Novel Dy(III) Sensor Based on a New Bis‐Pyrrolidene Schiff's Base

In this work a dysprosium [Dy(III)]‐selective solvent polymeric membrane sensor based on N,N‐bis(pyrrolidene) benzne‐1,2‐diamine, poly(vinyl chloride)(PVC), the plasticizer benzylacetate (BA), and anionic site is described. This sensor responds to Dy(III) activity in a linear range from 1.0×10^?5 to 1.0×10^?1 M, with a slope of 20.6±0.2 mV per decade and a detection limit of 6.0×10^?6 M at the pH range of 3.5–8.0. It has a fast response time of<20 s in the entire concentration range, and can be used for at least 2 months without any considerable divergence in the electrode potentials. The proposed sensor revealed comparatively good selectivity with respect to common alkali, alkaline earth, transition and heavy metal ions. It was used as an indicator electrode in the potentiometric titration of fluoride ions and in determination of concentration of F ^– ions in some mouth washing solutions.     

Synthesis and fluorescence properties of dysprosium‐coordinated with high‐Tg polyaryletherketones containing carboxyl side groups

A series of novel dysprosium coordination polymers were synthesized using new high‐T_g carboxyl‐containing polyaryletherketones (PEKs) as macromolecular ligands and a small molecule, 1,10‐phenanthroline, as co‐ligand. The FTIR, WAXD, and UV–Vis results indicated that the dysprosium ions were coordinated simultaneously with carboxyl group of PEKs and 1,10‐phenanthroline, and homogeneously distributed along the polymer backbone. These obtained dysprosium coordination polymers showed excellent film‐formation properties. Moreover, all the dysprosium coordination polymers could exhibit the intense characteristic emission of dysprosium ions under UV excitation. Meanwhile, the emission intensity increased with increasing dysprosium ion content, and no obvious fluorescence quenching happened at the Dy³⁺ ion content up to 10.71 wt%, which was attributed to the very rigid structure of PEK and synergistic coordination effect of PEK and 1,10‐phenanthroline. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental Determination of Magnetic Anisotropy in Exchange‐Bias Dysprosium Metallocene Single‐Molecule Magnets

We investigate a family of dinuclear dysprosium metallocene single‐molecule magnets (SMMs) bridged by methyl and halogen groups [Cp′₂Dy(μ‐X)]₂ (Cp′=cyclopentadienyltrimethylsilane anion; 1 : X=CH₃^?; 2 : X=Cl^?; 3 : X=Br^?; 4 : X=I^?). For the first time, the magnetic easy axes of dysprosium metallocene SMMs are experimentally determined, confirming that the orientation of them are perpendicular to the equatorial plane which is made up of dysprosium and bridging atoms. The orientation of the magnetic easy axis for 1 deviates from the normal direction (by 10.3°) due to the stronger equatorial interactions between Dy^III and methyl groups. Moreover, its magnetic axes show a temperature‐dependent shifting, which is caused by the competition between exchange interactions and Zeeman interactions. Studies of fluorescence and specific heat as well as ab initio calculations reveal the significant influences of the bridging ligands on their low‐lying exchange‐based energy levels and, consequently, low‐temperature magnetic properties.     

Tuning the Magnetic Interactions and Relaxation Dynamics of Dy2 Single‐Molecule Magnets

Efficient modulation of single‐molecule magnet (SMM) behavior was realized by deliberate structural modification of the Dy₂ cores of [Dy₂( a ′ povh )₂(OAc)₂(DMF)₂] ( 1 ) and [Zn₂Dy₂( a′povh )₂(OAc)₆] ? 4 H₂O ( 2 ; H₂ a ′ povh =N′‐[amino(pyrimidin‐2‐yl)methylene]‐o‐vanilloyl hydrazine). Compound 1 having fourfold linkage between the two dysprosium ions shows high‐performance SMM behavior with a thermal energy barrier of 322.1 K, whereas only slow relaxation is observed for compound 2 with only twofold connection between the dysprosium ions. This remarkable discrepancy is mainly because of strong axiality in 1 due to one pronounced covalent bond, as revealed by experimental and theoretical investigations. The significant antiferromagnetic interaction derived from bis(μ₂‐O) and two acetate bridging groups was found to be crucial in leading to a nonmagnetic ground state in 1 , by suppressing zero‐field quantum tunneling of magnetization.     

