The Resorcinarene Hexameric Capsule as a Supramolecular Photoacid to Trigger Olefin Hydroarylation in Confined Space

The self-assembled resorcinarene capsule C6 shows remarkable photoacidity upon light irradiation, which is here exploited to catalyze olefin hydroarylation reactions in confined space. An experimental pKa* value range of -3.3--2.8 was estimated for the photo-excited hexameric capsule C6*, and consequently an increase in acidity of 8.8 log units was observed with respect to its ground state (pKa=5.5-6.0). This makes the hexameric capsule the first example of a self-assembled supramolecular photoacid. The photoacid C6* can catalyze hydroarylation reaction of olefins with aromatic substrates inside its cavity, while no reaction occurred between them in the absence of irradiation and/or capsule. DFT calculations corroborated a mechanism in which the photoacidity of C6* plays a crucial role in the protonation step of the aromatic substrate. A further proton transfer to olefin with a concomitant C-C bond formation and a final deprotonation step lead to product releasing.

Insights into the Friedel-Crafts Benzoylation of N-Methylpyrrole inside the Confined Space of the Self-Assembled Resorcinarene Capsule

Friedel-Crafts benzoylation of N-methylpyrrole 2 can run inside the confined space of the hexameric resorcinarene capsule C. The bridged water molecules at the corner of C act as H-bonding donor groups to polarize the C-Cl bond of benzoyl chlorides 3a-f. Confinement effects on the regiochemistry of the FC benzoylation of N-methylpyrrole are observed. The nature of the para-substituents of 3a-f and their ability to establish H-bonds with the water molecules of C work synergistically with the steric constrictions imposed by the capsule to drive the regiochemistry of products 4a-f. QM investigations indicate that inside the cavity of C, the FC benzoylation of 2 has a bimolecular concerted SN2 mechanism, appropriately, above-plane nucleophilic vinylic substitution (SNVπ)─supported by H-bonding interactions between water molecules and both the leaving Cl atom and the carbonyl group.

Hexahexyloxycalix[6]arene, a Conformationally Adaptive Host for the Complexation of Linear and Branched Alkylammonium Guests

Hexahexyloxycalix[6]arene 2b leads to the endo-cavity complexation of linear and branched alkylammonium guests showing a conformational adaptive behavior in CDCl₃ solution. Linear n-pentylammonium guest 6a⁺ induces the cone conformation of 2b at the expense of the 1,2,3-alternate, which is the most abundant conformer of 2b in the absence of a guest. In a different way, branched alkylammonium guests, such as tert-butylammonium 6b⁺ and isopropylammonium 6c⁺, select the 1,2,3-alternate as the favored 2b conformation (6b⁺/6c⁺⊂2b^1,2,3-alt), but other complexes in which 2b adopts different conformations, namely, 6b⁺/6c⁺⊂2b^cone, 6b⁺/6c⁺⊂2b^paco, and 6b⁺/6c⁺⊂2b^1,2-alt, have also been revealed. Binding constant values determined via NMR experiments indicated that the 1,2,3-alternate was the best-fitting 2b conformation for the complexation of branched alkylammonium guests, followed by cone > paco > 1,2-alt. Our NCI and NBO calculations suggest that the H-bonding interactions (⁺N-H···O) between the ammonium group of the guest and the oxygen atoms of calixarene 2b are the main determinants of the stability order of the four complexes. These interactions are weakened by increasing the guest steric encumbrance, thus leading to a lower binding affinity. Two stabilizing H-bonds are possible with the 1,2,3-alt- and cone-2b conformations, whereas only one H-bond is possible with the other paco- and 1,2-alt-2b stereoisomers.

