Supramolecular chemistry and complexation abilities of diphosphonic acids

Increasing photoeradication's efficiency of Acinetobacter baumannii by polyphosphonic chelating agents

Ethylenediamine-N,N,N',N'-tetrakis(methylenephosphonic acid (EDTMP), nitrilotri(methylphosphonic acid (ATMP) and zoledronic acid were studied to enhance the methylene blue-mediated photodynamic inactivation of Acinetobacter baumannii. Laser light (wavelength 638 nm; standard light output 40 mW) was used in all experiment. Planktonic cultures were irradiated for 10, 20 and 30 min which corresponded to the light dose of 63 Jcm‒ 2, 126 Jcm‒2 and 189 Jcm‒2. Biocidal effect depended on the exposure time and it was shown that MB alone caused the highest reduction in the number of viable cells by 3.10 ± 0.2 log10 units after 30 min of irradiation. A significantly more effective killing effect was achieved when the bacteria were pre-treated with zoledronate, ATMP, or EDTMP (prior to photosensitisation) as the number of viable bacteria was reduced by 4.04±0.2 log10, 3.95±0.2 log10 and 4.01 ± 0.2 log10, respectively. The photo-killing effect caused by MB against biofilm pre-incubated with zoledronate, ATMP, or EDTMP and the number of viable bacteria was reduced by 0.80±0.1 log10, 1.25±0.05 log10 and 0.65±0.05 log10, respectively. Polyphosphonic chelating agents increased the efficiency of photo-destruction of A. baumannii by increasing the amount of bound photosensitizer by planktonic cells and biofilm, and increasing the detachment of live planktonic cells from the biofilm. The presence of glucose in the photosensitizing system significantly affected the bacterial photo-elimination. Pre-incubation of planktonic bacteria with the studied polyphosphonic chelating agents in the presence of glucose, and then exposure to light (with MB) for 30 min caused the lethal effect. This photo-eradication protocol (in the case of biofilms) reduced the number of viable bacteria by 2.05±0.2 log10, 3.2±0.2 log10 and 2.02±0.2 log10 for zoledronic acid, ATMP and EDTMP, respectively.

Multipod Bi(Cu2-xS)n Nanocrystals formed by Dynamic Cation-Ligand Complexation and Their Use as Anodes for Potassium-Ion Batteries

We report the formation of an intermediate lamellar Cu-thiolate complex, and tuning its relative stability using alkylphosphonic acids are crucial to enabling controlled heteronucleation to form Bi(Cu_2-xS)_n heterostructures with a tunable number of Cu_2-xS stems on a Bi core. The denticity of the phosphonic acid group, concentration, and chain length of alkylphosphonic acids are critical factors determining the stability of the Cu-thiolate complex. Increasing the stability of the Cu-thiolate results in single Cu_2-xS stem formation, and decreased stability of the Cu-thiolate complex increases the degree of heteronucleation to form multiple Cu_2-xS stems on the Bi core. Spatially separated multiple Cu_2-xS stems transform into a support network to hold a fragmented Bi core when used as an anode in a K-ion battery, leading to a more stable cycling performance showing a specific capacity of ∼170 mAh·g^-1 after 200 cycles compared to ∼111 mAh·g^-1 for Bi-Cu_2-xS single-stem heterostructures.

Chelate assisted phytoextraction for effective rehabilitation of heavy metal(loid)s contaminated lands

The contamination of lands and water by heavy toxic metal(loid)s is an environmental issue that needs serious attention as it poses a major threat to public health. The persistence of heavy metals/metalloids in the environment as well as their potentially dangerous effects on organisms underpins the need to restore the areas contaminated by heavy toxic metal(loid)s. Soil restoration can be achieved through a variety of different methods. Being more cost-effective and environmentally sustainable, phytoremediation has recently replaced traditional processes like soil washing and burning. Many plants have been intensively explored to eliminate various heavy metals from polluted soils through phytoextraction, which is a commonly used phytoremediation approach. The ability of chelants to enhance phytoextraction potential has also received wide attention owing to their ability to elevate the efficiency of plants in removing heavy metal(loid)s. Chelants have been found to improve plant growth and the activity of the defense system. Several chelants, either non-biodegradable or biodegradable, have been reported to augment the phytoextraction efficiencies of various plants. The problem of the leaching of heavy metal(loid)s and secondary pollution caused by non-biodegradable chelants can be overcome by the use of biodegradable chelants to an extent. This review is a brief report focusing on recent articles on chelate-assisted phytoextraction of heavy metal (loids) As, Cd, Cu, Cr, Hg, Ni, Pb, U, and Zn.

