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The β-diketone scaffold is a commonly used synthetic intermediate, and is a functional group found in natural products such as curcuminoids. This core structure can also act as a chelating ligand for a variety of metals. In order to assess the potential of this scaffold for medicinal inorganic chemistry, seven different κ(2)-O,O’-chelating ligands were used to construct Ru(II) complexes with polypyridyl co-ligands, and their biological activity was evaluated. The complexes demonstrated promising structure-dependent cytotoxicity. Three complexes maintained high activity in a tumor spheroid model, and all complexes demonstrated low in vivo toxicity in a zebrafish model. From this series, the best compound exhibited a ~ 30-fold window between cytotoxicity in a 3-D tumor spheroid model and potential in vivo toxicity. These results suggest that κ(2)-O,O’-ligands can be incorporated into Ru(II)-polypyridyl complexes to create favorable candidates for future drug development.

We prepared four new complexes, 4a,b and 5a,b, from polyimido sulfur-centered ligands with FeII and CoII amides. Their molecular structures were elucidated by single-crystal X-ray diffraction. Cobalt magnetic investigations and multiconfigurational calculations provided insight into magneto-structural correlations between the acute N,N' chelating bite angle and P-side arm donation. The deviation from an ideal trigonal planar geometry and the magnetic performance correlated in an unprecedented manor. Mononuclear cobalt species 4b and 5b showed slow magnetic relaxation under a small applied dc field with energy barriers of up to 33.0 and 21.9 cm-1, respectively. Although they possess some of the largest zero-field splitting parameters among three-coordinate cobalt single-ion magnets, both theory and experiment suggest that the high rhombicity (E/D) hampers large effective energy barriers to spin reversal at zero field from being obtained.

A comparative investigation of two structurally related potentially nonadentate chelating ligands, H4neunpa-NH2 and H4noneunpa, has been undertaken to examine the influence of bifunctionalization o...

Rechargeable zinc-ion batteries (RZIBs) are mostly powered by aqueous electrolytes. However, uncontrolled water interactions often confer a small voltage window and poor battery capacity retention. Here, we explore replacing water with ethylene glycol as the primary solvent in zinc electrolyte formulations. The assembled batteries reveal suppressed electrolyte-induced parasitic reactions, leading to (1) expanded voltage stability windows up to 2.2 V, (2) prolonged zinc stripping/plating stability up to 2.4 times longer compared to the water-based counterparts, and (3) doubled cathode capacity retentions as observed in full-cell Zn-FeVO4 RZIBs. Using a combination of synchrotron EXAFS and FTIR, we investigate the molecular level salt-solvent interactions and explain how the chelation ability of EG ligands reduces parasitic reactions to enable the enhanced electrochemical performances. The structural insights should provide guidelines on the selection of salt, concentration, and chelating solvents for robust multivalent-ion battery systems. National Research Foundation (NRF) Accepted version This work was funded by the National Research Foundation of Singapore Investigatorship Award Number NRFI2017-08

Examples of chelating ligands that incorporate P-O donors are seldom encountered. Herein, a series of novel bridging diphosphate ligand supported bimetallic Zr(iv), V(iii) and Ni(ii) complexes have been derived from reactions of the oxyphosphorane (C6Cl4O2)P(OEt)3 with the corresponding metal halides. The mechanism is probed and shown to involve elimination of ethyl halide, and ring opening affording the chelating phosphate-catecholate ligands.

While lanthanides and actinides are essential to many clean energy technologies, they are at high risk for supply chain disruption. As such, the development of recycling and recovery techniques for lanthanides and actinides is essential to avoid future shortages. Conventional reversed-phase chromatography cannot readily discriminate between the metals, making column modifications, such as adsorption of ion-pair agents, necessary to achieve element separation. In this work, we demonstrate that a siderophore-inspired synthetic derivative, 3,4,3-LI(1,2-HOPO), can be used as an in situ chelating agent, promoting lanthanide and trivalent actinide separation in less than 15 min without column modification. By employing alternative chelating ligands, f-element separations are therefore achievable in chromatographic systems used in analytical laboratories around the world, creating new opportunities for the separation and recovery of these critical materials.

