Metal-ligand Stoichiometry Research Articles

Experimental and theoretical insight into biphasic extractive mass transfer of thorium into ionic liquid phase using chloroamide ligands

2-chloro-N-methyl-N-phenylacetamide (L1) and 2-chloro-N-(3-methylpyridin-2-yl)acetamide (L2) have been explored for the efficient separation of tetravalent thorium ion (Th4+) from aqueous phase to the ionic liquid phase. Due to the positive inductive effect (+I effect) of alkyl group, the electron density on N in L1 was more compared to that in L2; as evidenced from the distribution ratio values of Th4+ (DThL1 ∼ 180 and DThL2 ∼ 107 at 1 M HNO3). The extraction proceeds via 'cation exchange' mechanism involving 1:3 metal ligand stoichiometry for both the ligands. Each thorium complex was associated with three nitrate ions; thus, making the complex uni-positive in nature. The charge compensation during extractive mass transfer was done by dissolution of one hexyl methylimidazolium cation from ionic liquid phase to aqueous phase. The mass transfer followed slower kinetics, which was attributed to the high viscosity coefficient of ionic liquid. The extraction processes were spontaneous (ΔGL1300K ∼ −16.31 kJ mol−1 and ΔGL2300K ∼ −15.75 kJ mol−1) and endothermic in nature with a significant enhancement in the entropy (ΔSL1300K ∼ 107.98 kJ mol- 1K−1 and ΔSL2300K ∼ 103.54 kJ mol-1K−1). Density functional theory (DFT) calculation revealed the presence of two types of Th-O bond associated with nitrate ion and ligands (Th-OnitrateL1 ∼ 2.511A˚, Th-OligandL1 ∼ 2.411A˚, Th-OnitrateL2 ∼ 2.518A˚ and Th-OligandL2 ∼ 2.422A˚. The higher extraction efficiency of Th4+ for L1 was corroborated from the negative ΔG values calculated for L1 in gas and ionic liquid phase compared to that for L2.

Assembly of a Heterometallic Cu(II)-Pd(II) Cage by Post-assembly Metal Insertion.

Porous structures based on multi-metallic motifs are receiving growing interest, but their general preparation still remains a challenge. Here, we report the self-assembly and structure of a CuII metal-organic cage (MOC) that is functionalized with free bis(pyrazolyl)methane sites. The homometallic Cu4L4 cage is isolated as a water-stable crystalline solid, and its formation is dependent on metal-ligand stoichiometry and the pre-organization of the Cu2 paddlewheel. We show by X-ray diffraction and SEM-EDX that PdII chloride can be quantitatively inserted into the free chelating sites of the MOC to yield a [Cu4(L(PdCl2))4] structure. Moreover, the solvent employed in the metalation dictates the solid-state isomerism of the heterometallic cage─a further handle to control the MOC's structural diversity and permanent porosity.

IN VITRO ANTICANCER, ANTIOXIDANT AND MOLECULAR DOCKING STUDIES OF 4-AMINOBENZAMIDE METAL COMPLEXES

Objective: Mixed ligand complexes of Cu(II) and Cd(II) with 4-aminobenzamide(4-ABZ) have been synthesized under microwave irradiation and they were characterized by elemental analysis, estimation of metal ion, molar conductivity, magnetic study, FT-IR, Far-IR, electronic spectra, NMR (1H and 13C) and EPR spectral studies. Methods: The data of microanalysis and metal estimation showed that the complexes have the composition of [M(L1)2(L2)2] for Cu(II) and [M(L1)(L2)2] for Cd(II) complex respectively. The conductivity data confirmed the neutral nature of the complexes. The tetrahedral geometry of the Cd(II) complex was confirmed using UV-Visible spectra. The tetragonally distorted octahedral stereochemistry of Cu(II) complex was further confirmed by UV and EPR spectral studies. The diamagnetic nature and probable geometry of Cd(II) complex were also confirmed using NMR spectral studies, which are also compared with free 4-aminobenzamide. The in vitro bio-potential activities of 4-ABA and Cd(II) complex were screened for E. coli and C. Albicans microorganisms by Agar disc diffusion methods. Results: The cancer study of Cu(II) complex and antioxidant activity of DPPH free radical scavenging method of Cd(II) complex were measured and compared with 4-aminobenzamide and standard drugs. The breast cancer studies were also identified using the targeted proteins viz., BRCA1, PR and EGFR by molecular docking study. Conclusion: In the present study, we synthesized new metal complexes of Cu(II) and Cd(II) with 4-ABA and nitrite ion by microwave irradiation method. The analytical data show that the metal-ligand stoichiometry they are non-electrolytes in acetonitrile solution. The spectral data show that the synthesized ligand binds with metal ions through the nitrogen atom of the 4-ABA and oxygen atoms of the nitrite ion.