Cyclam with a phosphinate-bis(phosphonate) pendant arm is a bone-targeting carrier of copper radionuclides

Ligands combining a bis(phosphonate) group with a macrocycle function as metal isotope carriers for radionuclide-based imaging and for treating bone metastases associated with several cancers. However, bis(phosphonate) pendant arms often slow down complex formation and decrease radiochemical yields. Nevertheless, their negative effect on complexation rates may be mitigated by using a suitable spacer between bis(phosphonate) and the macrocycle. To demonstrate the potential of bis(phosphonate) bearing macrocyclic ligands as a copper radioisotope carrier, we report the synthesis of a new cyclam derivative bearing a phosphinate-bis(phosphonate) pendant (H₅te1P^BP). The ligand showed a high selectivity to Cu^II over Zn^II and Ni^II ions, and the bis(phosphonate) group was not coordinated in the Cu^II complex, strongly interacting with other metal ions in solution. The Cu^II complex formed quickly, in 1 s, at pH 5 and at a millimolar scale. The complexation rates significantly differed under a ligand or metal ion excess due to the formation of reaction intermediates differing in their metal-to-ligand ratio and protonation state, respectively. The Cu^II-te1P^BP complex also showed a high resistance to acid-assisted hydrolysis (t_1/2 2.7 h; 1 M HClO₄, 25 °C) and was effectively adsorbed on the hydroxyapatite surface. H₅te1P^BP radiolabeling with [⁶⁴Cu]CuCl₂ was fast and efficient, with specific activities of approximately 30 GBq ⁶⁴Cu per 1 μmol of ligand (pH 5.5, room temperature, 30 min). In a pilot experiment, we further demonstrated the excellent suitability of [⁶⁴Cu]Cu^II-te1P^BP for imaging active bone compartments by dedicated small animal PET/CT in healthy mice and subsequently in a rat femoral defect model, in direct comparison with [¹⁸F]fluoride. Moreover, [⁶⁴Cu]Cu^II-te1P^BP showed a higher uptake in critical bone defect regions. Therefore, our study highlights the potential of [⁶⁴Cu]Cu^II-te1P^BP as a PET radiotracer for evaluating bone healing in preclinical and clinical settings with a diagnostic value similar to that of [¹⁸F]fluoride, albeit with a longer half-life (12.7 h) than ¹⁸F (1.8 h), thereby enabling extended observation times.

Giant zirconium-bisphosphonate nano-ribbons and their liquid crystalline phase behaviour in water

In decimolar aqueous solutions, zirconium oxychloride octahydrate forms several micrometer long and approximately 15 nm wide thin ribbons through the reaction with excess amounts of the sodium salt of 1-hydroxyethane-1,1-diphosphonic acid (HEDP, known as etidronic acid). Primarily deduced from SAXS, TEM, EXAFS and solid-state NMR analyses, a consistent structural model enables congruous explanations for the colloidal behaviour of the purified ribbons as well as of their reaction products with ammonia and amines, respectively. Properties of the lyotropic, liquid crystalline phases are discussed in the light of potential applications in aqueous coatings.