Lanthanoid Antimonides Ln2Sb5 (Ln = Sm,Gd, Tb,Dy) and Rationalization of Chemical Bonding within the Antimony Polyanion by Combining the Zintl‐Klemm Concept with Bond‐Length Bond‐Strength Relationships

The title compounds are formed by peritectic reactions. Single crystals could be isolated from samples with high antimony content. Their structure was determined for Dy₂Sb₅ from four‐circle X‐ray diffractometer data: P2₁/m, a = 1306.6(1) pm, b = 416.27(4) pm, c = 1458.4(1) pm, β = 102.213(8)°, Z = 4, R = 0.061 for 2980 structure factors and 86 variable parameters. All dysprosium atoms have nine antimony neighbors forming tricapped trigonal prisms with Dy–Sb distances varying between 308 and 338 pm. The antimony atoms occupy ten different sites with greatly varying coordination. One extreme case is an antimony atom surrounded only by dysprosium atoms in trigonal prismatic arrangement, the other one is an antimony atom in distorted octahedral antimony coordination. The various antimony‐antimony interactions (with Sb–Sb distances varying between 284 and 338 pm) are rationalized by combining the Zintl‐Klemm concept with bond‐length bond‐strength considerations.     

Synthesis and characterization of a novel,fluoride‐releasing dimethacrylate monomer and its dental composite

A novel, fluoride‐releasing dimethacrylate monomer containing zirconium fluoride chelate for use in dental composites was synthesized by an efficient four‐step procedure starting from 4,4‐bis‐(4‐hydroxyphenyl)‐pentanoic acid and was characterized by electrospray mass spectrometry, Fourier transform infrared (FTIR), and ¹H and ¹³C NMR spectroscopies. The synthesized monomer was photopolymerized with camphorquinone and 1‐phenyl‐1,2‐propane‐dione as initiators and N,N‐dimethylaminoethyl methacrylate as an accelerator. The photopolymerization process was investigated by FTIR spectroscopy. The experimental composite containing 13.7 wt % of the synthesized monomer was tested for fluoride release, fluoride recharge, compressive strength, and flexure strength, each in comparison to three commercial flowable dental composites. The results showed that the experimental composite had significantly higher fluoride release and fluoride recharge capabilities than the commercial flowable composites. The flexure strength was comparable to the commercial materials. The water sorption and solubility met the requirements of the International Organization for Standardization 4049 and the American National Standards Institute/American Dental Association Specification Number 27. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 985–998, 2004     

The sensing mechanism of fluoride anion for a novel molecule D2: Desilylation and intramolecular charge transfer

In this work, the sensing mechanism of a new fluoride chemosensor 12‐([tert‐butyldiphenylsilyl]oxy)‐8a,13a‐dihydro‐7H‐benzo[de]benzo[4,5]imidazo[2,1‐a]‐isoquinolin‐7‐one (abbreviated as D2) is investigated using density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. The theoretical electronic spectra (vertical excitation energies and fluorescence peak) reproduced previous experimental results (D. Li et al., Spectrochim. Acta A Mol. Biomol. Spectrosc. 2017 , 185, 173), which confirms the rationality of the theoretical level used in this work. The constructed potential energy curve of the desilylation process suggests that the low barrier could be responsible for the rapid response to fluoride anions. Analyses of the binding energies show that only fluoride anion can be detected by D2 chemosensor in dimethylsulfoxide (DMSO). In view of the excitation process, the strong intramolecular charge transfer (ICT) process of the S₀ → S₁ transition explains the red shift of the absorption peak of the D2 sensor with the addition of fluoride anions. This work not only presents a straightforward sensing mechanism of sensing of the fluoride anion by the D2 chemosensor but should also play an important role in the synthesis and design of fluorescent sensors in future.     

Ion imprinted polymer based ion-selective electrode for the trace determination of dysprosium(III) ions

Ion-selective electrode (ISE) was designed by dispersing the dysprosium(III) IIP particles in 2-nitrophenyloctyl ether plasticizer and then embedded in polyvinyl chloride matrix. The ISE shows a Nernstian response for dysprosium(III) over a wide concentration range (8.0 × 10⁻⁶ to 1.0 × 10⁻¹ M) with a slope of 21.7 mV per decade. The limit of detection was 2 × 10⁻⁶ M. This sensor has a very fast response time (∼10 s) and offers high selectivity compared to conventional chemical sensors towards dysprosium(III) with respect to several alkali, alkaline earth and transition metal ions as the selectivity is 10-100-fold better. The sensor was used for determination of dysprosium(III) ions by potentiometric (EDTA) titration and has been successfully demonstrated for the determination of fluoride in mouth wash solution.     

