Characteristics of Trivalent Lanthanides in Coordination Chemistry

Some basic characteristics of lanthanide-oxygen bonds in various trivalent lanthanide metal-organic complexes are quantitatively studied by the bond valence model. Some important relationships among the electronegativity, bond valence parameter, bond length and lanthanide coordination number in these complexes are generally found , which show that for each trivalent lanthanide cation all calculated parameters may well be correlated with its coordination number in their coordination complexes. Specifically,32 new data for the bond valence parameter are first calculated in this work.An approximate linear relationship between the Ln-O bond valence parameter and the coordination number of Ln^(3+) is obtained.The Ln-O bond length increases with the increase in the lanthanide coordination number.The difference of electronegative values decreases with the increase in the lanthanide coordination number.

Insights into layered-tunnel dynamic structural evolution based on local coordination chemistry regulation for high-energy-density and long-cycle-life sodium-ion oxide cathodes

The pursuit of high energy density while achieving long cycle life remains a challenge in developing transition metal(TM)oxide cathode materials for sodium-ion batteries(SIBs).Here,we present a concept of precisely manipulating structural evolution via local coordination chemistry regulation to design high-performance composite cathode materials.The controllable structural evolution process is realized by tuning magnesium content in Na0.6Mn1-xMgxO2,which is elucidated by a combination of experimental analysis and theoretical calculations.The substitution of Mg into Mn sites not only induces a unique structural evolu-tion from layered–tunnel structure to layered structure but also mitigates the Jahn–Teller distortion of Mn3+.Meanwhile,benefiting from the strong ionic inter-action between Mg2+and O2-,local environments around O2-coordinated with electrochemically inactive Mg2+are anchored in the TM layer,providing a pinning effect to stabilize crystal structure and smooth electrochemical profile.The layered–tunnel Na0.6Mn0.95Mg0.05O2 cathode material delivers 188.9 mAh g-1 of specific capacity,equivalent to 508.0 Wh kg-1 of energy density at 0.5C,and exhibits 71.3%of capacity retention after 1000 cycles at 5C as well as excellent compatibility with hard carbon anode.This work may provide new insights of manipulating structural evolution in composite cathode materials via local coordi-nation chemistry regulation and inspire more novel design of high-performance SIB cathode materials.

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.

Efficacious selective separation of U(Ⅵ) over Mo(Ⅵ) using novel 2,9-diamide-1,10-phenanthroline ligands: Liquid-liquid extraction and coordination chemistry

Uranium and molybdenum are important strategic elements. The production of ^(99)Mo and the hydrometallurgical process of uranium ore face difficult problems of separation of uranium and molybdenum.In this study, the four phenanthroline diamide ligands were synthesized, and extraction and stripping experiments were performed under different conditions to evaluate the potential application of these ligands for separation of U(Ⅵ) over Mo(Ⅵ). With the growth of alkyl chain, the solubility of ligands could be greatly improved, and the separation effect of U(Ⅵ) over Mo(Ⅵ) gradually increased. The SF_(U/Mo) were around 10,000 at 4 mol/L HNO3. Three stripping agents were tested with the stripping efficiency of Na_(2)CO_(3)(5%) > H_(2)O > HNO_(3)(0.01 mol/L). The stripping percentages of the three stripping agents were all close to unity, indicating that the ligands had the potential to be recycled. The chemical stoichiometry of U(Ⅵ) complexes with ligands was evaluated as 1:1 using electrospray ionization mass spectrometry,ultraviolet visible spectroscopy and single-crystal X-ray diffraction. The consistency between theoretical calculation and experimental results further explains the coordination mechanism.

Structure design and electrochemical properties of carbon-based single atom catalysts in energy catalysis:A review

Single atom catalysts(SACs) possessing regulated electronic structure, high atom utilization, and superior catalytic efficiency have been studied in almost all fields in recent years. Carbon-based supporting SACs are becoming popular materials because of their low cost, high electron conductivity, and controllable surface property. At the stage of catalysts preparation, the rational design of active sites is necessary for the substantial improvement of activity of catalysts. To date, the reported design strategies are mainly about synthesis mechanism and synthetic method. The level of understanding of design strategies of carbon-based single atom catalysts is requiring deep to be paved. The design strategies about manufacturing defects and coordination modulation of catalysts are presented. The design strategies are easy to carry out in the process of drawing up preparation routes. The components of carbon-based SACs can be divided into two parts: active site and carbon skeleton. In this review, the manufacture of defects and coordination modulation of two parts are introduced, respectively. The structure features and design strategies from the active sites and carbon skeletons to the overall catalysts are deeply discussed.Then, the structural design of different nano-carbon SACs is introduced systematically. The characterization of active site and carbon skeleton and the detailed mechanism of reaction process are summarized and analyzed. Next, the applications in the field of electrocatalysis for oxygen conversion and hydrogen conversion are illustrated. The relationships between the superior performance and the structure of active sites or carbon skeletons are discussed. Finally, the conclusion of this review and prospects on the abundant space for further promotion in broader fields are depicted. This review highlights the design and preparation thoughts from the parts to the whole. The detailed and systematic discussion will provide useful guidance for design of SACs for readers.

