Syntheses and Crystal Structures of Two Tin(Ⅳ) Complexes with Aminosilane Bearing Ligand

Aminosilane bearing bulky substituents on nitrogen： LH2 （L = Me2Si（NDipp＇）2, Dipp = 2,6-diisopropylphenyl） was reacted with BuLi in toluene. The resulting bulky chelating dianion Me2Si（NDipp）2 was used to synthesize the unusual spirocyclic heterotriatomic complex [MeESi（NDipp）2]ESn （1） by its reaction with SnCl4 and the bulky heterotriatomic complex Me2Si（NDipp）2SnPh2 （2） with Ph2SnC12. 1 belongs to the monoclinic system, space group P21/n with a = 13.193（2）, b = 20.663（3）, c = 20.403（3）A, β = 99.954（2）°, V = 5478.3（15） A3, C55H85.5N4Si2Sn, Mr = 977.64, Z = 4, Dc. = 1.185 Mg/m3, μ（MoKa） = 0.547 mm-1, F（000） = 2086, S = 1.000, the final R = 0.0614 and wR = 0.1322 for 14446 observed reflections （1 〉 2σ（I）） and R = 0.0797 and wR = 0.1456 for all data. 2 belongs to the triclinic system, space group P1 with a = 10.36（15）, b = 13.204（7）, c = 14.363（7） A, a = 90.214（10）, β = 106.182（7）, y = 109.854（8）°, V = 1764.4（15） A3, C38HsoN2SiSn, M,. = 681.58, Z = 2, Dc = 1.283 Mg/m^3,μ（MoKa） = 0.785 mm-1, F（000） = 712, S = 1.002, the final R = 0.0498 and wR = 0.0955 for 7533 observed reβections （I 〉 2σ（I）） and R = 0.0676 and wR = 0.1018 for all data. In the structure of 1, the tin atom is located in the spirocyclic center of the two fused four-membered SnN2Si rings. The two complexes were characterized by ^1H NMR, elemental analysis, and single-crystal X-ray structural analysis.

Chelating ligand-bridged IO-Gd nanoparticles with enhanced contrast performance for dual-mode MRI

Magnetic resonance imaging(MRI)is a non-invasive medical imaging technique that has been widely applied in the clinical diagnosis of diseases across various fields.Currently,there is a dearth of high-performance dual-mode contrast agents that provide precise diagnostic information for complex diseases.In this study,iron oxide-gadolinium nanoparticles(IO-Gd NPs)bridged by hydrophilic ligand ethylenedi-amine tetramethylenephosphonic acid(EDTMP)are designed inspired by Solomon-Bloembergen-Morgan(SBM)theory,where T_(1)and T_(2)relaxivity increase with a reduction in Gd content.In particular,the NPs with minimum Gd content exhibit excellent dual-mode contrast performance(r_(1)=94.42 mM^(−1)s^(−1),r_(2)=343.62 mM^(−1)s^(−1)).The underlying mechanism is that the bridged EDTMP coordinate limits Gd tum-bling and forces Gd^(3+)to expose itself to the surface of the NPs.This provides more opportunities for water molecules to coordinate with Gd^(3+)and significantly enhances proton relaxivity.Moreover,the hy-drophilicity of the ligand enhances the water dispersion stability of the NPs and increases the exchange rate of water protons near the NPs,further enhancing the dual-mode contrast effect.Finally,the biocom-patibility and in vitro/vivo imaging performances of the IO@EDTMP-Gd NPs are systematically evaluated,and the results demonstrate their potential as dual-mode contrast agents.This study provides a new strategy for developing dual-mode MRI contrast agents that can further improve the accuracy of MRI in the diagnosis of complex diseases.

Coordination chemistry of surface-associated ligands for solid-liquid adsorption of rare-earth elements

General guidelines for the design of ligands for the enrichment of rare-earth elements by solid-liquid adsorption are described using coordination chemistry.Relevant properties of ligands include selectivity of metal ions based on adjustment of donor atom polarizability,denticity,and the pKarange of the binding sites.The selectivity of solid-phase materials for the enrichment of rare-earth ions by the ligand design guidelines is outlined,with special consideration of additional variable factors including steric hindrance,saturated binding sites,variability in speciation caused by the identity of counterions and ionic strength,and size-exclusivity in ligands stemming from differences in bite angle,preo rganization of ligands,or intraligand interactions.This review analyzes some principles of selectivity of rare-earth elements with ligands organized by donor type from examples collected from reports published between 2009 and 2021.

Tetravalent Terbium Chelates: Stability Enhancement and Property Tuning

Coordination chemistry of rare-earth elements has been dominated by the+3 oxidation state.Complexes with higher-valence lanthanide ions are synthetically challenging but are of fundamental research interest and significance as advanced molecular materials.Herein,four tetravalent terbium complexes(2-5)of the common formula[Tb(OSiPh3)4L](L=ethylene glycol dimethyl ether(DME),2,2’-bipyridine(bpy),2,2’-bipyrimidine(bpym),and 1,10-phenanthroline(phen))are reported.Crystallographic analyses reveal in each of these complexes a hexacoordinate Tb(IV)ion situated in a distorted octahedral coordination environment formed by four triphenylsi-loxido ligands and a bidentate chelating ligand.The use of chelating ligands enhances the stability of the resulting complexes over their THF solvate precursor.More significantly,the aromatic N-chelating ligands have been found to tune effectively the electronic structures of the complexes,as evidenced by the sizable potential shifts observed for the quasi-reversible redox Tb(IV/III)process and by the changes in their absorption spectra.The experimental findings are augmented with quantum theoretical calculations in which the ligandπ-donation to the 5d orbitals of the Tb(IV)center is found to be primarily responsible for stability enhancement and the corresponding changes of physical properties observed.Magnetic measurements and results from electron paramagnetic resonance studies produced small absolute values of zero-field splittings of these complexes,ranging from 0.1071(22)to 1.1484(112)cm-1 and comparable to the values reported for analogous Tb(IV)complexes.

Synthesis and Structural Characterization of a Dinuclear Copper（Ⅱ） Complex with p-tert-Butylsulfonylcalix[4]arene

The X-ray crystallographic structure was reported for a dinuclear copper（Ⅱ） complex with a tetraanionic ligand of p-tert-butylsulfonylcalix[4]arene [Cu2L（CH3OH）6]·4CH3OH （H4L=p-tert-butylsuffonylcalix[4]arene）. The complex belongs to triclinic system, P1^-- space group, with a = 1.2303（3） nm, b = 1.2377（3） nm, c = 1.3110（3） nm, a =66.862（4）°, β= 67.206（4）°, γ=61.711（3）°, Z= 1, V= 1.5659（7） nm^3, Dc= 1.371 g/cm^3, F（000） = 682,μ（Mo Kα） = 0.883 mm^-1, R1 =0.0325, wR2=0.0870. In this complex, the calix[4]arene acts as a bis-tridentate chelating ligand with the 1,2-alternate conformation.