Enhanced Fluorescence by Inter/Intramolecular Hydrogen Bonding in Si-Substituted Coumarins

Abstract

Introducing heteroatoms in organic fluorophores offers a unique strategy to tune their photophysical properties without dangling structural decorations. Silicon-substituted coumarins (Si-coumarins) are the analogues of coumarin with the substitution of ester oxygen atoms by silicon atoms. In Si-coumarins, significant fluorescence enhancement in protic solvents through the formation of inter/intramolecular hydrogen bonds (H-bonds) offered great potential in various aspects with many unique photophysical properties. The energies of nπ* and ππ* states in Si-coumarins are elaborately tuned by inter/intramolecular H-bonds and solvents after incorporating silicon atoms. For example, the inter/intramolecular H-bonds elevate the energy of the nπ* state in protic solvents, leading to an enlarged energy gap between the nπ* and ππ* states. Thus, fluorescence is enhanced by reducing the nonradiative transition through the nπ* state in coumarins, resulting in many unique photophysical properties. The understanding of H-bonds in Si-coumarins offers more potential strategies for the design of novel fluorophores.

Aryl sulfonate anion stabilized aromatic triangular cation [Pd3]+: syntheses, structures and properties

“…This clear difference was also probably caused by the interactions of hydrogen bonds with hydroxyl in CH 3 OH. 37 Overall, the CIE coordinates of complex 7 changed from blue to teal with the increase of solvent polarity ( Fig. 3g ).…”