A DFT Study on the Conformation, Properties of the Excited States, and Excimer's Formation of Tetraphenylcyclotetrasiloxane

The present study performed a DFT study on the conformation dependence of the properties of excited states and the excimer's formation for the tetramethyl tetraphenyl cyclotetrasiloxane. The conformations have little effect on the electronic structure of the ground state. The deformed phenyl group in the geometry of the excited state is the excimer-forming site. The energetically matched HOMO of the excited state with the LUMO of the ground state should cause an attraction to form an excimer. Most conformations are likely to form the excimer but have different contributions to the excimer formation. The interaction of the ground state with the excited state in the excimer has been described quantitatively, which shows that the most stable intermolecular arrangement is the stacked-eclipsed mode. The excimers display a broad excitation spectrum. The local excitation type is dominant during the excitation, and the charge transfer contributes to the excimer's stability.