TY - JOUR A1 - Reifarth, Martin A1 - Bekir, Marek A1 - Bapolisi, Alain M. A1 - Titov, Evgenii A1 - Nusshardt, Fabian A1 - Nowaczyk, Julius A1 - Grigoriev, Dmitry A1 - Sharma, Anjali A1 - Saalfrank, Peter A1 - Santer, Svetlana A1 - Hartlieb, Matthias A1 - Böker, Alexander T1 - A dual pH- and light-responsive spiropyrane-based surfactant BT - investigations on Its switching behavior and remote control over emulsion stability JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - A cationic surfactant containing a spiropyrane unit is prepared exhibiting a dual-responsive adjustability of its surface-active characteristics. The switching mechanism of the system relies on the reversible conversion of the non-ionic spiropyrane (SP) to a zwitterionic merocyanine (MC) and can be controlled by adjusting the pH value and via light, resulting in a pH-dependent photoactivity: While the compound possesses a pronounced difference in surface activity between both forms under acidic conditions, this behavior is suppressed at a neutral pH level. The underlying switching processes are investigated in detail, and a thermodynamic explanation based on a combination of theoretical and experimental results is provided. This complex stimuli-responsive behavior enables remote-control of colloidal systems. To demonstrate its applicability, the surfactant is utilized for the pH-dependent manipulation of oil-in-water emulsions. KW - Dual-Responsiveness KW - Manipulation of Emulsion Stability KW - Spiropyrane KW - Surfactant KW - Switchable Surfactants KW - pH-Dependent Photoresponsivity Y1 - 2022 U6 - https://doi.org/10.1002/anie.202114687 SN - 1433-7851 SN - 1521-3773 VL - 61 IS - 21 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Fischer, Eric Wolfgang A1 - Anders, Janet A1 - Saalfrank, Peter T1 - Cavity-altered thermal isomerization rates and dynamical resonant localization in vibro-polaritonic chemistry JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - It has been experimentally demonstrated that reaction rates for molecules embedded in microfluidic optical cavities are altered when compared to rates observed under "ordinary" reaction conditions. However, precise mechanisms of how strong coupling of an optical cavity mode to molecular vibrations affects the reactivity and how resonance behavior emerges are still under dispute. In the present work, we approach these mechanistic issues from the perspective of a thermal model reaction, the inversion of ammonia along the umbrella mode, in the presence of a single-cavity mode of varying frequency and coupling strength. A topological analysis of the related cavity Born-Oppenheimer potential energy surface in combination with quantum mechanical and transition state theory rate calculations reveals two quantum effects, leading to decelerated reaction rates in qualitative agreement with experiments: the stiffening of quantized modes perpendicular to the reaction path at the transition state, which reduces the number of thermally accessible reaction channels, and the broadening of the barrier region, which attenuates tunneling. We find these two effects to be very robust in a fluctuating environment, causing statistical variations of potential parameters, such as the barrier height. Furthermore, by solving the time-dependent Schrodinger equation in the vibrational strong coupling regime, we identify a resonance behavior, in qualitative agreement with experimental and earlier theoretical work. The latter manifests as reduced reaction probability when the cavity frequency omega(c) is tuned resonant to a molecular reactant frequency. We find this effect to be based on the dynamical localization of the vibro-polaritonic wavepacket in the reactant well. Y1 - 2022 U6 - https://doi.org/10.1063/5.0076434 SN - 0021-9606 SN - 1089-7690 VL - 156 IS - 15 PB - American Institute of Physics CY - Melville, NY ER - TY - JOUR A1 - Choudhury, Arnab A1 - DeVine, Jessalyn A. A. A1 - Sinha, Shreya A1 - Lau, Jascha Alexander A1 - Kandratsenka, Alexander A1 - Schwarzer, Dirk A1 - Saalfrank, Peter A1 - Wodtke, Alec Michael T1 - Condensed-phase isomerization through tunnelling gateways JF - Nature : the international weekly journal of science N2 - Quantum mechanical tunnelling describes transmission of matter waves through a barrier with height larger than the energy of the wave(1). Tunnelling becomes important when the de Broglie wavelength of the particle exceeds the barrier thickness; because wavelength increases with decreasing mass, lighter particles tunnel more efficiently than heavier ones. However, there exist examples in condensed-phase chemistry where increasing mass leads to increased tunnelling rates(2). In contrast to the textbook approach, which considers transitions between continuum states, condensed-phase reactions involve transitions between bound states of reactants and products. Here this conceptual distinction is highlighted by experimental measurements of isotopologue-specific tunnelling rates for CO rotational isomerization at an NaCl surface(3,4), showing nonmonotonic mass dependence. A quantum rate theory of isomerization is developed wherein transitions between sub-barrier reactant and product states occur through interaction with the environment. Tunnelling is fastest for specific pairs of states (gateways), the quantum mechanical details of which lead to enhanced cross-barrier coupling; the energies of these gateways arise nonsystematically, giving an erratic mass dependence. Gateways also accelerate ground-state isomerization, acting as leaky holes through the reaction barrier. This simple model provides a way to account for tunnelling in condensed-phase chemistry, and indicates that heavy-atom tunnelling may be more important than typically assumed. Y1 - 2022 U6 - https://doi.org/10.1038/s41586-022-05451-0 SN - 0028-0836 SN - 1476-4687 VL - 612 IS - 7941 SP - 691 EP - 695 PB - Macmillan Publishers Limited, part of Springer Nature CY - London ER - TY - JOUR A1 - Yang, Jin A1 - Ghosh, Samrat A1 - Roeser, Jérôme A1 - Acharjya, Amitava A1 - Penschke, Christopher A1 - Tsutsui, Yusuke A1 - Rabeah, Jabor A1 - Wang, Tianyi A1 - Tameu, Simon Yves Djoko A1 - Ye, Meng-Yang A1 - Grüneberg, Julia A1 - Li, Shuang A1 - Li, Changxia A1 - Schomaecker, Reinhard A1 - Van de Krol, Roel A1 - Seki, Shu A1 - Saalfrank, Peter A1 - Thomas, Arne T1 - Constitutional isomerism of the linkages in donor–acceptor covalent organic frameworks and its impact on photocatalysis JF - Nature Communications N2 - When new covalent organic frameworks (COFs) are designed, the main efforts are typically focused on selecting specific building blocks with certain geometries and properties to control the structure and function of the final COFs. The nature of the linkage (imine, boroxine, vinyl, etc.) between these building blocks naturally also defines their properties. However, besides the linkage type, the orientation, i.e., the constitutional isomerism of these linkages, has rarely been considered so far as an essential aspect. In this work, three pairs of constitutionally isomeric imine-linked donor-acceptor (D-A) COFs are synthesized, which are different in the orientation of the imine bonds (D-C=N-A (DCNA) and D-N=C-A (DNCA)). The constitutional isomers show substantial differences in their photophysical properties and consequently in their photocatalytic performance. Indeed, all DCNA COFs show enhanced photocatalytic H2 evolution performance than the corresponding DNCA COFs. Besides the imine COFs shown here, it can be concluded that the proposed concept of constitutional isomerism of linkages in COFs is quite universal and should be considered when designing and tuning the properties of COFs. Y1 - 2022 U6 - https://doi.org/10.1038/s41467-022-33875-9 SN - 2041-1723 VL - 13 IS - 1 PB - Nature Publishing Group UK CY - [London] ER - TY - JOUR A1 - Fischer, Eric Wolfgang A1 - Werther, Michael A1 - Bouakline, Foudhil A1 - Grossmann, Frank A1 - Saalfrank, Peter T1 - Non-Markovian vibrational relaxation dynamics at surfaces JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Vibrational dynamics of adsorbates near surfaces plays both an important role for applied surface science and as a model lab for studying fundamental problems of open quantum systems. We employ a previously developed model for