Chemphyschem最新文献

Exciton coupling model provides one of the most intuitive and powerful frameworks to directly connect molecular structure with chiroptical responses. This review focuses on rigid architectures with C₂ symmetry, in which conformational rigidity, symmetry constraints, and independent chromophores allow for direct correlations among molecular geometry, Davydov splitting, and electronic circular dichroism intensity. After introducing the theoretical basis of exciton coupling and its crucial role in absolute configuration assignment, we analyze how molecular design strategies control the conformational space, as well as how the electron transition dipole moments of interacting chromophores enable the modulation of dissymmetry factors (g-factors). Next, we expand these principles from isolated molecules to supramolecular assemblies, thin films, and polymers, where cooperative effects and new structural constraints can come into play to amplify or distort excitonic signatures. Overall, this review compiles transferable design principles to guide the development of next-generation chiroptical materials with broad relevance for sensing, optoelectronic, and spintronic applications.

Using combined geometry optimization and electronic analyses, it is examined how metal nature (alkali and Cu(I)), solvation (THF), ligands, and aggregation modulate the N- versus C-bonding balance in metalated acetonitrile. C-binding is energetically favored in covalent Cu(I) complexes, while lithiated species prefer N-binding. Surprisingly, N-metalated species do not all exhibit the expected ketenimine-like character (CCN, lone pair on N), but a nitrile-like one (C^bC≡N, lone pair on C^b) also emerges from the natural bond orbital analyses. Ketenimines are stabilized by polarizing or covalent MN bonds, while nitriles are obtained with weakly coordinating cations or in anionic species. Notably, an external electric field can induce a similar electronic reorganization, thus revealing the electronic flexibility of metalated nitriles.

Metal responsive transcription factors are essential for bacterial metal homeostasis, allowing cells to regulate metal uptake, efflux, and detoxification in response to fluctuating metal ion levels. Among these, CueR, a member of the MerR family, is widely found in Gram-negative bacteria. While E. coli CueR has been extensively studied, revealing that it adopts multiple conformational states to regulate transcription, P. aeruginosa CueR (PACueR) remains less characterized, with no resolved structure despite regulating a broader set of genes. In this study, we applied electron paramagnetic resonance (EPR) spectroscopy combined with DNA spin-labeling to investigate the conformational states of PACueR bound to two different promoter sequences, copZ2 and mexPQ-opmE. We examined the effects of PACueR binding and copper addition, capturing the transcription initiation stage that represents an essential step in copper homeostasis regulation of P. aeruginosa. Our results reveal promoter-specific differences in PACueR DNA interactions, suggesting that while the core transcription initiation mechanism is conserved, variations in promoter affinity and length of dyad symmetry fine-tune transcription levels in response to copper. These findings highlight the value of EPR spectroscopy in probing metal-dependent transcription mechanisms and offer new insights into copper regulation in P. aeruginosa, a clinically important pathogen.

The Front Cover shows how aromatic cyano compounds might have played an important role in the molecular complexity associated with the origin of life. Benzonitrile interacts with low-energy electrons to produce CN⁻ anions through coupling between π* and σ* orbitals, which leads to C─CN bond cleavage. More information can be found in the Research Article by L. M. Cornetta, F. Ferreira da Silva and co-workers (DOI: 10.1002/cphc.202500206).

The feasibility of the C₁₀₀ fullerene as a nanocontainer for glycine, alanine, and serine has been investigated using density functional theory (B3LYP-D3), second-order Møller-Plesset perturbation theory, and the domain-based local pair natural orbital-coupled cluster singles doubles and perturbative triples (DLPNO-CCSD(T)) method. The interaction energies for glycine@C₁₀₀, alanine@C₁₀₀, and serine@C₁₀₀ are calculated to be -47.8, -45.5, and -43.8 kcal mol^-1, respectively, for their most stable conformers, at the DLPNO-CCSD(T) level, indicating favorable host-guest interactions. Furthermore, encapsulation leads to substantial stabilization of both the intramolecular hydrogen-bonded and nonhydrogen-bonded conformers of the amino acids. Vibrational frequency analysis shows a blueshift for most of the vibrational modes, indicative of restricted motion due to the confined space. However, the OH-stretch mode, especially for the intramolecular hydrogen-bonded conformers, exhibits a large redshift upon encapsulation, suggesting a strengthening of the hydrogen bond due to confinement. The results of the dipole moment calculations reveal a significant reduction in the dipole moment after encapsulation, indicating an effective screening of the dipole by the C₁₀₀ cage. ¹H NMR chemical shift calculations reveal a large downfield shift, consistent with the deshielding effects experienced by the encapsulated molecules due to the unique electronic environment within the fullerene cavity.