Chelating phosphines have long been a mainstay as efficient directing ligands in transition‐metal catalysis. Low‐valent derivatives, namely chelating phosphinidenes, are to date unknown, and could lead to chelating complexes containing more than one metal centre due to the intrisic capacity of phosphinidenes to bind two metal fragments at one P‐centre. Here we describe the synthesis of the first such chelating bis‐phosphinidene ligand, XantP2 (2), generated by the reduction of a diphosphino xanthene derivative, Xant(PH2)2 (1) with iPrNHC (iPrNHC=[:C{N(iPr)C(H)}2]). Initial studies have shown that this novel chelating ligand can act as a bidentate ligand towards element dihalides (i.e. FeCl2, ZnI2, GeCl2, SnBr2), forming cationic complexes with the tetryl elements. In contrast, XantP2 demonstrates an ability to bind multiple metal centres in the reaction with CuCl, leading to a cationic Cu3P3 ring complex, with Cu centres bridged by phosphinidene arms. Density Functional Theory calculations show that 2 indeed holds 4 lone pairs of electrons, shedding further light on the coordination capacity for this novel ligand class through observation of directionality and hybridisation of these electron pairs., It's a P‐P‐Party! A facile synthetic route to a new form of chelating phosphorous ligand, namely the chelating bis‐phosphinidene XantP2, has been developed, allowing for the gram‐scale synthesis of this novel ligand scaffold. Computational investigations corroborate that each P‐centre holds two lone pairs of electrons, allowing for the binding of multiple metal centres. Initial efforts towards the coordination chemistry of XantP2 are reported.

The mobility of several radionuclides in a soil sample from a potential site in Egypt is examined. The retention of 152,154Eu (as homologs of 241Am), 60Co, 137Cs, and 99Mo in the presence of chelating ligands in the soil sample and without them is studied. Four chelating agents, namely, ethylenediaminetetraacetic acid (EDTA), citric and oxalic acids (as the major degradation products of EDTA), and humic acid are chosen for this purpose. The radionuclide retention on the soil without chelating ligands decreases in the order Co(II) > Eu(III) > Cs(I) > Mo(VI), with Kd equal to 11.38 mL/g for 99Mo and 1088 mL/g for 152,154Eu. The chelating ligands had little influence on the sorption of 60Co and 137Cs, but significantly decreased the retention of 152,154Eu owing to complexation. The soil sample on the potential nuclear site can act as a material for trapping the released radionuclides.

A disilane that contains two diphenylphosphino moieties, (Ph2PCH2)Ph2Si-SiPh2(CH2PPh), was readily synthesized from the reaction of ClPh2Si-SiPh2Cl with (tmeda)Li(CH2PPh2). Treatment of the thus-obtained disilane with the palladium(0) precursor [Pd(CNtBu)2]3 led to the exclusive formation of a trinuclear palladium cluster in which three palladium atoms are arranged in a triangular fashion. Single-crystal X-ray diffraction analysis of the obtained triangular cluster revealed that novel silylphosphido chelating ligands were formed via a skeletal rearrangement of the ligand framework.

The synthesis and characterization of air-stable heterobimetallic Os–Ag hydrides are described. All of the new heterobimetallic Os–Ag hydrides are neutral, and the in situ generated and presynthesized cis-[Os](H)–CC–R units in these frameworks act as organometallic bidentate chelating ligands coordinating with the AgPPh3 cation, which makes these complexes more stable. Our results provide a new synthetic route for the construction of stable heterobimetallic complexes.

In the current study, two new coordination complexes with the chemical formulae of [Co(cbba)(bimb)](H2O) (1, H2cbba = 3-((3-carboxybenzyl)oxy)benzoic acid, bimb = 6,6′-bis(1H-benzo[d]imidazol-2-yl)...

A series of chiral bis-N-heterocyclic carbene ligands H2[(S)-1a–d]X2 (X = Br, I) on a spiro scaffold and their palladium complexes (S)-2a–d and (S)-3a,b were prepared and applied in the enantiosele...

