Field-Induced Single-Ion Magnets Based on Enantiopure Chiral β‑Diketonate Ligands

A pair of homochiral β-diketonate ligands (+)-3-trifluoroacetyl)­camphor (<i>d</i>-Htfc) and (−)-3-trifluoroacetyl)­camphor (<i>l</i>-Htfc) were used to construct two enantiomeric pairs of Dy­(III) single-ion magnets [Dy­(<i>d</i>-tfc)₃(bpy)]₂ (<i>d</i>-<b>1</b>)/[Dy­(<i>l</i>-tfc)₃(bpy)]₂ (<i>l</i>-<b>1</b>) (bpy = 2,2′-bipyridine) and [Dy­(<i>d</i>-tfc)₃(phen)]·2H₂O (<i>d</i>-<b>2</b>)/[Dy­(<i>l</i>-tfc)₃(phen)] (<i>l</i>-<b>2</b>) (phen = 1,10-phenanthroline). The capping aromatic <i>N</i>,<i>N</i>′-donors have a dramatic influence on the structural and magnetic characteristics of the Dy­(III) β-diketonate enantiomeric pairs: the cocrystal of two homochiral Dy­(III) β-diketonate stereoisomers with the 2,2′-bipyridine ligand was formed, showing field-induced single-ion magnet behaviors with a two-step relaxation process, while no stereoisomerization happened for the homochiral Dy­(III) β-diketonate with the 1,10-phenanthroline coligand, exhibiting a single relaxation process of the magnetization only. The anisotropy barriers of <i>d</i>-<b>1</b> (36.5 and 46.1 K) are slightly smaller than those of <i>l</i>-<b>1</b> (37.0 and 49.3 K), while <i>d</i>-<b>2</b> has a larger energy barrier (30.5 K) with respect to <i>l</i>-<b>2</b> (25.1 K)

Field-Induced Single-Ion Magnets Based on Enantiopure Chiral β‑Diketonate Ligands

A pair of homochiral β-diketonate ligands (+)-3-trifluoroacetyl)­camphor (<i>d</i>-Htfc) and (−)-3-trifluoroacetyl)­camphor (<i>l</i>-Htfc) were used to construct two enantiomeric pairs of Dy­(III) single-ion magnets [Dy­(<i>d</i>-tfc)₃(bpy)]₂ (<i>d</i>-<b>1</b>)/[Dy­(<i>l</i>-tfc)₃(bpy)]₂ (<i>l</i>-<b>1</b>) (bpy = 2,2′-bipyridine) and [Dy­(<i>d</i>-tfc)₃(phen)]·2H₂O (<i>d</i>-<b>2</b>)/[Dy­(<i>l</i>-tfc)₃(phen)] (<i>l</i>-<b>2</b>) (phen = 1,10-phenanthroline). The capping aromatic <i>N</i>,<i>N</i>′-donors have a dramatic influence on the structural and magnetic characteristics of the Dy­(III) β-diketonate enantiomeric pairs: the cocrystal of two homochiral Dy­(III) β-diketonate stereoisomers with the 2,2′-bipyridine ligand was formed, showing field-induced single-ion magnet behaviors with a two-step relaxation process, while no stereoisomerization happened for the homochiral Dy­(III) β-diketonate with the 1,10-phenanthroline coligand, exhibiting a single relaxation process of the magnetization only. The anisotropy barriers of <i>d</i>-<b>1</b> (36.5 and 46.1 K) are slightly smaller than those of <i>l</i>-<b>1</b> (37.0 and 49.3 K), while <i>d</i>-<b>2</b> has a larger energy barrier (30.5 K) with respect to <i>l</i>-<b>2</b> (25.1 K)

Field-Induced Single-Ion Magnets Based on Enantiopure Chiral β‑Diketonate Ligands

A pair of homochiral β-diketonate ligands (+)-3-trifluoroacetyl)­camphor (<i>d</i>-Htfc) and (−)-3-trifluoroacetyl)­camphor (<i>l</i>-Htfc) were used to construct two enantiomeric pairs of Dy­(III) single-ion magnets [Dy­(<i>d</i>-tfc)₃(bpy)]₂ (<i>d</i>-<b>1</b>)/[Dy­(<i>l</i>-tfc)₃(bpy)]₂ (<i>l</i>-<b>1</b>) (bpy = 2,2′-bipyridine) and [Dy­(<i>d</i>-tfc)₃(phen)]·2H₂O (<i>d</i>-<b>2</b>)/[Dy­(<i>l</i>-tfc)₃(phen)] (<i>l</i>-<b>2</b>) (phen = 1,10-phenanthroline). The capping aromatic <i>N</i>,<i>N</i>′-donors have a dramatic influence on the structural and magnetic characteristics of the Dy­(III) β-diketonate enantiomeric pairs: the cocrystal of two homochiral Dy­(III) β-diketonate stereoisomers with the 2,2′-bipyridine ligand was formed, showing field-induced single-ion magnet behaviors with a two-step relaxation process, while no stereoisomerization happened for the homochiral Dy­(III) β-diketonate with the 1,10-phenanthroline coligand, exhibiting a single relaxation process of the magnetization only. The anisotropy barriers of <i>d</i>-<b>1</b> (36.5 and 46.1 K) are slightly smaller than those of <i>l</i>-<b>1</b> (37.0 and 49.3 K), while <i>d</i>-<b>2</b> has a larger energy barrier (30.5 K) with respect to <i>l</i>-<b>2</b> (25.1 K)

