Thermodynamics of sublimation and the effect of aggregation on the electronic absorption spectra of etioporphyrins Cu-etiop-III and VO-etiop-III

In this paper, a comparative experimental and theoretical study of two etioporphyrin complexes (Cu-EtioP-III and VO-EtioP-III) with transition metals is carried out. The sublimation enthalpies of Cu-EtioP-III and VO-EtioP-III were determined to be 145(3) kJ/mol and 195(5) kJ/mol, respectively using the Knudsen effusion method with mass spectrometric control of the vapor composition. The electronic absorption spectra of vacuum-sublimated Cu-EtioP-III layers were simulated using TD-DFT calculations for mono-, di-, tetra- and hexameric forms with the geometric structure corresponding to the crystal unit cell. Comparison of the results with similar data for VO-EtioP-III allows us to draw conclusions about the ability of the simplest natural porphyrinoids to form intermolecular bonds during aggregation (in thin layers, crystals).