Experimental and theoretical determination of the accurate CH/π interaction energies in benzene–alkane clusters: correlation between interaction energy and polarizability

Abstract

The CH/π interaction energies in benzene-alkane model clusters were precisely determined by laser spectroscopy and theoretical calculations. Two-color resonant two-photon ionization spectroscopy was employed to experimentally determine the interaction energies with isomer selectivity. High precision ab initio calculations were also performed to evaluate the CCSD(T) level interaction energies of various isomers at the basis set limit. Binary clusters of benzene with ethane, propane, n-butane, iso-butane, and cyclohexane were studied. The experimental interaction energies were well reproduced by the theoretical evaluations. The magnitude of the interaction energy clearly correlates with the average polarizability of the alkane moiety, demonstrating that the CH/π interaction energy is dominated by the dispersion interaction. On the other hand, the number of C-H groups in contact with the phenyl ring has no relation to the magnitude of the interaction energy, and it indicates that the role of the hydrogen atom in the CH/π interaction is essentially different from that in hydrogen bonds.

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

“…14 As reviewed by Grimme, 11 this can be generalized to molecules. Thus, the average molecular polarizabilityᾱ is often employed as a convenient proxy for the strength of dispersive interactions at medium to long range, 13,[44][45][46] although at short distances the approximation must break down.…”

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

“…1,2,4 The detailed nature of such interactions remains insufficiently understood, and may include aspects such as charge transfer contributions from the π system to C-H antibonding orbitals, as well as London dispersion. [5][6][7][8] Deeper understanding will benefit from quantitative characterization of systems such as the bimolecular complexes presented here.…”

“…20,21 Again a linear correlation with the average molecular polarizabilities was found. 6,7 Currently, we are extending measurement of D 0 (S 0 ) values to more complex and chemically relevant cases such as 1-naphthol (1-NpOH) with hydrocarbons. In these complexes, the 1-NpOH can act as a non-classical H-bond donor to the alkane, or the alkane can act as a CH/π donor.…”

Communication: The highest frequency hydrogen bond vibration and an experimental value for the dissociation energy of formic acid dimer

“…3 In considerably more complex systems with an aromatic chromophore, UV laser experiments can provide tight lower and upper bounds. [4][5][6] For formic acid dimer, the prototype of a double hydrogen bridge, neither of these approaches is feasible. However, there is an increasingly complete spectroscopic data set of the dimer at low temperatures.…”