Spontaneous resolution in a new chiral purely organic crystal containing homochiral helical chains: Synthesis, crystal structure, and phosphorescence

Abstract

A novel chiral purely organic crystal [(A)(HA+HSO4−)2]⋅2H2O (1) (A=2-(imidazo [1,2-a]pyridin-2-yl)-2-oxoacetic acid) has been obtained through diffusion of acetone into sulfuric acid aqueous solution of A. This crystal was characterized by the elemental analysis, IR spectrum and the single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic system, chiral space group P21, with a=10.092(2)Å, b=15.641(3)Å, c=10.551(2)Å, β=101.62(3)°, and Z=2. Compound 1 reveals left-handed 21 helical chain assembled by hydrogen bond and hydrophobic (short atomic contact) interactions, in which spontaneous resolution occurs. The left-handed chirality of the original helical chain is transferred uniformly to adjacent chain in a homochiral manner, through interchain hydrogen bond and hydrophobic interactions, resulting in the formation of chiral layer. Compound 1 also exhibits green phosphorescence.