Dicationic Compounds Research Articles

On the Coordination Chemistry of Triazolyl‐substituted Diborane Ligands, Prepared by 1,3‐dipolar Cycloaddition Reactions between Diazido‐diboranes and Alkynes

AbstractMetal‐free cycloaddition reactions between a diazido‐diborane and alkynes are used to synthesize new ditriazolyl‐diborane molecules, a bis(ferrocenyl‐1,2,3‐triazolyl)‐diborane and a bis(2‐pyridyl‐1,2,3‐triazolyl)‐diborane. Then, the bis(2‐pyridyl‐1,2,3‐triazolyl)‐diborane was used as polydentate ligand for the synthesis of larger architectures. Reaction with ditriflato‐diborane yielded a tetracationic hexaboron compound, and reaction with metal salts yielded dicationic ring compounds with two hexacoordinate metal atoms and two integrated diborane units.

Experimental and theoretical study of tetraphenylethylene-based dicationic compounds for corrosion inhibition of steel and brass in an acidic medium

TPE-based compounds with AIE feature were developed for corrosion protection, exhibiting high inhibition efficiencies for steel and brass in H2SO4.

N, N’‐Disubstituted Benzimidazolium Salts: Synthesis, Characterization, Micromolar Detection of Fe(III) ions in Aqueous system, Biological Evaluation and Molecular Docking Studies

AbstractA series of dicationic N, N’‐disubstituted benzimidazolium salts with Br− and PF6− as the counter anions were synthesized in 75–98 % yields. The single crystal X‐ray diffraction studies of one of the benzimidazolium salts confirmed the structure of these dicationic compounds. These salts exhibited a selective “turn‐off” fluorescence response toward Fe3+ ions in aqueous solution over the other competitive metal ions such as Ag+, Al3+, Ba2+, Ca2+, Co2+, Cr3+, Cu2+, Fe2+, K+, Mg2+, Na+, Ni2+, Pb2+, and Zn2+. Upon addition of 5 equivalents Fe3+ ions, emission intensity was quenched by 94–99 % in pure aqueous media. Detection limits for all probes with Fe3+ ions were found in micromolar range. Further, drug combination analysis was conducted by evaluating the combinatorial treatment effects of two benzimidazolium salts with doxorubicin on breast cancer cells using the Chou‐Talalay method and the Highest Single Agent (HSA) model, and it was found that these compounds showed synergism with doxorubicin. Further, molecular docking studies revealed the best docking score (−6.11) for one of the benzimidazolium salts, and explained its binding affinity with checkpoint kinase 2 (chk2) protein.

Thermoresponsive Ionic Liquid with Different Cation-Anion Pairs as Draw Solutes in Forward Osmosis.

We synthesized various phosphonium- and ammonium-based ionic liquids (ILs), using benzenesulfonate (BS) and 4-methylbenzenesulfonate (MBS) to establish the criteria for designing an ideal draw solute in a forward osmosis (FO) system. Additionally, the effects of monocationic, dicationic, and anionic species on FO performance were studied. Monocationic compounds ([P4444][BS], [P4444][MBS], [N4444][BS], and [N4444][MBS]) were obtained in one step via anion exchange. Dicationic compounds ([(P4444)2][BS], [(P4444)2][MBS], [(N4444)2][BS], and [(N4444)2][MBS]) were prepared in two steps via a Menshutkin SN2 reaction and anion exchange. We also investigated the suitability of ILs as draw solutes for FO systems. The aqueous [P4444][BS], [N4444][BS], [N4444][MBS], and [(N4444)2][BS] solutions did not exhibit thermoresponsive behavior. However, 20 wt% [P4444][MBS], [(P4444)2][BS], [(P4444)2][MBS], and [(N4444)2][MBS] had critical temperatures of approximately 43, 33, 22, and 60 °C, respectively, enabling their recovery using temperature. An increase in IL hydrophobicity and bulkiness reduces its miscibility with water, demonstrating that it can be used to tune its thermoresponsive properties. Moreover, the FO performance of 20 wt% aqueous [(P4444)2][MBS] solution was tested for water flux and found to be approximately 10.58 LMH with the active layer facing the draw solution mode and 9.40 LMH with the active layer facing the feed solution.

Methyl Viologens of Bis-(4'-Pyridylethynyl)Arenes - Structures, Photophysical and Electrochemical Studies, and their Potential Application in Biology.

