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Rhodium containing macromolecules calix[4]pyrrole (RhCP) and tetraphenyl porphyrin (RhTPP) were prepared and grafted on the surface of functionalised molecular sieve materials. 1H and 13C NMR, CHNS and mass spectral analyses were used for the structural elucidation of homogeneous organometallic complexes.1H NMR and CHNS analyses confirm the formation of calix[4]pyrrole (CP) and tetraphenyl porphyrin (TPP). The introduction of rhodium ions into the macromolecule is well evident from the disappearance of the 1H NMR signal characteristic of N-H proton (7.1 ppm in CP and ?2.74 ppm in TPP). Furthermore the formation of RhCP and RhTPP complexes is confirmed using CHNS and mass spectral analysis; the data are in line with theoretically calculated values. The grafting of RhCP and RhTPP on a diamino functionalised SBA-15 support was confirmed through low angle XRD, 13C MAS-NMR and SEM-EDAX analysis. Both homogeneous and heterogeneous catalysts were utilized for nitrobenzene reduction. RhCP and RhTPP heterogenized on SBA-15-F showed complete conversion of nitrobenzene with exclusive formation of aniline as a product. The catalytic activities were retained in both the systems even after several runs.

Anionic hydridosilicates are highly reactive and strong hydride donors. In contrast, calix[4]pyrrole hydridosilicate is an entirely water-stable, anionic silicon hydride, which does not show hydridic reactivity. However, it still acts as an electron donor and enables the detection of a single electron transfer process in the reduction chemistry with hydridosilicates. Most important, these unusual properties are imparted by the unique planar structure of its elusive parent neutral silane-substantiating the effect of planar tetracoordinate silicon for the first time.

(Figure Presented) New tricks for an old dog: Calixpyrroles bind anions efficiently and can be transformed into transition-metal complexes only under forcing conditions. Reducing the macrocycle creates a ligand that easily forms classical Werner complexes with copper, nickel, and palladium ions. The metal complexes present an array of four directed hydrogen bonds, which specifically bind the counterions (see picture; blue N, white H, green Cl, red Cu, Ni, or Pd).

The first direct synthesis of ss-unsubstituted meso-decamethylcalix[5] pyrrole from pyrrole and acetone, with moderate yield, is described. The results showed that a bismuth salt was necessary to obtain calix[5]pyrrole, with the best results obtained usingBi(NO3)3.

Abstract: The smallest core expanded calix[4]pyrrole derivative (5) was synthesized via incorporation of an additional sp3meso-carbon at the periphery of the macrocycle. Anion binding study of the macrocycle reveals clearly the effect of core s

We describe the first synthesis of the novel meso-pentaspirocyclohexyl calix[5]pyrrole 2b. Anion-guest properties of the new compound were evaluated with respect to fluoride, chloride, and bromide tetrabutylammonium salts by 1H NMR titration techniques in deuterated dichloromethane at 22 °C by following the induced shifts in the NH resonances upon complexation.

Solvent-extraction studies provide confirming evidence that meso-octamethylcalix[4]pyrrole acts as an ion-pair receptor for cesium chloride and cesium bromide in nitrobenzene solution. The stoichiometry of the interaction under extraction conditions from water to nitrobenzene was determined from plots of the cesium distribution ratios vs cesium salt and receptor concentration, indicating the formation of an ion-paired 1:1:1 cesium:calix[4]pyrrole:halide complex. The extraction results were modeled to evaluate the equilibria inherent to the solvent-extraction system, with either chloride or bromide. The binding energy between the halide anion and the calix[4]pyrrole was found to be about 7 kJ/mol larger for cesium chloride than for the cesium bromide. The ion-pairing free energies between the calix[4]pyrrole-halide complex and the cesium cation are nearly the same within experimental uncertainty for either halide, consistent with a structural model in which the Cs+ cation resides in the calix bowl. These results are unexpected since nitrobenzene is a polar solvent that generally leads to dissociated complexes in the organic phase when used as a diluent in extraction studies of univalent ions. Control studies involving nitrate revealed no evidence of ion pairing for CsNO3 under conditions identical to those where it is observed for CsCl and CsBr.

