Gallium(iii) hydration in aqueous solution of perchlorate, nitrate and sulfate. Raman and 71-Ga NMR spectroscopic studies and ab initio molecular orbital calculations of gallium(iii) water clustersElectronic supplementary information (ESI) available: Unscaled HF/6-31+G* frequencies, intensities and force constants of the hexaaqua-Ga(iii) ion, octadeca-aqua gallium(iii) and octadeca-aqua gallium(iii) cluster. See http://www.rsc.org/suppdata/cp/b2/b202567c/