Redox-Controlled Hydrogen Bonding: Turning a Superbase into a Strong Hydrogen-Bond Donor

• Published in: Chemistry : a European journal Vol. 20; no. 20; pp. 5914 - 5925
• Main Authors: Wild, Ute, Neuhäuser, Christiane, Wiesner, Sven, Kaifer, Elisabeth, Wadepohl, Hubert, Himmel, Hans-Jörg
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 12.05.2014; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Acceptors (electronic); Aggregates; aggregation; Chemistry; Chemistry, Multidisciplinary; Coloring Agents - chemical synthesis; Coloring Agents - chemistry; Donors (electronic); Formations; Freezing; Frozen; guanidine; Guanidine - chemical synthesis; Guanidine - chemistry; Hydrogen - chemistry; Hydrogen Bonding; hydrogen bonds; Models, Molecular; Oxidation; Oxidation-Reduction; Physical Sciences; Science & Technology; self-assembly; COORDINATION CHEMISTRY; ZINC-COMPLEXES; oxidation; REACTIVITY; aggregation; hydrogen bonds; guanidine; self-assembly; PROTON AFFINITY; LACTIDE POLYMERIZATION; AMIDINATE; COPPER(I) COMPLEXES; MODEL SYSTEMS; GUANIDINES; ABSORPTION
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201304882

Herein the synthesis, structures and properties of hydrogen‐bonded aggregates involving redox‐active guanidine superbases are reported. Reversible hydrogen bonding is switched on by oxidation of the hydrogen‐donor unit, and leads to formation of aggregates in which the hydrogen‐bond donor unit is sandwiched by two hydrogen‐bond acceptor units. Further oxidation (of the acceptor units) leads again to deaggregation. Aggregate formation is associated with a distinct color change, and the electronic situation could be described as a frozen stage on the way to hydrogen transfer. A further increase in the basicity of the hydrogen‐bond acceptor leads to deprotonation reactions. Hydrogen‐bond sandwich, anyone? After oxidation of guanidinyl‐functionalized aromatic compounds, the superbase is turned into a strong hydrogen‐bond donor and forms hydrogen‐bonded aggregates, which could be described as frozen stages on the way to hydrogen transfer (see figure).