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La 2 @ C s (17 490)‐C 76 : A New Non‐IPR Dimetallic Metallofullerene Featuring Unexpectedly Weak Metal–Pentalene Interactions
Author(s) -
Suzuki Mitsuaki,
Mizorogi Naomi,
Yang Tao,
Uhlik Filip,
Slanina Zdenek,
Zhao Xiang,
Yamada Michio,
Maeda Yutaka,
Hasegawa Tadashi,
Nagase Shigeru,
Lu Xing,
Akasaka Takeshi
Publication year - 2013
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.201302821
Subject(s) - metallofullerene , pentalene , chemistry , fullerene , crystallography , metal , atom (system on chip) , cocrystal , synthon , pentagon , stereochemistry , molecule , hydrogen bond , organic chemistry , embedded system , computer science , political science , law
Although all the pure‐carbon fullerene isomers above C 60 reported to date comply with the isolated pentagon rule (IPR), non‐IPR structures, which are expected to have different properties from those of IPR species, are obtainable either by exohedral modification or by endohedral atom doping. This report describes the isolation and characterization of a new endohedral metallofullerene (EMF), La 2 @C 76 , which has a non‐IPR fullerene cage. The X‐ray crystallographic result for the La 2 @C 76 /[Ni II (OEP)] (OEP=octaethylporphyrin) cocrystal unambiguously elucidated the C s (17 490)‐C 76 cage structure, which contains two adjacent pentagon pairs. Surprisingly, multiple metal sites were distinguished from the X‐ray data, which implies dynamic behavior for the two La 3+ cations inside the cage. This dynamic behavior was also corroborated by variable‐temperature 139 La NMR spectroscopy. This phenomenon conflicts with the widely accepted idea that the metal cations in non‐IPR EMFs invariably coordinate strongly with the negatively charged fused‐pentagon carbons, thereby providing new insights into modern coordination chemistry. Furthermore, our electrochemical and computational studies reveal that La 2 @ C s (17 490)‐C 76 has a larger HOMO–LUMO gap than other dilanthanum‐EMFs with IPR cage structures, such as La 2 @ D 3 h (5)‐C 78 and La 2 @ I h (7)‐C 80 , which implies that IPR is no longer a strict rule for EMFs.