Hydrogen-bond-assisted, crossed dipole π-stacking in 1,4-bis(phenylethynyl)benzene

2,5-Bis(2-hydroxyethoxy)-1,4-bis(phenylethynyl) benzene (BHE-PE2.5) was synthesized and characterized by X-ray single-crystal diffraction analysis: formula=C26H22O4, M=398.44, orthorhombic unit cell, Pbcn, a=22.5520(9)angstrom, b=12.9259(4)degrees, c=7.2463(2)angstrom, alpha=beta=gamma=90.00(0)degrees, V=2112.33(12)angstrom(3), Z=4, R-1=0.1194, wR(2)=0.1455. The molecules are somewhat deplanarized, with a 19.8 degrees interplane torsion between phenyl rings. They form pi-stacks with a centroid-centroid distance of 3.62 angstrom along the stack axis, a cant angle of the central phenyl ring of 13.2 degrees relative to the pi-stack c-axis, and a 99.2 degrees rotation of each molecule along the pi-stack, yielding crossed-dipole stacks in which the molecular long axes alternate nearly perpendicularly to one another. This unusual crossed dipole pattern is induced by a network of hydrogen bonds that assembles the BHE-PE2.5 molecules into the stacks and further associates the stacks into two-dimensional sheets.