Confused-Prism[5]arene: a Conformationally Adaptive Host by Stereoselective Opening of the 1,4-Bridged Naphthalene Flap

The confused-prism[5]arene macrocycle (c-PrS[5]^Me ) shows conformational adaptive behavior in the presence of ammonium guests. Upon guest inclusion, the 1,4-bridged naphthalene flap reverses its planar chirality from pS to pR (with reference to the pS(pR)₄ enantiomer). Stereoselective directional threading is also observed in the presence of directional axles, in which up/down stereoisomers of homochiral (pR)₅ -c-PrS[5]^Me pseudorotaxanes are formed.

Molecular Recognition in an Aqueous Medium Using Water-Soluble Prismarene Hosts

The synthesis of water-soluble prism[n]arenes (n = 5 and 6) bearing anionic carboxylato groups on the rims is described. The binding properties of this novel class of water-soluble hosts are studied by nuclear magnetic resonance and calorimetry. The complexation of singly and doubly charged ammonium guests with the more rigid pentamer is enthalpically driven by secondary interactions, while the thermodynamic fingerprint for the larger hexamer reveals driving forces that strongly depend on the guest charge and/or size.

Carbocation catalysis in confined space: activation of trityl chloride inside the hexameric resorcinarene capsule

The hexameric resorcinarene capsule is able to promote carbocation catalysis inside its cavity.

Supramolecular catalysis in confined space: making the pyrogallol[4]arene capsule catalytically active in non-competitive solvent

The confined space inside the hexameric pyrogallol[4]arene capsule (CP6) has been exploited for the catalysis of the 1,3-dipolar cycloaddition (1,3-DC) between the proline-based iminium derivative I and nitrone 3, in the presence of the non-competitive benzene solvent.

Unusual Calixarenes Incorporating Chromene and Benzofuran Moieties Obtained via Propargyl Claisen Rearrangement

Monopropargyloxy-tripropoxy-calix[4]arene 1 was subjected to a propargyl Claisen rearrangement to give unusual calix[3]arene[1]chromene and homocalix[3]arene[1]benzofuran macrocycles. Quantum mechanical density functional theory calculations indicated that an initial [3,3] sigmatropic reaction affords a highly reactive allene intermediate, stabilized by two main diradical pathways leading to six- and five-membered oxygenated rings. In the presence of a n-butylammonium guest, calix[3]arene[1]chromane 6 forms two stereoisomeric complexes stabilized by ⁺N–H···O and cation···π interactions.

per-Hydroxylated Prism[n]arenes: Supramolecularly Assisted Demethylation of Methoxy-Prism[5]arene

Methoxy-prism[5]arene PrS[5]^Me is demethylated by a supramolecularly assisted reaction. In the presence of a tetramethylammonium cation, PrS[5]^Me is demethylated by BBr₃ in high yield, while in its absence a 55/40 mixture of PrS[5]^OH/PrS[6]^OH is formed. The dealkylation of prismarenes, such as PrS[6]^R (R = Et, nPr) and c-PrS[5]^Me, can be easily obtained in high yields in the presence of BBr₃.

Chromogenic Properties of p-Pyridinium- and p-Viologen-Calixarenes and Their Cation-Sensing Abilities

The synthesis of calix[4]- and -[6]arene derivatives P6(H)₂²⁺·(Cl^–)₂, V4(H)₂⁴⁺·(Cl^–)₂·(I^–)₂, and V6(H)₂⁴⁺·(Cl^–)₂·(I^–)₂ bearing N-linked pyridinium (P) and viologen (V) units at the upper rim is described here. A rare example of an anionic conformational template is reported for p-pyridiniumcalix[6]arene P6(H)₂²⁺, which adopts a 1,3,5-alternate conformation in the presence of chloride anions. Derivatives P6(H)₂²⁺·(Cl^–)₂, V6(H)₂⁴⁺·(Cl^–)₂·(I^–)₂, and V4(H)₂⁴⁺·(Cl^–)₂·(I^–)₂ show a negative solvatochromism, while their UV–vis acid–base titration evidenced that upon addition of a base, new bands appear at 487, 583, and 686 nm, respectively, due to the formation of betainic monodeprotonated species P6(H)₁⁺, V6(H)₁³⁺, and V4(H)₁³⁺. These new bands were attributable to the intramolecular charge-transfer (CT) transition from the phenoxide to the pyridinium or viologen moiety and were responsive to the presence of cations. In fact, the band at 487 nm of P6(H)₁⁺ was quenched in the presence of a hard Li⁺ cation, and the color of its acetonitrile solution was changed from pink to colorless upon addition of LiI. Consequently, this derivative can be considered as a useful host for the recognition and sensing of lithium cations.

