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

Abstract

Two dysprosium isotopic isomers were synthesized: Et₄ N[¹⁶³ DyPc₂ ] (1) with I=5/2 and Et₄ N[¹⁶⁴ DyPc₂ ] (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.