A series of bis‐(4’‐pyridylethynyl)arenes (arene=benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis‐N‐methylpyridinium compounds were investigated as a class of π‐extended methyl viologens. Their structures were determined by single crystal X‐ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds. The neutral compounds showed very small Stokes shifts, which are a little larger for the dications. All of the compounds showed very short fluorescence lifetimes (<4 ns). The neutral compound with an anthracene core has a quantum yield of almost unity. With stronger acceptors, the analogous bis‐N‐methylpyridinium compound showed a larger two‐photon absorption cross‐section than its neutral precursor. All of the dicationic compounds interact with DNA/RNA; while the compounds with benzene and tetrafluorobenzene cores bind in the grooves, the one with an anthracene core intercalates as a consequence of its large, condensed aromatic linker moiety, and it aggregates within the polynucleotide when in excess over DNA/RNA. Moreover, all cationic compounds showed highly specific CD spectra upon binding to ds‐DNA/RNA, attributed to the rare case of forcing the planar, achiral molecule into a chiral rotamer, and negligible toxicity toward human cell lines at ≤10 μM concentrations. The anthracene‐analogue exhibited intracellular accumulation within lysosomes, preventing its interaction with cellular DNA/RNA. However, cytotoxicity was evident at 1 μM concentration upon exposure to light, due to singlet oxygen generation within cells. These multi‐faceted features, in combination with its two‐photon absorption properties, suggest it to be a promising lead compound for development of novel light‐activated theranostic agents.

Search for Selective Glua1 Ampa Receptor Antagonists in a Series of Dicationic Compounds

Search for Selective Glua1 Ampa Receptor Antagonists in a Series of Dicationic Compounds

Novel Pyridazin-3(2H)-one-Based Guanidine Derivatives as Potential DNA Minor Groove Binders with Anticancer Activity.

Novel aryl guanidinium analogues containing the pyridazin-3(2H)-one core were proposed as minor groove binders (MGBs) with the support of molecular docking studies. The target dicationic or monocationic compounds, which show the guanidium group at different positions of the pyridazinone moiety, were synthesized using the corresponding silyl-protected pyridazinones as key intermediates. Pyridazinone scaffolds were converted into the adequate bromoalkyl derivatives, which by reaction with N,N’-di-Boc-protected guanidine followed by acid hydrolysis provided the hydrochloride salts 1–14 in good yields. The ability of new pyridazin-3(2H)-one-based guanidines as DNA binders was studied by means of DNA UV-thermal denaturation experiments. Their antiproliferative activity was also explored in three cancer cell lines (NCI-H460, A2780, and MCF-7). Compounds 1–4 with a bis-guanidinium structure display a weak DNA binding affinity and exhibit a reasonable cellular viability inhibition percentage in the three cancer cell lines studied.

Radially π-Extended Pyrrole-Fused Azacoronene: A Series of Crystal Structures of HPHAC with Various Oxidation States.

Radially π-extended hexapyrrolohexaazacoronene (HPHAC 2) was synthesized in two steps with 2,5-di-tert-butyl-acenaphtho[1,2-c]pyrrole and hexafluorobenzene. Like its parent HPHAC 1a, 2 exhibited reversible oxidation behavior. Crystal structures of not only the neutral and dicationic compounds but also the radical cation were all revealed. While analyzing its peculiar structure, the formation of a 1:1 complex with C60 was observed in solution by NMR and absorption analyses. The spectroscopic analyses of 2 and 1a were performed based on magnetic circular dichroism and theoretical calculations.

Novel Inhibitors for Corrosion Protection of Galvanized Steel

Nitrogen-containing heterocyclic dicationic compounds with antioxidant properties have been synthesized and characterized by NMR spectroscopy. Their corrosion inhibiting behavior for zinc and steel protection have been studied by electrochemical polarization methods to assess the potential suitability of those compounds in hybrid galvanic zinc protective coatings. The individual assessment for corrosion inhibiting activity will facilitate the shortlisting of eligible candidates, help to avoid potential incompatibilities of ingredients, and reduce times in the process of designing hybrid coatings for corrosion protection. This study has found that the compounds have significant corrosion protecting effect on steel and zinc and those molecules were shortlisted for our future studies on galvanic hybrid coating of steel.

Cationic Phosphorus Compounds Based on a Bis(1-piperidinyl)-Substituted Carbodiphosphorane: Syntheses, Structures, and Csp3 -H Activation.