An intramolecularly self-templated synthesis of macrocycles: self-filling effects on the formation of prismarenes

Ethyl- and propyl-prism[6]arenes are obtained in high yields and in short reaction times, independent of the nature and size of the solvent, in the cyclization of 2,6-dialkoxynaphthalene with paraformaldehyde. PrS[6]Et or PrS[6]nPr adopt, both in solution and in the solid state, a folded cuboid-shaped conformation, in which four inward oriented alkyl chains fill the cavity of the macrocycle. On these bases, we proposed that the cyclization of PrS[6]Et or PrS[6]nPr occurs through an intramolecular thermodynamic self-templating effect. In other words, the self-filling of the internal cavity of PrS[6]Et or PrS[6]nPr stabilizes their cuboid structure, driving the equilibrium toward their formation. Molecular recognition studies, both in solution and in the solid state, show that the introduction of guests into the macrocycle cavity forces the cuboid scaffold to open, through an induced-fit mechanism. An analogous conformational change from a closed to an open state occurs during the endo-cavity complexation process of the pentamer, PrS[5]. These results represent a rare example of a thermodynamically controlled cyclization process driven through an intramolecular self-template effect, which could be exploited in the synthesis of novel macrocycles.

Poly(Ethylene Glycol)/β-Cyclodextrin Pseudorotaxane Complexes as Sustainable Dispersing and Retarding Materials in a Cement-Based Mortar

Pseudorotaxane complexes between β-CD and mPEG derivatives bearing a carboxylic acid function (mPEG-COOH) were synthesized and investigated for their dispersing properties in a cement-based mortar. The formation of mPEG-COOH derivatives and their pseudorotaxanes was investigated by 1D nuclear magnetic resonance, diffusion ordered spectroscopy, and thermogravimetric analysis experiments. Mortar tests clearly indicate that mPEG-COOH@β-CD-interpenetrated supramolecules show excellent dispersing abilities. In addition, the supramolecular complexes show a retarding effect, analogously to other known β-CD-based superplasticizers in which the β-CD is covalently grafted on a polymeric backbone.

Expanding Coefficient: A Parameter To Assess the Stability of Induced-Fit Complexes

Here we propose a new parameter, the Expanding Coefficient (EC), that can be correlated with the thermodynamic stability of supramolecular complexes governed by weak secondary interactions and obeying the induced-fit model. The EC values show a good linear relationship with the log Kapp of the respective pseudorotaxane complexes investigated. According to Cram's Principle of Preorganization, the EC can be considered an approximate mechanical measure of the host's reorganization energy cost upon adopting the final bound geometry.

Multivalent resorcinarene clusters decorated with DAB-1 inhitopes: targeting Golgi α-mannosidase from Drosophila melanogaster

Resorcinarene@DAB-1 clusters show a remarkable multivalent effect towards GMIIb over other α-mannosidases, due to a rebinding mechanism: two DAB-1 units of the cluster bind the two Zn-sites of the dimeric protein in an alternate way.

