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Abstract

Aromatic ethers such as diphenyl ether (DPE) represent molecules with different docking sites for alcohols leading to competing OH–O and OH–π interactions. In a multi-spectroscopic approach in combination with quantum chemical calculations the complex of DPE with tert-butyl alcohol (t-BuOH) is investigated in the electronic ground state (S₀) and the electronically excited state (S₁). FTIR, microwave as well as mass- and isomer-selective IR/R2PI spectra are recorded, revealing co-existing OH–O and OH–π isomers in the S₀ state. Surprisingly, they are predicted to be of almost equal stability in contrast to the previously investigated DPE–MeOH complex, where the OH–π structure is preferred by both theory and experiment. The tert-butyl group in t-BuOH allows for a simultaneous optimization of hydrogen-bonding and dispersion interactions, which provides a sensitive meeting point between theory and experiment. In the electronically excited state of DPE–t-BuOH, vibrational spectra could be recorded separately for both isomers using UV/IR/UV spectroscopy. In the S₁ state the same structural binding motifs are obtained as in the S₀ state with the OH–O bond being weakened for the OH–O arrangement and the OH–π interaction being strengthened in the case of the OH–π isomer compared to the S₀ state.