Structural study of compounds modelling elementary polymer units, 4. Molecular and crystal structures of three isomers of 4,4′-bis(x-hydroxyphenoxy)octafluorobiphenyl

The paper presents an X-ray study of the isomers 4,4′-bis(2-hydroxyphenoxy)-, 4,4′-bis(3-hydroxyphenoxy)-, and 4,4′-bis(4-hydroxyphenoxy)octafluorobiphenyl, which are used as monomers in the synthesis of polyarylates. The molecular packing in crystals is characterized by intermolecular H-bonds, donor-acceptor and stacking interactions between the benzene rings of adjacent molecules, which results in considerable distortion of the molecular geometry. Notably, bending of biphenyl fragments accompanied by distortion of benzene ring planarity was observed, along with unusual conformations of oxydiphenylene fragments and distortions of bond angles at ipso-carbon atoms bonded to ether oxygen atoms.     

Structural study of compounds modelling elementary polymer units, 2. Molecular and crystal structures of bis[(3-pentafluorophenoxy)phenyl] 4,4′-oxydibenzoate and octafluorobiphenyl-4,4′-diylbis(oxy-1,3-phenylene) dibenzoate

This paper discusses the synthesis and X-ray studied of bis[(3-pentafluorophenoxy)phenyl] 4,4′-oxydibenzoate ( 10 ) and octafluorobiphenyl-4,4′-diylbis(oxy-1,3-phenylene) dibenzoate ( 11 ). These compounds are differently chosen models of the elementary unit of a polyarylate based on fluorinated bisphenols and aromatic dicarboxylic acids. Structures of 10 and 11 provide data on the conformational flexibility and the predominant was of arrangement of polyarylate chains.     

Structural study of compounds modelling elementary polymer units, 3. Molecular and crystal structure of 1,3,5-tris[4′-(C-o-carboranyl)biphenyl-4-yl]benzene

Following the studies on elucidating the main structural features of elementary units of polyphenylene-type polymers prepared by condensation of di- and monoacetylaromatic compounds, an X-ray structural analysis of 1,3,5-tris[4′-(C-o-carboranyl)biphenyl-4-yl]benzene ( 2 ) (systematic name: 1,3,5-tris[)1,2-dicarba-closo-dodecarborane( 12 )-1-yl(biphenyl-4-yl]benzene), which is the low-molecular-weight analog of one of the polymers in the given series, was performed. Compound 2 crystallizes as unstable solvate 1:1:1 with chloroform and benzene. The crystals are monoclinic, a = 17,060 Å, b = 20,220 Å, c = 18,448 Å, β = 102,79°, space group P2₁/n, Z = 4. Molecule 2 exhibits asymmetric conformation with substantial distortions of the linear geometry of polyphenylene units. The crystal is built of layers of molecules 2 , the solvate molecules being situated between these molecules in the channels and cavities with a population of 2/3. The benzene molecules participate in stacking-interaction with one of the carboranyl-substituted (i.e., the strongest electron-acceptor) benzene rings of the host molecule 2 ; chloroform molecules pack the channels without a specific interaction with the host molecules.     

Structural study of compounds modelling elementary polymer units, 6. X-ray structural and quantum-chemical investigation of the cis- and trans-isomeric models of the polynaphthoylenebenzimidazole elementary units

The X-ray structural investigation of the naphthoylenebis-(benzimidazole) ( 1 ) cis- and trans-isomers as models for the cis and trans elementary units of the corresponding poly(naphthoylene-benzimidazoles) (PNBI) was carried out. The correctness of the previous identification of the isomers was confirmed, and exact geometrical parameters of the PNBI elementary units (required, in particular, for the calculation of the Kuhn segment of PNBI) were determined. Quantum-chemical semi-empirical calculations of the ground and excited electronic states of the isomers were carried out. Both experimental and theoretical data confirm a larger stability of the planar π-conjugated structure of the trans-isomer in comparison with the cis-isomer in the ground as well as in the excited electronic state. Crystals of the cis- and trans-isomers obtained from trifluoroacetic acid solutions are the solvates of bis(trifluoroacetates) of diprotonated 1 with an extremely high content of the solvating trifluoroacetic acid. This peculiarity is favourable for modelling the main characteristics of the interaction between PNBI and protonic polar solvent molecules, viz. preferred types of H-bonding and a possibility of interaction of the electronic lone pairs of the solvent molecules with the π-electronic systems of the elementary units of PNBI by charge transfer complexes.     

