Fei Jin

Mononuclear Clusterfullerene Single-Molecule Magnet Containing Strained Fused-Pentagons Stabilized by a Nearly Linear Metal Cyanide Cluster

Abstract Fused‐pentagons results in an increase of local steric strain according to the isolated pentagon rule (IPR), and for all reported non‐IPR clusterfullerenes multiple (two or three) metals are required to stabilize the strained fused‐pentagons, making it difficult to access the single‐atom properties. Herein, we report the syntheses and isolations of novel non‐IPR mononuclear clusterfullerenes MNC@C76 (M=Tb, Y), in which one pair of strained fused‐pentagon is stabilized by a mononuclear cluster. The molecular structures of MNC@C76 (M=Tb, Y) were determined unambiguously by single‐crystal X‐ray diffraction, featuring a non‐IPR C 2v(19138)‐C76 cage entrapping a nearly linear MNC cluster, which is remarkably different from the triangular MNC cluster within the reported analogous clusterfullerenes based on IPR‐obeying C82 cages. The TbNC@C76 molecule is found to be a field‐induced single‐molecule magnet (SMM).

Skeletal Transformation of a Classical Fullerene C88 into a Nonclassical Fullerene Chloride C84Cl30 Bearing Quaternary Sequentially Fused Pentagons

A classical fullerene is composed of hexagons and pentagons only, and its stability is generally determined by the Isolated-Pentagon-Rule (IPR). Herein, high-temperature chlorination of a mixture containing a classical IPR-obeying fullerene C88 resulted in isolation and X-ray crystallographic characterization of non-IPR, nonclassical (NC) fullerene chloride C84(NC2)Cl30 (1) containing two heptagons. The carbon cage in C84(NC2)Cl30 contains 14 pentagons, 12 of which form two pairs of fused pentagons and two groups of quaternary sequentially fused pentagons, which have never been observed in reported carbon cages. All 30 Cl atoms form an unprecedented single chain of ortho attachments on the C84 cage. A reconstruction of the pathway of the chlorination-promoted skeletal transformation revealed that the previously unknown IPR isomer C88(3) is converted into 1 by two losses of C2 fragments followed by two Stone-Wales rearrangements, resulting in the formation of very stable chloride with rather short C-Cl bonds.

Experimental and Theoretical Approach to Variable Chlorination-Promoted Skeletal Transformations in Fullerenes: The Case of C102

The first example of three alternative chlorination-promoted skeletal transformation pathways in the same fullerene cage is presented. Isolated-pentagon-rule (IPR) C102(19) undergoes both Stone-Wales rotations to give non-IPR #283794C102Cl20 and C2 losses to form nonclassical C98 and non-IPR C96. X-ray structural characterization of the transformation products and a theoretical study of their formation pathways are reported.

Singly Bonded Monoadduct rather than Methanofullerene: Manipulating the Addition Pattern of Trimetallic Nitride Clusterfullerene through One Endohedral Metal Atom Substitution

Bingel-Hirsch reactions of trimetallic nitride clusterfullerenes (NCFs) generally yield methanofullerene (cyclopropane) adducts instead of singly bonded derivatives, which have been reported for monometallofullerenes. Herein, we report the synthesis and characterization of the Bingel-Hirsch derivative of a mixed metal nitride clusterfullerene (MMNCF) TiY2 N@Ih -C80 . Surprisingly, in contrast to the reported Bingel-Hirsch cyclopropane adducts of the analogous NCF Y3 N@Ih -C80 , the Bingel-Hirsch derivative of TiY2 N@Ih -C80 is the first singly bonded monoadduct (labeled as TiY2 N@C80 -Mono) to be reported, which was determined unambiguously by single-crystal X-ray crystallography. Besides, the reactivity of TiY2 N@Ih -C80 was found to be significantly improved relative to that of Y3 N@Ih -C80 . Upon substituting one endohedral yttrium (Y) atom of Y3 N@Ih -C80 with titanium (Ti), the Bingel-Hirsch derivative changes from the cyclopropane to the singly bonded monoadduct, revealing that not only the reactivity but also the addition pattern of NCFs can be manipulated simultaneously through one endohedral metal atom substitution.