Syntheses, Crystal Structures, and Magnetic Properties of Two <i>p</i>-<i>tert</i>-Butylsulfonylcalix[4]arene Supported Cluster Complexes with a Totally Disordered Ln₄(OH)₄ Cubane Core

Two new sandwich calix[4]­arene-supported cluster complexes, [Ln₄(OH)₄­(TBSOC)₂­(H₂O)₄­(CH₃OH)₄]­·4H₂O (H₄TBSOC = <i>p</i>-<i>tert</i>-butylsulfonylcalix­[4]­arene; Ln = Dy, <b>1</b>; Ln = Ho, <b>2</b>), have been prepared and characterized. An X-ray crystallographic study reveals that both complexes contain a holistically disordered [Ln₄(OH)₄]⁸⁺ cubane cluster core, which is sandwiched between two antiparallel calixarene macrocycles. Magnetic investigations indicate that complex <b>1</b> displays slow magnetization relaxation typical for single-molecule magnets in the absence of a static applied dc field, with the Δ<i><i>E</i>/k</i>_B parameter of 22.9 K, the largest value for the calixarene-supported pure 4f single-molecule magnets so far, whereas complex <b>2</b> does not show any relaxation of the magnetization above 2 K

Syntheses, Crystal Structures, and Magnetic Properties of Two <i>p</i>-<i>tert</i>-Butylsulfonylcalix[4]arene Supported Cluster Complexes with a Totally Disordered Ln₄(OH)₄ Cubane Core

Two new sandwich calix[4]­arene-supported cluster complexes, [Ln₄(OH)₄­(TBSOC)₂­(H₂O)₄­(CH₃OH)₄]­·4H₂O (H₄TBSOC = <i>p</i>-<i>tert</i>-butylsulfonylcalix­[4]­arene; Ln = Dy, <b>1</b>; Ln = Ho, <b>2</b>), have been prepared and characterized. An X-ray crystallographic study reveals that both complexes contain a holistically disordered [Ln₄(OH)₄]⁸⁺ cubane cluster core, which is sandwiched between two antiparallel calixarene macrocycles. Magnetic investigations indicate that complex <b>1</b> displays slow magnetization relaxation typical for single-molecule magnets in the absence of a static applied dc field, with the Δ<i><i>E</i>/k</i>_B parameter of 22.9 K, the largest value for the calixarene-supported pure 4f single-molecule magnets so far, whereas complex <b>2</b> does not show any relaxation of the magnetization above 2 K

Arraying Octahedral {Cr₂Dy₄} Units into 3D Single-Molecule-Magnet-Like Inorganic Compounds with Sulfate Bridges

Two novel 3D pure inorganic compounds based on [Cr₂Dy₄(μ₄-O)₂(μ₃-OH)₄]¹⁰⁺ cluster units and sulfate anions are presented. Both complexes exhibit single-molecule-magnet (SMM)-like behavior. Permutation of the magnetic moment direction among SMM-like cluster units has a significant effect on the performance of molecular nanomagnets, and directional consistency shows obvious advantages

Conjugated Donor–Acceptor Polymers Entailing Pechmann Dye-Derived Acceptor with Siloxane-Terminated Side Chains Exhibiting Balanced Ambipolar Semiconducting Behavior

We present four conjugated donor–acceptor (D–A) polymers PBPDT-Si, PBPDSe-Si, PBPDT, and PBPDSe entailing a new electron acceptor Pechmann dye framework, i.e., bipyrrolylidene-2,2′(1<i>H</i>,1′<i>H</i>)-dione (BPD), and thiophene and selenophene as the respective electron donors. PBPDT-Si and PBPDSe-Si contain siloxane-terminated side chains, while PBPDT and PBPDSe bear branching alkyl chains. The respective HOMO energies of PBPDT-Si and PBPDSe-Si are slightly higher than those of PBPDT and PBPDSe, whereas the respective LUMO energies of PBPDT-Si and PBPDSe-Si are slightly lower than those of PBPDT and PBPDSe. The results reveal that (i) thin films of all four polymers show ambipolar semiconducting performances under a nitrogen atmosphere, (ii) hole and electron mobilities are more balanced for PBPDT-Si and PBPDSe-Si, and (iii) the employment of siloxane-terminated side chains is beneficial for improving charge transporting compared to branching alkyl side chains. Thin film hole and electron mobilities of PBPDT-Si can reach 0.74 and 0.87 cm² V^–1 s^–1, respectively

