Physical chemistry articles within Nature Chemistry

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  • In Your Element |

    Rajeev K. Dubey and Frank Würthner discuss the colourful character of perylene bisimides and the impact of aggregation on their functional properties.

    • Rajeev K. Dubey
    •  & Frank Würthner

  • Article |

    Trihydrogen cations are abundant in interstellar space and play a vital role in both star and organic molecule formation. Now it has been shown that D3+ cations can be directly produced through photoionization of molecular D2–D2 dimers.

    • Yonghao Mi
    • , Enliang Wang
    •  & André Staudte

  • Article |

    H3+ and D3+ serve as initiators of many chemical reactions in interstellar clouds. Now the ultrafast formation dynamics of D3+ from a light-driven bimolecular reaction starting from D2–D2 dimers have been measured. It has also been shown that the emission direction of D3+ can be controlled by driving the reaction with a more complex two-colour laser pulse.

    • Lianrong Zhou
    • , Hongcheng Ni
    •  & Jian Wu

  • Perspective |

    Bioresponsive hyperpolarized probes contain magnetic resonance signals that can be many orders of magnitude larger than those of common, thermally polarized probes. This Perspective discusses how bioresponsive hyperpolarized probes can be directly linked to biological events to give functional information, enabling the mapping of physiological processes and diseases in real time using magnetic resonance.

    • Goran Angelovski
    • , Ben J. Tickner
    •  & Gaoji Wang

  • Article
    | Open Access

    Protein solutions can undergo liquid–liquid phase separation, by condensing into a dense phase that often resembles liquid droplets, which coexist with a dilute phase. Now it is shown that hydrophobic interactions, specifically at interfaces, can trigger a liquid–solid phase separation of a protein solution.

    • Daria Maltseva
    • , Sayantan Chatterjee
    •  & Mischa Bonn

  • Article
    | Open Access

    Electronic spin influences chemistry profoundly, but its role in surface chemistry is poorly established. Now the spin-dependent reaction probabilities of oxygen atoms with a graphite surface have been studied. Molecular dynamics simulations help elucidate the mechanism for spin-flipping, which is observed to occur with low probability in surface scattering experiments.

    • Zibo Zhao
    • , Yingqi Wang
    •  & G. Barratt Park

  • Article |

    In situ chirality identification for single-molecule systems is not a straightforward task. Now, real-time chirality identification during a Michael addition reaction has been realized by continuous measurements of spin-polarized currents through a single-molecule junction, providing a promising method for studying symmetry-breaking reactions.

    • Chen Yang
    • , Yanwei Li
    •  & Xuefeng Guo

  • Article |

    Indole-5,6-quinone (IQ) is a long-sought intermediate and structural subunit of eumelanin pigments whose instability has precluded isolation and characterization. It has now been shown that a sterically shielded derivative of IQ exhibits hallmark eumelanin properties, including near-infrared absorption, ultrafast nonradiative decay and a persistent semiquinone radical formed by comproportionation.

    • Xueqing Wang
    • , Lilia Kinziabulatova
    •  & Jean-Philip Lumb

  • 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 |

    The advantages and disadvantages of building a nanosystem using one, two or more molecular components are poorly understood. Now, using structural and catalytic DNA-based nanosystems and theoretical simulations, it has been shown that the assembly of trimeric nanosystems displays much higher levels of programmability and functionality than the monomeric or dimeric counterparts.

    • D. Lauzon
    •  & A. Vallée-Bélisle

  • News & Views |

    An organic quantum magnet has been prepared in short chains of porphyrin derivatives through a combination of on-surface synthesis and atom manipulation using the tip of a scanning probe microscope.

    • P. Jelínek

  • Article |

    The transition state, a transient species where bond transformation occurs, fundamentally controls reaction dynamics. This important species can be probed through the photodetachment of an anionic precursor, as has now been shown in the F + NH3 reaction. A combination of theory and experiment reveals resonances that span the transition state.

    • Mark C. Babin
    • , Martin DeWitt
    •  & Daniel M. Neumark

  • Article
    | Open Access

    Inelastic hydrogen atom scattering from surfaces provides a good benchmark for the validity of the Born–Oppenheimer approximation in surface chemistry. Now it has been shown that hydrogen atoms colliding with a semiconductor surface can efficiently excite electrons above the surface bandgap, representing a clear example of the failure of the approximation.

