LC-Polyimides. 22. Thermotropic Poly(Amide-Imide)s Derived from New Bisimide Spacers and Biphenyl-4,4′-dicarboxylic Acids

Abstract

A new class of diamine spacers was synthesized from α,ω-diaminoalkanes and 4-nitrophthalic anhydride. The resulting α,ω-bis(4-aminophthalimido)alkanes were polycondensed with terephthaloylchloride, 2-phenylthioterephthaloylchloride, naphthalene-2,6-dicarboxylic acid dichloride, and 4,4′-biphenyl dicarboxylic acid dichloride. Most poly(amide-imide)s proved to be semicrystalline, forming a smectic layer structure in the solid state. Yet only the poly(amide-imide)s derived from 4,4′-biphenyl dicarboxylic acid are thermotropic and form a smectic and a nematic LC-phase. Due to the high temperatures employed, the reversibility of the phase transitions suffers from thermal degradation.     

Vortex-Assisted Liquid–Liquid Microextraction (VALLME): Applications

Recently, a new and fast equilibrium-based solvent microextraction technique termed vortex-assisted liquid–liquid microextraction was developed. In this technique, the dispersion of the extraction solvent is enhanced by vortex mixing. The aim of the present review is to discuss the applications of vortex agitation in solvent-microextraction procedures.     

Vortex-Assisted Liquid–Liquid Microextraction (VALLME): Applications

Recently, a new and fast equilibrium-based solvent microextraction technique termed vortex-assisted liquid–liquid microextraction was developed. In this technique, the dispersion of the extraction solvent is enhanced by vortex mixing. The aim of the present review is to discuss the applications of vortex agitation in solvent-microextraction procedures.

     

Dipyrrolo[1,2-a; 2′,1′-c]pyrazines. 5. Azo coupling of dipyrrolo[1,2-a;2′,1′-c]pyrazines and 5,6-dihydrodipyrrolo[1,2-a; 2′,1′-c]pyrazines

We have synthesized a series of previously unreported azo dyes via the azo coupling of alkyl substituted dipyrrolopyrazines with aryldiazonium chloride. For this type of substrate where one or both -positions of the pyrrole rings of the molecules are not occupied by substituents, electrophilic attack was found to occur initially at carbon atom C₍₃₎.For communication 4 see [1]M. V. Lomonosov State University, Moscow 119899, Russia Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 236–240, February, 1999.     

Dipyrrolo[1,2-a; 2′,1′-c]pyrazines. 4. Aminomethylation of alkyl substituted dipyrrolo[1,2-a; 2′,1′-c]pyrazines and 5,6-dihydrodipyrrolo[1,2-a; 2′,1′-c]pyrazines

We have studied the aminomethylation reaction of alkyl substituted dipyrrolo[1,2-a; 2,1-c]pyrazines and their 5,6-dihydro analogs using different aminomethylating agents. Use of alkoxydialkylaminomethanes (aminoacetals) as Mannich reagents leads to the highest yields of the aminomethylated dipyrrolopyrazines. The compounds prepared have been studied by mass spectrometry.For Communication 3, see [1].M. V. Lomonosov State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 949–957, July, 1998.     

New 1,4‐Diaryl [1,2,3]‐Triazole Liquid Crystals Using a Click Reaction

New nonlinear compounds containing 1,4‐diaryl‐[1,2,3]‐triazole were prepared using a straightforward and efficient method for the regioselective synthesis of [1,2,3]‐triazoles. The methodology consists of a Cu(I)‐catalyzed 1,3‐dipolar cycloaddition of aryl azides to terminal arylacetylenes (click reaction). All compounds exhibited liquid‐crystalline profile.     

Self-Assembly of Aminocyclopropenium Salts: En Route to Deltic Ionic Liquid Crystals

Aminocyclopropenium ions have raised much attention as organocatalysts and redox active polymers. However, the self-assembly of amphiphilic aminocyclopropenium ions remains challenging. The first deltic ionic liquid crystals based on aminocyclopropenium ions have been developed. Differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction provided insight into the unique self-assembly and nanosegregation of these liquid crystals. While the combination of small headgroups with linear p-alkoxyphenyl units led to bilayer-type smectic mesophases, wedge-shaped units resulted in columnar mesophases. Upon increasing the size and polyphilicity of the aminocyclopropenium headgroup, a lamellar phase was formed.     

