Polar order by rational design: crystal engineering with parallel beloamphiphile monolayers.

Polar order in the biosphere is limited to nanometer-sized domains, occurs with essentially complete cancellation, or is avoided on purpose. One thus wonders whether large-scale polar order is even possible, and this question is the subject of the dipole alignment problem. We addressed this challenge with an interdisciplinary approach bringing together elements of mathematics, electronic structure theory and computational chemistry, physical-organic and synthetic chemistry, crystallization and crystallography, and, most importantly, patience and much thought about intermolecular bonding in molecular crystals. The azine- and biphenyl-based beloamphiphiles (Y-Ph-MeC=N-N=CMe-Ph-X and Y-Ph-Ph-X) are ascendants of a new generation of highly anisotropic functional materials with perfect polar order.