1
|
Bhattacharyya A, Sahu A, Patra S, Tiwari V. Low- and high-frequency vibrations synergistically enhance singlet exciton fission through robust vibronic resonances. Proc Natl Acad Sci U S A 2023; 120:e2310124120. [PMID: 38019862 PMCID: PMC10710028 DOI: 10.1073/pnas.2310124120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 10/14/2023] [Indexed: 12/01/2023] Open
Abstract
Singlet exciton fission (SEF) is initiated by ultrafast internal conversion of a singlet exciton into a correlated triplet pair [Formula: see text]. The "reaction coordinates" for ultrafast SEF even in archetypal systems such as pentacene thin film remain unclear. Couplings between fast electrons and slow nuclei are ubiquitous across a range of phenomena in chemistry. Accordingly, spectroscopic detection of vibrational coherences in the [Formula: see text] photoproduct motivated investigations into a possible role of vibronic coupling, akin to that reported in several photosynthetic proteins. However, acenes are very different from chlorophylls with 10× larger vibrational displacements upon photoexcitation and low-frequency vibrations modulating intermolecular orbital overlaps. Whether (and if so how) these unique features carry any mechanistic significance for SEF remains a poorly understood question. Accordingly, synthetic design of new molecules aiming to mimic this process across the solar spectrum has broadly relied on tuning electronic couplings. We address this gap and identify previously unrecognized synergistic interplay of vibrations, which in striking contrast to photosynthesis, vitally enhances SEF across a broad, nonselective and, therefore, unavoidable range of vibrational frequencies. We argue that attaching mechanistic significance to spectroscopically observed prominent quantum beats is misleading. Instead, we show that vibronic mixing leads to anisotropic quantum beats and propose readily implementable polarization-based two-dimensional electronic spectroscopy experiments which uniquely distinguish vibrations which drive vibronic mixing and promote SEF, against spectator vibrations simply accompanying ultrafast internal conversion. Our findings introduce crucial ingredients in synthetic design of SEF materials and spectroscopy experiments aiming to decipher mechanistic details from quantum beats.
Collapse
Affiliation(s)
- Atandrita Bhattacharyya
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore560012, India
| | - Amitav Sahu
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore560012, India
| | - Sanjoy Patra
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore560012, India
| | - Vivek Tiwari
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore560012, India
| |
Collapse
|
2
|
Rafiq S, Weingartz NP, Kromer S, Castellano FN, Chen LX. Spin-vibronic coherence drives singlet-triplet conversion. Nature 2023; 620:776-781. [PMID: 37468632 DOI: 10.1038/s41586-023-06233-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 05/18/2023] [Indexed: 07/21/2023]
Abstract
Design-specific control over the transitions between excited electronic states with different spin multiplicities is of the utmost importance in molecular and materials chemistry1-3. Previous studies have indicated that the combination of spin-orbit and vibronic effects, collectively termed the spin-vibronic effect, can accelerate quantum-mechanically forbidden transitions at non-adiabatic crossings4,5. However, it has been difficult to identify precise experimental manifestations of the spin-vibronic mechanism. Here we present coherence spectroscopy experiments that reveal the interplay between the spin, electronic and vibrational degrees of freedom that drive efficient singlet-triplet conversion in four structurally related dinuclear Pt(II) metal-metal-to-ligand charge-transfer (MMLCT) complexes. Photoexcitation activates the formation of a Pt-Pt bond, launching a stretching vibrational wavepacket. The molecular-structure-dependent decoherence and recoherence dynamics of this wavepacket resolve the spin-vibronic mechanism. We find that vectorial motion along the Pt-Pt stretching coordinates tunes the singlet and intermediate-state energy gap irreversibly towards the conical intersection and subsequently drives formation of the lowest stable triplet state in a ratcheting fashion. This work demonstrates the viability of using vibronic coherences as probes6-9 to clarify the interplay among spin, electronic and nuclear dynamics in spin-conversion processes, and this could inspire new modular designs to tailor the properties of excited states.
Collapse
Affiliation(s)
- Shahnawaz Rafiq
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Nicholas P Weingartz
- Department of Chemistry, Northwestern University, Evanston, IL, USA
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL, USA
| | - Sarah Kromer
- Department of Chemistry, North Carolina State University, Raleigh, NC, USA
| | - Felix N Castellano
- Department of Chemistry, North Carolina State University, Raleigh, NC, USA.
| | - Lin X Chen
- Department of Chemistry, Northwestern University, Evanston, IL, USA.
