Jürgen Schatz3, Frank Schildbacha, Axel L en tzb, Sylvia R a stä tte rb, Joachim Schilling5, Jö rg D o rm an n c, A n d reas R uoffc, and Tony D eb ae rd em ae k erd The inclusion complexes formed from carbon disulfide and /?-r£7-r-butylcalix[4]arene ( 1 C S 2) or /?-rm-butylcalix[6]arene (2-C S2) were investigated by X-ray crystal structure analysis, infrared (IR) and Raman spectroscopy. The complex 1 C S 2 crystallises in the space group P4/n, 2 C S 2 in the space group P2xln. In case of /?-rm-butylcalix[4]arene as host the carbon disulfide molecule is included in the cavity. In the crystal structure of p-rm -butylcalix[6]arene clathrate, self-com plexation o f one rm-butyl group in the cavity o f another calix[6]arene can be observed. Due to inclusion, the symmetry of CS2 is lowered both in the prm -butylcalix[4]arene and p-rm-butylcalix[6]arene case causing significant shifts in the fully assigned infrared and Raman spectra.

By comparison of the fully assigned vibrational spectra obtained for resorcarene-based cavitands 2a and 2b, their clathrates with toluene and ethanol respectively, and free guest molecules, good structural models for the clathrates could be obtained merely based on Fourier transform infrared data. Using this novel technique, various different interactions between the host and guest in the solid state as well as the orientation of the included guest could be identified. In the case of cavitand 2a, the model obtained by this methodology could be validated by comparison with an experimental crystal structure analysis.

Mono-and tetrakis(aminomethyl)-substituted resorcinarene-based cavitands 1 and 2 and their clathrates 1 2 ÁTHF and 2Á(THF) 2 were investigated by FTIR spectroscopy and thermogravimetric analysis. Both hosts form stable clathrates with THF both in solution and in the solid state. Major intra-and intermolecular interactions could be identified and located by the use of vibrational spectroscopy. In all cases, dynamic cyclic intramolecular hydrogen bonds between the amino groups and neighbouring ether bridges are observable. a Interpretation of band splittings; sh = shoulder; br = broad. * Superposition of guest and host bands. 1, Different orientations of the host molecules in the crystal lattice (one inside, one outside the cavity). 2, Different orientations of the guest molecule in the cavity.

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 1 H 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 C 4 symmetrical arrangement is probable. Guest molecules, such as benzene or cyclohexane, are enclosed inside the container rotating fast on the IR timescale around a longitudinal axis of the guest. From the observed splitting of absorption bands upon dimerization and inclusion it follows that either two crystallographically independent types of capsules exist in the crystal lattice or that the guests are occupying two major orientations in the capsule. As indicated by a higher complexation induced shift for cyclohexane, this guest exhibits a tighter interaction with the host molecules compared to benzene.