Stretchable Self-Healing Plastic Polyurethane with Super-High Modulus by Local Phase-Lock Strategy.

In this work, a multiblock polyurethane (PU-Im) consisting of polyether and polyurethane segments with imidazole dangling groups is demonstrated, which can further coordinate with Ni2+ . By controlling the ligand content and metal-ligand stoichiometry ratio, PU-Im-Ni complex with vastly different mechanical behavior can be obtained. The elastomer PU-2Im-Ni has extraordinary mechanical strength (61MPa)andexcellenttoughness(420 MJ m-3 ), but the plastic PU-4Im-Ni exhibits super-high modulus (515 MPa),strength(63 MPa),andgoodstretchability(≈800%). The metal-ligand interaction between polyurethane segments and Ni2+ is proved by Raman spectra, dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). The polyurethane segments domain formed by microphase separation is dynamically "locked" by Ni2+ coordinated with imidazole, revealing a local phase-lock effect. The phase-locking hard domains reinforce the PU-Im-Ni complex and maintain stimuli-responsive self-healing ability, while the free polyether segments provide stretchability. Primarily, the water environment with plasticization effect serves as an effective and eco-friendly self-healing approach for PU-Im-Ni plastic. With the excellent mechanical performance, thermal/aquatic self-healing ability, and unique damping properties, the PU-Im-Ni complexes show potential applications in self-healing engineering plastic and cushion protection fields.

Synthesis and characterization of 2,5-dibutylthio-2,3-dihydro-2-formyl-4H-pyran thiosemicarbazones and their copper complexes

Previously unknown derivatives of thiosemicarbazide were obtained in high yields by the condensation reaction of 2,5-dibutylthio-2,3-dihydro-2-formyl-4H-pyran with 4-phenylthiosemicarbazide or thiosemicarbazide when boiling in EtOH. The reaction products are represented by colored oils. Cu(II) complexes based on 2,5-dibutylthio-2,3-dihydro-2-formyl-4H-pyran carbazones were synthesized by their interaction with copper (II) chloride. All these complexes are soluble in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) and, according to elemental analysis, have a 1:1 metal-ligand stoichiometry. The obtained compounds were studied using IR and 1H, 13C, 15N NMR spectroscopy, as well as elemental analysis. The obtained copper-containing complexes with thiosemicarbazones are of particular interest due to their pronounced biological activity. The thiosemicarbazone 2,5-dibutylthio-2,3-dihydro-2-formyl-4H-pyran compound was subjected to primary screening for acute toxicity. The obtained results showed that, when taken intragastricaly, the studied compound can be characterized as a substance with a low risk of acute toxicity. According to the DL50 parameter, the compound belongs to the V hazard class (DL50>2000 mg/kg).

Alkyl-Substituted Aminobis(phosphonates)-Efficient Precipitating Agents for Rare Earth Elements, Thorium, and Uranium in Aqueous Solutions.

