Exploring Novel Interfacial Charge Transfer Complexes Between TiO2 and Flavonoids: Theoretical Study.

The formation of interfacial charge transfer (ICT) complexes with suitable ligands is an effective method to improve the spectral properties of materials based on titanium dioxide (TiO₂). In the presented work, six structurally different flavonoids are studied as potential ligands for synthesizing novel TiO₂-based ICT complexes using density functional theory (DFT). The formation of stable bidentate Ti-O coordination between the TiO₂ surface and studied flavonoids is confirmed by Bader's quantum theory of atoms in molecules (QTAIM) analysis. The calculated band gaps of the studied ICT complexes are within the range of 1.95-2.15 eV, which is significantly lower than the one of pristine TiO₂ (3.20 eV) and it corresponds to the absorption in the visible spectral region. The lowest band gaps were found for the ICT complexes with flavonoids containing the OH group at position 3 of the C ring (myricetin, quercetin). The thermochemistry calculations revealed that the formed ICT complexes possess increased radical scavenging potential when compared to their parent flavonoids, which are well-known as naturally occurring antioxidants.