Local Current Through Helical Orbitals

Traditional chemical research has given great information about the physical properties of molecules. This research provides understanding of how molecules work in the classical ways, but the limit is reached when molecules are used in a non-traditional way. Now molecules can be inserted in molecular junctions, which makes it possible to examine molecules in new ways. Recent theoretical work has shown that some linear molecules can have helical orbitals. Here the question of interest is whether the current density around these particular molecules are affected by the helical orbitals and the coupling of the electrodes. We show that the helical orbitals in combination with the coupling of the electrodes, indeed has an impact on the current and that the orbitals contribute to a circular current around these linear molecules. As the understanding of the currents behavior around the molecules expand, it paves the way for new chemical questions about how we can control the current. For example, how helical current may induce magnetic properties in non-magnetic molecules, and how chemical substituent can be used to impact these effects

Using Polarized Spectroscopy to Investigate Order in Thin-Films of Ionic Self-Assembled Materials Based on Azo-Dyes

Three series of ionic self-assembled materials based on anionic azo-dyes and cationic benzalkonium surfactants were synthesized and thin films were prepared by spin-casting. These thin films appear isotropic when investigated with polarized optical microscopy, although they are highly anisotropic. Here, three series of homologous materials were studied to rationalize this observation. Investigating thin films of ordered molecular materials relies to a large extent on advanced experimental methods and large research infrastructure. A statement that in particular is true for thin films with nanoscopic order, where X-ray reflectometry, X-ray and neutron scattering, electron microscopy and atom force microscopy (AFM) has to be used to elucidate film morphology and the underlying molecular structure. Here, the thin films were investigated using AFM, optical microscopy and polarized absorption spectroscopy. It was shown that by using numerical method for treating the polarized absorption spectroscopy data, the molecular structure can be elucidated. Further, it was shown that polarized optical spectroscopy is a general tool that allows determination of the molecular order in thin films. Finally, it was found that full control of thermal history and rigorous control of the ionic self-assembly conditions are required to reproducibly make these materials of high nanoscopic order. Similarly, the conditions for spin-casting are shown to be determining for the overall thin film morphology, while molecular order is maintained