Dual-radical-based molecular anisotropy and synergy effect of semi-conductivity and valence tautomerization in a photoswitchable coordination polymer.

Organic radicals are widely used as linkers or ligands to synthesize molecular magnetic materials. However, studies regarding the molecular anisotropies of radical-based magnetic materials and their multifunctionalities are rare. Herein, a photoisomerizable diarylethene ligand was used to form {[Co(3,5-DTSQ)(3,5-DTCat)](6F-DAE-py)}·3CHCN·HO (·3CHCN·HO, 6F-DAE-py = 1,2-bis(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene), a valence-tautomeric (VT) coordination polymer.

Structural, magnetic and theoretical analyses of anionic and cationic phthalocyaninato-terbium(III) double-decker complexes: magnetic relaxation higher ligand-field sublevels enhanced by oxidation.

Crystal structural and magnetic analyses were performed for the anionic (1-) and cationic (1+) forms of phthalocyaninato-Tb3+ double-decker single-molecule magnets (SMMs). Both charged species showed slow magnetic relaxations and magnetic hysteresis characteristics for SMMs. 1+ showed longer magnetic relaxation times (τ) and higher activation energy for spin reversal (ΔE) than 1- did.

Highly Oxidized States of Phthalocyaninato Terbium(III) Multiple-Decker Complexes Showing Structural Deformations, Biradical Properties and Decreases in Magnetic Anisotropy.

Presented here is a comprehensive study of highly oxidized multiple-decker complexes composed of Tb and Cd ions and two to five phthalocyaninato ligands, which are stabilized by electron-donating n-butoxy groups. From X-ray structural analyses, all the complexes become axially compressed upon ligand oxidation, resulting in bowl-shaped distortions of the ligands. In addition, unusual coexistence of square antiprism and square prism geometries around metal ions was observed in +4e charged species.

Manipulation of the Coordination Geometry along the C Rotation Axis in a Dinuclear Tb Triple-Decker Complex via a Supramolecular Approach.

A supramolecular complex (1⋅C ) was prepared by assembling (C60-Ih)[5,6]fullerene (C ) with the dinuclear Tb triple-decker complex [(TPP)Tb(Pc)Tb(TPP)] (1: Tb =trivalent terbium ion, Pc =phthalocyaninato, TPP =tetraphenylporphyrinato) with quasi-D symmetry to investigate the relationship between the coordination symmetry and single-molecule magnet (SMM) properties. Tb -Pc triple-decker complexes (Tb Pc ) have an important advantage over Tb -Pc double-decker complexes (TbPc ) since the magnetic relaxation processes correspond to the Zeeman splitting when there are two 4f spin systems. The two Tb sites of 1 are equivalent, and the twist angle (φ) was determined to be 3.

A new member of a class of rod-like Mn single molecule magnets using 2-(pyridine-2-ly)propan-2-ol.

This paper reports on the synthesis, structure and magnetic properties of a new type of rod like Mn metal cluster, [MnO(OH)(OMe)(dmhmp)(OCPh)(HO)] (6) where the ligand (dmhmpH) is 2-(pyridine-2-yl)propan-2-ol. Compound (6) was obtained by reacting MnCl·4HO with dmhmpH in the presence of benzoic salt and EtN. The resulting crystalline material is assigned to the triclinic space group 1̄.

A single-ion single-electron cerrous magnet.

Herein, we present monometallic Ln(iii) complexes [LLn(NO)] [where Ln = Ce (1) and La (2)] assembled from a simple reaction of the respective lanthanide nitrate hydrate and a bulky phosphonic diamide BuPO(NHPr) ligand (L), where complex 1 behaves as a single-ion single-electron magnet under a small applied magnetic field. The Ce(iii) ion occupies a nine-coordinate distorted muffin-like coordination environment. The combination of direct and Raman process dominates the relaxation dynamics in 1 under the applied dc field.

Boosting axiality in stable high-coordinate Dy(iii) single-molecule magnets.

A new nine-coordinate, air-stable Dy(iii) single-ion magnet has been successfully isolated. Our in silico studies demonstrate that through carefully modulating the ligand electronics, the axiality can be boosted to generate Ucal barriers of over 600 K.

Structure Switching and Modulation of the Magnetic Properties in Diarylethene-Bridged Metallosupramolecular Compounds by Controlled Coordination-Driven Self-Assembly.

We report three self-assembled iron complexes that comprised an anti-parallel open form (o-L ), a parallel open form (o-L ), and a closed form (c-L) of diarylethene conformers. Under kinetic control, Fe (o-L ) was isolated, which exhibited a dinuclear structure with diamagnetic properties. Under light-irradiation control, Fe (c-L) was prepared and exhibited paramagnetism and spin-crossover behaviour.

