rGO-3% composite displayed an ideal photocatalytic H2 evolution rate of 96 μmol g–1 h–1 under visible light irradiation, this was 10 times higher than that of pure TNF. At 420 nm, the apparent quantum efficiency of this composite reached a maximum of 7.18%. Kelvin probe force microscopy demonstrated the formation of an interfacial electric field that was oriented from CTNF to rGO and served as the driving force for interfacial electron transfer. The successful establishment of an intimate interface between CTNF@rGO facilitated the efficient transfer of charges and suppressed the rate of recombination of photogenerated electron–hole pairs, leading to a substantial enhancement in photocatalytic performance. X-ray photoelectron spectroscopy, photoluminescence spectra, and electrochemical characterization provide further confirmation that formation of a heterojunction between CTNF@rGO leads to an extension in the lifetimes of the photogenerated charge carriers. The experimental evidence suggests that a p–n heterojunction is the mechanism responsible for the significant photocatalytic activity observed in the CTNF@rGO composite during H2 evolution

Utilization of Multi-Heterodonors in Thermally Activated Delayed Fluorescence Molecules and Their High Performance Bluish-Green Organic Light-Emitting Diodes

We report a series of pentacarbazolyl-benzonitrile derivatives such as 2,4,6-tri­(9H-carbazol-9-yl)-3,5-bis­(3,6-di­(pyridin-3-yl)-9H-carbazol-9-yl)­benzonitrile (mPyBN), 3,5-bis­(3,6-bis­(4-(trifluoromethyl)­phenyl)-9H-carbazol-9-yl)-2,4,6-tri­(9H-carbazol-9-yl)­benzonitrile (pCF3BN), 2,4,6-tri­(9H-carbazol-9-yl)-3-(3,6-di­(pyridin-3-yl)-9H-carbazol-9-yl)-5-(3,6-diphenyl-9H-carbazol-9-yl)­benzonitrile (PyPhBN), 3-(3,6-bis­(4-(trifluoromethyl)­phenyl)-9H-carbazol-9-yl)-2,4,6-tri­(9H-carbazol-9-yl)-5-(3,6-di­(pyridin-3-yl)-9H-carbazol-9-yl)­benzonitrile (PyCF3BN), and 3-(3,6-bis­(4-(trifluoromethyl)­phenyl)-9H-carbazol-9-yl)-2,6-di­(9H-carbazol-9-yl)-5-(3,6-di­(pyridin-3-yl)-9H-carbazol-9-yl)-4-(9H-pyrido­[3,4-b]­indol-9-yl)­benzonitrile (CbPyCF3BN) in which some of the carbazoles are substituted with modified 3,5-diphenyl carbazoles, exhibiting thermally activated delayed fluorescence (TADF) properties. These emitters comprised two, three, and four different types of donors, capable of bluish-green emission of around 480 nm with relatively high photoluminescence quantum yields over 90% in solution. Emitters, namely, PyPhBN, PyCF3BN, and CbPyCF3BN, composed of three and four different types of donors endowed a rather short delayed lifetime (τd) of 4.25, 5.01, and 3.65 μs in their film state, respectively. Bluish-green organic light-emitting diodes based on PyPhBN, PyCF3BN, and CbPyCF3BN exhibit a high external quantum efficiency of 20.6, 19.5, and 19.6%, respectively, with unsurpassed efficiency roll-off behavior. These results indicate that the TADF properties of multidonor type molecules can be manipulated by controlling the types and number of electron donor units

Defect Passivation by Pyridine-Carbazole Molecules for Efficient and Stable Perovskite Solar Cells

The defects in the light-harvesting perovskite absorber layer play a key role in limiting power conversion efficiencies (PCEs) and long-term stability of lead halide perovskite solar cells (PSCs). Although organic ammonium halides have been used for defect passivation in high-performance PSCs, the stability issue is still a challenge. Herein, we develop a novel material of pyridine-carbazole (Py-Cz) to passivate defects via coordination bonding. With this passivation, the photoluminescence intensity of perovskite films was increased. In addition, the formation of under-coordinated Pb2+ defects in perovskite films was reduced significantly, enabling high-performance and long-term stable PSCs. Three different sets of PSCs were constructed, namely, without passivation, with phenethylammonium iodide (PEAI) (commonly used for passivation), and with Py-Cz passivation. Remarkably, the PSCs fabricated using the Py-Cz passivation not only achieved PCEs of over 20% but also retained 85% of their initial performances over more than 5000 h. In contrast, the PSCs without or with PEAI passivation degraded quickly during the long-term operational stability test under light illumination. This method opens up a new opportunity to develop highly efficient and operationally stable PSCs