semiimine
Semiimine is a nonstandard term used in some branches of chemistry to describe species that exhibit imine-like character while not being a fully formed imine, or to refer to systems that contain both imine and amine functionalities. There is no formal IUPAC definition, and as a result the meaning of semiimine varies among authors. In practice, semi-imine descriptions are often encountered in contexts such as reductive amination intermediates where the C=N bond is only partially reduced, leaving residual imine character alongside amine-like features. The term is also used for certain ligands in coordination chemistry in which a C=N unit is modified by protonation, conjugation, or other substitutions, giving a structure that sits between an imine and an amine; such motifs can alter binding properties and electron density at a metal center. In polymer and materials chemistry, semi-imine motifs may arise in dynamic covalent systems or in partially hydrolyzed or conjugated imine networks, where optical, thermal, or mechanical properties reflect mixed character.
Relation to other functional groups: Semiimine is not a precise substitute for imine, iminium, amidine, or Schiff
See also: imine, iminium, amidine, Schiff base, dynamic covalent chemistry.