Vibrationally Resolved Photoelectron Spectroscopy of the Model GFP Chromophore Anion Revealing the Photoexcited S₁ State Being Both Vertically and Adiabatically Bound against the Photodetached D₀ Continuum

The first excited state of the model green fluorescence protein (GFP) chromophore anion (S₁) and its energy level against the electron-detached neutral radical D₀ state are crucial in determining the photophysics and the photoinduced dynamics of GFP. Extensive experimental and theoretical studies, particularly several very recent gas-phase investigations, concluded that S₁ is a bound state in the Franck–Condon vertical region with respect to D₀. However, what remains unknown and challenging is if S₁ is bound adiabatically, primarily due to lack of accurate experimental measurements as well as due to the close proximity in energy for these two states that even sophisticated high-level ab initio calculations cannot reliably predict. Here, we report a negative ion photoelectron spectroscopy study on the model GFP chromophore anion, the deprotonated <i>p</i>-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI^–) taken under low-temperature conditions with improved energy resolution. Despite the considerable size and low symmetry of the molecule, resolved vibrational structures were obtained with the 0–0 transition being the most intense peak. The adiabatic (ADE) and vertical detachment (VDE) energies therefore are determined both to be 2.73 ± 0.01 eV, indicating that the detached D₀ state is 0.16 eV higher in energy than the photon excited S₁ state. The accurate ADE and VDE values and the well-resolved photoelectron spectra reported here provide much needed robust benchmarks for future theoretical investigations

Vibrationally Resolved Photoelectron Spectroscopy of the Model GFP Chromophore Anion Revealing the Photoexcited S₁ State Being Both Vertically and Adiabatically Bound against the Photodetached D₀ Continuum

The first excited state of the model green fluorescence protein (GFP) chromophore anion (S₁) and its energy level against the electron-detached neutral radical D₀ state are crucial in determining the photophysics and the photoinduced dynamics of GFP. Extensive experimental and theoretical studies, particularly several very recent gas-phase investigations, concluded that S₁ is a bound state in the Franck–Condon vertical region with respect to D₀. However, what remains unknown and challenging is if S₁ is bound adiabatically, primarily due to lack of accurate experimental measurements as well as due to the close proximity in energy for these two states that even sophisticated high-level ab initio calculations cannot reliably predict. Here, we report a negative ion photoelectron spectroscopy study on the model GFP chromophore anion, the deprotonated <i>p</i>-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI^–) taken under low-temperature conditions with improved energy resolution. Despite the considerable size and low symmetry of the molecule, resolved vibrational structures were obtained with the 0–0 transition being the most intense peak. The adiabatic (ADE) and vertical detachment (VDE) energies therefore are determined both to be 2.73 ± 0.01 eV, indicating that the detached D₀ state is 0.16 eV higher in energy than the photon excited S₁ state. The accurate ADE and VDE values and the well-resolved photoelectron spectra reported here provide much needed robust benchmarks for future theoretical investigations

Multiscale Assembly of Grape-Like Ferroferric Oxide and Carbon Nanotubes: A Smart Absorber Prototype Varying Temperature to Tune Intensities

Ideal electromagnetic attenuation material should not only shield the electromagnetic interference but also need strong absorption. Lightweight microwave absorber with thermal stability and high efficiency is a highly sought-after goal of researchers. Tuning microwave absorption to meet the harsh requirements of thermal environments has been a great challenge. Here, grape-like Fe₃O₄-multiwalled carbon nanotubes (MWCNTs) are synthesized, which have unique multiscale-assembled morphology, relatively uniform size, good crystallinity, high magnetization, and favorable superparamagnetism. The Fe₃O₄-MWCNTs is proven to be a smart microwave-absorber prototype with tunable high intensities in double belts in the temperature range of 323–473 K and X band. Maximum absorption in two absorbing belts can be simultaneously tuned from ∼−10 to ∼−15 dB and from ∼−16 to ∼−25 dB by varying temperature, respectively. The belt for reflection loss ≤−20 dB can almost cover the X band at 323 K. The tunable microwave absorption is attributed to effective impedance matching, benefiting from abundant interfacial polarizations and increased magnetic loss resulting from the grape-like Fe₃O₄ nanocrystals. Temperature adjusts the impedance matching by changing both the dielectric and magnetic loss. The special assembly of MWCNTs and magnetic loss nanocrystals provides an effective pathway to realize excellent absorbers at elevated temperature