Light-Induced Processes in Porphyrin-Fullerene Systems

Konev, Alexander S.

doi:10.1007/978-3-030-05974-3_22

Cited by 2 publications

(2 citation statements)

References 61 publications

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“…Fullerenes are a set of highly conjugated carbon allotropes akin to graphene and nanotubes that consist of a fully enclosed sp 2 cage brought on by the inclusion of 12 pentagons in their molecular structure. − Since their first theorization , and synthesis, fullerenes have been found in nature including in Precambrian rock and in interstellar nebulae/dust clouds. , Their interesting electronic nature , means they have found use in organic electronics in conjunction with other π–π conjugated materials like porphyrins − and organic polymers, , among others; , as antioxidants; − as electron acceptors in organic electronic devices; and in composite materials. − Despite this, their formation is peculiar and complex and involves multiple potential mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Role of Graphitic Bowls in Temperature Dependent Fullerene Formation

et al. 2022

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Fullerenes are used extensively in organic electronics as electron acceptors among other uses; however, there are still several key mysteries regarding their formation such as the importance of graphitic intermediates and the thermokinetics of initial cage formation. To this end, we have conducted density functional tight binding molecular dynamics (DFTB-MD) calculations on disintegrated I h -C60 to investigate the formation mechanisms of fullerenes at high temperature conditions. From the results of these DFTB-MD calculations we were able to develop a thermokinetic model to describe the free energies and kinetics of fullerene formation at a range of temperatures. Direct observation of the mechanism revealed fullerenes readily forming in nanosecond times between 2000 and 3000 K but were hindered above this temperature window. Analysis revealed temperature dependent formation mechanisms where at low temperatures (<2750K) flat graphitic bowls play an important part as metastable intermediates while highly curved bowls follow a direct fast transformation. Meanwhile at higher temperatures (>2750 K), flat bowls become the transitory structure between chains and fullerene. Free energy analysis from our thermokinetic model shows this change in graphitic bowls to being transitory hinders fullerene formation at high temperatures compared to lower temperatures, essentially kinetically trapping C60 as chain networks. This investigation gives new key insights into the formation mechanisms of C60 fullerenes and highlights important intermediates while also illuminating the temperature window for fullerene formation, facilitating better optimization of experimental methods.

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Section: Introductionmentioning

confidence: 99%

Role of Graphitic Bowls in Temperature Dependent Fullerene Formation

et al. 2022

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“…I h -C 60 exhibits several interesting properties besides its stability. These include entering a 3D equivalent to aromaticity in the +10 cation state, the ability to adsorb up to six electrons, allowing it to act as a strong electron acceptor, and the extensive π conjugation allows it to π–π stack with other materials such as porphyrins, − organic polymers, , and other materials. , Due to these properties and its ability to form composites, I h -C 60 has found uses as an antioxidant, − as electron acceptors in organic electronic devices, and in several other potentially useful composite materials. − With extensive novel uses, the actual dominance of I h -C 60 in nature and experimental production alike is poorly understood, particularly given the paradox of larger fullerenes being lower in energy. This lack of understanding is a significant hinderance in optimizing any process used in I h -C 60 production.…”

Section: Introductionmentioning

confidence: 99%

High Temperature Accelerated Stone–Wales Transformation and the Threshold Temperature of IPR-C₆₀ Formation

et al. 2021

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The Stone–Wales bond rotation isomerization of nonicosahedral C60 (C2v-C60) into isolated-pentagon rule following icosahedral C60 (Ih-C60 or IPR-C60) is a limiting step in the synthesis of Ih-C60. However, extensive previous studies indicate that the potential energy barrier of the Stone–Wales bond rotation is between 6 and 8 eV, extremely high to allow for bond rotation at the temperatures used to produce fullerenes conventionally. This is also despite data indicating a possible fullerene road mechanism that necessitates low-temperature annealing. However, these previous investigations often have limiting factors, such as using the harmonic approximation to determine free energies at high temperatures or considering only the reverse Ih-C60 to C2v-C60 transition as a basis. Indeed, when the difference in energy between Ih-C60 and C2v-C60 is accounted for, this barrier is generally reduced by ∼1.5 eV. Thus, utilizing the recently developed density functional tight binding metadynamics (DFTB-MTD) interface, the effects of temperature on the bond rotation in the conversion of C2v-C60 to Ih-C60 have been investigated. We found that Stone–Wales bond rotations are complex processes with both in-plane and out-of-plane transition states, and which transition path dominates depends on temperature. Our results clearly show that at temperatures of 2000 K, the free energy for a C2v-C60 to Ih-C60 transition is only ∼4.21 eV and further reduces to ∼3.77 eV at 3000 K. This translates to transition times of ∼971 μs at 2000 K and ∼34 ns at 3000 K, indicating that defect healing is a fast process at temperatures typical of arc jet or laser ablation experiments. Conversely, below ∼2000 K, bond rotation becomes prohibitively slow, putting a lower threshold limit on the temperature of fullerene formation and subsequent annealing.

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Light-Induced Processes in Porphyrin-Fullerene Systems

Cited by 2 publications

References 61 publications

Role of Graphitic Bowls in Temperature Dependent Fullerene Formation

Role of Graphitic Bowls in Temperature Dependent Fullerene Formation

High Temperature Accelerated Stone–Wales Transformation and the Threshold Temperature of IPR-C₆₀ Formation

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Light-Induced Processes in Porphyrin-Fullerene Systems

Cited by 2 publications

References 61 publications

Role of Graphitic Bowls in Temperature Dependent Fullerene Formation

Role of Graphitic Bowls in Temperature Dependent Fullerene Formation

High Temperature Accelerated Stone–Wales Transformation and the Threshold Temperature of IPR-C60 Formation

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High Temperature Accelerated Stone–Wales Transformation and the Threshold Temperature of IPR-C₆₀ Formation