    • Kerstin Krüger
    • , Yingqi Wang
    •  & Oliver Bünermann

  • Article
    | Open Access

    Iodic acid (HIO3) forms aerosols very efficiently, but its gas-phase formation mechanism is not well understood. Atmospheric simulation chamber experiments, quantum chemical calculations and kinetic modelling have now revealed that HIO3 forms as an early iodine oxidation product from hypoiodite. The mechanism explains field measurements and suggests a catalytic role for iodine in particle formation.

    • Henning Finkenzeller
    • , Siddharth Iyer
    •  & Rainer Volkamer

  • News & Views |

    The study of rare isotopes, including many in the f-block, is a key step to advancing our fundamental understanding of these elements, but their scarcity poses challenges. Now, minute amounts of such materials have been isolated and characterized through complexation with polyoxometalate clusters.

    • Kristina O. Kvashnina

  • Article |

    Quantum nanomagnets, which display collective quantum behaviours, serve as important components in modern quantum technologies, but their fabrication has remained challenging. Quantum nanomagnets have now been constructed spin by spin in metal-free porphyrin chains, using on-surface synthesis and hydrogen manipulation using a scanning tunnelling microscope, and their collective quantum behaviours have been clearly resolved.

    • Yan Zhao
    • , Kaiyue Jiang
    •  & Shiyong Wang

  • Article |

    Intersystem crossing in reaction entrance channels usually arises from ‘heavy-atom’ effects. Now molecular-beam experiments show that even without heavy atoms, the O(3P) + pyridine reaction leads to spin-forbidden pyrrole + CO products. Theoretical calculations reveal efficient intersystem crossing before the entrance barrier for O-atom addition to the N-atom lone pair, which dominates reactivity at low to moderate temperatures.

    • Pedro Recio
    • , Silvia Alessandrini
    •  & Vincenzo Barone

  • Article
    | Open Access

    Proteins rich in phenylalanine-glycine (FG) repeats can phase separate through FG–FG interactions. The molecular interactions of an important FG-repeat protein, nucleoporin 98, have now been studied in liquid-like transient and amyloid-like cohesive states. These interactions underlie the behaviour of FG-repeat proteins and their function in physiological and pathological cell activities.

    • Alain Ibáñez de Opakua
    • , James A. Geraets
    •  & Markus Zweckstetter

  • 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
    | Open Access

    In some cases, hydrogen adsorption close to its boiling temperature shows unusually high monolayer capacities, but the microscopic nature of this adsorbate phase is not well understood. Now, H2 adsorbed on a well-ordered mesoporous silica surface has been shown to form a 2D monolayer with very short H2···H2 intermolecular distances and a density more than twice that of bulk-solid H2.

    • Rafael Balderas-Xicohténcatl
    • , Hung-Hsuan Lin
    •  & Michael Hirscher

  • Article |

    The influence that liquid environments have on the ultrafast excited-state dynamics of molecules is poorly understood. Using time-resolved photoelectron spectroscopy, the dynamics of the photoisomerization of stilbene in the gas and liquid phases have now been shown to be qualitatively similar—including the observation of vibrational coherences—but the timescales are significantly longer in the liquid phase.

    • Chuncheng Wang
    • , Max D. J. Waters
    •  & Hans Jakob Wörner

  • Article |

    Intermolecular Coulombic decay (ICD) is a process whereby a photoexcited molecule relaxes while ionizing a neighbouring molecule. ICD is efficient when intermolecular interactions are active and consequently it is usually observed in weakly bound systems. Now, an efficient ICD is shown to occur even between unbound pyridine molecules excited at ambient-light intensities.

    • Saroj Barik
    • , Saurav Dutta
    •  & G. Aravind

  • News & Views |

    How electric fields generated by enzyme active sites push and pull on substrates is important to their chemistry, but measuring them is difficult. Now, the electric field within an active site has been measured along two directions using a vibrational probe, revealing that the field effect in enzymes is different compared with that in bulk solvents.

    • Anuj Pennathur
    •  & Jahan Dawlaty

  • Article |

    Laser cooling of molecules with more than six atoms is challenging, mainly due to vibrational loss to dark states. Now, taking a step towards the development of a ‘quantum functional group’, it has been shown that such vibrational loss in molecules like phenol can be greatly restricted by functionalizing with a Ca(I)–O unit, which may serve as a generic qubit moiety.

    • Guo-Zhu Zhu
    • , Debayan Mitra
    •  & Eric R. Hudson

  • Article
    | Open Access

    The design of photoactivatable fluorophores—which are required for some super-resolution fluorescence microscopy methods—usually relies on light-sensitive protecting groups imparting lipophilicity and generating reactive by-products. Now, it has been shown that by exploiting a unique intramolecular photocyclization, bright and highly photostable fluorophores can be rapidly generated in situ from appropriately substituted 1-alkenyl-3,6-diaminoxanthone precursors.

