Photodehydrocyclizations of stilbene-like compounds VIII: Synthesis of hexaheliceno[3,4-c]hexahelicene
The synthesis of a new double helicene, hexaheliceno[3,4-c]hexahelicene, has been described. Of two possible diastereomers only one has been obtained. Presumably the product has the racemic configuration but this assignment is not yet definite.
Conformational preference of cis-1-aryl-2-(2-benzo[C]phenanthryl)-and cis-1-aryl-2-(3-phenanthryl)-ethenes
NMR measurements under different conditions (temperature, solvents used, presence of a shift-reagent) of cis- and trans-1-aryl-2-(2-benzo[c]phenanthryl)-ethenes reveal that an overcrowded conformation predominates in cis isomers. In the analogous 1-aryl-2-(3-phenanthryl)ethenes no clear conformational preference is found.
Dating of Historical Manuscripts Using Spectrometric Methods: A Mini-Review
An overview is provided of spectrometric methods useful for age estimation of historical manuscripts (medieval ones in particular), in order to confirm their authenticity. Individual methods (infrared and Raman spectroscopy, mass spectrometry, atomic emission spectroscopy, X-ray spectroscopy, and electron scanning microscopy) are discussed and examples of their application described. The following general strategy can be recommended for dating and/or authenticating of historical manuscripts. First of all, the pigment analysis should be carried out using Raman spectroscopy (distinguishing the period and modern pigments), followed by PIXE ink analysis (solving the question of ink homogeneity). Finally, the radiocarbon dating of the writing support, potentially supplemented by the ink dating using scanning Auger microscopy should be performed.