Two π-Electrons Make the Difference: From BODIPY to BODIIM Switchable Fluorescent Dyes

(aza-)BODIPY dyes (boron dipyrromethene dyes) are well-established fluorophores due to their large quantum yields, stability, and diversity, which led to promising applications including imaging techniques, sensors, organic (opto)electronic materials, or biomedical applications. Although the control of the optical properties in (aza-)BODIPY dyes by peripheral functional groups is well studied, we herein present a novel approach to modify the 12 π-electron core of the dipyrromethene scaffold. The replacement of two carbon atoms in the β-position of a BODIPY dye by two nitrogen atoms afforded a 14 π-electron system, which was termed BODIIM (boron diimidazolylmethene) in systematic analogy to the BODIPY dyes. Remarkably, the BODIIM dye was obtained with a BH₂-rigidifying entity, which is currently elusive and highly sought after for the BODIPY dye class. DFT-Calculations confirm the [12+2] π-electron relationship between BODIPY and BODIIM and reveal a strong shape correlation between LUMO in the BODIPY and the HOMO of the BODIIM. The modification of the π-system leads to a dramatic shift of the optical properties, of which the fluorescent emission is most noteworthy and occurs at much larger Stokes shift, that is, ≈500 cm⁻¹ in BODIPY versus >4170 cm⁻¹ in BODIIM system in all solvents investigated. Nucleophilic reactivity was found at the meso-carbon atom in the formation of stable borane adducts with a significant shift of the fluorescent emission, and this behavior contrasts the reactivity of conventional BODIPY systems. In addition, the reverse decomplexation of the borane adducts was demonstrated in reactions with a representative N-heterocyclic carbene to retain the strongly fluorescent BODIIM compound, which suggests applications as fully reversible fluorescent switch.     

Application of 1,4-Diaminoanthraquinone as a New Sensing Material for Fabrication of a Iron(III)-Selective Modified Carbon Paste Electrode

In the present work, a novel sensitive electrochemical potentiometric sensor for sensing Fe³⁺ ions based on 1,4-diaminoanthraquinone (DAQ) as a hydrophobic selector element was prepared to implement as an ion selective carbon paste electrode in the aqueous solutions. The adequate amounts of ionophore (5%), paraffin oil (25%) as a binder, Nanosilica (NS: 0.5%) multi-wall carbon nanotubes (MWCNTs: 1%) as a modifier, and graphite powder (68.5%) as an inert matrix was occupied to form the paste. This new FeCP sensor demonstrated a Nernstian slope of 19.7 ± 0.7 mV per decade over widish linear range between 1.0 × 10^–8 to 1.0 × 10^–2 mol L^–1 at working pH range of 1.9–5.0 in the optimized conditions. The average elapsed time to response of electrode was about ~6 s for concentrations from lower (1.0 × 10^?8 mol L^–1) to higher (1.0 × 10^?2 mol L^–1) of Fe³⁺ ion solution. The selectivity of electrode toward Fe³⁺ ions in comparison with other cations was studied by matched potential method. The making FeCP sensor has been put to use successfully as an indicator electrode in analytical applications such as the potentiometric titration and determination of iron(III) ion in blend of different ions.     

A metal organic framework prepared from benzene-1,3,5-tricarboxylic acid and copper(II), and functionalized with various polysulfides as a sorbent for selective sorption of trace amounts of heavy metal ions

Novel composites were obtained via direct assembly of polysulfides (S_x^2?, X?=?3, 4, 6) on the surface of a metal organic framework (MOF; type benzene-1,3,5-tricarboxylic/Cu(II). They are referred to as S_x-MOFs and were used for highly selective and efficient extraction of ultra-trace amounts of heavy metal ions from aqueous solutions. The structure of the S_x-MOFs was characterized by Raman spectroscopy, FT-IR, X-ray diffraction, and scanning electron microscopy. The Raman spectra of S_x-MOF is similar to the bare MOF and shows the MOFs structure to be well retained after S_x functionalization. The selective interaction of S_x with soft metal ions and the high surface area of MOFs resulted in excellent affinity and selectivity for ions such as Hg(II). The S_x-MOFs of type S₄-MOF had the highest distribution coefficient K_d value (~10⁷) and best extraction recovery (~100%) for Hg(II). The S₄-MOF also has high selectivity in the following order: Hg(II) >?>?Pb(II)?>?Zn(II)?>?Ni(II)?>?Co(II). The binding process of the metals occurs via M–S bonding. The ions were quantified by inductively coupled plasma optical emission spectrometry (ICP-OES). The detection limit for Hg(II) is 0.13 μg L^?1. The S₄-MOF was applied to the extraction of trace metal ions from natural and contaminated waters and data were compared with other sorbets. The results revealed that S₄-MOF is an excellent adsorbent for sorption of heavy metal ions even in the presence of the relatively high concentration of other ions.

Open image in new window

Graphical abstract A composite was synthesized via direct assembly of polysulfides (S_x^2?, X?=?3, 4, 6) on surface of the metal organic framework (S_x-MOF) and was used for selective and efficient extraction of ultra-trace amounts of heavy metal ions from aqueous solutions.