Bisphosphonate-based nanocomposite hydrogels for biomedical applications

Nanocomposite hydrogels consist of polymeric network embedded with functional nanoparticles or nanostructures, which not only contribute to the enhanced mechanical properties but also exhibit the bioactivities for regulating cell behavior. Bisphosphonates (BPs) are capable of coordinating with various metal ions and modulating bone homeostasis. Thanks to the inherent dynamic properties of metal-ligand coordination bonds, BP-based nanocomposite hydrogels possess tunable mechanical properties, highly dynamic structures, and the capability to mediate controlled release of encapsulated therapeutic agents, thereby making them highly versatile for various biomedical applications. This review presents the comprehensive overview of recent developments in BP-based nanocomposite hydrogels with an emphasis on the properties of embedded nanoparticles (NPs) and interactions between hydrogel network and NPs. Furthermore, various challenges in the biomedical applications of these hydrogels are discussed to provide an outlook of potential clinical translation.

Multi-target heteroleptic palladium bisphosphonate complexes

Bisphosphonates are the most commonly prescribed drugs for the treatment of osteoporosis and other bone illnesses. Some of them have also shown antiparasitic activity. In search of improving the pharmacological profile of commercial bisphosphonates, our group had previously developed first row transition metal complexes with N-containing bisphosphonates (NBPs). In this work, we extended our studies to heteroleptic palladium-NBP complexes including DNA intercalating polypyridyl co-ligands (NN) with the aim of obtaining potential multi-target species. Complexes of the formula [Pd(NBP)₂(NN)]·2NaCl·xH₂O with NBP = alendronate (ale) or pamidronate (pam) and NN = 1,10 phenanthroline (phen) or 2,2'-bipyridine (bpy) were synthesized and fully characterized. All the obtained compounds were much more active in vitro against T. cruzi (amastigote form) than the corresponding NBP ligands. In addition, complexes were nontoxic to mammalian cells up to 50-100 µM. Compounds with phen as ligand were 15 times more active than their bpy analogous. Related to the potential mechanism of action, all complexes were potent inhibitors of two parasitic enzymes of the isoprenoid biosynthetic pathway. No correlation between the anti-T. cruzi activity and the enzymatic inhibition results was observed. On the contrary, the high antiparasitic activity of phen-containing complexes could be related to their ability to interact with DNA in an intercalative-like mode. These rationally designed compounds are good candidates for further studies and good leaders for future drug developments. Four new palladium heteroleptic complexes with N-containing commercial bisphosphonates and DNA intercalating polypyridyl co-ligands were synthesized and fully characterized. All complexes displayed high anti-T. cruzi activity which could be related to the inhibition of the parasitic farnesyl diphosphate synthase enzyme but mainly to their ability to interact DNA.

Changes in magnetic order through two consecutive dehydration steps of metal-phosphonate diamond chains

Hydrothermal reactions of the multitopic ligand 1-hydroxy-1-(piperidin-4-yl)methylidenebisphosphonic acid (hpdpH₄) with cobalt or nickel sulfates afforded two new isostructural metal phosphonates, M₃^II(hpdpH)₂(H₂O)₆·4H₂O [M = Co (Co-10H₂O), Ni (Ni-10H₂O)]. Their structures consist of parallel diamond chains of three MO₆ octahedra bridged by the PO₃C tetrahedra. Six of the seven oxygen atoms of the ligand are involved in coordination; for two ligands that amounts to 12 bonds for 3 MO₆ and the remaining six are occupied by terminal water molecules. In addition, four water molecules sit in between the chains providing H-bonds to the formation of a 3D-net. Thermal analyses show identical two-step dehydration processes involving first the departure of six water molecules followed by the remaining four. A detailed study of the ac- and dc-magnetization as a function of temperature, field and frequency reveals associated drastic changes. The virgin form Co-10H₂O is a paramagnet while its partial dehydrated form Co-4H₂O is an antiferromagnet displaying canting below T_N = 4.7 K and the fully dehydrated form Co is a ferrimagnet (T_C = 12 K). Ni-10H₂O and Ni-4H₂O exhibit long-range ordered antiferromagnetism (T_N = 2.7 and 4.0 K, respectively) and also become ferrimagnets (T_C = 9.4 K) when fully dehydrated to Ni. The dehydrated samples can be fully rehydrated with the complete recovery of both the structures and magnetic properties.