The use of the bis(1-piperidinyl)-substituted carbodiphosphorane (Ph2(Pip)P)2C (1) as an NCN ligand for the stabilization of phosphorus cations was studied. A simple ligand for halide exchange allowed the synthesis and isolation of a series of phosphorus monocations of the type [1-PR2]+ (with R = Cl, Br, I, CyCl, Ph). These cations exhibit characteristic NMR and structural properties which nicely correlate with the charge at the central phosphorus atom and the interaction between the ligand and the PR2 moiety. Halide abstraction from the monocations does not result in isolable dicationic compounds but in an unexpected intramolecular Csp3–H activation in the piperidinyl group. DFT studies show that the selective activation of the CH2 group next to the nitrogen atom instead of a CH group at the phenyl substituents proceeds via an iminium intermediate formed by hydride transfer from the carbon atom to the cationic phosphorus center. This observation clearly demonstrates the pronounced π acidity of the dicationic phosphorus species in comparison to compounds with a further π-donor substituent.

Saturated NHC Derived Dichalcogen Dications

Herein, the synthesis and characterization of dicationic dichalcogenide compounds [(SIPr)E]2(OTf)2 (3a‐E) (E = S, Se, Te) based on a saturated N‐heterocyclic carbene (NHC), SIPr [SIPr = C{N(Dipp)CH2}2, Dipp = 2,6‐iPr2C6H3] are reported. Treatment of SIPr (1a) with elemental chalcogens affords the heavier ketone derivatives (SIPr)E (2a‐E), which readily undergo oxidative E–E coupling reactions with triflic anhydride to yield the corresponding products 3a‐E. Compounds 3a‐E are air‐stable crystalline solids and were characterized by NMR and UV/Vis spectroscopy as well as by X‐ray diffraction methods.

Experimental investigation of thermo-physical properties of geminal dicationic ionic compounds for latent thermal energy storage

To enhance thermal stability of ionic compounds and increase thermal storage density, a series of geminal dicationic ionic compounds have been synthesized. The structures of these geminal dicationic ionic compounds were confirmed by 1H NMR and 13C NMR. Besides, thermal stability was determined by thermogravimetric analysis (TGA); melting point, heat of fusion and heat capacity were investigated by differential scanning calorimetry (DSC) for synthetic geminal dicationic ionic compounds. The effects of alkyl side-chain, the H atom at position 2 of the imidazolium ring, and anions on the thermal properties of the geminal dicationic ionic compounds were investigated. Hydrogen bonding in geminal dicationic ionic compounds was studied, in the case of C4(mim)2(Br)2, by single-crystal X-ray diffraction. The thermal analysis results indicate that geminal dicationic ionic compounds show excellent thermal stability. The decomposition temperatures of geminal dicationic ionic compounds can be up to 741.25 K, and the latent heat can reach 115.69 kJ kg−1. It is increased on average by 61.8% and 126.1%, respectively, as compared to alkyl chain ionic compounds (C4mim)Br. It can be expected that these geminal dicationic ionic compounds are suitable for thermal storage applications. Enhanced thermal storage density can thus be achieved by increasing the density and heat capacity. These values are higher than that of the monocationic ionic compounds. It can be expected that these geminal dicationic ionic compounds are suitable for thermal storage applications.

Back Cover: Chalcogen Bonding Catalysis of a Nitro‐Michael Reaction (Angew. Chem. Int. Ed. 47/2019)

Chalcogen bonding is a noncovalent interaction between electrophilic chalcogen substituents and Lewis bases. In their Communication on page 16923 ff., S. M. Huber and co-workers show that dicationic tellurium compounds can act as strong catalysts in a nitro-Michael reaction. This is the first time that a nitro compound has been reported to be activated by halogen bonding or chalcogen bonding. The crucial role of chalcogen bonding was confirmed by comparison experiments.