Cobalt coordination with pyridines in sulfurized polyacrylonitrile cathodes to form conductive pathways and catalytic M-N4S sites for accelerated Li-S kinetics

Sulfurized polyacrylonitrile(SPAN)represents a unique class of cathode material for lithium sulfur(Li-S)batteries as it eradicates the polysulfides shuttling issue in carbonate-based electrolyte.However,due to the essential chemical S-linking and organic nature of SPAN,the active mass percentage and rate capability are two bottleneck issues preventing its ultimate deployment outside of laboratories.In the current work,aiming to endow both the charge conductivity and catalytic activity to SPAN for maximizing the redox kinetics of S conversion,a freestanding nanofibrous SPAN cathode embedding conductive CNTs and atomically dispersed Co centers is fabricated via multivariate electrospinning.While the CNTs enable dramatically enhancing the fiber conductivity and generating mesoscopic porosity for facilitating charge and mass transportation,the cross-linking of SPAN by Co-N_(4) S motifs creates extra charge conduction pathways and further serves as the catalytic active sites for expediting redox S conversion.As a result,an extraordinary Li-SPAN performance is achieved with a high specific capacity up to 1856 mAh g^(-1)@0.2 C,a superb rate capability up to 10 C,and an ultra-long battery life up to 1500 cycles@1 C.Consequently,our study here provides insights into the adoption of coordination chemistry to maximize the sulfur utilization by ensuring a more complete redox conversion from SPAN to Li2 S,and vice versa.

Sodium-Coordinated Polymeric Phthalocyanines as Stable High-Capacity Organic Anodes for Sodium-Ion Batteries

Sodium-ion batteries(SIBs)have attracted considerable interest as an alternative to lithium-ion batteries owing to their similar electrochemical performance and superior long-term cycle stability.Organic materials are regarded as promising anode materials for constructing SIBs with high capacity and good retention.However,utilization of organic materials is rather limited by their low energy density and poor stability at high current densities.To overcome these limitations,we utilized a novel polymeric disodium phthalocyanines(pNaPc)as SIB anodes to provide stable coordination sites for Na ions as well as to enhance the stability at high current density.By varying the linker type during a one-pot cyclization and polymerization process,two pNaPc anodes with O-(O-pNaPc)and S-linkers(S-pNaPc)were prepared,and their structural and electrochemical properties were investigated.The O-pNaPc binds Na ions with a lower binding energy compared with S-pNaPc,which leads to more facile Na-ion coordination/dissociation when engaged as SIB anode.The use of O-pNaPc significantly improves the redox kinetics and cycle stability and allows the fabrication of a full cell against Na_(3)V_(2)(PO_(4))_(2)F_(3)/C cathode,which demonstrates its practical application with high energy density(288 Wh kg^(-1))and high power density(149 W kg^(-1)).

Expanded Porphyrin Exhibiting Off-Centered Out-of-Plane Coordination to Dysprosium

The complexation of high-spin lanthanides to porphyrinoids is a powerful strategy for the development of advanced molecular magnets.In this context,the use of expanded porphyrinoids remains elusive since their coordination chemistry is challenging to control.Herein,taking inspiration from on-surface chemistry,we explored the coordination of Dy^(3+)to a six-membered porphyrinoid,namely,the hemihexaphyrazine H3Hhp.Remarkably,we observed the selective formation of a mono-nuclear off-centered,out-of-plane H_(2)Hhp-Dy^(3+)complex when performing the complexation under reductive conditions.During this reaction,the oxidation state of the macrocycle did not change.Employing X-ray diffraction analysis,we found that the coordination number of Dy in this complex was 8.The macrocycle cocrystallized with decamethylcobaltocene(Cp_(2)^(*)Co)molecules,giving rise to a wellordered solid-state packing,governed byπ-πinteractions.As a result of this organization,a small magnetic coupling between the neighboring molecules was observed.All in all,this work provides key insights into the coordination of magnetically active metals with expanded porphyrinoids,thus motivating the development of advanced spintronic devices.

