Q-state absorption spectra of the phthalocyanines (Pc) H2Pc, MgPc, ZnPc and AlPcCl have been simulated by calculating Franck-Condon (FC) factors with time-dependent density functional theory (TD-DFT) using M11, PBE0 and B3LYP functionals and the 6- 31G(d) basis set. Comparisons of the electronic band origins (�0,0) recorded under low temperature, jet-cooled conditions with the predicted (T = 0 K) values, indicate that the B3LYP functional provides the best results for the three metal phthalocyanines (MPc). For H2Pc the M11 functional performed marginally better than B3LYP. The FC spectrum simulated for AlPcCl at 60 K accounts very well for strong hot bands present in the recorded excitation spectrum. The vibrational motion responsible was identified as a low frequency out-of-plane bending mode at 17.77 cm-1 activated when the GS C4v symmetry is reduced to C2v in the ES. The long-range FC vibronic structure was compared with He droplet data which provides the simplest spectra enabling the direct vibronic mode assignments. The assigned band structures present in excitation are also present in emission - a finding consistent with the similarities in the geometries calculated for the phthalocyanines in the ground and excited Q-state. TDDFT was used to calculate vertical excitation energies of squarate dianion (C4O4 2- ) revealing a previously undocumented � → � ∗ transition occurring at 25066.43 cm-1 in vacuum. This lowest energy allowed transition was investigated by optimising the ground state geometry and calculating its absorption in a variety of solvents with a range of dielectric constants using the Polarisable Continuum Model (PCM). It was found that the � → � ∗ transition is highly solvent dependent due to a large charge separation in the associated molecular orbitals. The transition blueshifts strongly with the increase in dielectric constant so that in water it is located in the UV region (44477 cm-1 )