Arylamine Moieties Research Articles

Towards enhancing spin states in doped arylamine compounds through extended planarity of the spin coupling moieties

Arylamine moieties oxidized to radical cations are promising spin bearers for organic high-spin compounds.

Ionic Thiourea Organocatalysis of the Morita–Baylis–Hillman Reaction

An ionic thiourea based organocatalyst has been shown to promote a 1,4-diazabicyclo[2.2.2]octane, (DABCO) catalysed Morita-Baylis-Hillman reaction between benzaldehyde and cyclohex-2-en-1-one. The ionic thiourea catalyst was easily prepared from a pyrrolidinium salt containing an arylamine moiety and 3,5-di(trifluoromethyl)phenylisothiocyanate. X-ray crystallographic analysis of the ionic thiourea catalyst shows an acetone molecule doubly hydrogen bonded to the Lewis acidic thiourea N-H protons. Entrainment of the ionic thiourea co-catalyst in the ionic liquid N-butyl-N-methylpyrrolidinium bistriflimide, [BMPyr][N(Tf)2], facilitates catalyst recycling and affords very good yields with reaction times reduced through use of microwave heating.

Histochemical evaluation of catechins in PEG stressed transgenic tea plants using catechin-specific-diazotized sulfanilamide reagent

We investigated the applicability of catechin-specific-reagent (CSR) for histochemical evaluation of catechins. The diazotized arylamine moiety in CSR reacts specifically with the A-ring of catechins to yield a golden yellow complex. This makes it highly specific for spectrophotometric quantification of catechins. Therefore, microtome cut sections of untransformed and osmotin-expressing transgenic leaves and stem of tea were stained with CSR. We found catechins in the form of golden yellow globules. The catechin globules increased in the structurally intact and highly turgid cells of osmotin expressing transgenic tea plants after stress treatment with 20% PEG; by contrast, the cells in non-transgenic plants accumulated fewer catechin globules. Spectrophotometric quantification of catechins also confirmed higher levels in transgenics compared to untransformed plants. We found elevated accumulation of catechins in stress tolerant cells of tea leaves.

Influence of the terminal electron donor in D–D–π–A phenothiazine dyes for dye-sensitized solar cells

We report three new molecularly engineered push–pull dyes based on phenothiazine (PTZ) as a π-conjugating linker and arylamine moiety as donor and compared with a simple phenothiazine derived reference dye. Absorption spectra, electrochemical cyclic voltammetry, theoretical calculations, current–voltage curves and electrochemical impedance spectroscopy were performed to understand the terminal electron donor influence on the performance of D–D–π–A PTZ dyes. Among these four dyes, the dye incorporating a 9-hexyl-9H-carbazole shows the best photovoltaic performance: a short-circuit photocurrent density of 14.02 mA cm−2, an open-circuit photovoltage of 748 mV, and a fill factor of 0.68, corresponding to an overall conversion efficiency of 7.13% under standard global AM 1.5 solar light conditions.

Synthesis and Electroluminescent Properties of OLED Green Dopants Based on BODIPY Derivatives

Organic light-emitting diodes (OLEDs) based on the small organic molecules have gained remarkable attention for display and solid-state lighting applications over the last few years due to their well-defined molecular structures, facile syntheses and modifications, and specific structure-property correlations. One approach that has been used to improve the efficiency of the OLED devices in term of brightness and stability is the introducing of the highly fluorescent organic guest dopants into the host materials to obtain the full color display. Therefore, there is still a need for the development of new dopants with good color purity, stability and high efficiency. Difluoroboradiaza-s-indacene (BODIPY) represents an outstanding class of fluorophore with high quantum yield, large molar absorption coefficient, high chemical, thermal and photophysical stability. The development of new BODIPY derivatives has become a booming of research due to their potential applications in luminescent devices, chemical sensors, biological labeling, and photovoltaic cells. Major efforts have been devoted to obtain the welldesigned BODIPY structures by modifying of the pyrrole core, fusing some aromatic rings to the BODIPY core, and replacing the 8-carbon atom with a nitrogen atom to form aza-BODIPY. The incorporation of boron element into the π-conjugated framework may lead to the appearance of unique electronic and photophysical properties. Recently, we have successfully explored some green dopants based on arylamine 2,3-disubstituted bithiophene derivatives for OLEDs. In the course of our ongoing studies, herein we wish to report the novel green dopants based on BODIPY and two different arylamine moieties with good overall performance in the multilayer device (Figure 1). In the design of the target molecules 5a–b (Figure 1), the outstanding fluorescent BODIPY core was fused with different arylamine moieties which were expected to enhance the light emitting efficiency through the extension of the

