Rotational Isomerism in Fluorene Derivatives.

Rotational Isomerism in Bis-[/>-(3-Methyl-butyloxy)-phenyl]-thiourea

In case of Thiocarlidum (1) the thermoanalytical examination showed an endothermic transformation without loss of weight. This occured in samples recrystallized from cold polar solvents and the transformation proved to be non-reversible. The UV and IR spectra of the two samples differed characteristically and X-ray studies showed that the two modifications (in the following aand ßmodifications ...

Spectroscopic Studies of Dimethylamino Derivatives of Fluorene

2-dimethylamino-9-fluorenol and 2-dimethylamino-9(4'dimethylamino)phenyl-9-fiuorenol in polar solvents in the excited state undergo conformation changes in which two fluorescent isomers are created. The isomers (in the local excited (LE) and charge transfer (CT) configuration) possess separate fluorescence bands, one appearing from the S! (LE) state and the second f rom the intramolecular charg...

Rotational isomerism in Bis-(p-(3-methyl-butyloxy)-phenyl)-thiourea.

In case of Thiocarlidum (1) the thermoanalytical examination showed an endothermic transformation without loss of weight. This occured in samples recrystallized from cold polar solvents and the transformation proved to be non-reversible. The UV and IR spectra of the two samples differed characteristically and X-ray studies showed that the two modifications (in the following aand ßmodifications ...

Conformational Isomerism in l , Substituted Derivatives of 3 , 3 . Dimethylbutane

Bond-Stretch Isomerism in Tetrasilabicyclo[1.1.0]butane Derivatives

Bond-stretch isomerism is predicted not to occur in the parent compound Si4H6 and the substituted 1,3-di-tert-butyl derivative, although the existence of bond-stretch isomerism in the 1,3-dimethyl derivative is a possibility. Bulky bridgehead moieties induce a preference for a short Si−Si bridge bond, while a longer bridge bond length (2.840 Å at the MP2/6-31G(d,p) level) is predicted for the u...