Signal Amplification By Reversible Exchange (SABRE) is a particularly simple hyperpolarisation approach. However, compared to other hyperpolarisation methods, SABRE is more limited in substrate scope. Therefore, it is critical to understand and overcome the factors limiting generalization. Past developments in SABRE catalyst optimization have emphasized large enhancements in the canonical SABRE substrate: pyridine and structurally closely related motifs. However, the pyridine-optimized catalysts are not efficient at hyperpolarising more sterically demanding substrates, including 2-substituted pyridine derivatives. Here we report that modifications of the catalyst ligand sphere, using a chelating ligand in particular, can increase the volume fraction available for substrate coordination to the iridium catalyst, thus permitting significant signal enhancements on otherwise sterically hindered substrates. The system yields (1)H enhancements on the order of 100-fold over 8.5 T thermal measurements for 2-substituted pyridine derivatives, and smaller, yet significant (1)H enhancement for provitamin B(6) and caffeine. For the 2-substituted pyridine derivatives we further show (15)N enhancements on the order of 1000-fold and (19)F enhancements of 30-fold over 8.5 T thermal polarisations.

We report the syntheses of two new organotin sulfide clusters with heteroaromatic substituents. A phenanthroline-functionalized tin sulfide cluster [(RPhenSn)4S6] (1; RPhen = CMe2CH2C(Me)N-NC(H)C12H7N2) and a bipyridyl-terminated cluster [(R4-bipySn)4S6] (2; R4-bipy = CMe2CH2C(Me)N-NC(H)-4-C10H7N2) were obtained from reactions of the hydrazone-functionalized organotin sulfide cluster [(RNSn)4S6] (RN = CMe2CH2C(Me)N-NH2) with 1,10-phenanthroline-5-carboxaldehyde or 2,2'-bipyridine-4-carbaldehyde. 1 and 2 were tested towards their capability of trapping metal ions by means of the terminal chelating ligands. The reaction of 2 with ZnCl2 afforded the cluster compound [(R4-bipyZnCl2Sn)4S6] (5), in which four ZnCl2 units are coordinated by the heteroaromatic organic groups. We discuss the structures and demonstrate the effect of ZnCl2 trapping on optical absorption and luminescence properties.

Since the remarkable work by Werner, the design and use of chelating ligands have played an essential part in coordination chemistry. While ligands such as 2,4-pentanedione (acac) and 1,5-diazapentadienyl (NacNac) have been established in the literature for over a century and their rich coordination chemistry is well known, 1,3,5-triazapentadiene ligands remain the significantly less explored members of this family. Also known as imidoyl amidine (ImAm), the coordination chemistry of this ligand framework has recently attracted a great deal of attention due to its multiple binding sites, ability to be incorporated into organic and inorganic materials, and diverse applicability (catalysis, biomolecular probes, materials science, etc.) making them a class of chelates like no other. The scope of this review is to provide a critical overview of the research progress on the chemistry of ImAm as well as complexation with different metal ions. General synthetic routes and new insights for the preparation of ImAm are discussed along with their use as starting materials or intermediates in organic and coordination chemistry in the development of materials that have found use in fields ranging from magnetic, conducting and luminescent materials to catalysis and biomedical applications. Concluding remarks including the limitations and perspectives of ImAm are discussed.

The structural features of four mononuclear octahedral d2-Re(V) monooxo complexes [ReO(Ltri)(Lbi)] and [ReO(Ltetra)(Lmono) with tridentate (O, O, O) and tetradentate (O, O, O, O) chelating ligands are discussed. It is shown that the Re–O(Ltri)trans bonds are elongated, whereas the Re–O(Ltetra)trans bonds are shortened as compared to the Re–O(L)cis bonds.

