Twisted aromatics, 9-anthryl and 1-pyrenyl terpyridines organize into novel multi-directional ‘ladder-like’ motifs in the solid state

9-Anthryl and 1-pyrenyl terpyridines (1 and 2, respectively), key precursors for the design of novel fluorescent sensors have been synthesized and characterized by ¹H NMR, mass spectroscopy and X-ray crystallography. Twisted molecular conformations for each 1 and 2 were observed in their single crystal structures. Energy minimization calculations for the 1 and 2 using the semi-empirical AM1 method show that the ‘twisted’ conformation is intrinsic to these systems. We observe interconnected networks of edge-to-face CHπ interactions, which appear to be cooperative in nature, in each of the crystal structures. The two twisted molecules, although having differently shaped polyaromatic hydrocarbon substituents, show similar patterns of edge-to-face CHπ interactions.The presently described systems comprise of two aromatic surfaces that are almost orthogonal to each other. This twisted or orthogonal nature of the molecules leads to the formation of interesting multi-directional ladder like supramolecular organizations. A combination of edge-to-face and face-to-face packing modes helps to stabilize these motifs. The ladder like architecture in 1 is helical in nature.     

Scattering of hydrogen and helium from cesiated surfaces

Hydrogen and helium ion beams with energies of 1 to 15 keV have been reflected from Cs-covered Ni surfaces at normal incidence. For hydrogen there are surface peaks in the positive fraction and surface minima in the negative fraction, a result very different from that observed with other materials. The charged fractions of both hydrogen and helium depend on the thickness of the Cs layer. Some results for scattering of hydrogen at glancing angles are presented.     

A family of maximal subgroups containing the Sylow subgroups and some solvability conditions

Archiv der Mathematik -     

Studies in K-shell x-ray energy shift for a 2p spectator vacancy

We examine a simple model for calculating x-ray energy shifts due to outer atomic vacancies and present some case studies. We find that this model is a good supplement for the traditional approach to the problem.     

Residual velocity distributions in complete and incomplete fusion reactions

Theoretical simulation of residual velocity distributions at various mass windows for complete and incomplete fusion reactions have been done for the system⁴⁰Ar+²⁴Mg at the incident energies of 1100, 800 and 600 MeV. The comparison of the residual velocity distributions enables us to have a qualitative understanding about the relative contributions of the complete and incomplete fusion processes in intermediate energy heavy ion reaction.