Liquid crystalline phase transitions in hexakis(4-(4′-heptyloxy)biphenoxy)cyclotriphosphazene

Abstract

Hexakis(4-(4′-heptyloxy)biphenoxy)cyclotriphosphazene (HHCP) was synthesized from hexachlorocyclotriphosphazene and 4-heptyloxy-4′-hydroxybiphenyl. The mesogenicity of HHCP was studied by DSC, FTIR spectroscopy and polarizing microscopy. Enantiotropic smectic C and nematic phases were observed between 450 and 455 K and 455 and 456 K, respectively, on heating, and between 456 and 455 K (nematic) and 455 and 440 K (smectic C) on cooling from the isotropic liquid phase. The introduction of the heptyloxybiphenoxy groups as side chains into cyclotriphosphazene has generated the liquid crystalline phase. FTIR spectroscopy showed that the P=N and P-O-(C) stretching vibrations converted to lower frequencies from 1224 to 1210 cm^?1 and from 920 to 910cm^?1, respectively, at the crystalline (C)-S_c phase transition. This result suggests that the state of the cyclotriphosphazene ring dramatically changes near the C-S_c phase transition.     

Determination of Hypericin in Hypericum perforatum (St. John’s Wort) Using Classical C18 and Pentafluorophenyl Stationary Phases: Contribution of Pi–Pi Interactions to High-Performance Liquid Chromatography (HPLC)

Hypericin is one of the most important bioactive substances present in Hypericum perforatum (Saint John’s Wort), which exhibits various biological activities such as inhibition of neuronal processes coupled with transmission of serotonin, dopamine, gamma-amino butyric acid and L-glutamine. This red-colored derivative of anthraquinone contains six benzene cycles and four hydroxy groups that polarize electron density in the conjugated double bond system and enable the molecule to act as a Lewis base in charge-transfer complexes. In this study, four stationary phases modified by the pentafluorophenyl group were selected to investigate the contribution of π-π interactions to the improvement of hypericin separation in comparison to the separation provided with a classical C18 based chromatographic column. In order to develop a suitable gradient chromatographic method for the quantification of hypericin, normal, polar organic and reverse elution modes were evaluated using high-performance liquid chromatography with ultraviolet-visible and mass spectrometry detection. It was disclosed in the analyses that the pentafluorophenyl stationary phase can separate hypericin from hyperforin, which was not possible to achieve with the C18 based stationary phase. The best analytical method found, employing the pentafluorophenyl stationary phase, showed sufficient linearity, accuracy and precision and was used for the determination of hypericin in Saint John’s Wort.     

Copper(I) complexes—III: Tetrakis,tris and bis amine copper(I) perchlorates

The treatment of Cu(I)ClO₄ with heterocyclic amines leads to the formation of complexes in which copper is tetra-, tri- and dicoordinated. Evidence that precludes coordination by perchlorate and confirms that the trisamine copper(I) complex contains triligated copper, is presented. I.R. results suggest that the formally dicoordinated complexes in fact possess a higher coordination number in the solid, due to the formation of π-complexes, metal clusters or electron deficient bonds. The overall coordination number of copper(I) in each complex is shown to be a function of the basicity and the steric requirements of the ligands and determines the resistance to air oxidation of copper(I). Unexpectedly, for a d¹⁰ ion, several complexes show apparent magnetic moments which are quite large.     

Improved Synthesis of Tetrakis(2‐thienyl)methane

Abstract

An improved synthesis of tetrakis(2‐thienyl)methanes, where an aromatic nucleophilic substitution is the key reaction for the introduction of the fourth 2‐thienyl group, has been developed, thus, reaction of tris(2‐thienyl)methyl anion with 2‐fluoro‐5‐cyanothiophene smoothly proceeded to give (5‐cyano‐2‐thienyl)‐tris(2‐thienyl)methane in good yield. Alkaline hydrolysis of the cyano group to carboxylic acid followed by decarboxylation at 180°C in quinoline in the presence of copper(I) oxide afforded the parent tetrakis(2‐thienyl)methane in 50% total yield from the trithienylmethane.     