Stimulated by recent findings of a beneficial effect of a high-temperature treatment on the activity and selectivity of highly active and selective Ru/TiO₂ catalysts in the CO_x methanation, a detailed study of the dynamic changes in the chemical and structural properties is performed, induced by this treatment and their correlation with the changes in the catalytic performance of the catalyst. These changes are characterized by time-resolved operando X-ray absorption spectroscopy at the Ru and Ti K-edges, together with structural characterization by high-resolution transmission electron microscopy. The observation of differently long times required for the reduction of the oxidic Ru nanoparticles in CO-free CO₂/H₂ gas mixtures (1000 min) and in trace amounts of CO containing CO/CO₂/H₂ gas mixtures (100 min) under reaction conditions (190 °C, atmospheric pressure) correlates very well with the different times required for catalyst activation in these reaction gas mixtures.

Herein, a density functional theory based mechanistic and kinetics study of experimentally reported pincer metal complex catalyzed homogenous dehydrogenation of methanol and diamine into diamide is explored. The reaction proceeds through dehydrogenation and hydrogenation reactions for the reversible interconversion between methanol and diamine. The mechanism proceeds via a step-by-step formation of aldehyde, amide, and diamide complexes. The generated formaldehyde reacts with ethylenediamine in the second cycle to make monoamide, which reacts with formaldehyde from the first cycle to produce diamide. The complete diamide formation reaction follows a cross-multicarrousel type mechanism. The turnover-determining transition state is the formation of the first amide bond, where the addition of amine and metal aldehyde takes place. The alternative reaction of metal aldehyde and alcohol via an ester formation reaction is a minor path. The rate equation is derived from the most feasible path. From the dissociation dynamics simulations, the dehydrogenation reaction of metal hydride is found to be favorable, and a strong Mn and H₂ interaction is present during the H₂ release, which may facilitate the hydrogenation reaction. Diamide dissociation is more challenging than amide dissociation, and a high temperature is required for diamide dissociation dynamics.

Modular synthetic modification to ligand scaffolds of metal complexes provides an approach to rational improvement of existing molecular catalytic systems. A previous report from the Marinescu group has shown that a cobalt phosphino thiolate complex ([Co(triphos)(bdt)]⁺) has excellent selectivity and activity for electrocatalytic CO₂ reduction to formate. Here, a multimetallic analogue, [Co₃(triphos)₃(tht)]³⁺, that is conjugated through a trinucleating dithiolene ligand in the form of triphenylene–2,3,6,7,10,11–hexathiolate is investigated. While voltammetric studies indicate enhanced current densities under similar conditions to [Co(triphos)(bdt)]⁺, electrolysis and ultraviolet–visible spectroscopy results suggest significant catalyst degradation and overall moderate faradaic yields.

The ionizing radiation acting on DNA results in various kinds of damage including base modifications. The Cover Feature illustrates the appearance of 8-oxo-guanine (OG) and 5-formyl-cytosine (5fC) as oxidation products resulting from the indirect effect of radiation on the DNA double helix. The picture highlights the high mutagenicity of the OG lesion, which can mispair with adenine, guanine, and thymine bases, leading to transition and transversion mutations after DNA replication. More information can be found in the Research Article by V. Poltev and co-workers (DOI: 10.1002/cphc.202400964). Cover design by V.D. and V.P.

Electrochemical fluorination on a nickel anode (Simons process) is an important process for producing fluorinated compounds. Despite its success, the mechanism is still under debate. Here a first-principles study is presented of fluorination of ethene on a model fluorinated (001) NiF$$ surface, which is chosen because it is stabilized under the external potential close to that at which the Simons cell operates and because it has a readily available $$ unit providing fluorine source to aid fluorination reactions. The adsorption of the simplest double bond containing hydrocarbon on this surface is investigated. It is placed on the surface in different orientation, leading to six distinct structural outcomes upon relaxation. These include formation of 1,2-difluoroethane, fluoroethene, and 1,2-difluoroethene, alongside other fluorinated products as well as monocarbon fragments. This is one of the first computational studies of the catalytic Simons-type fluorination and can, despite its simplicity, offers some insight into reaction pathways and surface interactions.