Nanosized molecular propellers by cyclodehydrogenation of polyphenylene dendrimers.

In a polymer analogous approach, large dendritic oligophenylenes containing benzene and tetraphenylmethane cores are transformed via oxidative cyclodehydrogenation to novel propeller-shaped molecules with large polycyclic aromatic hydrocarbon units as "blades". Structure analysis is performed by a combination of MALDI-TOF mass spectrometry, UV/vis, fluorescence, and Raman spectroscopy using solid-state sample preparation methods. These methods are also utilized to determine the degree of the cyclodehydrogenation reaction.

A Chemically and Electrochemically Switchable [2]Catenane Incorporating a Tetrathiafulvalene Unit.

A mechanical switch in a [2]catenane, made up of a cyclobis(paraquat-p-phenylene) tetracation interlocked with a macrocyclic polyether containing a redox-active tetrathiafulvalene (TTF) unit and a 1,5-dioxynaphthalene ring system, can be thrown either chemically or electrochemically. The neutral TTF unit resides "inside" the tetracationic cyclophane in the reduced state and "alongside" it in the oxidized species (TTF+ / TTF2+ ). Switching between the reduced (I4+ ) and oxidized state (I5+ (I6+ )) is accompanied by a dramatic color change.