The efficient and environmentally sustainable separation process for rare earth elements (REE), especially for adjacent lanthanoids, remains a challenge due to the chemical similarity of REEs. Tetravalent actinoids, thorium, and traces of uranium are also present in concentrates of REEs, making their separation relevant. This study reports six simple water-soluble aminobis(phosphonate) ligands, RN[CH2P(O)(OH)2]2 (1 R = CH2CH3, 2 R = (CH2)2CH3, 3 R = (CH2)3CH3, 4 R = (CH2)4CH3, 5 R = (CH2)5CH3, 6 R = CH2CH(C2H5)(CH2)3CH3) as precipitating agents for REEs, Th, and U, as well as gives insight into the coordination modes of the utilized ligands with REEs at the molecular level. Aminobis(phosphonates) 4–6 with longer carbon chains were found to separate selectively thorium, uranium, and scandium from REEs with short precipitation time (15 min) and excellent separation factors that generally range from 100 to 2000 in acidic aqueous solution. Ligands 1–6 also improved separation factors for adjacent lanthanoids in comparison to traditional oxalate precipitation agents. Importantly, precipitated metals can be recovered from the ligands with 3 molar HNO3 with no observed ligand decomposition enabling the possibility of recycling the ligands in the separation process. NMR-monitored pH titrations for 1 showed deprotonation steps at pKa 1.3, 5.55, and >10.5, which indicate that the ligands remain in a deprotonated [L]−1 form in the pH range of 0–4 used in the precipitation studies. 31P NMR titration studies between 1 and M(NO3)3 (M = Y, La, Lu) gave satisfactory fits for 1:3, 1:2, and 1:1 metal–ligand stoichiometries for Y, La, and Lu, respectively, according to an F-test. Therefore, aminobis(phosphonate) precipitation agents 1–6 are likely to form metal complexes with fewer ligands than traditional separation agents like DEHPA, which coordinates to REEs in 1:6 metal–ligand ratio.

Copper (II) complexes with novel Schiff-based ligands: synthesis, crystal structure, thermal (TGA–DSC/FT-IR), spectroscopic (FT-IR, UV-Vis) and theoretical studies

This study aimed to synthesize two novel Schiff-base ligands through the condensation between N-(2-aminoethyl)pyrazoles and 2-hydroxy-1-naphthaldehyde, which are: NaphPz ((E)-1-(((2-(1H-pyrazol-1-yl)ethyl)imino)methyl)naphthalen-2-ol)) and NaphDPz ((E)-1-(((2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)imino)methyl)naphthalen-2-ol). These novel pyrazole-imines were synthesized, characterized and used as copper (II) ion complexing agents. Different synthetic routes have been adapted to obtain the [Cu(NaphPz)Cl], [Cu(NaphDPz)Cl] and [Cu(NaphPz)2] complexes in the solid state, the first two in the crystalline form and the latter as a powder. The minimum metal–ligand stoichiometry for the three complexes was defined by TGA–DSC thermoanalytical data and by single-crystal X-ray diffraction for the crystalline samples which belong to the P21/n space group. The products of the thermal decomposition of the material were also monitored by TGA–DSC/FT-IR in air and N2 atmospheres in order to suggest how thermal decomposition of the organic portion of the complex occurs. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations compared to experimental results (UV-Vis and FT-IR) show a high degree of correlation. From HOMO/LUMO orbitals, the main major charge distributions, responsible for the absorption bands of the complexes, were determined.

Ex-vivo Antimalarial and in-vitro Biological Activities of newly synthesized Co(II) complex with Schiff base

Abstract The first-row transition metal complex of Schiff base has been synthesized and characterized based on physicochemical spectral and biochemical methods. The metal-ligand stoichiometry and molecular formula of the complex assessed by Elemental analysis and metal estimation-neutral, monomeric nature of the complex and paramagnetic nature also predict by the conductance and magnetic moment study. The octahedral environment around Co(II) and metal-imine bond as a whole predicted by atomic IR and Far-IR spectra. In-vitro antibacterial and antifungal activities of the Schiff base and its complexes compared with those for standard (Chloramphenicol & Fluconazole) by agar disc diffusion method. The Ex-vivo antimalarial activity of the Schiff base and its metal complex was found by using Plasmodium falciparum bacteria/fungal.

New Co(II) and Cu(II) complexes derived from an imidazolium ionic liquid-based Schiff base : Synthesis, Physico chemical characterization and exploration of Antibacterial activities

Two new Co(II) and Cu(II) complexes from an imidazolium ionic liquid based Schiff base 1-{2-(2-hydroxy-5-nitrobenzylideneamino)ethyl}-3-ethylimidazolium tetrafluoro -borate were synthesized and characterized by different analytical and spectroscopic techniques such as elemental analysis (CHN analysis), UV-Visible, 1 H-NMR, FT-IR, Mass-spectra, Powder X-ray diffraction analysis, magnetic susceptibility measurements and molar conductance data. From these analytical results, tetra coordinated 1:2 metal-ligand stoichiometry was suggested for the both complexes. The molar conductance data of the complexes revealed their electrolytic nature (1:2). The synthesized complexes along with the ligand were screened for in vitro antibacterial applications against gram negative and gram positive bacteria to assess their inhibition potentials. The complexes were proved very effective against the tested organisms.

