Oligopyrrole macrocycles: receptors and chemosensors for potentially hazardous materials

Relativistic DFT and experimental studies of mono- and bis-actinyl complexes of an expanded Schiff-base polypyrrole macrocycle

Relativistic DFT calculations present accurate geometries of complexes and redox properties, confirmed by the newly-developed experimental syntheses.

High-affinity anion binding by steroidal squaramide receptors

Exceptionally powerful anion receptors have been constructed by placing squaramide groups in axial positions on a steroidal framework. The steroid preorganizes the squaramide NH groups such that they can act cooperatively on a bound anion, while maintaining solubility in nonpolar media. The acidic NH groups confer higher affinities than previously-used ureas or thioureas. Binding constants exceeding 10(14)  M(-1) have been measured for tetraethylammonium salts in chloroform by employing a variation of Cram's extraction procedure. The receptors have also been studied as transmembrane anion carriers in unilamellar vesicles. Unusually their activities do not correlate with anion affinities, thus suggesting an upper limit for binding strength in the design of anion carriers.

Efficient Synthesis of Terpyrrole Derivatives by a Pseudo-Five-Component Reaction between Pyrrole, β-Enaminocarbonyls and Arylglyoxals

Pyrrole reacts with arylglyoxal monohydrates and enaminoketones or enaminoesters in alcoholic media in the presence of FeBr3 as a catalyst to produce 2,5-bis(1H-pyrrol-2-yl)-1H-pyrrole derivatives in high yields as the only product. Reactions are clean and products are isolated by simple filtration.

Self-assembled discrete molecules for sensing nitroaromatics

Efficient sensing of trace amount nitroaromatic (NAC) explosives has become a major research focus in recent time due to concerns over national security as well as their role as environment pollutants. NO2 -containing electron-deficient aromatic compounds, such as picric acid (PA), trinitrotoluene (TNT), and dinitrotoluene (DNT), are the common constituents of many commercially available chemical explosives. In this article, we have summarized our recent developments on the rational design of electron-rich self-assembled discrete molecular sensors and their efficacy in sensing nitroaromatics both in solution as well as in vapor phase. Several π-electron-rich fluorescent metallacycles (squares, rectangles, and tweezers/pincers) and metallacages (trigonal and tetragonal prisms) have been synthesized by means of metal-ligand coordination-bonding interactions, with enough internal space to accommodate electron-deficient nitroaromatics at the molecular level by multiple supramolecular interactions. Such interactions subsequently result in the detectable fluorescence quenching of sensors even in the presence of trace quantities of nitroaromatics. The fascinating sensing characteristics of molecular architectures discussed in this article may enable future development of improved sensors for nitroaromatic explosives.

Solution and solid-phase halogen and C-H hydrogen bonding to perrhenate

(1)H NMR spectroscopic and X-ray crystallographic investigations of a 1,3-bis(4-ethynyl-3-iodopyridinium)benzene scaffold with perrhenate reveal strong halogen bonding in solution, and bidentate association in the solid state. A nearly isostructural host molecule demonstrates significant C-H hydrogen bonding to perrhenate in the same phases.

Fluorescent and colorimetric ion probes based on conjugated oligopyrroles

In this tutorial review, the design strategies, syntheses, and ion sensing properties of conjugated oligopyrroles are described.

Superior perrhenate anion recognition in water by a halogen bonding acyclic receptor

The first example of perrhenate anion binding and fluorescence sensing in water by a halogen bond donor is reported.

Preparation of dipyrrins from F-BODIPYs by treatment with methanesulfonic acids

Compatible with highly reactive functionalities workable with strongly electron-poor starting products.

Synthesis, spectroscopy studies, and theoretical calculations of new fluorescent probes based on pyrazole containing porphyrins for Zn(II), Cd(II), and Hg(II) optical detection

New pyrazole-porphyrin conjugates were successfully prepared from a reaction of β-porphyrin-chalcone derivatives with phenylhydrazine in acetic acid followed by an oxidative step. This fast and efficient synthetic approach provided the expected compounds in yields up to 82%. The sensing ability of the new porphyrin-pyrazole derivatives to detect the metal ions Ag(+), Na(+), K(+), Mg(2+), Ca(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Cr(3+) was studied by spectrophotometric and spectrofluorimetric titrations. In the presence of Zn(2+), the conjugates exhibit changes in the emission spectra that are desired for a ratiometric-type fluoroionophoric detection probe. The studies were extended to gas phase, where the pyrazole-porphyrin conjugates show ability to sense metal ions with high selectivity toward Cu(2+) and Ag(+), and in poly(methyl methacrylate) doped films with promising results for Zn(2+) detection.

De Proft F. Exploring the structure–aromaticity relationship in Hückel and Möbius N-fused pentaphyrins using DFT

Fine-tuning of the molecular topology and macrocyclic aromaticity of N-fused pentaphyrins by changing the number of π electrons and meso-substituents.

Fluorescent sensing of 99Tc pertechnetate in water

The fluorescent cage senses pertechnetate in water at μM concentration, opening perspectives to detect the pollutant without radioanalytical instrumentation.

Switchable π-coordination and C–H metallation in small-cavity macrocyclic uranium and thorium complexes

Actinide complexes of a small-cavity, dipyrrolide macrocycle exhibit unusual bent metallocene-type binding, or bis(arene)-type binding, or both at once in a di-uranium adduct.

Crossed and linked histories of tetrapyrrolic macrocycles and their use for engineering pores within sol-gel matrices

The crossed and linked histories of tetrapyrrolic macrocycles, interwoven with new research discoveries, suggest that Nature has found in these structures a way to ensure the continuity of life. For diverse applications porphyrins or phthalocyanines must be trapped inside solid networks, but due to their nature, these compounds cannot be introduced by thermal diffusion; the sol-gel method makes possible this insertion through a soft chemical process. The methodologies for trapping or bonding macrocycles inside pristine or organo-modified silica or inside ZrO₂ xerogels were developed by using phthalocyanines and porphyrins as molecular probes. The sizes of the pores formed depend on the structure, the cation nature, and the identities and positions of peripheral substituents of the macrocycle. The interactions of the macrocyclic molecule and surface Si-OH groups inhibit the efficient displaying of the macrocycle properties and to avoid this undesirable event, strategies such as situating the macrocycle far from the pore walls or to exchange the Si-OH species by alkyl or aryl groups have been proposed. Spectroscopic properties are better preserved when long unions are established between the macrocycle and the pore walls, or when oligomeric macrocyclic species are trapped inside each pore. When macrocycles are trapped inside organo-modified silica, their properties result similar to those displayed in solution and their intensities depend on the length of the alkyl chain attached to the matrix. These results support the prospect of tuning up the pore size, surface area, and polarity inside the pore cavities in order to prepare efficient catalytic, optical, sensoring, and medical systems. The most important feature is that research would confirm again that tetrapyrrolic macrocycles can help in the development of the authentic pore engineering in materials science.