the relaxation of a D-Si-Si bending mode at a D:Si(100)-(2 x 1) surface, induced by a "bath " of more than 2000 phonon modes [Lorenz and P. Saalfrank, Chem. Phys. 482, 69 (2017)], to extend previous work along various directions. First, we use a Hierarchical Effective Mode (HEM) model [Fischer et al., J. Chem. Phys. 153, 064704 (2020)] to study relaxation of higher excited vibrational states than hitherto done by solving a high-dimensional system-bath time-dependent Schrodinger equation (TDSE). In the HEM approach, (many) real bath modes are replaced by (much less) effective bath modes. Accordingly, we are able to examine scaling laws for vibrational relaxation lifetimes for a realistic surface science problem. Second, we compare the performance of the multilayer multiconfigurational time-dependent Hartree (ML-MCTDH) approach with that of the recently developed coherent-state-based multi-Davydov-D2 Ansatz [Zhou et al., J. Chem. Phys. 143, 014113 (2015)]. Both approaches work well, with some computational advantages for the latter in the presented context. Third, we apply open-system density matrix theory in comparison with basically "exact " solutions of the multi-mode TDSEs. Specifically, we use an open-system Liouville-von Neumann (LvN) equation treating vibration-phonon coupling as Markovian dissipation in Lindblad form to quantify effects beyond the Born-Markov approximation. Published under an exclusive license by AIP Publishing. KW - phonons KW - Vibrational states KW - Chemical dynamics KW - Adsorption KW - Surface science KW - Open quantum systems KW - Density-matrix KW - Coherent states KW - Markov processes Y1 - 2022 U6 - https://doi.org/10.1063/5.0092836 SN - 0021-9606 SN - 1089-7690 SN - 1520-9032 VL - 156 IS - 21 PB - AIP Publishing CY - Melville ER - TY - JOUR A1 - Mullan, Thomas A1 - Maschio, Lorenzo A1 - Saalfrank, Peter A1 - Usvyat, Denis T1 - Reaction barriers on non-conducting surfaces beyond periodic local MP2 BT - Diffusion of hydrogen on alpha-Al2O3 (0001) as a test case JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - The quest for "chemical accuracy" is becoming more and more demanded in the field of structure and kinetics of molecules at solid surfaces. In this paper, as an example, we focus on the barrier for hydrogen diffusion on a alpha-Al2O3 (0001) surface, aiming for a couple cluster singles, doubles, and perturbative triples [CCSD(T)]-level benchmark. We employ the density functional theory (DFT) optimized minimum and transition state structures reported by Heiden, Usvyat, and Saalfrank [J. Phys. Chem. C 123, 6675 (2019)]. The barrier is first evaluated at the periodic Hartree-Fock and local Moller-Plesset second-order perturbation (MP2) level of theory. The possible sources of errors are then analyzed, which includes basis set incompleteness error, frozen core, density fitting, local approximation errors, as well as the MP2 method error. Using periodic and embedded fragment models, corrections to these errors are evaluated. In particular, two corrections are found to be non-negligible (both from the chemical accuracy perspective and at the scale of the barrier value of 0.72 eV): the correction to the frozen core-approximation of 0.06 eV and the CCSD(T) correction of 0.07 eV. Our correlated wave function results are compared to barriers obtained from DFT. Among the tested DFT functionals, the best performing for this barrier is B3LYP-D3. Y1 - 2022 U6 - https://doi.org/10.1063/5.0082805 SN - 0021-9606 SN - 1089-7690 VL - 156 IS - 7 PB - AIP Publishing CY - Melville ER - TY - JOUR A1 - Yue, Yanhua A1 - Melani, Giacomo A1 - Kirsch, Harald A1 - Paarmann, Alexander A1 - Saalfrank, Peter A1 - Campen, Richard Kramer A1 - Tong, Yujin T1 - Structure and Reactivity of a-Al2O3(0001) Surfaces: How Do Al-I and Gibbsite-like Terminations Interconvert? JF - The journal of physical chemistry / publ. weekly by the American Chemical Society. C, Energy, materials, and catalysis N2 - The alpha-Al2O3(0001) surface has been extensively studied because of its significance in both fundamental research and application. Prior work suggests that in ultra-high-vacuum (UHV), in the