Strontium Complexes Research Articles

Molecular insights into the binding mechanism of strontium and cesium on phyllosilicates with different expandability

The environmental fate of strontium (Sr) and cesium (Cs), as the critical radioactive fission products, have raised significant concerns regarding radioactive waste disposal and environmental protection. The current study investigated the distinction in the binding configurations of Sr2+ and Cs+ on various 2:1 phyllosilicate (illite, vermiculite, and montmorillonite) by combining batch adsorption, sequential extraction, and spectroscopic analyses. The results show that strontium adsorption is strongly influenced by pH as well as ionic strength, while there is no significant variability in strontium adsorption by different types of clay minerals. EXAFS analysis confirms the outer complexation of strontium on the planar sites of the clay minerals, i.e., Sr2+ is surrounded by ~8.0 O atoms, RSr-O ≈ 2.6 Å, and that process is mainly realized by ion exchange. In contrast, Cs+ adsorption was markedly influenced by the variety of clay minerals but less by pH and ionic strength, the presence of humic acid (HA) inhibited Cs+ adsorption. The inner-sphere complexation formed mainly at the frayed edge sites on illite, and interlayer sites on vermiculite and montmorillonite, was the dominant mechanism for Cs+ adsorption. In addition, the collapse of the interlayer space of vermiculite induced by Cs+ adsorption on the interlayer sites was responsible for the more stable and irreversible immobilization. The findings in present work highlighted the significance of prevailed mineral in governing environmental migration risk of radionuclides, the revealed adsorption mechanism and binding configuration of Sr2+ and Cs+ on typical phyllosilicates would be referable in constructing a reliable migration model of Sr2+ and Cs+ in natural media.

Removal of strontium by nanofiltration: Role of complexation and speciation of strontium with organic matter

Strontium (Sr) removal from water is required because excessive naturally occurring Sr exposure is hazardous to human health. Climate and seasonal changes cause water quality variations, in particular quality and quantity of organic matter (OM) and pH, and such variations affect Sr removal by nanofiltration (NF). The mechanisms for such variations are not clear and thus OM complexation and speciation require attention. Sr removal by NF was investigated with emphasis on the role of OM (type and concentration) and pH (2–12) on possible removal mechanisms, specifically size and/or charge exclusion as well as solute-solute interactions. The filtration results show that the addition of various OM (10 types) and an increase of OM concentration (2–100 mgC.L−1) increased Sr removal by 10-15%. The Sr-OM interaction was enhanced with increasing OM concentration, implying enhanced size exclusion via Sr-OM interaction as the main mechanism. Such interactions were quantified by asymmetric flow field-flow fractionation (FFFF) coupled with an inductively coupled plasma mass spectrometer (ICP-MS). Both extremely low and high pH increased Sr removal due to the enhanced charge exclusion and Sr-OM interactions. This work elucidated and verified the mechanism of OM and pH on Sr removal by NF membranes.

A stable 3D Sr-MOF as an efficient heterogeneous catalyst for the cycloadditions of CO2 and knoevenagel condensation reactions

The catalytic activity of MOF is determined not only by its unique structure but also by the active sites from metal sites and functional ligands. A sTable 3D strontium complex, {[Sr2(BTCB)Cl(H2O)2]}n (Sr-BTCB), was synthesized under solvothermal condition. It is assembled with an amide-functionalized tricarboxylic acid and a Sr(II)-based infinite chain, where Sr2 repeating units are arranged sequentially. Two such 3D structures are interwoven to create a two-folded interpenetrated structure. The interpenetrated structure is strengthened by π-π interstacking between the central phenyl rings of ligands from different 3D structures. After solvent exchange and vacuum drying, the surface of nanochannels in desolvated Sr-BTCB is modified by unsaturated Sr2+ions. Complex Sr-BTCB has abundant Lewis acidic metal sites and Lewis basic sites of amide groups, as well as 1D rhombic channels. It exhibits excellent stability and heterogeneous catalysis on CO2 fixation reactions into cyclic carbonates and Knoevenagel condensation reactions of aldehydes and malononitrile.

A series of neutral alkaline earth metal hydride complexes supported by a bulky, unsymmetrical β-diketiminate ligand, [{(Dip/TCHPNacnac)M(μ-H)}2] (M = Mg, Ca, Sr or Ba).