CuⅡ and CuⅠ Complexes of 1,1＇-（Pyridin-2-ylmethylene）-bis[3-（pyridin-2-yl）imidazo[1,5-a]pyridine]：in situ Generation of the Ligand via Acetic Acid-controlled Metal-ligand Reactions

Reaction of 3-（pyridin-2-yl）-imidazo[1,5-a]pyridine （HPIP）, CuCi2·2H20 and picolinaldehyde in the mixture of CHaCOOH and EtOH under solvothermal conditions gave complexes [LCuCI][CuECI3] （1） and [HLCuC1]E[CuCI2]2[CuCI3].2H20 （2） （L = 1,1＇-（pyridin-2- ylmethylene）bis[3-（pyridin-2-yl）imidazo[1,5-a]pyridine]） simultaneously. The ligand L was generated via in situ metal-ligand reaction between HPIP and picolinaldehyde. When CuCI2·2H20 was replaced by CuC1, the 2：1：1（HPIP：picolinaldehyde：CuCI） reaction afforded complex [CuaL2CI2][CuCI2]·2H20 （3） and the analogous 2：1：3 reaction generated compound [CuaL2][CuCI2]3 （4）. Complexes 1 and 2 are Cun/CuI mixed-valence compounds. Complexes 1-4 display four various structures. It is found that the formation of the L ligand is controlled by CH3COOH. This work reveals that the structures of complexes 1-4 could be rationally tuned via the inclusion of CH3COOH in the reaction systems, the proper selection of different starting materials and the dexterous adjustment of the ratio of the starting materials.

Recent advances in amino acid-metal coordinated nanomaterials for biomedical applications

Metal and amino acid(AA),as two kinds of entities,have been widely involved in biomaterials and nanomedicines.Recently,the marriage of them has developed new nanoformulations,amino acid-metal coordinated nanomaterials(AMCNs),which show great biomedical application potential in cancer therapy,antibacterial applications,biomedical imaging,etc.With the respective characteristics of metal and AA with rich biological and chemical properties,AMCNs can not only act as drug carriers with specific tumor targeting ability,but also realize synergistic therapy and imaging-guided therapy.Although the design and synthesis of amino acid-metal coordinated nanomaterials have been in-depth investigated,there are few systematic reviews on their biomedical application.In this review,we give a comprehensive summary of recent progresses in the design,fabrication,and biomedical applications of AMCNs.We also propose the future outlooks and challenges in aforementioned field.We expect that this review would contribute some inspiration for future research and development for amino acid metal coordinated nanomaterials.

Synthesis and applications of lanthanoid complexes of pentadentate and hexadentate N_(5) and N_(6) macrocycles:A review

In this paper,the lanthanoid complexes of N_(5) and N_(6) macrocycle ligands,without pendant arms or additional heteroatoms,are surveyed.This review covers the period from 2015 to the current date,since in 2014 Schiff base macrocyclic ligands incorporating the pyridine moiety,and their complexes,were revised,and in 2015 the chemistry of pentaaza macrocycle ligands with rare earth metals was also summarized.Porphyrin and phthalocyanine ligands are not included in this review,which primarily focuses on complexes with Schiff bases and amines without pendant arms or any additional donor other than nitrogen.The synthetic methods,structural characterization,based on single X-ray crystal data,and properties of the lanthanoid complexes,with special attention to magneto-structural correlations,are presented herein.

Halogen-bond induced unusual polyhalogen anions formation in hydrogen-bonded frameworks to secure iodine sequestration

Safe confinement of fission iodine isotopes for long-term radioactive waste disposal remains a formidable challenge,as conventional sorbents provide inherently weak iodine-host interactions.We report here a novel halogen bond(X-bond)directed strategy to sequester volatile iodine in hydrogen-bonded(H-bonded)frameworks with unprecedented stability.Charge-assisted Hbonded frameworks bearing open halide sites are developed,showing distinctive iodine encapsulation behaviors without compromising the crystallinity.Direct crystallographic evidence indicates the formation of X-bonds,i.e.,I–I···Cl^(−) and I–I···Br^(−),within the confined pore channels.Unusual polyhalogen anions,i.e.,[I_(2)Cl_(2)]^(2−)and[I_(2)Br_(2)]^(2−),sustained in H-bonded frameworks are identified for the first time.The X-bond reinforced host-guest interaction affords robust iodine trapping without leaking out even at elevated temperatures up to 180℃.By integrating the halogen-bond chemistry with H-bonded frameworks,this study offers fresh concepts for developing effective host reservoirs to secure fission iodine isotopes from spent fuel reprocessing off-gases.

