Steric Control of Photocatalytic Electron Transfer: A Predictive Framework Using Sterimol Parameters

Area of Science:

• Photochemistry
• Organic Chemistry
• Materials Science

Background:

• Steric effects significantly impact excited-state electron transfer processes in photocatalysis.
• Accurate prediction of steric influence on electron transfer efficiency remains a challenge in catalyst design.

Purpose of the Study:

• To quantify the steric bulk of axial substituents on silicon phthalocyanine photocatalysts using Sterimol parameters.
• To evaluate the influence of these steric effects on electron-transfer efficiency via fluorescence-quenching experiments.
• To develop a predictive model for electron-transfer efficiency based on steric descriptors.

Main Methods:

• Synthesis and characterization of 11 silicon phthalocyanine derivatives with varying axial substituents.
• Fluorescence-quenching experiments using N,N-diisopropylethylamine as a quencher.
• Multiparameter linear regression analysis correlating Sterimol parameters with Stern-Volmer quenching constants (K_SV).

Main Results:

• A significant correlation was found between Sterimol parameters and K_SV values.
• The Sterimol descriptors wB₁ (minimum width), wB₅, and wL showed distinct contributions to the correlation.
• Minimum substituent width (wB₁) emerged as the dominant steric parameter influencing electron-transfer efficiency.
• Leave-two-out cross-validation indicated good predictive performance for related catalysts.

Conclusions:

• Sterimol parameters provide a quantitative measure of steric effects in silicon phthalocyanine photocatalyst quenching.
• A predictive model based on Sterimol parameters can estimate electron-transfer efficiency for new photocatalysts.
• This approach offers a framework for designing photocatalysts with tailored steric properties for enhanced performance.