A bulky, unsymmetrical β-diketiminate ligand, [HC{MeCN(Dip)}{MeCN(TCHP)}]- (Dip/TCHPNacnac; Dip = 2,6-diisopropylphenyl, TCHP = 2,4,6-tricyclohexylphenyl), has been utilised in the preparation of a series of magnesium alkyl and calcium, strontium and barium amide complexes. Reaction of these with PhSiH3 afforded the first complete series of β-diketiminato heavier group 2 metal hydride complexes, [{(Dip/TCHPNacnac)M(μ-H)}2] (M = Mg, Ca, Sr or Ba). The unsymmetrical nature of the β-diketiminate ligand seemingly promotes stabilising interactions of ligand Dip groups with the metal centres in the Ca, Sr and Ba hydride complexes.

Sorption of Sr(II) ions with tricalcium phosphate in the presence of humic acids

The sorption behavior of traces Sr(II) toward β-Ca3(PO4)2 (TCP) depending on the concentration of the cation, pH, and concentrations of humic acids (HA) in the solution was udied. Thermodynamic analysis of the solubility of TCP (1) was performed taking into account the formation of Ca(OH)2 (CH, 2), Ca(H2PO4)2 (MCPA, 3), CaHPO4·2H2O (DCPD, 4), Ca5(PO4)3OH (hydroxyapatite, OHAp, 5), and Ca2P2O7 (DCPP, 6). It is shown that, depending on the pH of the solution, the main equilibrium phases with the solution are phases (4) and (5). X-ray di raction analysis, Raman spectroscopy, and 31P NMR data of the phase (1) samples after contact with a solution of 0.01 mol/L NaNO3 for about 10 days showed the presence of only the phase (1). The solubility of (1) regarding the concentration of Ca2+, PO43- ions and the stoichiometric ratio (Ca/P) in solutions, depending on pH, corresponds to the presence of surface phases (4) or (5). The model of surface complexation in the Henry region adequately describes the mechanism of sorption of Sr(II) by the surface phase (5) on TCP particles in the form of the SrHPO40 complex. The formation of the HA complex Sr(II) in solution does not a ect distribution coe cient K d(Sr) in the range of HA concentrations of 0-150 mg/L due to the competitive e ect of hydrogen phosphate ions on strontium complexes.

Protolytic and Complexing Properties of Isomeric N-(Pyridylethyl)taurines

New N-derivatives of taurine, N-[2-(2-pyridyl)ethyl]taurine (HL1) and N-[2-(4-pyridyl)ethyl]taurine (HL2) have been synthesized. Using the method of alkalimetric titration of aqueous solutions with pH potentiometric indication at I = 0.1 mol/L (KCl/KNO3) and T = 25 ± 1°C, the acid dissociation constants of functional groups in the composition of reagents have been determined (HL1: pKa0 = 3.80 ± 0.03, pKa1 = 8.67 ± 0.02, HL2: pKa0 = 4.80 ± 0.05, pKa1 = 8.18 ± 0.04). It has been found that reagent HL1 is more resistant to the degradation process. The complexation of transition and alkaline earth metal ions with НL1 has been studied. It has been shown that the introduction of a 2-(2-pyridyl)ethyl substituent into the structure of taurine leads to a significant increase in the stability (Δ log β ≥ 1) of copper(II), cobalt(II), nickel(II), zinc(II), cadmium(II) and silver(I) complexes with НL1. Calcium(II), magnesium(II), strontium(II), and barium(II) complexes with HL1 are characterized by a slight increase in stability (Δ lg β 1) compared to taurine. Based on the data obtained, the structure of the studied complexes have been assumed.

Zwitterions Functionalized by Optical Cycling Centers: Toward Laser-Coolable Polyatomic Molecular Cations.

Functionalization of large aromatic compounds and biomolecules with optical cycling centers (OCC) is of considerable interest for the design and engineering of molecules with a highly selective optical photoresponse. Both internal and external dynamics in such molecules can be precisely controlled by lasers, enabling their efficient cooling and opening up broad prospects for high-precision spectroscopy, ultracold chemistry, enantiomer separation, and various other fields. The way the OCC is bonded to a molecular ligand is crucial to the optical properties of the OCC, first of all, for the degree of closure of the optical cycling loop. Here we introduce a novel type of functionalized molecular cation where a positively charged OCC is bonded to various organic zwitterions with a particularly high permanent dipole moment. We consider strontium(I) complexes with betaine and other zwitterionic ligands and show the possibility of creating efficient and highly closed population cycling for dipole-allowed optical transitions in such complexes.

Do Phenyl Substituents Affect the Properties of Azobenzocrown Derivatives?

