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The product was unambiguously identified using NMR spectroscopy and mass spectrometry ( Figures S48, S49, and S54 Scheme S4 of the Supporting Information, SI), and was further characterized crystallographically in the solid state (see below). Using the above approach we were able to prepare up to 180 mg of 1 in a single batch. (50) Under these conditions, 5 cleanly produced the target 1, which was isolated in an 86% yield as a yellow solid. Reductive aromatization of the two masked p-phenylene units in 5 was performed using a tin(II) reagent, as reported by Yamago et al.

These are angles different in the parent calixarene (49) ( 2 with X = H, θ 1 = −24.2° and θ 2 = 68.6°), indicating that the observed conformation of 5 is a compromise between the steric requirements of the constituent subunits. The interplanar angles between the diagonal pairs of benzene rings in the calixarene section of 5 are respectively θ 1 = 33.8° and θ 2 = 76.9° ( Scheme 1). The molecular structure of 5, revealed by an X-ray crystallographic analysis, is characterized by slight bending of the lateral biphenyl sections of the loop, indicative of a small degree of internal strain. (48) 2a was borylated and coupled with Jasti’s masked phenylene building block 3, (38) and the resulting dibromo intermediate 4 was cyclized using Yamamoto coupling, to furnish the basket-like precursor 5. (37)Ĭompound 1 was prepared from the diagonally functionalized dibromocalixarene 2a, which can be obtained stereoselectively as a cone-like structure ( Scheme 1). (34−36) These features can be leveraged to enhance supramolecular interactions and to produce usable physical output upon self-assembly. (24) While the synthesis of curved aromatics is often challenging, (26) they provide structural rigidity, variable curvature types, (27−29) topologically nontrivial π conjugation, (23,30−32,19) chirality, (33) and unusual chromophore properties. The curvature facilitates formation of interlocked structures, i.e., rotaxanes, (20,21) catenanes, (22−25) and molecular knots. (18,19) In these systems, the receptor function can be precisely controlled by the type and extent of curvature and by adjusting the cavity dimensions. (1−3) In particular, carbon-rich cavities of such systems have been used to develop cylindrical, (3−11) concave, (12,13) and macrocyclic hosts (14,15) for spherical guest molecules and ions, self-assembling surfaces, (16,12,17) and porous organic materials. Methylacridinium and anthraquinone adducts show red-shifted emission in the solid state, attributable to the charge-transfer character of these inclusion complexes.Ĭurved aromatic molecules have found diverse uses in supramolecular and nanomaterials chemistry. In solution, the receptor shows cyan fluorescence (λ max em = 485 nm, Φ F = 33%), which is partly quenched upon binding of guests. The solid receptor is porous to gases and vapors, yielding an uptake of ca. The interaction with the methylacridinium cation in solution was interpreted in terms of a 2:1 binding model, with K 11 = 5.92(7) × 10 3 M –1. The new receptor forms inclusion complexes in the solid state and in solution, showing a dependence of the observed binding strength on the shape of the guest species and its charge.

The system contains an electron-rich cavity with an adaptable shape, which can serve as a host for electron deficient guests, such as diquat, 10-methylacridinium, and anthraquinone. A hybrid nanocarbon receptor consisting of a calixarene and a bent oligophenylene loop (“molecular squid”), was obtained in an efficient, scalable synthesis.