M₃^II(hpdpH)₂(H₂O)₆·4H₂O (M = Co, Ni) experience identical two-step dehydration processes associated with drastic magnetic changes from paramagnet to antiferromagnet/metamagnetic to ferrimagnet for M = Co, and from antiferromagnet to antiferromagnet to ferrimagnet for M = Ni.

Effects of soil amendments on the growth response and phytoextraction capability of a willow variety (S. viminalis × S. schwerinii × S. dasyclados) grown in contaminated soils

This study was conducted to evaluate the effects of lime and bisphosphonates (BPs) such as N10O chelate amendment on the growth, physiological and biochemical parameters, and phytoextraction potential of the willow variety Klara (Salix viminalis × S. schwerinii × S. dasyclados) grown in soils heavily contaminated with copper (Cu), nickel (Ni) and zinc (Zn). The plants were irrigated with tap or processed water (mine wastewater). The results suggest that the combined effects of the contaminated soil and processed water inhibited growth parameters, gas exchange parameters and chlorophyll fluorescence (Fv/Fm) values. In contrast, malondialdehyde (MDA) content, organic acids, total phenolic and total flavonoid contents, and the accumulation of metals/metalloids in the plant tissues were increased compared to the control. When the soil was supplemented with lime and N10O; growth, physiological, biochemical parameters, and resistance capacity were significantly higher compared to unamended soil treatments, especially in the contaminated soil treatments. The combined lime‒ and N10O‒amended soil treatment produced higher growth rates, resistance capacity, photosynthesis rates and phytoextraction efficiency levels relative to either the lime‒amended or the N10O‒amended soil treatments. This study provides practical evidence of the efficient chelate‒assisted phytoextraction capability of Klara and highlights its potential as a viable and inexpensive novel approach for in situ remediation of Cu‒, Ni‒ and Zn‒contaminated soils and mine wastewaters.

Highly Dynamic Nanocomposite Hydrogels Self-Assembled by Metal Ion-Ligand Coordination

Hydrogels are emerging biomaterials with desirable physicochemical characteristics. Doping of metal ions such as Ca²⁺ , Mg²⁺ , and Fe²⁺ provides the hydrogels with unique attributes, including bioactivity, conductivity, and tunability. Traditionally, this doping is achieved by the interaction between metal ions and corresponding ligands or the direct incorporation of as-prepared metal-based nanoparticles (NPs). However, these approaches rely on a complex and laborious preparation and are typically restricted to few selected ion species. Herein, by mixing aqueous solutions of ligands (bisphosphonates, BPs), polymer grafted with ligands, and metal ions, a series of self-assembled metallic-ion nanocomposite hydrogels that are stabilized by the in situ formed ligand-metal ion (BP-M) NPs are prepared. Owing to the universal coordination between BPs and multivalent metal ions, the strategy is highly versatile and can be generalized for a wide array of metal ions. Such hydrogels exhibit a wide spectrum of mechanical properties and remarkable dynamic properties, such as excellent injectability, rapid stress relaxation, efficient ion diffusion, and triggered disassembly for harvesting encapsulated cells. Meanwhile, the hydrogels can be conveniently coated or patterned onto the surface of metals via electrophoresis. This work presents a universal strategy to prepare designer nanocomposite materials with highly tunable and dynamic behaviors.

Deciphering preferred solid-state conformations in nitrogen-containing bisphosphonates and their coordination compounds. A case study of discrete Cu(ii) complexes based on Cα-substituted analogues of zoledronic acid: crystal structures and solid-state characterization

Conformation diversity of N-containing bisphosphonic acids and related anions within their metal complexes and salts.