Influence of exo-Adamantyl Groups and endo-OH Functions on the Threading of Calix[6]arene Macrocycle

Calix[6]arenes bearing adamantyl groups at the exo-rim form pseudorotaxanes with dialkylammonium axles paired to the weakly coordinating [B(Ar^F)₄]⁻ anion. The exo-adamantyl groups give rise to a more efficient threading with respect to the exo-tert-butyl ones, leading to apparent association constants more than one order of magnitude higher. This improved stability has been ascribed to the more favorable van der Waals interactions of exo-adamantyls versus exo-tert-butyls with the cationic axle. Calix[6]arenes bearing endo-OH functions give rise to a less efficient threading with respect to the endo-OR ones, in line with what was known from the complexation of alkali metal cations.

Kinetic and Thermodynamic Modulation of Dynamic Imine Libraries Driven by the Hexameric Resorcinarene Capsule

The composition of dynamic covalent imine libraries (DCL) adapts to the presence of the hexameric resorcinarene capsule. In the presence of the self-assembled capsule, a kinetic and thermodynamic modulation of the imine constituents of the DCLs was observed, which was induced by an unusual predatory action of the capsule on specific imine constituents. More complex 2 × 2 DCLs also adapt to the presence of the hexameric capsule, showing a thermodynamic and kinetic modulation of the constituents induced by the predatory action of the capsule. By cross-referencing experimental data, a good selectivity (up to 66%) for one constituent can be induced in a 2 × 2 DCL.

Calix[2]naphth[2]arene: A Class of Naphthalene-Phenol Hybrid Macrocyclic Hosts

Calix[2]naphth[2]arenes make up a new class of phenol–naphthalene hybrid macrocycles. X-ray studies show that calix[2]naphth[2]arene 1 adopts a 1,2-alternate conformation. Alkali metal cations are complexed by the calixnaphtharenes in a 1,2-alternate conformation, by cation···π interactions with the naphthalene walls, and by RO···M⁺ ion–dipole interactions. In the presence of Cs⁺, chiral complexes of calixnaphtharenes 5 and 6 were observed in which the cation is nested on one of the two faces of the macrocycle.

Dispersing and Retarding Properties of Water-Soluble Tetrasulfonate Resorcin[4]arene and Pyrogallol[4]arene Macrocycles in Cement-Based Mortar

Water-soluble tetrasulfonate resorcin[4]arene (1a and 1c) and pyrogallol[4]arene (1b) macrocycles were synthesized and investigated for their dispersing properties in cement-based mortars. Mortar tests clearly show that these polyhydroxylated macrocycles (nonpolymeric) work as cement dispersants. Setting time determinations indicate that the macrocycles 1a and 1b show a retarding effect that is reminiscent of the behavior of superplasticizers (SPs) functionalized with polyhydroxylated β-CDs. Finally, the addition of sulfate anions to the cement paste does not affect the dispersing abilities of 1b, probably due to the sulfate anion capture by H-bonding interactions with its OH groups at the upper rim.

Systemic Immunosuppression Is Highly Effective in the Long-term Control of Inflammatory non-infectious Uveitic Choroidal Neovascularization: A Comparative Study

Purpose: To compare immediate versus delayed introduction of immunosuppressives for naive noninfectious inflammatory choroidal neovascularization (iCNV).Methods: a retrospective, consecutive, comparative, interventional case series of patients with a diagnosis of inflammatory CNV and a minimum follow of 36 months. Patients were divided into two groups: Group A received Immunosuppressives if needed, while Group B since baseline. Both groups received systemic steroids and intravitreal ranibizumab since baseline. Primary end point was to compare the BCVA outcome till 36-month follow-up.Results: Twenty-nine eyes with iCNV were enrolled. In the long term, best-corrected visual acuity (BCVA) was significantly better in group B. At 3-month follow-up, Group B reduced steroids <10 mg/day significantly (p = .0001, Fisher's Exact Test). At 36 months of follow up, injections given were 2.9 (0.9 SD) in group A and 1.25 (0.4 SD) in group B.Conclusion: early immunosuppressive therapy exerts a positive action on the long-term control of uveitic CNV.

