Conformational control through co-operative nonconventional C-H• • •N hydrogen bonds

We report the design, synthesis, and crystal structure of a conjugated aryleneethynyl molecule, 2-(2-{4,5-dimethoxy-2-[2-(2,3,4-trifluorophenyl)ethynyl]phenyl}ethynyl)-6-[2-(pyridin-2-yl)-ethynyl]pyridine, C30H17F3N2O2, that adopts a planar rhombus conformation in the solid state. The molecule crystallizes in the space group P (1) over bar, with Z = 2, and features two intramolecular sp(2)-C-H center dot center dot center dot N hydrogen bonds that co-operatively hold the arylethynyl molecule in a rhombus conformation. The H atoms are activated towards hydrogen bonding since they are situated on a trifluorophenyl ring and the H center dot center dot center dot N distances are 2.470 (16) and 2.646 (16) angstrom, with C-H center dot center dot center dot N angles of 161.7 (2) and 164.7 (2)degrees, respectively. Molecular electrostatic potential calculations support the formation of C-H center dot center dot center dot N hydrogen bonds to the trifluorophenyl moiety. Hirshfeld surface analysis identifies a self-complementary C-H center dot center dot center dot O dimeric interaction between adjacent 1,2-dimethoxybenzene segments that is shown to be common in structures containing that moiety.