Abstract
We report the synthesis of a new macrocyclic receptor, namely 2,8,14,20-tetra-hexyl-4,24:6,10:12,16:18,22-O,O'-tetra-kis-[2,3-di-hydro-[1,4]dioxino[2,3-g]quinoxalin-7,8-di-yl]resorcin[4]arene, DeepQxCav, obtained by the addition of ethyl-ene glycol di-tosyl-ate to an octa-hydroxy quinoxaline cavitand. A 1:1 supra-molecular complex of this cavitand with benzene has been obtained and analysed through X-ray diffraction analysis. The complex, of general formula C92H88O16N8·C6H6, crystallizes in the space group C2/c, with the cavitand host located about a twofold rotation axis. The benzene guest, which is held inside the cavity by C-H⋯π inter-actions and dispersion forces, is disordered over two equivalent sites, one in a general position and one lying on a twofold axis. The crystal structure features C-H⋯O hydrogen bonds and C-H⋯π inter-actions involving the alkyl chains, the aromatic rings, and the O atoms of the dioxane moiety of the resorcinarene scaffold. The crystal studied was refined as a two-component twin.
Highlights
C22AÁ Á ÁC23Ai C22BÁ Á ÁC23Bi two sites, one in a general position and one lying on a twofold axis
In this paper we report and analyse the crystal structure of its complex with benzene as guest
The mean planes passing through the quinoxaline moieties are inclined with respect to the plane passing through the O1/O2 atoms, forming angles of 85.24 (3) and 75.16 (4) for the walls labelled A and B, respectively
Summary
Resorcinarene-based cavitands are macrocyclic synthetic compounds (Cram, 1983; Cram & Cram, 1994), whose versatility primarily stems from the possibility of modifying the size and form of the cavity by choosing different bridging groups connecting the phenolic hydroxyl groups of the resorcinarene scaffold This allows the tuning of the complexation properties of the cavity, which can interact with neutral and charged molecules through hydrogen bonding, – stacking and C— HÁ Á Á interactions, and forms coordinate bonds with metal centers to create discrete complexes, cages or extended networks. The demand for fast and reliable detection of biological and chemical hazards is rising continuously and optimal sensors for environmental, security and biomedical applications must be sufficiently responsive to allow detection of the target analyte at low concentrations, and selective enough to respond primarily to a single chemical species in the presence of interferents In this respect, quinoxaline-based cavitands, exploiting the -basicity and hydrophobicity of their cavity are ideal hosts to interact with aromatic compounds (Pinalli et al, 2018). The mouth of the cavity is roughly rectangular in shape, but because of the bending of the walls, the opening is blocked by the steric hindrance of the four 1,4 dioxane rings (see Table 1 for geometrical details)
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