Low pH constructed Co(ii) and Ni(ii) 1D coordination polymers based on Cα-substituted analogues of zoledronic acid: structural characterization, and spectroscopic and magnetic properties

Three novel coordination compounds based on α,α-disubstituted analogues of zoledronic acid with a cyclopropane (cpp) or cyclobutane (cbt) ring on the C_α carbon, isomorphous [Co(H₂cppZol)(H₂O)]·H₂O (1a), [Ni(H₂cppZol)(H₂O)]·H₂O (1b) and [Co(H₂cbtZol)(H₂O)]·H₂O (2a), were synthesized under hydrothermal conditions at low pH. Single-crystal X-ray diffraction analysis revealed that all the compounds had a 1D double zig–zag chain architecture with an 8 + 8 ring motif formed by alternately arranged symmetrical (–O–P–O–)₂ bridges linking equivalent octahedral metal centres. Both the ligand coordination mode and chain architecture displayed by 1a, 1b and 2a are unique among 1D [M(H₂L)(H₂O)_x]·yH₂O coordination polymers based on nitrogen-containing bisphosphonates reported so far. All the compounds exhibit similar decomposition pathways upon heating with thermal stabilities decreasing in the order 1b > 1a > 2a. The IR spectra revealed that lattice water release above 227, 178 and 97 °C, respectively, does not change the chain architecture leaving them intact up to ca. 320, 280 and 240 °C. Magnetic behaviour investigations indicated that 1a, 2a and 1b exhibit weak alternating antiferromagnetic–ferromagnetic exchange interactions propagated between the magnetic centres through double (–O–P–O–)₂ bridges. The boundary between antiferro- and ferromagnetic couplings for the Co–O⋯O–Co angle in 1a and 2a was estimated to be ca. 80°. This value is also applicable for recently reported [M₃(HL)₂(H₂O)₆]·6H₂O (M = Co, Ni) complexes based on α,α-disubstituted analogues of zoledronic acid and can be used to the explain magnetic behaviour of 1b.

1D Co(ii)/Ni(ii) coordination polymers with alternating antiferromagnetic–ferromagnetic exchange interactions between metal centers propagated through double (–O–P–O–)₂ bridges.

Use of poly(vinylidene fluoride-co-vinyl dimethylphosphonate) copolymers for efficient extraction of valuable metals

The radical copolymerisation of vinylidene fluoride (VDF) with vinyl dimethyl phosphonate (VDMP) initiated by various kinds of initiators is presented.

Thermodynamics of the Interactions of Aminobisphosphonates and Their Calcium Complexes with Bovine Serum Albumin

Binding of bisphosphonates (BPs) to plasma proteins was investigated in the 1990s as a pharmacokinetic issue in order to fully understand bio-distribution of BP drugs which are successfully used for the treatment of several bone-related diseases. It has been hypothesized that binding to these proteins occurs with low to moderate affinity despite of unfavorable hydrophilicity of BPs, and Ca²⁺ was identified as a strong catalyst of this binding. However, these studies mainly consisted in the separation and quantification of bound and unbound drug or protein fractions using chromatographic techniques without an outcome on the molecular level. Presented thermodynamic studies analyze the interactions of three N-BPs as well as their Ca²⁺ complexes with bovine serum albumine (BSA) by means of isothermal calorimetry. The studies reveal spontaneous enthalpy favored interactions of N-BPs (amino-containing BPs) with BSA, which are enhanced by the presence of Ca²⁺ ions up to ~15-fold, strongly depending on N-BP. Those are low affinity binding events, comparable to Ca²⁺ -N-BP interactions, which most likely occur at Ca²⁺ binding site(s). It is a first example of estimation of thermodynamic forces of interactions of free and calcium-bound N-BPs with albumin.