Synthesis of Some Green Dopants for OLEDs Based on Arylamine 2,3-disubstituted Bithiophene Derivatives

A series of green dopants based on 2,2-diphenylvinyl end-capped bithiophene and three different arylamine moieties (9-phenylcarbazole, triphenylamine, and N,N’-di-(p-tolyl)benzeneamine) were successfully synthesized by the Suzuki and Wittig coupling reactions. The photophysical properties of these compounds are reported. The strongest PL emitting compound with the 9-phenylcarbazole moiety has been used for fabricating an OLED device with good overall performance.

Synthesis and characterization of blue light-emitting poly(aryl ether)s containing pyrimidine-incorporated oligofluorene pendants with bipolar feature

Novel blue light-emitting poly(aryl ether)s comprising of bipolar oligofluorene pendants as chromophores have been designed and synthesized, in which pyrimidine and arylamine moieties are utilized as the electron acceptor and electron donor, respectively. Through varying π bridge length from monofluorene to bifluorene and end-cappers from hydrogen to carbazole and diphenylamine, the emission color of the resulting polymers covers from deep blue to greenish blue, and their HOMO and LUMO levels can be modulated to facilitate charge injection to improve the device performance. Polymer lightemitting diodes (PLEDs) are fabricated with the device structure of ITO/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) (50 nm)/polymer (80 nm)/Ca (10 nm)/Al (200 nm). Among these polymers, P2Cz5F-Py with bifluorene bridge and carbazole end-capper shows excellent trade-off between the efficiency and emission wavelength, having a peak luminous efficiency as high as 1.26 cd/A and Commission Internationale de L’Eclairage (CIE) coordinates of (0.17, 0.17).

Synthesis and In Vitro Antioxidant Evaluation of Some Indole-2-carboxylic Acid-Aryl Amine Conjugates

A simple and efficient protocol for the synthesis of novel indole-2-carboxylic acid analogues having aryl amine moieties (2a-k) has been described. The synthesized compounds were characterized by spectroscopic techniques (IR, 1 H NMR, 13 C NMR and MS-EI) and further screened for their antioxidant activity by using various in vitro assays such as 2,2-diphenyl-1-picrylhydrazyl (DPPH • ) scavenging assay, 2,2 ' -azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS •+ ) radical scavenging activity, ferric reducing antioxidant power, cupric ion reducing ability method and phosphomolybdate method. In all the antioxidant assays performed, compounds 2b, 2d, 2e and 2f showed promising antioxidant activity. Whereas, compound 2c displayed potent antioxidant activity.

Electroluminescent properties of 6-N,N-diarylsubstituted-1H-pyrazolo[3,4-b]quinolines as light emitting diode chromophore

In this paper we applied 1H-pyrazolo[3,4-b]quinolines substituted with arylamine moiety as dopants in poly(9-N-vinylcarbazole) PVK matrix which serves as hole transporting material for light emitting diodes. The study of electroluminescence is performed for 1H-pyrazolo[3,4-b]quinolines derivatives for chromophore possessing different ground state dipole moments. Correlation between the values of these dipole moments and the output EL is explored. Role of dipole–dipole (chromophore–polymer interaction is explored). For this reason quantum chemical calculations of the ground state dipole were performed.

