Pillaring of HTO with PA or HDA therefore results in the reduction of the average Ti oxidation state, with more reduction in the case of HTO-HDA. This could be explained by the overall higher number of amine groups in HTO-HDA compared to HTO-PA (ca. 2 versus 1.5 amine groups per H2Ti4O9, respectively). The N 1s core-level spectra (Fig. ) reveal the coexistence of NH3 + and NH2 species in the pillared materials, suggesting that the organic pillar exists in the structure in both its free and ionic (alkylammonium ion) forms. The ratio of NH3 + to NH2 was estimated to be ca. 4 to 1 in HTO-PA, and 2.5 to 1 in HTO-HDA, respectively. The higher NH3 + /NH2 peak intensity ratio in HTO-PA suggests a higher tendency for the organic pillars to exist in their ionic form compared to HTO-HDA, where the alkyldiamine molecule might contain an ionized NH 3+ on one end and a neutral NH2 on the other. Moreover, it is unlikely that covalent Ti-N bonds are forming due to the absence of a Ti-N peak at 397.2 eV. These findings agree with previous works that detected mixed NH2 and NH3 + species in alkylaminepillared titanates and alkyldiamine-pillared vanadia.