Dimethoxy substituted triphenylamine based donor-acceptor fluorophores: tunable solid-state emission and reversible thermofluorochromism

A simple and eco‐friendly green protocol was used for synthesis of pyrazolopyranopyrimidines via four‐component reaction of hydrazine hydrate, ethyl acetoacetate, barbituric acid or dimethyl barbituric acid, and aromatic aldehydes under thermal and solvent‐free conditions in the presence of magnetic nanoparticle supported silica bonded n‐propyl‐4‐aza‐1‐azoniabicyclo[2.2.2]octane chloride (MNPs@DABCO+Cl−) as an efficient, recyclable heterogeneous catalyst. MNPs@DABCO+Cl− also catalyzed the synthesis of 1,6‐diamino‐2‐oxo‐1,2,3,4‐tetrahydropyridine‐3,5‐dicarbonitrile derivatives by four‐component reaction of hydrazine hydrate, malononitrile, ethyl cyanoacetate and ketones under thermal and solvent‐free conditions at 80 °C. These methods are practical and offer many advantages, such as high yields, short reaction times, and simple work‐up.

Donor-acceptor system introduces N defect modified g-C3N4 for efficient photocatalytic degradation of methylene blue under visible light

The main purpose of this research is to synthesize a series of conjugated molecules serving as an TiO2 modifier in poly(3-hexylthiophene) (P3HT)/titania (TiO2) layer heterojunction devices. By improving the charge separation and transfer between P3HT organic donor and TiO2 inorganic acceptor, the LUMO levels of interface modifiers (IMs) should be located between the LUMO levels of P3HT and conduction band of TiO2. Therefore, combining the strategies of structural design and principle of electronic structure, we developed a series of novel conjugated molecules that composed of three parts: (i) benzathiadiazole and thiophene moieties as the conjugated backbone for energy levels tuning, (ii) a hexyl chain to increase solubility, lipophilicity and inhibit π-stacking aggregation, and (iii) cyanoacetic acid as an electron-accepting and TiO2 anchoring substituents. We first utilized Kumada coupling to engineer the hexyl chain onto different positions on thiophene thus obtaining various derivative structures, and subsequently combined benzathiadiazole and thiophene moieties through Stille coupling to form conjugated molecules. Next, we performed a Vilsmeier-Haack formylation to yield an additional aldehyde group on the conjugated backbone. Finally, we introduced cyanoacetic acid by Knoevenagel condensation to form SL-series conjugated modifiers. Structural characterization of SL-series was achieved by 1H NMR, 13C NMR, elemental analysis (EA) and electron impact mass spectroscopy (EI-MS). Optical and electronic properties of these molecules were determined by UV-vis spectroscopy and cyclic voltammetry (CV). Furthermore, the contact angle of SL-series modified TiO2 on FTO film were measured by contact angle analyzer. The quenching effect on FTO/TiO2:IMs/P3HT was determined by photoluminescence measurement. Our analytical studies reveal that the UV-vis spectra exhibit a bathochromic effect with an increment in the conjugated moieties. While introducing the hexyl chain effectively increases the solubility of the conjugated molecules, the electron-density donation of hexyl chain also reflects a bathochromic effect on the UV-vis absorption. We also observed an inhibition toward the formation of π-π stacking aggregation in TiO2:IMs films attributed to conjugated molecules bearing a hexyl chain. Furthermore, contact angle analysis shows that, hexyl chian-containing modifiers form a higher average water contact angle than those without hexyl chain, suggesting a better lipophilicity on the TiO2 surfaces in the presence of conjugated molecules consisting hexyl chain which in turn increases its compatibility with organic materials. Collectively, our study concluded that modified TiO2 films containing the SL-series compounds have a higher quenching ratio in comparison to their unmodified counterpart. These results can further extend to the notion that conjugated molecules can serve as an interface modifier between organic donor and inorganic acceptor to warrant a better performance in the heterojunction photovoltaic devices.

Donor-Acceptor (D-A) systems in which a triphenylamine has tethered at meso phenyl position of corrole (1-TPA-Cor) corrole monomer, (2-TPA-Cor) corrole dimer, and (3-TPA-Cor) corrole trimer have been designed and synthesized. All three D-A systems have been characterized by various spectroscopic techniques that include 1H NMR, 13C NMR, HR -MS, absorption, and emission (both steady-state and lifetime) spectroscopies as well as electrochemical methods. Optical and theoretical studies suggest that there will be π-π interactions between donor triphenylamine (TPA) and acceptor corrole (Cor) units and as a result both Soret and Q-bands are red-shifted with broadening of Soret band. Selective excitation of TPA in these D-A systems at 300nm resulted in the quenching of TPA emission suggested the photo-induced electron transfer (PET) from 1TPA* to corrole. In contrast, excited at 405nm also resulted in quenching of emission of Cor. As the number of corrole units and polarity of the solvent increased the quenching is more and suggested that PET reactions in these D-A systems. Time-resolved fluorescence studies shown the presence of PET within these systems and revealed an ultra-fast electron rate of ∼108 to 1010s-1, follows the order 3-TPA-Cor>2-TPA-Cor>1-TPA-Cor and are polarity of solvent dependent.

