Structural study of hydrated/dehydrated manganese thiophene-2,5-diphosphonate metal organic frameworks, Mn2(O3P-C4H2S-PO3)·2H2O

A new series of magnetic and luminescent layered hybrid materials obtained from thianthrene phosphonic acid: M(H2O)PO3-S2C12H7 (M = Cu, Zn) and M(H2O)2(PO2OH-S2C12H7)2 (M = Mn, Co)

Four new metallophosphonates with the chemical formulae M(H2O)PO3-S2C12H7 (M = Cu, Zn) and M(H2O)2(PO2OH-S2C12H7)2 (M = Mn, Co) were synthesized using a hydrothermal route from the original bent rigid thianthrene-2-ylphosphonic acid (TPA). This organic precursor crystallizes in a non-centrosymmetric space group P212121 and presents a unique bent geometry due to the presence of two sulfur atoms in its rigid platform architecture. Obtained as single crystal and polycrystalline powders, the structures of the four hybrid materials were solved using X-ray diffraction on single crystals in a monoclinic P21/c space group. These compounds adopt a lamellar structure consisting of one inorganic subnetwork alternating with a 'sawtooth' double organic -S2C12H7 subnetwork. The inorganic layers of these compounds are made of (PO3C) or partially deprotonated (PO2OHC) tetrahedra connected by the apices to isolated ZnO3(H2O) tetrahedra, Cu2O6(H2O)2 copper dimers and cobalt and manganese MO4(H2O)2 octahedra, where the latter two exhibit an isotype structure. Thermogravimetric analysis was performed to confirm the amount of water molecules present in the formula, to track the dehydration process of the structures, and to evaluate their thermal stability. The magnetic properties of the copper, cobalt, and manganese-based materials were investigated from 2 K to 300 K by using a SQUID magnetometer revealing dominant antiferromagnetic interactions with Weiss temperatures of -8.0, -10, and -1 K, respectively. These magnetic behaviors were further corroborated by first-principles simulations based on Density Functional Theory (DFT). Finally, the absorption and photoluminescence properties of both the ligand and hybrid materials were investigated, revealing diverse excitation and recombination mechanisms. The organic moiety based on thianthrene significantly influenced the absorption and emission, with additional peaks attributed to transition metals. Singlet and triplet states recombination were observed, accompanied by an unidentified quenching mechanism affecting the triplet state lifetime.

An alternative C–P cross-coupling route for the synthesis of novel V-shaped aryldiphosphonic acids

The synthesis of phosphonate esters is a topic of interest for various fields, including the preparation of phosphonic acids to be employed as organic linkers for the construction of metal phosphonate materials. We report an alternative method that requires no solvent and involves a different order of addition of reactants to perform the transition-metal-catalyzed C–P cross-coupling reaction, often referred to as the Tavs reaction, employing NiCl2 as a pre-catalyst in the phosphonylation of aryl bromide substrates using triisopropyl phosphite. This new method was employed in the synthesis of three novel aryl diphosphonate esters which were subsequently transformed to phosphonic acids through silylation and hydrolysis.

The Hydrolysis of Phosphinates and Phosphonates: A Review

Phosphinic and phosphonic acids are useful intermediates and biologically active compounds which may be prepared from their esters, phosphinates and phosphonates, respectively, by hydrolysis or dealkylation. The hydrolysis may take place both under acidic and basic conditions, but the C-O bond may also be cleaved by trimethylsilyl halides. The hydrolysis of P-esters is a challenging task because, in most cases, the optimized reaction conditions have not yet been explored. Despite the importance of the hydrolysis of P-esters, this field has not yet been fully surveyed. In order to fill this gap, examples of acidic and alkaline hydrolysis, as well as the dealkylation of phosphinates and phosphonates, are summarized in this review.