Mn(II) has several favorable physicochemical characteristics and a good toxicity profile, which makes it a viable alternative to the Gd(III)-based MRI contrast agents currently used in clinics. Although many studies have been undertaken in the last 10 years, this is a field of investigation still in rapid and continuous development. This review aims to critically discuss the chemical and magnetic properties of Mn(II) compounds relevant as MRI probes, both small complexes and nanosystems containing a large number of metal centers, the possible approaches for optimizing their efficiency by understanding the role of various molecular parameters that control the relaxation processes, and the most important issues related to stability and kinetic inertness.

Various functional secondary and tertiary phosphines, or their derivatives, containing stationary chiral phosphorus and flexible chiral axis were prepared, which could be further modified to afford diversely chelating ligands. The flexible axial chirality was fixed by stereogenic phosphorus via a cyclic linkage of chemical bonds or coordination with a metallic ion.

Six new green to yellow-emitting heteroleptic bis-cyclometalated iridium(III) complexes of the type Ir(C⁁N)2(L⁁X) (C⁁N = cyclometalating ligand, L⁁X = monoanionic chelating ancillary ligand) bearin...

Organic light-emitting diodes (OLEDs) are well known in display, signage, and lighting potential applications. However, the development of organic semiconductors started 100 years back by Pochettino in 1906 with the discovery of the photoelectric effect in anthracene crystals. Over the recent past, a lot of efforts have been spent to increase device efficiency and lifetime, which permits organic electroluminescence in the display and lighting market. Degradation of materials is the major obstacle for the development of highly efficient and economically feasible and durable organic light-emitting devices for commercial applications. In this progressive review article, we have consolidated the recent advances in the elucidation of materials degradation due to possible crystal defects and π-conjugated structures having high carrier mobility in organoboron compounds, which make them to be appropriate in optoelectronics including OLEDs. Various chelating ligands and boron moieties have been researched and explored to construct stable electronic structural molecules in four-coordinated boron compounds, which play significant roles on the photophysical and electronic properties. In this review article, we provided the overview of the materials degradation, construction, and durability of organoboron compounds with enough prominence photophysical data.

Schrock alkylidenes are highly versatile, very active olefin metathesis catalysts, but their pronounced sensitivity to air still hinders their applications. Converting them into more robust but inactive 18-electron adducts was suggested previously to facilitate their handling. Generating the active species from the inactive adducts, however, required a high-temperature Lewis acid treatment and resulted in an insoluble by-product, limiting the practicality of the methodology. Herein, we introduce an approach to circumvent the inconvenient, costly, and environmentally taxing activation process. We show that 18-electron adducts of W- and Mo-based Schrock catalysts with finite stability constants (typically K = 200–15,000 M−1) can readily be prepared and isolated in excellent yields. The adducts display enhanced air-stability in the solid state, and in solution they dissociate spontaneously, hence liberating the active alkylidenes without chemical assistance. Air-sensitive molybdenum olefin metathesis catalysts are known to form stable but inactive adducts with appropriate chelating ligands, but regenerating the active catalyst requires the use of Lewis acids and vigorous conditions. Here, tuning the electron donor capacity of the ligands leads to air-stable solid adducts of tungsten and molybdenum alkylidenes that spontaneously release the active catalysts in solution.

Incorporating nanoparticles into devices for a wide range of applications often requires the formation of thick films, which is particularly necessary for improving magnetic power storage, microwave properties, and sensor performance. One approach to assembling nanoparticles into films is the use of electrophoretic deposition (EPD). This work seeks to develop methods to increase film thickness and stability in EPD by increasing film-substrate interactions via functionalizing conductive substrates with various chelating agents. Here, we deposited iron oxide nanoparticles onto conductive substrates functionalized with three chelating agents with different functional moieties and differing chelating strengths. We show that increasing chelating strength can increase film-substrate interactions, resulting in thicker films when compared to traditional EPD. Results will also be presented on how the chelating strength relates to film formation as a function of deposition conditions. Yield for EPD is influenced by deposition conditions including applied electric field, particle concentration, and deposition time. This work shows that the functionalization of substrates with chelating agents that coordinate strongly with nanoparticles (phosphonic acid and dopamine) overcome parameters that traditionally hinder the deposition of thicker and more stable films, such as applied electric field and high particle concentration. We show that functionalizing substrates with chelating agents is a promising method to fabricate thick, stable films of nanoparticles deposited via EPD over a larger processing space by increasing film-substrate interactions.

