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 , with Z = 2, and features two intramolecular sp2 -C - H-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-N distances are 2.470(16) and 2.646(16)Å, with C - H-N angles of 161.7(2) and 164.7(2)°, respectively. Molecular electrostatic potential calculations support the formation of C - H-N hydrogen bonds to the trifluorophenyl moiety. Hirshfeld surface analysis identifies a self-complementary C - H-O dimeric interaction between adjacent 1,2-dimethoxybenzene segments that is shown to be common in structures containing that moiety.


Chemistry and Biochemistry

Document Type




C - H-N hydrogen bond, conformational control, crystal structure, intramolecular hydrogen bonding, molecular rhombus, nonconventional hydrogen bond, self-complementary hydrogen bond

Publication Date


Journal Title

Acta Crystallographica Section C: Structural Chemistry