Pressure dependence of zero-field splittings in organic triplets. I. Aromatics

Abstract

Optically detected magnetic resonance experiments have been conducted at pressure up to 45 kbar for p-dichlorobenzene (DCB), s-tetrachlorobenzene (TCB) and quinoxaline (Q). The pressure dependence of their zero-field splitting parameters and, for DCB, the quadrupolar splitting are reported. For all three systems the D value decreases moderately with increasing pressure. The slope for TCB is approximately twice that for DCB. These results are interpreted in terms of pressure dependence of the mesomeric effect and the inductive effect of the substituents on the aromatic triplet state. For Q, the influence of pressure on spin-orbit interaction is also suggested.