Fluorescence and amplified emission properties of single-crystal 2,5-bis(4-biphenylyl)thiophene

Ligth amplification properties are investigated for single crystals of commercially available 2,5-bis(4-biphenylyl)thiophene. Depending on growth methods, three kinds of crystals are obtained having different fluorescence spectra in blue-green color. Under optical pumping, their amplified spontaneous emission (ASE) bands appear at different wavelengths. The solution-grown crystal shows ASE bands at λ = 464 and 494 nm which are assigned to the 0–1 and 0–2 transitions, respectively. By contrast, the vapor- and slide-boat-grown crystals show a red-shifted 0–1 band at λ = 496 and a 0–2 band at 520 nm, respectively.     

4-Chloro-2,6-bis(hydroxymethyl)pyridinium Chloride and 4-Dimethylamino-2,6-bis(hydroxymethyl)pyridinium Chloride Hemihydrate

Abstract  Two substituted pyridinium chloride salts, namely 4-chloro-2,6-bis(hydroxymethyl)pyridinium chloride (triclinic, P-1, a = 6.0651(8) ?, b = 8.4393(8) ?, c = 8.6554(9) ?, α = 78.845(1)°, β = 83.156(1)°, γ = 89.047(1)°; V = 431.55(8) ?³; Z = 2) and 4-dimethylamino-2,6-bis(hydroxymethyl)pyridinium chloride hemihydrate (orthorhombic, Aba2, a = 17.2179(14) ?, b = 17.6332(15) ?, c = 7.2068(6) ?; V = 2188.0(3) ?³; Z = 4), have been structurally characterized. Hydrogen bonding and van der Waals contacts are evident in both structures. Furthermore, the 4-dimethylamino derivative features a trigonal planar dimethylamino group with some π interaction between the nitrogen atom and the pyridine ring. Graphical Abstract  Two compounds, namely 4-chloro-2,6-bis(hydroxymethyl)pyridinium chloride and 4-dimethylamino-2,6-bis(hydroxymethyl)pyridinium chloride hemihydrate, have been spectroscopically and structurally characterized.      

4-(2-Methylphenyl)-1,2,3,4,5,6,7,8-octahydroquinazoline-2,5-dione (I) and 4-(4chlorophenyl)-1,2,3,4,5,6,7,8-octahydroquinazoline-2,5-dione (II)

The crystal and molecular structures of the title compounds have been determined by x-ray structure analysis. The compounds (I) and (II) crystallize in space groups P2₁2₁2₁ and 12/a respectively. The structures were solved by direct methods and refined to R = 0.058 and R = 0.046. The saturated pyrimidine-2-one ring in both structures deviates from the planarity. There are two intermolecular hydrogen bonds in (I) and (II). The configuration at C4 in (I) is S.     

The nematic reentrant phase in binary mixtures composed of a 4-(trans-4-alkylcyclohexyl)-1-(2-cyanoethenyl)-benzene and 60CB

It is shown that the smectic A phase in the 4-(trans-4-n-alkylcyclohexyl)-1-(2-cyanoethenyl)-benzene EPCH homologous series has a partially dimolecular structure of A_d type. The EPCH compounds show a virtual S_Ad → N_re transition revealed in mixtures of 60CB with members of the homologous series with five or more carbon atoms in the alkyl chain. The temperature dependences of electric conductivity and electric permittivity of the 8EPCH-60CB mixture have been tested in the three successive phases, N_re, S_Ad and N.     

Stabilization processes of metastable crystalline phases in 2,5-dichlorothiophene

Three crystalline phases, two metastable and one most-stable phase, were found in 2,5-dichlorothiophene by differential scanning calorimetry (DSC). The relaxation processes from one metastable crystalline phase to another and from this metastable phase to the stable phase were investigated by tracing the enthalpy change for a long time under constant temperature using DSC. The Avrami index n, in the Avrami equation, was found to be approximately 2 for both relaxation processes.     

4-(2,3-Dichlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-bis(methoxycarbonyl), 4-(2,4-dichlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-bis(methoxycarbonyl), and 4-(2,3,5-trichlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-bis(methoxycarbonyl): conformational observations in the crystalline state

Hydrogen bonding interactions displayed by three crystalline chloro-substituted 4-phenyl-1,4-dihydropyridine molecules 4-(2,3-Dichlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-bis(methoxycarbonyl), 4-(2,4-dichlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-bis (methoxycarbonyl) and 4-(2,3,5-trichlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-bis (methoxycarbonyl), suggests that, in contrast to previous observation, sp orientation of the 3 or 5 substituted carbonyl group accomodates hydrogen bonding to the carbonyl oxygen atom when polar orthosubstituents exist on the phenyl ring.     

