Lithium naphthalocyanine as a new molecular radical probe for electron paramagnetic resonance oximetry

Abstract A new lithium naphthalocyanine dye aggregate [Li2Nc][LiNc] is reported as a potential electron paramagnetic resonance (EPR) oximetry probe for accurate measurement of oxygen concentration in biological systems. The Li2Nc is diamagnetic; however, the LiNc molecule has an unpaired electron and hence is paramagnetic. The aggregate shows a strong and single line EPR signal that is non-saturating at normal EPR power levels. An oxygen-dependent peak-to-peak EPR spectral width ranging from 0.51 G (at pO2: 0 mmHg) to 26.2 G (at pO2: 760 mmHg) has been observed. The application of this probe has been demonstrated in the measurement of arterial and venous oxygen tensions in a rat.