摘要:

AbstractA simple technique for the preparation of anions of polycyclic aromatic hydrocarbons is described.1H and13C NMR spectra of dianions of pyrene and derivatives of pyrene are reported and discussed. The electron density is greatest at the carbon atoms in the perimeter of the dianions. The presence of an electron‐donating substituent at position 2 causes an increase in the charge at positions 1 and

ISSN:0165-0513    

DOI:10.1002/recl.19881070102

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA simple technique for the preparation of anions of polycyclic aromatic hydrocarbons is described.1H and13C NMR spectra of dianions of pyrene and derivatives of pyrene are reported and discussed. The electron density is greatest at the carbon atoms in the perimeter of the dianions. The presence of an electron‐donating substituent at position 2 causes an increase in the charge at positions 1 and

ISSN:0165-0513    

DOI:10.1002/recl.19881070103

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractAn improved synthesis for 5,10,15,20‐tetrakis(pentafluorophenyl)porphyrin, 5,10,15,20–tetrakis(2,4,6‐trimethylphenyl)porphyrin and 5,10,15,20‐tetrakis(2,6‐dichlorophenyl)porphyrin by an acid‐catalysed condensation of pyrrole and properly substituted aldehyde, followed by oxidation, is reported, with yields of up to 30% bei

ISSN:0165-0513    

DOI:10.1002/recl.19881070104

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe ESR spin‐probe technique has been used to investigate structural changes in didodecyldimethylammonium bromide (DDAB) bilayer vesicles (average diameter of 2000 and 3000 Å, respectively) around the phase transition temperature and in the presence of a fusogenic agent. Among several popular nitroxide spin‐probes, TEMPON‐DNPH is the only probe which binds effectively to the DDAB vesicles. Analysis of nitrogen hyperfine splitting constants (AN) revealed two different binding sites for TEMPON‐DNPH. At binding site I, the spin‐probe floats on the bilayer surface. At binding site II, the nitroxide moiety penetrates into the bilayer and experiences a more apolar microenvironment. The temperature dependence ofANindicates an increase in micropolarity at binding site II during the phase transition from a gel‐like to a liquid‐crystalline state of the bilayer. This effect is more pronounced for the larger vesicles. Estimates of the effective rotational correlation times suggest that the molecular tumbling of the probe increases with increasing temperature. No ESR spectral evidence was obtained for structural alterations in the vesicle bilayer under conditions of aggregation or fusion. This result is rationalized by assuming that binding site II is located too deeply in the vesicle bilayer to be affected by changes at the bilayer surface as they occur upon interaction with the f

ISSN:0165-0513    

DOI:10.1002/recl.19881070105

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA new cobaloxime‐type model for coenzyme B12has been synthesized. For this model strong steric repulsion between its dioxymethylene bridge and (one of) the axial ligands on cobalt presages enhanced rates of axial ligand exchang

ISSN:0165-0513    

DOI:10.1002/recl.19881070106

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19881070107

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19881070108

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19881070101

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY