Magnetic field effect on the photochemistry of chromium complex

Abstract

The magnetic field effect (MFE) on the emission spectrum, phosphorescence lifetime and quenching by phenols were investigated for the tris(1,10 phenantroline) chromium (III) complex ([Cr(phen)3]3+). The reactions in the present study have been investigated as a function of the field intensity, between 0–8 T at ambient temperature. With the aid of a homemade magnetic field generator, changes in the emission spectrum and lifetime of the (2T/2E) states of [Cr(phen)3]3+ in presence of an external magnetic field were observed. The emission spectrum showed changes in their two phosphorescent states, 2E and 2T1 doublets; a split and a shift, with enhanced emission, of the band located at 700 nm corresponding to the 2T1 → 4A1g transition and an intensity decrease in the band located at 730 nm, corresponding to the 2E → 4A1g transition. The phosphorescent lifetime for both emission states, which is ∼70 μs in aerated aqueous solutions at ambient temperature, showed a decrease when increasing with the external magnetic field applied. The MFE on the quenching rate constants (kq B) for phenols were evaluated and discussed in terms of transition state theory and outer coordination sphere complexes reactions.