Light harvesting articles within Nature Chemistry

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  • Article
    | Open Access

    Noble metals dominate the field of photosensitizers and luminophores. Now, an approach incorporating cyclometalating and carbene functions into FeIII complexes has been shown to enable dual emission from the opposing ligand-to-metal and metal-to-ligand charge-transfer states. The latter shows an exceptionally long lifetime of 4.6 ns and is quenched by oxygen and other quenchers.

    • Jakob Steube
    • , Ayla Kruse
    •  & Matthias Bauer

  • Article |

    Meso–meso linked porphyrin arrays have been described as rod-like photonic wires. Now it has been shown that they can be bent into rings using template-directed synthesis. These rings of porphyrins mimic the light-harvesting arrays of chlorophyll molecules responsible for photosynthesis.

    • Henrik Gotfredsen
    • , Jie-Ren Deng
    •  & Harry L. Anderson

  • Article |

    The principal mid-visible light-harvesting system in cyanobacteria is the phycobilisome. Now, using broadband multidimensional spectroscopy, delocalized vibronic excitations and sub-picosecond excitation transfer pathways have been observed in the rods of intact phycobilisomes. An observed kinetic bottleneck in the phycobilisome’s core arises from the intramolecular charge-transfer character of the bilin chromophores, enabling photoregulatory processes to operate on the >10-ps timescale.

    • Sourav Sil
    • , Ryan W. Tilluck
    •  & Warren F. Beck

  • Article |

    Molecular π-stacked chromophores are promising photonic materials, but much of our understanding is limited to covalent dimers. Now it has been shown that, in a slip-stacked perylenediimide trimer, coherent vibronic coupling to high-frequency modes facilitates ultrafast state mixing between the Frenkel exciton and charge-transfer states, which then collapses by solvent fluctuations and low-frequency vibronic coupling, resulting in ultrafast symmetry-breaking charge separation.

    • Chenjian Lin
    • , Taeyeon Kim
    •  & Michael R. Wasielewski

  • Article |

    The overall efficiency of free-triplet generation from intramolecular singlet fission is limited by the efficiency of the dissociation of spatially adjacent triplet pairs. Now, using transient magneto-optical spectroscopy, it has been shown that this limitation can be overcome by promoting a pathway mediated by spatially separated triplet pairs in tetracene trimers and tetramers.

    • Zhiwei Wang
    • , Heyuan Liu
    •  & Min Xiao

  • Article |

    Generating high-energy triplet excitons from singlet fission without excess energy loss is a critical goal for potential applications. Now it is shown that molecular chromophores that are connected covalently can harbour multiple long-lived and high-energy triplets—created from one photon—only if more than two chromophoric units are present and they have sufficient flexibility to isolate the excitations upon torsional motion.

    • Nadezhda V. Korovina
    • , Christopher H. Chang
    •  & Justin C. Johnson

  • Article |

    Replacing rare elements in benchmark photosensitizers with iron would facilitate the large-scale implementation of solar energy conversion, but iron complexes generally do not exhibit sufficiently long-lived photoexcited states. Now, it has been shown that iron(ii) complexes with carefully designed ligands can absorb broadly across the visible light spectrum and have charge-transfer excited states with nanosecond lifetimes.

    • Jason D. Braun
    • , Issiah B. Lozada
    •  & David E. Herbert

  • Article |

    Although they are synthetically tunable, organic molecules that undergo singlet fission (the generation of two excitons from one photon) have not demonstrated the excited-state properties necessary to improve optoelectronic devices. Now, a general ‘energy cleft’ molecular design scheme has been demonstrated that enables rapid generation and long lifetimes of multiple triplet excitons that are for device applications.

    • Andrew B. Pun
    • , Amir Asadpoordarvish
    •  & Matthew Y. Sfeir

  • Article |

    The implications of coherence signals for the transfer of energy within the Fenna–Matthews–Olson complex of photosynthetic green sulfur bacteria is a well debated topic. Now, polarization-controlled 2D spectroscopy — aided by vibronic exciton modelling — has enabled the characterization of all such coherences and determination of their physical origins; while electronic coherences dephase extremely rapidly, ground- and excited-state vibrational coherences dominate.

