Anionic Substituents Research Articles

Copper Dithiocarbamates: Coordination Chemistry and Applications in Materials Science, Biosciences and Beyond

Copper dithiocarbamate complexes have been known for ca. 120 years and find relevance in biology and medicine, especially as anticancer agents and applications in materials science as a single-source precursor (SSPs) to nanoscale copper sulfides. Dithiocarbamates support Cu(I), Cu(II) and Cu(III) and show a rich and diverse coordination chemistry. Homoleptic [Cu(S2CNR2)2] are most common, being known for hundreds of substituents. All contain a Cu(II) centre, being either monomeric (distorted square planar) or dimeric (distorted trigonal bipyramidal) in the solid state, the latter being held together by intermolecular C···S interactions. Their d9 electronic configuration renders them paramagnetic and thus readily detected by electron paramagnetic resonance (EPR) spectroscopy. Reaction with a range of oxidants affords d8 Cu(III) complexes, [Cu(S2CNR2)2][X], in which copper remains in a square-planar geometry, but Cu–S bonds shorten by ca. 0.1 Å. These show a wide range of different structural motifs in the solid-state, varying with changes in anion and dithiocarbamate substituents. Cu(I) complexes, [Cu(S2CNR2)2]−, are (briefly) accessible in an electrochemical cell, and the only stable example is recently reported [Cu(S2CNH2)2][NH4]·H2O. Others readily lose a dithiocarbamate and the d10 centres can either be trapped with other coordinating ligands, especially phosphines, or form clusters with tetrahedral [Cu(μ3-S2CNR2)]4 being most common. Over the past decade, a wide range of Cu(I) dithiocarbamate clusters have been prepared and structurally characterised with nuclearities of 3–28, especially exciting being those with interstitial hydride and/or acetylide co-ligands. A range of mixed-valence Cu(I)–Cu(II) and Cu(II)–Cu(III) complexes are known, many of which show novel physical properties, and one Cu(I)–Cu(II)–Cu(III) species has been reported. Copper dithiocarbamates have been widely used as SSPs to nanoscale copper sulfides, allowing control over the phase, particle size and morphology of nanomaterials, and thus giving access to materials with tuneable physical properties. The identification of copper in a range of neurological diseases and the use of disulfiram as a drug for over 50 years makes understanding of the biological formation and action of [Cu(S2CNEt2)2] especially important. Furthermore, the finding that it and related Cu(II) dithiocarbamates are active anticancer agents has pushed them to the fore in studies of metal-based biomedicines.

Substituent Effect on the Circularly Polarized Luminescence of C1‐Symmetric Carbene‐Copper(I) Complexes

AbstractThe substituent effect on the magnitude of the circularly polarized luminescence (CPL) of MentCAAC‐Cu‐X (X=F, Cl, Br, I, BH4, B3H8; CAAC=cyclic (alkyl)(amino)carbenes) complexes is experimentally investigated. This study examines seven pairs of enantiomeric complexes with small anionic substituents (halides, borohydrides, hydride). The complexes are fully characterized, including single crystal X‐ray diffraction studies, and chiroptical measurements show that small covalent anions induce a larger CPL magnitude. These results demonstrate that the magnitude of the CPL can be manipulated without making any modifications to the chiral ligand.

Thiophene-Based Optical Ligands That Selectively Detect Aβ Pathology in Alzheimer's Disease.

In several neurodegenerative diseases, the presence of aggregates of specific proteins in the brain is a significant pathological hallmark; thus, developing ligands able to bind to the aggregated proteins is essential for any effort related to imaging and therapeutics. Here we report the synthesis of thiophene‐based ligands containing nitrogen heterocycles. The ligands selectively recognized amyloid‐β (Aβ) aggregates in brain tissue from individuals diagnosed neuropathologically as having Alzheimer's disease (AD). The selectivity for Aβ was dependent on the position of nitrogen in the heterocyclic compounds, and the ability to bind Aβ was shown to be reduced when introducing anionic substituents on the thiophene backbone. Our findings provide the structural and functional basis for the development of ligands that can differentiate between aggregated proteinaceous species comprised of distinct proteins. These ligands might also be powerful tools for studying the pathogenesis of Aβ aggregation and for designing molecules for imaging of Aβ pathology.

