Synthesis and quantum chemical study of PDI derivatives with phenylalkynyl groups at the bay position

Six new perylenetetracarboxylic diimide (PDI) compounds were prepared by introducing alkynyl or alkynylphenyl groups with different length to the bay position of PDI ring. The UV–vis absorption and emission spectra of these new compounds were recorded. The red-shift on the maximum absorption and emission peaks revealed the efficient participation of the side conjugation chain to the whole conjugation system. The molecular structure, the frontier molecular orbital and the energy gaps between the highest occupied orbital (HOMO) and the lowest un-occupied orbital (LUMO) were calculated with DFT method. The results show good consistent with the experimental results. The absorption and emission spectra of these six compounds were also simulated with TD-B3lyp/6-31g(d) and TD-PBE1PBE/6-31g(d) methods. The simulated results for the compounds with short side conjugation chain show better response to the experimental results. However, the quantum calculation on the compounds with long conjugated side chain do not give satisfied results because of the significant electron transfer characteristics in the excited states.