An Atom-Economical Method for the Formation of Amidopyrroles Exploiting the Self-Assembled Resorcinarene Capsule

Here is reported the first example of an organocatalyzed coupling between pyrrole and isocyanates in a nanoconfined space. The hexameric resorcinarene capsule C is able to catalyze the direct coupling between isocyanates and pyrroles to give amidopyrroles with excellent yields and selectivities. The reaction catalyzed by C prevents the use of expensive and poorly atom-economical reagents. As in natural enzymes, the cavity of C is able to discriminate between isomeric substrates.

Prismarenes: A New Class of Macrocyclic Hosts Obtained by Templation in a Thermodynamically Controlled Synthesis

The novel title macrocycles, based on methylene-bridged 1,5-naphthalene units, have been obtained by template effect in a thermodynamically controlled synthesis. In detail, the prism[5]arene 1 or the prism[6]arene 3 was selectively removed from the equilibrium mixture by using the complementary ammonium-templating agent. When only the solvent 1,2-DCE was used, the 1,4-confused derivative 2 was obtained. The prism[5]arene here described shows a deep π-electron-rich aromatic cavity that exhibits a great affinity for the quaternary ammonium guests, originating from favorable cation···π and ⁺NC–H···π interactions. This recognition motif is the basis of the templated synthesis of the prism[n]arenes here reported.

The Hexameric Resorcinarene Capsule as a Brønsted Acid Catalyst for the Synthesis of Bis(heteroaryl)methanes in a Nanoconfined Space

Herein, we show that the hexameric resorcinarene capsule C is able to catalyze the formation of bis(heteroaryl)methanes by reaction between pyrroles or indoles and carbonyl compounds (α-ketoesters or aldehydes) in excellent yields and selectivity. Our results suggest that the capsule can play a double catalytic role as a H-bond catalyst, for the initial activation of the carbonyl substrate, and as a Brønsted acid catalyst, for the dehydration of the intermediate alcohol.

Multiple threading of a triple-calix[6]arene host

The synthesis of the triple-calix[6]arene derivative 6 in which three calix[6]arene macrocycles are linked to a central 1,3,5-trimethylbenzene moiety is reported. Derivative 6 is able to give multiple-threading processes in the presence of dialkylammonium axles. The formation of pseudo[2]rotaxane, pseudo[3]rotaxane, and pseudo[4]rotaxane by threading one, two, and three, respectively, calix-wheels of 6 has been studied by 1D and 2D NMR, DOSY, and ESI-FT-ICR MS/MS experiments. The use of a directional alkylbenzylammonium axle led to the stereoselective formation of endo-alkyl pseudo[n]rotaxane stereoisomers.

Threading of Conformationally Stable Calix[6]arene Wheels Substituted at the Methylene Bridges

Calix[6]arenes disubstituted at the methylene bridges, which are stable in the cone or 1,2,3-alternate conformation, form pseudorotaxanes with dialkylammonium axles. The cone wheel-based pseudorotaxanes are 10-100 times more stable than those obtained with the native conformationally mobile calix[6]arene wheel, as a consequence of their higher degree of preorganization. The threading of conformationally stable 1,2,3-alternate calix[6]arenes is unprecedented in the literature. Therefore, very peculiar NMR features are here evidenced for this threading process involving the less symmetrical 1,2,3-alternate calix[6]arene conformation, which implies a peculiar rototranslation motion of the axle.

Synthesis, Characterization, and Solid-State Structure of [8]Cycloparaphenylenes with Inherent Chirality

We report here the synthesis of two [8]cycloparaphenylenes ([8]CPP) derivatives, 1 and 2, bearing a monosubstituted benzene moiety. The presence of the substituent implies a planar chirality for the monosubstituted [8]CPP 1 and 2, whose configuration is here described by applying the chirality descriptors pR and pS. Experimental evidence of this planar chirality has been obtained through ¹H VT NMR studies and by addition of Pirkle's reagent. This was confirmed by the X-ray crystal structure of 2, which represents an interesting example of solid-state structure of a monosubstituted [8]CPP derivative. Derivative 2 crystallizes in two monoclinic crystal forms (α and β), which show a herringbone motif. The [8]CPP ring of the α form encapsulates two dichloromethane molecules, held through C-H···π interactions, while in the β form, open channels are partially filled by highly disordered solvent molecules.

