Electronic photodissociation spectra and decay pathways of gas-phase IrBr62-

We report photodissociation action spectra for the dianion IrBr(6)2- in the range of 1.08-5.6 eV. The photoproducts observed are IrBr6-, IrBr5-, IrBr4- and Br-. Comparison of the action spectra to the aqueous absorption spectrum of K2IrBr6 leads to the determination of solvatochromic shifts of between 0.02 and 0.16 eV in the visible region and approximately 0.3 eV in the ultraviolet. The fragmentation branching ratios vary greatly as a function of photon energy. This behavior can be attributed to differences in the fragmentation mechanisms as well as differences in the excited states that are accessed at different energies. Absorption in the visible region favors fragmentation into IrBr5- and Br-, whereas a number of fragmentation channels and mechanisms are active in the ultraviolet region. These mechanisms include fragmentation as well as electron detachment and dissociative electron detachment.