Dynamic Decoupling Doubles Coherence Times in a Nuclear Spin “Lite” Vanadium(IV) Tris(dithiolate)

The spin dynamics of a tris(dithiolate)vanadium complex dianion and perdeutero-tetraphenylarsonium cation, (AsPh4-d20)2[V(mnt)3], composed of spin-free and weakly magnetic nuclei are investigated in an analogously composed solvent system, CDCl3/Cl3CCN (4:1). This gives the longest reported coherence times for a transition-metal-based spin in deuterated solvents with a T1 of 164(4) ms, and a TM of 60(2) μs. Dynamic decoupling more than doubled TM, resulting in TM = 136(13) μs. The enhancing capabilities of Carr-Purcell and Uhrig-type pulse sequences are compared, revealing significantly different trends. The very limited effectiveness of such dynamic decoupling experiments highlights the need to fully purge the electron-spin environment of magnetic nuclei, and underlines the importance of considering both the fast and slow components of TM. Indeed, the main component (ca. 50-85%) of the decoherence is found to occur with a fast process which drastically shortens the feasibility of extending the number of pulses. This observation further highlights the need to explore dynamic decoupling in tandem with electron-spin environment engineering to eliminate fast decoherence processes.