Artykuły IChO PAN

Displaying 1 - 5 of 209 records

Monitoring the Switching from Base-on to Base-off Forms of Vitamin B12 by Natural and Magnetic Circular Dichroism Spectroscopies
(ACS Publications, 2026) Machalska, Ewa; Mazzeo, Giuseppe; Wierzba, Aleksandra J.; Dybas, Jakub; Rode, Joanna E.; Abbate, Sergio; Gryko, Dorota; Baranska, Malgorzata; Longhi, Giovanna; Fusè, Marco; Department of Molecular and Translational Medicine, Università di Brescia; Jagiellonian Centre for Experimental Therapeutics (JCET), Jagiellonian University; Institute of Organic Chemistry, Polish Academy of Sciences; Istituto Nazionale di Ottica CNR, Unità di Brescia; Department of Biochemistry, University of Colorado; BioFrontiers Institute, University of Colorado; Laboratory for Spectroscopy, Molecular Modeling and Structure Determination, Institute of Nuclear Chemistry and Technology; Faculty of Chemistry, Jagiellonian University
This work demonstrates that an approach which makes use of magnetic circular dichroism (MCD) together with electronic circular dichroism (ECD) brings one to a rapid, sensitive, nondestructive, and inexpensive determination of the electronic structure of diamagnetic, chiral, and flexible molecular systems. The subject of this study is cobalamins (Cbls), including vitamin B12, the unique and intricate structure of which determines their selective and strong protein binding. Their existence in two forms (base-on and base-off) not only causes significant structural changes but also influences the reactivity of B12 derivatives in biologically important organometallic reactions. Therefore, recognizing the Cbl forms and understanding how they switch between them is essential. Notably, this study is the first to show that combining MCD and ECD, supported by quantum mechanics calculations, allows differentiation between base-on and base-off Cbls in aqueous environment at pH 7.4 and in acidic conditions, respectively. Furthermore, these techniques are sensitive to Cbl modifications at the meso position of the corrin macrocycle or in the axial upper ligands.
The versatile world of cumulene chemistry
(Royal Society of Chemistry, 2026) Pareek, Abhishek; Qiu, Yu; Johnson, Matthew A.; Tykwinski, Rik R.; Gaweł, Przemysław; Institute of Organic Chemistry, Polish Academy of Sciences; Department of Chemistry, University of Alberta, Canada
Despite a history spanning over a century, cumulenes are often relegated to the realm of perceived curiosities rather than practical synthetic intermediates as a result of their high intrinsic reactivity. In this review, we bridge the gap between the known synthetic strategies for these “exotic” molecules and the potential of their reactivity. By surveying both even and odd [n]cumulenes, paying particular attention to the most accessible [3]cumulenes, alongside more limited but instructive examples of [4]- and [5]cumulenes, we demonstrate that these sp-hybridized frameworks offer exceptional synthetic versatility. Indeed, cumulenes can function effectively as nucleophiles, electrophiles, and dienophiles, enabling cyclooligomerization, cycloaddition, organometallic coupling, and other transformations. We describe how these reactions utilize the “naked” sp-hybridized carbon atoms of the cumulene and their substantial internal energy to access structurally diverse products that would otherwise be challenging or even impossible to obtain using more traditional routes. In doing so, we aim to showcase their potential in organic synthesis and highlight the opportunities they present for constructing novel molecular architectures. By reframing cumulenes as valuable synthetic building blocks, rather than mere curiosities, this review hopes to persuade chemists to incorporate these intriguing scaffolds more broadly into modern organic synthesis.
Taming Boroloborinines: Toward Photostable Polycyclic Antiaromatic Hydrocarbons
(Royal Society of Chemistry, 2026) Mehboob, Muhammad Yasir; Sheeja, Minu; Sasar, Mahdi; Foroutan-Nejad, Cina; Institute of Organic Chemistry, Polish Academy of Sciences
Boron-containing heterocycles are attracting growing attention due to their unique electronic structures and effectiveness as electron acceptors in functional organic materials. Among them, boroloborinines, a fused borole–borinine scaffold, constitute a rare class of 8π-electron antiaromatic systems with potential applications in organic electronics. However, their inherent antiaromatic instability has limited synthetic exploration and practical deployment. In this work, we employ density functional theory (DFT) along with wavefunction based methods to systematically investigate strategies for stabilizing boroloborinine derivatives via nitrogen incorporation and selective benzannulation. Photochemical stability is evaluated using HOMO–LUMO and singlet–triplet (S–T) energy gaps, while aromaticity is assessed through three classes of indices: the multicenter index (MCI), the Harmonic Oscillator Model of