The Structure of Diphenyl Ether-Methanol in the Electronically Excited and Ionic Ground States: A Combined IR/UV Spectroscopic and Theoretical Study.

Diphenyl ether offers competing docking sites for methanol: the ether oxygen acts as a common hydrogen-bond acceptor and the π system of each phenyl ring allows for OH-π interactions driven by electrostatic, induction, and dispersion forces. Based on investigations in the electronic ground state (S0 ), we present a detailed study of the electronically excited state (S1 ) and the ionic ground state (D0 ), in which an impact on the structural preference is expected compared with the S0 state. Dispersion forces in the electronically excited state were analyzed by comparing the computed binding energies at the coupled-cluster-singles (CCS) and approximate coupled-cluster-singles-doubles levels of theory (CC2 approximation). By applying UV/IR/UV spectroscopy, we found a more strongly bound OH-π structure in the S1 state compared with the S0 state, in agreement with spin-component-scaled CC2 calculations. A structural rearrangement into a non-hydrogen-bonded structure takes places upon ionization in the D0 state, which was revealed by using IR photodissociation spectroscopy and confirmed by theory.