Reductive N alkylation of cyclo[8]pyrroles.
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Journal Article↗
Biomedical subjects
Jonathan L Sessler
Publications and source records attributed to Jonathan L Sessler.
Calix[4]pyrrole[2]carbazole: a new kind of expanded calixpyrrole.
The synthesis and anion binding properties of a new class of calixpyrrole analogue, containing two carbazole subunits in lieu of two of the four acetone bridging elements normally found in calix[4]pyrrole, is described. The compound exists in a winglike structure in the solid state, as judged from single-crystal X-ray diffraction analyses of both the free system and the corresponding benzoate anion complex. Evidence for anion binding in dichloromethane solution was obtained from static fluorescent quenching experiments; these latter revealed a slight preference for acetate relative to other carboxylate anions (e.g., benzoate, oxalate, succinate), as well as various other anionic substrates (i.e., chloride and dihydrogen phosphate). No evidence of binding was observed in the case of bromide, nitrate, and hydrogen sulfate.
Calixarenes↗
Calix[4]bipyrrole--a big, flexible, yet effective chloride-selective anion receptor.
Anion binding studies reveal that, in spite of its big size and flexible structure, calix[4]bipyrrole shows strong anion binding in general and good selectivity towards chloride anion in acetonitrile.
Calixarenes↗
Calix[4]phyrins. Effect of peripheral substituents on conformational mobility and structure within a series of related systems.
A new, stepwise synthesis of calix[4]phyrins is described. It relies on the condensation of a ketone with pyrrole to form a dipyrromethane containing a quaternary carbon center that is subsequently condensed with an aromatic aldehyde. This methodology, in contrast to the previous rational approach described by this group (involving formation of a trisubstituted dipyrromethane via the condensation of an aldehyde with pyrrole, followed by condensation of this dipyrromethane with acetone), allows for a variety of bulky, ketone-derived substituents to be incorporated into the meso-like positions. The resulting systems, while all containing the same central macrocyclic core, display conformational properties that reflect the nature of these meso-like substituents; these conformational features were independently assessed by X-ray diffraction analysis, NMR spectroscopy, and quantum chemical calculations.
Calixarenes↗
Synthesis and characterization of a discotic uranium-containing liquid crystal.
The synthesis of several UO(2)-alaskaphyrin derivatives functionalized with aliphatic chains is described. These compounds are found to be liquid-crystalline and form columnar mesophases, as judged from polarizing optical microscopy studies, and represent the first uranium-containing discotic mesogens.
Journal Article↗
Enhancing Hoogsteen interactions: a pyrrole-containing purine nucleoside that competes with guanosine self-assembly.
A pyrrole-appended purine nucleoside 1 is described that can form an "extended" three-point Hoogsteen-type interaction due to the stabilization of the donor-acceptor-acceptor (DAA) motif. Nucleoside 1 is shown to bind guanosine 10 (a classic ADD motif) to form ensemble I. This interaction competes effectively with guanosine self-assembly and, as such, is capable of disrupting guanosine quadruplex formation.
Binding, Competitive↗
Synthesis and study of a new diamidodipyrromethane macrocycle. An anion receptor with a high sulfate-to-nitrate binding selectivity.
A new 2,6-diamidopyridinedipyrromethane hybrid macrocycle () has been synthesized that shows a high selectivity for dihydrogen phosphate and hydrogen sulfate relative to nitrate in acetonitrile solution as judged from UV-vis spectrophotometric titrations; this leads to the suggestion that this or related systems might find use in nuclear waste remediation applications requiring the selective removal of hydrogensulfate from nitrate-rich waste mixtures.
Journal Article↗
Octaethylporphyrin and expanded porphyrin complexes containing coordinated BF2 groups.
In contrast to octaethylporphyrin, which forms a very labile bis-BF(2) complex, treatment of the hexa- and octapyrrolic expanded porphyrins amethyrin and [32]octaphyrin with BF(3).Et(2) under standard reaction and work-up conditions gives rise to stable, non-labile mono- and bis-BF(2) complexes; these were readily characterised by, inter alia, X-ray diffraction analyses.
Boron Compounds↗
Synthesis of 2,2'-bipyrroles and 2,2'-thienylpyrroles from donor-acceptor cyclopropanes and 2-cyanoheteroles.
