Publications du Département de Chimie physique


Excitation Energies of Embedded Chromophores from Frozen-Density Embedding Theory Using State-Specific Electron Densities of the Environment
Fu, M.; Wesolowski, T. A.
J. Phys. Chem. A 2023, 127, 535-545.

Starting from the Perdew–Levy theorem on extrema of the Hohenberg–Kohn functional, the expression for the vertical excitation energy is derived within the formal framework of Frozen-Density Embedding Theory (FDET) that makes it possible to use state-specific electron densities of the environment (ρB) of an embedded species. The derived general expression involves the embedded wave functions for ground and excited states that are orthogonal and is exact up to quadratic terms in the appropriate density expansion. It can be applied in practice using various methods differing in the treatment of the electron–electron correlation for embedded electrons, the method to evaluate different contributions to the excitation energy, the method to generate state-specific ρB, and the approximation used for the non-electrostatic component of the FDET embedding potential. The derived expression is applied for 47 local excitations in 10 embedded organic chromophores. The explicit treatment of the differential polarization of ρB improves indeed the accuracy of the excitation energy as compared to the implicit treatment in which the same ρB is used for all states of embedded chromophore. For 47 local excitations in 10 embedded organic chromophores, the average absolute errors in excitation energies drop from 0.04 to 0.03 eV and their standard deviations from 0.032 to 0.025 eV, respectively. The maximal errors show similar trends.

Room-Temperature Bistability in Spin Crossover-Loaded Metal–Organic Frameworks
Shen, Y.; Woodburn, J.; Bouras, S.; Dai, S.; Dovgaliuk, I.; Grenèche, J.-M.; Patriarche, G.; Lawson Daku, L. M.; Serre, C.; Tissot, A.
Chem. Mater. 2023, 35, 719-727.

In this article, we present an unprecedented strategy to prepare bistable porous nanocrystals based on the anchoring of switchable molecules in the pores of a host matrix through strong host–guest interactions. More precisely, we have inserted a prototypical Fe(III) spin-crossover complex in MOF-808, a chemically robust large-pore Zr-based MOF. The loaded nanocrystals present a hysteretic thermal spin transition close to room temperature that is independent of the complex loading and the MOF particle size while remaining highly porous, which opens up opportunities for their use as chemical sensors.

Isolation of a novel heterodimeric PSII complex via strep-tagged PsbO
Lambertz, J.; Meier-Credo, J.; Kucher, S.; Bordignon, E.; Langer, J. D.; Nowaczyk, M. M.
Biochim. Biophys. Acta, Bioenerg. 2023, 1864, 148953.

The multi-subunit membrane protein complex photosystem II (PSII) catalyzes the light-driven oxidation of water and with this the initial step of photosynthetic electron transport in plants, algae, and cyanobacteria. Its biogenesis is coordinated by a network of auxiliary proteins that facilitate the stepwise assembly of individual subunits and cofactors, forming various intermediate complexes until fully functional mature PSII is present at the end of the process. In the current study, we purified PSII complexes from a mutant line of the thermophilic cyanobacterium Thermosynechococcus vestitus BP-1 in which the extrinsic subunit PsbO, characteristic for active PSII, was fused with an N-terminal Twin-Strep-tag. Three distinct PSII complexes were separated by ion-exchange chromatography after the initial affinity purification. Two complexes differ in their oligomeric state (monomeric and dimeric) but share the typical subunit composition of mature PSII. They are characterized by the very high oxygen evolving activity of approx. 6000 μmol O2·(mg Chl·h)−1. Analysis of the third (heterodimeric) PSII complex revealed lower oxygen evolving activity of approx. 3000 μmol O2·(mg Chl·h)−1 and a manganese content of 2.7 (±0.2) per reaction center compared to 3.7 (±0.2) of fully active PSII. Mass spectrometry and time-resolved fluorescence spectroscopy further indicated that PsbO is partially replaced by Psb27 in this PSII fraction, thus implying a role of this complex in PSII repair.