A long-standing question in porphyrin chemistry is why pyrrole monomers selectively form tetrapyrrolic macrocycles, whereas the corresponding tripyrrolic macrocycles are never observed. Calix[3]pyrrole, a tripyrrolic porphyrinogen-like macrocycle bearing three sp3-carbon linkages, is a missing link molecule that might hold the key to this enigma; however, it has remained elusive. Here we report the synthesis and strain-induced transformations of calix[3]pyrrole and its furan analogue, calix[3]furan. These macrocycles are readily accessed from cyclic oligoketones. Crystallographic and theoretical analyses reveal that these three-subunit systems possess the largest strain energy among known calix[n]-type macrocycles. The ring-strain triggers transformation of calix[3]pyrrole into first calix[6]pyrrole and then calix[4]pyrrole under porphyrin cyclization conditions. The present results help explain the absence of naturally occurring three-pyrrole macrocycles and the fact that they are not observed as products or intermediate during classic porphyrin syntheses.

Themeso-decamethyl-calix[5]pyrrole2bwassynthesizedfromthefuran- basedanalogue1bviathehomologationofthefuranringstopyrrole,anditssolid- statestructurewasdeterminedbyX-raycrystallography:surprisingly, thebindingconstantof2btowardchlorideisfoundtobelowerthan

The present work describes the reaction of triplet dioxygen with the porphyrinogenic calix[4]pyrrolato aluminates to alkylperoxido aluminates in high selectivity. Multiconfigurational quantum chemical computations disclose the mechanism for this spin-forb

meso-Octamethylcalix[4]pyrrole (C4P) enhances sulfate selectivity in solvent extraction by Aliquat 336N, an effect ascribed to the supramolecular preorganization and thermodynamic stability imparted by insertion of the methyl group of the Aliquat cation into the cup of C4P in its cone conformation.

A series of octamethylcalix[4]pyrrole/ruthenium phosphinidene complexes (Na2[1=PR]) can be accessed by phosphinidene transfer from the corresponding RPA (A = C14H10, anthracene) compounds (R = tBu, iPr, OEt, NH2, NMe2, NEt2, NiPr2, NA, dimethylpiperidino). Isolation of the tert-butyl and dimethylamino derivatives allowed comparative studies of their 31P nuclear shielding tensors by magic-angle-spinning solid-state nuclear magnetic resonance spectroscopy. Density functional theory and natural chemical shielding analyses reveal the relationship between the 31P chemical shift tensor and the local ruthenium/phosphorus electronic structure. The general trend observed in the 31P isotropic chemical shifts for the ruthenium phosphinidene complexes was controlled by the degree of deshielding in the δ11 principal tensor component, which can be linked to the σRuP/πRuP? energy gap. A δ22-δ33 crossover effect for R = tBu was also observed, which was caused by different degrees of deshielding associated with polarizations of the σPR and σPR? natural bond orbitals.

Calix[4]pyrrole was found to be high deuterium incorporation and easy-to-make hydrogen-deuterium exchange in β-pyrrolic positions with the 98% sulphuric acid as catalyst in D2O/CH3CN–D2O/CHCl3–D2O. Co

Herein, a new scaffold for anion recognition based on a tripodal tris(pyrrolamide) motif is presented. The receptors were able to bind to a variety of anions with high affinity. Using density functional theory methods, the three-dimensional geometry of the receptor-anion complex was calculated. These calculations show that the receptors bind anions via a preorganized cavity of amide and pyrrole hydrogen bond donor groups. Based on these findings, homochiral tris(pyrrolamide) receptors were prepared, which produced 1.6-fold greater affinity for (S)-(+)-mandelate(R)-(?)-mandelate, demonstrating the ability to differentiate between these enantiomeric anions. The interaction of (S)-(+)-mandelate and (R)-(?)-mandelate within the homochiral receptor was examined by solution NMR spectroscopy and theoretical calculations. These findings indicate that the preorganized positioning of the pyrrole groups and subsequent sterics allows to differentiate between the stereoisomeric anions.

