Extended Self-complementary Halogen Bonded Dimers

Lisa Kirchner, MSU Graduate Student
Nathan Bowling
Eric Bosch, Missouri State University

Abstract

The X-ray structure of a series of 1,4-diethynylbenzene bridged pyridyl polyfluoroiodo- and polyfluorobromophenyls designed to form self-complementary dimers in the solid state are reported. The compound 2-[[4-[(3-bromotetrafluorophenyl)ethynyl]phenyl]ethynyl]pyridine, 1, crystalized in the triclinic space group P-1 with unit cell parameters a = 6.3332(4) (Ã…), b = 7.4288(4) (Ã…), c = 17.8897(10) (Ã…) and α = 91.0980(10)°, β = 90.8580(10)° and γ = 94.3830(10)°. The asymmetric unit contains a unique molecule as a self-complementary halogen bonded dimer. Compounds 2, 3-[[4-[(2-bromotetrafluorophenyl)ethynyl]phenyl]ethynyl]pyridine and 3, 3-[[4-[(2-iodotetrafluorophenyl)ethynyl]phenyl]ethynyl]pyridine both crystalized in the triclinic space group P-1 and are isostructural with unit cell parameters a = 6.1324(13) (Ã…), b = 11.264(2) (Ã…), c = 13.064(3) (Ã…), α = 66.646(3)°, β = 89.736(3)°, γ = 87.726(3)° for 2 and a = 6.1671(5) (Ã…), b = 11. 2571(9) (Ã…), c = 13.3083(11) (Ã…), α = 66.2870(10)°, β = 88.1990(10)°, γ = 87.3820(10)° for 3. In both structures the molecules assemble as essentially planar self-complementary halogen bonded dimers. In contrast 3-[[4-[(2-bromo-4,5-difluorophenyl)ethynyl]phenyl]ethynyl]pyridine, 4, crystalized in the monoclinic space group P21/c with unit cell parameters a = 18.7881(7) (Ã…), b = 3.83820(10) (Ã…), c = 22.9321(9) (Ã…), α = γ = 90°, β = 102.6180(10)° and featured a C"“H···N hydrogen bonded dimer.