Structural study of compounds modelling elementary polymer units, 1. Molecular and crystal structures of 1,3,5-tris(4-biphenylyl)-benzene and 1,3,5-tris[4-(C-o-carboranylmethyl)phenyl]benzene

For elucidating the structural features of elementary units of polyphenylene type polymers, prepared by polycondensation of di- and mono-acetylaromatic compounds, and X-ray study of two model compounds was performed, viz. 1,3,5-tris(4-biphenylyl)benzene (1) and 1,3,5-tris[4-(C-o- carboranylmethyl)phenyl]benzene (2) (diffractometer: R = 0,063 (1) and 0,061 (2) )· 1 0,5 C₆H₆ crystals were found to be rhombohedral, a = 20,168 (3), c = 13,678 (3) ǎ, space group R3c, Z = 6;2· CHCl₃ crystals are triclinic, a = 15,7528 (2), b = 12,7004 (6), c = 15,460 (2) Å, α = 109,97(1) β = 111,92(1) γ = 100,69 (2) °, space group P1, Z = 2. In the crystal the molecule 1 has a 32 symmetry with a propeller-like orientation of the biphenyl fragments with respect to the central ring (the rotation of the disubstituted benzene rings relative to the central one is 47,2° and relative to the therminal ones, it is 35,9°). In 2 the disubstituted benzene rings are rotated with respect to the central one by different values (dihedral angeles are 31,7 - 30,7, and 52,5°). In all benzene rings of both molecules a decrease of the endocyclic bond angles at the ipso-atoms is observed which in 2 depends on the dihedral angeles between the planes of bonded benzene rings. All there carboranylmethylphenyl fragements in 2 have the same conformation: the CH-group of the carborane skeleton “hangs” over the benzene ring plane. The crystal packing of 1 and 2 is characterized by sufficiently large cavities which are occupied by solvent molecules. In crystals of 2 the carborane parts of the molecules are associated into separate structural motives.     

New organic polymers, 4. Synthesis and characterization of polymers containing 3,3′-dioxo-5,5′-biindol-2,2′-diyl units

Polymers containing 3,3′-dioxo-5,5′-biindol-2,2′-diyl units were synthesized by high temperature polycondensation of 4,4′-diaminobiphenyl-3,3′-dicarboxylic acid (1) with ethylene dichloride and dibromide, 4-chloromethylbenzyl chloride and bromide, 4-chloromethyl-2,5-dimethylbenzyl chloride and bis(4-chloromethylphenyl) ether under different experimental conditions. These resulting polymers 5a–d were characterized by viscometric and IR Spectral studies and by TG in air. Kinetic parameters of their thermal degradation were evaluated.     

Polymers of carbonic acid, 5. Nematic polyurethanes derived from 4,4′-dihydroxybiphenyl and 4,4′-bipiperidine,ethylene-4,4′-bipiperidine or trimethylene-4,4′-bipiperidine

4,4′-Bipiperidine ( 3a ), 1,2-bis(4-piperidinyl)ethane ( 3b ) and 1,3-bis(4-piperidinyl)propane ( 3c ) were condensed with the dichloroformates of p-phenylene, 2-methyl-1,4-phenylene or 2,5-biphenylylene. Furthermore, two copolyurethanes were prepared either by mixing 3a and 3c or by mixing the dichloroformates for p-phenylene and 2,5-biphenylylene. Inherent viscosities between of 0,6 and 1,7 dl/g were found for the polyurethanes of 3c , but only values below 0,86 dl/g for those of 3a and 3b . The polyurethanes derived from hydroquinone or methylhydroquinone are semicrystalline polymers with a short-term thermostability up to 310°C. The polyurethanes deriving from phenylhydroquinone are amorphous with a thermostability up to 360°C. The homo-and copolyurethanes containing 4,4′-biphenylylene units form a smectic layer structure in the solid state and a nematic melt above the melting point.     

Identification of in vivo interaction between Hepatitis C Virus core protein and 5′ and 3′ UTR RNA

Here, we investigated the ability of the Hepatitis C Virus (HCV) core protein to interact specifically with the 5′ and 3′ untranslated regions (UTRs) of HCV using an in vivo cell-based translation inhibition assay. HCV core protein interacts weakly but specifically with the SLIII stem loop in the 5′ UTR in which the SLIIIb subdomain is the major determinant and the SL2 loop in the X region of the 3′ UTR. These results revealed for the first time in vivo interaction of the core protein with 5′ and 3′ UTRs involved in the viral life cycle. This system provides a useful tool for further investigating interactions between the HCV core protein and 5′ and 3′ UTRs.     