New products of photo- and thermal rearrangements of 19-membered azoxybenzocrown with phenyl substituents in benzene rings in the para positions to oligooxyethylene fragments are characterized. The yields of photochemical transformations depend on the solvent. Para-hydroxyazocrown is formed with yields over 50% in propan-2-ol. Ortho-hydroxyazobenzocrown is obtained with yields up to 70% in toluene/acetic acid mixture. Macrocyclic Ph-20-ester is obtained in yield 90% under thermochemical rearrangement conditions. Structure of new hydroxyazobenzocrowns and also atypical product of rearrangements, 20-membered ester, was confirmed by X-ray diffraction analysis. Azophenol⇄quinone-hydrazone tautomeric equilibrium of new hydroxyazobenzocrowns and the influence of metal cations on tautomeric equilibrium was investigated using 1H NMR and UV-Vis spectroscopy in acetonitrile. The highest value of stability constant (logK 7.25) was obtained for strontium complex of p-hydroxyazobenzocrown. For the first time p-hydroxyazobenzocrown was used as a chromoionophore in the receptor layer of an optical sensor. Comparative analysis with data obtained previously for series 19-membered analogs have shown the influence of the presence of substituents in benzene rings for the course and products distribution of photo- and thermal rearrangement. The effect of substituents was also discussed against the tautomeric equilibrium and metal cation complexation properties.

Complexation of some alkaline earth metals with bidentate uracil ligand: Synthesis, spectroscopic and antimicrobial analysis

ABSTRACT. Magnesium, calcium, strontium, and barium complexes of uracil were prepared in a 2:1 ligand to metal ratio to investigate the ligational character of the uracil (Ura). The modes of chelation were explained depending on elemental analyses, FT. IR, 1H–NMR spectra as well as scanning electron microscopy. Uracil has two donation sites either through N(3) and C(2)=O, or through N(3) and C(4)=O with the molecular formulas [M(Ura)2(H2O)2]Cl2 where M = Mg(II), Ca(II), Sr(II) and Ba(II) . The morphological surface and particle size of uracil metal complexes were determined using SEM and TEM. The thermal behaviors of the complexes were studied by the TGA (DTG) technique. The data obtained agreed well the proposed structures and showed that the complexes were finally decomposed to the corresponding metal oxide. The thermodynamic parameters are calculated from the thermal analysis curves using the Coats–Redfern and Horowitz–Metzger methods. The negative values of deduced the ordered structures of the prepared complexes compared to their starting reactants. Antibacterial activity of ligands and complexes is evaluated with two types of bacteria Staphylococcus aureus (gram‐positive) and Escherichia coli (gram‐negative) by the agar-well diffusion technique using DMSO as a solvent.
 
 KEY WORDS: Uracil, Coordination compounds, Non-isothermal kinetic parameters, Elemental analysis, Spectral studies, Biological efficiency
 Bull. Chem. Soc. Ethiop. 2023, 37(4), 945-957. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i4.11

Synthesis of Mononuclear Strontium Complexes with Polyether and β-Diketonato Ligands.

Strontium β-diketonate complexes were synthesized by the substitution reaction of the bis(trimethylsilyl) amide of Sr(btsa)2·2DME with an ethereal group and β-diketonate ligands. The compounds [Sr(tmge)(btsa)]2 (1), [Sr(tod)(btsa)]2 (2), Sr(tmgeH)(tfac)2 (3), Sr(tmgeH)(acac)2 (4), Sr(tmgeH)(tmhd)2 (5), Sr(todH)(tfac)2 (6), Sr(todH)(acac)2 (7), Sr(todH)(tmhd)2 (8), Sr(todH)(hfac)2 (9), Sr(dmts)(hfac)2 (10), [Sr(mee)(tmhd)2]2 (11), and Sr(dts)(hfac)2·DME (12) were obtained and analyzed by various techniques, including FT-IR, NMR, TGA (thermogravimetric analyses), and elemental analysis. Complexes 1, 3, 8, 9, 10, 11, and 12 were further structurally confirmed by single-crystal X-ray crystallography, where complexes 1 and 11 showed dimeric structures with μ2-O bonds of ethereal groups or tmhd ligands, and complexes 3, 8, 9, 10, and 12 displayed monomeric structures. Interestingly, compounds 10 and 12, which preceded trimethylsilylation of the coordinating ethereal alcohols such as tmhgeH and meeH in the presence of HMDS as by-products due to highly increasing acidity of them, originated from electron-withdrawing two hfac ligands.

