Eufemio Moreno-Pineda

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

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.

Molecular Nanomagnets Based on f-Elements

Abstract Molecular nanomagnets include metal complexes that show single-ion magnet, single-molecule magnet, or single-chain magnet behavior. In these compounds, slow magnetic relaxation is often observed at much higher temperatures than seen in 3D analogues due to the strong spin-orbit coupling of f-elements and the effects of the crystal field symmetry. This chapter will provide a concise introduction to the field of f-based molecular nanomagnets, and discuss key aspects regarding the relaxation property and the relaxation mechanisms operating in these systems. We overview the most significant properties and magnetic phenomena associated with slow-relaxing molecular nanomagnets, and discuss selected examples of single-ion, single-molecule, and single-chain magnets.

Synthesis and Characterization of a Heterometallic Extended Architecture Based on a Manganese(II)-Substituted Sandwich-Type Polyoxotungstate

The reaction of [α-P2W15O56]12− with MnII and DyIII in an aqueous basic solution led to the isolation of an all inorganic heterometallic aggregate Na10(OH2)42[{Dy(H2O)6}2Mn4P4W30O112(H2O)2]·17H2O (Dy2Mn4-P2W15). Single-crystal X-ray diffraction revealed that Dy2Mn4-P2W15 crystallizes in the triclinic system with space group P1¯, and consists of a tetranuclear manganese(II)-substituted sandwich-type phosphotungstate [Mn4(H2O)2(P2W15O56)2]16− (Mn4-P2W15), Na, and DyIII cations. Compound Dy2Mn4-P2W15 exhibits a 1D ladder-like chain structure based on sandwich-type segments and dysprosium cations as linkers, which are further connected into a three-dimensional open framework by sodium cations. The title compound was structurally and compositionally characterized in solid state by single-crystal XRD, powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric (TGA), and elemental analyses. Further, the absorption and emission electronic spectra in aqueous solutions of Dy2Mn4-P2W15 and Mn4-P2W15 were studied. Also, magnetic properties were studied and compared with the magnetic behavior of [Mn4(H2O)2(P2W15O56)2]16−.

Observation of Cooperative Electronic Quantum Tunneling: Increasing Accessible Nuclear States in a Molecular Qudit

As an extension of two-level quantum bits (qubits), multilevel systems, so-called qu dits, where d represents the Hilbert space dimension, have been predicted to reduce the number of iterations in quantum-computation algorithms. This has been tested in the well-known [TbPc2]0 single-molecule magnet (SMM), which allowed implementation of the Grover algorithm in a single molecular unit. In the quest for molecular systems possessing an increased number of accessible nuclear spin states, we explore herein a dimeric Tb2-SMM via single-crystal μ-SQUID measurements at sub-Kelvin temperatures. We observe ferromagnetic interactions between the TbIII ions and cooperative quantum tunneling of the electronic spins with spin ground state | J z = ±6⟩. Strong hyperfine coupling with the TbIII nuclear spins leads to a multitude of spin-reversal paths, leading to seven strong hyperfine-driven tunneling steps in the hysteresis loops. Our results show the possibility of reading out the TbIII nuclear spin states via cooperative tunneling of the electronic spins, making the dimeric Tb2-SMM an excellent nuclear spin qu dit candidate with d = 16.

Coordination ability of amino acid hydrazide ligands and their influence on magnetic properties in copper(II) coordination polymers

Newly synthesized amino acid hydrazide ligands (L1 = N,N′-di-L-leucine hydrazide; L2 = N,N′-di-L-phenylalanine hydrazide) have shown excellent reactivity and stability, as well as extraordinary coordination ability. Reactions of L1/L2 with copper(II) ions and 4,4′-bipyridine (4,4′-bpy) as a secondary spacer yielded new coordination polymers {Cu(L1)0.5(4,4′-bpy)(H2O)(NO3)}n·1.5nH2O (1) and {Cu3(L2)2(4,4′-bpy)(H2O)2}n(NO3)2n·3nH2O (2). UV/vis spectroscopy together with structural analysis showed that the deprotonated ligands L12−/L22− with six available donor atoms per ligand have the ability for strong chelation to copper(II) ions, acting as bis-bidentate (L12−) and bridging bi + tridentate (L22−) ligands. Compound 1 contains copper(II) ions simultaneously bridged with short hydrazide bridges (4.725 A) and long 4,4′-bpy spacers (11.144 A) forming a two-dimensional coordination network. In compound 2, a pair of L22− molecules bridges three copper(II) ions, which are further interconnected with 4,4′-bpy into an overall one-dimensional chain-like structure. Although bulkier, the phenylalanine ligand (L2) was found to be more flexible compared to the leucine ligand (L1), exhibiting additional intramolecular contact: cation–π interaction. In both compounds, the hydrazide (–N–N–) bridge mediates the antiferromagnetic interaction between copper(II) ions. Hydrogen bonds have a strong influence on the crystal packing and physical (magnetic) properties. The reported compounds are first examples of hydrazide-bridged metal centres featuring amino acid-based ligands.