Calix[6]arene derivatives as tools to tune the properties of their bound guests

This PhD dissertation focuses on the potentiality of host-guest chemistry as tool to modulate the physical and chemical properties of chemical species through intermolecular interactions. Initially, the ability of tris(N-phenylureido) calix[6]arene hosts to enhance the reactivity of threaded N-alkyl-pyridylpyridinium salts towards nucleophilic substitutions, was exploited to obtain sophisticated molecular architectures. In particular, [3]rotaxanes composed by two non-palindrome calix[6]arene hosts and a threaded bisviologen-based dumbbell, may exist in three different orientational isomers. The supramolecular assisted approach allowed to obtain all the possible orientational isomers of the [3]rotaxanes with good yields and high control on the reciprocal orientation of the components. Then, the synthesis of a two-stations-two-gates oriented catenane was carried out to examine the possibility to use this MIM as a prototype of a unidirectional rotatory molecular motor. A further significant study explored the influence of the complexation inside a tris(N-phenylureido)-calix[6]arene host on the spectroscopic behavior of stilbazolium salts, particularly focusing on the role played by the orientation of these guests inside the cavity. Lastly, the properties of new bis(N-phenylureido)- and bis(N-phenylthioureido)-calix[6]arene hosts were investigated. The impact of the modification of the number/type and geometrical arrangement of the functional groups at the upper rim on the conformation and complexation ability of the hosts was investigated.