Polyaromatic ether-ketones from o,o′-disubstituted diphenyl ethers

Polyaromatic ether-ketone resins with potentially open structures which are possibly useful as membranes were prepared from diphenyl ethers with alkyl substitutions in the ortho positions and isophthaloyl or terephthaloyl chloride by Friedel–Craft-type polymerization. These polymers are soluble in such solvents as DMF, DMA, and CHCl₃, and can be cast into colorless transparent films.     

Preparation and characterization of aromatic copolyesters containing the o,o′-biphenylene ring system

Poly[oxy-2,2′-diphenyleneoxyisophthaloyl-b-oxy(2-methyl-1,3-phenylene)oxyterephthaloyl] I, poly[oxy-2,2′-diphenyleneoxyterephthaloyl-b-oxy(2-methyl-1,3-phenylene)oxyterephthaloyl] II, poly(oxy-2,2′-diphenyleneoxyisophthaloyl-b-oxy-2,2′-diphenyleneoxyterephthaloyl) III, poly[oxy-2,2′-diphenyleneoxyterephthaloyl-b-oxy(2-methyl-1,4-phenylene)oxyterephthaloyl] IV, poly[oxy2,2′-diphenyleneoxyterephthaloyl-b-oxy(2-chloro-1,4-phenylene)oxyterephthaloyl] V, poly[oxy-2,2′-diphenyleneoxyterephthaloyl-co-oxy(2-chloro-1,4-phenylene)oxyterephthaloyl] VI, and poly[oxy-2,2′-diphenyleneoxyterephthaloyl-co-oxy(2-methyl-1,4-phenylene)oxyterephthaloyl] VII have been synthesized and characterized. Random copolyester VI appears to form a birefringent fluid phase above the melting temperature.     

Über die spektrale Sensibilisierung von Zinkoxid: I. Sorptionsverhalten von o,o′-Dihydroxyazofarbstoffen

o,o′-Dihydroxyazo compounds are spectral sensitizers for the photosemiconductor properties of zinc oxide. It is shown that 1-(2-hydroxyphenylazo-)-2-naphthol (II) forms a 1:1 Zn complex on the surface of ZnO particles if adsorbed from toluene solution. With most samples of ZnO a Langmuir type adsorption isotherm is obtained. The concentration of the dye at saturation relative to the BET surface of the ZnO particles correponds to a slightly oblique edge-on arrangement of the dye molecules on the surfaces. In the case of ZnO pretreated with propionic acid and having taken up dye in excess of a monolayer, it can be shown by electron microscopy that tail-like complexes (zinc: dye ratio = 1:1) are formed, and that these complexes contain zinc which was originally on the particle surfaces.     

Lanthanide shift reagents as a structural probe for alkenes

The utility of LSR for structural analysis of the AG⁺ complexes of 3,7-dimethylenebicyclo[3.3.1]nonane and its derivatives is demonstrated.     

Molecular modeling,NMR spectroscopy,and conformational analysis of 3′,4′-anhydrovinblastine

The assignment of the proton spectrum of 3′,4′-anhydrovinblastine is reported. Assignments are made for several protons for which only approximate assignments were available previously. Homonuclear TOCSY and ROESY spectra were utilized in conjunction with HMQC and HMBC spectra in making the assignment. Correlations in the ROESY spectrum suggested a preferred conformation of the cleavamine (upper) portion of 3′,4′-anhydrovinblastine in which the 21-methyl of the 20/21 ethyl group of the vindo-line (lower) portion is in proximity to the H14′ and 16′-NH resonances of the cleavamine. In a Monte Carlo search, the global minimal energy structure was oriented with the 16-methoxyl group oriented toward the H14′ and 16′-NII resonances. Two other structures, the second and tenth lowest in energy, 0,2 kJ and 8 kJ higher in energy, respectively, brought the 21-methyl group in proximity to the H14′ and 16′-NH resonances in a fashion consistent with the ROESY data. The preferred solution conformation of 3′,4′-anhy-drovinblastine is consistent with the reported solution conformation of vinblastine.     

Carbon-13 nuclear magnetic resonance spectra. XVI—lanthanide induced signal shifts of diastereotopic 13C nuclei as a probe for a conformational equilibrium

The ¹³C NMR signals of the two methyl groups in 4-hydroxy-1-isopropyl-2-oxaadamantane are anisochronous in the presence of Yb(fod)₃. This is interpreted in terms of the different populations of three rotational conformers.     

1H- and 13C-NMR. Studies of some metal complexes of o,o′-dihydroxyazobenzenes

The aromatic ¹H- and ¹³C-NMR. spectra of some metal complexes of o, o′-dihydroxyazobenzenes are shown to be useful in distinguishing the two possible isomers (acolar and discolar) stemming from the non equivalence of the two ligating azo nitrogen atoms. The ortho aromatic carbon atoms, C(6) and C(12) experience relatively large upfield shifts between 12.8 and 15.7 ppm when the adjacent nitrogen atom is coordinated. The protons attached to these carbon atoms are shifted downfield. The values ⁿJ (¹⁵N, ¹³C) for the ligand 2,2′-dihydroxy-3-methyl-4′-chloro-5-(t-butyl)-¹⁵N-azobenzene are reported.     