     

Photocatalytic decarboxylative amidosulfonation enables direct transformation of carboxylic acids to sulfonamides

Sulfonamides feature prominently in organic synthesis, materials science and medicinal chemistry, where they play important roles as bioisosteric replacements of carboxylic acids and other carbonyls. Yet, a general synthetic platform for the direct conversion of carboxylic acids to a range of functionalized sulfonamides has remained elusive. Herein, we present a visible light-induced, dual catalytic platform that for the first time allows for a one-step access to sulfonamides and sulfonyl azides directly from carboxylic acids. The broad scope of the direct decarboxylative amidosulfonation (DDAS) platform is enabled by the efficient direct conversion of carboxylic acids to sulfinic acids that is catalyzed by acridine photocatalysts and interfaced with copper-catalyzed sulfur–nitrogen bond-forming cross-couplings with both electrophilic and nucleophilic reagents.

Sulfonamides are now accessible directly from carboxylic acids by a one-step, tricomponent decarboxylative amidosulfonation that provides the missing link between the two key functionalities.     

A Classical Cosmological Model for Triviality

The aim of this paper is to study the triviality of λ ϕ⁴ theory in a classical gravitational model. Starting from a conformal invariant scalar tensor theory with a self-interaction term λ ϕ⁴, we investigate the effect of a conformal symmetry breaking emerging from the gravitational coupling of the large-scale distribution of matter in the universe. Taking in this cosmological symmetry breaking phase the infinite limit of the maximal length (the size of the universe) and the zero limit of the minimal length (the Planck length) implies triviality, i.e. a vanishing coupling constant λ. It suggests that the activity of the self-interaction term λ ϕ⁴ in the cosmological context implies that the universe is finite and a minimal fundamental length exists.     

Rapid and Efficient Synthesis of Imidazolines and Bisimidazolines Under Microwave and Ultrasonic Irradiation

Summary. Small assemblies of 2-imidazolines and bisimidazolines from appropriate nitriles and ethylenediamine with catalytic amounts of P₂S₅ employing a microwave assisted protocol were prepared. Sonication of this system also led to successful synthesis of 2-imidazolines and bisimidazolines. Another advantage of these systems is the ability to carry out large scale reactions.     

Hit-to-Lead Short Peptides against Dengue Type 2 Envelope Protein: Computational and Experimental Investigations

Data from the World Health Organisation show that the global incidence of dengue infection has risen drastically, with an estimated 400 million cases of dengue infection occurring annually. Despite this worrying trend, there is still no therapeutic treatment available. Herein, we investigated short peptide fragments with a varying total number of amino acid residues (peptide fragments) from previously reported dengue virus type 2 (DENV2) peptide-based inhibitors, DN58wt (GDSYIIIGVEPGQLKENWFKKGSSIGQMF), DN58opt (TWWCFYFCRRHHPFWFFYRHN), DS36wt (LITVNPIVTEKDSPVNIEAE), and DS36opt (RHWEQFYFRRRERKFWLFFW), aided by in silico approaches: peptide–protein molecular docking and 100 ns of molecular dynamics (MD) simulation via molecular mechanics using Poisson–Boltzmann surface area (MMPBSA) and molecular mechanics generalised Born surface area (MMGBSA) methods. A library of 11,699 peptide fragments was generated, subjected to in silico calculation, and the candidates with the excellent binding affinity and shown to be stable in the DI-DIII binding pocket of DENV2 envelope (E) protein were determined. Selected peptides were synthesised using conventional Fmoc solid-phase peptide chemistry, purified by RP-HPLC, and characterised using LCMS. In vitro studies followed, to test for the peptides’ toxicity and efficacy in inhibiting the DENV2 growth cycle. Our studies identified the electrostatic interaction (from free energy calculation) to be the driving stabilising force for the E protein–peptide interactions. Five key E protein residues were also identified that had the most interactions with the peptides: (polar) LYS36, ASN37, and ARG350, and (nonpolar) LEU351 and VAL354; these residues might play crucial roles in the effective binding interactions. One of the peptide fragments, DN58opt_8-13 (PFWFFYRH), showed the best inhibitory activity, at about 63% DENV2 plague reduction, compared with no treatment. This correlates well with the in silico studies in which the peptide possessed the lowest binding energy (−9.0 kcal/mol) and was maintained steadily within the binding pocket of DENV2 E protein during the MD simulations. This study demonstrates the use of computational studies to expand research on lead optimisation of antiviral peptides, thus explaining the inhibitory potential of the designed peptides.     

Uniform copper nanoparticles as an inexpensive and efficient catalyst for synthesis of novel β-carbonyl-1, 2, 3-triazoles in water medium

Copper nanoparticles as an efficient, inexpensive catalyst were prepared via ball milling for synthesis of β-carbonyl 1, 2, 3-triazoles from azido alcohol by click reaction in water. An extensive range of raw materials such as sodium azide, phenacyl bromide, epichlorohydrin, and terminal alkynes were used. Complete reduction of CuO in presence of NaBH₄ was done via ball milling with a ball-to-powder weight ratio of 50:1 under air atmosphere at room temperature. The final copper nanoparticles (Cu NPs) were characterized by SEM, EDX, XRD and FT-IR. The Cu NPs catalyzed one-pot three component synthesis of β-carbonyl 1, 2, 3-triazoles at room temperature with short reaction time and high product yields. The catalyst could be easily recovered and reused in several successive runs.

     

Microwave-assisted efficient synthesis of azlactone derivatives using TsCl/DMF under solvent-free conditions

A simple and efficient procedure for the synthesis of azlactones employing condensation reaction of aromatic aldehydes with hippuric acid has been developed by using the tosyl chloride (TsCl) and dimethylformamide (DMF) system as condensing agent in the absence of solvents under microwave irradiation. The present protocol is operationally simple and offers several advantages such as high yields, short reaction time, and simple workup.