M(H2O)(PO3C10H6OH)·(H2O)0.5 (M = Co, Mn, Zn, Cu): a new series of layered metallophosphonate compounds obtained from 6-hydroxy-2-naphthylphosphonic acid

Four new metallophosphonates M(H₂O)(PO₃C₁₀H₆OH)·(H₂O)_0.5 (M = Mn, Co, Cu, Zn) were obtained as single crystal and polycrystalline powders by hydrothermal synthesis from the precursors 6-hydroxy-2-naphthylphosphonic acid and the corresponding metal salts. These analogous hybrids crystalized in the space group P12₁/c1 in a lamellar structure. Their layered structures consisted of inorganic [M(H₂O)(PO₃C)] layers stacked with organic bilayers of 6-hydroxy-2-naphthyl moieties "HO-C₁₀H₆" and free water molecules. Their structures were determined by single crystal X-ray diffraction and confirmed by powder X-ray diffraction and Le Bail refinement for the powder sample. The removal of water upon heating at 250 °C was studied by thermogravimetric analysis and temperature-dependent powder X-ray diffraction. Their magnetic properties were studied by SQUID magnetometry and show antiferromagnetic behavior for the Co analogue and the occurrence of a canted antiferromagnetic order at T_N = 12.2 K for the Mn analogue. The Cu compound displayed an unprecedented ferromagnetic behavior. Their absorption and luminescence properties were investigated and revealed that the ligand and the compounds displayed a common behavior below a wavelength of 400 nm. Specific absorption bands were found in the compounds with Co²⁺ and Cu²⁺ at 539 nm and 849 nm, respectively. Moreover, particular luminescence bands were found for the compounds with Mn²⁺, Co²⁺ and Zn²⁺ at 598 nm, 551 nm and 530 and 611 nm, respectively.

Further Understanding of the Reactivity Control of Bisphosphonates to a Metal Source for Fabricating Highly Ordered Mesoporous Films

Mesoporous metal organophosphonates having embedded organic functions are a promising platform to hybridize organics and non-siliceous inorganic frameworks in their molecular scale. However, the reactivity between a bisphosphonate and a metal source is dramatically different for their combination and then hampers to construct ordered mesoporous structures even when using amphiphilic organic molecules. By proposing an advanced method to adjust such reactivity, we recently succeeded in fabricating ordered mesoporous aluminum organophosphonate (AOP) films with chemically designable benzene units inside their hybrid frameworks. The reactivity of the organically bridged bisphosphonates has been controlled by utilizing dissimilar reactivities of acid-base pairs like P-OH and P-OEt groups to AlCl₃ . Here, we further prove our reactivity-control concept through the introduction of organic groups, such as those having symmetric thiophene, asymmetric amide, and hydrophilic ether units. Liquid-state ³¹ P NMR measurements further clarified the usefulness of the control of the -OH/ -OEt ratio in the same bisphosphonate molecules for obtaining highly ordered mesostructured AOP films.

Manganese Fluorene Phosphonates: Formation of Isolated Chains

9,9-dimethylfluorenyl-2-phosphonic acid 1 was reacted with manganese nitrate tetrahydrate to produce under hydrothermal conditions the crystalline manganese phosphonate Mn(H2O)2[O2(OH)PC15H13]2·2H2O which crystallize in the P21/c space group. This compound is a rare example of Mn-phosphonate material featuring isolated chains. The interactions between these chains containing the 9,9-dimethylfluorenyl moieties, result from Van der Waals interactions involving the fluorene ligands and C···H–C hydrogen bonds as revealed by Hirshfeld Surfaces. This material features antiferromagnetic exchange interactions as revealed by the magnetic susceptibility as a function of the temperature.

Phosphonic acid: preparation and applications

The phosphonic acid functional group, which is characterized by a phosphorus atom bonded to three oxygen atoms (two hydroxy groups and one P=O double bond) and one carbon atom, is employed for many applications due to its structural analogy with the phosphate moiety or to its coordination or supramolecular properties. Phosphonic acids were used for their bioactive properties (drug, pro-drug), for bone targeting, for the design of supramolecular or hybrid materials, for the functionalization of surfaces, for analytical purposes, for medical imaging or as phosphoantigen. These applications are covering a large panel of research fields including chemistry, biology and physics thus making the synthesis of phosphonic acids a determinant question for numerous research projects. This review gives, first, an overview of the different fields of application of phosphonic acids that are illustrated with studies mainly selected over the last 20 years. Further, this review reports the different methods that can be used for the synthesis of phosphonic acids from dialkyl or diaryl phosphonate, from dichlorophosphine or dichlorophosphine oxide, from phosphonodiamide, or by oxidation of phosphinic acid. Direct methods that make use of phosphorous acid (H3PO3) and that produce a phosphonic acid functional group simultaneously to the formation of the P-C bond, are also surveyed. Among all these methods, the dealkylation of dialkyl phosphonates under either acidic conditions (HCl) or using the McKenna procedure (a two-step reaction that makes use of bromotrimethylsilane followed by methanolysis) constitute the best methods to prepare phosphonic acids.

