Bharat K. Sharma

Synthesis, photophysical and electrochemical studies of acridone-amine based donor–acceptors for hole transport materials

A series of new donor–acceptor molecules based on acridone-amine containing four aryl substituted 2,7-diaminoacridones (1–4) and morpholine substituted acridone compounds (5) were synthesized in good yields using palladium catalysed Buchwald–Hartwig C–N amination. Their absorption, photoluminescence and electrochemical properties were investigated in solution and in thin films. Photophysical properties were found to be affected by the electron donating capability of the substituents on the diaryl amines. Absorption showed intramolecular charge transfer transitions (ICT) in a range of 447–479 nm. These acridone amine derivatives emit in the green region (500–527 nm). Reversible oxidation waves were observed for compounds 1–5 in cyclic voltammetry. The HOMO (−4.95 to −5.11 eV) and LUMO (−2.36 to −2.56 eV) energy levels of 1–5 were calculated. The EHOMO for compounds 1–5 are similar with the most widely used hole transporting materials NPD, TPD and spiro-OMe-TAD. Hence we believe that these compounds have the potential to be used as hole transporting materials in optoelectronic devices.

Synthesis, Photophysical, Electrochemical and Thermal Studies of Triarylamines based on benzo[g]quinoxalines

AbstractA series of novel dipolar and nonplanar compounds featuring electron acceptor benzo[g]quinoxaline and various electron donor triarylamine units have been synthesized in good yields and fully characterized. The photophysical, electrochemical and thermal properties of the synthesized compounds are described. The photoluminescence properties of the synthesized molecules are influenced by peripheral amines. The derivatives have high Stokes shifts, low band gap and the Commission Internationale de l’Eclairage (CIE) coordinates are positioned in the green–yellow region of the chromaticity diagram. The ionization potentials and electron affinity were found to be in the range of 5.11–5.60 eV and 2.77–2.93 eV and are comparable to the commonly used hole transporters. Thermal studies also reveal that these synthesized molecules have good thermal stability with 5% and 10% weight loss temperature ranging from 200 to 355°C and 268 to 442°C, respectively. Graphical AbstractThe absorption, emission, electrochemical and thermal properties of the synthesized materials is significantly influenced by the nature of peripheral amine segments attached to the benzo[g]quinoxaline segment. Ionization potential and electron affinity of the synthesized molecules are comparable to most commonly used hole transporting materials with good thermal stability.

Synthesis and optoelectronic investigations of triarylamines based on naphtho[2,3-f]quinoxaline-7,12-dione core as donor–acceptors for n-type materials

In this work, we have synthesized a new series of donor–acceptor system (2–7) involving electron donor triarylamines and electron acceptor naphtho[2,3-f]quinoxaline-7,12-dione by employing palladium catalyzed C–N bond forming amination reaction in good yields and fully characterized. Absorption spectra of all the synthesized molecules showed an intramolecular charge transfer (ICT) transitions in the range of 405–561 nm. Electrochemical properties of the compounds were studied by cyclic voltammetry and differential pulse voltammetry. The HOMO and LUMO energy levels of 2–7 are in the range of −4.88 to −5.57 eV and −3.37 to −3.48 eV respectively. Low-lying LUMO energy levels of 2–7 are comparable to well-known electron transporter materials and make them potential candidates as n-type semiconducting materials.

Novel electroluminescent donor–acceptors based on dibenzo[a,c]phenazine as hole-transporting materials for organic electronics

A series of novel donor–acceptor type of molecules (2–6) based on dibenzo[a,c]phenazine were synthesized by employing a palladium = catalyzed C–N bond forming amination reaction in a good yield and were then fully characterized, whereby the optical properties of 2–6 were determined by UV-vis absorption, fluorescence spectroscopy, and the electrochemical properties by cyclic voltammetry. The absorption spectra of 2–6 showed intramolecular charge transfer (ICT) transitions in the range of 447–513 nm in solution. The HOMO and LUMO energy levels of 2–6 were in the range from −5.03 to −5.29 eV and −2.75 to −2.87 eV, respectively, with an electrochemical band gap within 2.26–2.45 eV. The HOMO energy levels of 2–6 are comparable with those of the most commonly used hole-transporting materials, which makes them potential candidates for hole-transporting materials in organic electronics.