4-Amino-5-(arylaminomethyl)-2-(methylthio)furo[2,3-d]pyrimidines via Mitsunobu Reaction of 4-Amino-5-(hydroxymethyl)-2-(methylthio)furo[2,3-d]pyrimidine with N-Mesyl- and N-Nosylarylamines

An efficient method for the synthesis of 4-amino-5-­(arylaminomethyl)-2-(methylthio)furo[2,3- d ]pyrimidines via the Mitsunobu­ reaction of 4-amino-5-(hydroxymethyl)-2-(methylthio)furo[2,3- d ]pyrimidine with N -mesyl- and N -nosylarylamines, and subsequent removal of the mesyl and nosyl groups, has been developed. The influence of substituents in the arylamine moiety on the Mitsunobu reaction was investigated. An unexpected nucleophilic substitution of a nitro group in the reaction of N -({4-amino-2-(methylsulfonyl)furo[2,3- d ]pyrimidin-5-yl}methyl)-4-nitro- N -phenylbenzenesulfonamide with sodium methoxide was observed.

Novel 2,4-difluorophenyl-functionalized arylamine as hole-injecting/hole-transporting layers in organic light-emitting devices

Novel 2,4-difluorophenyl-functionalized triphenylamine and its dimer, namely tris(2′,4′-difluorobiphenyl-4-yl)-amine (3FT) and N4,N4,N4′,N4′-tetrakis-(2′,4′-difluorobiphenyl-4-yl)-biphenyl-4,4′-diamine (4FDT), have been synthesized and characterized. The device with the configuration of ITO/4FDT/Alq3/LiF/Al yields maximum current efficiency of 4.3cd/A. Moreover, with 4FDT as the hole-injecting layer, the maximum efficiency and luminance of the device was further improved to be 5.0cd/A and 19880cd/m2, respectively. The good performance of devices with 4FDT as HTL or HIL was attributed to the incorporation of the strong electron-withdrawing fluorinated substituents into the arylamine moiety, which reduced holes mobility of HTL and HIL and then balanced the injected carriers in devices.

Theoretical Investigations into the Role of Aryl Nitrenium Ions' Stability on Their Mutagenic Potential

By using Mulliken and Natural Bond Orbital (NBO) methods based on the density functional theory (DFT), partial charges of exocyclic nitrogen atoms were calculated for nitrenium ions formed from 201 known drugs and 50 Ames positive (mutagenic) compounds containing aryl amine and nitro moieties. The statistical difference of the partial charges was analysed based on the hypothesis that the mutagens have a more negative charge on their exocyclic nitrogen atom resulting in stable nitrenium ions, and thus a longer lifetime to react selectively with DNA; whereas known drugs are not in general mutagenic and therefore have a relatively more positive partial charge. The nitrenium ions with 1° amine parent compounds did not show a statistical difference between drugs and mutagens based on the Mulliken charges. A slight difference was observed in the NBO data where the drugs have more negative partial charge on their exocyclic nitrogen atoms compared with the mutagens. Interestingly, nitrenium ions with aryl nitro drugs as their parent compounds have more negative charge on the exocyclic nitrogen compared with the other drug classes. Aryl nitro drugs are relatively scarce and are often linked to genotoxicity, which fits with the hypotheses proposed. These results indicate that other physical properties besides the stability of the nitrenium ions are important to determine the mutagenic potential of aryl amine and nitro containing compounds.

Water‐Accelerated Cationic π‐(7‐endo) Cyclisation: Application to Indole‐Based Peri‐Annulated Polyheterocycles

AbstractAn efficient and versatile method for the synthesis of indole‐based polycyclic indolo‐benzazepine and its derivatives through water‐accelerated cationic π‐cyclisation is described. The strategy involves condensation of arylamine moieties linked to C‐4 in indole/azaindole systems with arylaldehydes in water containing catalytic amount of Brønsted acids. The C–C bond formation in water is complete within 10–30 min, furnishing the title compounds in excellent yields and purities, whereas in organic solvents 10–12 h are required. Furthermore, aldehydes both with electron‐donating and‐withdrawing substituents facilitate the π‐cyclisation equally.

