1. [obsolete] @[email protected] between a base and the conjugate acid of a different base through a @[email protected] (B' … HB+ or A'H … A). The term has its origin in the @[email protected] and is in no way related to @[email protected] of @[email protected] Heteroassociation is a more appropriate term.
  2. [obsolete] Some authors refer to @[email protected] containing a heteroatom, e.g. pyridine, as 'heteroconjugated systems'. This usage is discouraged since it inappropriately suggests an analogy to @[email protected], 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 [Terms] [Paper]