absence of water, the so-called Al-I termination is thermodynamically favored, while in ambient, in contact with liquid water, a Gibbsite-like layer is created. While the view of the alpha- Al2O3(0001)/H2O(l) interface appears relatively clear in theory, experimental characterization of this system has resulted in estimates of surface acidity, i.e., isoelectric points, that differ by 4 pH units and surface structure that in some reports has non-hydrogen-bonded surface aluminol (Al-OH) groups and in others does not. In this study, we employed vibrational sum frequency spectroscopy (VSFS) and density functional theory (DFT) simulation to study the surface phonon modes of the differently terminated alpha-Al2O3(0001) surfaces in both UHV and ambient. We find that, on either water dosing of the Al-I in UHV or heat-induced dehydroxylation of the Gibbsite-like in ambient, the surfaces do not interconvert. This observation offers a new explanation for disagreements in prior work on the alpha-Al2O3(0001)/liquid water interface -different preparation methods may create surfaces that do not interconvert-and shows that the surface phonon spectral response offers a novel probe of interfacial hydrogen bonding structure. Y1 - 2022 U6 - https://doi.org/10.1021/acs.jpcc.2c03743 SN - 1932-7447 SN - 1932-7455 VL - 126 IS - 31 SP - 13467 EP - 13476 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schürmann, Robin A1 - Titov, Evgenii A1 - Ebel, Kenny A1 - Kogikoski Junior, Sergio A1 - Mostafa, Amr A1 - Saalfrank, Peter A1 - Milosavljević, Aleksandar R. A1 - Bald, Ilko T1 - The electronic structure of the metal-organic interface of isolated ligand coated gold nanoparticles JF - Nanoscale Advances N2 - Light induced electron transfer reactions of molecules on the surface of noble metal nanoparticles (NPs) depend significantly on the electronic properties of the metal-organic interface. Hybridized metal-molecule states and dipoles at the interface alter the work function and facilitate or hinder electron transfer between the NPs and ligand. X-ray photoelectron spectroscopy (XPS) measurements of isolated AuNPs coated with thiolated ligands in a vacuum have been performed as a function of photon energy, and the depth dependent information of the metal-organic interface has been obtained. The role of surface dipoles in the XPS measurements of isolated ligand coated NPs is discussed and the binding energy of the Au 4f states is shifted by around 0.8 eV in the outer atomic layers of 4-nitrothiophenol coated AuNPs, facilitating electron transport towards the molecules. Moreover, the influence of the interface dipole depends significantly on the adsorbed ligand molecules. The present study paves the way towards the engineering of the electronic properties of the nanoparticle surface, which is of utmost importance for the application of plasmonic nanoparticles in the fields of heterogeneous catalysis and solar energy conversion. Y1 - 2022 U6 - https://doi.org/10.1039/d1na00737h SN - 2516-0230 VL - 4 IS - 6 SP - 1599 EP - 1607 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kuntze, Kim A1 - Viljakka, Jani A1 - Titov, Evgenii A1 - Ahmed, Zafar A1 - Kalenius, Elina A1 - Saalfrank, Peter A1 - Priimagi, Arri T1 - Towards low-energy-light-driven bistable photoswitches BT - ortho-fluoroaminoazobenzenes JF - Photochemical & photobiological sciences / European Society for Photobiology N2 - Thermally stable photoswitches that are driven with low-energy light are rare, yet crucial for extending the applicability of photoresponsive molecules and materials towards, e.g., living systems. Combined ortho-fluorination and -amination couples high visible light absorptivity of o-aminoazobenzenes with the extraordinary bistability of o-fluoroazobenzenes. Herein, we report a library of easily accessible o-aminofluoroazobenzenes and establish structure-property relationships regarding spectral qualities, visible light isomerization efficiency and thermal stability of the cis-isomer with respect to the degree of o-substitution and choice of amino substituent. We rationalize the experimental results with quantum chemical calculations, revealing the nature of low-lying excited states and providing insight into thermal isomerization. The synthesized azobenzenes absorb at up to 600 nm and their thermal cis-lifetimes range from milliseconds to months. The most unique example can be driven from trans to cis with any wavelength from UV up to 595 nm, while still exhibiting a thermal cis-lifetime of 81 days.
