Middlemolecule

Middlemolecule is an informal term used in some areas of chemistry and materials science to refer to a central molecular fragment that connects two environments, domains, or reactive sites. It is not part of standard chemical nomenclature, and its precise meaning varies by context. In practice, a middlemolecule describes a core scaffold that sits between two functional regions, thereby mediating interactions, properties, or assembly.

In organic synthesis, a middlemolecule may denote a transient intermediate that links two coupling partners in a convergent route, or a deliberately designed bifunctional core that anchors two reactive “wings” in a target molecule. In polymer science and supramolecular chemistry, the term can describe a short, modular core that bridges oligomeric units or host–guest components, influencing rigidity, electronic communication, and overall architecture. In molecular electronics and materials design, a middlemolecule can serve as a central conduit for charge transfer or as a tunable spacer between functional groups.

Common characteristics include a central scaffold with two or more attachment points, modularity for substituent variation, and the ability to adjust physical or electronic properties by changing the attached groups. Synthesis and characterization typically rely on standard organic or polymer chemistry techniques, supported by spectroscopic methods and, when relevant, crystallography or computational modeling to predict conformations and interactions.

Because middlemolecule is an informal label, definitions are inconsistent across literature. Users should rely on explicit descriptions of structure and role rather than the term alone. See also: molecular scaffold, linker, reaction intermediate, bifunctional molecule.