Investigations on the electronic effects of the peripheral 4?-group on 5-(4?-substituted)phenylazo-8-hydroxyquinoline ligands: zinc and aluminium complexesElectronic supplementary information (ESI) available: synthesis details of ligands I?VI, complexes 1a?6a and 2b?6b, absorption maxima from electronic spectra of compounds I?VI, 1a?6a and 1b?6b, emission spectra of complexes 1a and 1b, Cartesian coordinates of neutral and charged ligands I, A, V and VI, the Kohn?Sham orbital energies and the HOMO?LUMO gaps for compounds I, A, V and VI, and atomic spin density for two nitrogen atoms of the diazo group and the computed geometries of the neutral and charged compounds I, A, V and VI. See http://www.rsc.org/suppdata/dt/b4/b404814h/