Dynamic Cantilever Magnetometry of Paramagnetism with Slow Relaxation

Dynamic cantilever magnetometry is a sensitive method that has been widely used in studying magnetic anisotropy in ferromagnetic materials and Fermi surface in quantum materials.We study a cobalt-iridium metal-metalloligand coordination polymer using dynamic cantilever magnetometry.The experimental data of dynamic cantilever magnetometry are well explained using the proposed model for Langevin paramagnetism with slow relaxation.Based on the proposed model,we calculate the magnetization and magnetic susceptibility of paramagnetic materials from frequency shifts of a cantilever.The extracted magnetization and magnetic susceptibility are consistent with those obtained from conventional DC and AC magnetometry.The proposed slow relaxation picture is probably a general model for explaining dynamic cantilever magnetometry data of paramagnetic materials,including previously observed dynamic cantilever magnetometry data of paramagnetic metals[Gysin et al.2011 Nanotechnology22285715].

Boosting the proton conduction in a magnetic dysprosium-organic framework by introducing conjugate NH_(4)^(+)-NH_(3)pairs

Metal-organic frameworks(MOFs)with inherent porosity and suspended acidic groups are promising proton conducting materials in water or aqua-ammonia media.Herein we report a new lanthanide phosphonate,namely,Dy_(2)(amp_(2)H_(2))_(2)(mal)(H_(2)O)_(2)·5H2O(MDAF-6).It possesses a 3D open-framework structure,and shows a high NH_(3)adsorption capacity of 142.4 cm^(3)/g at P/P0=0.98 at 298 K due to acid-base interaction.Interestingly,the proton conductivity of MDAF-6-NH3 is enhanced by five orders of magnitude compared to MDAF-6 after 8.5 h exposure in saturated NH_(3)-H_(2)O vapor,indicating the importance of coexistent conjugate acid-base pairs of H_(3)O+-H_(2)O and NH_(4)^(+)-NH_(3)in promoting proton conduction.Magnetic studies of MDAF-6 revealed slow magnetization relaxation under zero dc field,characteristic of singlemolecule magnet behavior.This work provides not only a new multifunctional MOF material,but also a new strategy to improve proton conduction in aqua-ammonia medium.

Chiral metal phosphonates: assembly, structures and functions

As an important class of inorganic-organic hybrid materials, metal phosphonates can exhibit versatile structures, interesting functions and high water and thermal stabilities. Despite a large number of metal phosphonates reported in the past two decades,the development of chiral metal phosphonates is still in its infancy. This review summarizes the current status in this topical field including the synthetic strategies, the crystal structures of chiral metal phosphonates reported thus far, and their physical and chemical properties. Future challenges in this promising field are also discussed.

M_2(pbtcH)(phen)_2(H_2O)_2[M(Ⅱ)=Co,Ni]:Mixed-ligated metal phosphonates based on 5-phosphonatophenyl-1,2,4-tricarboxylic acid showing double chain structures

Two new mixed-ligated metal phosphonates, M2（pbtcH）（phen）2（H2O）2 [M（Ⅱ）=Co （1）, Ni （2）] （pbtcH5 = 5-phosphonatophenyl-1,2,4-tricarboxylic acid, phen = 1,10-phenanthroline）, have been syn- thesized and characterized. Both show one-dimensional double chain structures, where the M（phen）（H2O） moieties are chelated and bridged by pbtcH4 through the carboxylate and phosphonate oxygen atoms. The chains are connected by hydrogen bonding interactions and π-π stacking, forming a three-dimensional supramolecular structure. The IR and magnetic properties of the two compounds are also investigated.

Engineering Heteronuclear Arrays from Ir^(Ⅲ)-Metalloligand and Co^(Ⅱ)Showing Coexistence of Slow Magnetization Relaxation and Photoluminescence

Three heteronuclear Ir^(Ⅲ)-Co^(Ⅱ)arrays,[Co(H_(2)O)6]_(2)[Ir(ppyCOO)(ppyCOOH)(bpy)]_(2)[Ir(ppyCOO)_(2)(bpy)]_(2)(NO_(3))2·10.5H_(2)O(2),[Co(H_(2)O)6]{Co-(H_(2)O)4[Ir(ppyCOO)_(2)(bpy)]_(2)}[Ir(ppyCOO)_(2)(bpy)]2·15H_(2)O(3)and{Co(H_(2)O)2[Ir(ppyCOO)_(2)(bpy)]_(2)}·2CH_(3)OH·3H_(2)O(4),have been synthe-sized by combining paramagnetic Co^(Ⅱ)ion with luminescent Ir^(Ⅲ)-metalloligand,[Ir(ppyCOOH)_(2)(bpy)][Ir(ppyCOO)_(2)(bpy)]·5H_(2)O(1),where ppyCOOH=3-(pyridin-2-yl)benzoic acid and bpy=2,2'-bipyridyl.Owing to the variable charged states of compound 1 at dif-ferent pH,compounds 2 and 3 are discrete ionic complexes containing hydrated Co^(2+)cations and deprotonated[Ir(ppyCOO)_(2)(bpy)]-anions as well as coexisting neutral[Ir(ppyCOO)(ppyCOOH)(bpy)](for 2)or Co(H_(2)O)_(4)[Ir(ppyCOO)_(2)(bpy)]_(2) trinuclear molecule(for 3).Whereas compound 4 consists of self-assembled two-dimensional coordination polymer with Co-metalloligand dative bonds.The hexa-coordinated Co^(Ⅱ)cores in all complexes display octahedral geometries with varying degrees of distortion.In a bias dc field,the ac susceptibilities for 2-4 reveal slow magnetic relaxation.Moreover,the solid-state phosphorescence is observed for compounds 2 and 3 due to weak supramolecular interaction between Co^(Ⅱ)ion and Ir-moiety but is severely quenched for 4,where the Co center is strongly connected to the metalloligand.To the best of our knowledge,this is the first report of Ir-Co systems showing both slow magnetization relaxation and photoluminescence.

Thermo-induced structural transformation with synergistic optical and magnetic changes in ytterbium and erbium complexes

Dinuclear ytterbium and erbium based bifunction complexes Ln_(2) L_(2)(depma_(2))Cl_(2)(1-Ln,Ln=Yb and Er,H_(2) L=N~1,N~3-bis(salicylideneimino)diethylenetriamine,depma_(2)=dimerized 9-diethyl-phosphonomethylanthracene)are reported.They undergo thermo-induced consecutive phase transitions,first the dissociation of depma_(2) ligand forming LnL(depma)Cl(2-Ln)and then the release of chloroethane forming LnL(epma)(3-Ln,epma=9-ethylphosphonomethylanthrancene).The structural transformations are accompanied with synergetic switch of the luminescence in visible and NIR regions and also magnetic dynamics.