TDDFT study of UV–vis spectra of permethrin, cypermethrin and their beta-cyclodextrin inclusion complexes: A comparison of dispersion correction DFT (DFT-D3) and DFT

• The UV–vis spectra of β-CD inclusion complexes were studied by TDDFT.
• A comparison of DFT-D3 and DFT has been carried out.
• The UV–vis spectra of inclusion complexes arise from intermolecular charge transfer.

A comparative study of DFT and DFT-D3 has been carried out on the UV–vis absorption of permethrin, cypermethrin and their β-cyclodextrin inclusion complexes. The TDDFT method with PCM (or COSMO) model was adopted and B3LYP, BLYP and BLYP-D3 functionals were selected. Comparing the simulated spectra with experimental one, we can notice that pure BLYP functional can better reproduce the UV–vis spectra than hybrid B3LYP, but empirical dispersion corrections BLYP-D3 has better performance than BLYP. BLYP-D3 calculations reveal that the main absorption bands of permethrin and cypermethrin arise from the π → π* transition, after encapsulated by β-CD to form inclusion complexes, the host–guest intermolecular charge transfer (ICT) makes the main absorption bands to be changed significantly in wavelength and intensity.

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