The reaction of [(arene)MCl2]2 with ligands 4-hydroxy-benzhydrazide (L1) and 3-methoxy-benzhydrazide (L2) leads to formation of cationic complexes 1-6 having the general formula [(arene)M(L)Cl]+ {arene = p-cymene, M = Ru; arene = Cp*; M = Rh/Ir; L = L1 and L2}. The reaction of [CpRu(PPh3)2Cl] with L1 and L2 yielded cationic complexes that have been formulated as [CpRu(L)PPh3]Y {Y = Cl (7), Y = PF6 (8)}. The molecular structures of 1, 2 and 4 revealed that these complexes adopt typical three-legged “piano stool” geometry. The arene ring occupies the apex of the stool, terminal chloride and N,O-bidentate ligands are coordinated to the metal center at the base of the stool. The antibacterial activity of the ligands and complexes was evaluated on Gram-positive S. aureus, B. thuringiensis and Gram-negative E. coli, P. aeruginosa strains; some complexes exhibit moderate antibacterial activity towards gram-positive bacteria. The antioxidant studies of these complexes have been carried out, and the results showed that these complexes have strong DPPH-scavenging properties.

International audience; Long overlooked, chelating ligands have garnered recently increasing interest in gold chemistry. They enforce bending at gold(I) and thereby, noticeably modify its electronic properties. This review focuses on -complexes with alkenes and alkynes side-on coordinated to gold(I), as well as gold(I) carbene complexes. The influence of the chelating ligand on the structure, bonding and reactivity of these species is thoroughly discussed.

Reactions of C10H7-1-N(PPh2)2 (1) and C10H7-1-N(P(Se)Ph2)2 (2) ligands with mercury(II)iodide in equimolar ratio gave cis-[HgI2{1-��2P,P}] (3) and cis-[HgI2{2-��2Se,Se}] (4). Also, refluxing of monooxidized thioyl and selenoyl bis(phosphino)amine ligands C10H7-1-N(P(E)Ph2)(PPh2) (E = S (5), Se (6)) with [Ru(CO)3Cl2]2 dimer afforded cis-[Ru(CO)2Cl2{5-��2P,S}] (7) and cis-[Ru(CO)2Cl2{6-��2P,Se}] (8). Complexes 3, 4, 7 and 8 were identified and characterized by multinuclear NMR (1H, 13C, 31P and 77Se NMR) and IR spectroscopy. The molecular structure of 5 was determined by single X-ray crystallography. 5 is the first structurally characterized example of this kind of ��2P,S -bidentate ligand. The novel ruthenium(II) complexes 7 and 8 show high catalytic activity in the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source.

Background 64Cu is one of the few radioisotopes that can be used for both imaging and therapy, enabling theranostics with identical chemical composition. Development of stable chelators is essential to harness the potential of this isotope, challenged by the presence of endogenous copper chelators. Pyridyl type chelators show good coordination ability with copper, prompting the present study of a series of chelates DOTA-xPy (x = 1–4) that sequentially substitute carboxyl moieties with pyridyl moieties on a DOTA backbone. Results We found that the presence of pyridyl groups significantly increases 64Cu labeling conversion yield, with DOTA-2Py, −3Py and -4Py quantitatively complexing 64Cu at room temperature within 5 min (1 × 10− 4 M). [64Cu]Cu-DOTA-xPy (x = 2–4) exhibited good stability in human serum up to 24 h. When challenged with 1000 eq. of NOTA, no transmetallation was observed for all three 64Cu complexes. DOTA-xPy (x = 1–3) were conjugated to a cyclized α-melanocyte-stimulating hormone (αMSH) peptide by using one of the pendant carboxyl groups as a bifunctional handle. [64Cu]Cu-DOTA-xPy-αMSH retained good serum stability (> 96% in 24 h) and showed high binding affinity (Ki = 2.1–3.7 nM) towards the melanocortin 1 receptor. Conclusion DOTA-xPy (x = 1–3) are promising chelators for 64Cu. Further in vivo evaluation is necessary to assess the full potential of these chelators as a tool to enable further theranostic radiopharmaceutical development. Supplementary Information The online version contains supplementary material available at 10.1186/s41181-020-00119-4.

