It is known that very strong hydrogen bonds can occur in charged systems, such as $\ce{[F-}\ce{-H+-F-]}$, while hydrogen bonds in neutral systems are much weaker in comparison.
What is the strongest known hydrogen bond within the following specifications?
- both donor and acceptor monomers are neutral, and remain neutral upon association (no ionic bridges);
- heterodimers are allowed (e.g. hydrogen fluoride and ammonia);
- must be a single-site hydrogen bond - excluding dimers stabilized by multiple hydrogen bonds such as nucleobase pairs.