Spectroscopic studies and density functional theory investigations of a cobalt phthalocyanine derivative

• The α and β phases of a cobalt derivative have been studied by spectroscopic methods.
• Its complex structure arises from the presence of crystalline and molecular phases.
• Theoretical calculations predict novel deformations on the bond Co-anthraquinone.

Colloidal solutions at room temperature were used to obtain various polymorphic forms of a [PcCoCN]n and double potassium salt from 1,8 dihydroxyanthraquinone derivative. Nanocrystals in the form α and β were characterized using IR and UV–Vis spectroscopy techniques. Likewise in this context, an energy doublet in the absorption spectra of the monoclinic form at 1.8 and 2 eV was observed. The complex structure inherent to the spectra of the CoPc derivative is attributed to the simultaneous presence of both crystalline and molecular phases in the samples. The optical absorption of the compound was also investigated in order to evaluate changes in the electronic structure of these metal organic nanostructures. The absorption spectra of the CoPc derivative recorded in the UV–Vis region manifested two absorption bands, namely the Q- and B- bands. DFT calculations of this structure help to establish the source of the spectroscopic behavior and also lead to a particular phenomenon not known previously in this kind of complex, because the optimized structure of the cobalt complex manifests a very strange deformation of the bond between the anthraquinone derivative and the cobalt atom; the origin of this deformation is also discussed.