Determination of Anticancer Zn(II)-Rutin Complex Structures in Solution through Density Functional Theory Calculations of 1H NMR and UV-VIS Spectra.

Coordination compounds formed by flavonoid ligands are recognized as promising candidates as novel drugs with enhanced antioxidant and anticancer activity. Zn(II)–Rutin complexes have been described in the literature and distinct coordination modes proposed based on 1H NMR/MS and IR/UV–VIS experimental spectroscopic data: 1:1/1:2 (Zn(II) binding to A-C rings) and 2:1 (Zn(II) binding to A-C-B rings) stoichiometry. Aiming to clarify these experimental findings and provide some physical insights into the process of complex formation in solution, we carried out density functional theory calculations of NMR and UV–VIS spectra for 25 plausible Zn(II)–Rutin molecular structures including solvent effect using the polarizable continuum model approach. The studied complexes in this work have 1:1, 1:2, 2:1, and 3:1 metal–ligand stoichiometry for all relevant Zn(II)–Rutin configurations. The least deviation between theoretical and experimental spectroscopic data was used as an initial criterion to select the probable candidate structures. Our theoretical spectroscopic results strongly indicate that the experimentally suggested modes of coordination (1:2 and 2:1) are likely to exist in solution, supporting the two distinct experimental findings in DMSO and methanol solution, which may be seen as an interesting result. Our predicted 1:2 and 2:1 metal complexes are in agreement with the experimental stoichiometry; however, they differ from the proposed structure. Besides the prediction of the coordination site and molecular structure in solution, an important contribution of this work is the determination of the OH–C5 deprotonation state of rutin due to metal complexation at the experimental conditions (pH = 6.7 and 7.20). We found that, in the two independent synthesis of metal complexes, distinct forms of rutin (OH–C5 and O(−)–C5) are present, which are rather difficult to be assessed experimentally.

Ruthenium hydrazone complexes with 1:1 and 1:2 metal–ligand stoichiometry: a comparison of biomolecular interactions and in vitro cytotoxicities

Two ruthenium(II) complexes [RuIICl(PPh3)2(L)] (1) and [RuII(L)2] (2) were synthesized by reacting [RuCl2(PPh3)3] and thiophene-2-carboxylic acid (1-pyridine-2-yl-ethylidene)-hydrazide (HL) in methanol–chloroform, and characterized by elemental analysis and spectral and XRD data. The ratio of ligand to metal is 1:1 in the former complex and 2:1 in the latter. Interaction of these complexes with CT-DNA was studied using absorption and emission spectral studies; these show that both the complexes interact with CT-DNA through intercalative modes of interaction. Their BSA-binding activity results indicated the operation of static quenching mechanism and stronger binding of tryptophan residues than tyrosine residues. In vitro cytotoxicity assays against HeLa and MCF-7 cell lines showed better activity of both the complexes compared to the standard drug cisplatin. Overall, the activity of complex 2 with two units of coordinated ligand showed better activity than the other one.

Unfolding the complexation and extraction of Am3+ and Eu3+ using N-heterocyclic aromatic diphosphonic acids: a combined experimental and DFT study.

Phosphonate based ligands are well known for the extraction of 'f' block elements. Three N,O-donor N-heterocyclic aromatic diphosphonate ligands were evaluated in the present work for the extraction/separation studies of Am3+ and Eu3+. Complexation studies in aqueous medium using luminescence titration indicated the formation of anionic complexes in the case of Eu3+. Two phase liquid-liquid extraction studies were, therefore, carried out by employing Aliquat-336 as the liquid anion exchanger. The results indicated the formation of a species with a metal-ligand stoichiometry of 1 : 3 in the case of pyridine-2,6-diphosphonic acid (PyPOH). In the case of 2,2'-bipyridine-6,6'-diphosphonic acid (BipyPOH), however, a 1 : 2 complex was extracted and 1,10-phenanthroline-2,9-diphosphonic acid (PhenPOH) extracts the Am3+ and Eu3+ ions by forming both 1 : 2 and 1 : 3 complexes. Formation of these kinds of anionic complexes was further confirmed using electrospray ionization mass spectrometry (ESI-MS). DFT calculations predicted the structure of the anionic complexes. The non-selectivity of these kinds of ligands between Am3+ and Eu3+ was attributed to the presence of unfavorable covalent interactions in the metal-ligand bonds.

