Synthesis and structural characterisation of functionalised cyclotetrasiloxane rings [4-RC6H4Si(O)OR']4 (R= Cl, Br, CH=CH2, CH2Cl; R'= Na, SiMe3) as scaffolds for the synthesis of models of a silica bound monolayer of fluorescent or second order NLO active organic chromophores

A series of sodium arylcyclotetrasiloxanolates properly functionalized in the para position of the aromatic ring, like [4-RC6H4Si(O)ONa]4 and the corresponding (trimethylsiloxy)cyclotetrasiloxanes [4-RC6H4Si(O)OSiMe3]4 (R = Cl, Br, CH@CH2, CH2Cl), were prepared as scaffolds for anchoring second order NLO active or fluorescent organic chromophores. Such cyclic molecules can be regarded as 2D models reproducing supramolecular organizations as monolayers. The crystalline structures of some of the compounds synthesized in this work were characterized by single crystal X-ray diffraction analysis at low temperature. All the compounds have phenyl rings in an all-cis arrangement with respect to the tetrasiloxane cycle which, in the trimethylsiloxy derivatives, is quite planar. In these latter compounds the phenyl rings are almost parallel one to the other, although not orthogonal to the ring.