Binding mechanism of strontium to biopolymer hydrogel composite materials

Strontium-90 is a radionuclide of concern that is mobile in soil and groundwater and is a threat to life. Activated hydrogel biopolymer composites were fabricated for strontium remediation from groundwater. Batch uptake demonstrated a maximal stontium uptake capacity of 109 mg g−1, much higher than unactivated hydrogel controls. Activation also more than doubled the decontamination factor at environmentally relevant concentrations. EXAFS was used to investigate the binding mechanism, revealing inner sphere complexation of strontium for the first time. Biopolymer composities synthesized for these studies are sustainable and cheap remediation materials that exhibit good strontium uptake and inner sphere binding.

Study on crystallographic structure and antiproliferative effect of mixed-ligand strontium(II) complex and N, Nˊ–bis(2-hydroxy-5-methylphenyl) pyridine-2,6-dicarboxamide ligand

The novel amide ligand, N,Nˊ–bis(2-hydroxy-5-methylphenyl) pyridine-2,6-dicarboxamide (L) was synthesized through the condensation reaction of pyridine-2,6-dicarbonylchloride with 2-amino-4-methylphenol (1:2). The new mixed-ligand complex [Sr(pydcH)2(H2O)3][Sr(pydcH2)(pydcH)(pydc)]2.[Sr(pydcH2)2(H2O)3].2H2O (C) (where pydc is pyridine-2,6-dicarboxylate) was prepared from the reaction of L with Sr(NO3)2·4H2O metal salt. The structures were characterized by single-crystal X-ray diffraction. A study on the antiproliferative effect of compounds was done by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay against two cancer cell lines including A375 (a human melanoma) and HT29 (a human colon adenocarcinoma), and also a normal HFF (a human foreskin fibroblast) cell line. A potent and selective cytotoxicity effect was exhibited for the complex toward A375 (IC50= 2.42 μM, MAE= 73.91%) cells. Further evaluations confirmed that ROS (Reactive oxygen species) level has increased by 307.7% in A375 cells following treatment with the complex compared to the control. Also, the decrease of MMP (Mitochondrial membrane potential) in the mentioned cell line was significant. Finally, the apoptotic cell death and the cell cycle arrest in the S-phase were recognized in A375 cells treated with the complex.

Synthesis and Characterization of New Strontium Complexes with Multidentate Ligands

AbstractA series of new strontium complexes, [Sr(tmtad)(btsa)]2 (1), [Sr(ptmtad)(btsa)]2 (2), [Sr(etmtad)(btsa)]2 (3), [Sr(tmtad)(tmhd)]2 (4), [Sr(ptmtad)(tmhd)]2 (5), and [Sr(etmtad)(tmhd)]2 (6), were successfully synthesized by substitution reactions between btsa, aminoalkoxide ligands, and tmhdH (btsa=bis(trimethylsilyl) amide, tmtadH=2,5,9,12‐tetramethyl‐2,5,9,12‐tetraazatridecan‐7‐ol, ptmtadH=2,5,7,9,12‐pentamethyl‐2,5,9,12‐tetraazatridecan‐7‐ol, etmtadH=7‐ethyl‐2,5,9,12‐tetramethyl‐2,5,9,12‐tetraazatridecan‐7‐ol, tmhdH=2,2,6,6‐tetramethyl‐3,5‐heptanedione). Thermogravimetric analysis (TGA) of the new strontium compounds showed low residual masses (4‐11 %) where complex 4 displayed the highest volatility and thermal stability. Single crystal X‐ray study of complexes 1, 3, and 6 revealed that the respective complexes crystalize in a triclinic space group as a dimer with a hexa‐ or hepta‐coordination. Furthermore, dimethylamino nitrogen atoms of aminoalkoxide ligands are freely pendent without coordinating to the central strontium metal due to their steric hindrance on the coordination sphere. Compounds 1–6 were characterized by 1H‐ and 13C‐nuclear magnetic resonance (NMR) spectroscopy, Fourier‐transform infrared (FT‐IR) spectroscopy, elemental analysis (EA), and thermogravimetric analysis.

Mechanisms of radiation defect formation in KCl crystals under the influence of local and plastic deformation

This work proposes an original approach to the study of trihalide centers in a KCl matrix in the field of local and plastic deformation. Local lattice deformation is carried out by purposeful doping of the KCl crystal with light homologous cations, as well as bivalent impurities, which create dipole strontium complexes to maintain the electroneutrality of the lattice. Plastic deformation, which creates paired vacancy defects in the lattice, divacancies and vacancy quartets, is realized at room temperature within the degree of relative uniaxial deformation of 3–5%. After subsequent cooling down to 80 K the deformed crystal was additionally irradiated with X-rays. The absorption spectra of the crystals subjected to two types of deformation and additional isodose irradiation by X-rays were recorded in a special cryostat at 80 K. The spectral characteristics and formation efficiency of V-type centers, lithium- and strontium-containing centers in the field of pre-irradiation dipole complexes have been considered.