Green, Mild, and Efficient Friedel-Crafts Benzylation of Scarcely Reactive Arenes and Heteroarenes under On-Water Conditions

Metal-free Friedel-Crafts benzylation (FCB) of scarcely reactive arenes and heteroarenes was performed under on-water conditions by an environmentally sustainable procedure. The catalytic strategy exploits the hydrophobicity of the resorcinarene macrocycle 1 a. The proposed mechanism is based on the activation of benzyl chloride by H-bonding interactions with catalyst 1 a. In fact, under on-water conditions the hydrophobic amplification of the strength of the H-bonding interactions between the OH groups of the resorcinarene catalyst and the chlorine atom of benzyl chloride leads to polarization of the C-Cl bond, which consequently promotes electrophilic attack of the π nucleophile. Thus, many arenes and heteroarenes were efficiently benzylated under mild on-water conditions by using resorcinarene 1 a as catalyst. The FCB of benzene is industrially relevant for the synthesis of diphenylmethane, and hence the on-water procedure was extended to the gram-scale synthesis of diphenylmethane, starting from benzene and benzyl chloride in the presence of resorcinarene catalyst 1 a.

A hexameric resorcinarene capsule as a hydrogen bonding catalyst in the conjugate addition of pyrroles and indoles to nitroalkenes

A hexameric resorcinarene capsule (C) acts as a hydrogen bonding catalyst for the addition of nitroalkenes to pyrroles and indoles.

First demonstration of the use of very large Stokes shift cycloparaphenylenes as promising organic luminophores for transparent luminescent solar concentrators

The use of [n]CPP derivatives as luminophores in LSC-devices minimises reabsorption losses.

Synthesis, Optoelectronic, and Supramolecular Properties of a Calix[4]arene-Cycloparaphenylene Hybrid Host

A novel hybrid host has been obtained by fusion of the calix[4]arene skeleton with a cycloparaphenylene (CPP) ring. The CPP-bridged calix[4]arene 1 combines the optoelectronic and structural properties of the CPP rings with the recognition abilities of the calix[4]arene hosts. Thus, calix-CPP 1 shows an unexpected selectivity for the Li⁺ cation over Na⁺, as a result of more favorable cation···π interactions of Li⁺ with the CPP bridge and its better size complementarity.

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

Some examples of atropoisomeric pseudorotaxanes in which the isomerism arises by the different conformations adopted by the wheel are reported here. Upon threading hexahexyloxycalix[6]arene 1 with ammonium axles 2⁺ or 3⁺, bearing biphenyl or trifluoromethylbenzyl moieties, respectively, two atropoisomeric pseudorotaxanes were formed in which the calix[6]-wheel 1 adopts the 1,2,3-alternate and cone conformations. The interconversion between them cannot be obtained by simple rotation around the ArCH₂Ar bonds of the calixarene wheel, which is blocked by the presence of the axle inside its cavity. Therefore, it can only be obtained through a mechanism of de-threading/re-threading of the axle. In all the examined cases, the 1,2,3-alternate and cone atropoisomers are, respectively, the kinetic and the thermodynamic ones.

Solvent-Free Enantioselective Michael Reactions Catalyzed by a Calixarene-Based Primary Amine Thiourea

An upper-rim functionalized calix[4]arene-based thiourea installed onto the ( R, R)-1,2-cyclohexanediamine scaffold was synthesized with a view to investigate its catalytic ability in enantioselective Michael additions. The reactions were found to conveniently proceed under solvent-free conditions, observing good to high enantioselectivities. From this preliminary study, the calix[4]arene unit is likely to play a role in affecting the conversion and to a lesser extent to the stereochemical outcome of the reactions through van der Waals contacts and C-H···π interactions with the substrates.