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. Y1 - 2022 U6 - https://doi.org/10.1007/s43630-021-00145-4 SN - 1474-905X SN - 1474-9092 VL - 21 IS - 2 SP - 159 EP - 173 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Penschke, Christopher A1 - Edler von Zander, Robert A1 - Beqiraj, Alkit A1 - Zehle, Anna A1 - Jahn, Nicolas A1 - Neumann, Rainer A1 - Saalfrank, Peter T1 - Water on porous, nitrogen-containing layered carbon materials BT - the performance of computational model chemistries JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies / RSC, Royal Society of Chemistry N2 - Porous, layered materials containing sp(2)-hybridized carbon and nitrogen atoms, offer through their tunable properties, a versatile route towards tailormade catalysts for electrochemistry and photochemistry. A key molecule interacting with these quasi two-dimensional materials (2DM) is water, and a photo(electro)chemical key reaction catalyzed by them, is water splitting into H-2 and O-2, with the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) as half reactions. The complexity of some C/N-based 2DM in contact with water raises special needs for their theoretical modelling, which in turn is needed for rational design of C/N-based catalysts. In this work, three classes of C/N-containing porous 2DM with varying pore sizes and C/N ratios, namely graphitic carbon nitride (g-C3N4), C2N, and poly(heptazine imides) (PHI), are studied with various computational methods. We elucidate the performance of different models and model chemistries (the combination of electronic structure method and basis set) for water and water fragment adsorption in the low-coverage regime. Further, properties related to the photo(electro)chemical activity like electrochemical overpotentials, band gaps, and optical excitation energies are in our focus. Specifically, periodic models will be tested vs. cluster models, and density functional theory (DFT) vs. wavefunction theory (WFT). This work serves as a basis for a systematic study of trends for the photo(electro)chemical activity of C/N-containing layered materials as a function of water content, pore size and density. Y1 - 2022 U6 - https://doi.org/10.1039/d2cp00657j SN - 1463-9076 SN - 1463-9084 VL - 24 IS - 24 SP - 14709 EP - 14726 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Tetenoire, Auguste A1 - Ehlert, Christopher A1 - Juaristi, Joseba Iñaki A1 - Saalfrank, Peter A1 - Alducin, Maite T1 - Why ultrafast photoinduced CO desorption dominates over oxidation on Ru(0001) JF - The journal of physical chemistry letters N2 - CO oxidation on Ru(0001) is a long-standing example of a reaction that, being thermally forbidden in ultrahigh vacuum, can be activated by femtosecond laser pulses. In spite of its relevance, the precise dynamics of the photoinduced oxidation process as well as the reasons behind the dominant role of the competing CO photodesorption remain unclear. Here we use ab initio molecular dynamics with electronic friction that account for the highly excited and nonequilibrated system created by the laser to investigate both reactions. Our simulations successfully reproduce the main experimental findings: the existence of photoinduced oxidation and desorption, the large desorption to oxidation branching ratio, and the changes in the O K-edge X-ray absorption spectra attributed to the initial stage of the oxidation process. Now, we are able to monitor in detail the ultrafast CO desorption and CO oxidation occurring in the highly excited system and to disentangle what causes the unexpected inertness to the otherwise energetically favored oxidation. Y1 - 2022 U6 - https://doi.org/10.1021/acs.jpclett.2c02327 SN - 1948-7185 VL - 13 IS - 36 SP - 8516 EP - 8521 PB - American Chemical Society CY - Washington, DC ER -