Nutation spectroscopy of a weakly interacting heterobimetallic spin system.

The use of VIV and CuII spins to design weakly coupled and dissymmetric spin systems has been examined. Such systems were synthesized using porphyrin-based complexes, with external coordination sites allowing for the formation of dimers via a PdII linker ion. Continuous-wave (CW) Electron Paramagnetic Resonance (EPR) spectroscopy allowed the unequivocal magnetic characterization of the mononuclear precursors V and Cu. The porphyrin dimer VPdCu presented a broad and overlapped spectrum that was more pronounced than for the previously reported VPdV, hinting at the effect of weak interspin interactions between dissimilar spins. Pulsed EPR experiments on V, VPdV and VPdCu samples diluted in a diamagnetic matrix confirmed that this complication is also present in the Field-Swept Echo-Detected (FSED) spectra of the heterometallic VPdCu system. Despite the strongly overlapped field-swept spectra, spin nutation experiments revealed two distinct oscillations in the case of VPdCu, which are assigned to transitions with different spin characters. Remarkably, coherence is retained above liquid nitrogen temperatures for all complexes, in particular up to 295 K for V and VPdV and 150 K for VPdCu.