Accurate dissociation energies of two isomers of the 1-naphthol⋅cyclopropane complex

Abstract

Articles you may be interested inInfluences of the propyl group on the van der Waals structures of 4-propylaniline complexes with one and two argon atoms studied by electronic and cationic spectroscopy J. Chem. Phys. 143, 034308 (2015); 10.1063/1.4927004The weak hydrogen bond in the fluorobenzene-ammonia van der Waals complex: Insights into the effects of electron withdrawing substituents on π versus in-plane bonding J. Chem. Phys. 126, 154319 (2007) The 1-naphthol·cyclopropane intermolecular complex is formed in a supersonic jet and investigated by resonant two-photon ionization (R2PI) spectroscopy, UV holeburning, and stimulated emission pumping (SEP)-R2PI spectroscopy. Two very different structure types are inferred from the vibronic spectra and calculations. In the "edge" isomer, the OH group of 1-naphthol is directed towards a C-C bond of cyclopropane, the two ring planes are perpendicular. In the "face" isomer, the cyclopropane is adsorbed on one of the π-aromatic faces of the 1-naphthol moiety, the ring planes are nearly parallel. Accurate ground-state intermolecular dissociation energies D 0 were measured with the SEP-R2PI technique. The D 0 (S 0 ) of the edge isomer is bracketed as 15.35 ± 0.03 kJ/mol, while that of the face isomer is 16.96 ± 0.12 kJ/mol. The corresponding excited-state dissociation energies D 0 (S 1 ) were evaluated using the respective electronic spectral shifts. Despite the D 0 (S 0 ) difference of 1.6 kJ/mol, both isomers are observed in the jet in similar concentrations, so they must be separated by substantial potential energy barriers. Intermolecular binding energies, D e , and dissociation energies, D 0 , calculated with correlated wave function methods and two dispersion-corrected density-functional methods are evaluated in the context of these results. The density functional calculations suggest that the face isomer is bound solely by dispersion interactions. Binding of the edge isomer is also dominated by dispersion, which makes up two thirds of the total binding energy. Published by AIP Publishing. [http://dx

Intermolecular dissociation energies of dispersively bound 1-naphthol⋅cycloalkane complexes

“…12,[23][24][25][26][27][30][31][32] Detailed descriptions have been reported elsewhere. 12,28 Briefly, a pulsed pump laser (∼ 5 ns pulse width) is fixed at the S 0 → S 1 electronic origin (0 0 0 band) and excites the jet-cooled M·X complex from the vibrationless S 0 to the vibrationless S 1 state.…”

“…[23][24][25][26][27][28] Mass-selective one-color resonant two-photon ionization (R2PI) spectra were recorded using a 120 cm linear time-of-flight mass spectrometer. To identify isomeric complexes of the same mass, hole-burning spectroscopy was performed.…”

“…34 The D 0 (S 0 ) values for two different 1NpOH·cyclopropane complexes calculated with this method agreed with the ex-perimental dissociation energy to within 1.1%. 28 In addition, we employed the B97-D3 method 35 with the def2-TZVPP basis set, as implemented in TURBOMOLE 7.0, and the Chai and Gordon long-range and dispersion-corrected ωB97X-D functional 36 with the 6-31++G(d,p) basis set, as implemented in Gaussian 09. 37 The latter two methods gave good results in a study of large π-stacked complexes.…”

“…The calculated structures of the edge and face isomers of the 1NpOH·cyclopropane complex have been previously reported. 28 For 1NpOH·cyclopentane, two face isomers are predicted, related by rotation or pseudorotation of the cyclopentane. The dissociation energies differ by only 0.3 kJ/mol.…”

“…Below, we will assume that the B97-D3 and B3LYP-D3 ordering is correct. The interconversion barrier between the two predicted face isomers of the 1NpOH·cyclopropane complex is only 1.4 kJ/mol, 28 so it is likely that the isomerization barriers between the four face isomers of 1NpOH·cycloheptane are in the range of 1 − 2 kJ/mol and can be surmounted even at late stages of the supersonic expansion. This would also explain why so far only two isomers have been experimentally observed.…”