Spin Correlation in Ion Radical Salts; The System (Cs+)2(TCNQ)3=

Abstract

The physical properties of the (Cs+)2(TCNQ)3 = ion radical salt as measured by electron paramagnetic resonance are discussed in terms of the preliminary crystal‐structure data. The salt is characterized by a thermally accessible triplet state lying 0.16 ev above a singlet ground state; the triplet state is described by a rhombic spin Hamiltonian H =βH·g·S+DS z 2 +E(S x 2 −S y 2 ), with D/hc=±0.009367 cm—1, E/hc=±0.001513 cm—1, and gx, gy, gz equal to, respectively, 2.0025, 2.0015, and 2.0003. Some conclusions are drawn regarding the general class of ion radical salts exhibiting triplet state character. The concept of spin delocalization over several TCNQ molecules is strengthened, and, from consideration of the temperature‐dependent exchange narrowing effects present in these systems, arguments are presented to the effect that the triplet excitation may be free to propagate as a triplet exciton.