[reaction: see text] Two new series of 2,2'-bipyrroles and 2,2'-thienylpyrroles have been prepared by trimethylsilyl trifluoromethanesulfonate (TMSOTf)-mediated reaction of donor-acceptor cyclopropanes with 2-cyanopyrroles and 2-cyanothiophene, respectively. This method opens the door toward a wide variety of unsymmetrical bipyrroles and thienylpyrroles.
Cyclopropanes↗
Cytosine-substituted metalloporphyrins: receptors for recognition of nucleotides in ion-selective electrodes.
A new series of cytosine-substituted metalloporphyrin conjugates (containing Co(II) and Zn(II) as the coordinated metals) were designed and investigated as nucleotide receptors in PVC-membrane-based ion-selective electrodes under neutral conditions. The potentiometric results indicate that these systems, in particular the Co(II)-containing complex, may be potentially useful sensors for complementary nucleotide substrates in the presence of 10 mol% tridodecylmethylammonium chloride (K(Pot.)(5'-GMP/5'-AMP)= 0.045).
Biosensing Techniques↗
Calix[4]pyrrole Schiff base macrocycles. Novel binucleating ligands for mu-oxo iron complexes.
New bimetallic mu-oxo diferric complexes of several previously reported calix[4]pyrrole Schiff base macrocycles are described. The synthesis of a new member of this class of macrocycles is also reported; it was prepared via an acid-catalyzed condensation between 1,9-bisformyl-5,5-dipropyldipyrromethane and o-phenylenediamine. Reactions of the free base macrocycles or their bis-HCl salts with Fe(II) mesitylene, followed by air oxidation, gave the binuclear mu-oxo bis-Fe(III) compounds 6-10 in moderate yield. X-ray crystallography data reveal two different coordination environments for the Fe-O-Fe subunit in 6-10 that it is suggested can be controlled by altering the reaction conditions. Structural properties of these metalated pyrrolic macrocycles are also compared to those of mu-oxo diferric porphyrins and mu-oxo diferric texaphyrin. Complexes 6-10 exhibit two distinct types of M-N bonds that are similar in length to the bonds observed in metallotexaphyrin complexes. However, the electronics of the present systems are very different from those of texaphyrins and porphyrins in that no delocalized bonding patterns are observed within the ligands as a whole.
Benzene Derivatives↗
Biodistribution assessment of a lutetium(III) texaphyrin analogue in tumor-bearing mice using NIR Fourier-transform Raman spectroscopy.
The use of near-infrared (NIR)-excited Fourier-transform (FT) Raman spectroscopy as a technique for evaluating the extent of photosensitizer localization in tumor (human pancreatic adenocarcinomas)-bearing mice has been tested using lutetium(III) texaphyrin analogue Lu-T2B2Tex. The complex was injected subcutaneously in the form of three injections given during the course of 3 days. The kinetics of biodistribution were then followed over a time scale of 1-6 days. The NIR-FT-Raman spectra of tissue samples obtained from the xenographic tumor, muscle, heart, brain, liver, spleen, kidney and blood were recorded and used to identify the presence of Lu-T2B2Tex in these tissues. Five Raman sensitizer markers were used to estimate the relative content of Lu-T2B2Tex in tumor at various postinjection times. UV-Visible (Vis) absorption spectroscopic detection of this sensitizer in tissue extracts was applied as a conventional method. Both spectroscopic methods were in good agreement with each other and confirm that Lu-T2B2Tex localizes well in tumor tissue. Maximal drug content was observed 3 days after the final injection. This time delay seems to be optimal for tumor irradiation in photodynamic therapy.
Adenocarcinoma↗
Water soluble sapphyrins: potential fluorescent phosphate anion sensors.