Towards a Strategy for the Synthesis of Polymeric Ionic Liquids with a Bulk Anion in Various Reaction Media

The interest in polymerizable ionic liquids of researchers is due to their unique properties, such as good thermal stability, low vapor pressure, and wide potential window of stability. The complex of these properties determines the prospect of using ionic liquids and polymers based on them in the technology of membrane separation. This article describes the synthesis of monomeric ionic liquids (IL) containing quaternary amino groups, pyridine, and imidazole groups based on vinyl benzyl chloride (conversion was 95%). Further, on their basis, polymer ionic liquids were obtained by the method of free radical polymerization with bulky anionic substituents. Proof of the formation of polimeric IL was carried out by NMR and FTIR spectroscopy methods. The molecular weight of the IL was determined by gel permeation chromatography and reached ~ 140,000. An anion exchange reaction was carried out to replace the Cl anion with Tf2N.

π-Electronic Ion-Pairing Assemblies of Deprotonation-Induced Anions.

Dipyrrolylnitrophenols (DPPhs) afforded various hydrogen-bonding-stabilized π-electronic anions upon deprotonation. Through ion-pair metathesis, π-electronic cations were introduced as a counter species to provide π-electronic ion pairs that occurred as tightly bound states in solution while resulting in solid-state charge-by-charge assemblies. The assembling modes were modulated according to the geometries and electronic states of the positively charged constituents along with the substituents of the DPPh anions.

Influence of the Fluorinated Aromatic Fragments on the Structures of the Cadmium and Zinc Carboxylate Complexes Using Pentafluorobenzoates and 2,3,4,5-Tetrafluorobenzoates as Examples

A series of the cadmium and zinc carboxylate complexes with anions of pentafluorobenzoic (HРfbz) and 2,3,4,5-tetrafluorobenzoic (HТfbz) acids and N-donor ligands (1,10-phenanthroline (Phen) and quinoline (Quin)), [Cd(Pfbz)2(Phen)]n (I), [Cd(Рfbz)2(Рhen)2]·2MeCN (II), [Zn(H2O)-(Рfbz)2(Рhen)] (III), [Zn2Cd(Рfbz)6(Рhen)2]⋅2C6H6 (IV), [Cd2(H2O)2(Tfbz)4(Рhen)2] (V), [Cd2-(H2O)2(Tfbz)4(Quin)2] (VI), and [Cd(Tfbz)2(Phen)2]⋅HTfbz (VII), is synthesized. The structures of new complexes I–VII are determined by X-ray diffraction analysis (CIF files CCDC nos. 1871300, 2005461, 2005462, 2005464, 2005466, 2005465, and 2005459, respectively). The majority of the synthesized compounds is typical of intramolecular stacking interactions between the coordinated molecules of the aromatic N-donor ligands and fluorinated substituents of the carboxylate anions. These interactions lead to the formation of unusual compounds, which are different in the cases of pentafluorobenzoates and tetrafluorobenzoates, in particular, coordination polymer I and binuclear complexes V and VI with coordinated water molecules. The synthesized zinc and cadmium compounds differ in structure and composition.

1-Trifluoromethyl-prop-2-yne 1-iminium salts and 1-imines: reactions with the mesoionic „Nitron“

Abstract The heterocyclic mesoionic compound (1,4-diphenyl-1H-1,2,4-triazol-4-ium-3-yl)(phenyl)amide („Nitron“) has recently been found to exist in a prototropic equilibrium with minor amounts of a nucleophilic heterocyclic carbene of the 1,2,4-triazolyl-5-ylidene type. Here we report that Nitron reacts with 1-trifluoromethyl-substituted prop-2-yne iminium salts by conjugate nucleophilic addition of the anionic PhN‒ substituent in the mesoionic tautomer, whereas the nucleophilic triazolylidene form is involved in the reaction with 1-CF3-prop-2-yne imines. 3-(2,3-Dihydro-1H-benzo[c]azepin-5-yl)-1H-1,2,4-triazol-4-ium triflate salts were obtained in the former case and (Z)-9-arylidene-1,2,4,7-tetraazaspiro[4.4]nona-2,7-dienes in the latter.

Synthesis and the Effect of Anions on the Spectroscopy and Electrochemistry of Mono(dimethyl sulfoxide)-Ligated Cobalt Corroles.

