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Abstract

Approaches to novel diphenylacetylene derivatives and related compounds with restricted rotation of the phenyl rings have been developed. Since mutual overlapping of molecular orbitals specifies the electronic communication between aromatic π-systems, regulation of the conformation within a molecule gives control over conductive and photophysical properties of tolane. Amide- and ester bound tethers have been used. The first one resists aggressive factors better, compared with ester. Introduction of amide-functionalized tethers have been demonstrated by synthesis of two bridged tolanes; a novel double-bridged 1,4-bis(phenylethynyl)benzene (I) was prepared.

In addition, synthetic approaches leading to multi-gram amounts of bifunctional tolanophanes are shown, ready for further derivatization. TIPS-acetylene derivatives possessed not only outstanding emissive, but also interest-evoking structural properties, expressed in folded cyclic dimers with electronically interacting chromophore units by means of π-π-stacking. Considering this, series of cyclic oligomers have been synthesized and investigated.

From previous studies it was known, that in the solid state twisted tolanophanes planarize after excitation due to a special arrangement of the electronic states. Introduction of the second tether into the tolanophane molecule gives a more rigid molecule (II) and leads to a better understanding of the emissive properties of tolane chromophores. Compound II showed a twisted conformation in the excited state. Figure I. Selected synthesized and studied molecules.

Further, bifunctional tolanophanes have been used for copolymerization (III). Bridged derivatives of 1,4-diphenyldiacetylene have been investigated, as they are usual defects in poly(para-phenyleneethynylene)s and can significantly affect their properties. Emissive ability of these substances appeared to be not distinct; they showed weak photophysical response on twisting.