Fluorescence from aromatic compounds isolated in the solid state by double intercalation using layered polymer crystals as the host solid

Poly(muconic acid)s, stereoregular polymer crystals obtained by topochemical polymerization using supramolecular control, function as the layered host solids for organic intercalation, in which alkylamines as the guest species are reversibly inserted into them through an acid-base interaction. We now report a double-intercalation method using alkylamine and pyrene as the guests to control the fluorescence property in the solid state. An aromatic compound can be separately introduced into the hydrophobic layers of the ammonium polymer crystals. The aromatic molecules, which are sandwiched between two alkyl layers, show fluorescence emission from the single molecule but not the excimer. This method can be applied to various organic photofunctional materials showing unique fluorescence properties.     

A novel system for the synthesis of nitriles from carboxylic acids

A simple, mild and high yielding method for the conversion of various carboxylic acids to nitriles has been developed using diphosphorus tetraiodide in combination with ammonium carbonate at room temperature.     

Orientational control of guest molecules in an organic intercalation system by host polymer tacticity

Four kinds of stereoregular poly(muconic acid)s, which are synthesized by topochemical polymerization and subsequent solid-state hydrolysis, are used as the organic host materials for intercalation. We describe the reaction behavior and layered structure of intercalation compounds using stereoregular poly(muconic acid)s and n-alkylamines as host and guest, respectively. The packing structure of the guest alkylamines was determined by X-ray diffractions as well as IR and Raman spectroscopies. We have found that the orientation of the guest molecules is controlled by the host polymer tacticity, depending on the structure of the two-dimensional hydrogen-bonding network formed in the polymer sheets of the crystals.     

Di-, tri-, and tetra-arylterephthalic acids as novel clathrate host compounds

Novel terephthalic acid host compounds having aromatic substituent 1-4 have been prepared and their inclusion properties were investigated. These host compounds enclathrated several kinds of alcohols, ethers, ketones, amides, and sulfoxides. The X-ray structures of 1:1 2a/EtOH, 1:2 2b/DMF, 1:2 3/MeOH, and 1:1 4/EtOH complexes revealed complexation mode.     

Lewis superacids derived from triflic and triflimidic acids and their use as catalysts in 1,6-diene cycloisomerisation

We have developed a procedure for the preparation of anhydrous metallic triflates and triflimidates of general formulae M(OTf)_n and M(NTf₂)_n based on the oxidative dissolution of metal powders in the presence of HOTf or HNTf₂, respectively. The method provides salts in anhydrous form, solvates with DMSO molecules, and constitutes a good complement to a previous method developed in our group based on an electrochemical procedure. We have compared the catalytic activity of various Sn(IV) salts in the reaction of cycloisomerisation of 1,6-dienes and identified that anhydrous Sn(IV) triflimidates are more active catalysts, as compared to anhydrous Sn(IV) triflate, or their hydrated forms usually obtained by conventional methods of preparation or purchased from chemical suppliers.     

Vinyl triflates derived from 1,3-dicarbonyl compounds and analogs: access and applications to organic synthesis

This review details the current methods used to prepare vinyl triflates derived from 1,3-dicarbonyl compounds and describes the reactivity of such functionalized vinyl triflates. α-Ketovinyl triflates can easily and stereoselectively be produced through three different ways. Enolization and triflation is the most common route, but direct triflation with triflic anhydride could also be used, each involving different mechanisms. Direct addition of triflic acid and related sulfonic acids to triple bond offers an alternative to the previous methods. With their peculiar set of functional groups, α-ketovinyl triflates can react in four different ways. The vinyl triflate part could be engaged in coupling reactions, while the carbonyl group as well as the enone motif could be subjected to nucleophilic additions. If a proton is available next to the triflate group, eliminations could occur under basic conditions. Upon addition, fragmentations could also be possible.     

A catalyst system for the reaction of carboxylic acids with aliphatic isocyanates

Catalysts have been found for the selective reaction of aliphatic isocyanates with carboxylic acids giving amides after carbon dioxide extrusion. Magnesium and calcium salts lead to a dramatic increase in reaction rates while improving the selectivity when sterically hindered isocyanates and/or carboxylic acids are used.     

