ZEKE and Hole-Burning Spectroscopy of the Rotational Isomers of Resorcinol·CO

Abstract

Two rotational isomers of resorcinol‚CO were investigated using zero electron kinetic energy (ZEKE) photoelectron spectroscopy. Vibrational progressions and combination bands of the in-plane-bend, stretch and in-plane-wag intermolecular modes were observed in the spectra of each isomer. While the frequencies of these intermolecular modes were similar for both isomers, the Franck-Condon patterns for vibrational excitation were notably different, indicating that the isomers experience distinctive geometry changes upon ionization. Ab initio calculations at the MP2/6-31G* level of theory predict the existence of many stable isomers of resorcinol‚CO, with the three lowest energy minima corresponding to structures where the CO molecule binds through its carbon atom to one OH group of resorcinol. The calculations were used to assign the vibrational features in the ZEKE spectra and distinguish the rotational isomers observed.

The PFI-ZEKE photoelectron spectrum of m-fluorophenol and its aqueous complexes: Comparing intermolecular vibrations in rotational isomers

“…Only modest geometric changes are predicted to occur between the S 0 and D 0 states, with the primary changes involving a lengthening of the C 1 -C 2 bond (from 1.39-1.45 A ˚) and a shortening of the C 1 -O 12 bond (from 1.35 to 1.28 A ˚). A similar pattern was observed in the 3-methoxyphenol monomer, 11 and is associated with an increase in the keto-character of the phenol group in the ionic state. In addition, the C 5 -F 9 bond decreases upon ionization (1.33-1.29 A ˚), in line with a shift in electron density from the fluorine atom to the aromatic ring.…”

“…sented here indicate that the intermolecular bond is broadly similar in the S 0 and D 0 states of both cis-mfpÁH 2 O and trans-mfpÁH 2 O. It is useful in this context to compare the ZEKE spectra of mfpÁH 2 O with the spectra of resorcinolÁH 2 O, resorcinolÁCO and 3-methoxyphenolÁH 2 O,2,3,11 where much more distinctive Franck-Condon patterns of vibrational excitation were observed in the spectra of different isomers. It therefore appears that the structural differences between cis-mfpÁH 2 O and trans-mfpÁH 2 O are more modest than in the previously studied systems.Finally, it is of interest to compare the spectra of cis-mfpÁH 2 O and trans-mfpÁH 2 O with those of phenolÁH 2 O.…”

“…10 This level of theory has been demonstrated to be sufficient for assigning similar rotational isomers and interpreting their ZEKE spectra. 2,3,11,12 Harmonic frequencies were calculated to confirm that optimized structures correspond to local minima, and are presented unscaled. Spin unrestricted orbitals were employed in the D 0 state calculations, and the expectation value of the S 2 operator ranged from 0.7627 to 0.7991.…”

LIF and IR Dip Spectra of Jet-Cooled p-Aminophenol−M (M = CO, N2): Hydrogen-Bonded or Van der Waals-Bonded Structure?

“…12 The decrease in the OH stretching frequency is consistent with the hydrogenbonded structure proposed by Mu ¨ller-Dethlefs and co-workers. [8][9][10] A similar intermolecular hydrogen bond is observed in resorcinol (1,3-hydroxybenzene)-CO. 13 The existence of a weak intermolecular hydrogen bond is also suggested in tropolone-CO 2 . [14][15][16] These complexes have planar structures and the solvent molecule is located in the molecular plane of the aromatic or pseudoaromatic ring.…”

“…The existence of a weak intermolecular hydrogen bond is also suggested in tropolone−CO 2 . − These complexes have planar structures and the solvent molecule is located in the molecular plane of the aromatic or pseudoaromatic ring. In such planar complexes the interaction between the electric dipole moment of the OH or CO group of the chromophore and the electric quadrupole moment of the solvent molecule plays a crucial role to stabilize the complex. − ,− …”