Donor/Acceptor Complexes in Hydrogen-Bonded Networks: pH-Dependent Self-Organization

摘要

Donor/acceptor complexes [D~(δ+) ... A~(δ-)] between donor molecules of low ionizution energy, which also function as Lewis bases, nucleophiles, or reducing reagents, and electron-deficient acceptor molecules with their properties as Lewis acids,electrophiles, or oxidizing reagents arc kept together by weak Coulomb interactions and can be intermediates in microscopic pathways of substitution or redox reactions. Their fascinating color is due to the long-wavelength excitation into short-lived charge transfer (CT) states {D~(centre dot +) ... A~(centre dot -)}. Structural analysis of mixed-stack aggregates between six-membered ring donors and acceptors, which can be specifically crystallized, proves that in their ground states, all bond lengths andangles of the components remain unchanged on n-com-plexation. Attempts to increase the re-interaction by shortening the donor ... acceptor distance, thereby generating recognizable structure perturbations, have been the starting point for the crystallization of donor acceptor complexes in hydrogen-bonded networks illustrated by the following examples.