Synthesis and Oligonuclear Structures of Strontium and Barium Complexes with Protonated and Deprotonated N-Mesityl-P,P-diphenylphosphinic Amide Ligands.

Metalation of N-mesityl-P,P-diphenylphosphinic amide Ph2P(O)-NHMes (HL, I) with MgBu2 and Ae{N(SiMe3)2}2 (Ae = Ca, Sr, and Ba) yields alkaline-earth metal complexes with the compositions of [(thf)nAe(L·HL)2] [Ae/n = Mg/0 (II), Ca/2 (III)] as well as of [Sr2L3(L·HL)(HL)] (1), [Ba2L3(L·HL)(HL)] (2), [Ba3L6] (3), and [(thf)2Ba3L6] (4). In III, 1, 2, and 3, the alkaline-earth metal atoms are in severely distorted octahedral environments, and the structural distortions are partially caused by the small O-Ae-N bite angles of the chelating Ph2P(O)-NMes anions. The substructures (L·HL) contain N–H···N hydrogen bridges, stabilizing the arrangement of the ligands in complexes II, III, 1, and 2. In the trinuclear barium complex [Ba(μ-L)3Ba(μ-L)3Ba] (3), a rigid adjustment of the anionic L bases leads to a C3-symmetric molecule in the crystalline state with bridging oxygen atoms. Due to the small O–Ba–N bite angles of the chelating anions, vacant coordination sites are available at the outer barium centers. Coordination of thf bases in these gaps yields the complex [(thf)Ba(μ-L)3Ba(μ-L)3Ba(thf)] (4). However, THF is unable to deaggregate the trinuclear complexes into smaller barium-containing moieties. Increasing the radius of the alkaline-earth metals and increasing the nuclearity of these compounds lead to decreasing solubility in common organic solvents. NMR studies verify that the molecular structures of these alkaline-earth metal complexes are maintained in ethereal solvents and toluene.

Synthesis and Crystal Structures of New Strontium Complexes with Aminoalkoxy and β-Diketonato Ligands

New heteroleptic strontium complexes were synthesized using substitution reaction of bis(trimethylsilyl)amide of Sr(btsa)2·2DME with aminoalkoxide and β-diketonate ligands. The complexes [Sr(bdmp)(btsa)]2·2THF (1), [Sr(bdeamp)(btsa)]2 (2), [Sr(dadamb)(btsa)]2 (3), [Sr(bdmp)(hfac)]3 (4), [Sr(bdeamp)(hfac)]3 (5), [Sr(dadamb)(hfac)]3 (6), and [Sr3(dadamb)4(tmhd)2] (7) were prepared and characterized by means of various analysis techniques such as Fourier transform infrared, NMR, thermogravimetric analysis, and elemental analysis. Complexes 1–3 were further structurally confirmed by single-crystal X-ray crystallography, and they displayed dimeric structures in which strontium atoms were connected by alkoxide oxygen atoms of the μ2 type. Compound 1 has a trigonal prismatic structure, whereas 2 and 3 have a distorted square pyramidal structure. In complexes 5–7, trimeric structures were obtained with strontium atoms connected by μ3–O bonds of alkoxide oxygen atoms and μ2–O bonds of alkoxide and β-diketonate oxygen atoms. The crystal structures of 5, 6, and 7 showed distorted capped octahedral geometry, while 7 (middle Sr atom) displayed a distorted trigonal prism geometry. Complexes 5–7 displayed ∼70% mass loss in the temperature range from 25 to 315 °C.

Metal-Organic Frameworks Derived from Calcium and Strontium Complexes of a Redox-Active Ligand.

