Atomic charges and structures of some hydrogen bonded substituted anilinium chloride systems: Correlation with XPS

Using the MOPAC/AM1 method and employing an aggregate involving a cation with three hydrogen bonded chloride counterions, atomic charge calculations have been made on the basis of known crystal structures for the anilinium derivatives RR'C6H4NH3+Cl-, in which R = 4-CH3, R' = H, and R = 2-CH3, R' = 6-CH3, together with the newly determined structures which have R = 2-OCH3, R' = H (I) and R = 2-CH3, R' = H (II). For I, molecular formula C7H10NClO:space group P21/c, Z = 4 with a = 0.5374 (5), b = 1.3869 (7), c = 1.0940 (8)nm, beta = 97.61(7)degrees, R, R(w) = 0.050, 0.047. For II molecular formula C7H10ClN : space group Pca2(1), Z = 4 with a = 1.5767 (6), b = 0.5408 (3), c = 0.8705 (4) nm, R, R(w) = 0.041, 0.035.The estimated charges on the N atoms are shown to correlate with the N(1s) binding energies, determined via XPS measurements. It is also demonstrated that these charges are largely independent of substituent ring position.