Determination of the T₁ state energy levels of metalloporphyrins using temperature-dependent time resolved spectroscopy

Area of Science:

• Photochemistry
• Spectroscopy
• Materials Science

Background:

• Metalloporphyrins are crucial photosensitizers in various applications.
• Understanding their triplet excited state energy (ET1) is vital for optimizing functionality.
• Existing methods for ET1 determination can be complex or limited.

Purpose of the Study:

• To propose and validate a novel strategy for determining the ET1 values in metalloporphyrin systems.
• To investigate the temperature dependence of oxygen quenching rate constants.
• To provide insights into energy-loss mechanisms in metalloporphyrin photoconversion.

Main Methods:

• Utilized time-resolved spectroscopy to analyze oxygen quenching rate constants.
• Employed a theoretical model based on thermal equilibrium between triplet and oxygen excited states.
• Studied Platinum(II) octaethylporphyrin (PtOEP) and Palladium(II) octaethylporphyrin (PdOEP) as model systems.
• Validated the approach using excitation spectra of metalloporphyrins.

Main Results:

• Demonstrated a nonlinear temperature dependence of the oxygen quenching rate.
• Successfully determined ET1 values for PtOEP and PdOEP using the developed model.
• Confirmed the validity of the proposed strategy through experimental data.

Conclusions:

• The proposed method offers an effective pathway for determining ET1 in metalloporphyrins.
• This approach provides new insights into energy-loss mechanisms relevant to photoconversion.
• The findings facilitate better understanding and optimization of metalloporphyrin photosensitizers.