A new calix[4]pyrrole-based, dual functional, chemodosimetric sensor was developed and studied as a cyanide selective indicator; complete color bleaching was observed even in the co-presence of an excess of other anions.
Binding straps: Chiral calix[4]pyrroles 1 bearing an (R)‐ or (S)‐binol‐derived strap on one side of the tetrapyrrolic core (see picture) were synthesized and characterized. The resulting systems bind selected chiral carboxylate anions (shown in red) with high affinity in acetonitrile while at the same time exhibiting enantiomeric discrimination. PB=2‐phenylbutyrate.
A strapped calix[4]pyrrole bearing an 1,3-indanedione group at a β-pyrrolic position has been synthesized and studied as a ratiometric cyanide selective chemosensor. A concentration-dependent bleaching of the initial yellow color was observed upon addition of the cyanide anion. The bleaching, which was observed exclusively with the cyanide anion, occurred even in the presence of other anions. Spectroscopic studies provides support for a mechanistic interpretation wherein the cyanide anion forms a complex with the receptor (K = 2.78 × 104 M-1) through a fast equilibrium, which is followed by slow nucleophilic addition to the β-position of the 1,3-indanedione group. A minimum inhibitory effect from other anions was observed, a feature that could be beneficial in the selective sensing of the cyanide anion.
p-p Stackingi so mnipresent not only in nature but in aw ide variety of practical fields appliedt oo ur lives. Becauseo fi ts importance in ap erformance of natural and artificial systems, such as light harvesting system and working layer in device, many researchers have put intensive effort into identifying its underlying nature. However,f or the case of p-p stacked systemsc omposed of antiaromatic units, the understanding of the fundamentalm echanisms is still unclear.H erein, we synthesized an ew type of planar b,b'-phenylene-bridgedh exaphyrin (1.0.1.0.1.0),r eferred as naphthorosarin whichp ossesses the 24p-electronc onjugated pathway.E specially,t he corresponding antiaromaticp orphyrinoid shows the unique property to form dimeric species adopting the face-to-face geometry which is unprecedentedi nc ases of known annulated naphthorosarins. In order to elucidate the intriguing properties derived from the stacked dimer,t he current study focuses on the experimental support to rationalizet he observed p-p interactions betweent he two subunits.
Hybrid calixpyrrole systems are calixpyrrole-like macrocycles that are based on more than one type of small molecule building block. Structurally, these "mixed-breed" macrocycles differ from calixpyrroles in that some pyrrolic units in the latter are replaced by other hetereocyclic units such as furan, thiophene, bipyrrole, and bithiophene. Although several such systems have been reported in recent years, only a few have been studied as possible anion receptors. In this paper, the results of detailed anion binding studies involving several prototypic systems are reported. Taken in concert, these results highlight the fact that some hybrid systems, including compounds 2-5, display anion affinities that are considerably weaker than those of the parent system 1. On the other hand, they also show that compounds 6-8 are good receptors for "Y-shaped" anions, such as carboxylates, and that they bind these species with high affinity. These findings are strongly supported by solid-state structural studies, which reveal an interesting "cross binding mode" for the binding of carboxylate anions by the bis-thiophene, bis-pyrrole system 7.
Peripherally substituted antiaromatic naphthorosarins have been synthesized for the first time. The synthesis was accomplished by acid‐catalyzed condensation of naphthobipyrrole building blocks with aromatic aldehydes. The naphthobipyrrole building blocks were synthesized by simple oxidative coupling of the corresponding pyrrole substituted aromatics. Solid‐state structural analyses of the synthesized naphthorosarins revealed that the presence of meso‐2,6‐dichlorophenyl‐ and 5,6‐difluoro‐substitution substantially alter the geometry and properties of the naphthorosarins. The substituents affect the redox potentials as well and, in turn, the proton‐coupled electron‐transfer processes leading to the formation of one‐ and two‐electron reduced forms of the corresponding naphthorosarins. One particular naphthorosarin that bears both peripheral fluorine and meso‐2,6‐dichlorophenyl substituents forms a stable 25 π‐electron species upon treating with TFA that was characterized by single‐crystal X‐ray diffraction analysis. The current study underscores how structural modifications can be used to fine‐tune the electronic features of naphthorosarins, including stabilization of odd electron species.
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