The use of chiral shift reagents in an NMR study of 2,2′,6,6′-tetrasubstituted biphenyls

The determination of the enantiomeric composition of 2,2′,6′6′-tetrasubstituted biphenyls using ¹H NMR spectroscopy, in combination with chiral lanthanide shift reagents, has been studied. In general, the S compounds give largeer induced shifts than the correspondind R isomers when d-camphor derived shift reagents are used.     

15N-NMR. A Method for Assigning Structure in Complexes of Unsymmetrical o,o′–Dihydroxydiarylazo–Ligands

The ¹⁵N-NMR. parameters of some Pt(II)complexes of unsymmetrical o, o′-dihydroxydiarylazo-ligands are shown to be useful in the solution of subtle structural problems.     

N,N′,N′′,N′′′‐Tetraethylterephthalamidinium bis(tetrazolate)

The crystal structure of the title 2:1 salt of tetrazole and a substituted terephthal­amidine, C₁₆H₂₈N₄²⁺·2CHN₄^?, contains an infinite network of hydrogen bonds, with short N?N distances of 2.820 (2) and 2.8585 (19) Å between the tetrazolate anion and the amidinium cation. Involvement of the lateral N atoms of the tetrazole in the hydrogen bonding appears to be a typical binding pattern for the tetrazolate anion.     

Synthesis,Characterization, and Crystal Structure of Complexes of Lanthanide Picrates with N,N,N′,N′-tetraphenyl-3,6-dioxaoctanediamide

Lanthanide picrate complexes with the ligand N,N,N′,N′-tetraphenyl-3,6-dioxaactanediamide (tdd): [Ln(Pic)₃(tdd)] (Ln = La, Nd, Eu, Tb, Er) have been prepared in a nonaqueous medium and characterized by elemental analysis, conductivity measurements, IR, and ¹H-NMR spectra. The crystal structures of the complexes for Ln = Nd and Er were determined. The early lanthanide, Nd^III, crystallizes as the nona-coordinate complex [Nd(Pic)₃(tdd)]. 2 CH₃CN in the monoclinic space group P2₁n with a = 11.384(2), b = 18.805(4), c = 27.526(5) Å, β = 99.41(1)°, V = 5832(2) ų, and D_c = 1.58 gcm^?3 for Z = 4. The structure was refined to R = 0.0505, based on 4772 observed Deflections. The late lanthanide, Er^III, forms an octa-coordinate complex [Er(Pic)₃(tdd)]; crystals are triclinic, P1, with a = 12.449(2), b = 17.065(2), c = 26.243(4) Å, α = 72.12(1), β = 87.86(1), γ = 84.60(1)°, V = 5282(1) ų, and D_c = 1.68 g cm^?3 for Z, = 4. The structure was refined to R = 0.0469, based on 10666 observed reflections, The results reveal that tdd forms a ring-like structure with its four O-atoms, coordinating to the metal ions as multidentate ligand, together with one O-atom of the bidentate picrate. The structure of the complexes is greatly affected by the ionic radius due to participation of the picrates in coordination.     

Equilibrium constant for coordinative polymerization of an o,o′-dihydroxyazobenzene derivative with Ni(II) ion in water

Equilibrium constant (K_CP) for coordinative polymerization is measured for the first time. Constant K_CP is defined as [L]_cp/[M][L], where [L]_cp represents the concentration of the ligand present in the coordination polymer. Plot of absorbance changes measured for 3, a water-soluble derivative of o,o′-dihydroxyazobenzene, against the concentration of Ni(II) ion indicates formation of a 1 : 1-type complex in water at pH 7.74 and 25°C when Ni (II) is added in excess of 3. The 1 : 1-type complex can be either Ni 3, the monomeric complex, or (Ni 3 )_n, the coordination polymer. The equilibrium constant for formation of the 1 : 1-type complex is estimated as 10^13.10 by using UO₂²⁺ ion as the competing metal ion. For the Ni(II) complex of an o,o′-dihydroxyazobenzene derivative attached to poly(ethylenimine), the formation constant is estimated as 10^5.36. Due to the structure of the polymer, possibility of coordinative polymerization is excluded for the polymer-based ligand. The much greater equilibrium constant for formation of the Ni(II) complex of 3, therefore, indicates formation of (Ni 3 )_n instead of Ni 3. The value of K_CP for (Ni 3 )_n shows that only 10⁻⁷% of the initially added 3 is left unpolymerized when Ni(II) is added in excess of 3 by 10⁻⁴ M. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1825–1830, 1997