Triplet Exciton EPR and Crystal Structure of [TMPD + ] 2 [Ni(mnt) 2 ] −2
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We report in this paper the results of EPR and x ray diffraction studies on the ionic-radical salt [TMPD+]2[Ni(mnt)2]-2composed of an organic free radical cation and a diamagnetic transition metal complex ion. This crystal exhibits the triplet exciton EPR spectrum characteristic of an alternating chain of spins. Exciton creation energy is ΔE = 0.240±0.005 eV; triplet spin Hamiltonian parameters are | D |= 215±1 G and |E| =28±1 G; gzz= 2.0029, gyy= 2.0033, gxx= 2.0035, all ±0.0005. The complex crystallizes in Ci1-P1̄ of the triclinic system, with cell dimensions of a = 9.145 (9) Å, b=11.502 (9) Å, c = 7.762 (8) Å, α= 98.24 (5)°, β= 105.69 (2)° and γ = 92.64 (4)°. The organic free radicals form very strongly alternating linear chains and we examine the extent to which EPR results for a triplet exciton system may, through knowledge of the crystal structure of the system, be related in a detailed fashion to the zeroth order picture of the spin excitation of an isolated free radical pair.
author list (cited authors)
Hove, M. J., Hoffman, B. M., & Ibers, J. A.