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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.

Methoxy-prism[5]arene PrS[5]Meis demethylated by a supramolecularly assisted reaction. In the presence of a tetramethylammonium cation, PrS[5]Meis demethylated by BBr3in high yield, while in its absence a 55/40 mixture of PrS[5]OH/PrS[6]OHis 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.

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–)2bearing 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–)2show 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.

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]arenes make up a new class of phenol–naphthalene hybrid macrocycles. X-ray studies show that calix[2]naphth[2]arene 1adopts 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 5and 6were observed in which the cation is nested on one of the two faces of the macrocycle.

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 1or the prism[6]arene 3was 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 2was 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 macrocyclization of 2,6-dialkoxynaphthalene monomers to prism[5]arenes is thermodynamically templated by DABCO cations. In this study, we demonstrate that a greater template affinity for prism[5]arene improves the macrocyclization yield. By using novel templating cations, the yield of alkoxy-prism[5]arenes increases significantly compared with those of previously reported procedures, while the purification process becomes easier and faster.

[8]Cycloparaphenylene derivative 1has been synthesized and its recognition abilities toward pyridinium guests have been investigated and compared with the [8]CPP macrocycle. The results showed a fine-tuning of the binding properties of [8]CPP 1toward pyridinium cations due to the presence of the 1,4-DMB ring. DFT calculations indicate that the close steric fitting between the rigid cavity of 1and the pyridinium guest is the crucial factor for the stabilization of their supramolecular complex through C–H···π and N+···π1,4DMBinteractions.

We report here the synthesis of two [8]cycloparaphenylenes ([8]CPP) derivatives, 1and 2, bearing a monosubstituted benzene moiety. The presence of the substituent implies a planar chirality for the monosubstituted [8]CPP 1and 2, whose configuration is here described by applying the chirality descriptors pRand 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 2crystallizes 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.

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 1combines the optoelectronic and structural properties of the CPP rings with the recognition abilities of the calix[4]arene hosts. Thus, calix-CPP 1shows 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.

Monopropargyloxy-tripropoxy-calix[4]arene 1was 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 6forms two stereoisomeric complexes stabilized by +N–H···O and cation···π interactions.