Light Emitting Diodes Prepared from Terbium‐Immobilized Polyurea Chelates

Abstract

This article describes the synthesis and application of poly(1,4‐phenylene‐2,6‐pyridylurea) (MCPU) as a charge transporting and rare earth metal chelating host matrix for organic light emitting diodes (OLEDs). The chelation between MCPU and Terbium (Tb³⁺) (the rare earth metal used in this study), is facile in nature and persists in thin films obtained by spin coating onto various substrates. Multiple polymer chelating moieties at each Tb ion site may derive from MCPU repeat units from a single polymer chain or two polymer chains, and their respective structures are proposed. The emissive properties of these films in the presence and absence of Terbium (Tb³⁺) were characterized by steady state UV‐VIS absorption spectroscopy and photoluminescence (PL) spectroscopy. The PL emission from Tb(MCPU) films indicate contribution from both the host MCPU and the Tb ions. The incorporation of these films in OLEDs employing different device architectures yields electroluminescence spectra, which show the characteristic emission of the Tb ions but no emission from the host polymer matrix. Although these devices are not optimized, they exhibit an order of magnitude higher external quantum efficiency as compared to that of conventional aluminum tris 8‐hydroxyquinoline (Alq₃) based OLEDs, at low current densities.     

Cyclic Aromatic Polyamides via the Triphenylphosphite Method

Abstract

5‐tert‐Butyl‐isophthalic acid (TIPA) was polycondensed with three different aromatic diamines by means of triphenylphosphite (TPP) and pyridine. The resulting polyamides were characterized by solution viscosities and MALDI‐TOF mass spectra (m.s.). These m.s. revealed significant fractions of cyclic oligo‐ and polyamides in all samples. In polyamides of high molecular weight, only cycles were detectable (observed up to masses of 13,000 Da). Three poly(amide‐imide)s were prepared by TPP‐mediated polycondensation of trimellitic anhydride (TMA) and three aromatic diamines. Although relatively high molar masses were obtained, the MALDI‐TOF m.s. displayed the peaks of linear chains in addition to those of cyclic polymers. The results together suggest that the side reactions mainly occur at the amino endgroups.     

Anion Receptor with Xylene Bridged Two Imidazolium Rings

A m-xylene bridged imidazolium receptor 1 has been designed and synthesized. The receptor 1 utilizes two imidazole (C–H)⁺—anion hydrogen bonds and one aromatic hydrogen—anion hydrogen bond. The major driving force of complexation between the receptor 1 and anions comes from two imidazole (C–H)⁺—anion hydrogen bonding. However, some hydrogen bonding energy between aromatic hydrogen and anion exists, although it is expected to be much smaller than that of imidazole (C–H)⁺—anion hydrogen bonds.

     

QSAR-based toxicity classification and prediction for single and mixed aromatic compounds

Quantitative structure-activity relationships (QSARs) based on the octanol/water partition coefficient were employed to predict acute toxicities of 36 substituted aromatic compounds and their mixtures. In this study, the model developed by Verhaar et al. was modified and used to calculate octanol/water partition coefficients of chemical mixtures. To validate the model, acute toxicities of these chemicals were measured to Vibrio fischeri in terms of EC⁵⁰. The results indicated that the obtained QSAR models could be used to predict toxicities of samples consisting of these substituted aromatic compounds, individually or in combinations. The obtained equations were proved to be robust enough by using the leave-one-out test method. By classifying these chemicals into two groups, polar and non-polar, the toxicities of chemical mixtures within each group can be predicted accurately from their calculated partition coefficients.     

An efficient one-pot multi-component synthesis of 3,4,5-substituted furan-2(5H)-ones catalyzed by tetra-n-butylammonium bisulfate

A facile one-pot synthesis of 3,4,5-substituted furan-2(5H)-one derivatives from a three-component reaction of aniline derivatives, dialkylacetylenedicarboxylates and aromatic aldehydes under mild conditions using tetra-n-butylammonium bisulfate as a catalyst has been developed.     

Convenient Synthesis of 14‐Aryl‐14‐H‐dibenzo[a,j]xanthenes Catalyzed by Acyclic Brønsted Acidic Ionic Liquid [H—NMP]+[HSO4]− under Microwave Irradiation

Efficient method for direct preparation of 14‐aryl‐14‐H‐dibenzo[a,j]xanthenes through condensation of β‐naphthol with various aromatic aldehydes in the presence of the catalytic amount of [H—NMP]⁺[HSO₄]^? under microwave irradiation was described. This method has the advantages such as; very easy reaction workup, absolute separation of catalyst from the reaction mixture and smooth recyclability of catalyst. In this reaction 14‐aryl‐14‐H‐dibenzo[a,j]xanthenes were obtained as desired products in excellent yields and short reaction times via green and one‐pot procedure.     

One Facile Preparation of N‐Aroyl‐N′‐arylsulfonylhydrazines by Oxidation of Aromatic Aldehyde N‐Arylsulfonylhydrazones with bis(Trifluoroacetoxy)iodobenzene

N‐aroyl‐N′‐arylsulfonylhydrazines can be obtained by oxidation of aromatic aldehyde N‐arylsulfonylhydrazones with bis(trifluoroacetoxy)iodobenzene in acetone at room temperature in mild to good yields.     

Convenient Procedure for Synthesis of N‐Protected β‐Aminomalonates and β‐Amino Acids From α‐Amidosulfones

A synthesis of N‐protected β‐aminomalonates starting from α‐amidosulfones under very mild and simple reaction conditions is described. Treatment of the sulfones with malonate esters in the presence of 2.5 equivalents of potassium carbonate affords the desired products in good yield. A variety of N‐Z and N‐Boc protected aliphatic and aromatic α‐aminosulfones and malonate esters have been successfully used as starting materials. Hydrolysis with concomitant decarboxylation of the N‐protected β‐aminomalonates provides a convenient access to racemic β‐amino acids.     

Organic Reactions in Ionic Liquids: Ionic Liquid Ethylammonium Nitrate–Promoted Knoevenagel Condensation of Meldrum's Acid With Aromatic Aldehydes

The Knoevenagel condensation of Meldrum's acid with aromatic aldehydes proceeded efficiently in a reusable ionic liquid, ethylammonium nitrate, at room temperature in the absence of any catalyst with high yields.