    • Richard Lincoln
    • , Mariano L. Bossi
    •  & Stefan W. Hell

  • Article |

    A genetically encoded phototrigger based on a xanthone amino acid can expand the scope of time-resolved serial femtosecond crystallography beyond naturally photoactive proteins. This approach has been used to uncover metastable reaction intermediates that occur prior to C–H bond activation in a human liver fatty-acid-binding protein mutant.

    • Xiaohong Liu
    • , Pengcheng Liu
    •  & Jiangyun Wang

  • News & Views |

    Photoredox catalysts offer a promising approach to performing reactions with high energetic requirements, however, the influence of solvent and counter ions is not fully understood. Now, a microwave-based technique is shown to give direct insight into their effects on charge reorganization during catalysis.

    • Ferdinand C. Grozema

  • News & Views |

    Over the past 25 years, the photo-induced spin-crossover behaviour of Fe(II) complexes has puzzled scientists. Now, a symmetry-breaking twisting mode has been observed during the relaxation of such a complex. Controlling its configuration using enantiopure counterions has also been shown to slow down the relaxation.

    • J. Olof Johansson

  • Article
    | Open Access

    Ions in salt solutions perturb the hydrogen bonding between the surrounding water molecules, altering the properties of water, but how ion polarity affects this is not fully understood. By monitoring the dissipation of terahertz energy in salt solutions, it has now been shown that intermolecular rotational-to-translational energy transfer is enhanced by highly charged cations and reduced by highly charged anions.

    • Vasileios Balos
    • , Naveen Kumar Kaliannan
    •  & Mohsen Sajadi

  • In Your Element |

    The tris(2,2′-bipyridine)ruthenium(II) cation, or ‘rubipy’ to its friends, has had a significant influence on our understanding of the photophysics of transition metal complexes, and has also helped revolutionize organic photochemistry, explains Daniela M. Arias-Rotondo.

    • Daniela M. Arias-Rotondo

  • Comment |

    In 1931, Erich Hückel published a landmark paper — the seed of the now famous 4n + 2 rule for aromaticity in annulenes that bears his name. Electron counting has since been extended to other classes of compounds, resulting in a multitude of rules aiming to capture the concept of aromaticity and its impact in chemistry.

    • Miquel Solà

  • Article |

    Despite much research, the high-spin-state relaxation mechanism of Fe(II) spin-crossover complexes is unresolved. Using ultrafast circular dichroism spectroscopy it has now been revealed that the spin relaxation is driven by a torsional twisting mode, which breaks the chiral symmetry of a prototypical Fe(II) compound. Stereocontrolling the configuration of the complex can thus be used to slow down the spin relaxation.

    • Malte Oppermann
    • , Francesco Zinna
    •  & Majed Chergui

  • Article |

    HCN and its isomer HNC are both observed in the interstellar medium and inelastic collisions with helium and other species strongly influence their derived abundances. Now it has been shown experimentally and theoretically that HNC is much more strongly excited than HCN in collisions with helium at the low temperatures of interstellar space.

    • Brian M. Hays
    • , Divita Gupta
    •  & Ian R. Sims

  • Article |

    Preorganized electric fields may be essential for the extraordinary catalytic power of enzymes. Now, it has been demonstrated how electric field strengths can be monitored along two directions using a vibrational Stark probe, enabling the observation of distinct electric field orientations in an enzyme active site compared with those in simple solvents.

    • Chu Zheng
    • , Yuezhi Mao
    •  & Steven G. Boxer

  • Article |

    The collision dynamics between a pair of aligned molecules in the presence of a scattering resonance provide the most sensitive probe of the long-range anisotropic forces important to chemistry. By simultaneously controlling the collision temperature and geometry between a pair of aligned D2 molecules, we unravel the anisotropic dynamics of a cold scattering process.

    • Haowen Zhou
    • , William E. Perreault
    •  & Richard N. Zare

  • 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 |

    Ion pairing is ubiquitous in low-dielectric-constant solvents, but whether it influences the reactivity of common cationic photoredox catalysts has been unclear. However, it has now been shown that ion pairing is responsible for a 4-fold modulation in reactivity in a prototypical Ir(III) complex and is explained by excited-state ion-pair reorganization.