Synthesis and Crystal Structure of Tetrakis(1-vinylimidazole-kN3)diisothiocyanatomanganese(Ⅱ)

The title compound I(C22H24MnN10S2,Mr=547.57)has been synthesized and structurally characterized by single-crystal X-ray diffraction.The compound crystallizes in the monoclinic system,space group P21/c with a=8.6010(17),b=9.0180(18),c=17.773(4)(A),β=101.79(3)°,V=1349.5(5)(A)3,Z=2,Dc=1.348 g/cm3,μ=0.674mm-1,F(000)=566,the final R=0.0488 and wR=0.1289.In the structure,each Mn atom is coordinated by four Vim(Vim=1-vinylimidazole)ligands and a pair of monodentate isothiocyanic groups,affording a compressed octahedral MnN6 core.     

Vibrational spectroscope of complexes of platinum(0)—I. Tetrakis(triphenylphosphine)platinum(0) and Dioxygenbis(triphenylphosphine)platinum(0)

Assignment of i.r. and Raman spectra for Pt(PPh₃)₄ and Pt(O₂)(PPh₃)₂ yielded values for νPtP of 137 and 157 cm⁻¹ (Pt(PPh₃)₄); 132 (antisymmetric) and 145 cm⁻¹ (symmetric) (Pt(O₂)(PPh₃)₂). For the dioxygen complex, solution phase Raman spectra gave values for both ν PtO₂ modes for the first time. Data from the ¹⁶O₂, ¹⁶O¹⁸O and ¹⁸O₂ isotopomers were used in a normal coordinate analysis of the PtO₂ fragment. The OO stretching force constant (3.0 mdyn Å⁻¹) is consistent with extensive net π-back-donation into the π* m.o.s of the O₂ ligand.     

Optimized Synthesis of Tetrakis(4-methoxyphenyl)porphin–Co(II)

Detailed kinetic investigation of Rothemund synthesis of porphyrins was conducted in different solvents. A one-pot synthesis of tetrakis(4-methoxyphenyl)porphin–Co(II) from pyrrole, anisic aldehyde, and cobalt acetate was developed that gave 35% isolated yield. Chlorobenzene was found to be the best solvent for the reaction. The synthesis can be done with either propionic or chloroacetic acid as catalyst with about the same yield. Cobalt prevents the synthesis of the porphyrin, so it has to be added in the reaction mixture only after the synthesis of the free porphyrin is finished. Optimum time is 2–2.5 h at a temperature of 130°C. Lower temperatures reduce the yield. Potentially, these dependencies can be applied to synthesis of other analogous porphyrins.     

Dipyrrolo[1,2-a; 2',1'-c]pyrazines. 2. Electrophilic substitution in dipyrrolo[1,2-a; 2′,1′-c]pyrazines: protonation,trifluoroacetylation, acetylation

A number of alkyl-substituted dipyrrolo[l,2-a; 2,1-cIpyrazines have been synthesized and investigated to determine their behavior in reactions of protonation, trifluoroacetylation, and acetylation. The experimental results correlate well with the calculated data in most cases.For communication 1, see [1].M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp, 1566–1572, November, 1995 Original article submitted September 13, 1995.     

8,8′-Bis(diphenylphosphinomethyl)-1,1′-binaphthyl. Synthese und Konformation

Summary The title compound3 was prepared from 8,8-Bis(bromomethyl)-1,1-binaphthyl (1) in two steps in approx. 10% overall yield. The crystal structure of the intermediate phosphinoxide2 was determined. Attempts to prepare chelate complexes of3 with Ni(II) or Pd(II) failed.

     

ChemInform Abstract: A New Description of Samson′s Cd3Cu4 and a Model of Icosahedral i-CdCu.

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