New pincer-like receptor derived from trans-cyclopentane-1,2-diamine as a chiral shift reagent for carboxylic acids

A new pincer-like enantiopure receptor bearing two (1R,2R)-cyclopentane-1,2-diamine moieties has been synthesized and tested as a chiral shift reagent (CSR) for different carboxylic acids. This CSR is efficient for those acids bearing an aromatic group attached to Cα, especially for arylpropionic acids. A full structural study of the diastereomeric supramolecular complexes has allowed us to propose a reasonable model for the interaction.     

Synthesis of novel polyarylate with elecrooptical chromophores as side chain as electro-optic host polymer

Two novel soluble polyarylates with different nonlinear optical chromophores as the side chains were prepared and characterized by UV–visible spectra, nuclear magnetic resonance, and infrared spectroscopy. The titled polymers show us good thermal stability; the thermal decomposition temperature values were 201 and 253?°C, respectively, for polymer sPAR-CTCF and sPAR-CTCP. The glass transition temperatures were 139 and 122?°C for sPAR-CTCF and sPAR-CTCP, respectively. Chromophore FTC-wl was doped in these polymers as a guest chromophore to form binary chromophore electro-optic (EO) system. And super large EO coefficients (124?pm/V) were found from FTC-wl-doped sPAR-CTCP binary chromophore system at high chromophore loading density.     

Enantioselective recognition of carboxylates: a receptor derived from alpha-aminoxy acids functions as a chiral shift reagent for carboxylic acids

Enantioselective recognition of carboxylates has important implications in asymmetric synthesis and drug discovery. We have prepared a novel C2-symmetric receptor 1 from alpha-aminoxy acids in a high overall yield. A series of chiral recognition studies indicate that receptor 1 not only can bind to carboxylate ions tightly but also has a good ability to recognize enantiomers of a broad variety of carboxylic acids in the 1H NMR spectra. Thus, the receptor 1 can be used as a chiral shift reagent for the determination of enantiomeric purities of chiral carboxylic acids by 1H NMR directly and rapidly.     

Carbazole compounds as host materials for triplet emitters in organic light-emitting diodes: polymer hosts for high-efficiency light-emitting diodes

A carbazole homopolymer and carbazole copolymers based on 9,9'-dialkyl-[3,3']-bicarbazolyl, 2,5-diphenyl-[1,3,4]-oxadiazole and 9,9-bis(4-[3,7-dimethyloctyloxy]phenyl)fluorene were synthesized and their electrical and photophysical properties were characterized with respect to their application as host in phosphorescent polymer light-emitting diodes. It is shown that the triplet energy of a polymer depends on the specific connections between its building blocks. Without changing the composition of the polymer, its triplet energy can be increased from 2.3 to 2.6 eV by changing the way in which the different building blocks are coupled together. For poly(9-vinylcarbazole) (PVK), a carbazole polymer often used as host for high-energy triplet emitters in polymer light-emitting diodes, a large hole-injection barrier of about 1 eV exists due to the low-lying HOMO level of PVK. For all carbazole polymers presented here, the HOMO levels are much closer to the Fermi level of a commonly used anode such as ITO and/or a commonly used hole-injection layer such as PEDOT:PSS. This makes high current densities and consequently high luminance levels possible at moderate applied voltages in polymer light-emitting diodes. A double-layer polymer light-emitting diode is constructed comprising a PEDOT:PSS layer as hole-injection layer and a carbazole-oxadiazole copolymer doped with a green triplet emitter as emissive layer that shows an efficacy of 23 cd/A independent of current density and light output.     

Acid-catalyzed alkenylation of aromatic compounds with 1,3-pentadiene as a route to new modifying additives for polymer compounds

Alkenylation of a series of aromatic compounds with 1,3-pentadiene was studied. The oligomeric alkenylation products cured with hexamethylenetetramine were used for modifying elastic-strength properties of elastomeric compounds and improving the compatibility of the elastomers with silicic acid fillers.     

New chiral auxiliaries derived from (S)-α-phenylethylamine as chiral solvating agents for carboxylic acids

The two new diastereoisomeric chiral auxiliaries 1a and 1b were synthesized conveniently and effectively. ¹H NMR was employed to investigate their chiral recognition ability. Compared with (S)-PEA, these new chiral auxiliaries exhibited better enantioselectivity towards the carboxylic acids we had chosen.     

