Vibrational spectroscopy of a tetraureidocalix[4]arene based molecular capsuleElectronic supplementary information (ESI) available: three tables containing fully assigned IR data of tetraureido calix[4]arene 1, its complex with cyclohexane and benzene, and the corresponding model substances 2–5 as well as 1H NMR spectra of the capsules 1·C6H6·1 and 1·C6H12·1 in solution. See http://www.rsc.org/suppdata/p2/b1/b108055p/

Structural models for self-assembled dimers composed of two urea calix[4]arenes which entrap benzene or cyclohexane are developed using Fourier transform infrared (FTIR) spectroscopy. Based on the host–guest ratio determined by 1H NMR spectroscopy in solution, and confirmed for the solid state by a thermogravimetric analysis, it is possible to prove by a comparison of the FTIR data of host, guest, complex and model compounds, that the capsule is held together by a cyclic array of weak and strong hydrogen bonds between the urea units attached at the wide rim of the calixarenes. The dimerization of the two urea units leads to a loss of symmetry, and an averaged C4 symmetrical arrangement is p…