Dysprosium Single-Molecule Magnets with Bulky Schiff Base Ligands: Modification of the Slow Relaxation of the Magnetization by Substituent Change.

The synthesis, and magnetic and photoluminescence investigations of two bifunctional dysprosium complexes based on tridentate Schiff base ligands is reported. Magnetic investigations reveal a genuine single-molecule magnet (SMM) behavior, with out-of-phase signals up to 60 K, and tunable emission arising from the Schiff base ligands.

Thermodynamic stability and structure in aqueous solution of the [Cu(PTA)] complex (PTA = aminophosphine‑1,3,5‑triaza‑7‑phosphaadamantane).

The chemistry of copper(I) with water-soluble phosphines is an emergent area of study which has the objective of finding ligands that stabilize copper in its lower oxidation state. Cu(I) has been found relevant in the mechanism of copper transports into cells, and the accessibility of this oxidation state has implications in oxidative stress processes. For these reasons the possibility to deal with stable, water soluble copper(I) is an attractive approach for devising new biologically relevant metal-based drugs and chelating agents.

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 [TbPc] 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 Tb-SMM via single-crystal μ-SQUID measurements at sub-Kelvin temperatures.

Slow Magnetic Relaxation in a Palladium-Gadolinium Complex Induced by Electron Density Donation from the Palladium Ion.

Incorporating palladium in the first coordination sphere of acetato-bridged lanthanoid complexes, [Pd Ln (H O) (AcO) ]⋅2 AcOH (Ln=Gd (1), Y (2), Gd Y (3), Eu (4)), led to significant bonding interactions between the palladium and the lanthanoid ions, which were demonstrated by experimental and theoretical methods. We found that electron density was donated from the d Pd ion to Gd ion in 1 and 3, leading to the observed slow magnetic relaxation by using local orbital locator (LOL) and X-ray absorption near-edge structure (XANES) analysis. Field-induced dual slow magnetic relaxation was observed for 1 up to 20 K.

Comparison of the Magnetic Anisotropy and Spin Relaxation Phenomenon of Dinuclear Terbium(III) Phthalocyaninato Single-Molecule Magnets Using the Geometric Spin Arrangement.

Herein we report the synthesis and characterization of a dinuclear Tb single-molecule magnet (SMM) with two [TbPc] units connected via a fused-phthalocyaninato ligand. The stable and robust complex [(obPc)Tb(Fused-Pc)Tb(obPc)] (1) was characterized by using synchrotron radiation measurements and other spectroscopic techniques (ESI-MS, FT-IR, UV). The magnetic couplings between the Tb ions and the two π radicals present in 1 were explored by means of density functional theory (DFT).

Supramolecular Approach for Enhancing Single-Molecule Magnet Properties of Terbium(III)-Phthalocyaninato Double-Decker Complexes with Crown Moieties.

A Tb -phthalocyaninato double-decker ([1] ) single-molecule magnet (SMM) having four 15-crown-5 moieties in one of the ligands was synthesized, and its dimerization and magnetic properties were studied in an attempt to utilize the supramolecular aggregation for enhancing the SMM properties. Aggregation of [1] to form [1 K ] in the presence of K ions was studied by using UV/Vis-NIR absorption and NMR spectroscopies. For the magnetic measurements, [1] and [1 K ] were dispersed in poly(methyl methacrylate) (PMMA).

Slow Magnetic Relaxation and Single-Molecule Toroidal Behaviour in a Family of Heptanuclear {Cr Ln } (Ln=Tb, Ho, Er) Complexes.

The synthesis, magnetic properties, and theoretical studies of three heterometallic {Cr Ln } (Ln=Tb, Ho, Er) complexes, each containing a metal topology consisting of two Ln triangles connected via a Cr linker, are reported. The {CrTb } and {CrEr } analogues display slow relaxation of magnetization in a 3000 Oe static magnetic field. Single-crystal measurements reveal opening up of the hysteresis loop for {CrTb } and {CrHo } molecules at low temperatures.

Transition Metal Single-Molecule Magnets: A {Mn} Nanosized Cluster with a Large Energy Barrier of ∼60 K and Magnetic Hysteresis at ∼5 K.

The first {Mn} cluster (1) has been prepared from carboxylate ions and the chelating/bridging ligand α-methyl-2-pyridine-methanol. Compound 1 possesses a unique nanosized structural topology with one of the largest energy barriers reported to-date for high-nuclearity 3d-metal clusters. Single-crystal magnetic hysteresis studies reveal the presence of hysteresis loops below 5 K, one of the highest temperatures below which molecular hysteresis has been observed for 3d-based SMMs.

Nuclear Spin Isomers: Engineering a Et N[DyPc ] Spin Qudit.

