Related Experiment Video
Updated: Sep 21, 2025
11:44
Synthesis and Structure Determination of µ-Conotoxin PIIIA Isomers with Different Disulfide Connectivities
Published on: October 2, 2018
12.7K
Parallel versus Twisted Pentacenes: Conformational Impact on Singlet Fission.
Ilias Papadopoulos1, S Rajagopala Reddy2, Pedro B Coto3
1Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich Alexander-University Erlangen-Nuremberg, Egerlandstraße 3, 91058 Erlangen, Germany.
The Journal of Physical Chemistry Letters
|June 2, 2022
Summary
Singlet fission in pentacene molecules is influenced by excitation wavelength and molecular flexibility. Controlling molecular structure is key for efficient singlet fission (SF) materials.
Area of Science:
- Organic Photovoltaics
- Materials Science
- Photochemistry
Background:
- Singlet fission (SF) is a process where one high-energy exciton splits into two lower-energy triplet excitons.
- Understanding SF is crucial for developing next-generation solar cells with enhanced efficiency.
- Pentacene derivatives are promising candidates for SF materials due to their electronic properties.
Purpose of the Study:
- To investigate the influence of excitation wavelength, conformational flexibility, and vibronic coupling on singlet fission in pentacene dimers.
- To elucidate the dynamics of triplet pair formation and decay pathways.
Main Methods:
- Synthesis of pentacene-diacetylene molecules with chromophores at termini.
- Ultrafast spectroscopic techniques to probe excited-state dynamics.
- Temperature-dependent measurements to study conformational effects.
Main Results:
- Low-energy excitation forms a hot, delocalized triplet pair (1(T1T1)deloc) with a lifetime < 2 ps.
- High-energy excitation initially forms 1(T1T1)deloc (1.0 ps lifetime), decaying via triplet-triplet annihilation within 4 ps at room temperature.
- Lowering temperature promotes delocalization and vibronic decoupling, leading to localized triplet pairs (1(T1T1)loc).
- Diacetylene linker flexibility can lead to twisted conformations, significantly reducing SF quantum yields.
Conclusions:
- Excitation wavelength and temperature critically affect SF dynamics and triplet pair localization.
- Molecular design must control linker flexibility to optimize SF efficiency in pentacene-based materials.
- This study provides insights into designing molecules for efficient singlet fission applications.
Related Concept Videos
02:11Conformations of Cyclohexane
13.2K
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
13.2K
02:02Chair Conformation of Cyclohexane
15.5K
The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this...
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this...
15.5K
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
926
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
926
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
1.2K
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
1.2K
01:18Aromatic Hydrocarbon Cations: Structural Overview
3.1K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
Removing one hydrogen from the intervening CH2 group...
3.1K
01:28Stability of Conjugated Dienes
3.8K
Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
3.8K