Matrix effect found in the reaction of GaCl with HCl: application of the Onsager model to describe interaction between matrices and matrix isolated species

摘要

The matrix photochemistry of the GaCl/HCl system is re-examined applying density functional theory (DFT) calculations. First, the structure of the primary hydrogen bonded complex (GaCl centre dot HCl) is presented, which allows the highly subcoordinated GaCl to partially fill up its coordination sphere releasing 2.1 kcal mol~(-1) of reaction enthalpy. This is one of the rare cases that a preformed complex in an rare gas cage can be unequivocally characterised by spectroscopic and structural methods before reacting to its final product. For all further species (GaCl, Ga_2Cl_2, HGaCl_2) accurate geometries, energies and IR spectra are derived as well. Second, the remaining differences between experiment and theory are reconciled by considering the solvation effects of the matrix material used. The Onsager theory applied to this particular photoreaction can explain the significant change of the IR frequency of GaCl observed in the gas phase (vGaCl = 352 cm~(-1)) and in 'weakly' solvating rare gas matrices (vGaCl = 329 cm~(-1)). Thus, a valuable method for improving the interpretation of matrix isolation IR data is demonstrated.