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.

Proton Control of the Lanthanoid Single-Ion Magnet Behavior of a Double-Decker Complex with an Indolenine-Substituted Annulene Ligand.

Two double-decker complexes with annulene ligands functionalized with indolenine groups were synthesized and characterized. The position of the proton acting as a counterion on one of the four indolenine nitrogen atoms was determined by using DFT calculations. Deprotonation and protonation of the complex induced by adding a base and an acid, respectively, were monitored by using NMR spectroscopy.

NMR analysis of an Fe(i)-carbene complex with strong magnetic anisotropy.

A tricoordinated Fe complex with two cyclic-alkyl(amino) carbene (cAAC) and one chlorido ligand, (cAAC)FeCl (1), is studied by means of H NMR spectroscopy and DFT calculations. Due to the cAAC ligands, which can take significant amounts of spin density from the metal center, and due to the magnetic anisotropy of the Fe ion (P. P.

How Ions Arrange in Solution: Detailed Insight from NMR Spectroscopy of Paramagnetic Ion Pairs.

Ion pairing between the paramagnetic anion [Tb(obPc) ] (obPc=2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato), which has a very large magnetic anisotropy, with various diamagnetic counterions [P(Ph) ] (1 a), [As(Ph) ] (1 b), bis(triphenylphosphine)iminium ([PPN] , 1 c) and tetra-n-butylammonium ([TBA] , 1 d) was studied by means of H, C, N, and P NMR spectroscopy in solution at various temperatures. The influence of the paramagnetic anion on the NMR spectroscopy properties of the diamagnetic cations allowed a detailed insight into the distances and relative orientations of the paired ions. Isotropic tumbling models for the description of the quaternary cations are inaccurate, particularly for [TBA] with its flexible butyl chains.

Insights into the cytotoxic activity of the phosphane copper(I) complex [Cu(thp)][PF].

The phosphane Cu(I) complex [Cu(thp)][PF], 1 (thp=tris(hydroxymethyl)phosphane) shows notable in vitro antitumour activity against a wide range of solid tumours. Uptake experiments performed in 1-treated colon cancer cells by atomic absorption spectrometry, reveal that the antiproliferative activity is consistent with the intracellular copper content. The solution chemistry of this agent, investigated by means of X-ray Absorption Spectroscopy and spectrophotometric titrations in aqueous media, indicates that 1 is labile giving coordinative unsaturated [Cu(thp)] species (n=3 and 2) at micromolar concentrations.

Radical Monocationic Guanidino-Functionalized Aromatic Compounds (GFAs) as Bridging Ligands in Dinuclear Metal Acetate Complexes: Synthesis, Electronic Structure, and Magnetic Coupling.

In this work, the oxidation of several new dinuclear metal (M) acetate complexes of the redox-active guanidino-functionalized aromatic compound (GFA) 1,2,4,5-tetrakis(tetramethylguanidino)benzene (1) was studied. The complexes [1{M(OAc)2}2] (M = Ni or Pd) were oxidized to the radical monocationic complexes [1{M(OAc)2}2](+ •). From CV (cyclic voltammetry) measurements, the Gibbs free enthalpy for disproportionation of [1{M(OAc)2}2](+ •) into [1{M(OAc)2}2] and [1{M(OAc)2}2](2+) could be estimated to be roughly +20 kJ mol(-1) in CH2Cl2 solution.

α-Substituted Bis(octabutoxyphthalocyaninato)Terbium(III) Double-Decker Complexes: Preparation and Study of Protonation by NMR and DFT.

Synthesis of the anionic, α-substituted, bis(phthalocyaninato)Tb(III) complex [Tb(α-obPc)2](-) ([1](-)) (obPc = α-octabutoxyphthalocyaninato) leads to the isolation of its protonated form [1H](0). This complex was characterized by X-ray diffraction (XRD), mass spectroscopy (MS), infrared (IR) and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy. Crystal structure analysis did not allow localization of the additional proton, which is probably attached to the meso-N atom or isoindole-N atom of the phthalocyaninato ligand.

Ligand π-radical interaction with f-shell unpaired electrons in phthalocyaninato-lanthanoid single-molecule magnets: a solution NMR spectroscopic and DFT study.

The phthalocyaninato double-decker complexes [M(obPc)2 ](0) (M= Y(III) , Tb(III) , Dy(III) ; obPc=2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato), along with their reduced ([M(obPc)2 ](-) [P(Ph)4 ](+) ; M=Tb(III) , Dy(III) ) and oxidized ([M(obPc)2 ](+) [SbCl6 ](-) (M=Y(III) , Tb(III) ) counterparts were studied with (1) H, (13) C and 2D NMR. From the NMR data of the neutral (i.e.