    • Erling Thyrhaug
    • , Roel Tempelaar
    •  & Donatas Zigmantas

  • Article |

    Singlet fission may one day allow solar cells to produce two excited electrons with one photon. Now, by comparison of the time-resolved photoluminescence and sensitized triplet–triplet annihilation of a tetracene derivative, it has been shown that—contrary to previous reports—the excimer state is a trap, and not a necessary intermediate for singlet fission.

    • Cameron B. Dover
    • , Joseph K. Gallaher
    •  & Timothy W. Schmidt

  • Article |

    Spectroscopists and theorists are closing in on an understanding of the origin of oscillatory features in the spectral response of light-harvesting complexes to femtosecond pulsed excitation. Now, the photosynthetic Fenna–Matthews–Olson complex is probed by femtosecond pump–probe spectroscopy and compared with a series of genetically modified mutants with distinct excitonic interactions, allowing electronic and vibrational contributions to coherence to be distinguished.

    • Margherita Maiuri
    • , Evgeny E. Ostroumov
    •  & Gregory D. Scholes

  • News & Views |

    The flow of energy in Earth's primary light harvesters — photosynthetic pigment–protein complexes — needs to be heavily regulated, as the sun's energy supply can vary over many orders of magnitude. Observing hundreds of individual light-harvesting complexes has now provided important insights into the machinery that regulates this process.

    • Peter J. Walla

  • Article |

    Photoprotection is crucial for the fitness of organisms that carry out oxygenic photosynthesis. LHCSR, a photosynthetic light-harvesting complex, has been implicated in photoprotection in green algae and moss. Now, single-molecule studies of LHCSR have revealed that multi-timescale protein dynamics underlie photoprotective dissipation of excess energy.

    • Toru Kondo
    • , Alberta Pinnola
    •  & Gabriela S. Schlau-Cohen

  • News & Views |

    The process of electronic energy transfer between molecules has long fascinated chemists. Femtosecond spectroscopy measurements of a series of molecular dimers now reveal signals that arise from non-Born–Oppenheimer coupling, suggesting a new mechanism to enhance energy transfer.

    • Daniel B. Turner

  • Article |

    Synthetic heterodimers provide a platform to demonstrate molecular design principles of vibronic coupling. Now, it has been shown that quantum beating caused by vibronic coupling can be controlled by packing a structurally flexible heterodimer on single-walled carbon nanotubes. This quantum beating requires a vibration to be resonant with the energy gap between excited states and structural rigidity.

    • Lili Wang
    • , Graham B. Griffin
    •  & Gregory S. Engel

  • Article |

    Singlet fission — the splitting of a singlet exciton into two triplets — is a process that could be exploited to improve the power conversion efficiency of solar cells. Spectroscopic data now suggest that coherent and incoherent mechanisms for singlet fission in crystalline hexacene coexist and occur on different timescales.

    • Nicholas R. Monahan
    • , Dezheng Sun
    •  & X.-Y. Zhu

  • Article |

    A primary objective in solar energy conversion is to achieve long-lived light-driven redox separation. Now a modular self-assembly strategy has been developed to construct molecular p/n junctions surface-bound to transparent conducting ITO nanoparticle electrodes. Both photoanode and photocathode assemblies achieved remarkably long-lived redox separation lifetimes without making use of traditional wide-bandgap semiconductors.

    • Byron H. Farnum
    • , Kyung-Ryang Wee
    •  & Thomas J. Meyer

  • Article |

    Effective light capture in photosynthetic organisms depends on the efficiency of all energy-transfer steps in the photosynthetic unit. Two-dimensional electronic spectroscopy has now been used on intact cells in situ to reveal and characterize the functional connectivity between individual complexes in the photosynthetic apparatus of green sulfur bacteria.