Design,synthesis and liquid crystalline behavior of ethyl 4-((4-alkoxyphenyl)diazenyl)benzoates

A series of ethyl 4-((4-alkoxyphenyl)diazenyl)benzoate is synthesized and the liquid crystalline behavior studied. Synthesized compounds are characterized by FTIR, ¹H-NMR, Mass and single crystal XRD. Differential scanning calorimetry was carried out to study the phase transitions and enthalpy changes. Polarizing optical microscopy revealed the mesogenic properties. These techniques revealed that three compounds (2a, 2b, 2f) exhibit liquid crystalline properties in the range of 80–104°C. POM exhibiting focal conical fan like texture which revealed the presence of smectic phases suggestive of their use in LCD and temperature sensing devices, besides 2c can be used as green emitter in OLEDs.     

Structural characterization of 2,6-bis(N-methylenepiperidino)-4-nitrophenol (MPN) and 2,6-bis-(N-methylenemorpholino)-4-nitrophenol (MMN)3

MPN: C₁₈H₂₇N₃O₃,M _r=333.43, monoclinic,P2₁/n. a=6.207(2),b=21.893(6),c=13.693(3) Å; =96.12(2)^o,V=1850.1(8) ų.,Z=4,D _cal=1.20 mg/m³,F(000)=720, (CuK)=1.5418 Å, andT=298K.R=0.042 andwR=0.049 for 1675 observed reflections. MMN: C₁₆H₂₃N₃O₅,M _r=337.38, triclinic,P,a=9.642(1) Å,b=10.123(5) Å,c=9.341(2) Å, =93.00(3)^o, =90.96(1)^o, =110.46(1)^o, V=852.5(5) ų,D _cal=1.31 mg m^–3.F(000)=360,Z=2, (CuK)=1.5418 Å,R=0.054 andwR=0.074 for 2804 observed reflections. The piperidine and morpholino rings assumechair conformation and orient each other at an angle of 44.8(1)^o (MPN) and 47.1(1)^o (MMN), respectively.Contribution No. 827 from DCB.     

Trifluoromethyl group disorder in crystalline 2,8-bis(trifluoromethyl)-4-hydroxymethylquinoline

The title compound crystallized in space groupPna2₁ with lattice constantsa=13.406(1),b=18.799 (4), andc=4.785(1). The molecule is essentially flat with only fluorine atoms, methylene hydrogen atoms, and the hydroxyl hydrogen atom out of the plane of the quinoline ring. Only one of the trifluoromethyl groups of the title compound is disordered following a pattern observed in other crystal structures. Quantum chemical calculations at the AM1 level are consistent with this phenomenon. Although the carbon atom of the fixed trifluoromethyl group is further from the quinoline nitrogen atom than the carbon atom of the disordered trifluoromethyl group, the fluorine atoms of the fixed trifluoromethyl group more closely approach the quinoline nitrogen atom by 0.3 Å if the C(8)–C(10) bond in the crystal structure is freely rotated.National Research Council Associate     

Synthesis and crystal structure of 4-(p-methoxyphenyl)-3, 5-bis(4-pyridyl)-1,2,4-triazole

The 4-(p-methoxyphenyl)-3,5-bis(4-pyridyl)-1,2,4-triazole has been synthesized and its crystal structure has been determined by X-ray diffraction methods. It crystallizes in the monoclinic space group P2₁/n, with a = 12.5832(6) Å, b = 7.0512(5) Å, c = 18.4669(12) Å, = 96.826(1)°, and D_calc = 1.345 g cm^–1 for Z = 4. In the structure, two pyridyl rings, phenyl ring, and triazole ring do not share a common plane. The most favored orientation of the pyridyl rings in the crystal is that their planes are inclined toward opposite directions with respect to the triazole ring.     

Mesogenic 3,6-bis(4-hydroxyphenyl)-1,2,4,5-tetrazine alkanoate esters

A novel series of 3,6-bis(4-hdroxyphenyl)-1,2,4,5-tetrazine alkanoate esters were synthesized and their mesogenic properties were studied using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). The impact of changing the tail-core linkage from alkyl or alkoxy to ester is profound. Compared to the alkyl or alkoxy linkages, the ester linkage reduced mesogenic properties. Short-tailed compounds are non mesogenic (4a-4e), while long-tailed compounds (4f-4r) exhibit nematic phases. Unlike the alkyl or alkoxy tail series, none of the 18 presented esters in this series exhibits a smectic phase.     

