Conformational changes upon excitation in PYDAPX-based charge-transfer complexes

We present quantum mechanical (QM) calculations which propose a conformational structure of the new pyrene-based, organic glass constituent PYDAPX doped with 2,4,7-tri-nitro-fluorenone (TNF). PYDAPX is a photo-conducting substance. Upon doping with 2,4,7-Tri-Nitro-Fluorenone PYDAPX shows a threefold increase in its photoconductivity. Calorimetric and spectroscopic data indicate the formation of a molecule complex. Density functional theory and MNDO-based calculations have been carried out to clarify the geometry of the complex. It can be shown that a small conformational change happens upon photo-excitation. Further computational efforts indicate that the conformational rearrangement is even larger when examining different TNF configurations. The effect is a general phenomenon due to the electron's kinetic energy and expected to appear especially on conjugated polymers.