A porphyrin macrocyclic square is efficiently prepared by a dynamic combinatorial approach to olefin metathesis and shown by scanning tunneling microscopy (STM) to self-assemble into highly ordered arrays on a graphite surface.

We describe the syntheses and properties of five semi-rigid donor−(σ-bridge)−acceptor (D−σ−A) compounds. These compounds, which are candidates for incorporation in materials, have aniline-type donors and (mixed) cyano-and alkoxycarbonyl-1,1-difunctionalized vinyl acceptors that are separated by a four-σ-bond bridge. Their electronic properties were studied by means of photoelectron spectroscopy in combination with ab initio MO calculations, cyclic voltammetry, UVVis absorption spectroscopy, (time-resolved) fluorescence spectroscopy, and time-resolved microwave conductivity (TRMC). We found that these D−σ−A compounds exhibit a