A new series of cobalt A3-triarylcorroles were synthesized and the compounds examined as to their electrochemical and spectroscopic properties in CH2Cl2 or dimethyl sulfoxide (DMSO) containing 10 different anions added to the solution in the form of tetrabutylammonium salts. The investigated anions were PF6-, BF4-, HSO4-, ClO4-, Br-, I-, Cl-, OAc-, F-, OTs-, and CN-, all but three of which were found to facilitate reduction of the cobalt corrole in dilute CH2Cl2 solutions, as determined by a combination of UV-vis spectroscopy and spectroelectrochemistry. The synthesized corroles are represented as (Ar)3CorCo(DMSO), where Ar is a meso-phenyl group containing one of 10 different electron-donating or -withdrawing substituents. The axial DMSO ligand was found to dissociate in dilute (10-5 M) CH2Cl2 solutions, but this was not the case at the higher electrochemical concentration of 10-3 M, where the investigated corroles exhibit a rich redox reactivity, undergoing up to five reversible one-electron-transfer reactions under the different solution conditions. The reversible half-wave potentials for generation of the singly oxidized corroles varied by over 1.0 V with a change in the electron-donating or -withdrawing meso-phenyl substituents and type of anion added to the solution, ranging from E1/2 = 0.83 V in one extreme to -0.42 V in the other. Much smaller shifts in the potentials (on the order of ∼210 mV) were observed for the reversible first reduction as a function of changes of the anion and/or corrole substituents, with the only exception being in the case of CN-, where the E1/2 values in CH2Cl2 ranged from +0.08 V in solutions containing 0.1 M TBAClO4 to >-1.8 V upon the addition of CN-.

Investigation on the coordination behaviors of tris(2-pyridyl)pyrazolyl borates iron(II) complexes

A series of Fe(II) complexes bearing hydrotris[3-(2-pyridyl)-pyrazolyl]borate (Tppy) ligand are prepared and examined. Crystallographic results of those TppyFe(II) complexes exhibit several new types of binding modes resulting in a mononuclear or dinuclear species formation. Mononuclear complex [TppyFeCl](1) has a distorted square pyramidal Fe(II) center with one arm (pyrazolyl-pyridyl) dangling outside of coordination sphere; this is newly finding in TppyFe(II) chemistry. Complex [(Tppy)2Fe(OH2)](2) has shown unique coordination behaviour and hydrogen bonding interactions with dangling pyrazolyl-pyridyl arms of Tppy ligands which might shorten the Fe-OH2 bond length and stabilize the coordination modes. In contrast, complex [TppyFe(μ-OMe)]2(3) shows an unique methoxy bridging centrosymmetric dinuclear structure which is isolated from the reaction of KTppy with FeSO4·7H2O after re-crystallization process in methanol. The complex 3 also could isolate independently from the reaction of complex 1 with sodium methoxide. To further investigate the coordination modes on mononuclear complex 1, exogenous anionic substituents used to form [TppyFe(BF4)](4) and [TppyFe(N3)](5) which was confirmed by crystallography. The podand Tppy ligand and nature of exogenous ligand elucidate the systematic modification and coordination modes in ferrous complexes.

Mechanochemical synthesis of apatite and tricalciumphosphate as materials for medical purposes

This paper presents the results of the mechanochemical synthesis of hydroxyapatite (HAP) with Zn2+, Cu2+, K1+ and Cs1+ as substituents for the calcium ion and (ZrO4)4-, (SiO4)4- and (AlO3)3- anion substituents for the phosphate group with the substituent concentrations in the range of 0.04–2.0 mol per 1 mol of HAP. The use of Si-substituted HAP as a coating material promotes accelerated osteosynthesis and osteointegration of implants into the bone tissue. Zirconium and aluminum ions can promote the adhesion of coatings to ceramic implants. The replacement of calcium ions by Zn2+, Cu2+, K1+ and Cs1+ in the HAP structure plays an antimicrobial role preventing inflammatory processes.

