Several complexes of fluorine-substituted phthallic acid anhydrides with chloride anion have been optimized at the RI-MP2(full)/6-31++G** level of theory. The presence of fluorine atoms attached to the aromatic ring increases the acidity of the aromatic hydrogen atoms. The dual sigma/pi-binding affinity of title compounds have been studied by means of ab initio and molecular interaction potential with polarization (MIPp) calculations and Bader's theory of "atoms-in-molecules".