Modulation of the Electronic and Mesomorphic Properties of Alkynyl–Spirobifluorene Compounds as a Function of the Substitution Pattern

• Published in: Journal of physical chemistry. C 2015-05, Vol.119 (19), p.10564-10575
• Main Authors: Thiery, Sébastien, Heinrich, Benoît, Donnio, Bertrand, Poriel, Cyril, Camerel, Franck
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Organic chemistry
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.5b01691

An original series of eight 9,9′-spirobifluorene substituted differently by ethynylbenzene or N-(ethynylphenyl) benzamide fragments, carrying hexadecyl carbon chains, in the 2-, 4-, and 7-positions have been synthesized. The substitution pattern/photophysical properties relationship as well as the thermal properties have been deeply studied. The photophysical properties of these eight derivatives were found to be higly sensitive to the number, the position, the conjugation length, and the nature of the alkynyl fragment. All compounds are deep blue emitters in solution and in the condensed state, and quantum yields up to 40% were found in the solid state. Finally, the symmetrical introduction of four ethynylbenzene or N-(ethynylphenyl) benzamide fragments in the 2-, 2′-, 7-, and 7′-positions was found to be mandatory for the emergence of blue emissive mesomorphic materials, and X-ray scattering analyses have evidenced the formation of columnar mesophases of hexagonal or rectangular symmetries containing staggered double-strings formed by the face-to-face stacking of SBF core halves.