Helvetica Chimica Acta最新文献

Optical control of molecular beams is intriguing as it promises to become a new tool for mass spectrometry and quantum interferometry, where a single or two photons deterministically remove a tailored tag from a larger molecular structure, e. g., a polypeptide. This cleavage process can change the charge state of the macromolecule, provide reporting signals for both fragments by mass spectrometry and it can selectively remove the fragments from a molecular beam by the momentum recoil generated in the dissociation process. Here, we explore a series of porphyrin derivatives as candidates for photocleavage in the gas phase. They share a large, conjugated core which promises a high absorption cross section for visible light. We present the individualization and beam formation of candidate molecules and study their photo-dissociation under tunable, visible radiation. We observe a significant wavelength shift and broadening in the photocleavage cross section for molecules in the gas phase compared to those in solution and we find that a single photon can suffice to trigger the cleavage process.

The carbonylation of methyl nitrite (MN) to synthesize dimethyl carbonate (DMC) is a promising route, but the lack of efficient and stable catalysts remains a major challenge for large-scale applications. In this study, by adjusting the alkalinity of the initial gel, NaY zeolites with tunable acidity were synthesized, and the amount of Lewis acid sites was optimized. Appropriate amounts of Lewis acid sites facilitated the interaction between NaY zeolites and Pd species, which was beneficial for stabilizing the oxidation state of Pd and promoting CO adsorption and activation, thereby contributing to the formation of the key intermediate *COOCH₃. The catalyst PdCu/NaY-1 (alkalinity in the initial gel Na₂O=9) exhibited significant improvement in catalytic performance for the synthesis of DMC, with the WTY_DMC of 1604 g kg_cat⁻¹⋅h⁻¹, the conversion of CO to DMC (C_CO) of 88.7 %, and the DMC selectivity based on CO (S_DMC/CO) up to 100 %.

Protonation and tautomerization significantly impact the conformational landscape and non-covalent interactions in bis(oxazoline) (BOX) ligands, which are crucial for their applications in catalysis. These interactions influence properties such as binding affinity and catalytic efficiency. While tautomerization has been reported for neutral BOX ligands, its role in protonated forms remains less understood. Here we report the structural and spectroscopic characterization of (S,S−Ph-BOX)H⁺ and its tautomerization-resistant derivative (S,S−Ph-diMeBOX)H⁺. We show through IRMPD spectroscopy and TIMS experiments, combined with DFT calculations that (S,S−Ph-BOX)H⁺ is present in its tautomeric form, while a broader conformational landscape is observed for (S,S−Ph-diMeBOX)H⁺, in which an N−H⋅⋅⋅N proton-shared conformer is identified. These findings provide a deeper understanding of the relationship between tautomerization and non-covalent interactions in protonated BOX ligands, offering insights for the design of catalytic systems.

The rich chemistry of East Indian Sandalwood oil has fascinated chemists for over a century. Whilst the synthesis on industrial scale of the principal odour vector (−)-(Z)-β-Santalol 2, has resisted all attempts to date, many synthetic fragrant sandalwood ingredients have been discovered and manufactured on industrial scale. This precious wood is still listed as endangered and appears on the CITES red list, despite an increased number of plantations being developed. This review will focus on the interesting chemistry of Santalum album (Linn.) essential oil and the subsequent efforts by researchers to find a viable substitute for this highly appreciated oil both by investigating novel structures and using biotech approaches. The emphasis will be on the approaches to these highly appreciated odorants made from renewable resources that are currently manufactured on multi-MT scale. Lesser emphasis will be placed on close structural analogues that have not been commercially successful.