Ibandronate metal complexes: solution behavior and antiparasitic activity

To face the high costs of developing new drugs, researchers in both industry and academy are looking for ways to repurpose old drugs for new uses. In this sense, bisphosphonates that are clinically used for bone diseases have been studied as agents against Trypanosoma cruzi, causative parasite of Chagas disease. In this work, the development of first row transition metal complexes (M = Co²⁺, Mn²⁺, Ni²⁺) with the bisphosphonate ibandronate (iba, H₄iba representing the neutral form) is presented. The in-solution behavior of the systems containing iba and the selected 3d metal ions was studied by potentiometry. Mononuclear complexes [M(H_xiba)]^(2-x)- (x = 0-3) and [M(Hiba)₂]^4- together with the formation of the neutral polynuclear species [M₂iba] and [M₃(Hiba)₂] were detected for all studied systems. In the solid state, complexes of the formula [M₃(Hiba)₂(H₂O)₄]·6H₂O were obtained and characterized. All obtained complexes, forming [M(Hiba)]^- species under the conditions of the biological studies, were more active against the amastigote form of T. cruzi than the free iba, showing no toxicity in mammalian Vero cells. In addition, the same complexes were selective inhibitors of the parasitic farnesyl diphosphate synthase (FPPS) enzyme showing poor inhibition of the human one. However, the increase of the anti-T. cruzi activity upon coordination could not be explained neither through the inhibition of TcFPPS nor through the inhibition of TcSPPS (T. cruzi solanesyl-diphosphate synthase). The ability of the obtained metal complexes of catalyzing the generation of free radical species in the parasite could explain the observed anti-T. cruzi activity.

Aminobisphosphonates based on cyclohexane backbone as coordinating agents for metal ions. Thermodynamic, spectroscopic and biological studies

Complex formation equilibria of calcium, magnesium, copper and nickel with amino-bisphosphonic ligands are described, together with a speciation study along with calorimetric outcome and cytotoxicity characteristics.

1D Co(ii) coordination polymers based on cyclobutyl- and cyclopentyl-substituted zoledronate analogues: synthesis, structural comparison, thermal stability and magnetic properties

Competing magnetic exchange in 1a and 2a with predominant participation of antiferromagnetic interactions in 1a and ferromagnetic exchange in 2a.

Synthesis, structural characterization and computational studies of catena-poly[chlorido[μ3-(pyridin-1-ium-3-yl)phosphonato-κ3O:O':O'']zinc(II)]

Coordination polymers are constructed from two basic components, namely metal ions, or metal-ion clusters, and bridging organic ligands. Their structures may also contain other auxiliary components, such as blocking ligands, counter-ions and nonbonding guest or template molecules. The choice or design of a suitable linker is essential. The new title zinc(II) coordination polymer, [Zn(C₅H₅NO₃P)Cl]_n, has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction and vibrational spectroscopy (FT-IR and FT-Raman). Additionally, computational methods have been applied to derive quantitative information about interactions present in the solid state. The compound crystallizes in the monoclinic space group C2/c. The four-coordinated Zn^II cation is in a distorted tetrahedral environment, formed by three phosphonate O atoms from three different (pyridin-1-ium-3-yl)phosphonate ligands and one chloride anion. The Zn^II ions are extended by phosphonate ligands to generate a ladder chain along the [001] direction. Adjacent ladders are held together via N-H...O hydrogen bonds and offset face-to-face π-π stacking interactions, forming a three-dimensional supramolecular network with channels. As calculated, the interaction energy between the neighbouring ladders is -115.2 kJ mol^-1. In turn, the cohesive energy evaluated per asymmetric unit-equivalent fragment of a polymeric chain in the crystal structure is -205.4 kJ mol^-1. This latter value reflects the numerous hydrogen bonds stabilizing the three-dimensional packing of the coordination chains.

Poly(vinylidene fluoride) Containing Phosphonic Acid as Anticorrosion Coating for Steel

Vinylidene fluoride (VDF)-based copolymers bearing pendant phosphonic acid function for potential application as anticorrosion coatings were synthesized via free radical copolymerization of VDF with a new phosphorus containing 2-trifluoromethacrylate monomer, (dimethoxyphosphoryl)methyl 2-(trifluoromethyl)acrylate (MAF-DMP). MAF-DMP was prepared from 2-trifluoromethacrylic acid in 60% overall yield. Radical copolymerizations of VDF with MAF-DMP initiated by tert-amyl peroxy-2-ethylhexanoate at varying ([VDF]₀/[MAF-DMP]₀) feed ratios led to several poly(VDF-co-MAF-DMP) copolymers having different molar percentages of VDF (79-96%) and number-average molecular weights (M_n's) up to ca. 10 000 g mol^-1 in fair yields (47-53%). Determination of the composition and microstructure of all the synthesized copolymers was done by ¹H and ¹⁹F NMR spectroscopies. The monomer reactivity ratios of this new VDF/MAF-DMP pair were also determined (r_VDF = 0.76 ± 0.34 and r_MAF-DMP = 0 at 74 °C). The resulting poly(VDF-co-MAF-DMP) copolymers exhibited high melting temperature (162-171 °C, with respect to the VDF content), and the degree of crystallinity reached up to 51%. Finally, the pendant dimethyl phosphonate ester groups of the synthesized poly(VDF-co-MAF-DMP) copolymer were quantitatively hydrolyzed, giving rise to novel phosphonic acid-functionalized PVDF (PVDF-PA). In comparison to hydrophobic poly(VDF-co-MAF-DMP) copolymers (the water contact angle, WCA, was 98°), the hydrophilic character of the PVDF-PA was found to be surprisingly rather pronounced, exhibiting low WCA (15°). Finally, steel plates coated with PVDF-PA displayed satisfactory anticorrosion properties under simulated seawater environment.

