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

Abstract

Two dysprosium isotopic isomers were synthesized: Et N[ DyPc ] (1) with I=5/2 and Et N[ DyPc ] (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 reveal several nuclear-spin-driven QTM events; hence determination of the hyperfine coupling and the nuclear quadrupole splitting is possible. Compound 2 shows only strongly reduced QTM at zero magnetic field. 1 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.

Manipulation of the Coordination Geometry along the C4 Rotation Axis in a Dinuclear Tb3+ Triple‐Decker Complex via a Supramolecular Approach

“…However, due to the instability of the isotope of 154 Tb ion ( I =0), detailed investigation was not possible. Therefore, the influence of QTM on the isotope has been examined for the Dy 3+ ion . Thus, by using a supramolecular approach and investigating the details of the magnetic relaxation mechanism, it may be possible to investigate the relationship between the LF and the I ‐ J interactions of Ln 3+ ion.…”

“…This is due to the large magnetic anisotropies and the large | m J | quantum ground states of 4f ions, such as terbium(III) (Tb 3+ ), dysprosium(III) (Dy 3+ ) and erbium(III) (Er 3+ ) ions . For SMMs to be useful in memory devices, quantum computing, and quantum information processing, their properties must be controllable . In particular, the magnetic relaxation times ( τ ), which include contributions from quantum tunneling of the magnetization (QTM), must be drastically slowed.…”

Synthetic Hilbert Space Engineering of Molecular Qudits: Isotopologue Chemistry

“…[41] The utilization of 164 Dy(III) (I = 0) led to the observation of enlarged hysteresis loops at zero field, in comparison to SMMs obtained from the naturally occurring isotopic mixture. [43] Altogether, the presence of multiple nuclear-spin-driven QTM events as well as the determination of the hyperfine coupling and the nuclear quadrupole splitting prove that [ 163 DyPc 2 ] − could be potentially used as qudit with an increased Hilbert space of d = 6 in QIP schemes. [42] In the search for isotope-based quantum effects in SMMs we have prepared two isotopologue molecules: Et 4 N[ 164 DyPc 2 ] with I = 0 and Et 4 N[ 163 DyPc 2 ] with I = 5/2 (Et 4 N + being the tetraethylamino cation).…”

“…Instead, the much more favorable Kramers character of Dy(III) often produces a well isolated ground doublet state, making it the leading lanthanide for the synthesis of SMMs. [43] Concerning the second strong requirement, the presence of the quadrupolar term of the hyperfine coupling to guarantee an unequal energy spacing of the nuclear spin states to be addressed, the µ-SQUID loops for [ 163 DyPc 2 ] − revealed a staircase-like structure between ≈±20 mT (see Figure 6c right), which is clear evidence of hyperfine-induced QTM events. Recently, in the quest for improved SMM properties, some research groups exploited the synthesis of isotopically enriched Dy-SMMs to improve the magnetic hysteresis width by excluding nuclear spins.…”

“…However, before the advantageous magnetic properties of Dy(III) ions can be used, one challenge has to mas-tered: whereas 159 Tb(III) contains a single nuclear spin isotope, I = 3/2, with 100% natural abundance, the natural composition of Dy(III) comprises seven isotopes, possessing two different nuclear spin states, I = 0 and 5/2. [43] This crossing is further split, due to the entanglement between the |13/2〉 electronic and the being α, β, and γ the Stevens constants. [41] The utilization of 164 Dy(III) (I = 0) led to the observation of enlarged hysteresis loops at zero field, in comparison to SMMs obtained from the naturally occurring isotopic mixture.…”