Abstract Tuning the intrinsic bonding and mechanical behavior of MAX phases is crucial for tailoring their performance. In this work, a series of Ti3AlC2–xBx MAX phase ceramics were fabricated via spark plasma sintering, and we systematically investigated the effects of B substitution on their crystal structure, bonding characteristics, and mechanical properties through a combination of experiments and theoretical calculations. B substitution creates local electronic imbalance within the M–X layers, which in turn promotes carbon vacancy formation via charge compensation process. The interplay between B incorporation and Cv formation induces further structural relaxation and charge redistribution. As a result, the resistance to elastic failure and plastic deformation failure is enhanced by 27.6% and 76.0%, respectively, under the synergistic influence of M–X bonds and Cv. However, under high B concentrations, excessive Cv accumulation destabilizes the Ti3C2 layers and drives the formation of Ti2AlC. Overall, this work systematically unravels how B substitution modifies the Ti3AlC2 structure, offering valuable insights into the regulation of X-site chemistry and bonding in MAX phases.
Abstract β-Amyloid peptides N-truncated at Phe4 (Aβ4–x) contain an amino-terminal Cu- and Ni-binding (ATCUN) motif that can form high-affinity, redox-silent Cu2+ complexes. Human Aβ4–40/42 is present in the brains of individuals with and without Alzheimer’s disease, and soluble Aβ4–9 can be generated by neprilysin proteolysis of Aβ1–40/42 in vitro. These observations led to the proposal that Aβ4–x may be functional Cu2+-binding peptides. Because amyloid precursor protein is constitutively expressed in mammals, this study assessed whether murine Aβ4–x peptides retain the properties of the human analogues. Cu2+ coordination, binding affinity, and redox activity were compared for murine and human Aβ4–9 and Aβ4–16. The murine peptides formed Cu2+ complexes with spectroscopic parameters closely matching those of the human peptides. Competitive binding against glycylglycylhistidine gave conditional Cu2+ dissociation constants at pH 7.4 of 3–4 fM for murine Aβ4–x and 8–10 fM for human Aβ4–x. All Cu(Aβ4–x) complexes were redox-silent in an aminophenyl fluorescein/ascorbate assay. Thus, murine Aβ4–x has the chemical capacity required for a Cu2+-binding role if generated in vivo. However, because endogenous murine Aβ4–x has not been detected in wild-type mice, the present findings challenge the support for a broadly conserved physiological role for Aβ4–x in mammalian Cu2+ handling.
Abstract The kinetics of oxidative addition (OA) of 4-chlorobenzotrifluoride to a well-defined Pd0-NHC complex, [Pd(IPr)(PhC≡CPh)], has been investigated using electrochemical techniques. The influence of the concentration of the substrate and added amounts of the weakly coordinating ligand on kobs have been studied. The resulting OA product has been isolated and full characterized and is a dimeric species. Additionally, evidence supports a “cocktail-type” catalysis and the reductive elimination of the NHC ligand from the Pd center as a possible decomposition pathway. Finally, the influence of eight different NHC ligands on the oxidative addition has been evaluated.
Abstract BaZrS3 doped with Nd3+, Er3+, or Yb3+ shows structured near-infrared emission whose interpretation requires distinguishing the local coordination environments. Embedded-cluster CASSCF/NEVPT2 calculations with spin–orbit coupling in the complete 4fn configuration space compare Nd3+, Er3+, and Yb3+ in six-coordinate Zr-site and eight-coordinate Ba-site models, and breathing-coordinate scans quantify the sensitivity to the local Ln–S distance. Validation on Cs2NaLnCl6 shows that the complete state space brings the Er3+4I13/2 and 4I11/2 energies to within 0.5% of experiment, where the highest-multiplicity restriction leaves larger, multiplet-dependent errors. The two sites give comparable ground-multiplet widths but contrasting level patterns: the Zr-site ligand field is dominated by rank-four terms and the Ba-site field by rank-two terms, with opposite responses to the local bond length. Published low-temperature emission data are compatible with a Zr-like environment for the dominant Er3+ and Nd3+ emitters and, tentatively, a contracted Ba-like environment for the broadest Yb3+ population; ground-doublet g-tensors and susceptibilities provide discriminants for EPR and magnetometry, and restricted-active-space calculations calibrated on Er3+ in LaCl3 show that, within the static electronic models, the electric-dipole strength of Er3+ and Yb3+ is symmetry-suppressed at the Zr site whereas the Ba-site ions acquire a forced electric-dipole channel of comparable or larger strength.
Abstract Harnessing and tailoring spin dynamics at the molecular level is pivotal for advancing quantum information technologies and multifunctional materials. While α-diimine–Dy(III) β-diketonates have been extensively explored, β-diimine ligands remain largely unexplored as a ligand-field platform for modulating magnetic anisotropy and magneto-optical response in Dy(III) β-diketonates. Herein, we investigate β-diimine coligands as a tunable ligand-field platform in Dy(III) β-diketonate complexes, [Dy(dbm)3(bik-Et)] (1), [Dy(dbm)3(bik-Me)] (2), and [Dy(acac)3(bik-Et)] (3), where bik-R = bis(1-R-1H-imidazol-2-yl)methanone. Single-crystal X-ray diffraction reveals DyO6N2 coordination in distorted square antiprismatic (1, 3) and triangular dodecahedral (2) geometries, leading to distinct anisotropy-axis orientations. All complexes exhibit zero-field slow magnetic relaxation, and ab initio CASSCF/SINGLE_ANISO calculations reproduce Kramers doublet splitting and show qualitative correlations between coordination structure, electronic anisotropy, and relaxation pathways. Temperature-dependent photoluminescence demonstrates that these complexes function as luminescent thermometers with high relative sensitivity up to 2.98% K–1. Together, these results establish β-diimine coordination as a complementary ligand-field platform for modulating coordination geometry, Kramers-doublet structure, magnetic anisotropy, relaxation behavior, and luminescent thermometry in Dy(III) β-diketonate single-ion magnets.