Impact of Chloride Concentration on Ligand Substitution Reactions of Zinc(II) Complexes with Biologically Relevant Nitrogen Nucleophiles

The mole-ratio method was used to determine the metal–ligand stoichiometry between [ZnCl2(en)] and [ZnCl2(terpy)] (where en = 1,2-diaminoethane or ethylenediamine and terpy = 2,2′:6′,2″-terpyridine) and imidazole at pH 7.2 in the presence of different chloride concentrations. The results indicated step-wise formation of 1:1 and 1:2 complexes in the presence of 0.010 M NaCl and 1:1 complexes in the presence of 0.001 M NaCl for the [ZnCl2(en)] complex. These results are correlated with additional coordination of chlorides in the first coordination sphere and with changes in coordination geometry. In the presence of 0.001 M NaCl the five-coordinate complex anion [ZnCl3(en)]- is formed initially and then a substitution reaction with imidazole occurs. In the presence of 0.010 M NaCl the octahedral complex anion [ZnCl4(en)]2- is formed. Additional coordination of chloride in the [ZnCl2(terpy)] complex is not found and the metal–ligand stoichiometry is 1:2. The kinetics of ligand substitution reactions of zinc(II) complexes and biologically relevant nitrogen nucleophiles such as imidazole, 1,2,3-triazole and L-histidine were investigated at pH 7.2 as a function of nucleophile concentration in the presence of 0.001 M and 0.010 M NaCl. The reactions were followed under pseudo first-order conditions by UV-Vis spectrophotometry. The substitution reactions included two steps of consecutive displacement of chlorido ligands with changes only in the coordination geometry of the [ZnCl2(en)] complex. The order of reactivity of the investigated nucleophiles for the first reaction step towards both complexes was L-histidine > 1,2,3-triazole > imidazole, while in the presence of 0.010 M NaCl the most reactive ligand was 1,2,3-triazole towards the [ZnCl2(en)] complex.

Kinetic Studies of the Reactions between Dichlorido(1,2-Diaminoethane)Zinc(II) and Biologically Relevant Nucleophiles in the Presence of Chloride

The mole-ratio method was used for determining metal–ligand stoichiometry for the reaction between [ZnCl2(en)] (where en = 1,2-diaminoethane or ethylenediamine) and chloride ion at pH 7.2. The results have shown step-wise formation of 1:1 and 1:2 complexes and indicate additional coordination of chloride ions in the first coordination sphere. The kinetics of ligand substitution reactions of the zinc(II) complex and biologically relevant nucleophiles such as inosine-5′-monophosphate (5′-IMP), guanosine-5′-monophosphate (5′-GMP), L-methionine (L-Met), glutathione (GSH) and DL-aspartic acid (DL-Asp) were investigated at pH 7.2 as a function of nucleophile concentration in the presence of 0.010 M NaCl. The reactions were followed under pseudo first-order conditions by UV-Vis spectrophotometry. The substitution reactions include two steps of consecutive displacement of chlorido ligands and changes in coordination geometry. In the presence of an excess of chloride, the octahedral complex anion [ZnCl4(en)]2- formed. The first step of the substitution reactions could be interpreted as substitution of the axial chlorido ligands in the cis position to bidentate ethylenediamine by the biologically relevant nucleophiles, while the second step could be interpreted as substitution of the equatorial chlorido ligand. The order of reactivity of the investigated nucleophiles for the first reaction step is 5′-IMP > GSH > L-Met > DL-Asp > 5′-GMP, while for the second reaction step the order of reactivity is GSH > L-Met > 5′-IMP > DL-Asp > 5′-GMP.