Dicationic triazolium fungicidal ionic liquids with herbicidal properties

The purpose of the present study was to synthesize the dicationic ionic liquids exhibiting herbicidal and fungicidal activities. A homologue series of ten dicationic ionic liquids was synthesized using commercial triazole fungicide (tebuconazole) and evaluated in terms of their possible antifungal and herbicidal activities. Dicationic triazolium compounds containing different linkers were prepared via acid–base reaction between the corresponding dicationic hydroxides and herbicides in the form of free acids. Additionally, the ionic liquids were fully characterized using NMR and thermal analysis. The herbicidal efficacy was tested during greenhouse experiments, using lambsquarters and oilseed rape as the test plants. In the case of determination of antifungal activity, six fungal species were used: Sclerotinia sclerotiorum, Botrytis cinerea, Fusarium culmorum, Fusarium oxysporum, Colletotrichum sp. and Monographella nivalis. The obtained results indicate that the conversion of compounds into dicationic ionic liquids affects their fungicidal and herbicidal activity. In the case of tests carried out on fungi, no difference in activity was observed at higher doses, except Monographella nivalis. However, at lower concentration (10 ppm), there is a reduction in efficacy compared to the reference substance. In addition, all obtained compounds are characterized by high activity.Graphic abstract

Thermophysical properties of dicationic imidazolium-based ionic compounds for thermal storage

In order to improve the thermal stability of ionic liquids and enhance the thermal storage density, a series of dicationic ionic compounds containing incorporated Br−, BF4−, PF6−, NTf2− anions were synthesized. The structures of these dicationic ionic compounds were confirmed by 1H NMR, 13C NMR and FT-IR. The dicationic ionic compounds' thermo-physical properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effect of molecular configuration on the heat of fusion was studied by changes alkyl side-chain, linkage chain, molecular structure symmetry, and anions. The quantum calculation was carried to validate the number of hydrogen bonds for the dicationic ionic compounds. The results showed that hydrogen bonds significantly increased compared to that of the monocationic ionic liquids (MILs). The thermal analysis results indicate that dicationic ionic compounds exhibit excellent thermal stability; the decomposition temperatures higher than 560 K; the melting points and heat of fusion value reached 481 K and 116.26 kJ·kg−1, respectively. These values are higher than those of the MILs.

Studies on diverse chemical species derived from chalcogen atoms ~ The Footprint of Professor Naomichi Furukawa in Heteroatom Chemistry ~

AbstractThis account summarizes representative contributions of Prof. Naomichi Furukawa to the field of heteroatom chemistry. Ligand‐coupling reactions (LCRs) and ligand‐exchange reactions (LERs) of chalcogen derivatives were developed from reactions of trivalent chalcogen species with organometallic reagents. Prof. Furukawa has also reported a large number of mono‐ and dicationic compounds generated via transannular and intermolecular interactions. Furthermore, the detection and isolation of hypercoordinated chalcogen species bearing only carbon ligands and an efficient method for the synthesis of thiophene S‐oxides and their reactivity are described.

Functional groups in geminal imidazolium ionic compounds and their influence on thermo-physical properties

To enhance the thermal stability of ionic liquids (ILs) and increase the latent heat, the effect of functional groups for geminal dicationic ionic compounds were investigated and compared to that of monocationic ionic liquids (MILs) analogues. A series of new functionalized ionic compounds were synthesized by introducing vinyl group, cyanomethyl group, hydroxyl group, and carboxyl group to the imidazolium cation. The structures of these ionic compounds were confirmed by 1H NMR, 13C NMR and FT-IR. The thermal stability was determined by TGA; the melting temperature, heat of fusion and heat capacity were investigated by DSC for the synthetic ionic compounds. The thermal analysis results indicate that the functionalized ionic compounds show excellent thermal stability. The decomposition temperature and melting temperature can be up to 593.17 K and 484.99 K, respectively, and the latent heat can reach 64.40 KJ·mol−1. It's increased on average by 6.30%, 34.0% and 93.93%, respectively, as compared to alkyl chain ionic liquid (C2mim)Br. In addition, the heat capacity and thermal storage density of the functionalized ionic compounds are higher than those of the MILs. These superior properties are attributed to the additional hydrogen bonds and electrostatic energy in the functionalized ionic compounds.

Resistance to pentamidine is mediated by AdeAB, regulated by AdeRS, and influenced by growth conditions in Acinetobacter baumannii ATCC 17978.

