Maity Surajit, Ottiger Philipp, Balmer Franziska A, Knochenmuss Richard, Leutwyler Samuel
Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3000 Bern, Switzerland.
J Chem Phys. 2016 Dec 28;145(24):244314. doi: 10.1063/1.4973013.
Intermolecular dissociation energies D(S) of the supersonic jet-cooled complexes of 1-naphthol (1NpOH) with cyclopentane, cyclohexane, and cycloheptane were determined to within <0.5% using the stimulated-emission pumping resonant two-photon ionization method. The ground state D(S) values are bracketed as 20.23±0.07 kJ/mol for 1NpOH⋅cyclopentane, 20.34±0.04 kJ/mol for 1NpOH⋅cyclohexane, and 22.07±0.10 kJ/mol for two isomers of 1NpOH⋅cycloheptane. Upon S→S excitation of the 1-naphthol chromophore, the dissociation energies of the 1NpOH⋅cycloalkane complexes increase from 0.1% to 3%. Three dispersion-corrected density functional theory (DFT) methods predict that the cycloalkane moieties are dispersively bound to the naphthol face via London-type interactions, similar to the "face" isomer of the 1-naphthol⋅cyclopropane complex [S. Maity et al., J. Chem. Phys. 145, 164304 (2016)]. The experimental and calculated D(S) values of the cyclohexane and cyclopentane complexes are practically identical, although the polarizability of cyclohexane is ∼20% larger than that of cyclopentane. Investigation of the calculated pairwise atomic contributions to the D2 dispersion energy reveals that this is due to subtle details of the binding geometries of the cycloalkanes relative to the 1-naphthol ring. The B97-D3 DFT method predicts dissociation energies within about ±1% of experiment, including the cyclopropane face complex. The B3LYP-D3 and ωB97X-D calculated dissociation energies are 7-9 and 13-20% higher than the experimental D(S) values. Without dispersion correction, all the complexes are calculated to be unbound.
采用受激发射泵浦共振双光子电离方法，将1-萘酚（1NpOH）与环戊烷、环己烷和环庚烷形成的超声速喷射冷却复合物的分子间解离能D(S)测定至误差在<0.5%以内。基态D(S)值范围为：1NpOH·环戊烷为20.23±0.07 kJ/mol，1NpOH·环己烷为20.34±0.04 kJ/mol，1NpOH·环庚烷的两种异构体为22.07±0.10 kJ/mol。对1-萘酚发色团进行S→S激发时，1NpOH·环烷烃复合物的解离能增加0.1%至3%。三种色散校正密度泛函理论（DFT）方法预测，环烷烃部分通过伦敦型相互作用分散地结合到萘酚面上，类似于1-萘酚·环丙烷复合物的“面”异构体[S. Maity等人，《化学物理杂志》145, 164304 (2016)]。环己烷和环戊烷复合物的实验和计算D(S)值实际上是相同的，尽管环己烷的极化率比环戊烷大约20%。对计算得到的D2色散能的成对原子贡献进行研究表明，这是由于环烷烃相对于1-萘酚环的结合几何结构的细微细节所致。B97-D3 DFT方法预测的解离能在实验值的±1%左右，包括环丙烷面复合物。B3LYP-D3和ωB97X-D计算得到的解离能比实验D(S)值高7 - 9%和13 - 20%。没有色散校正时，所有复合物计算结果均为未结合状态。
