4,10,16,22-Tetra-kis(2-chloro-acet-oxy)-6,12,18,24-tetra-meth-oxy-2,8,14,20-tetra-pentyl-resorcin[4]arene

Correlating Solution- and Solid-State Structures of Conformationally Flexible Resorcinarenes: Significance of a Sulfonyl Group in Intramolecular Self-Inclusion

The synthesis of tetramethoxyresorcinarene podands bearing p-toluene arms connected by -SO3 - (1) and -CH2 O- (2) linkers is presented herein. In the solid state, the resorcinarene podand 1 forms an intramolecular self-inclusion complex with the pendant p-toluene group of a podand arm, whereas the resorcinarene podand 2 does not show self-inclusion. The conformations of the flexible resorcinarene podands in solution were investigated by variable-temperature experiments using 1D and 2D NMR spectroscopic techniques as well as by computational methods, including a conformational search and subsequent DFT optimisation of representative structures. The 1 H NMR spectra of 1 and 2 at room temperature show a single set of proton signals that are in agreement with C4v symmetry. At low temperatures, the molecules exist as a mixture of boat conformations featuring slow exchange on the NMR timescale. Energy barriers (ΔG≠ 298 ) of 55.5 and 52.0 kJ mol-1 were calculated for the boat-to-boat exchange of 1 and 2, respectively. The results of the ROESY experiments performed at 193 K and computational modelling suggest that in solution the resorcinarene podand 1 adopts a similar conformation to that present in its crystal structure, whereas podand 2 populates a more versatile range of conformations in solution.

4,5,6,10,11,12,16,17,18,22,23,24-Dodeca-kis-[(meth-oxy-carbon-yl)meth-oxy]-2,8,14,20-tetra-pentyl-resorcin[4]arene

The title compound, C(84)H(112)O(36), has a macrocyclic structure. It has 12 (meth-oxy-carbon-yl)meth-oxy 'head groups' in the upper rim and exhibits a flattened boat geometry. Intra-molecular C-H⋯O hydrogen bonds occur. In the crystal, inter-molecular C-H⋯O contacts occur. The 'head groups' and the pentyl 'feet' contain disordered (0.5:0.5 occupancy ratio) atoms.