New Isolated-Pentagon-Rule Isomers of Fullerene C98 Captured as Chloro Derivatives

Fullerene C98 possesses 259 isomers obeying the isolated pentagon rule (IPR), from which two, nos. 116 and 248, have been confirmed earlier as chloro derivatives. High-temperature chlorination of C98-containing mixtures afforded crystals of several chloro derivatives, and their structure elucidation by X-ray crystallography revealed the presence of new isomers, nos. 107, 109, and 120, in the fullerene soot. Evidence for an isomer of no. 111 is also presented. In addition, a new chloride of the known isomer 248 has been isolated and structurally studied. The chlorination patterns of the chlorides are discussed in terms of the formation of isolated C═C bonds and aromatic substructures on the fullerene cages.

Chloro Derivatives of Isomers of a Giant Fullerene C104: C104(234)Cl16/18, C104(812)Cl12/24, and C104(811)Cl28

The chemistry of a giant fullerene, C104 , has been extended by the synthesis and structural study of several chloro derivatives of three isolated pentagon rule (IPR) isomers of C104 nos. 234, 812, and 811. In the structure of C104 (234)Cl16/18 , two molecules with 16 and 18 attached Cl atoms occupy the same crystallographic site with an occupancy ratio of 61/39. The structures of C104 (812)Cl12 and C104 (812)Cl24 demonstrate substructure relationships of their chlorination patterns with single and double Cl attachments to 12 cage pentagons. The structure of C104 (811)Cl28 is compared with the known C104 (811)Cl24 thus revealing dramatic changes in the chlorination pattern, which occur with relatively small increases in the degree of chlorination.

Synthesis, Isolation, and Trifluoromethylation of Two Isomers of C84-Based Monometallic Cyanide Clusterfullerenes: Interplay between the Endohedral Cluster and the Exohedral Addends

As an emerging member of endohedral fullerenes, metal cyanide clusterfullerenes (CYCF) are unique in terms of the encapsulation of a monometallic cluster. To date the reported carbon cages of CYCFs are limited to C82 and C76 , and little is known about the chemical reactivity of CYCFs. Herein, two isomers of the first C84 -based CYCFs, YCN@C84 , were isolated as trifluoromethyl derivatives, including YCN@C84 (23)(CF3 )18 and three isomers of YCN@C84 (13)(CF3 )16 , which are based on a unique chiral C2 -C84 (13) cage. As a common feature of the CF3 addition patterns, the YCN@C84 (CF3 )16/18 compounds are stabilized by the formation of isolated C=C bonds and benzenoid rings on the carbon cages. The interplay between the endohedral YCN cluster and the exhohedral CF3 addends was unveiled according to single-crystal X-ray diffraction studies, thus offering new insight into the chemical reactivity of CYCFs.

Steering the Geometry of Butterfly-Shaped Dimetal Carbide Cluster within a Carbon Cage via Trifluoromethylation of Y2C2@C82(6)

As one of the largest sub-branches of endohedral clusterfullerenes, dimetal carbide clusterfullerene (CCF) in the form of M2C2@C2 n is quite intriguing since an alternative structure of M2@C2 n+2 as conventional dimetallofullerene may exist as well. Herein, by using high-temperature trifluoromethylation followed by HPLC separation and single-crystal X-ray diffraction study, we report for the first time the unambiguous structural determination of yttrium (Y)-based CCF as its trifluoromethyl derivatives, Y2C2@C82(6)(CF3)16. Four isomers of Y2C2@C82(6)(CF3)16 with different addition patterns of 16 CF3 groups are successfully isolated, and two Y atoms of the butterfly-shaped Y2C2 cluster are coordinated by two cage pentagons in each isomer. The butterfly geometry of Y2C2 cluster varies significantly in the four Y2C2@C82(6)(CF3)16 isomers, with Y···Y distances ranging from 3.544 to 4.051 Å dependent on the relative positions of the two yttrium-coordinated pentagons on the carbon cage.