Coherent control of individual molecular spins in nano-devices is a pivotal prerequisite for fulfilling the potential promised by molecular spintronics. By applying electric field pulses during timeresolved electron spin resonance measurements, we measure the sensitivity of the spin in several antiferromagnetic molecular nanomagnets to external electric fields. We find a linear electric field dependence of the spin states in Cr7Mn, an antiferromagnetic ring with a ground-state spin of S = 1, and in a frustrated Cu3 triangle, both with coefficients of about 2 rad s −1 /Vm −1 . Conversely, the antiferromagnetic ring Cr7Ni, isomorphic with Cr7Mn but with S = 1/2, does not exhibit a detectable effect. We propose that the spin-electric field coupling may be used for selectively controlling individual molecules embedded in nanodevices.

The trinuclear copper(ii) complex [Cu3(saltag)(py)6]ClO4 (H5saltag = tris(2-hydroxybenzylidene)triaminoguanidine) was synthesized and characterized by experimental as well as theoretical methods.

A cobalt(II)-based spin triangle shows a significant spin-electric coupling. [Co 3 (pytag)(py) 6 Cl 3 ]ClO 4 •3 py crystallizes in the acentric monoclinic space group P2 1. The intratriangle antiferromagnetic interaction, of the order of ca. À15 cm À1 (H = ÀJS 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 Dg E /E = 0.11 10 À9 m V À1 , which in terms of frequency corresponds to approximately 0.3 Hz m V À1. This value is comparable to what was determined for a Cu 3 triangle despite the antiferromagnetic interaction being 20 times larger for the latter.

The pentanuclear nickel(II) complex [Ni5(saltagBr)2(tptz)4] (Ni5) with the tritopic triaminoguanidine‐derived Schiff‐base ligand H5saltagBr (1,2,3‐tris[(5‐bromosalicylidene)amino]guanidine) and tptz (2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine) as capping ligands is reported. Ni5 crystallizes in the triclinic space group P1 with the central nickel(II) ion linking two triangular arrangements of nickel(II) ions supported by two tritopic triaminoguanidine ligands. The octahedral coordination of the four peripheral nickel(II) ions is complemented by capping tridentate tptz ligands. By variation of the synthesis also the corresponding trinuclear nickel(II) complex [Ni3(saltagBr)(tptz)3]NO3 (Ni3) is accessible. Magnetic measurements for Ni3 and Ni5 reveal a singlet ground state with antiferromagnetic coupling between the nickel(II) ions, which in the case of Ni5 can only be simulated assuming a two‐J exchange coupled spin topology. For both complexes significant zero‐field splitting for the nickel(II) ions is evident from the measured magnetic data, which can be verified by theoretical studies revealing a magnetic anisotropy with strong rhombic distortion due to the presence of the tptz co‐ligands in both compounds.

The trinuclear high-spin iron­(III) complex [Fe3Cl3(saltagBr)­(py)6]­ClO4 {H5saltagBr = 1,2,3-tris­[(5-bromo-salicylidene)­amino]­guanidine} was synthesized and characterized by several experimental and theoretical methods. The iron­(III) complex exhibits molecular 3-fold symmetry imposed by the rigid ligand backbone and crystallizes in trigonal space group P3̅ with the complex cation lying on a crystallographic C 3 axis. The high-spin states (S = 5/2) of the individual iron­(III) ions were determined by Mößbauer spectroscopy and confirmed by CASSCF/CASPT2 ab initio calculations. Magnetic measurements show an antiferromagnetic exchange between the iron­(III) ions leading to a geometrically spin-frustrated ground state. This was complemented by high-field magnetization experiments up to 60 T, which confirm the isotropic nature of the magnetic exchange and negligible single-ion anisotropy for the iron­(III) ions. Muon-spin relaxation experiments were performed and further prove the isotropic nature of the coupled spin ground state and the presence of isolated paramagnetic molecular systems with negligible intermolecular interactions down to 20 mK. Broken-symmetry density functional theory calculations are consistent with the antiferromagnetic exchange between the iron­(III) ions within the presented trinuclear high-spin iron­(III) complex. Ab initio calculations further support the absence of appreciable magnetic anisotropy (D = 0.086, and E = 0.010 cm–1) and the absence of significant contributions from antisymmetric exchange, as the two Kramers doublets are virtually degenerate (ΔE = 0.005 cm–1). Therefore, this trinuclear high-spin iron­(III) complex should be an ideal candidate for further investigations of spin-electric effects arising exclusively from the spin chirality of a geometrically frustrated S = 1/2 spin ground state of the molecular system.