D_2d(23)-C₈₄ versus Sc₂C₂@D_2d(23)-C₈₄: Impact of Endohedral Sc₂C₂ Doping on Chemical Reactivity in the Photolysis of Diazirine

Abstract

We compared the chemical reactivity of D(23)-C and that of ScC@D(23)-C, both having the same carbon cage geometry, in the photolysis of 2-adamantane-2,3'-[3H]-diazirine, to clarify metal-atom doping effects on the chemical reactivity of the carbon cage. Experimental and computational studies have revealed that the chemical reactivity of the D(23)-C carbon cage is altered drastically by endohedral ScC doping. The reaction of empty D(23)-C with the diazirine under photoirradiation yields two adamantylidene (Ad) adducts. NMR spectroscopic studies revealed that the major Ad monoadduct (C(Ad)-A) has a fulleroid structure and that the minor Ad monoadduct (C(Ad)-B) has a methanofullerene structure. The latter was also characterized using X-ray crystallography. C(Ad)-A is stable under photoirradiation, but it interconverted to C(Ad)-B by heating at 80 °C. In contrast, the reaction of endohedral ScC@D(23)-C with diazirine under photoirradiation affords four Ad monoadducts (ScC@C(Ad)-A, ScC@C(Ad)-B, ScC@C(Ad)-C, and ScC@C(Ad)-D). The structure of ScC@C(Ad)-C was characterized using X-ray crystallography. Thermal interconversion of ScC@C(Ad)-A and ScC@C(Ad)-B to ScC@C(Ad)-C was also observed. The reaction mechanisms of the Ad addition and thermal interconversion were elucidated from theoretical calculations. Calculation results suggest that C(Ad)-B and ScC@C(Ad)-C are thermodynamically favorable products. Their different chemical reactivities derive from ScC doping, which raises the HOMO and LUMO levels of the D(23)-C carbon cage.

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

“…Interestingly,i th as been reported that the reactivities of the empty fullerene C 84 (23) and endohedral fullerene Sc 2 C 2 @C 84 (23) in the photolysis of 2-adamantane-2,3'-[3H]diazirine were drastically different because of metal-atom doping effects. [15] In our present case of ah igh-temperature trifluoromethylation reaction, no obvious difference in the reactivity between C 84 (23) and YCN@C 84 (23) was observed in terms of the similarity in the extent of CF 3 addition under approximately the same reaction conditions,t hus revealing the dependence of the chemical reactivity on the endohedral metal cluster. [1,2] Another new isomer of YCN@C 84 ,Y CN@C 84 (13), was further discovered as at rifluoromethyl derivative obtained from the YCN@C 84 /Y 2 C 2 @C 82 subfraction.…”

“…Three isomers (I–III) were isolated and structurally characterized by X‐ray diffraction study with the use of synchrotron radiation. The IPR isomer C 2 ‐C 84 (13) of the empty fullerene C 84 has never been isolated from the raw fullerene soot because of its very high relative formation energy of +91.4 kJ mol −1 , while the most unstable IPR isomer of C 84 , confirmed experimentally, is C 2 v ‐C 84 (18) with a relative formation energy of +67.3 kJ mol −1 . However, stability principles of endohedral fullerenes differ from those of empty fullerenes because of the charge transfer from the encapsulated metal to the cage .…”

Crystallographic and Theoretical Investigations of Er2@C2 n (2 n=82, 84, 86): Indication of Distance‐Dependent Metal–Metal Bonding Nature

“…More detailsa re listed in Ta ble S1 (in the SupportingI nformation). Particularly,t he characteristic peaks of Er 2 C 84 are largely redshiftedi nc omparison with that of the reported Lu 2 @D 2d (23)-C 84 [12a] and Sc 2 C 2 @D 2d (23)-C 84 , [22] indicating the difference of the cage symmetry,b ecause the Vis-NIR absorption of EMFs are mostlyd ue to p-p*transitions of the fullerene cage, which are determined by the isomeric structure and the charge state of the cage. [23] As expected,t he spectra of Er 2 C 82 (I), Er 2 C 82 (II), and Er 2 C 86 isomers are quite similar to that of the crystallographicallyc haracterized Lu 2 @C s (6)-C 82 ,L u 2 @C 3v (8)-C 82 ,a nd Lu 2 @C 2v (9)-C 86 ,r espectively, [12a] which is ah allmark of the same electronics tructure and cage symmetry for the corresponding Er 2 @C 82,86 isomers.…”

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

“…Zuschriften Interestingly,i th as been reported that the reactivities of the empty fullerene C 84 (23) and endohedral fullerene Sc 2 C 2 @C 84 (23) in the photolysis of 2-adamantane-2,3'-[3H]diazirine were drastically different because of metal-atom doping effects. [15] In our present case of ah igh-temperature trifluoromethylation reaction, no obvious difference in the reactivity between C 84 (23) and YCN@C 84 (23) was observed in terms of the similarity in the extent of CF 3 addition under approximately the same reaction conditions,t hus revealing the dependence of the chemical reactivity on the endohedral metal cluster. [1,2] Another new isomer of YCN@C 84 ,Y CN@C 84 (13), was further discovered as at rifluoromethyl derivative obtained from the YCN@C 84 /Y 2 C 2 @C 82 subfraction.…”

“…Three isomers (I-III) were isolated and structurally characterized by X-ray diffraction study with the use of synchrotron radiation. The IPR isomer C 2 -C 84 (13) of the empty fullerene C 84 has never been isolated from the raw fullerene soot because of its very high relative formation energy of + 91.4 kJ mol À1 , [15] while the most unstable IPR isomer of C 84 ,confirmed experimentally,is C 2v -C 84 (18) with ar elative formation energy of + 67.3 kJ mol À1 . [14,16] However,s tability principles of endohedral fullerenes differ from those of empty fullerenes because of the charge transfer from the encapsulated metal to the cage.…”