Insights in the antioxidant activity of diarylamines from the 2,3-dimethylbenzo[ b]thiophene through the redox profile

Cyclic voltammetry was used to evaluate the antioxidant activity of 7-aryl or 7-heteroarylamino-2,3-dimethylbenzo[ b]thiophenes previously synthesized by some of us, comparing their oxidation potentials with those of the well-known synthetic standards (BHA, BHT). Compounds with electron-donating groups on the arylamine moiety have lower E p/2 than compounds with electron-withdrawing groups or electron-deficient rings (pyridines). The position of the methoxy group on the arylamine moiety also changes the oxidation potential: lower E p/2 for the diarylamines with methoxy groups in the para position. Comparing the first peak potential with the ones of BHA and BHT, the diarylamine compounds show lower oxidation potential, and therefore higher reducing power. A reasonable inverse correlation was also observed between the E p/2 values and the pEC 50 values obtained in antioxidant activity chemical assays. It can be generalized that compounds with lower E p/2 values have better antioxidant activity (DPPH assay) and higher reducing power.

Synthesis of Carbazole/Triarylamine Containing Polyfluorene and Its Application to Electroluminescent Devices

Solution-processable carbazole/triarylamine-based polyfluorene (CT-PF) was designed and synthesized by Suzuki coupling reaction. CT-PF was originally designed to have multiple functions at the same polymer backbone; blue emission and large band gap energy by fluorine group as well as good hole transporting property and tunable ionization potential by excellent electron donating triarylamine and carbazole moieties. It was confirmed from TGA measurement that the synthesized CT-PF had thermal stability up to 379 degrees C. The UV-Visible absorption spectra of CT-PF had absorption maxima at 292 nm and 351 nm in dilute solution, and 332 nm and 400 nm in film state, which might be originated from fluorene and arylamine moieties. PL emission maxima were also measured in the blue range at 425 nm in dilute solution and 468 nm in film state. Turn-on voltage of double-layered OLED with CT-PF as HTL was reduced to 7 V, and the luminescence were enhanced up to 1,397 cd/m2 with maximum current efficiency of 0.32 lm/W and power efficiency of 1.1 cd/A, which were over 3 times higher than those of single-layered device without HTL. PhOLED with CT-PF as a host material for Ir(ppy)3 phosphorescent dopant showed bright green emission with CIE color coordinates as (x = 0.31, y = 0.57).

Application of the Pictet–Spengler reaction to aryl amine substrates linked to deactivated aromatic heterosystems

Three new substrates with an aryl amine moiety attached to quinoxalines, triazoles and tetrazoles either via C or N have been used for the Pictet–Spengler reaction. The substrates have been designed by applying the concept of ‘aryl amine attached to a deactivated heteroaromatic ring’ in a manner to facilitate endo cyclization. This is in contrast to the substrates used traditionally and reported earlier by us that are based on either aliphatic or aryl amine, respectively, attached to an activated heterocyclic ring. The Pictet–Spengler condensation of the three substrates with aldehydes led to the synthesis of novel N-rich polyheterocyclic system hitherto not reported. Our modified strategy opens up possibilities to design novel substrates with aryl amines linked via C or N to either deactivated or activated heterocyclic privileged structure, which in turn can be used for the synthesis of novel fused polyheterocyclic skeletons.

Organic Dyes Containing 1H-Phenanthro[9,10-d]imidazole Conjugation for Solar Cells

Series of dyes based on 1H-phenanthro[9,10-d]imidazole chromophores were developed and characterized. Dye-sensitized solar cells (DSSCs) using the dyes as the sensitizers exhibited good efficiencies, ranging from 2.95 to 4.68%, which reached 45−70% with respect to that of an N719-based device fabricated under similar conditions. Incorporation of arylamine moieties at 1H-phenanthro[9,10-d]imidazole was found to retard charge recombination of the electrons in the conduction band of TiO2 with the oxidized dyes. In contrast, incorporation of hydrophobic dodecanyl chains at 1H-phenanthro[9,10-d]imidazole reduced the dark current and improved the device efficiency. Results of TDDFT computation on the compounds are in support of the charge-transfer character of the compounds and consistent with the device performance. A cascade of charge separation is possible for compounds with arylamine moieties via an internal conversion from a bright higher excited state to a long-range charge separated state. Our results indicate that the extent of charge separation in the excited state is an important factor for DSSC efficiency.