Electrical Conductivity, Electronic Absorption, IR and NMR Studies On Cr(III), Sn(IV) and Pb(IV) Complexes of an Azo Ligand derived from Isatin and 4-Aminoantipyrine.

The electrical conductivity, electronic absorption, IR and NMR spectroscopy of an azo ligand synthesized by coupling IH-indole-2,3-dione(isatin) with diazotized I-phenyl-2,3-dimethyl-4-aminopyrazole-5-one (4-aminoantipyrine) have been studied. The ligand: 6-[(E)-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-lH-pyrazole-4-yl)diazenyl]-lH-indole-2,3-dione(DPDD), forms stable complexes with metal ions, such as Cr(III), Sn(IV) and Pb(IV). These complexes have potential application in pharmacology. Their structures were investigated by UV and IR spectroscopy. Analytical data on the composition of the complexes show that Cr(IV) and Sn(IV) formed complexes with 2:l metal-ligand mole ratio, whereas complexation with Pb(IV) followed 2:1 metal-ligand stoichiometry. Keywords : Azoligand; DPDD; metal complexes; 4-aminoantipyrine; isatin; Cr(III); Sn (IV); Pb(IV).

Electro-Fenton degradation of antibiotic ciprofloxacin (CIP): Formation of Fe3+-CIP chelate and its effect on catalytic behavior of Fe2+/Fe3+ and CIP mineralization

This work investigated the effect of the chelation of Fe3+ with a fluoroquinolone (FQ) antibiotic ciprofloxacin (CIP) on the catalytic behavior of Fe3+/Fe2+ and the degradation and mineralization of CIP in electro-Fenton (EF) process using activated carbon fiber (ACF) felt cathode. First of all, effect of initial Fe2+ and Fe3+ concentrations on the degradation and mineralization of CIP in EF process was compared, while the optimal initial Fe2+ and Fe3+ contents were both verified to be 1.50mmoldm−3, in which 73% and 72% of initial TOC were eliminated after 360min electrolysis, respectively. Secondly, Fe3+-CIP chelate was produced during CIP degradation in EF process, whose predominant form was confirmed as 1:2 metal-ligand stoichiometry. The formation of Fe3+-CIP chelate had no obvious inhibition on the degradation and mineralization of CIP due to the efficient Fe3+ reduction on the ACF cathode with excellent catalytic feature. About 17% and 35% of initial 1.50mmoldm−3 Fe3+ were reduced to Fe2+ at 18mAcm−2 in ultrapure water and 200mgdm−3 CIP solutions during 30min pre-aeration of EF process, respectively, while higher Fe2+ concentration was maintained for initial 1.50mmoldm−3 Fe3+ during CIP degradation. Finally, the evolution of F−, NH4+ and NO3− ions released to the acidic medium were determined, as well as the formation of short-chain carboxylic acid (oxalic, oxamic and formic acids). Eight aromatic intermediates were identified using UPLC-QTOF-MS/MS, and a feasible mineralization pathway was proposed.

An Insight into the Complexation of Trivalent Americium Vis‐à‐Vis Lanthanides with Bis(1,2,4‐triazinyl)bipyridine Derivatives

Complexation of Am3+ and Ln3+ (La3+, Eu3+, and Er3+) with two bis(1,2,4‐triazinyl)bipyridine (C2BTBP, C5BTBP) derivatives has been studied in acetonitrile medium with use of various experimental techniques such as electrospray ionization mass spectrometry (ESI‐MS), time‐resolved fluorescence spectroscopy (TRFS), UV/Vis spectrophotometry, and solution calorimetry. Metal–ligand stoichiometries and conditional stability constants of these complexes were determined. To the best of our knowledge, this is the first report on the complexation of Am3+ with any of the BTBP derivatives with use of UV/Vis spectrophotometric titration to determine the conditional stability constants. Density functional theory (DFT) calculations are carried out on the An3+ (U3+ and Am3+) and Ln3+ (La3+, Nd3+, Eu3+, Er3+, and Lu3+) complexes of BTBP in order to understand the difference between the bonding in actinide and lanthanide complexes. The results indicate a stronger covalent interaction in the An–N bonds as compared to the Ln–N bonds, which leads to an actinide selectivity of this class of ligands.

