Introduction Calixarenes are versatile molecular scaffolds for design of highly efficient and selective receptors, self-assembling systems such as molecular capsules and well defined functional nanostructures. Herein we report on progress in rational design of the calixarene receptors and their supramolecular complexes with environmentally hazardous and biologically relevant cations, anions and neutral molecules. The calixarenes or their complexes can be used as materials for radionuclide extraction, construction of chemo-sensors, drug design. An attention is focused to chiral calixarenes and their complexes with biomolecules. Cation Receptors In order to obtain efficient and selective cation receptors parent calixarenes were functionalized with phosphorus-containing legating functional groups. The calix[4]arene bearing four phosphoryl groups at the narrow rim of the macrocycle selectively binds Li+ in the presence of Na+, K+, Cs+ and NH4 + [1]. To obtain receptors for multi-charged cations we have synthesised calixarenes bearing cationoacceptor groups such as phosphineoxide, carbamoylphosphineoxide and di-phosphineoxide at the wide rim of the macrocycle [2, 3]. The phosphorus containing calixarenes have been shown to extract lanthanides as well as actinides such as Am, Cm, Pu and U. It is noteworthy that calixarene carbamoylphosphineoxides are capable of selective extracting Am (III) in the presence of Eu(III). The calixarene bearing four tetrazole fragments at the wide rim of the macrocycle forms solid complex with PdCl2 [4]. The X-ray diffraction study revealed that in this complex two Pd atoms link two molecules of the tetrazolocalixarene through the coordination with the nitrogen atoms of the tetrazole rings.figureSingle crystal X-ray structure of the calixarenetetrazole and its complex with PdCl2 Anion receptors Molecular recognition of anions is an important topic in supramolecular chemistry since anions play crucial role in many biochemical processes and in chemical technology. Several carbamide functions were attached to the narrow rim of the macrocycle in order to achieve strong and selective binding of halide anions through multiple and cooperative hydrogen bonding [5]. The chiral calixarenecarbamides, bearing two fragments of l-Ala are capable of stereoselective binding the anion forms of racemic aminoacids. For example, l-phenylalanine anion is bound 4 times stronger than its enantiomer. Receptors for organic compounds and biologically relevant molecules We obtained new calixarene receptors which bind various organic molecules in the crystalline state, solution, and gaseous phase [6-13]. The calix[4]arene derivatives bearing two or four dihydroxyphosphonyl groups form stable complexes with herbicides 2,4-D and atrazine in aqueous solution [6]. Molecular capsules are promising self-assembling receptors which may be used as sensitive materials in chemo-sensors. Two molecules of the thiacalixarene bearing four carbamoylphosphinoxide groups at the wide rim of the macrocycle form dimeric capsules stabilized by a seam of eight NH O=P hydrogen bonds. The volume of the cavity was estimated to be 370 Å3. This can be filled with a solvent molecule (chloroform, benzene, toluene) or such a complementary cation as tetraethylammonium or cobaltocenium [7]. The design of receptors for bio-relevant molecules is an important trend in bio-medical investigations since it allows to rationally construct the sensitive materials for diagnostic systems of biomedical application. On the basis of phosphorylated calixarenes we have obtained novel receptors for uracil and adenine derivatives, aminoacids, dipeptides [8-10]. The calixarenes functionalized at the wide rim of the macrocycle with methylenebisphosphonic or aminophosphonic acid fragments inhibit the alkali phosphatases [11, 12] with inhibition constants of 0.38 – 86 μM. The chiral calixarenebisaminophosphonic acids show stereoselective inhibition. Namely the RR isomer is about 50 times more effective than its SS counterpart [12].