High‐Resolution UV Spectroscopy of Molecular Complexes

Abstract

Information on the structure, the rigidity and the intermolecular potential of molecular complexes is essential to our understanding of the physical and chemical properties of molecular complexes. In this work we would like to demonstrate that rotationally resolved UV spectroscopy provides precise new information on these topics. In particular, the structure and van der Waals bond length of benzene‐X complexes (X = Ne, Ar, Kr, Xe, N2) have been experimentally determined. In the benzene‐N2 complex with its parallel‐stacked configuration, the two constituents, benzene and N2, can rotate against each other. Rotationally resolved vibronic van der Waals bands allow the clear assignment of the excited van der Waals vibrations. Their anharmonicity and the vibrationally averaged rotational constants provide basic information on the intermolecular potential. For the example of the benzene‐Ar2 trimer it is shown that isomeric structures exist that are rigid on the nanosecond time scale.

Rotational Coherence Spectroscopy of Aromatic-(Ar)n Clusters: Geometries of Anthracene-(Ar)n, 9,10-Dichloroanthracene-Ar, and Tetracene-Ar

“…Mostly, our RCS results, like the structure results from other laboratories (e.g., refs. [13][14][15][16][17][18][19][20], confirm these predictions. Particularly notable is the confirmationg of (a) the prediction from minimum energy calculations of two structural isomers of peryIene-(Ar)*' and (b) the assignment by band-shift rules of two vibronic bands to those isomers.'…”

Specific and nonspecific interactions in a molecule with flexible side chain: 2-phenylethanol and its 1:1 complex with argon studied by high-resolution UV spectroscopy

“…In this way, we are able to compare this result with our previous high-resolution spectroscopy results of clusters of benzene with Ar. 18,19 For the latter, we demonstrated that a ͑1͉1͒-type conformation, in which one Ar atom is on top of either side of the aromatic ring is favored over the ͑2͉0͒-type conformation even though the ͑2͉0͒ configuration may be stabilized by the Ar-Ar interaction. 18 In the benzene-Ar case both sites are completely equivalent.…”

The van der Waals rovibronic spectrum of p-difluorobenzene–Ar up to 125 cm−1 intermolecular energy: Assignment and character of van der Waals modes

“…5,31 Thus, the region of overlap suitable to compare with theoretical vdW rovibrational states calculated from the ab initio potential ͑well depth 429 cm Ϫ1 ͒ ͑Ref. 34͒ is small.…”

“…30 For benzene-Ar rotational resolution has been achieved for all three vdW vibronic bands known from low resolution spectroscopy. 5,31 The complete rotational analysis of these vibronic bands will be presented elsewhere 5,31 and compared with the calculations of the rovibratoric states. 22,23 In this work the high resolution spectra of several van der Waals vibronic bands of another model system, p-difluorobenzene-Ar ͑pDFB-Ar͒ are presented leading to a complete analysis of the vdW vibrations.…”