The structure and spectroscopy of lanthanide(iii) complexes with 2,2???-bipyridine-1,1???-dioxide in solution and in the solid state: effects of ionic size and solvent on photophysics, ligand structure and coordinationElectronic supplementary information (ESI) available: ORTEP drawings of Nd(bpyO2)43+, Lu(bpyO2)43+ and perchlorate anions in Nd crystal structure; absorption spectra of Nd(bpyO2)43+. See http://www.rsc.org/suppdata/nj/b2/b201846m/