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Bonding in Endohedral Metallofullerenes as Studied by Quantum Theory of Atoms in Molecules
Author(s) -
Popov Alexey A.,
Dunsch Lothar
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901045
Subject(s) - delocalized electron , crystallography , chemistry , metal , molecule , ionic bonding , atoms in molecules , electron localization function , natural bond orbital , ion , density functional theory , computational chemistry , electron , physics , organic chemistry , quantum mechanics
Metal–cage and intracluster bonding was studied in detail by quantum theory of atoms in molecules (QTAIM) for the four major classes of endohedral metallofullerenes (EMFs), including monometallofullerenes Ca@C 72 , La@C 72 , M@C 82 (M=Ca, Sc, Y, La), dimetallofullerenes Sc 2 @C 76 , Y 2 @C 82 , Y 2 @C 79 N, La 2 @C 78 , La 2 @C 80 , metal nitride clusterfullerenes Sc 3 N@C 2 n (2 n =68, 70, 78, 80), Y 3 N@C 2 n (2 n =78, 80, 82, 84, 86, 88), La 3 N@C 2 n (2 n =88, 92, 96), metal carbide clusterfullerenes Sc 2 C 2 @C 68 , Sc 2 C 2 @C 82 , Sc 2 C 2 @C 84 , Ti 2 C 2 @C 78 , Y 2 C 2 @C 82 , Sc 3 C 2 @C 80 , as well as Sc 3 CH@C 80 and Sc 4 O x @C 80 ( x =2, 3), that is, 42 EMF molecules and ions in total. Analysis of the delocalization indices and bond critical point (BCP) indicators such as G bcp / ρ bcp , H bcp / ρ bcp , and |V bcp |/ G bcp , revealed that all types of bonding in EMFs exhibit a high degree of covalency, and the ionic model is reasonable only for the Ca‐based EMFs. Metal–metal bonds with negative values of the electron‐density Laplacian were found in Y 2 @C 82 , Y 2 @C 79 N, Sc 4 O 2 @C 80 , and anionic forms of La 2 @C 80 . A delocalized nature of the metal–cage bonding results in a topological instability of the electron density in EMFs with an unpredictable number of metal–cage bond paths and large elipticity values.