Circularly Polarized Luminescence from Atomically Precise Gold Nanoclusters Helically Assembled by Liquid-Crystal Template
Lipok, M.; Obstarczyk, P.; Parzyszek, S.; Wang, Y.; Bagiński, M.; Buergi, T.; Lewandowski, W.; Olesiak-Bańska, J.
Adv. Opt. Mater. 2023, in press.

Chiral plasmonic gold nanoparticles assemblies are known for their strong circular dichroism. However, little is known about the creation of helical assemblies from atomically precise nanoparticles like gold nanoclusters (AuNCs) and the optical properties of the final structures. Herein, a new approach is proposed to helically assemble atomically precise gold nanoclusters and enable circularly polarized luminescence using a liquid-crystal template creating helical nanofilaments. The problem of nanoclusters miscibility is resolved with the liquid crystal matrix by functionalizing nanoclusters with two different ligands: dodecanethiol and specially designed liquid crystal-like ligand. Additionally, the authors explore how functionalization, heating, and helical assembly affect optical properties of gold nanoclusters. The findings prove that assembly incorporating thermotropic liquid crystals and double functionalization of nanocluster surface can be successfully applied to assemble ultrasmall nanoparticles in a helical manner while preserving their atomically precise structure. Moreover, the assembly tunes the nanocluster luminescence and generates new chiroptical effects.

Nanomechanical and structural study of Au38 nanocluster Langmuir-Blodgett films using bimodal atomic force microscopy and X-ray reflectivity
Swierczewski, M.; Chenneviere, A.; Lee, L.-T.; Maroni, P.; Bürgi, T.
J. Colloid Interface Sci. 2023, 630, 28-36.


Langmuir-Blodgett (LB) technique allows the deposition of gold nanoparticles and nanoclusters (atomically precise nanoparticles below 2 nm in diameter) onto solid substrates with an unprecedented degree of control and high transfer ratios. Nanoclusters are expected to follow the crinkle folding mechanism, which promotes the formation of trilayers of nanoparticles but kinetically disfavors the formation of the fourth layer.


LB films of Au38(SC2H4Ph)24 nanocluster were prepared at a range of surface pressures in the bilayer/trilayer regime and their internal structure was analyzed with X-ray Reflectivity (XRR) and Grazing-Incidence Wide-Angle X-ray Scattering (GIWAXS). Bimodal atomic force microscopy (AFM) imaging was used to quantify the elastic modulus, which can be correlated with the topography at the same point on the surface.


Nanocluster bilayers and trilayers exhibited the elastic moduli of ca. 1.2 GPa and 0.9 GPa respectively. Films transferred in the 20–25 mN/m surface pressure regime displayed a particular propensity to form highly vertically organized trilayers. Further compression resulted in disorganization of the layers. Crucially, the use of two cantilevers of contrasting stiffness for bimodal AFM measurements has demonstrated a new approach to quantify the mechanical properties of ultrathin films without the use of deconvolution algorithms to remove the substrate contribution.

Efficient Photoredox Cycles to Control Perylenediimide Self-Assembly
Chen, C.; Valera, J. S.; Adachi, T. B. M.; Hermans, T.
Chem. Eur. J. 2023, 29, e202202849.

Photoreduction of perylenediimide (PDI) derivatives has been widely studied for use in photocatalysis, hydrogen evolution, photo-responsive gels, and organic semiconductors. Upon light irradiation, the radical anion (PDI •– ) can readily be obtained, whereas further reduction to the dianion (PDI 2– ) is rare. Here we show that full 2-electron photoreduction can be achieved using UVC light: 1) in anaerobic conditions by ‘direct photoreduction’ of PDI aggregates, or 2) by ‘indirect photoreduction’ in aerobic conditions due to acetone ketyl radicals. The latter strategy is also efficient for other dyes, such as naphthalenediimide (NDI) and methylviologen (MV 2+ ). Efficient photoreduction on the minute time-scale using simple LED light in aerobic conditions is attractive for use in dissipative light-driven systems and materials.