Coordination engineering of Cu-Zn-Sn-S aqueous precursor for efficient kesterite solar cells

Aqueous precursors provide an alluring approach for low-cost and environmentally friendly production of earth-abundant Cu2ZnSn(S,Se)4(CZTSSe)solar cells.The key is to find an appropriate molecular agent to prepare a stable solution and optimize the coordination structure to facilitate the subsequent crystallization process.Herein,we introduce thioglycolic acid(TGA),which possesses strong coordination(SH)and hydrophilic(COOH)groups,as the agent and use deprotonation to regulate the coordination competition within the aqueous solution.Ultimately,metal cations are adequately coordinated with thiolate anions,and carboxylate anions are released to become hydrated to form an ultrastable aqueous solution.These factors have contributed to achieving CZTSSe solar cells with an efficiency as high as 12.3%(a certified efficiency of 12.0%)and providing an extremely wide time window for precursor storage and usage.This work represents significant progress in the non-toxic solution fabrication of CZTSSe solar cells and holds great potential for the development of CZTSSe and other metal sulfide solar cells.

UranyI Phosphonates with Multiple UranyI Coordination Geometries and Low Temperature Phase Transition

Main observation and conclusion Two new uranium(VI)phosphonate compounds,namely K_(8)[N(C_(2)H_(5))_(4)]_(2)(UO_(2))_(17)(H_(2)O)_(4)[CH_(2)(PO_(3))_(2)]_(8)[CH_(2)(PO_(3))(PO_(3)H)]_(4)·16(H_(2)O)(1)and[N(C_(2)H_(5))_(4)]_(4)(H_(3)O)_(2)(UO_(2))_(10)[CH_(2)(PO_(3))_(2)]_(5)[CH_(2)(PO_(3))(PO_(3)H)]_(2)·10H_(2)O(2),have been synthesized under mild hydro/solvothermal condition.The structural analysis of the two compounds reveals that they both contain all three typical coordination geometries of the U(VI)ions,including UO;tetragonal,UO,pentagonal,and UOg hexagonal bipyramids.Moreover,compound 1 displays a tempera-ture-induced single crystal to single crystal phase transformation as confirmed by the Single-crystal X-ray diffraction data collected at different temperatures.Temperature-dependent fluorescence spectra presented herein illustrate the perturbation of the electronic structure of uranyl centers.

Exploring the Nanomechanical Properties of a Coordination-bond Based Supramolecular Polymer

Due to their dynamic nature and strength tunability,metallo-supramolecular polymers have been introduced into various materials.The mechanical strength of the metallo-supramolecular polymers in the system directly influences the mechanical properties(e.g.,the toughness)of the materials.Therefore,it is necessary to explore the mechanical behavior of the metallo-supramolecular polymers.Herein,we present a single-molecule method to systematically explore the chain structure and mechanical properties of metallo-supramolecular polymer by using a loop protected architecture.Notably,we found that the mechanical stability of the individual chain,which is determined by the strength of terpyridine-Fe^(2+) -terpyridine(tpy-Fe^(2+)-tpy)bonds,was about 0.6–1.0 nN,depending on the pulling speed.This value is around three times higher than those measured using old methods.In addition,the unique loop protected structure further reduces the interference of non-specific polymer-AFM tip(or polymer-substrate)interactions on the quantification of the actual strength and kinetic parameter of noncovalent interactions in supramolecular polymers.Furthermore,the single chain flexibility of the metallo-supramolecular polymer was investigated and found to be comparable to the corresponding covalent analogues.Our findings provide a new way to explore the force response of supramolecular polymers composed of metal-ligand interactions and will be useful for the design of metallo-supramolecular polymer-based functional materials with tailored mechanical properties.

