Complexation of Flavonoids: Spectral Phenomena, Regioselectivity, Interplay with Charge and Proton Transfer

Area of Science:

• Photochemistry
• Organic Chemistry
• Spectroscopy

Background:

• Flavonoids exhibit complex spectral behaviors influenced by their electronic structure.
• Metal complexation significantly alters these electronic properties, impacting spectral characteristics.
• Understanding these changes is crucial for applications in various scientific fields.

Purpose of the Study:

• To review spectral classification of flavonoids and their electronic structure changes upon complex formation.
• To analyze the regioselectivity of complex formation and its correlation with spectral properties.
• To investigate the interplay between complexation and excited-state processes like charge and proton transfer.

Main Methods:

• Compilation and analysis of existing literature on flavonoid spectral properties.
• Review of studies on metal-flavonoid complex formation and their structures.
• Examination of spectroscopic data (absorption and emission) of flavonoid complexes.

Main Results:

• Spectral classification of flavonoids and changes upon complexation are detailed.
• Regioselectivity of complexation, chelate structures, and spectral correlations are discussed.
• The influence of complex formation on intramolecular charge transfer (ICT) and proton transfer (ESIPT) is considered.

Conclusions:

• Metal complexation profoundly impacts flavonoid spectral properties, offering avenues for tuning their optical behavior.
• The regioselectivity of complexation is a key factor governing the resulting spectral characteristics.
• This review provides a comprehensive overview of flavonoid-metal complexes and their spectroscopic signatures.