Triarylamine-Bearing Poly(1,4-phenylenevinylene): Facile Preparation and Its Durable Aminium Polyradical

Poly[2-{bis(4-methoxyphenyl)amino}phenyl-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] 1 was prepared via the Gilch reaction of the p-bis(chloromethyl)benzene monomer, 2-{bis(4-methoxyphenyl)aminophenyl}-α,α′-dichloro-p-xylene. The Gilch reaction facilitated the preparation of the polyphenylenevinylene with a triarylamine pendant group when compared to that via the Heck polycondensation. The molecular weight of the polymer was approximately 4.0×105, and it was soluble in common solvents and was reversibly redoxed due to the pendant arylamine moiety. Chemical oxidation of 1 afforded the corresponding aminium polyradical 1+ with the half life-time of ca. 2 weeks under ambient conditions. ESR and magnetization measurements of 1+ revealed a forbidden multiplet signal and an average spin quantum number (S) of 3/2 at low temperature, respectively. The polyradical 1+ was the first example of a high molecular weight, high-spin organic polymer with solvent-solubility and film formability. 2,3-Bis[N,N-bis(4-methoxyphenyl)aminophenyl]stilbene 2 and its aminium diradical 2+ were also prepared as the model dimer compounds; 2+ was a triplet molecule at low temperature. The effect of the π-conjugated poly(1,4-phenylenevinylene) backbone on the high-spin alignment was also discussed.

Poly(2-diphenylamino-1,4-phenylenevinylene): Its preparation via chemical vapor deposition polymerization

2,5-Bis(chloromethyl)triphenylamine 1 was prepared and polymerized via the Gilch reaction to give poly(2-diphenylamino-1,4-phenylenevinylene) 2G as a solvent-soluble F-conjugated polymer. 1 was also polymerized via the chemical vapor deposition to yield the precursor polymer of 2C, which was heated under vacuum to yield a yellow or brown thin film of 2C on substrates such as glass and a silicon wafer. Spectroscopies of the film supported the formation of the poly (2-diphenylamino-1,4-phenylenevinylene) 2C. The arylamine moiety of the 2C film worked as a functional group like a redox site.

Hemoglobin adducts in workers exposed to benzidine and azo dyes

Benzidine (Bz) is a known human carcinogen. Several azo dyes have been synthesized with Bz. Bz can be metabolically released from azo dyes. In a group of Indian workers producing Bz and azo dyes the presence of hemoglobin (Hb) adducts was investigated. The following Hb adducts were identified and quantified by GC-MS: Bz, N-acetylbenzidine (AcBz), 4-aminobiphenyl (4ABP), aniline. 4ABP and aniline were quantitatively the major adducts. In the exposed workers (n = 33) all correlations between 4ABP, Bz and AcBz were r = 0.89 (P < 0.01) or greater. The group of workers exposed to Bz (Bz workers, n = 15) had 10-17-fold higher adduct levels than the workers exposed to dyes (dye workers, n = 18). 4ABP can be metabolically released from Bz and azo dyes. Aniline can be metabolically released from azo dyes. Therefore, the presence of 4ABP and aniline as Hb adducts is a consequence of exposure to the parent compounds or to the exposure of Bz and azo dyes and a consequent metabolical release of the arylamine moiety. The mean adduct ratios of 4ABP/(AcBz + Bz) varied up to 4-fold across all seven factories. Therefore, it is possible that 4ABP may have derived from general contamination in the work environment or endogenous metabolism, or a combination of the two. Since 4ABP is also a known human carcinogen, tumors observed in workers exposed to Bz or Bz dyes might be caused by both compounds. Further, these results suggest that understanding the role that genetic variants in NAT1 and NAT2 play in modifying the impact of Bz on bladder cancer risk may be complicated, as N-acetylation detoxifies 4ABP and activates Bz.