Spin-Electric Coupling in a Cobalt(II)-Based Spin Triangle Revealed by Electric-Field-Modulated Electron Spin Resonance Spectroscopy

A cobalt(II)-based spin triangle shows a significant spin-electric coupling. [Co-3(pytag)(py)(6)Cl-3]ClO4.3 py crystallizes in the acentric monoclinic space group P2(1). The intra-triangle antiferromagnetic interaction, of the order of ca. -15 cm(-1) (H=-JS(a)S(b)), leads to spin frustration. The two expected energy-degenerate ground doublets are, however, separated by a few wavenumbers, as a consequence of magnetic anisotropy and deviations from threefold symmetry. The Co-3 planes of symmetry-related molecules are almost parallel, allowing for the determination of the spin-electric properties of single crystals by EFM-ESR spectroscopy. The spin-electric effect detected when the electric field is applied in the Co-3 plane was revealed by a shift in the resonance field. It was quantified as Delta g(E)/E=0.11x10(-9) m V-1, which in terms of frequency corresponds to approximately 0.3 Hz m V-1. This value is comparable to what was determined for a Cu-3 triangle despite the antiferromagnetic interaction being 20 times larger for the latter.