The reactions of monomeric [(dpp-Bian)M(thf)4] (M = Ca (1a), Sr (1b); dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with 4,4'-bipyridyl (4,4'-bipy) proceed with electron transfer from dpp-Bian2- to 4,4'-bipy0 to afford calcium and strontium complexes containing simultaneously radical-anionic dpp-Bian- and 4,4'-bipy- ligands. In tetrahydrofuran (thf) the reactions result in 1D coordination polymers [{(dpp-Bian)M(4,4'-bipy)(thf)2}·4thf]n (M = Ca (2a), Sr (2b)), while in a thf/benzene mixture the reaction between 1a and 4,4'-bipy affords the 2D metal-organic framework [{(dpp-Bian)Ca(4,4'-bipy)2}·2thf·2C6H6]n (3). The structures of compounds 2a,b and 3 have been determined by single-crystal X-ray analyses. The presence of the ligand-localized unpaired electrons allows the use of ESR spectroscopy for characterization of the compounds 2a,b and 3. DFT calculations of model calcium complexes with the dpp-Bian, 4,4'-bipy, and thf ligands confirm the energetically favorable open-shell configurations of the molecules bearing the 4,4'-bipy fragments. The magnetic susceptibility measurements confirm the presence of two unpaired electrons per monomeric unit in 2a,b and 3. The thermal stability of compounds 2a,b and 3 was studied by thermogravimetric analysis (TGA). To the best of our knowledge, 3 is the first MOF simultaneously containing two different paramagnetic bridging ligands inside the framework.

Approaching a “Naked” Boryl Anion: Amide Metathesis as a Route to Calcium, Strontium, and Potassium Boryl Complexes

AbstractAmide metathesis has been used to generate the first structurally characterized boryl complexes of calcium and strontium, {(Me3Si)2N}M{B(NDippCH)2}(thf)n(M=Ca,n=2; M=Sr,n=3), through the reactions of the corresponding bis(amides), M{N(SiMe3)2}2(thf)2, with (thf)2Li‐ {B(NDippCH)2}. Most notably, this approach can also be applied to the analogous potassium amide K{N(SiMe3)2}, leading to the formation of the solvent‐free borylpotassium dimer [K{B(NDippCH)2}]2, which is stable in the solid state at room temperature for extended periods (48 h). A dimeric structure has been determined crystallographically in which the K+cations interact weakly with both the ipso‐carbons of the flanking Dipp groups and the boron centres of the diazaborolyl heterocycles, with K⋅⋅⋅B distances of >3.1 Å. These structural features, together with atoms in molecules (QTAIM) calculations imply that the boron‐containing fragment closely approaches a limiting description as a “free” boryl anion in the condensed phase.

Approaching a "Naked" Boryl Anion: Amide Metathesis as a Route to Calcium, Strontium, and Potassium Boryl Complexes.

Amide metathesis has been used to generate the first structurally characterized boryl complexes of calcium and strontium, {(Me3Si)2N}M{B(NDippCH)2}(thf)n (M=Ca, n=2; M=Sr, n=3), through the reactions of the corresponding bis(amides), M{N(SiMe3)2}2(thf)2, with (thf)2Li‐ {B(NDippCH)2}. Most notably, this approach can also be applied to the analogous potassium amide K{N(SiMe3)2}, leading to the formation of the solvent‐free borylpotassium dimer [K{B(NDippCH)2}]2, which is stable in the solid state at room temperature for extended periods (48 h). A dimeric structure has been determined crystallographically in which the K+ cations interact weakly with both the ipso‐carbons of the flanking Dipp groups and the boron centres of the diazaborolyl heterocycles, with K⋅⋅⋅B distances of >3.1 Å. These structural features, together with atoms in molecules (QTAIM) calculations imply that the boron‐containing fragment closely approaches a limiting description as a “free” boryl anion in the condensed phase.

Synthesis, spectroscopic, structural and morphological characterizations of magnesium(II), calcium(II), strontium(II) and barium(II) folate complexes

This article aimed to synthesis and characterizations of metal folic acid as a vitamin B9 drug (H2FO) complexes. Using this bi-dentate ligand, complexes of magnesium(II), calcium(II), strontium(II) and barium(II) with general formula [M2(FO)(H2O)6(Cl)2].2H2O have been synthesized. The synthesized folate complexes were characterized by number of techniques using elemental analysis, molar conductance, (FTIR, Raman laser, 1HNMR & electronic) spectroscopy and particle size analysis using X-ray powder diffraction (XRD) spectra. The elemental analysis results suggest the stoichiometry to be 2 : 1 (M : L). All the synthesized complexes are non-electrolytic nature as confirmed by molar conductance measurements. Infrared spectral data indicate the coordination between the folate ligand and the central metal ion via the folate anion which acts as a dicarboxylate ligand with the metal ion coordinated to both the α and β carboxylate groups of the glutamic acid moiety. Spectral studies suggest six-coordination geometry for all complexes.