Molecular structures of fluorene derivatives

A. PIOTTO; C. G. POZZI; G. A. ECHEVERRÍA; M. C. AVALOS; R. BOLMARO; G. PUNTE

Santa Marta

Congreso; LATIN AMERICAN SEMINAR OF ANALYSIS BY X-RAY TECHNIQUES (SARX 2012); 2012

Molecular structures of 4 fluorene dervatives have been studied: 9-(p-iodo-benzylidene)-9H-fluorene (1), bis-(phenylethynyl)-9-fluorenone (2), 9-(p-phenylethynyl-benzylidene)-9H-fluorene (3) and 9-(p-iodo-benzylidene)-2,7-bis-phenylethynyl-9H-fluorene (4). Compounds (1), (2) and (3) crystallize with two molecules for asymmetric unit. All the 3D structures are stabilized by C - H...pi(aryl/fluorene) interactions. In (1) they help to build helicoidally arranged chains along c, which organize in layers parallel to (011) plane, which are linked by C-H...I contacts. In (2) C -H ...pi(ethynyl), and  pi(arom)...pi(arom) contacts are also observed and help molecules to build chains perpendicular to the (100) plane forming herringbone interactions. In (3), in spite of some degree of disorder, it could be determined that the substituent in 9 is twisted out of the fluorene plane and  that inequivalent moleculesare arranged in planes perpendicular to a.  In (4) we also found contacts I...π(ethynyl)  and C - H...I originating an helix along b, which organize in infinite chains along this axis. Adjacent chains are linked by the C-H...pi(arom)  forming layers perpendicular to c and connected by  C- H...pi and C-H...C- H contacts. UV-Vis and fluorescence spectra of the four compounds in solutions were obtained and analyzed into the light of the known crystal structures and intermolecular interactions.Acknowledgements: UNLP, CONICET PIP 0985