Synthesis and opto-electrochemical properties of tribenzo[a,c,i]phenazine derivatives for hole transport materials

In this work, five novel 3,6-disubstituted-tribenzo[a,c,i]phenazine (2–6) derivatives were synthesized in good yield by employing a palladium catalyzed C–N bond forming amination reaction and fully characterized. Photophysical properties of 2–6 were studied both in solvent and neat solid film by UV-vis absorption, fluorescence spectroscopy and electrochemical properties by cyclic voltammetry. Absorption spectra of 2–6 showed intramolecular charge transfer (ICT) transitions in the range of 460–512 nm in solution. The HOMO and LUMO energy levels of 2–6 are in the range of −5.18 to −5.35 eV and −3.06 to −3.17 eV respectively with electrochemical bandgap within the range of 2.12–2.29 eV. HOMO energy levels of 2–6 are comparable with most commonly used hole transporting materials such as TPD, α-NPD and spiro-OMe-TAD etc. and thus make them potential candidates for the hole transporting material in organic electronics.

Synthesis, photophysical, electrochemical and thermal investigation of Triarylamines based on 9H-Xanthen-9-one: Yellow–green fluorescent materials

AbstractTriarylamines containing 9 H−Xanthen −9−one core and aromatic units such as phenyl, naphthyl and p −methoxyphenyl were synthesized by employing palladium catalyzed C −N bond forming amination reaction in good yields. The photophysical studies revealed that the absorption and emission spectra are influenced by the nature of the peripheral amines. The photoemission spectra can be readily tuned in the range 483–532 nm (solution) and 525–576 nm (film) displaying green or yellow emission (film) depending on the nature of the amine segment with optical band gaps in the range 2.52–2.75 eV (film). The ionization potential and electron affinity were found to be in the range 5.332–5.686 eV and 2.705–2.776 eV, respectively. Thermal studies revealed that the synthesized compounds have good thermal stability with 5% and 10% weight loss at temperature ranging from 260–330∘C and 340–370∘C, respectively. Graphical AbstractThe triarylamines containing 9H-Xanthen-9-one were synthesized via palladium-catalyzed C−N bond forming reaction in good yields. The absorption, emission, electrochemical and thermal properties of the dyes were studied and found to be significantly influenced by the nature of the peripheral amine segments attached to the xanthone core.

Electron-deficient molecules: photophysical, electrochemical, and thermal investigations of naphtho[2,3-f]quinoxaline-7,12-dione derivatives

In this work, we have prepared a series of 2,3-disubstituted naphtho[2,3-f]quinoxaline-7,12-dione derivatives by condensing 1,2-diaminoanthraquinone and various benzil compounds in glacial acetic acid with excellent yield and fully characterized. Optical properties of the synthesized compounds were studied in solvents of varying polarity and thin solid film. Electrochemical properties of the compounds were studied by the cyclic voltammetry. The ionization potentials (HOMO) and electron affinity (LUMO) were found to be in the range of −6.364 to −6.644 eV and −3.247 to −3.511 eV, respectively. Thermal investigations were carried out by thermogravimetric analysis and differential scanning calorimetry.

Synthesis, Spectral, Electrochemical and Theoretical Investigation of indolo[2,3-b]quinoxaline dyes derived from Anthraquinone for n–type materials

AbstractA series of five novel dyes based on indolo[2,3-b]quinoxaline skeleton, derived from anthraquinone, have been synthesized through cyclo-condensation reaction in good yield. The photophysical, electrochemical and thermal properties along with computed HOMO-LUMO energy levels were studied for the synthesized compounds. Their absorption and photoluminescence properties were investigated in various solvents and in neat solid film and found to possess characteristic electronic absorption and emission spectra which strongly depend on the nature of solvents used. Compounds show intramolecular charge transfer transitions (ICT) in the range of 501–561 nm with high molar absorption coefficient (ε). These indoloquinoxaline derivatives emit in the range of 580–648 nm in solutions and 672–700 nm (red region) in neat solid films. Electrochemical data indicate that the dyes possess relatively low–lying LUMO levels in the range −3.29 to −3.43 eV. The thermal stability observed for these compounds suggests their use under ambient conditions. The in–built donor–acceptor architecture and HOMO–LUMO energies were further rationalized using DFT calculations. This study suggests that these compounds have potential to be used as n–type materials for optoelectronic devices. Graphical AbstractA series of five new donor–acceptor based indolo[2,3-b]quinoxaline dyes, derived from anthraquinone, have been synthesized, characterized and their optoelectronic properties studied. The donor‒acceptor architecture and observed orbital energies were rationalized using DFT calculations. The low lying LUMO energy levels and other results suggest that these molecules have potential to be used as n–type materials in organic electronic devices.