Syntheses and crystal structures of azafulleroid and aziridinofullerene bearing silyl or germyl benzene

Hachiya, Houjin; Kakuta, Toshiyuki; Takami, Makoto; Kabe, Yoshio

doi:10.1016/j.jorganchem.2008.11.049

Cited by 21 publications

(12 citation statements)

References 60 publications

(2 reference statements)

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“…[15] Meanwhile, the reaction of organic azides is another important method for the functionalization of fullerenes, which has shown its effectiveness to produce many novel derivatives with different structures. [16][17][18][19][20] The bis-addition reactions of azides with C 60 are more complicated because of the large number of isomers that may form in the mixture and the difficulties lying in the complete isolation and concrete structural characterization of the bis-adducts, leaving a long confusion about the thermolysis mechanism of bis-triazoline derivatives of fullerenes. [21] As a result, the tether-directed strategy was also adopted for the regioselective synthesis of bis-adducts of C 60 following the azide addition.…”

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confidence: 99%

Rigid Tether Directed Regioselective Synthesis and Crystallographic Characterization of Labile 1,2,3,4‐Bis(triazolino)[60]fullerene and Its Thermolized Derivatives

et al. 2016

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Labile bis-triazoline adducts of C60 are supposed to be the precursors of bis-azafulleroids, but the formation mechanism is still unclear because of the incomplete isolation of the thermolized products and the lack of X-ray structures. A rigid-tethered reagent 1,2-bis(azidomethyl)benzene (1) was used to regioselectively synthesize the labile 1,2,3,4-bis(triazolino)[60]-fullerene (2), the structure of which was determined by single-crystal X-ray crystallography. Further thermolysis of 2 produces four products (3 a-3 d), which were all characterized by X-ray crystallography. Although 3 a and 3 b have traditional bis-azafulleroid structures, as proposed previously, 3 c and 3 d show unprecedented structures with either the coexistence of [5,6]-open and [6,6]-closed patterns or an oxidized structure with an 11-membered ring on the cage. A thermolysis mechanism is proposed to clarify long-term confusion about the transformation process from bis-triazoline adducts to bis-azafulleroids of C60 .

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confidence: 99%

Rigid Tether Directed Regioselective Synthesis and Crystallographic Characterization of Labile 1,2,3,4‐Bis(triazolino)[60]fullerene and Its Thermolized Derivatives

et al. 2016

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“…[11] Up to now, the tetherdirected methodology has been widely adopted to synthesize pure regioisomers of fullerene bis-adducts following different synthetic strategies, such as the Bingel-Hirsch reaction, [12] Prato reaction, [13] Diels-Alder cycloaddition, [14] and Diazo cycloaddition. [16][17][18][19][20] The bis-addition reactions of azides with C 60 are more complicated because of the large number of isomers that may form in the mixture and the difficulties lying in the complete isolation and concrete structural characterization of the bis-adducts, leaving a long confusion about the thermolysis mechanism of bis-triazoline derivatives of fullerenes. [16][17][18][19][20] The bis-addition reactions of azides with C 60 are more complicated because of the large number of isomers that may form in the mixture and the difficulties lying in the complete isolation and concrete structural characterization of the bis-adducts, leaving a long confusion about the thermolysis mechanism of bis-triazoline derivatives of fullerenes.…”

Section: Rigid Tether Directed Regioselective Synthesis and Crystallomentioning

confidence: 99%

Rigid Tether Directed Regioselective Synthesis and Crystallographic Characterization of Labile 1,2,3,4‐Bis(triazolino)[60]fullerene and Its Thermolized Derivatives

et al. 2016

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“…The 1,3-dipolar cycloaddition (1, of azide to the [6,6] bonds of C 60 followed by thermal extrusion of N 2 from the triazoline intermediate commonly leads to a mixture of two imino adducts, that is, open [5,6]-bridged azafulleroids and closed [6,6]-bridged aziridinofullerenes. [14][15][16][17][18][19] The ratio of these two species depends on the nature of the substituent. [15] The [6,6]triazoline intermediates lose N 2 immediately upon heating at temperatures slightly higher than 60 8C, [14,16,20] so this was not isolated or chemically characterized.…”

Section: Synthesismentioning

confidence: 99%

“…[14][15][16][17][18][19] The ratio of these two species depends on the nature of the substituent. [15] The [6,6]triazoline intermediates lose N 2 immediately upon heating at temperatures slightly higher than 60 8C, [14,16,20] so this was not isolated or chemically characterized. Thermal reaction of 13 with 1.5 equivalents of C 60 was performed in toluene at 100 8C under argon.…”

Section: Synthesismentioning

confidence: 99%

Photoinduced Charge Transfer in a Conformational Switching Chlorin Dimer–Azafulleroid in Polar and Nonpolar Media

Nikkonen

Oliva

Kahnt

et al. 2014

Chemistry A European J

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In the present study, a biomimetic reaction center model, that is, a molecular triad consisting of a chlorin dimer and an azafulleroid, is synthesized and its photophysical properties are studied in comparison with the corresponding molecular dyad, which consists only of a chlorin monomer and an azafulleroid. As evidenced by (1) H NMR, UV/Vis, and fluorescence spectroscopy, the chlorin dimer-azafulleroid folds in nonpolar media into a C2 -symmetric geometry through hydrogen bonding, resulting in appreciable electronic interactions between the chlorins, whereas in polar media the two chlorins diverge from contact. Femtosecond transient absorption spectroscopy studies reveal longer charge-separated states for the chlorin dimer-azafulleroid; ≈1.6 ns in toluene, compared with the lifetime of ≈0.9 ns for the corresponding chlorin monomer-azafulleroid in toluene. In polar media, for example, benzonitrile, similar charge-separated states are observed, but the lifetimes are inevitably shorter: 65 and 73 ps for the dimeric and monomeric chlorin-azafulleroids, respectively. Nanosecond transient absorption and singlet oxygen phosphorescence studies corroborate that in toluene, the charge-separated state decays indirectly via the triplet excited state to the ground state, whereas in benzonitrile, direct recombination to the ground state is observed. Complementary DFT studies suggest two energy-minima conformations, that is, a folded chlorin dimer-azafulleroid, which is present in nonpolar media, and another conformation in polar media, in which the two hydrophobic chlorins wrap the azafulleroid. Inspection of the frontier molecular orbitals shows that in the folded conformation, the HOMO on each chlorin is equivalent and is shared owing to partial π-π overlap, resulting in delocalization of the conjugated π electrons, whereas the wrapped conformation lacks this stabilization. As such, the longer charge-separated lifetime for the dimer is rationalized by both the electron donor-acceptor separation distance and the stabilization of the radical cation through delocalization. The chlorin folding seems to change the photophysical properties in a manner similar to that observed in the chlorophyll dimer in natural photosynthetic reaction centers.

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Syntheses and crystal structures of azafulleroid and aziridinofullerene bearing silyl or germyl benzene

Cited by 21 publications

References 60 publications

Rigid Tether Directed Regioselective Synthesis and Crystallographic Characterization of Labile 1,2,3,4‐Bis(triazolino)[60]fullerene and Its Thermolized Derivatives

Rigid Tether Directed Regioselective Synthesis and Crystallographic Characterization of Labile 1,2,3,4‐Bis(triazolino)[60]fullerene and Its Thermolized Derivatives

Rigid Tether Directed Regioselective Synthesis and Crystallographic Characterization of Labile 1,2,3,4‐Bis(triazolino)[60]fullerene and Its Thermolized Derivatives

Photoinduced Charge Transfer in a Conformational Switching Chlorin Dimer–Azafulleroid in Polar and Nonpolar Media

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