Fossilization yields stable polymers diagnostic of tissue type, biomineralization, and the place of animals in the tree of life., Proteins, lipids, and sugars establish animal form and function. However, the preservation of biological signals in fossil organic matter is poorly understood. Here, we used high-resolution in situ Raman microspectroscopy to analyze the molecular compositions of 113 Phanerozoic metazoan fossils and sediments. Proteins, lipids, and sugars converge in composition during fossilization through lipoxidation and glycoxidation to form endogenous N-, O-, and S-heterocyclic polymers. Nonetheless, multivariate spectral analysis reveals molecular heterogeneities: The relative abundance of glycoxidation and lipoxidation products distinguishes different tissue types. Preserved chelating ligands are diagnostic of different modes of biomineralization. Amino acid–specific fossilization products retain phylogenetic information and capture higher-rank metazoan relationships. Molecular signals survive in deep time and provide a powerful tool for reconstructing the evolutionary history of animals.

The use of multidentate chelating ligands enriches the geometric diversity of coordinated gold clusters, offering much knowledge to benefit the understanding of their unique electronic structures a...

A series of gold(I) N-heterocyclic carbene complexes containing monoanionic acylchalcogenourea (chalcogen = S, Se) ligands was prepared and characterised by various spectroscopic methods and X-ray diffraction. The compounds were conveniently accessible in good yields through a one-pot reaction involving [AuCl(tht)] (tht = tetrahydrothiophene), the imidazolium salt and the acylchalcogenourea in the presence of excess base. The X-ray diffraction experiments showed that in these complexes, the normally chelating ligands adopt the rare κS/Se-coordination mode in which only the chalcogen is bound to gold.

Pyrazoles were reacted with acylbromoacetylenes in solid Al2O3 at room temperature to afford 2,2-di(pyrazol-1-yl)enones in 22–69% yield. The reaction proceeds via isolable intermediates, (Z)-2-bromo-2-(pyrazol-1-yl)enones. This unexpected 2:1 coupling is in contrast to similar reactions of pyrroles, furans and thiophenes, which give the corresponding acylethynyl derivatives. This reaction opens a one-pot route to inaccessible gem-dipyrazolylenones, which have potential applications as bidentate chelating ligands and building blocks for drug design.

Binuclear Ni(II) complexes of 4-diethylaminosalicylaldehyde-4(N)-substituted thiosemicarbazones bridged by 1,3-bis(diphenylphosphino)propane have been synthesized and characterized. A spectroscopic evaluation of their binding ability with DNA and protein was carried out, the results of which implied a better affinity for the complexes. The free radical scavenging activity of the complexes was found to be greater than those observed for the ligands, the metal precursor and standard Vitamin C.

A series of {2Fe3S} complexes bearing phosphino thioether chelating ligand were synthesized on the basis of Fe2(Me2pdt)(1,2-Cy2PC6H4SMe)(CO)4 (Me2pdt = Me2C(CH2S−)2, 1). The disubstituted Fe(I)Fe(I) compound 1 exhibits a reversible one-electron redox even for [Fe(I)Fe(II)]+/0 couple. Based on the oxidation of 1 to [1]+, the tri-substituted [Fe(I)Fe(II)]+ cationic complex [Fe2(Me2pdt)(1,2-Cy2PC6H4SMe)(PPh3)(CO)3]+ ([2]+) was synthesized. Reduction of [2]+ provided the neutral tri-substituted Fe(I)Fe(I) compound 2. The substitution of the CO in 1 ligand by PPh3 results in an anodic shift of the FeIIFeI/FeIFeI couple of 470 mV. Most importantly, this substitution also leads to the Fe-Fe bonds in 1 and 2 with large Lewis basicity difference, i.e. ΔpKaMeCN ∼ 10.