Exploiting the p-Bromodienone Route for the Formation and Trapping of Calixarene Oxenium Cations with Enamine Nucleophiles

This study shows that calixarene p-bromodienone derivatives can act as precursors for the formation of oxenium cations, which can be trapped with enamine C-nucleophiles. When calixarene p-bromodienones were treated with enamines, in the presence of AgClO₄, the lower rim-substituted C-O-C products were obtained by an electrophilic attack of the intermediate calixarene-oxenium cation with a contemporary cone-to-partial-cone inversion of the involved aromatic ring.

Supramolecular Organocatalysis in Water Mediated by Macrocyclic Compounds

In the last decades many efforts have been devoted to design supramolecular organocatalysts able to work in water as the reaction medium. The use of water as solvent provides promising benefits with respect to environmental impact. In this context, macrocyclic compounds played a role of primary importance thanks to their ease of synthesis and their molecular recognition abilities toward the reactants. The aim of this review is to give an overview of the recent advances in the field of supramolecular organocatalysis in water, focusing the attention on calixarene and cyclodextrins derivatives. Calixarenes and cyclodextrins, thanks to their hydrophobic cavities, are able to host selectively the substrates isolating they from the reaction environment. In addition, the synthetic versatilities of these macrocycles permits to introduce useful functional groups in close proximity of the hydrophobic binding sites. Regarding the cyclodextrins (CDs), we have here reviewed the their most recent uses as organocatalysts for the synthesis of heterocyclic compounds, in multi-component reactions and in carbon-carbon bond forming reactions. Examples have been reported in which CD catalysts are able to drive the regiochemistry of common organic reactions. In addition, cyclodextrins bearing catalytically active chiral groups, have shown excellent enantioselectivity in the catalysis of organic reactions. Recently reported results have shown that calixarene derivatives are able to accelerate organic reaction under “on-water” conditions with a significant selectivity toward the reactants. Under “on-water conditions” the hydrophobic effect, induced by insoluble calixarene derivatives, forces the reactants and the catalyst to aggregate and thus accelerating the reaction between them thanks to an amplification of weak secondary interactions. Regarding the use of water-soluble calixarene organocatalysts, we have here reviewed their role in the acceleration of common organic reactions.

An Anthracene-Incorporated [8]Cycloparaphenylene Derivative as an Emitter in Photon Upconversion

The anthracene-incorporated [8]cycloparaphenylene 2 has been synthesized and its optoelectronic properties studied by UV-vis spectroscopy, cyclic voltammetry, and DFT calculations. NMR and computational studies indicate that the new cycloparaphenylene derivative possesses a C_s point group symmetry. The new CPP 2 exhibits peculiar optoelectronic properties: (i) fluorescence emission is blue-shifted with respect to [8]cycloparaphenylene 1, and its quantum yield is higher; (ii) in the presence of an octaethylporphyrin Pd complex, as sensitizer, it undergoes a visible light upconversion. This is the first case in which a cycloparaphenylene derivative is involved as an emitter in low power light frequency conversion.

Dinuclear zirconium complex bearing a 1,5-bridged-calix[8]arene ligand as an effective catalyst for the synthesis of macrolactones

“Macrocyclization of Cycles with a Macrocycle.” The intramolecular cooperation of metal centres in a novel dinuclear complex has been postulated as responsible for the observed high rate of formation of macrocyclic polyesters.

The hexameric resorcinarene capsule as an artificial enzyme: ruling the regio and stereochemistry of a 1,3-dipolar cycloaddition between nitrones and unsaturated aldehydes

The hexameric resorcinarene capsule as an artificial enzyme to rule the regio and stereochemistry of a 1,3-dipolar cycloaddition.