Ligand Effects on the Spin Relaxation Dynamics and Coherent Manipulation of Organometallic La(II) Potential Qu d its.

We present pulsed electron paramagnetic resonance (EPR) studies on three La(II) complexes, [K(2.2.2-cryptand)][La(Cp') 3 ] ( 1 ), [K(2.2.2-cryptand)][La(Cp″) 3 ] ( 2 ), and [K(2.2.2-cryptand)][La(Cp tt ) 3 ] ( 3 ), which feature cyclopentadienyl derivatives as ligands [Cp' = C 5 H 4 SiMe 3 ; Cp″ = C 5 H 3 (SiMe 3 ) 2 ; Cp tt = C 5 H 3 (CMe 3 ) 2 ] and display a C 3 symmetry. Long spin-lattice relaxation ( T 1 ) and phase memory ( T m ) times are observed for all three compounds, but with significant variation in T 1 among 1 - 3 , with 3 being the slowest relaxing due to higher s-character of the SOMO. The dephasing times can be extended by more than an order of magnitude via dynamical decoupling experiments using a Carr-Purcell-Meiboom-Gill (CPMG) sequence, reaching 161 μs (5 K) for 3 . Coherent spin manipulation is performed by the observation of Rabi quantum oscillations up to 80 K in this nuclear spin-rich environment ( 1 H, 13 C, and 29 Si). The high nuclear spin of 139 La ( I = 7/2), and the ability to coherently manipulate all eight hyperfine transitions, makes these molecules promising candidates for application as qu d its (multilevel quantum systems featuring d quantum states; d >2) for performing quantum operations within a single molecule. Application of HYSCORE techniques allows us to quantify the electron spin density at ligand nuclei and interrogate the role of functional groups to the electron spin relaxation properties.