The presence of downward shift in the band edge and the recombination reactions in the hemicyanine-sensitized solar cell reduces the open-circuit potential (VOC) and the short-circuit current density (JSC), which in turn decreases the dye cell performance. Choosing either an electrolyte possessing minimum overpotentials or a systematic dye design which can efficiently suppress the diffusion of charged species toward the TiO2 can improve the overall power conversion efficiency (PCE). Here, a series of donor–acceptor (D-A) hemicyanine dyes were synthesized utilizing a planar heterotriangulene (HT) or triphenylamine (TPA) donor and alkyl-functionalized indolium carboxylic acid acceptor unit. By introducing strong HT donor instead of TPA, the photophysical, and electrochemical properties of D-A dyes are significantly modulated. The strong donor nature of HT and effective passivation of surface by hydrophobic alkyl chains close to the anchoring group for NC3 dye exhibits an average PCE of 4.34% with a VOC of 0.416 V, JSC of 20.04 mA cm–2, and fill factor (ff) of 52.03% under simulated AM 1.5G illumination (100 mW cm–2) without 3α,7α-dihydroxy-5β-cholic acid coadsorbent (CDCA). The intrinsic dipole of the hemicyanine dye and the presence of Li+ ions in iodide/triiodide redox couple without tert-butylpyridine (TBP) additive induces a downward shift in conduction band edge (ECB) of TiO2. By rational molecular design, the extend of shift in ECB is controlled and enhanced the VOC. Electrochemical impedance spectroscopy (EIS) studies revealed the high charge transfer resistance (Rct) and long lifetime (τ) of injected electrons in HT-based dyes than that of TPA derivatives, which provide insight into the passivation of Li+ and I– ions by current D-A dye design possessing alkyl functionalities to increase both the JSC and VOC.

Donor-acceptor (D-A) molecules have drawn massive attention recently in the design of high-performance materials, but the underlying reasons for the magic abilities of D-A architecture in building very different organic semiconductors are still unclear. Here, based on a series of experimentally bipolar host and thermally activated delayed fluorescence (TADF) molecules with the same donor but different acceptor units, it was found that TADF emitters have more effective charge transfer between donor and acceptor units than bipolar host molecules. More efficient conjugation effects between the donor and acceptor units of host materials were identified from the lower dihedral angles of the D-A structure, smaller and even negative charge transfer amount, shorter charge-transfer length, and larger hole-electron overlap extent. These findings with in-depth insights into different interaction models of donor and acceptor units shed important light on the molecular design of TADF emitters and bipolar materials in a D-A architecture.

Synthesis, structure, photophysical, and electrochemical properties of donor–acceptor ferrocenyl derivatives

New highly electrophilic gem- and spiro-activated trichloromethylnitrocyclopropanes were obtained by the Michael-initiated ring closure (MIRC) reaction of 1-bromo-1-nitro-3,3,3-trichloropropene with linear and cyclic CH-acids catalyzed by bases. Conditions for obtaining the target cyclopropanes were optimized. The process is characterized by high diastereoselectivity and allows obtaining cyclopropanes with trans-configuration of -NO2 and -CCl3 groups. Monocyclic (based on malonic acid dinitrile, methyl cyanoacetate, ethyl cyanoacetate, benzoylacetonitrile), spirocarbo- (based on 1,3-indanedione) and spiroheterocyclic (based on Meldrum's acid, dimethylbarbituric acid, 3-methyl-1-phenyl-5-pyrazolone) cyclopropane structures were isolated and characterized.

Carbazole-based photocatalyst (4CzIPN) as a novel donor-acceptor (D-A) fluorophore catalyzed gram-scale 2-amino-4H-chromene scaffolds photosynthesis via a proton-coupled electron transfer (PCET) process

Effect of small-size co-sensitizer on acid-base co-sensitization system of dye-sensitized solar cells

Ethyl cyanoacetate is a chemical intermediate that has been frequently used. The esterification of cyanoacetic acid and absolute ethanol with a mixed catalyst yielded ethyl cyanoacetate (the same proportion of silicotungstic and p-toluene sulfonic acid as catalyst). The influence factors of the amount of catalyst, n (cyanoacetic acid): n (absolute ethanol), reaction time and reaction temperature on the esterification rate was investigated by orthogonal experiment of four factors and three levels. The product was analyzed by gas chromatography to determine the optimum reaction conditions

Ethyl cyanoacetate is an important chemical intermediate and has been used widely. Ethyl cyanoacetate was prepared by esterification of cyanoacetic acid and absolute ethanol with mixed catalyst (the same proportion of silicotungstic and p-toluene sulfonic acid as catalyst). The influence factors of the amount of catalyst, n(cyanoacetic acid): n ( absolute ethanol), reaction time and reaction temperature on the esterification rate was investigated by orthogonal experiment of four factors and three levels. The product was analyzed by gas chromatography to determine the optimum reaction conditions.

Tunable emission in aggregated T-Shaped 2H-Benzo[d][1,2,3]triazoles with waveguide behaviour

The products of the condensation of aryldiazonium salts with ethyl cyanoacetate are the (Z)- and (E)-isomers of the hydrazono forms. These have been examined separately by 13C n.m.r. spectroscopy which allows their specific identification. The effects of the geometric configurations and of substituents within the aromatic rings on the cyanoacetic acid carbon resonances have been examined.

Base and metal free true recyclable medium for Knoevenagel condensation reaction in SDS-ionic liquid-aqueous miceller composite system