Towards the assignment of the REMPI spectrum of Ph₂O using CIS and TD-DFT methods

Abstract

Tentative assignment of the low-lying vibrational features of the first electronic excited singlet-state S 1 of diphenyl ether (Ph 2 O), obtained from resonance-enhanced multiphoton ionisation (REMPI) spectroscopy, is performed using CIS and timedependent density functional theory (TD-DFT) methods. The potential energy surfaces, regarding the rotation of the phenyl rings relatively to the C-O-C plane, are obtained at the B3LYP/6-31G(d) level of theory, for the ground-state of neutral and cationic Ph 2 O and for its first excited singlet state. The torsional barriers of the ground state of diphenyl ether were studied by means of quantum-chemical perturbations of increasing accuracy and an extrapolation to the complete basis set limit and full configuration interaction (FCI) was performed through the use of correlation consistent basis sets and the continued fraction method. The first adiabatic ionisation energy (AIE) of the twist conformer is computed at 8.60 eV in the FCI limit, much higher than the experimental results of Terlouw et al. (8.09 ± 0.03 eV) and Paiva et al. (7.8 ± 0.1 eV). The B3LYP result of 7.82 eV is, however, in reasonable agreement with the result of Paiva et al. The first singlet excitation energy for the twist conformation is found to be 5.5 eV at the CIS/6-311++G(d,p) level of theory. Some features of the experimental REMPI spectrum, previously obtained by one of the authors, are explained and a new insight on the ionisation energy of diphenyl ether is presented.

Structures and internal dynamics of diphenylether and its aggregates with water

“…Indications of this have been reported before using different spectroscopic techniques, such as resonance-enhanced multi-photon ionization and NMR spectroscopy as well as quantum-chemical computations. [14][15][16][17][18][19][20][21] However, once the molecule is complexed with another molecular species, internal dynamics are often not observed anymore, as in the case of DPE-CH 3 OH, DPE-tBuOH, DPE-adamantol, and also the DPE dimer. 22 The reason is two-fold: in many cases the complexing molecules sterically hinder and thus "lock" the structure of the flexible molecule to a certain conformation, but a more general reason is that the symmetry is often broken upon complexation.…”

“…The PES of DPE was computed previously. 13,15,17,18,21 It was recomputed here to generate the respective structures for the internal dynamics analysis. Our new PES is given in Figure 1(a).…”

Aromatic embedding wins over classical hydrogen bonding – a multi-spectroscopic approach for the diphenyl ether–methanol complex

“…Therefore, a microscopic understanding of the docking preferences of alcohols to DPE may eventually be beneficial for solvent design in catalysis. DPE in the gas phase was spectroscopically investigated previously using resonance-enhanced multi-photon ionization, 19,20 but a detailed understanding of its conformational flexibility and rich internal dynamics is still missing and will be tackled in a separate study. DPE provides a number of plausible binding sites and pathways for methanol, and it is the aim of the present study to elucidate what type of bonding is most preferred and why.…”