1. [obsolete] Association between a base and the conjugate acid of a different base through a hydrogen bond (B' … HB+ or A'H … A). The term has its origin in the conjugate acid–base pair and is in no way related to conjugated systems of orbitals. Heteroassociation is a more appropriate term.
  2. [obsolete] Some authors refer to conjugated systems containing a heteroatom, e.g. pyridine, as 'heteroconjugated systems'. This usage is discouraged since it inappropriately suggests an analogy to homoconjugation, and conflicts with the currently accepted definition of that term.
PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1120 (https://doi.org/10.1351/pac199466051077)