SUPRAMOLECULAR ASSEMBLIES OF CATIONIC CALIX[4]RESORCINARENES AND METAL CHLORIDES ANIONES

Aidar T. Gubaidullin, Yulija E. Morozova, Ella Kh. Kazakova, Igor A. Litvinov

A.E.Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, 420083 Kazan, Russian Federation. Fax: +7 8432 767 424; e-mail:aidar@glass.ksu.ras.ru

Keywords: single-crystal X-ray, calix[4]resorcinarenes, complexes

Calixarenes, a class of synthetic macrocycles having a phenolic residues in a cyclic array, are widely used in supramolecular chemistry. It is known that calixarenes may exist in charged or uncharged forms in complexes. The structure of the protonated forms is less studied.

In this report we present the results of the crystal structure investigation of the aminomethylated calix[4]resorcinarene derivatives and their ionic complexes with metal (Zn, Pd, Cd) chlorides. This is the first example of X-ray data for metal complexes, where calix[4]resorcinarenes exist in the protonated form.

Conformational modifications of the macrocycles induced by the process of complexation are discussed based on the comparative analysis of this data with one obtained for neutral "host" calixarene molecules. It was shown that the structure of the calixarene moiety and three dimensional arrangement of the complexes with the same calixarene fragment depends greatly on the "guest" metal and inclusion of solvate molecules.

It should be pointed out, that the crystal packing analysis of the supramolecular complexes is very difficult because of numerous fragments and residues included in the assymetric part. In some cases fragmentary structures like layers, are used for three dimensional arrangement analysis. We present one of the possible options of the supramolecular structure packing analysis which, as we think, make sufficiently demonstratable presentation of the structures.

In the compounds under investigation the hydrophobic and hydrophilic regions are strongly localised in the crystal. As building units of the three dimensional packing a fragmentary structure, consisting of infinite one-dimensional stick, is choosen. This stick consists of more hydrophobic calixarene residues, whereas polar substituents, inorganic anions and solvate molecules form hydrophylic shell around the sticks.

Several types of superstructures which differ by the host:guest stoicheiometry and the mode of metal-guest and host molecules respective disposition is observed, the ionic canal-structures is found. Intra- and intermolecular interactions are analized. The factors determining the process of complex formation are discussed.