Synthesis,thermal reactivity and structure of 1,2-bis(4-hydroxy-3-methoxyphenylethynyl)benzene

The crystal structure of the new enediyne 3 was determined by X-ray diffraction. 3 crystallizes in the orthorhombic space group Pbca (No. 61) with a = 12.7148(9) Å, b = 7.4872(8) Å, c = 38.890(4) Å, = = = 90 and Z = 8. The three-dimensional structure is characterized by an 8-membered cyclic array linking four molecules of 3 by hydrogen bonding between phenolic and methoxy groups. Furthermore, stabilization by –-stacking and CH s interactions is present. The important cd distance (between the two terminal acetylene carbons of the enediyne) which is relevant for the Bergman cyclization, was determined to 401 pm, being in good agreement with the high cyclization barrier ( G = 147.9 kJ mol^–1 at 220C) that was determined by differential scanning calorimetry (DSC).     

Knoevenagel condensation of the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione with 9-anthracenecarboxaldehyde: Synthesis of the second-generation ligand 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione

The Knoevenangel condensation between 9-anthracenecarboxaldehyde and the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione (bpcd) takes place rapidly in CH₂Cl₂/MeOH solution in the presence of molecular sieves (4 ?) to produce the functionalized ligand 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione. The title compound has been isolated and characterized in solution by IR, NMR, and UV-vis spectroscopies, and the solid-state structure has been established by X-ray diffraction analysis. 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione crystallizes in the triclinic space group P−1, a=10.227(2) ?, b=13.865(2) ?, c=15.905(2) ?, α=112.157(2)°, β=101.424(2)°, γ=100.065(3)°, V=1968.5(5) ?³, Z=2, and d _calc=1.101 Mg/m³; R=0.0873, R _w=0.2604 for 7452 reflections with I>2σ(I). The cyclic voltammetric behavior for 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione has been studied, and the observed redox data and results from extended Hückel MO calculations are discussed relative to the parent ligand bpcd.

Thermal and phase behaviour studies of hydrogen-bonded compounds (SA:nOBA) using POM,DSC and image-processing techniques

A novel series of hydrogen-bonded liquid crystals are synthesised. The hydrogen bond is formed between non-mesogenic salicylic acid and the mesogenic p-n-alkoxy benzoic acids with n = 4–8, 10–12 and 16. The formation of hydrogen bond is confirmed from infrared studies. The transition temperatures and the phase identification are made with the use of polarising microscope (POM) attached with a hot stage. Further, the heats of transition and enthalpies are obtained by employing the differential scanning calorimeter (DSC). Along with POM and DSC, textural image analysis is done by image-processing techniques using MATLAB software and transition temperatures are identified. The results reveal that the compounds with the chain number n = 7, 8, 10–12 show the manifestation of smectic-B phase by quenching smectic-C phase.     

The crystal and molecular structure of 2,5-dibromo-1,4-phenylenediyl bis(trans-4-ethylcyclohexanoate)

The title compound with the formula C₂H₅ C₆H₁₀ COO-C₆H₂Br₂ OOC C₆H₁₀ C₂H₅ (DPBEC) crystallizes in the monoclinic space group P2₁/c with a = 15.37(2), b = 5.27(1), c = 15.13(2) Å, β = 92.7(1)° and two molecules per unit cell. The structure was solved using film intensity data by heavy atom method and refined to R = 0.078. The fully stretched DPBEC molecules exhibit exact C_i symmetry. Their packing in the crystal is characterized by a non-parallel (cross) arrangement of the molecular long axes.     

Molecular and crystal structure of 3-(4-chlorophenylthio)-1-(2,4-dinitrophenylamino)-pyrrolidine-2,5-dione

3-(4-Chlorophenylthio)-1-(2,4-dinitrophenylamino)-pyrrolidine-2,5-dione, C₁₆H₁₁N₄C10₆S, was obtained in the addition reaction of 4-chlorobenzenethiol and 2,4-dinitrophenyl-aminomaleimide. It forms orthorhombic crystals; the finalR=0.048 for 1083 unique observed reflections. The molecule consists of three rigid rings connected by single bonds. A synclinal conformation of the terminal phenyl rings (A andC) with respect to the central pyrrolidine ring (B) is observed in the crystal, with ringsA andC close to one another. An intramolecular hydrogen bond N(2)O(4) of 2.593(7) Å is observed. The structure of the title compound was also investigated by IR,¹H-NMR and M.S.     

Crystal structure ofcis-bis[1-(2-thienyl)-4, 4,4-trifluoro-1,3-butanedionato]-bis (4-methylpyridine)nickel(II)

The crystal structure of the 4-methylpyridine adduct of bis[1-(2-thienyl)-4, 4,4-trifluoro-1,3-butanedionatolnickel(II) was determined by a three-dimensional x-ray analysis using counter data. The crystals are monoclinic,C2/c, witha = 9.330,b = 18.278,c = 17.855 Å, and = 95.1°. The structure was refined by full-matrix least squares toR = 0.10. The molecule has a two-fold axis, and both enantiomers withcis configuration occur in the crystal. The solvation by 4-methylpyridine is shown to weaken the chelate bonds in the same way as doestrans hydration.