Fluorinated,crosslinkable terpolymers based on vinylidene fluoride and bearing sulfonic acid side groups for fuel‐cell membranes

The radical terpolymerization of 8‐bromo‐1H,1H,2H‐perfluorooct‐1‐ene with vinylidene fluoride (VDF) and perfluoro(4‐methyl‐3,6‐dioxaoct‐7‐ene) sulfonyl fluoride is presented. Changing the feed compositions of these three fluorinated comonomers enabled us to obtain different random‐type poly[vinylidene fluoride‐ter‐perfluoro(4‐methyl‐3,6‐dioxaoct‐7‐ene) sulfonyl fluoride‐ter‐8‐bromo‐1H,1H,2H‐perfluorooct‐1‐ene] terpolymers containing various sulfonyl fluoride and brominated side groups. Yields higher than 70% were reached in all cases. The hydrolysis of the sulfonyl fluoride group into the ? SO₃Li function in the presence of lithium carbonate was quantitatively achieved without the content of VDF being affected, and so dehydrofluorination of the VDF base unit was avoided. These original terpolymers were then crosslinked via dangling bromine atoms in the presence of a peroxide/triallyl isocyanurate system, which produced films insoluble in organic solvents such as acetone and dimethylformamide (which totally dissolved uncured terpolymers). The acidification of ? SO₃Li into the ? SO₃H function enabled protonic membranes to be obtained. The thermal stabilities of the crosslinked materials were higher than those of the uncured terpolymers, and their electrochemical performances were investigated. According to the contents of the sulfonic acid side functions, the ion‐exchange capacities ranged from 0.6 to 1.5 mequiv of H⁺/g, whereas the water uptake and conductivities ranged from 5–26% (±11%) and from 0.5 to 6.0 mS/cm, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4566–4578, 2006     

A Tunable and Enantioselective Hetero‐Diels–Alder Reaction Provides Access to Distinct Piperidinoyl Spirooxindoles

The active complexes of chiral N,N′‐dioxide ligands with dysprosium and magnesium salts catalyze the hetero‐Diels–Alder reaction between 2‐aza‐3‐silyloxy‐butadienes and alkylidene oxindoles to selectively form 3,3′‐ and 3,4′‐piperidinoyl spirooxindoles, respectively, in very high yields and with excellent enantioselectivities. The exo ‐selective asymmetric cycloaddition successfully regaled the construction of sp³‐rich and highly substituted natural‐product‐based spirooxindoles supporting many chiral centers, including contiguous all‐carbon quaternary centers.     

TD‐DFT study on the sensing mechanism of a fluorescent chemosensor for fluoride: Excited‐state proton transfer

An excited‐state proton transfer (ESPT) process, induced by both intermolecular and intramolecular hydrogen‐bonding interactions, is proposed to account for the fluorescence sensing mechanism of a fluoride chemosensor, phenyl‐1H‐anthra(1,2‐d)imidazole‐6,11‐dione. The time‐dependent density functional theory (TD‐DFT) method has been applied to investigate the different electronic states. The present theoretical study of this chemosensor, as well as its anion and fluoride complex, has been conducted with a view to monitoring its structural and photophysical properties. The proton of the chemosensor can shift to fluoride in the ground state but transfers from the proton donor (NH group) to a proton acceptor (neighboring carbonyl group) in the first singlet excited state. This may explain the observed red shifts in the fluorescence spectra in the relevant fluorescent sensing mechanism. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

A New Planar Hexanuclear Dysprosium Cluster Exhibiting Slow Magnetic Relaxation Features

Reaction of the Schiff base ligand H₂L and dysprosium acetate result in a new planar Dy₆ cluster [Dy₆(μ₃‐OH)L₆(Ac)₆] · MeOH ( 1 ) [H₂L = N'‐(2‐hydroxybenzylidene)‐2‐(hydroxyimino)propanohydrazide, HAc = acetic acid], which was successfully structurally and magnetically characterized. Single‐crystal X‐ray diffraction analysis revealed that 1 contained a hexanuclear dysprosium cluster [Dy₆], which is composed of four Dy₃ triangular units. Magnetic measurements suggest that 1 displays single‐molecule magnet (SMM) behavior which is enhanced by applying a 4000 Oe direct‐current field. The effective anisotropic barrier U_eff/k_B = 14.9 K and the pre‐exponential factor τ₀ = 1.31 × 10^–6 s are also obtained. This work may provide more insights for the design and investigation of lanthanide‐based SMMs.     