Ionic liquid crystals derived from the protonation of poly(propylene imine) dendrimers with a cholesterol-based carboxylic acid

The liquid crystalline character of salts resulting from the interaction of poly(propylene imine) dendrimers with 3-cholesteryloxycarbonylpropanoic acid has been studied. The supramolecular structure and consequently the observed liquid crystalline phases are dictated by the degree of protonation of primary amino groups as compared with that of tertiary ones, determined by FTIR spectroscopy in the bulk and by NMR spectroscopy in solution. Glass transition temperatures of the materials are about 38°C. At higher temperatures they are transformed to smectic C* phases while a second-order smectic C phase to smectic A phase transition is observed between 90 and 110°C depending on dendrimer generation. At about 150°C the onset of degradation is observed. The influence of the ionic dendrimeric scaffold on the thermotropic properties is discussed.     

Ionic liquid crystals derived from the protonation of poly(propylene imine) dendrimers with a cholesterol-based carboxylic acid

The liquid crystalline character of salts resulting from the interaction of poly(propylene imine) dendrimers with 3-cholesteryloxycarbonylpropanoic acid has been studied. The supramolecular structure and consequently the observed liquid crystalline phases are dictated by the degree of protonation of primary amino groups as compared with that of tertiary ones, determined by FTIR spectroscopy in the bulk and by NMR spectroscopy in solution. Glass transition temperatures of the materials are about 38°C. At higher temperatures they are transformed to smectic C* phases while a second-order smectic C phase to smectic A phase transition is observed between 90 and 110°C depending on dendrimer generation. At about 150°C the onset of degradation is observed. The influence of the ionic dendrimeric scaffold on the thermotropic properties is discussed.     

A comparison of ferroelectric liquid crystals containing diastereomeric propionic acids derived from natural ethyl lactate

Two diastereomeric carboxylic acids, 2(S)-[2(R)-methylhexyloxy]propionic acid and 2(S)[2(S)-methylhexyloxy]propionic acid, were prepared from ethyl (S)-lactate and (R)-1-iodo2-methylhexane or (S)-1-iodo-2-methylhexane in the presence of Ag₂O. From these acids two liquid crystals, 2 and 3, whose configurations are (S, R) and (S, S) were synthesized and their liquid crystal properties investigated. Although both LCs have the same phase sequence Cr-SmC*-N*-I as well as a wide SmC* phase range, the influence of the relative stereochemistry on their physical properties is clear. The liquid crystal with (S, S)-configuration possesses better properties: lower SmC* phase transition temperature, wider SmC* phase range and higher P_s value. The P_s value difference between the ferroelectric LCs 2 and 3 (97 and 131nCcm^-2, respectively, at T_c - T = 10°C) is unexpectedly large. The consideration, alone, of a zigzag conformation at the chiral molecular part of 2 and 3 is insufficient to explain such a difference.     

A comparison of ferroelectric liquid crystals containing diastereomeric propionic acids derived from natural ethyl lactate

Two diastereomeric carboxylic acids, 2(S)-[2(R)-methylhexyloxy]propionic acid and 2(S)[2(S)-methylhexyloxy]propionic acid, were prepared from ethyl (S)-lactate and (R)-1-iodo2-methylhexane or (S)-1-iodo-2-methylhexane in the presence of Ag₂O. From these acids two liquid crystals, 2 and 3 , whose configurations are (S , R ) and (S, S) were synthesized and their liquid crystal properties investigated. Although both LCs have the same phase sequence Cr-SmC*-N*-I as well as a wide SmC* phase range, the influence of the relative stereochemistry on their physical properties is clear. The liquid crystal with (S, S)-configuration possesses better properties: lower SmC* phase transition temperature, wider SmC* phase range and higher P_s value. The P_s value difference between the ferroelectric LCs 2 and 3 (97 and 131nCcm^-2, respectively, at T_c - T = 10°C) is unexpectedly large. The consideration, alone, of a zigzag conformation at the chiral molecular part of 2 and 3 is insufficient to explain such a difference.