Stability improvement of UV-filter between methoxy cinnamic acid derivatives and cyclodextrins inclusion complexes based on DFT and TD-DFT investigations

Structures and UV-vis absorption spectra of the host-guest interaction of the methoxy cinnamic acid (MCA) derivatives and cyclodextrins (CDs) were performed by using the density functional theory (DFT) and timedependent DFT (TD-DFT) calculations. All geometries of MCA derivatives (4-MCA, 245-MCA, 246-MCA), three types of CD (alpha CD, beta CD, gamma CD), and five host-guest inclusion complexes between MCA and CD consisting of 4MCA/alpha CD (1), 4-MCA/beta CD (2), 245-MCA/beta CD (3), 246-MCA/beta CD (4), and 246-MCA/gamma CD (5) were fully optimized by using the M06-2X/6-31G (d,p) levels of theory. Two orientations (A and B) of the MCA guest molecule were considered. Upon examining the optimized geometry, five complexes of the methoxy cinnamic acid molecules are located inside the cavity of CD. Orientation B was more stable than orientation A because of the stronger intermolecular hydrogen bonds between the hydroxyl group of CD and the carboxylic group of MCA. The results indicated that the intermolecular hydrogen bond is mainly the driving force of formation between methoxy cinnamic acid and cyclodextrins. To reveal the host-guest interaction that is relevant to UV-filter compounds, the UV-vis absorption spectra were performed using TD-DFT calculations. The obtained results confirmed that orientation B is the most stable orientation and can absorb in both UVB and UVA regions which is similar to the parent MCA. Therefore, this knowledge will bring to understand the host-guest interaction between methoxy cinnamic acid and cyclodextrin complexes. The theoretical results are expected to provide valuable information for improving the stability of further UV-filter compounds.

Automated summary

This study investigated the host-guest interaction between methoxy cinnamic acid derivatives and cyclodextrins using density functional theory (DFT) and timedependent DFT (TD-DFT) calculations. The results revealed that intermolecular hydrogen bonds are the main driving force of this interaction. In addition, UV-vis absorption spectra analysis showed that one particular orientation is the most stable and similar to the parent MCA in terms of absorption in both UVB and UVA regions. These findings provide valuable insights into the host-guest interaction and stability improvement of UV-filter compounds.