Over the past decades, the need for rare earth elements (REEs) has increased substantially, mostly because these elements are used as valuable additives in advanced technologies. However, the difference in ionic radius between neighboring REEs is small, which renders an efficient sized-based separation extremely challenging. Among different types of extraction methods, solid-phase extraction (SPE) is a promising candidate, featuring high enrichment factor, rapid adsorption kinetics, reduced solvent consumption and minimized waste generation. The great challenge remains yet to develop highly efficient and selective adsorbents for this process. In this regard, ordered mesoporous materials (OMMs) possess high specific surface area, tunable pore size, large pore volume, as well as stable and interconnected frameworks with active pore surfaces for functionalization. Such features meet the requirements for enhanced adsorbents, not only providing huge reactional interface and large surface capable of accommodating guest species, but also enabling the possibility of ion-specific binding for enrichment and separation purposes. This short personal account summarizes some of the recent advances in the use of porous hybrid materials as selective sorbents for REE separation and purification, with particular attention devoted to ordered mesoporous silica and carbon-based sorbents.

Structural features of 31 mononuclear octahedral d2-Re(V) monooxo complexes with singly charged oxygen atoms of bidentate chelating (О, N) ligands (L n ) [ReO(L n )(Lmono)3] (n = 1–19; Lmono is a monodentate ligand) have been considered. The O(L n ) atoms are trans to the О(oxo) ligands.

Six new coordination polymers (CPs), namely, [Mn2(OH)(TZI)(DMA)] (1), [Cu2(OH)(TZI)(DMA)]·3.5H2O (2), [Co2(OH)(TZI)(H2O)2] (3), [Zn2(OH)(TZI)(2,2′-bpy)]·H2O (4), [Zn2(OH)(TZI)(phen)]·2H2O (5) and [Zn2(OH)(TZI)(4,4′-bpy)0.5] (6), (H3TZI = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, 4,4′-bpy = 4,4′-bipyridine, and DMA = N,N-dimethylacetamide), have been synthesized under solvo-/hydrothermal conditions. Both 1 and 2 exhibit 3D structures containing butterfly-shaped tetranuclear M4(μ3-OH)2 clusters as secondary building units (SBUs). In 1, the SBUs are connected into 1D chains by the tetrazolate groups of the TZI ligands and the chains are further interlinked into a (4,8)-connected 3D net by the TZI spacers. In 2, the SBUs are directly connected by TZI to give a (3,6)-connected 3D framework. CP 3 features a double-layered structure based on corner-sharing Co3(μ3-OH) triangle Δ-chains in which Co(II) ions are bridged by mixed (μ4-tetrazolate)(μ3-OH)(μ2-COO) bridges. CPs 4–6 were synthesized by the reactions of the H3TZI ligands, Zn(NO3)2 and three different N-donor auxiliary ligands. The auxiliary ligands change from chelating ligands (2,2′-bpy, phen) to 4,4′-bpy, which leads to remarkable structural changes from 2D to 3D. CPs 4 and 5 display 2D structures with dinuclear motifs as SBUs. In 4, the dinuclear motifs with mixed double (μ2-tetrazolate)(μ2-OH) bridges are connected by the TZI spacers to produce a 2D framework. Differently, in 5, the dinuclear motifs with mixed double (μ2-COO)(μ2-OH) bridges are interlinked into a 2D framework with a (4,4)-connected net topology. In 6, the square Zn4O4 clusters are interlinked by the organic ligands into a 3D framework with a (4,10)-connected (44·62)(412·58·616·76·83) topology. Magnetic studies indicate that CPs 1–3 exhibit antiferromagnetic coupling. Further magnetic measurement demonstrates that CPs 1 and 3 show no magnetic ordering above 2 K. CPs 4–6 exhibit strong luminescence with different energies in the solid state at room temperature.

