Nuclear Spin Isomers: Engineering a Et₄N[DyPc₂] Spin Qudit

Two dysprosium isotopic isomers were synthesized: Et 4 N[ 163 DyPc 2 ] ( 1 ) with I =5/2 and Et 4 N[ 164 DyPc 2 ] ( 2 ) with I =0 (where Pc=phthalocyaninato). Both isotopologues are single‐molecule magnets (SMMs); however, their relaxation times as well as their magnetic hystereses differ considerably. Quantum tunneling of the magnetization (QTM) at the energy level crossings is found for both systems via ac‐susceptibility and μ‐SQUID measurements. μ‐SQUID studies of 1 ( I =5/2) reveal several nuclear‐spin‐driven QTM events; hence determination of the hyperfine coupling and the nuclear quadrupole splitting is possible. Compound 2 ( I =0) shows only strongly reduced QTM at zero magnetic field. 1 ( I =5/2) could be used as a multilevel nuclear spin qubit, namely qudit ( d =6), for quantum information processing (QIP) schemes and provides an example of novel coordination‐chemistry‐discriminating nuclear spin isotopes. Our results show that the nuclear spin of the lanthanide must be included in the design principles of molecular qubits and SMMs.