Native mass spectrometry ionizes biomolecules from aqueous buffered solutions using electrospray ionization. Collisions and lasers are often used to study the structures of such native biomolecular ions. While structural changes upon collisions have been studied in more detail, interactions with photons mostly comprise fragmentation. It remains unclear to what degree biomolecular ions undergo unfolding until cleavage. Here, gas-phase Förster resonance energy transfer (FRET) is used to study fluorescence lifetimes of a 32-residue α-helical peptide to monitor peptide unfolding. Increases in lifetime of up to 1.2 ns per charge are observed for different charge states, showing that a low charge is necessary for peptides to retain a compact structure. Increases in lifetime by up to 0.5 ns are observed upon collisional and laser-based activation and show that the peptide is partially unfolding upon activation. The results contribute to understanding the unfolding dynamics of biomolecules upon activation in mass spectrometry experiments.

The hydrolysis of dihydrazides was studied at different pH values in water at 25 °C. The resulting species were analyzed by HPLC, ¹H-NMR, and MALDI-TOF mass spectrometry. Among these species, unexpected molecules bearing carboxylate moieties were detected. Based on this analysis, a 2-step hydrolysis mechanism was proposed involving the formation of cyclic and linear intermediates before the addition of a water molecule to lead to carboxylate moieties. The first step was shown to be rate-determining and catalyzed in acidic conditions. To the best of our knowledge, this study shows for the first time that the hydrolysis of some dihydrazides can spontaneously occur in mild aqueous conditions, contrary to monohydrazides which do not reveal such a hydrolysis in same conditions. This draws attention to an overlooked degradation which might need more consideration, and possibly highlights new ways of soft hydrolysis conditions.

We present electric dipole polarizability calculations employing atomic-orbitals based linear response theory within the Kohn-Sham Density Functional Theory (KS-DFT) framework, considering both non-periodic and periodic boundary conditions. We adopt the optimization scheme introduced by T. Helgaker et al. in Chemical Physics Letters 327, 397 (2000) for the single-electron atomic-orbitals density matrix. We conduct a comparative analysis between the static polarizability computed using atomic orbitals-based and previously implemented molecular orbitals-based methods. In our calculations involving periodic boundary conditions, we implement polarizability calculation using velocity representation of the electric dipole operator in atomic orbitals-based algorithm, subsequently comparing the results with those computed using the Berry-phase formulation and velocity representation in molecular orbitals-based algorithm. We investigate 10 small and medium-sized molecules in the gas phase, analyze liquid-phase systems with up to 256 water molecules, and the solid-state structures of anatase TiO₂ and bulk WO₃. All polarizability results obtained from the AO-based solver exhibit good agreement with MO-based results. From our example calculations, we find that the AO-based solver exhibits better computational scaling and less memory demand than the MO-based solvers, which makes it better suited for very large systems.

The beginning of 2025 marks the completion of our first 3-year mandate as Editors-in-Chief of Helvetica Chimica Acta. This has been an exciting and intensive period of time, which has allowed us to drive forward our vision for the journal. We are now delighted to renew our commitment with Helvetica for a second (and last) three year mandate. Having said that, we also feel that now it is the right time to reflect on what we have achieved so far and to give new impulses for the future.

Thermoresponsive polymers, which undergo phase transitions within physiologically tolerated temperatures, are key to developing drug delivery systems (DDS) with precise spatial and temporal control, potentially addressing challenges associated with the treatment of complex diseases. Inorganic nanoparticles with unique optical, electronic, and magnetic properties serve as efficient transducers, converting external stimuli into localized heat to trigger thermoresponsive nanocarriers. This review explores the design and application of thermoresponsive nanocarriers transduced by inorganic nanoparticles as DDS. Following a brief description of temperature-triggered phase transition of polymers and heat generation mechanisms by inorganic nanoparticles, strategies to integrate these components into hybrid systems are described. Examples demonstrating the utility of these hybrid systems as advanced DDS are discussed, highlighting their potential for precise drug release alongside theranostic capabilities by combining therapy with imaging. Despite the challenges in design, synthesis, and biological applications, thermoresponsive polymer-inorganic hybrids hold immense promise for transforming drug delivery and biomedical innovations.