A Tetravalent Plutonium Organic Framework Containing[Pu_(2)O_(16)]Dimers as Secondary Building Units:Synthesis,Structure,and Radiation Stability

The second example of tetravalent plutonium carboxyl-based organic framework,^(242)Pu(OH)[PO[(C_(6)H_(4))COO]_(3)]·H_(2)O,termed as PuTPO(TPO=tris(4-carboxylphenyl)-phosphineoxide),was reported in this work.A series of characterizations of PuTPO,such as X-ray crystallography and solid-state UV-Vis-NIR spectroscopy,were carried out to expatiate its structure and physicochemical properties.PuTPO is constructed by dimers of the plutonium-oxygen subunit of[Pu_(2)O_(16)].Characteristic peaks located at approximately 1100 nm can be considered to be the fingerprint peaks of tetravalent plutonium.While PuTPO can maintain high crystallinity within several months after synthesis,it exhibits a radiation-induced swelling effect probed by the expansion of cell parameter of b axis after self-irradiation fromα-decay of ^(242)Pu.This result enriches the inventory of tetravalent plutonium compounds and provides an insight into the irradiation resistance of metal-organic frameworks.

Liquid-phase epitaxy of metal organic framework thin films

Metal-organic framework(MOF) thin films are multilayer materials ranging from nanometers to micrometers in thickness,physically or chemically adhesive to a(functionalized) substrate and,in an ideal case,exhibiting low roughness and high homogeneity.Various innovative approaches have been developed for MOF thin film fabrication.Among these advanced materials,surface-attached metal-organic frameworks(SURMOFs) are an important class of MOF films.SURMOFs,fabricated in a step-by-step liquid phase epitaxial(LPE) fashion by alternating deposition of metal and organic linker precursors on a functionalized substrate,for example,thiolate-based self-assembled monolayers(SAMs),have already exhibited their utility in both research and potential applications.SURMOFs combine surface science and the chemistry of MOFs,possessing the following unique advantages that cannot be accessed through other methods:(i) precisely controlling thickness,roughness and homogeneity as well as growth orientation,(ii) studying of MOF growth mechanism,(iii) modifying/tailoring MOFs' structures during the SURMOF growth and thus creating customizable properties,and(iv) existing in the form of thin film/membrane for direct applications,for example,as sensors.This review discusses the oriented and crystalline SURMOFs fabricated by LPE approach,covering their preparation,growth mechanism,and characterization methodology as well as applications based upon the most newly updated knowledge.

Minimizing Purifi cation-Induced Defects in Single-Walled Carbon Nanotubes Gives Films with Improved Conductivity

A method for the non-destructive purification of single-walled carbon nanotubes(SWNTs)using classical coordination chemistry to remove the metal catalyst has been developed.In preliminary tests,the conductivity of films based on the resulting SWNTs was markedly better than that of films prepared from SWNTs purified by treatment with oxidizing acid solutions.The transparent and conducting SWNT films have potential applications in optoelectronic devices.

Combining metal-organic frameworks(MOFs)and covalentorganic frameworks(COFs):Emerging opportunities for new materials and applications

In the past decades,metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)basically enjoy the coordination chemistry and covalent chemistry,respectively,and such uniqueness has become the major obstacle hampering their further scope diversity and application multi-functionalization.Inspired from the principle of organic retrosynthesis,combining coordination bond and covalent bond together offers additional opportunities for constructing novel MOFs,COFs and MOF@COF hybrids as well as confer on them superior performances in versatile application fields.In this review,we firstly classify and summarize the recently reported synthesis strategies based on the integration of metal-ligand coordination and dynamic covalent bonds.Then,the application performances of as-constructed MOFs,COFs as well as MOF@COF hybrids are discussed and highlighted in the fields of adsorption,separation,catalysis,biosensing,energy storage and so on.Last,our personal insights of the remaining challenges and further prospects are also provided,in order to trigger much more inspirations and endeavors for this hot research field.

siRNA-functionalized lanthanide nanoparticle enables efficient endosomal escape and cancer treatment

Attaching DNA/RNA to nanomaterials is the basis for nucleic acid-based assembly and drug delivery.Herein,we report that small interfering RNA(siRNA)effectively coordinates with ligand-free lanthanide nanoparticles(NaGdF4 NPs),and forms siRNA/NaGdF4 spherical nucleic acids(SNA).The coordination is primarily attributed to the interaction between Gd and phosphate backbone of the siRNA.Surprisingly,an efficient encapsulation and rapid endosomal escape of siRNA from the endosome/lysosome were achieved,due to its flexible ability to bound to phospholipid head of endosomal membrane,thereby disrupting the membrane structure.Resorting to the dual properties of NaGdF4 NPs,siRNA loading,and endosomal escape,siRNA targeting programmed cell death-ligand 1(siPD-L1)/NaGdF4 SNA triggers significant gene silencing in vitro and in vivo,and effectively represses the tumor growth in both CT26 tumor model and 4T1 orthotopic murine model.