Two isomorphous Co(ii) coordination polymers based on new α,α-disubstituted derivatives of zoledronic acid: synthesis, structures and properties

1D Co(ii) coordination polymers based on new derivatives of zoledronic acid. Spectroscopic and magnetic characterization.

Structural, spectral and magnetic studies of two Co(II)-N-heterocyclic diphosphonates based on multinuclear units

Two examples of Co(II)-N-heterocyclic coordination polymers based on 1-hydroxyethylidenediphosphonic acid (H5L=CH3C(OH)(PO3H2)2), namely 0.5(H3NCH2CH2NH3)·[Co6(Cl2)(H3L)2(H2L)(HL)(2,2'-bipy)6] 1 and 2(NH4)·[Co3(HL)2(H2O)2(phen)2]·2(H2O) 2, have been solvothermally obtained by introducing the second ligands 2,2'-bipyridine/1,10-phenanthroline (2,2'-bipy/phen) and characterized by powder X-ray diffraction (PXRD), elemental analysis, IR, TG-DSC. The single-crystal X-ray diffractions show that compound 1 possesses a 0-D structure with hexa-nuclear cluster [Co6(O-P-O)8] built through single/double O-P-O bridges and compound 2 displays a 1-D ladder-like chain structure with magnetic topology building blocks [Co4(O-P-O)4]n. Then H-bonding and π-π stacking interactions further expand the two low-dimensional structures into three-dimensional supramolecular frameworks. Fluorescent measurements reveal that both the maximum emission peaks of 1-2 are centered at 423nm, mainly deriving from intraligand π*-π transition state of N-heterocyclic ligand 2,2'-bipy/phen, respectively. Magnetism data indicate that 1 exhibits antiferromagnetic behavior within hexa-nuclear Co(II) clusters, while 2 shows weak ferromagnetic interactions in 1-D topology Co(II)-chain, showing promising potential as magnetic materials.

Multidimensional (0D to 3D) Alkaline-Earth Metal Diphosphonates: Synthesis, Structural Diversity, and Luminescence Properties

