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Investigating the possibility of simultaneously finding an electron‐hole and an electron‐pair in a molecule: Delocalization, competition of ionic vs. covalent character, and related effects in push–pull ethylenes
Author(s) -
Karafiloglou Padeleimon,
Marcos Enrique Sánchez
Publication year - 1992
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560440304
Subject(s) - delocalized electron , ionic bonding , chemistry , covalent bond , electron , electronic correlation , molecule , electron pair , ab initio , electron localization function , computational chemistry , chemical physics , molecular physics , crystallography , ion , physics , quantum mechanics , organic chemistry
This work examines the possibility of finding an electron‐hole and an electron‐pair simultaneously in a π‐system substituted by an electron‐donating (NH 2 ) and/or electron‐withdrawing (NO 2 ) group. The contributions of various ionic [(+), ( ↑ ↓ )] structures are calculated from ab initio SCF – CI wave functions, using a recently developed general multielectron population analysis. The molecules studied are two monosubstituted ethylenes, aminoethylene and nitroethylene, and a disubstituted ethylene, the 2‐nitroethenamine (push–pull ethylene) in its two configurational forms. The influence of the NH 2 and/or NO 2 group in delocalization and ionic (vs. covalent) character of the CC double bond are investigated, along with examining the experimental chemist formalism of electron‐pair “displacements” in several resonance structures. Analysis of mutual dependence of an electron‐hole and an electron‐pair, at short and long distances, leads to the conclusion that a push–pull π‐system can stimulate the simultaneous existence of an electronhole and an electron‐pair even for nonvicinal positions. The relationship between the electronpair distributions and contributions of the corresponding structures are also examined; the effects of electronic correlation are analyzed as well. © 1992 John Wiley & Sons, Inc.