Cooperative induction in double H-bonding donor/acceptor compounds: Chains vs. ribbons

Abstract

Two different types of monodimensional crystalline aggregates formed by squaramides, chains and ribbons, have been studied both in the solid state and ab initio with four model compounds. Although ribbons are a priori possible, only covalently forced syn conformations have been observed. Cooperative induction is postulated to explain the preference for chains instead of ribbons in squaramide crystals.