As part of an ongoing effort to study the anion binding properties of sapphyrins in various media, a number of previously reported water solubilized sapphyrins were studied in methanol and in buffered, neutral aqueous solutions and found to undergo self-aggregation under these solution phase conditions. The nature of the species produced as the result of self-aggregation and the processes leading to their formation were studied via UV-vis absorbance and fluorescence spectroscopy. In previous work (V. Král, H. Furuta, K. Shreder, V. Lynch, and J. L. Sessler, J. Am. Chem. Soc. 1996, 118 1595-1607) it was found that the addition of phosphate-type anions to water soluble sapphyrins at pH 6.1 gives rise to visible spectroscopic changes consistent with the binding to the aggregated form and the concurrent formation of an anion-bound dimer with effective equilibrium constants on the order of 100-300 M(-1). In this study we show that at high phosphate-to-sapphyrin ratios in neutral, buffered aqueous solutions further deaggregation occurs to produce an anion-bound monomeric form. This highly fluorescent species is formed with effective equilibrium constants on the order of 6-19 M(-1) leading to considerations that sapphyrins could function as fluorescent phosphate anion sensors. In an effort to modulate the deaggregation properties, several new sapphyrin derivatives bearing two meso aryl substituents were prepared and studied. The aggregation properties of these latter systems were analyzed in methanol and, in the case of one water solublized system, in neutral aqueous media. In analogy to what was observed for the beta-alkyl substituted sapphyrins, H-type aggregates were seen for the water solubilized meso-substituted system in aqueous media. However, in contrast to the H-type dimers seen in the case of the meso-free systems in methanol, J-type dimers were observed in the case of the sapphyrins bearing two meso substituents in this solvent. The effective dimerization constants of several of the meso-diaryl sapphyrins were determined in methanol as were their pKa values in aqueous media. The solid state structure of the bis HBr salt of one of the meso-diaryl sapphyrins, specifically 10,15-bis(3,5-di-tert-butylphenyl)-3,22-diethyl-2,23-dimethylsapphyrin, was also determined and found to show elements in common with those of previously reported sapphyrin derivatives. In particular, the two counter anions were found to be hydrogen bound above and below the diprotonated sapphyrin plane.
Anions↗
Calix[2]bipyrrole[2]furan and calix[2]bipyrrole[2]thiophene: new pyrrolic receptors exhibiting a preference for carboxylate anions.
Heterocycles other than pyrrole, specifically bipyrrole, furan, and thiophene, have been used to construct two new, calixpyrrole-like anion receptors; binding studies, carried out by ITC in CH3CN, reveal a selectivity for "Y-shaped" anions, such as benzoate, over spherical ones, such as chloride.
Anions↗
Synthetic expanded porphyrin chemistry.
Expanded porphyrins are synthetic analogues of the porphyrins, and differ from these and other naturally occurring tetrapyrrolic macrocycles by containing a larger central core with a minimum of 17 atoms, while retaining the extended conjugation features that are a hallmark of these quintessential biological pigments. The result of core expansion is to produce systems with novel spectral and electronic features, interesting and, often unprecedented, cation-coordination properties, and, in many cases, an ability to bind anions in certain protonation states. Also adding to the appeal of expanded porphyrins is their central role in addressing issues of aromaticity. In many cases, they also display structural features, such as decidedly nonplanar "figure-eight" motifs, that have no antecedents in the chemistry of porphyrins or related macrocyclic compounds. In this Review, the various synthetic approaches now being employed to produce expanded porphyrins as well as their various applications-related aspects are discussed.
Journal Article↗
Pyrazine analogues of dipyrrolylquinoxalines.
[structure: see text]. The synthesis of novel pyrazine derivatives bearing pyrrolic substituents is reported; the ability of these systems to bind certain biologically relevant anions in dichloromethane is also detailed.
Crystallography, X-Ray↗
The first liquid-crystalline, expanded porphyrins.
Aliphatic derivatives of hydrazinophyrin, a new type of tetrapyrrolic macrocycle prepared by the condensation of 2,5-diformylpyrroles with hydrazine, exhibit liquid crystalline properties as judged from polarising optical microscopy; these hydrazinophyrins appear to be the first mesogens derived from an expanded porphyrin core.
Journal Article↗
Fluorinated calixpyrroles: anion-binding extractants that reduce the Hofmeister bias.
Beta-octafluoro-meso-octamethylcalix[4]pyrrole (1) and beta-decafluoro-meso-decamethylcalix[5]pyrrole (2) were found to extract caesium salts of smaller anions (bromide and chloride for 1 and nitrate for 2) as effectively as that of iodide into nitrobenzene (NB) thereby overcoming the Hofmeister bias normally observed for processes of this type.
Journal Article↗