    • J. D. Earley
    • , A. Zieleniewska
    •  & G. Rumbles

  • News & Views |

    Electron spin relaxation, important in quantum information science, can be slowed down at clock transitions — which are insensitive to magnetic noise. It has now been shown that such transitions can be tuned, to high frequency, in rare-earth coordination complexes through control of s- and d-orbital mixing.

    • Eric J. L. McInnes

  • Article |

    Influencing the products of a reaction through controlling the state of the reactants is a notable goal for chemists. It has now been shown that the reactivity of a pair of Fermi-coupled vibrational states of CH3D(v1-I and v1-II) with a chlorine atom depends not only on the constituent basis modes, but also on the relative phase of the two modes in their wave-functions.

    • Huilin Pan
    •  & Kopin Liu

  • Article |

    Molecular energy transfer is thought to follow a simple rule of thumb: high energy transfer requires hard collisions that result in backscattering. However, now it has been observed that an unexpected forward scattering occurs in NO–CO and NO–HD collisions even for high energy transfer. This is attributed to ‘hard-collision glory scattering’, a mechanism that appears to be ubiquitous in molecule–molecule collisions.

    • Matthieu Besemer
    • , Guoqiang Tang
    •  & Tijs Karman

  • Article |

    Information is physical, but the flow between information, energy and mechanics in chemical systems remains largely unexplored. Now, an autonomous molecular motor has been analysed with information thermodynamics, which relates information to other thermodynamic parameters. This treatment provides a general thermodynamic understanding of molecular motors, with practical implications for machine design.

    • Shuntaro Amano
    • , Massimiliano Esposito
    •  & Benjamin M. W. Roberts

  • Article |

    The s-orbital mixing into the spin-bearing d orbital associated with a molecular Lu(II) complex is shown to both reduce spin–orbit coupling and increase electron–nuclear hyperfine interactions, which substantially improves electron spin coherence. Combined with the potential to tune interactions through coordination chemistry, it makes this system attractive for quantum information applications.

    • Krishnendu Kundu
    • , Jessica R. K. White
    •  & Stephen Hill

  • Article |

    Low-energy NO–He collisions have been studied and scattering resonances observed. By rotationally exciting NO before the collision, a controlled amount of angular momentum was added and its release in de-excitation collisions was monitored—additional quantum waves were imprinted in the angular distributions of the scattering products.

    • Tim de Jongh
    • , Quan Shuai
    •  & Sebastiaan Y. T. van de Meerakker

  • Article |

    Controlling the crystallographic registry of layered materials through interlayer twist angles has introduced a distinctive degree of freedom for tuning their electronic behaviour. Now, the interfacial electrochemical kinetics of solution-phase redox complexes at twisted bilayer graphene electrodes have been modulated by the angle-dependent tuning of moiré-derived flat bands.

    • Yun Yu
    • , Kaidi Zhang
    •  & D. Kwabena Bediako

  • Article |

    Molecular catalysts for artificial photosynthesis can break down during operation and stop working, whereas biological photosynthesis uses an enzymatic repair strategy to maintain function. Now, the degradation pathway of a hydrogen-evolving RuPt photocatalyst has been identified, enabling the development of an active repair strategy involving the use of 1O2 to reoxidize the deactivated bridging ligand.

    • Michael G. Pfeffer
    • , Carolin Müller
    •  & Sven Rau

  • News & Views |

    Despite the disordered and dynamic environment in which it occurs, photosynthetic light harvesting is highly efficient. Now, measurements of energy transfer in single photosynthetic antennae show how these structures deal with protein fluctuations, robustly transferring the energy before it is lost.

    • Pavel Malý

  • Article
    | Open Access

    Despite extensive investigations of mixed-valence complexes, molecules with intermediate spin states have remained elusive. Now, selenium- and tellurium-bridged mixed-valent iron dimers have been prepared in which a balance of Heisenberg exchange and double-exchange coupling of the unpaired electron, combined with moderate vibronic contributions, stabilizes S = 3/2 ground spin states.

    • Justin T. Henthorn
    • , George E. Cutsail III
    •  & Serena DeBeer

  • Article |

    In photosynthesis, photoenergy transfers through chromophore-containing proteins, which exhibit thermal fluctuations that change the positions of the chromophores. Now the ultrafast dynamics in allophycocyanin—a cyanobacterial light-harvesting protein—have been measured using single-molecule pump–probe spectroscopy. The data show that energy transfer precedes protein-induced photophysical heterogeneity, ensuring that light harvesting is robust to the heterogeneity.

    • Raymundo Moya
    • , Audrey C. Norris
    •  & Gabriela S. Schlau-Cohen

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