Synthesis and properties of para-linked aromatic polycondensates containing 3,3′,4,4′-biphenyltetracarboxylic-N,N′-bis(4-amino-biphenyl) diimide units

Two new diamino monomers based on 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) were synthesized and used in a low temperature polyamide polycondensation. High molecular weight homopoly(amide-imide)s and copoly(amide-imide)s were synthesized via in-situ silylation and investigated with respect to their solution, thermal, and film forming properties. All polymers are soluble in strong acids and most in amide type solvents. Inherent viscosities up to 7.4 dl/g in N-methyl-2-pyrrolidone (NMP)/LiCl were achieved. A methyl substitution in ortho-position to the imide group resulted in polymers possessing improved solubility and good thermal stability up to 500°C. Isotropic films can be prepared from solution.     

Fluorescence study on intermolecular complex formation between mesogenic 4,4′-biphenyldicarboxylate moieties of thermotropic liquid-crystalline polyesters with 5 and 6 methylene units

The change in intermolecular complex formation between mesogenic 4,4′-biphenyldicarboxylate moieties of thermotropic liquid-crystalline (LC) polyesters containing 5 and 6 methylene units (BB-n, n = 5, 6) was studied by fluorescence technique. BB-5 shows a crystalline, an S_CA, and an isotropic phase during heating. BB-6 shows a crystalline mixture of β- and γ-phase, a pure γ-phase, an S_A, and an isotropic phase during heating. The fluorescence of BB-n is confirmed to be due to the formation of an intermolecular ground-state complex between two mesogenic 4,4′-biphenyldicarboxylate moieties, and shows a wavelength shift of the fluorescence peak to lower wavelengths upon heating. This is because the increase in thermal fluctuation with increasing temperature induces a decrease in interaction between two 4,4′-biphenyldicarboxylate moieties. Because of the constancy of the fluorescence peak wavelength in the LC phase of BB-n, LC phases for S_CA and S_A type molecular arrangements of the LC polyester with mesogenic biphenyl moieties were proved to show fluorescence around 376 and 360 nm, respectively. However, the shift of the fluorescence peak wavelength to lower wavelengths upon heating has been observed for the first time in the present study. The change in molecular interaction between the mesogenic moieties of the LCPs during heating is shown to result in various fluorescence patterns.     

New polymer syntheses, 51. Thermotropic homopolyesters of 4,4′-dihydroxybiphenyl and substituted terephthalic acids

Polyesters were prepared from 4,4′-dihydroxybiphenyl and various aryloxyterephthalic acids or various disubstituted terephthalic acids. The aryloxyterephthalic acids were prepared by nucleophilic substitution of dimethyl nitroterephthalate with phenoxide ions. The disubstituted terephthalic acids were synthesized by double alkylation of diethyl 2,5-dihydroxyterephthalate with various alkyl bromides containing aromatic rings in the ω-position. The silyl method was primarily used for the polycondensation procedure. The resulting polyesters were characterized by elemental analyses, viscosity measurements, wide-angle X-ray scattering and differential scanning calorimetry measurements, and by optical microscopy. All polyesters proved to be semicrystalline, meltable materials forming a nematic phase above their melting points. The substituents of terephthalic acid enhance the solubility in organic solvents, so that all polyesters are soluble in CH₂Cl₂/trifluoroacetic acid mixtures and some of them even in hot N,N-dimethyl-formamide or methyl benzoate.     

New polymer syntheses, 52. Thermotropic copolyesters of various substituted terephthalic acids and 4,4′-dihydroxybiphenyl

Various copolyesters were synthesized from 4,4′-dihydroxybiphenyl and combinations of two or three differently substituted terephthalic acids. Various synthetic methods were studied; polycondensations of terephthaloyl dichlorides in dry pyridine gave the highest molecular weights. All copolyesters are semicrystalline and form a nematic melt above their melting points. Several copolyesters are well soluble in aprotic organic solvents, such as dichloromethane, N,N-dimethyl-formamide (DMF), methyl benzoate or chlorobenzene. A blend of such a soluble polyester (5 wt.-%) with bisphenol-A polycarbonate (poly(oxycarbonyl-oxy-1,4-phenyleneisopropylidene-1,4-phenylene)) was prepared from a cosolvent and various mechanical data were measured. These data were compared with those of an aromatic thermotropic polycarbonate.     