Fluoride Sensing by Catechol‐Based π‐Electron Systems

We have developed new catechol‐based sensors that can detect fluoride via fluorescence or optical absorption even in the presence of other halides. The level and sensitivity of detection of the sensing molecules is dependent on the chromophore length, which is controlled by the number of thiophene units (one to three) within the chromophore. The sensor with three thiophene units, (E)‐2‐(2,2′‐terthiophen‐5‐yl)‐3‐(3,4‐dihydroxyphenyl)acrylonitrile, gives the best response to fluoride. By using fluorescence measurements fluoride is detectable over the concentration range 1.7 μM to 200 μM . Importantly, when adsorbed onto a solid support the fluorescent catechol dye can be used to detect the presence of fluoride in aqueous solution.     

Single‐Molecule Magnetism in Three Dy2 Complexes from the Use of a Pentadentate Schiff Base Ligand and Different Benzoates

Three dinuclear dysprosium(III) complexes, [Dy₂L₂(O₂CPh)₂]?2 MeOH ( 1 ), [Dy₂L₂{(2‐NO₂)O₂CPh}₂] ( 2 ), and [Dy₂L₂{(2‐OH)O₂CPh}₂] ? MeOH ? MeCN ( 3 ) (H₂L=N₁,N₃‐bis(4‐chlorosalicyladehyde)diethylenetriamine), have been synthesized and structurally characterized. Complexes 1 – 3 possess similar Ln₂ cores and differ in substituents at the benzyl rings of benzoates. Direct current (dc) magnetic susceptibility studies in the 2–300 K range showed weak antiferromagnetic interactions between two dysprosium(III) ions in 1 – 3 . The alternating current (ac) magnetic susceptibility measurements indicated that they all exhibited SMM behavior. The strategic attachment of the ?NO₂ group (in 2 ) and the ?OH functionality (in 3 ) on the skeleton of the benzoic acid led to subtle variations of the bond lengths and bond angles in the coordination environments of the central dysprosium(III) ions, consequently resulting in the enhancement of the energy barriers for 2 and 3 . Complete‐active‐space self‐consistent field (CASSCF) calculations were employed to rationalize the experimental outcomes. Theoretical calculations confirm the existence of antiferromagnetic interactions in 1 – 3 , and the calculated dc magnetic susceptibility data agree well with those obtained experimentally. The computational results reveal more axial g tensors, as well as higher first excited Kramers doublets in 2 and 3 ; thus resulting in higher energy barriers in compounds 2 and 3 .     

Synthesis of Lanthanide(III) Chelates by Using ‘Click’ Chemistry

The copper(I)‐catalyzed dipolar [2+3] cycloaddition reaction of an azide and a terminal alkyne is exploited in the preparation of various europium(III), terbium(III), and dysprosium(III) chelates (Schemes 1–3). By changing the nature of the alkyne and the azide, a wide range of chelates and biomolecule‐labeling reactants were obtained. The photophysical properties (Table) of the synthesized chelates are also discussed.     

Novel method for the synthesis of 1,2,4‐oxadiazoles using alumina supported ammonium fluoride under solvent‐free condition

Alumina supported ammonium fluoride was found as an efficient reagent for the synthesis of 1,2,4‐oxadi‐azoles of amidoximes under solvent free conditions using microwave irradiation. This method is a one‐pot, easy, rapid, and high‐yielding reaction for the synthesis of 1,2,4‐oxadiazole derivatives from amidoximes and acyl chlorides. Reaction of amidoximes with acylchlorides in the presence of alumina without ammonium fluoride gave only the corresponding O‐acylamidoximes as major product.     

Aluminum(III) Porphyrins as Ionophores for Fluoride Selective Polymeric Membrane Electrodes

Aluminum(III) porphyrins are examined as potential fluoride selective ionophores in polymeric membrane type ion‐selective electrodes. Membranes formulated with Al(III) tetraphenyl (TPP) or octaethyl (OEP) porphyrins are shown to exhibit enhanced potentiometric selectivity for fluoride over more lipophilic anions, including perchlorate and thiocyanate. However, such membrane electrodes display undesirable super‐Nernstian behavior, with concomitant slow response and recovery times. By employing a sterically hindered Al(III) picket fence porphyrin (PFP) complex as the membrane active species, fully reversible and Nernstian response toward fluoride is achieved. This finding suggests that the super‐Nernstian behavior observed with the nonpicket fence metalloporphyrins is due to the formation of aggregate porphyrin species (likely dimers) within the membrane phase. The steric hindrance of the PFP ligand structure eliminates such chemistry, thus leading to theoretical response slopes toward fluoride. Addition of lipophilic anionic sites into the organic membranes enhances response and selectivity, indicating that the Al(III) porphyrin ionophores function as charged carrier type ionophores. Optimized membranes formulated with Al(III)‐PFP in an o‐nitrophenyloctyl ether plasticized PVC film exhibit fast response to fluoride down to 40 μM, with very high selectivity over SCN^?, ClO₄^?, Cl^?, Br^? and NO₃^? (k^pot<10^?3 for all anions tested). With further refinements in the membrane chemistry, it is anticipated that Al(III) porphyrin‐based membrane electrodes can exhibit potentiometric fluoride response and selectivity that approaches that of the classical solid‐state LaF₃ crystal‐based fluoride sensor.     

