Chemically induced dynamic electron spin polarization-detected energy transfer. Substrate size effects and solvent dependence

Time-resolved electron paramagnetic resonance spectroscopy is used to probe energy transfer from aromatic photoexcited triplet states to azo compounds in liquid solution. The observation of chemically induced dynamic electron spin polarization in the spectra gives precise information regarding the spin physics and mechanism of the energy transfer process. The substrate size is varied by altering the chain length of alkyl chains covalently attached to the azo compounds via ester or amide linkages. The solvent dependence of the energy transfer process is also investigated. The results are discussed in terms of Dexter and Forster mechanisms for energy transfer, the properties of the excited states, and the diffusive properties of the molecules in the solvents of interest. Decomposition rate studies and fluorescence measurements are also reported.