INFRARED PHOTODISSOCIATION SPECTROSCOPY OF MASS-SELECTED METAL ION-BENZENE COMPLEXES

Author Institution: DEPARTMENT OF CHEMISTRY, UNIVERSITY OF GEORGIA; DEPARTMENT OF CHEMISTRY, F. O. M. LABORATORY FOR PLASMAPHYSICS RIJNHUISENMetal ion-benzene complexes of the form $M^{+}(benzene)_{1,2} (M=V, Ti, Al)$ are produced by laser vaporization in a pulsed nozzle source, mass-selected in an ion-trap mass spectrometer and excited in the infrared with a free electron laser. Multiphoton dissociation occurs by the elimination of benzene molecules. The photofragment yield versus wavelength produces IR resonance-enhanced multiphoton photodissociation (IR-REMPD) spectroscopy for these complexes. Vibrational bands in the $600-1800cm^{-1}$ region are characteristic of the benzene molecular moiety perturbed by the metal bonding. Experimental data are compared to the IR spectra derived from density functional calculations. Vibrational patterns in $V^{+}(C_{6}H_{6})$ indicate that the metal is bound in an $\eta^{6} \pi$-bonding configuration, while $V^{+}(C_{6}H_{6})_{2}$ is a sandwich. Trapped-ion IR-REMPD is a general method to access the vibrational spectra of novel organometallic complexes