In recent years, effective treatment of infections caused by Acinetobacter baumannii has become challenging due to the ability of the bacterium to acquire or up-regulate antimicrobial resistance determinants. Two component signal transduction systems are known to regulate expression of virulence factors including multidrug efflux pumps. Here, we investigated the role of the AdeRS two component signal transduction system in regulating the AdeAB efflux system, determined whether AdeA and/or AdeB can individually confer antimicrobial resistance, and explored the interplay between pentamidine resistance and growth conditions in A. baumannii ATCC 17978. Results identified that deletion of adeRS affected resistance towards chlorhexidine and 4’,6-diamidino-2-phenylindole dihydrochloride, two previously defined AdeABC substrates, and also identified an 8-fold decrease in resistance to pentamidine. Examination of ΔadeA, ΔadeB and ΔadeAB cells augmented results seen for ΔadeRS and identified a set of dicationic AdeAB substrates. RNA-sequencing of ΔadeRS revealed transcription of 290 genes were ≥2-fold altered compared to the wildtype. Pentamidine shock significantly increased adeA expression in the wildtype, but decreased it in ΔadeRS, implying that AdeRS activates adeAB transcription in ATCC 17978. Investigation under multiple growth conditions, including the use of Biolog phenotypic microarrays, revealed resistance to pentamidine in ATCC 17978 and mutants could be altered by bioavailability of iron or utilization of different carbon sources. In conclusion, the results of this study provide evidence that AdeAB in ATCC 17978 can confer intrinsic resistance to a subset of dicationic compounds and in particular, resistance to pentamidine can be significantly altered depending on the growth conditions.

Bis(2-aminoimidazolines) and Bisguanidines: Synthetic Approaches, Antiparasitic Activity and DNA Binding Properties.

Parasitic diseases caused by protozoan parasites of the genus Trypanosoma and Plasmodium cause some of the deadliest and disabling human infections in tropical and subtropical areas. Diphenyl-based bis(2-phenylimino)imidazolidines and bisguanidines are extremely potent antiparasitic agents against Trypanosoma brucei (etiological agent of African trypanosomiasis) and Plasmodium falciparum (etiological agent of severe malaria). Many of these compounds are also curative in mouse models of stage 1 African trypanosomiasis representing promising leads for the development of antitrypanosomal drugs. In addition, different classes of bis(2-iminoimidazolidines) and bisguanidines have been shown to have antimicrobial activity against other pathogens (e.g. bacteria, fungi, parasitic worms). Due to their structural and physicochemical properties, these dibasic compounds, which are dications at physiological pH, are prone to bind to the minor groove of DNA at AT-rich sites. In several cases, such interaction is thought to be responsible for their antimicrobial activity. In this review, we give a comprehensive view of the synthetic methods used to introduce the 2-aminoimidazoline scaffold in a molecule. Synthetic routes that give access to these cyclic guanidines (i.e. unsubstituted, 1-, 4-, and 5-substituted 2-aminoimidazolines) are detailed. The in vitro and in vivo antiprotozoal activity of bis(2-aminoimidazolines) and bisguanidines against kinetoplastid parasites (T. brucei, T. cruzi, Leishmania), Plasmodium spp. and other pathogens (e.g. ESKAPE bacteria, Candida spp., M. tuberculosis, E. multilocularia) is also reviewed. Finally, the targets that are involved in the antimicrobial activity (e.g. DNA) or other biological activities (e.g. α-adrenergic receptors, imidazoline binding sites, kinases) of this class of dicationic compounds are discussed.

Synthesis and crystal structures of [Ph3PCH2PPh3]I2 di-chloro-methane disolvate and [Ph3PCH2PPh3](BI4)2.

Reaction of BI3 with carbodi-phospho-rane, C(PPh3)2, gives a mixture of the dicationic compounds, methyl-enebis(tri-phenyl-phospho-nium) diiodide di-chloro-methane disolvate, C37H32P22+·2I-·2CH2Cl2 or [Ph3PCH2PPh3]I2·2CH2Cl2 (I), methyl-enebis(tri-phenyl-phospho-nium) bis-(tetra-iodo-borate), C37H32P22+·2BI4- or [Ph3PCH2PPh3](BI4)2 (II). Solvents are the source of the protons at the ylidic C atom. The P-C-P angle is 124.1 (2)° for (I) and 121.7 (3)° for (II), while the two P-C bond lengths are 1.804 (4) and 1.807 (5) Å in (I), and 1.817 (5) and 1.829 (5) Å in (II). In the crystal of (I), the protons of the central P-CH2-P C atom exhibit weak C-H⋯I hydrogen bonds with the respective anions. The anions in turn are linked to the di-chloro-methane solvent mol-ecules by C-H⋯I hydrogen bonds. In the crystal of (II), one of the BI4- anions is linked to a phenyl H atom via a weak C-H⋯I hydrogen bond.