Carbazole Donor−Carbazole Linker-Based Compounds: Preparation, Photophysical Properties, and Formation of Fluorescent Nanoparticles

Abstract

A new class of highly soluble and stable compounds (1-4) has been synthesized and characterized. Compounds 1, 2, and 3 have 3,6-disubstituted carbazole as electron-donor-linked through the 2,7-positions of N-substituted carbazole with variably substituted phenyl acetylenes as electron acceptors. Compound 4 has two identical donors linked through the 2,7-position of N-substituted carbazole. These compounds absorb from UV to visible region and emit intensely from blue to green. The effect on the photophysical properties of these compounds by changing acceptors while keeping the donor and linker constant has been studied. A study of solvent effects on their photophysical properties has shown that an increase in polarity of the solvent causes a reduction of fluorescence quantum yields. With a decrease in temperature, these compounds showed increased emission intensity accompanied by a red shift of emission. Edge excitation red shift showed as much as 128 nm for compound 2 in isopropanol. Solid-state fluorescence quantum yields vary from 0.27 to 0.68 for these compounds. The fluorescence lifetimes of these compounds are solvent dependent. Compound 2 showed remarkable change in emission with concentration. Compounds 2 and 3 form highly stable fluorescent organic nanoparticles (FONs) in tetrahydrofuran/water mixtures. The general and specific solvent effect on the emission properties of these compounds are investigated by Lipert-Mataga plots. The potentiality of these compounds for use in dye-sensitized solar cells and in organic light-emitting diodes is under study in our laboratories.

Swift Electrofluorochromism of Donor–Acceptor Conjugated Polytriphenylamines

“…Such substantially enhanced and blueshifted fluorescence is attributed to the limited ICT transition in solid state. 33,34 For P(TCEC), the acetone solution shows weak emission with its PL spectrum approaching the base line, which is overlapped with the PL spectra of the mixture solution containing 10 vol% and 30 vol% of water, respectively. However, significantly increased PL intensity and little shift of PL spectra are observed when P(TCEC) gradually aggregates from the acetone solution with an increasing fraction of added water.…”

Organic nanoparticles

“…49 A new class of stable highly soluble substances, viz., donor-acceptor carbazole derivatives, was described in detail. 105 The dependences in their physicochemical properties on the change in the acceptor group was studied as well as their photophysical properties in different solvents. In tetrahydrofuran ± water mixtures, organic nanoparticles are formed with the size of *250 nm.…”

Synthesis and computational studies of diphenylamine donor-carbazole linker-based donor–acceptor compounds

“…24 N-Arylation of 12 was followed by the Sonogashira coupling with 4-ethynylbenzaldehyde to obtain 14 (Scheme 1). 25 Sonogashira coupling of 14 with 9 yielded 1, which was further reacted with malononitrile and basic aluminum oxide in toluene to produce 2. Sonogashira coupling of 9 with 13 produced the compound 3 (Scheme 2).…”

“…23 The synthetic procedures of compounds 12 and 13 are described elsewhere. 24,25 New synthetic procedures for synthesis of 1e6 and 14 are described here. 1 H and 13 C NMR spectra were recorded at 500 MHz using tetramethylsilane as the internal standard.…”