    • Jakub Dostál
    • , Jakub Pšenčík
    •  & Donatas Zigmantas

  • News & Views |

    For many years, chemists have tried and failed to find efficient light-harvesting molecules based on Earth-abundant, environmentally friendly iron. Now, an iron complex has been developed with photoluminescent properties that are tuned to efficiently convert light to electrons.

    • Elena Galoppini

  • Article |

    Using iron instead of the scarce ruthenium in light-harvesting complexes is challenging because iron complexes generally have short-lived excited states. Now an iron complex has been developed that has a long-lived excited state, which can lead to photo-induced electron injection into nanoporous TiO2 with a yield of 92%.

    • Tobias C. B. Harlang
    • , Yizhu Liu
    •  & Kenneth Wärnmark

  • Article |

    Charge separation in oxygenic photosynthesis occurs with high quantum efficiency and is yet to be fully understood. Using two-dimensional electronic spectroscopy, coherent dynamics have now been observed in the photosystem II reaction centre, where charge separation occurs. Supporting simulations suggest that the coherences have mixed electronic–vibrational (vibronic) nature, and may enhance the rate of charge separation. Leaf image: © Michael Wesemann/Alamy.

    • Franklin D. Fuller
    • , Jie Pan
    •  & Jennifer P. Ogilvie

  • Article |

    Solar thermal fuels have recently attracted an increasing amount of attention as a potential method for solar energy capture, conversion, storage and utilization. Azobenzene-functionalized single-walled carbon nanotubes demonstrate the proof-of-principle for increasing kinetic stability and energy densities by templating photoswitchable molecules on nanostructures to achieve highly (con)strained configurations.

    • Timothy J. Kucharski
    • , Nicola Ferralis
    •  & Jeffrey C. Grossman

  • News & Views |

    Pigment assemblies with high-efficiency electronic energy transfer have recently been observed to show unusual and persistent coherence, but its origin is not fully understood. Now, a combination of 2D electronic spectroscopy and theoretical modelling has allowed the excitonic coherence signal of a strongly coupled homodimer to be isolated.

    • Vivek Tiwari
    • , William K. Peters
    •  & David M. Jonas

  • Article |

    Light-driven proton pumps are used in biology to create a proton gradient that can be subsequently converted into chemical energy. Here, an artificial light-harvesting system based on a membrane doped with a spiropyran is described. Irradiation with UV light generates a proton flux across the membrane and results in the generation of an electrical current.

    • Xiaojiang Xie
    • , Gastón A. Crespo
    •  & Eric Bakker

  • Article |

    The observation of long-lived coherent oscillations in the nonlinear spectra of photosynthetic proteins has raised significant discussion on the role of quantum effects in biology. Using a model system, the signatures of inter-exciton coherence have been isolated, which has allowed the influence of vibronic coupling to be studied in unprecedented detail.

    • Alexei Halpin
    • , Philip J. M. Johnson
    •  & R. J. Dwayne Miller

  • Article |

    The collective excited states (excitons) in supramolecular light-harvesting systems depend intimately on their structure and it is crucial to understand how these states interact. Now it is shown that simple redox chemistry can be used to address this fundamental question by simplifying the complex excitonic interactions in such multichromophoric systems.

    • D. M. Eisele
    • , C. W. Cone
    •  & D. A. Vanden Bout

  • Article |

    Quantum beating has been observed in photosynthetic systems, suggesting that energy-transfer processes in natural light harvesting could involve quantum effects. Now, extensive beating is found in the light-harvesting protein of a cryptophyte alga, and shown to be electronic. The implications of these observations on the free-energy surfaces and exciton delocalization were investigated.

    • Cathy Y. Wong
    • , Richard M. Alvey
    •  & Gregory D. Scholes

  • Review Article |

    Photosynthesis starts when light is absorbed and the associated excitation energy is directed to reaction centres by antenna complexes. The principles learned from studying these complexes are described in this Review, and provide the framework from which the authors suggest how to elucidate strategies for designing light-harvesting systems that route the flow of energy in sophisticated ways.

    • Gregory D. Scholes
    • , Graham R. Fleming
    •  & Rienk van Grondelle

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