摘要:

AbstractThe luminescence processes in several rare‐earth compounds are discussed,viz.sensitization, one‐step energy transfer, multi‐step energy transfer (migration) and trapping. Results are given for compounds containing Eu3 +, Tb3+and Gd3+. The dimensionality of the rare‐earth sublattice (three, two or one) influences the migration and examples are presented. The case of Eu3+is the first for which one‐, two‐ and three‐dimensional migration has been observed for one and the same optically active ion. Gadolinium compounds can be applied in luminescent lamps, where they improve the lamp output

ISSN:0165-0513    

DOI:10.1002/recl.19861050502

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractA 300‐MHz1H NMR variable‐temperature study of the 1′‐phosphorylated trigonal‐bipyramidal (TBP) tetrahydropyran‐2‐methyl model compound4is reported. For this compound, in which both the equatorial and axial sites undergoing phosphorus pseudorotation bear a tetrahydro‐pyran‐2‐methyl group, a precise conformational analysis of the C(1′)‐C(2) bond is possible. The thermodynamic parameters which result from this analysis allow the assignment of the proton resonating at low field as H(1′). It is shown that, for the group situated axially in the PvTBP, an enhanced gauche (‐) population [O(1′) and O(1)trans‐situated] occurs around C(1′)‐C(2) (290 K, 59%; 230 K, 74%) as compared to the corresponding Pivcompound3(298 K, 10%). The same conformational transmission is observed for 6‐phosphorylated pyranosides, but in this case is found to depend upon the configuration at C(4). It appears that 6‐phosphorylated methyl 2,3,4‐tri‐O‐methyl‐α‐D‐galactopyranoside shows a conformational change around C(5)‐C(6) towards a higher g−population, going from 6‐Pivto 6‐PvTBP, which is absent in the corresponding 6‐phosphorylated methyl 2,3,4‐tri‐O‐methyl‐α‐D‐glucopyranoside. Apparently, th

ISSN:0165-0513    

DOI:10.1002/recl.19861050503

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractNitration of 2‐tert‐butyl‐ and 2,7‐di‐tert‐butylpyrene affords molecules with severely hindered nitro groups. A nitro grouporthoto atert‐butyl group is twisted at least 82° out of the plane of the aromatic nucleus. The lack of interaction between the hindered nitro group and the aromatic system is reflected in the chemical behaviour, as well as in the spectroscopic properties, of these nitro derivatives.Upon fragmentation in the mass spectrometer, thetert‐butyl group is always replaced by a hydrogen atom. Nitro groups are only replaced by a hydrogen atom if they areorthoto a

ISSN:0165-0513    

DOI:10.1002/recl.19861050504

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractEther complexes of trialkylaluminium compounds react with α‐chloro‐nitroso compounds via radicals which can abstract hydrogen from various solvents. In the presence of olefinic solvents, radical addition to the double bond also takes place.When the trialkylaluminium compounds are not complexed by ethers, they react with α‐chloro‐nitroso compounds predominantly via heterolytic pro

ISSN:0165-0513    

DOI:10.1002/recl.19861050505

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19861050506

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractLanthanide induced shifts for the17O,13C and1H nuclei of an aqueous solution of glycolate show that the Ln(glycolate)3(D2O)3complex contains 9 coordinating oxygens situated on a distorted tricapped trigonal prism. The three capping positions are occupied by carboxylate oxygens, the prismatic triangles by either D2O or α‐

ISSN:0165-0513    

DOI:10.1002/recl.19861050507

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19861050501

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY