Solvent dependent photophysical properties of dimethoxy curcumin

Area of Science:

• Photochemistry
• Molecular Spectroscopy
• Organic Chemistry

Background:

• Curcumin exhibits interesting photophysical properties.
• Understanding structure-property relationships is crucial for developing new functional molecules.
• Methylated derivatives like dimethoxy curcumin (DMC) offer a platform to study these relationships.

Purpose of the Study:

• To investigate the effect of ring substitution on the photophysical properties of curcumin.
• To compare the spectral behavior of dimethoxy curcumin (DMC) with curcumin.
• To elucidate the influence of solvent polarity on DMC's absorption and fluorescence characteristics.

Main Methods:

• Steady-state absorption and fluorescence spectroscopy were employed.
• Measurements were conducted in organic solvents of varying polarity.
• Analysis included solvent polarity function (Δf) and Stokes' shift calculations.

Main Results:

• Both absorption and fluorescence spectra of DMC demonstrated strong solvent polarity dependence.
• A red shift in DMC's spectral maxima was observed with increasing solvent polarity, more pronounced in fluorescence.
• The difference in dipole moments between the excited and ground states was estimated at 4.9 D.

Conclusions:

• The photophysical properties of dimethoxy curcumin (DMC) are significantly influenced by solvent polarity.
• Increased solvent polarity leads to a red shift in fluorescence and a linear increase in fluorescence quantum yield (φ(f)).
• This enhancement in quantum yield is attributed to a reduced non-radiative decay rate via intersystem crossing (ISC).