On the electronic structure of barrelene‐based rigid organic donor‐acceptor systems. An INDO model study including solvent effects

We present an INDO/S molecular‐orbital investigation of organic molecules containing a barrelene moiety that provides a rigid link between an aromatic donor and a maleic ester acceptor group. Molecules of this type have recently been synthesized and characterized spectroscopically. We discuss the ground state and various excited states both in vacuo and in solution. Solvent effects are incorporated by use of an electrostatic cavity model which is not restricted to a spherical cavity, but allows for a cavity shape that is adapted to the solute molecule. The calculations indicate low‐lying charge‐transfer (CT) excitations in the region of the first aromatic transitions, even in the gas phase. © 1992 John Wiley & Sons, Inc.