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL, USA.
| |
Collapse
|
3
|
Patra S, Tiwari V. Vibronic resonance along effective modes mediates selective energy transfer in excitonically coupled aggregates. J Chem Phys 2022; 156:184115. [PMID: 35568533 DOI: 10.1063/5.0088855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We recently proposed effective normal modes for excitonically coupled aggregates that exactly transform the energy transfer Hamiltonian into a sum of one-dimensional Hamiltonians along the effective normal modes. Identifying physically meaningful vibrational motions that maximally promote vibronic mixing suggested an interesting possibility of leveraging vibrational-electronic resonance for mediating selective energy transfer. Here, we expand on the effective mode approach, elucidating its iterative nature for successively larger aggregates, and extend the idea of mediated energy transfer to larger aggregates. We show that energy transfer between electronically uncoupled but vibronically resonant donor-acceptor sites does not depend on the intermediate site energy or the number of intermediate sites. The intermediate sites simply mediate electronic coupling such that vibronic coupling along specific promoter modes leads to direct donor-acceptor energy transfer, bypassing any intermediate uphill energy transfer steps. We show that the interplay between the electronic Hamiltonian and the effective mode transformation partitions the linear vibronic coupling along specific promoter modes to dictate the selectivity of mediated energy transfer with a vital role of interference between vibronic couplings and multi-particle basis states. Our results suggest a general design principle for enhancing energy transfer through synergistic effects of vibronic resonance and weak mediated electronic coupling, where both effects individually do not promote efficient energy transfer. The effective mode approach proposed here paves a facile route toward four-wavemixing spectroscopy simulations of larger aggregates without severely approximating resonant vibronic coupling.
Collapse
Affiliation(s)
- Sanjoy Patra
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Vivek Tiwari
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
| |
Collapse
|
4
|
Sahu A, Kurian JS, Tiwari V. Vibronic resonance is inadequately described by one-particle basis sets. J Chem Phys 2020; 153:224114. [DOI: 10.1063/5.0029027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Affiliation(s)
- Amitav Sahu
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Jo Sony Kurian
- Department of Chemistry, Indian Institute of Science Education and Research, Bhopal, Madhya Pradesh 462066, India
| | - Vivek Tiwari
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
| |
Collapse
|
5
|
Foster PW, Jonas DM. Nonadiabatic conical nodes are near but not at an elliptical conical intersection. Chem Phys 2019. [DOI: 10.1016/j.chemphys.2019.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
6
|
Zhang Z, Wang C, Zhang Z, Luo Y, Sun S, Zhang G. Cd(II) enhanced fluorescence and Zn(II) quenched fluorescence with phenylenevinylene terpyridine: A theoretical investigation. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2019; 209:40-48. [PMID: 30343108 DOI: 10.1016/j.saa.2018.10.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 10/02/2018] [Accepted: 10/12/2018] [Indexed: 06/08/2023]
Abstract
Phenylenevinylene terpyridine (mepvpt) shows chelation enhanced fluorescence (CHEF) with Cd(II) and chelation quenched fluorescence (CHQF) with Zn(II), respectively. To understand the behaviors, we studied their intrinsic optical properties using DFT/TDDFT methods. The results show that fluorescence quantum yields (FQY) of mepvpt, mepvpt-Cd and mepvpt-Zn are low due to high ISC rates from higher excited states rather than the S1 excited state. When mepvpt chelates Cd(II), the molecular structure becomes more planar and S3,4 → S0 radiation rates become higher than that of mepvpt, which results in CHEF. When mepvpt chelates Zn(II), a new S4 → S0 emission with low oscillator strength occurs and high S4 → Tn ISC rates appear, which leads to CHQF. This proposed mechanism of metal fluorescence enhancing/quenching suggests a design strategy for single-molecular multi-analyte sensors.
Collapse
Affiliation(s)
- Zhiyong Zhang
- Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Beijing 102249, China
| | - Chengjun Wang
- College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xian, Shaanxi 710021, China; Shaanxi Extend Oil (Group) Co., LTD. Research Institute, Xian, Shaanxi 710075, China.
| | - Zhongzhi Zhang
- Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Beijing 102249, China
| | - Yijing Luo
- Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Beijing 102249, China
| | - Shanshan Sun
- Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Beijing 102249, China
| | - Guangqing Zhang
- School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522, Australia
| |
Collapse
|
7
|
Jonas DM. Vibrational and Nonadiabatic Coherence in 2D Electronic Spectroscopy, the Jahn–Teller Effect, and Energy Transfer. Annu Rev Phys Chem 2018; 69:327-352. [DOI: 10.1146/annurev-physchem-052516-050602] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- David M. Jonas
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA
| |
Collapse
|
8
|
Tiwari V, Jonas DM. Electronic energy transfer through non-adiabatic vibrational-electronic resonance. II. 1D spectra for a dimer. J Chem Phys 2018; 148:084308. [DOI: 10.1063/1.5003193] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Vivek Tiwari
- Department of Chemistry and Biochemistry, University of Colorado, 215 UCB, Boulder, Colorado 80309, USA
| | - David M. Jonas
- Department of Chemistry and Biochemistry, University of Colorado, 215 UCB, Boulder, Colorado 80309, USA
| |
Collapse
|
9
|
Foster PW, Jonas DM. Nonadiabatic Eigenfunctions Can Have Amplitude, Signed Conical Nodes, or Signed Higher Order Nodes at a Conical Intersection with Circular Symmetry. J Phys Chem A 2017; 121:7401-7413. [DOI: 10.1021/acs.jpca.7b07140] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Peter W. Foster
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - David M. Jonas
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
| |
Collapse
|