Effect of phase modifiers TBP and iso-decanol on the extraction and complexation of Eu3+ with CMPO

ABSTRACTThe effect of tri-n-butyl phosphate (TBP) and iso-decanol as phase modifiers on the complexation of Eu3+ with octyl-phenyl N,N-diisobutyl carbamoyl methyl phosphine oxide (CMPO) was studied. On an increase of iso-decanol the extraction efficiency of Eu3+ decreases. The metal–ligand stoichiometry was found to be 1:3. The Eu complex of CMPO–TBP was more symmetric compared to CMPO–iso-decanol. The Eu3+ complex exhibited D3h and C3h symmetry for 30% and 5% iso-decanol, while that for TBP was C6v. The radiative, non-radiative life time, electric and magnetic dipole transition probabilities, branching ratio, quantum efficiency etc. were evaluated. The covalency between Eu3+ and CMPO is as follows: CMPO–TBP < CMPO-5% iso-decanol < CMPO-30% iso-decanol.

Understanding the complexation of the Eu3+ ion with TODGA, CMPO, TOPO and DMDBTDMA: Extraction, luminescence and theoretical investigation

A comparative study was carried out to understand the complexation behavior of the Eu3+ ion with important reagents, namely TODGA (N,N,N′,N′ tetraoctyl diglycolamide), CMPO (octyl (phenyl)-N, N-diisobutyl carbamoyl methyl phosphine oxide), DMDBTDMA (dimethyl dibutyl tetradecyl malonamide) and TOPO (tri-n-octyl phosphine oxide) in dodecane, used for the separation of actinides and lanthanides from lab and nuclear high-level wastes, by experimental (extraction and luminescent) and theoretical means. A solvent extraction study revealed the metal–ligand stoichiometry as 1:3 for all the systems with the extraction efficiency TOPO>CMPO>TODGA>DMDBTDMA at 1M HNO3, while TODGA>CMPO>DMDBTDMA>TOPO at 3M HNO3. A luminescence investigation revealed the presence of single species in the extracted complex for all the systems, with no inner sphere water molecules for all the systems except for DMDBTDMA which had one inner sphere water molecule. The high intensity of the 5D0–7F2 transition revealed the presence of Eu3+ ions in an asymmetric environment with the local point group symmetry C3v for the TODGA and DMDBTDMA complexes, compared to C3h symmetry for the CMPO and TOPO complexes. Judd–Offelt parameters, radiative, non-radiative lifetimes, branching ratio, transition probabilities and quantum efficiencies for all the complexes were estimated and compared. Three O-donor atoms from each TODGA molecule coordinated to the Eu3+ ion in the first coordination sphere, while three CMPO units were found to be coordinated in a monodentate fashion. For the Eu-TOPO complex, three O donor atoms from each of the three TOPO molecules and six O donor atoms from three nitrate ions were coordinated. Out of three DMDBTDMA ligands, one was found to be coordinated in a bidentate mode, whereas two were in a monodentate mode, along with three nitrate ligands bonding in a monodentate fashion.

Sequential Block Copolymer Self-Assemblies Controlled by Metal-Ligand Stoichiometry.

While numerous efforts have been devoted to developing easy-to-use probes based on block copolymers for detecting analytes due to their advantages in the fields of self-assembly and sensing, a progressive response on block copolymers in response to a continuing chemical event is not readily achievable. Herein, we report the self-assembly of a 4-piperazinyl-1,8-naphthalimide based functional block copolymer (PS-b-PN), whose self-assembly and photophysics can be controlled by the stoichiometry-dependent metal-ligand interaction upon the side chain. The work takes advantages of (1) stoichiometry-controlled coordination-structural transformation of the piperazinyl moiety on PS-b-PN toward Fe(3+) ions, thereby resulting in a shrinkage-expansion conversion of the self-assembled nanostructures in solution as well as in thin film, and (2) stoichiometry-controlled competition between photoinduced electron transfer and spin-orbital coupling process upon naphthalimide fluorophore leading to a boost-decline emission change of the system. Except Fe(3+) ions, such a stoichiometry-dependent returnable property cannot be observed in the presence of other transition ions. The strategy for realizing the dual-channel sequential response on the basis of the progressively alterable nanomorphologies and emissions might provide deeper insights for the further development of advanced polymeric sensors.