Structures and vibrations of p-dimethoxybenzene conformers in the S0 and S1 states studied by ab initio calculations and resonant two-photon ionization spectroscopy

The Absorption Spectrum of Anisole and the Anisole/CO2 1:1-Cluster. The Influence of Intermolecular Interaction on Intramolecular Vibrations

The S 1(1 B 2) ← S 0(1 A 1) electronic transition of anisole and the anisole/CO2 aggregate cooled in a supersonic free jet has been investigated in detail using REMPI spectroscopy and quantumchemical model calculations. The 42 intramolecular modes of anisole in the 1 S 1 state are assigned. Some previous assignments of modes of anisole in the 1 S 1 state have been improved, some of the assignments are still tentative. The origin of the corresponding electronic transition in the 1:1-aggregate is blueshifted by 117cm−1 versus the 0-0 transition of anisole, the origine in the 1:2-agreggate is redshifted by 216cm−1. Probably a second conformer of the 1:1-aggregate is formed in the molecular beam. 36 fundamental modes of the anisole/CO2 1:1-cluster out of possible 46 intramolecular modes are assigned. Spectral shifts of the fundamental modes in the 1 S 1 state of anisole/CO2 due to the aggregation have been observed. The intermolecular modes and their binary combinations with intramolecular modes have been analyzed.

The absorption spectra of anisole-h8, anisole-d3 and anisole-d8. The assignment of fundamental vibrations in the S0and the S1states

The REMPI spectra of anisole-h8, anisole-d3 and anisole-d8 have been measured. The assignment of the fundamental vibrations of anisole in the S(1) state is supported by quantum chemical model calculations, the isotopic shifts, the comparison with the frequencies of corresponding vibrations in other monosubstituted benzenes, especially phenol, and the overtones, combinations and progressions observed in the spectrum of anisole-h8. The frequencies of the 42 fundamental vibrations of anisole in the S(1) state are evaluated and compared with the frequencies of the corresponding vibrations in the electronic ground state. Some assignments given earlier in the literature have been revised.

Site-specific H/D exchange of p-methoxyphenol studied by resonant two-photon ionization and mass-analyzed threshold ionization spectroscopy

The origin of the S(1) <-- S(0) transition (E(1)) and the adiabatic ionization energy (IE) of cis-p-methoxyphenol-d(1)-OD are determined to be 33 660 and 62 302 cm(-1), whereas those of cis-p-methoxyphenol-d(1)-OCH(2)D are 33 669 and 62 323 cm(-1), respectively. Similarly, the E(1) and IE of trans-p-methoxyphenol-d(1)-OD are determined to be 33 563 and 62 191 cm(-1) and those of trans-p-methoxyphenol-d(1)-OCH(2)D are 33 575 and 62 216 cm(-1), respectively. Comparing these data with those of p-methoxyphenol suggests that the H/D exchange on the OH substituent gives rise to a red shift in both the E(1) and IE, whereas that on the OCH(3) group yields a blue shift. The mass-analyzed threshold ionization spectra of the selected isomers can be used as the fingerprints for molecular identification. Analysis of these cation spectra shows that the substituent-sensitive in-plane C-OH and C-OCH(3) bending (mode 9b) and breathing (mode 1) vibrations are active for all of these isomeric cations.