Single crystal electron paramagnetic resonance spectra of triplet excitons in [(CpRu)2(η6,η6-[22](1,4)cyclophane)2+][(TCNQ)42-]

• Published in: The Journal of chemical physics 1989-02, Vol.90 (4), p.2148-2153
• Main Authors: MORTON, J. R, PRESTON, K. F, WARD, M. D, FAGAN, P. J
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron paramagnetic resonance and relaxation; Exact sciences and technology; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Physics
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.456009

Single crystals of [(Cp*Ru)2(η6,η6-[22](1,4)cyclophane)2+][(TCNQ)2−4] (Cp*=η5-C5Me5, TCNQ=tetracyanoquinodimethane) have been examined by EPR spectroscopy at temperatures down to 4 K. The anisotropic spectrum measured in the 77–150 K range is characteristic of an excitonic triplet species (I). This behavior is attributed to interactions between electrons located in one of the TCNQ acceptor stacks present in the title compound. The direction of maximum electronic interaction coincides with the stacking axis of the crystals (the crystallographic a axis). Intensity measurements establish that I is a thermally excited triplet with a J=560±30 cm−1, exhibiting zero field splittings of ‖D‖=187 MHz (66G) and ‖E‖=32 MHz (10 G). A second although weaker feature in the spectrum is tentatively assigned to a second triplet (species II) having very much smaller values of ‖D‖ and J than those of I. Species II is attributed to an impurity present in very low concentrations.