Supramolecular host–guest complexation of Lash's calix[4]azulene with tetraalkylammonium halides and tetrafluoroborate salts: binding and DFT computational studies

Rahman, Shofiur; Zein, Ahmed L.; Shamov, Grigory A.; Thordarson, Pall; Georghiou, Paris E.

doi:10.1039/c5ra07802d

Cited by 14 publications

(10 citation statements)

References 32 publications

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“…Poor yields of impure calix [4]azulene 707d were obtained when 6-phenylazulene was used in these reactions. Calix [4]azulene 707a has been shown to form 1:1 supramolecular complexes with tetraalkylammonium salts, 327 and the related tert-butyl substituted calixazulene 707b formed a 1:1 supramolecular complex with C 60 . 328 Calixazulenes can be considered to be reduced forms of quatyrin, although it is unclear how aromatic macrocycles could be derived from this system.…”

Section: Tri-and Tetracarbaporphyrinoidsmentioning

confidence: 99%

Carbaporphyrinoid Systems

2016

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Following immediately after the serendipitous discovery of N-confused porphyrins, remarkably diverse carbaporphyrinoid systems have been synthesized and investigated. By replacing a pyrrolic unit within the porphyrin framework with cyclopentadiene, indene, azulene, cycloheptatriene, or benzene, new families of porphyrin-like macrocycles were produced. True carbaporphyrins are fully aromatic structures, while benziporphyrins are essentially devoid of macrocyclic aromatic character, and azuliporphyrins fall midway between the two extremes. Monocarbaporphyrinoids are superior organometallic ligands and form stable complexes with copper(III), silver(III), gold(III), nickel(II), palladium(II), platinum(II), rhodium(III), iridium(III), and ruthenium(II). Unusual oxidation reactions have also been discovered, commonly leading to derivatization of the internal carbon atom. In addition, structural rearrangements have been uncovered that allow the conversion of azuliporphyrins into benzocarbaporphyrins, and benziporphyrins into carbaporphyrins. Although less well studied, many examples of dicarbaporphyrinoids have been reported, and these show equally intriguing characteristics. Furthermore, contracted and expanded carbaporphyrinoids have been investigated. Studies in this area provide fundamental insights into the aromatic properties, tautomerization, and reactivity of porphyrins and related macrocyclic systems.

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Section: Tri-and Tetracarbaporphyrinoidsmentioning

confidence: 99%

Carbaporphyrinoid Systems

2016

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“…In contrast to regular porphyrinogens, their heteroanalogues have been explored to a limited extent, − especially in terms of their coordination properties. − Aside from coordination, the junction of a flexible yet stable framework of a porphyrinogen with an aromatic fragment can lead to the generation of a functional molecular device utilized for the recognition of aromatic carbocycles or fullerens. ,− Carbaporphyrinogens represent a subgroup of heteroporphyrinogens in which a carbocyclic fragment is built within the porphyrinogen framework. Carbaporphyrinogens include examples with o -, m -, and p -phenylene rings; , ferrocene; pyrrene; N-confused pyrrole; , naphthalene; and azulene. − The meso -unsubstituted calix[4]azulene was prepared by Lash et al Our efforts have been focused on azulene-containing molecules in which two, , three, or four pyrrole units are substituted by azulene moieties and a porphyrinogen-like structure is usually supplemented with thiophene rings. The exploration of azuliporphyrinogen redox chemistry systems has generated a unique class of di- and tetracarbocations confined in an azuliporphyrinoid frame.…”

Section: Introductionmentioning

confidence: 99%

Coordination-Induced Molecular Tweezing: Ruthenium Clusters Docked at Azuliporphyrinogens

2016

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The reaction of [Ru(CO)] with a series of conformationally flexible thiaazuliporphyrinogens, namely, dithiadiazuli-, thiatriazuli- and tetraazuliporphyrinogen, yielded a series of complexes with two azulene rings coordinated by either Ru(CO) and Ru(CO) or two Ru(CO) clusters. For dithiadiazuliporphyrinogen, three fundamental arrangements were detected, with two clusters being located at the same side or different sides of the meso plane. Coordination altered the electron density on the rings, allowing for dispersion-promoted interactions between coordinated azulenes. To create this face-to-face arrangement, the ligand framework performs a tweezing movement with coordinated azulenes approaching each other. The tweezer-like arrangement of the coordinated azulene rings assists the formation of azulene inclusion complexes as determined by H NMR titration.

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“…The ωB97xD functional [ 25 ] which combines the long range functional ωB97x with the empirical dispersion correction was used with the standard 6-31G(d) basis set [ 26 ]. We had previously described the use of this system in our previous studies in particular, in reference [ 20 ] as being more reliable than the use of B3LYP/6-31G(d) with our systems. Furthermore, for the halide guests and complexes (i.e., for TBACl, TBABr and TBAI) but not with the tetrafluorborate salts, we used relativistic ECPs by Hay and Wadt (LANL) along with the corresponding LANL2DZ basis set augmented with additional d-, p -polarizational functions [ 27 – 30 ].…”

Section: Resultsmentioning

confidence: 99%

“…For the free OPC4A host molecule, initial geometry-optimized determinations were made on the possible major conformations, based upon those previously defined in reference [ 20 ]. Three distinct conformations ( saddle , cone and 1,2-alternate ) shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…We previously used a similar solid-state NMR approach to study the solid-state supramolecular properties of tetra-6- tert -butylcalix[4]azulene ( 4 ) [ 19 ]. Unlike these two studies, however, in our first study on calixazulenes which we reported in 2015, we were able to demonstrate a chloroform solution-state complexation binding study with Lash and Colby’s calix[4]azulene 3 using a series of tetraalkylammonium halides and tetrafluoroborate salts [ 20 ]. This study was also supplemented by DFT studies to support the trends observed in the experimentally-derived binding constants.…”

Section: Introductionmentioning

confidence: 99%

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Calixazulenes: azulene-based calixarene analogues – an overview and recent supramolecular complexation studies

Georghiou¹,

Rahman²,

Alodhayb³

et al. 2018

Beilstein J. Org. Chem.

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Some of the least studied calixarenes are those that consist of azulene rings bridged by -CH2- groups. Since Lash and Colby’s discovery of a simple and convenient method for producing the parent all-hydrocarbon calix[4]azulene, there have been two other all-hydrocarbon calix[4]azulenes which have been synthesized in good yields by their method. This allowed studying their supramolecular properties. This report is of our latest work on the solution-state supramolecular complexation of one of these calix[4]azulenes, namely tetrakis(5,7-diphenyl)calix[4]azulene or “OPC4A”, with several electron-deficient tetraalkyammonium salts. As a result of more recent methods developed by us and others employing Suzuki–Miyaura cross-coupling reactions to produce additional functionalized azulenes, the promise of further greater functionalized calixazulenes lies in store to be investigated.

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Supramolecular host–guest complexation of Lash's calix[4]azulene with tetraalkylammonium halides and tetrafluoroborate salts: binding and DFT computational studies

Abstract: Calix[4]azulene1is shown to be an effective molecular receptor for tetraalkylammonium halide and BF4−salts.

Cited by 14 publications

References 32 publications

Carbaporphyrinoid Systems

Carbaporphyrinoid Systems

Coordination-Induced Molecular Tweezing: Ruthenium Clusters Docked at Azuliporphyrinogens

Calixazulenes: azulene-based calixarene analogues – an overview and recent supramolecular complexation studies

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