Mass-Analyzed Threshold Ionization Spectroscopy of o-, m-, and p-Methylaniline Cations:  Vicinal Substitution Effects on Electronic Transition, Ionization, and Molecular Vibration

Abstract

We have applied two-color resonant two-photon mass analyzed threshold ionization (MATI) spectroscopy to investigate the ionic properties of the structural isomers of methylaniline. The adiabatic ionization energies of o-, m-, and p-methylanilines have been determined to be 61 002 ( 5, 61 059 ( 5, and 60 160 ( 5 cm -1 , respectively. These vibrationally resolved spectra provide information about the active normal vibrations of the corresponding cations. The observed spectral features have been successfully assigned on the basis of comparison with the results from ab initio and density functional calculations and experimental data available in the literature. The results suggest that both the nature of the substitutents and the relative location in the ring can influence the electronic transition, ionization, and molecular vibration for these structural isomers.

Mass analyzed threshold ionization spectroscopy of o-fluorophenol and o-methoxyphenol cations and influence of the nature and relative location of substituents

“…As the ionization process includes the S 1 S 0 and D 0 S 1 transitions, the resulting IEs of these fluoro substituted phenols and anilines follow the order: para < ortho < meta. It has been reported [37,38] that the IEs of o-, m-, p-methylanilines are 61,002, 61,059, and 60,160 cm À1 , respectively. Thus, it follows the same order as those of fluorophenols and fluoroanilines.…”

Mass-analyzed threshold ionization spectroscopy of the rotamers of p-n-propylphenol cations and configuration effect

“…The EEs of p-methylaniline, p-ethylaniline, trans p-n-propylaniline, and gauche p-n-propylaniline and the corresponding benzene derivatives are also listed in Table IV. 6,15,[33][34][35][36][37][38] These results show that the effects of the alkyl chain on the EEs of p-alkylanilines and alkylbenzenes are similar to those of p-alkylphenols. It is known that the S 1 ←S 0 transitions of benzene, aniline, and phenol mainly involves the excitation of the electron clouds of the aromatic ring.…”

“…It is found that most of the MATI spectra demonstrate a propensity of maintaining the vibration of the intermediate level. 31,34,39,40 Figures 7͑a͒-7͑c͒ show the MATI spectra of trans p-n-propylphenol recorded by ionizing via the vibrational 9b 1 , 6a 1 , and 1 1 levels in the S 1 state. The general features in these MATI spectra of trans p-n-propylphenol are similar to those of p-methylphenol.…”

Resonant two-photon ionization and mass-analyzed threshold ionization spectroscopy of the selected rotamers of m-methoxyaniline and o-methoxyaniline

“…Oppositely, it yields a blue shift. Table 5 lists the measured E 1 's and IEs of o-methoxyaniline, m-methoxyaniline, and p-methoxyaniline, and several substituted anilines [16,19,20,[25][26][27][28][29]. These species have a general formula of XC 6 H 4 NH 2 , where X is H, OH, OCH 3 , CH 3 , or F at the ortho, meta, or para position with respect to the NH 2 group.…”