Absorption spectra of PTCDI: A combined UV–Vis and TD-DFT study

Absorption spectra of PTCDI (3,4,9,10-perylene-tetracarboxylic-diimide) have been investigated in chloroform, N,N′-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). While no signature of assembled PTCDI molecules is observed in chloroform solution, distinct bands assigned to their aggregation have been identified in DMF and DMSO solutions. PTCDI monomers show very similar absorption patterns in chloroform and DMSO solutions.Experimental data, including the vibronic structure of the absorption spectra were explained based on the Franck–Condon approximation and quantum chemical results obtained at PBE0-DCP/6-31+G(d,p) level of theory. Geometry optimization of the first excited state leads to a nice agreement between the calculated adiabatic transition energies and experimental data.

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► Absorption spectra of PTCDI in three solvents were investigated.
► No aggregation of PTCDI in chloroform is observed.
► Association of PTCDI molecules in DMF and DMSO gives distinct UV–Vis bands.
► FC approximation leads to accurate calculated excitation energies.
► Vibronic structure of absorption spectrum was explained using the FC approximation.