Synthesis and characterization of novel fluoride‐releasing monomers. II. Dimethacrylates containing bis(aminodiacetic acid) and their ternary zirconium fluoride complexes

Novel dimethacrylate monomers containing bis(aminodiacetic acid) chelating ligands with or without additional hydroxyl groups were synthesized, starting from 2,2‐bis(4‐hydroxy‐3‐methylphenyl)propane. The structures of the monomers were characterized by electrospray mass spectrometry (ESMS), ¹H NMR, and ¹³C NMR. The structures and relative stability of fluoride‐releasing monomers containing one or more ternary zirconium fluoride complex moieties were studied by ESMS. The most stable ternary zirconium fluoride complex was in the form of [LZrF]^?, where H₄L is the monomer containing bis(aminodiacetic acid) without additional hydroxyl groups. The synthesized monomer was photopolymerized with camphorquinone and 1‐phenyl‐1,2‐propane‐dione as initiators and N,N‐dimethylaminoethyl methacrylate as the accelerator. The fluoride release, fluoride recharge, compressive strength, and flexure strength were tested on the experimental dental composite containing 13.7 wt % synthesized monomer and three commercial flowable dental composites. The results showed that the experimental composite has significantly higher fluoride release and recharge capabilities than the commercial flowable composites. The compressive strength was comparable to that of the commercial materials. The water sorption and solubility met the requirement of the ISO Specification 4049. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3153–3166, 2005     

Photoluminescent and Liquid‐Crystalline Properties of Donor–Acceptor‐Type 2,5‐Diarylthiazoles

The synthesis of donor–acceptor‐type 2,5‐diarylthiazoles that bear electron‐donating N,N‐dialkylamine and electron‐withdrawing cyano groups at the 2‐ and 5‐position, respectively, were carried out with transition‐metal‐catalyzed C? H arylation reactions developed by us. The compounds were synthesized by the C? H arylation of unsubstituted thiazole at the 2‐position with a palladium/copper catalyst in the presence of tetrabutylammonium fluoride (TBAF) as an activator. Further C? H arylation of the 2‐arylated thiazole at the 5‐position was carried out by the palladium‐catalyzed reaction in the presence of silver(I) fluoride to afford the donor–acceptor‐type 2,5‐diarylthiazoles with N,N‐dialkylamine groups of different chain lengths. The UV/Vis absorption, photoluminescence, and electrochemical behavior were similar regardless of chain length, whereas liquid‐crystalline behavior and thermal characteristics were found to be dependent on the alkyl‐chain length. The compounds with N,N‐diethylamine or N‐butyl‐N‐methyl groups showed a stable liquid‐crystalline phase over a wide temperature range as well as higher stability to thermal decomposition.     

A Journey towards Salivary Fluoride Level Detection by Suitable Low Cost Chemosensor: From Molecule to Product

Fluoride is a ubiquitous anion and essential for us owing to its ability to protect human body from several health related issues. The safe limit of Fluoride ion for human body is 1.5 ppm, above it the ion becomes toxic and can cause dental‐skeletal fluorosis or urolithiasis. Several countries are facing such health hazard owing to the naturally abundant excess fluoride in ground water. As a consequence, habitants of such fluoride enriched zone needs to monitor the concentration of fluoride in their body by periodic analysis. In this regard, development of a chemosensor which can detect fluoride from human body fluid at easy‐instant‐economic way is an obvious mandate. For the first time, our group has developed a sensor kit and sensor station device as a deliverable product for individual and batch scale detection of salivary fluoride level by colorimetric method. The sensor station is the first device made by interfacing chemical output with electronics and the encrypted signal in digital version could be used as a level of fluoride in saliva. Our journey towards the development of suitable chemosensor for recognition of fluoride from human body fluid is summarized in this account.