Ethylene Oligomerization and Polymerization by Palladium(II) Methyl Complexes Supported by Phosphines Bearing a Perchlorinated 10-Vertex closo-Carborane Anion Substituent

The synthesis and ethylene reactivity of the zwitterionic Pd methyl complexes (κ2-P,Cl-PR2CB9Cl9)PdMe(THF) (7, R = iPr; 8, R = Ph) and (κ2-P,O-P(o-OMe-Ph)2CB9Cl9)PdMe(THF) (9), which contain the first phosphines appended with anionic 10-vertex perchlorinated closo-carboranes, are described. Complexes 7 and 8 oligomerize ethylene (23 °C, 2 atm) to a Schulz–Flory distribution of C4–C10 olefins with TOFs of ca. 8000 and 1800 t.o./h, respectively. 8 is ca. 4 times more active than the analogous (κ2-P,F-ortho-PPh2C6H4BF3)PdMe(L) (L = pyridine or collidine) system reported by Jordan and Piers, which produces butenes. Complex 9 reacts with ethylene to yield polyethylene wax (Mn ca. 1000, Đ ca. 1.5) that is similar to commercial Fischer–Tropsch waxes. The activities of 7–9 are independent of ethylene pressure and the presence of B(C6F5)3, suggesting that the catalyst resting state is the corresponding (PR2CB9Cl9)PdR(H2C═CH2) adduct. The molecular weights of the oligomer/polymer products are independent of ethylen...

Adhesive Hydrogel System Based on the Intercalation of Anionic Substituents into Layered Double Hydroxides.

Hydrogels comprising anionic substituents in their polymer network were synthesized and adhered to each other following application of layered double hydroxides (LDHs) onto their surfaces. The resulting systems displayed high adhesive strength and tolerance for changes in parameters like solvent, salt concentration, and temperature. In experiments involving hydrogels with bulky anionic substituents, it was confirmed that the efficiency of the intercalation of the anionic groups into the layered inorganic compound LDH determines the strength of the adhesion. Moreover, intercalation-based adhesive joints connecting anionic hydrogels displayed higher tolerance for saline solutions than adhesive joints relying on electrostatic interactions between anionic and cationic hydrogels, even though, because of the electrostatic repulsion between charges with the same sign, one would expect that polymer networks comprising opposite charges would tolerate better the disruption caused by high saline concentration.

An integrated approach (synthetic, structural and biological) to the study of aroylhydrazone salts

A change of anion or aroylhydrazone substituent position results in salts of different connectivities, thermal stabilities and properties.

Rheological and microrheological characterization of a novel amphoteric xanthan gum

ABSTRACTA novel amphoteric xanthan gum (AXG) containing anionic carboxyl groups and cationic quaternary ammonium substituents was prepared from xanthan gum (XG) and 3-chloro-2-hydroxypropyltriethanolammonium acetate. The rheological and microrheological properties of AXG and XG solutions were studied in this work. The rheological results showed that the apparent viscosity of the 0.4% AXG solution was 5.26 times that of the 0.4% XG solution, and the AXG solution exhibited more obvious thixotropy and much stronger viscoelasticity than the XG solution. Both experiment and numerical simulations were adopted to investigate the gel-breaking process of the AXG solution, and the rheokinetics equations can well describe the evolution of complex viscosity. Moreover, the optical microrheology method was also adopted to investigate the microrheological behavior of AXG and XG solutions. The microrheological results showed that the AXG solution exhibited higher viscosity index at zero shear and a more obvious solid-like behavior than the XG solution. Good agreement is found when comparing the results obtained from microrheology to classical rheology, which verifies the feasibility of the microrheology method for measuring the solution properties, especially some properties not well described by the current rheological approach.

Dealing at Arm's Length: Catalysis with N‐Heterocyclic Carbene Ligands Bearing Anionic Tethers

The catalytic transformations enabled by bidentate N‐heterocyclic carbenes bearing anionic substituents (tethered NHCs) are presented. The use of tethered NHCs as a ligand class for transition‐metal‐catalyzed reactions and their employment in organocatalytic and Lewis‐base‐catalyzed processes is discussed, with a focus on the influence of the anionic tether on the catalyzed reactions of interest.

Dynamic covalent bonding-triggered supramolecular gelation derived from tetrahydroxy-bisurea derivatives.