Aromaticity (HOMA), and magnetically induced ring currents (MICD). Our findings show that both the position and nature of substitution critically influence electronic structure, with the formation of Clar’s sextets correlating strongly with increased stability. Molecules that exhibit reduced antiaromaticity in the singlet state and minimal aromaticity in the triplet state tend to possess the largest S–T gaps. Besides photostability, we examined proton affinity of our model systems to verify which molecules can remain stable in acidic environment. Our modeling suggest that nitrogen atoms in the vicinity of boron have higher proton affinity; therefore, they are potentially more prone to acid catalyzed reactions. These insights provide guiding principles for designing antiaromatic chromophores with enhanced stability and tunable optoelectronic properties, potentially enabling the development of novel organic emitters with distinct emission wavelengths and improved quantum yields.
N-Aryl substituents have an influence on the photophysics of tetraaryl-pyrrolo[3,2-b]pyrroles
(Royal Society of Chemistry, 2026) Petrykowski, Wojciech D.; Banasiewicz, Marzena; Morawski, Olaf; Kałuża, Zbigniew; Barboza, Cristina A.; Gryko, Daniel T.; Institute of Organic Chemistry, Polish Academy of Sciences; Institute of Physics, Polish Academy of Sciences
The photophysics of two series of 1,4-dihydro-tetraaryl-pyrrolo[3,2-b]pyrroles possessing N-aryl substituents with various electronic characteristics was investigated systematically. The molecular structure of these compounds was designed so that their solubility enabled us to study their absorption and emission in a broad range of solvents. The presence of N-4-nitrophenyl substituents is responsible for a weak charge-transfer absorption band and shifts the emission band hypsochromically. At the same time, their presence quenches fluorescence; although if electron-withdrawing substituents are present at positions 2 and 5, this effect is reduced by an order of magnitude. In the case of less electron-withdrawing N-4-cyanophenyl and N-3-cyanophenyl groups, strong emission is present only if the electron-withdrawing groups are located at positions 2 and 5. The combined experimental and computational study points out the existence of a barrier between au (bright) and ag (dark) CT states, the height of which is the key factor governing the fate of these molecules in the excited state. Weaker electronic communication at positions 1 and 4 of the DHPP core is responsible for strong charge separation. Polar solvents favor the formation of transient dipole moments due to excited-state symmetry-breaking, which amplifies the nonradiative deactivation of nitro-TAPPs. A large increase in fluorescence intensity at 77 K suggests that internal conversion is a key channel for non-radiative electronic relaxation. Conversely, moderate to weak electron-donating groups favor strong LE emission.
Physicochemical Characterisation of Ceftobiprole and Investigation of the Biological Properties of Its Cyclodextrin-Based Delivery System
(MDPI, 2025) Boczar, Dariusz; Bocian, Wojciech; Małek, Krystian; Milczarek, Małgorzata; Laudy, Agnieszka Ewa; Michalska, Katarzyna; Department of Synthetic Drugs, National Medicines Institute; Institute of Organic Chemistry, Polish Academy of Sciences; Department of Biomedical Research, National Medicines Institute; Department of Pharmaceutical Microbiology and Bioanalysis, Medical University of Warsaw
Ceftobiprole is a novel and promising antibiotic; however, the direct pharmacological use of its native form is limited by its low water solubility. The first part of this study provides a deeper insight into the physicochemical properties of this drug. One- and two-dimensional nuclear magnetic resonance (NMR) spectra in D2O were recorded, and a complete assignment of 1H and 13C signals was achieved with the support of quantum mechanical calculations. The combined results from capillary electrophoresis and NMR confirmed the cationic nature of ceftobiprole at pH values well below 3 and the protonation of the secondary amino group, thus supporting the theoretically predicted dominant protonation states. Molecular dynamics simulations revealed that zwitterionic ceftobiprole molecules associate through hydrogen bonding, whereas in the cationic form, the attractive forces involve weaker π-π and stacking interactions. The use of ceftobiprole in its native form in pharmaceutical formulations was made possible through the development of a novel freeze-dried cyclodextrin-based delivery system. Consequently, the second part of this article focuses on evaluating the biological properties of this system (ceftobiprole/maleic acid/sulfobutylether-β-cyclodextrin in a molar ratio of 1:25:4), including its antibacterial activity against the most common pneumonia-causing pathogens and its cytotoxicity towards normal and cancer cells.

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