Needless to say, the development of green and sustainable reaction media instead of using volatile organic solvents as well as corrosive and/or expensive catalysts in the new millennium is continuously attracting great attention from the scientific commun

Here we report the preparation of first examples of iridium-based organometallic macromolecules, viz., iridium-tetra (4-carboxyphenyl)porphyrin (IrTCPP), iridium-calix[4]pyrrole (IrCP) iridium-tetraphenylporphyrin (IrTPP), which are effective catalysts for hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) and 1,4-pentanediol under base free conditions. The turnover number in the range of 1220–2850 is evident for the chosen reaction using iridium macromolecule based catalysts. The heterogenization of homogeneous IrTCPP, IrCP, and IrTPP result in stable reactivity of the catalysts for several runs.

Triazole-bearing calixpyrroles (TCPs) were synthesized as artificial anion binding receptors. The additional C-H?X hydrogen bonding interaction induced strong binding affinity towards halide ions. Using this strong binding affinity, Cl- was successfully extracted from the aqueous to organic phase.

A facile and highly efficient protocol has been developed for the synthesis of calix[4]pyrroles and tetraoxaquaterenes, in moderate to high yields by reaction of dialkyl or cycloalkyl ketones with pyrrole and furan catalyzed by tin (IV) chloride. Particul

A facile and efficient protocol is reported for the synthesis of calix[4]pyrroles and N-confused calix[4]pyrroles in moderate to excellent yields by one-pot condensation of ketones and pyrrole in the presence of catalytic amount of nontoxic acidic ionic liquids. In this reaction the products were obtained in short reaction time with selectivity of regular calix[4]pyrroles.

The eco-friendly and selective syntheses of 5-methyl-5-aryldipyrromethanes (1-4) in which aryl is FC6H4 1, ClC6H 5 2, CH3OC6H5 3 and CH 3C6H5 4,

4-(4-Nitrobenzylideneamine)phenol was used in two strategies allowing the highly selective detection of F- and CN-. Firstly, the compound in acetonitrile acts as a chromogenic chemosensor based on the idea that more basic anions cause its deprotonation (c

Condensation of activated functionalized pyrroles with acetone results in asymmetric bis(pyrrole)s, formed via ring annulation. The methodology is somewhat general and can be applied to a variety of ketones, as well as to a range of pyrrolic substrates that do not bear electron-withdrawing groups directly adjacent to the pyrrole ring.

Graphite oxide and graphene oxides have been used as solid catalysts for the synthesis of 5,5-dialkyldipyrromethanes and calix[4]pyrroles in organic and aqueous solutions at room temperature.

Ytterbium(III) triflate has been utilized as a mild Lewis-acid catalyst for the synthesis of various calix[4]pyrroles by the condensation of pyrrole with different ketones in ionic liquids. The calix[41pyrroles were obtained. in high yield under ecofriend

A facile and efficient protocol is reported for the synthesis of calix[4]pyrroles and N-confused calix[4]pyrroles in moderate to excellent yields by reaction of dialkyl or cycloalkyl ketones with pyrrole catalyzed by reusable Amberlyst-15 under eco-friendly conditions.

The synthesis, structure, and anion binding properties of chromogenic octamethylcalix[4]pyrroles (OMCPs) and their N-confused octamethylcalix[4] pyrrole isomers (NC-OMCPs) containing an inverted pyrrole ring connected via α′- and β-positions are described

Porosity and acidity of molecular sieve Al-MCM-41 (ca. 30 Angstroem pore diameter) plays a crucial role in the synthesis of novel calix(4)pyrroles; for the first time, Al-MCM-41 has been used as a solid acid catalyst to produce a number of calix(4)pyrroles with good selectivity and yields where zeolite HY (ca. 7.6 Angstroem pore diameter) yields mainly the linear chain dimer and no cyclic products.

Next to the 'normal' calix[4]pyrrole 1, the N-confused calix[4]pyrrole 2 is formed in substantial amounts (up to 22% yield) as side product in the acid-catalyzed condensation reaction of ketones and pyrrole. In some cases, doubly N-confused calix[4]pyrroles are also formed.