A new class of bisurea derivatives bearing tetrahydroxy groups have been proven to be non-gelators in water and various organic solvents even under long-term sonication or efficient heating treatment. We found that it is possible to trigger physical gelation behaviour by constructing dynamic covalent bonding. The results show that formation of dynamic covalent bonding between the borate anion and ethanediol substituent in these bisurea derivatives brings about rapid physical gelation at ambient temperature in a mixture of DMSO and water. During dynamic covalent bonding-triggered gelation, the stepgrowth polymerization from the B-O bonds would increase the size of the molecules and reduce the entropy of mixing as well as facilitate ion-dipole interactions in the linear polymeric gelators. They would drive a self-assembly transition and boost the construction of gel networks in coordination with α-tape urea-urea hydrogen bonding. The gelation mechanism was explored by 1H NMR, FTIR and rheology techniques. Moreover, the resulting gels are transparent and thixotropic, and could be turned into the sol state under CO2 or water-stimulus. Furthermore, they are stable in the presence of HAuCl4 and alkali. Therefore, they would afford another new medium for the growth of Au nanocrystals via in situ reduction and a new sensing medium for detecting Hg2+ ions.

Micellar aggregation of Triton X-100 surfactant in imidazolium ionic liquids

In this work we investigated aggregation behavior of a nonionic surfactant Triton X-100 in eighteen imidazolium ionic liquids (ILs) with two to eight carbon atoms in cations alkyl chain, namely 1-ethyl-3-methylimidazolium, [EMIM], 1-butyl-3-methylimidazolium, [PrMIM], 3-methyl-1-propylimidazolium, [BMIM], 1-hexyl-3-methylimidazolium, [PMIM], 3-methyl-1-pentyl-imidazolium, [HMIM], and 1-octyl-3-methylimidazolium, [OMIM], and with different anion substituents, such as tetrafluoroborate, [BF4], hexafluorophosphate, [PF6], bis(trifluoromethanesulfonyl)imide, [Tf2N], and trimethylosulfonate, [TfO]. Surface tension, density and dynamic light scattering measurements were conducted to determine surface and micellar behavior of the surfactant in ionic liquids. In addition, conductometric study gave information on an average number of imidazolium cations associating with each oxyethylene unit of the surfactant. An influence of anion and cation species on the ability of ILs to support Triton X-100 micelle formation was stated and discussed in terms of cohesive energy density.

Substituted hydroxyapatites for bone regeneration: A review of current trends.

At present hydroxyapatite (HA) is been extensively investigated for biomedical applications, largely as a result of its similarity in composition to the mineral portion of bone. Although HA undergoes osseointegration and is bioactive and osteoconductive, the inherent brittleness and low fracture toughness limits its use under load bearing conditions, also once implanted in the body, HA takes a long time to resorb. The crystal structure of HA is conducive to a variety of ionic substitutions. To accurately mimic the calcium deficient and carbonate-containing nature of HA in bone, both cationic and anionic substituents have been incorporated to synthetic HA. This article focuses on the incorporation of both the well established (Zn, Si, Sr, F, and carbonate) and latest ions (Ag, citrate, iron, niobate, and tantalates) into the HA structure and aims to highlight the key effects of these substitutions in terms of their chemical, physical, and biological properties. It can be shown that a minor substituent cannot only alter the microstructure, stability and crystallinity of the HA structure in an implant, but also have a significant effect on bone cells colonizing the implant, which in turn can influence the new bone formation and bone remodeling processes. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1285-1299, 2017.

Highly selective binding of methyl orange dye by cationic water-soluble pillar[5]arenes.

A new water-soluble pillar[5]arene with an amide fragment and triethylammonium groups was synthesized by our original method of aminolysis of the ester groups. Using UV-spectroscopy, it is shown that cationic pillar[5]arenes are able to selectively form 1 : 1 complexes with some hydrophobic anions: the guests with bulky uncharged or negatively charged substituents hindering entry into the macrocycle cavity. Highly selective binding of the most lipophilic guest, methyl orange dye, in the form of organic anion salts by positively charged water-soluble pillar[5]arenes was detected. In the case of the azo dye the appropriate Kass values were 10-100-fold higher than those calculated for the other sulfonic acid derivatives studied. The 2D NMR NOESY (1)H-(1)H spectroscopy confirms the formation of the inclusion complex: negative charge sulfonate head is outside the cavity of pillar[5]arenes and the hydrophobic fragment of the guest is located in the cavity.

The development of a light-up red-emitting fluorescent probe based on a G-quadruplex specific cyanine dye

Cyanine dye-dimethylindole red containing an anionic propylsulfonate substituent and an extending polymethine chain was found to behave as a highly specific red-emitting G-quadruplex probe, especially for parallel G-quadruplex c-myc.