A series of new alkaline-earth metal diphosphonate frameworks were successfully synthesized under solvothermal reaction condition (160 °C, 3 d) using 1-hydroxyethylidene-1,1-diphosphonic acid (CH3C(OH)(H2PO3)2, hedpH4) as a diphosphonate building block and Mg(II), Ca(II), Sr(II), or Ba(II) ions as alkaline-earth metal ion centers in water, dimethylformamide, and/or EtOH media. These diphosphonate frameworks, (H2NMe2)4[Mg(hedpH2)3]·3H2O (1), (H2NMe2)2[Ca(hedpH2)2] (2), (H2NMe2)2[Sr3(hedpH2)4(H2O)2] (3), and [Ba3(hedpH2)3]·H2O (4) exhibited interesting structural topologies (zero-, one-, two-, and three-dimensional (0D, 1D, 2D, and 3D, respectively)), which are mainly depending on the metal ions and the solvents used in the synthesis. The single-crystal analysis of these newly synthesized compounds revealed that 1 was a 0D molecule, 2 has 1D chains, 3 was a 3D molecule, and 4 has 2D layers. All compounds were further characterized using thermogravimetric analysis, solid-state (31)P NMR, powder X-ray diffraction analysis, UV-vis spectra, and infrared spectroscopy. In addition, Eu(III)- and Tb(III)-doped compounds of 1-4, namely, (H2NMe2)4[Ln(x)Mg(1-x)(hedpH2)2(hedpH(2-x))]·3H2O (1Ln), (H2NMe2)2[Ln(x)Ca(1-x)(hedpH2)(hedpH(2-x))] (2Ln), (H2NMe2)2[Ln(x)Sr(3-x)(hedpH2)3(hedpH(2-x))(H2O)2] (3Ln), and [Ln(x)Ba(3-x)(hedpH2)2(hedpH(2-x))]·H2O (4Ln) (where Ln = Eu, Tb), were synthesized, and their photoluminescence properties were studied. The quantum yield of 1Eu-4Eu was measured with reference to commercial red phosphor, Y2O2S:Eu(3+) (YE), and the quantum yield of terbium-doped compounds 1Tb-4Tb was measured with reference to commercial green-emitting phosphor CeMgAl10O17:Tb(3+). Interestingly, the compound 2Eu showed very high quantum yield of 92.2%, which is better than that of the reference commercial red phosphor, YE (90.8%).

Crystal structure of bis-[(1-ammonio-1-phosphono-eth-yl)phospho-nato]tetra-aqua-cadmium dihydrate: a powder X-ray diffraction study

In the compound [CdL₂(H₂O)₄]·2H₂O [L = (1-ammonio-1-phosphono­eth­yl)phospho­nate, C₂H₈NO₆P₂⁻], the Cd^II ion is situated on an inversion centre being coordinated by four aqua mol­ecules in the equatorial plane and two deprotonated phospho­nate O atoms from two L ligands in the axial positions in a distorted octa­hedral geometry. Each ligand L exists in a zwitterionic form, and with an intra­molecular O—H⋯O inter­action forming an S(6) ring motif and two intra­molecular N—H⋯O inter­actions each generating an S(5) ring motif. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds link complex mol­ecules into a three-dimensional network with voids of 38 ų filled with ordered lattice water mol­ecules, which are also involved in O—H⋯O hydrogen bonding.

In the title compound, [CdL₂(H₂O)₄]·2H₂O [L = (1-ammonio-1-phosphono­eth­yl)phospho­nate, C₂H₈NO₆P₂⁻], the Cd^II ion is situated on an inversion centre being coordinated by four aqua mol­ecules in the equatorial plane and two phosphonate O atoms from two deprotonated L ligands in the axial positions in a distorted octa­hedral geometry. The asymmetric unit contains one-half of the complex mol­ecule and one lattice water mol­ecule. The ligand L exists in a zwitterionic form, with a positive charge on the NH₃ group and a negative charge on the O atom of the non-coordinating phospho­nate group, and with an intra­molecular O—H⋯O inter­action forming an S(6) ring motif and two intra­molecular N—H⋯O inter­actions each generating an S(5) ring motif. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds link the complex mol­ecules into a three-dimensional network in which the voids of 38 ų are filled with ordered lattice water mol­ecules, which are also involved in O—H⋯O hydrogen bonding.

Advanced material and approach for metal ions removal from aqueous solutions

A Novel approach to remove metals from aqueous solutions has been developed. The method is based on a resin free, solid, non-toxic, microcrystalline bisphosphonate material, which has very low solubility in water (59 mg/l to ion free Milli-Q water and 13 mg/l to 3.5% NaCl solution). The material has been produced almost quantitatively on a 1 kg scale (it has been prepared also on a pilot scale, ca. 7 kg) and tested successfully for its ability to collect metal cations from different sources, such as ground water and mining process waters. Not only was this material highly efficient at collecting several metal ions out of solution it also proved to be regenerable and reusable over a number of adsorption/desorption, which is crucial for environmental friendliness. This material has several advantages compared to the currently used approaches, such as no need for any precipitation step.