Spectrally-resolved third-harmonic generation and the fundamental role of O-HCl hydrogen bonding in Oh, Td-cobalt(ii) tetraphenylmethane-based coordination polymers

The reaction of a phosphonate-diester tetraphenylmethane-based tecton, tetrakis[4-(diethoxyphosphoryl)phenyl]methane, (L) with cobalt(ii) chloride afforded a centrosymmetric coordination polymer (CP), [L·2Co(H₂O)₄²⁺·2CoCl₄^2-]_n, 2-Cl, possessing simultaneously octahedral (O_h) and tetrahedral (T_d) metal centers. This material served as a model compound for the demonstration of factors influencing the spectral dependence of one of the nonlinear optical (NLO) phenomena, the third-harmonic generation (THG). The spectrally-resolved THG (SR-THG) measurements in the range from 1125 to 1750 nm revealed that a maximum of THG response is obtained when the fundamental beam is around 1300 nm. The SR-THG study was combined with an analysis of the self-absorption effects of pumping and of third-harmonic radiation; based on these results, we put forward a hypothesis that the THG action spectrum is influenced more by the ability of the material to self-absorb the third harmonic rather than by the extent of self-absorption of the pumping radiation. Apart from investigations of NLO properties, we have explored coordination and particularly the supramolecular interactions that build up the 2-Cl CP. Despite the tetrahedral, spatial shape of the ligand L, CP 2-Cl has a two-dimensional net. The structure was found to be strongly supported by O-HCl hydrogen bonds, since each CoCl₄^2- complex anion is an acceptor of eight of such interactions within a distorted square grid layer of cobalt(ii) ions. While coordination and hydrogen-bonded nets are both featuring the sql topology when treated separately, the consideration of both of them as topological paths yields a trinodal 4,4,6-connected net, described by the point symbol (4²·8⁴)(4⁵·6)₂(4⁶·6⁶·8³)₂. SR-THG and structural studies of 2-Cl have been also supported by far- and mid-infrared spectroscopy, UV-Vis-NIR solid state absorption analysis, thermogravimetry and preliminary magnetic characterization.

Silver-based hybrid materials from meta- or para-phosphonobenzoic acid: influence of the topology on silver release in water

Three novel silver-based metal-organic frameworks materials, which were synthesized from either 3-phosphono or 4-phosphonobenzoic acid and silver nitrate, are reported. The novel hybrids were synthesized under hydrothermal conditions; the pH of the reaction media was controlled by adding different quantities of urea thereby producing different topologies. Compound 1 (Ag3(4-PO3-C6H4-COO)), synthesized in the presence of urea, exhibits a compact 3D structure in which both phosphonic acid and carboxylic acid functional groups are linked to the silver-based inorganic network. Compound 2 (Ag(4-PO3H-C6H4-COOH)), which was synthesized at lower pH (without urea), has a layered structure in which only the phosphonic acid functional groups from 4-phosphonobenzoic acid moieties are linked to the silver inorganic network; the carboxylic acid groups being engaged in hydrogen bonds. Finally, material 3 (Ag(3-PO3H-C6H4-COOH)) was synthesized from 3-phosphonobenzoic acid and silver nitrate without urea. This material 3 features a layered structure exhibiting carboxylic acid functional groups linked via hydrogen bonds in the interlayer space. After the full characterization of these materials (single X-ray structure, IR, TGA), their ability to release silver salts in aqueous environment was measured. Silver release, determined in aqueous solution by cathodic stripping voltammetry, shows that the silver release capacity of these materials is dependent on the topology of the hybrids. The more compact structure 1 is extremely stable in water with only trace levels of silver ions being detected. On the other hand, compounds 2 and 3, in which only the phosphonic acid functional groups were bonded to the inorganic network, released larger quantities of silver ions into aqueous solution. These results which were compared with the silver release of the previously described compound 4 (Ag6(3-PO3-C6H4-COO)2). The results clearly show that the release capacity of silver-based metal organic framework can be tuned by modifying their topology which, in the present study, is governed by the regio-isomer of the organic precursor and the synthetic conditions under which the hybrids are prepared.