A series of substituted, pyridyl-functionalized 2,4,6-triarylpyrylium salts were prepared and investigated for their light absorption and emission properties. After reaction with P(SiMe3)3, the corresponding λ3-phosphinines were obtained, which carry on the 4- or 6-aryl ring ±I and ±M substituents. Supported by DFT calculations, a systematic evaluation of the σ-donor and π-donor as well as π-acceptor properties of these low-coordinate P,N-hybrid ligands was performed. The modular synthetic approach allowed us at the same time to synthesize the structurally related bipyridine derivatives for comparison reasons. Reaction of the chelating ligands with [W(CO)6] in THF afforded the corresponding [(P^N)W(CO)4] and [(N^N)W(CO)4] complexes. A crystallographic characterization of selected coordination compounds revealed significant structural differences between the pyridyl-phosphinine- and the bipyridine-based compounds. Their characterization by means of IR-spectroscopy gave experimental insight into the electronic properties of the respective ligands.

Our previously reported ‘blue solution’ oxygen-evolution catalyst consists of an isomeric mixture of coordination complexes containing the (pyalk)IrIV–O–IrIV(pyalk) core unit and is thus entirely molecular but only when formed from organometallic precursors such as Cp*Ir(pyalk)Cl or Ir(pyalk)(CO)2 (pyalk = (2-pyridyl)-2-propanolate). We now show that attempts to form it from such obvious coordination precursors as Na[Ir(pyalk)Cl4] or Na[IrCl2(pyalk)(O2CPh)2], under a variety of conditions, always fail in our hands, leading to a mixture of molecular ‘blue solution’ species and IrOx nanoparticles, rather than the purely homogeneous catalyst formed from organometallic precursors. The loss of the pyalk ligand during the oxidative activation is associated with the nanoparticle generation. External chelating ligands also failed to stop the nanoparticle formation. This work implies the paradoxical conclusion that organometallic complexes are effective as catalyst precursors, even when coordination complexes are the catalytically active species, since the inner-sphere organometallic ligands, although ultimately lost or degraded, may nevertheless have a stabilizing effect sufficient to suppress undesirable nanoparticle production pathways in the activation of the catalyst precursor. A key aspect of the present study is that organometallic complexes in general may be useful catalyst precursors even if the organometallic ligands are lost in the activation process.

Intraperitoneal administration of chemotherapeutics is expected for the treatment of peritoneally disseminated gastric cancer because of poor migration of the drugs from the systemic circulation to the peritoneal cavity. In this study, for intraperitoneal delivery of cisplatin (CDDP), we developed a hyaluronan (HA)-based hybrid system in which CDDP-loaded HA nanogels were either physically encapsulated in or chemically conjugated to injectable HA hydrogels. Physical encapsulation enabled sustained release of HA nanogels from the HA hydrogel matrix for over a week. This was a longer release period than that of encapsulated free CDDP, which released 80% of the drug in 2 days. The longer release was attributed to delayed diffusion of HA nanogels from the hydrogel matrix network. The release profile could be tuned by modifying the chemical conjugation of HA nanogels to the HA hydrogel matrix, as well as the type of chelating ligands used to load CDDP to the nanogel. Furthermore, intraperitoneally administered hybrid had significant antitumor activity in a mouse model of peritoneally disseminated gastric cancer, especially for nodules smaller than 1.0 mm.

It has been demonstrated that the reaction of Cat[Ag[B12H12]] or [Ag2[B12H12]] with chelating ligands L (L = bipy, phen) leads to the selective formation of stable [(Ag2(L)2[B12H12]] n 1D polymers irrespective of the nature of cation (Cat) in the starting reagent, the ratio of the reaction components, and the solvent used. The structures of [Ag2(bipy)2[B12H12]] n · 2CH3CN and [Ag2(phen)2[B12H12]] n · DMF have been determined by X-ray crystallography. It has been demonstrated that the [B12H12]2− anion in polymer chains acts as a bridging ligand coordinated to silver atoms through edges or through an edge and a vertex of the icosahedron. The Ag–B(H) and Ag–H(B) distances are within 2.638(3)–3.074(3) and 1.90–2.80 A, respectively. These complexes are the first examples of 1D coordination polymers based on the [B12H12]2− anion and azaheterocyclic ligands L.