Perfect Polar Alignment of Parallel Beloamphiphile Monolayers: Synthesis, Characterization, and Crystal Architectures of Unsymmetrical Phenoxy-Substituted Acetophenone Azines.

Abstract

It remains a great challenge to achieve polar order in organic molecular crystals because anti-parallel alignment of side-by-side molecules is intrinsically preferred. We have addressed this problem with a rational design that focuses on the polar stacking of parallel beloamphiphile monolayers (PBAMs) with strong lateral quadrupole-quadrupole attractions. We employ arene-arene interactions as lateral synthons. The first successes were achieved with unsymmetrical donor (X), acceptor (Y) substituted acetophenone azines which form polar PBAMs with double T-contacts between the azines. Near-perfect alignment was achieved with the methoxy series of (MeO, Y)-azines with Y=Cl, Br, I. Here, we report on the synthesis, the characterization (GC/MS, 1 H NMR, 13 C NMR, FTIR), the crystallization, and the single-crystal X-ray analyses of the phenoxy series of (PhO, Y)-acetophenone azines with Y=F, Cl, Br, I. Properties of (RO, Y) azines were computed at the APFD/6-311G* level and are discussed with reference to p-nitroaniline (PNA). This (PhO, Y) series embodies an improved PBAM design based on triple T-contacts which is shown to facilitate faster crystallization and to produce larger crystals. Perfect polar-alignment has been achieved for the phenoxy series of (PhO, Y)-azines with Y=Cl, Br, I and the (PhO, F)-azine also features near-perfect dipole alignment.