Synthesis of 3′,5′-bis(morpholinomethyl)-4′-hydroxy- and 3′,5′-bis(4-methyl-1-piperazinylmethyl)-4′-hydroxymethacrylanilide. Copolymerization and metal ion binding properties of monomers and copolymers

4′-Hydroxymethacrylanilide was modified by Mannich reaction with morpholine/formaldehyde and 1-methyl-piperazine/formaldehyde, respectively. The interaction of the resulting monomers 3 and 4 and their corresponding copolymers with acrylamide ( 5 and 6 ) with Cu^{2 +} ions was studied by photometric methods. Incorporation of the aminomethylated phenol derivatives 3 and 4 in an acrylamide-methylene diacrylamide network system was performed to yield a product which selectively adsorbs Cu²⁺ in the presence of Ni²⁺, Co²⁺, Cd²⁺ and Ca²⁺ ions.     

Molecular Structure of 113C‐C2H4/C3H6 Copolymers Prepared in the Presence of Half Sandwich Titanium Methyl – B(C6F5)3 Catalysts

Summary: Copolymers of propylene with 1¹³C‐ethylene (99% isotopic purity) have been prepared in the presence of Cp*Ti(CH₃)₃ – B(C₆F₅)₃ (I) or CpTi(CH₃)₃ – B(C₆F₅)₃ (II) (Cp = cyclopentadienyl, Cp* = pentamethylcyclopentadienyl). ¹³C NMR analysis confirms previous findings that propylene polymerization in the presence of I is highly regioselective and somewhat isoselective, while catalyst II produces regioblock polypropylene. In the presence of II, polymerization is slightly syndioselective and the average size of the primary regioblocks seems larger than that of the secondary ones. Moreover, secondary insertion seems more syndioselective than the primary.

¹³C NMR spectra of samples I.2 and II.2.     

Synthesis of Nε,N′ε-(pyromellitoyl)dilysine and its copper (II) chelate polymer

Synthesis of N_ε,N′_ε-(pyromellitoyl)dilysine ( 8 ) was carried out by reacting L -lysine with dimethyl pyromellitate ( 6 ) followed by thermal imidation. The obtained product 8 was reacted with Cu²⁺ ions to form a light blue chelate polymer ( 9 ). Model compounds, N_ε-phthaloyllysine ( 4 ) and its copper chelate complex 5 , were also synthesized by a similar process for comparison. IR spectra, optical and solubility properties of the monomer and its chelate polymer together with their corresponding model compounds were investigated. The thermal stability of chelate polymer 9 in acid solution of different pH value were also investigated.     

Aliphatic-aromatic polyamide-imides from diisocyanates, 1. 1H and 13C NMR study of polymer structure

The reaction of a diisocyanate and an asymmetric aliphatic-aromatic diacid containing a preformed imide group was studied in order to obtain polyamide-imides. It is shown in this paper that combined ¹H and ¹³C NMR spectrometry will permit the quantitative evaluation of the proportions of head-tail, head-head, tail-tail additions, provided the content of urea in the polymer is low. In order to obtain unequivocal assignments and to thoroughly characterize the NMR spectra of the polymer, several model compounds resembling the polymer backbone were synthesized. A model polymer was synthesized with the same purpose, and its ¹H and ¹³C NMR spectra fully assigned. Unexpected chemical functions in the polymer, like urea and carboxylic acid, can also be easily detected and quantified by NMR.     

Inhibitor studies of phage T4 wild-type and mutant DNA polymerase. IV. The substrate analog 3′-fluorothymidine 5′-triphosphate

The deoxythymidine5′-triphosphate (dTTP) analog 3′-fluorothymidine 5′-triphosphate (3′-FdTTP) inhibits DNA synthesis by T4 wild-type, L98 (mutator) and CB121 (antimutator) DNA polymerase. CB121 DNA polymerase is less sensitive by a factor of two than the L98 and T4⁺ enzymes. Inhibition is not due to incorporation of the analog into DNA. 3′-FdTTP acts competitively to the substrate dTTP. The CB121 polymerase exhibits a higher K_i to K_m ratio than the other two enzymes (5.3 vs. 3.3) and thus discriminates better between the substrate dTTP and its analog 3′-FdTTP. 3′-FdTTP inhibits the polymerase-associated 3′-5′ exonuclease activities to the same extent as their polymerase activities. The CB121 3′-5′ exonuclease activity is suppressed only half as much by 3′-FdTTP as by dTTP. The results are discussed in relation to the role of T4 DNA polymerase and its associated 3′-5′ exonuclease in determining the accuracy of DNA replication.