The rotational spectrum of the weakly bound complex 2,3,4,5,6-pentafluorotoluene···water has been investigated using chirped pulse Fourier transform microwave spectroscopy in the 2-8 GHz region. The spectrum of the adduct splits in four components due to two tunneling motions. One is the internal rotation of the methyl group and the other is the internal rotation of the water subunit which leads to the characteristic 1:3 relative intensity ratio due to nuclear spin statistical weights. Contrary to the expectations water is not lying above the aromatic ring forming a lone pair-pi hole interaction as occurs in related fluorinated arenes L. Evangelisti, K. Brendel, H. Mäder, W. Caminati, S. Melandri, Angew. Chem. Int. Ed. 2017, 56 13699-13703^, C. Calabrese, Q. Gou, A. Maris, W. Caminati, S. Melandri, J. Phys. Chem. Lett., 2016, 7,1513–1517ut it is above the ring forming an O−H···F bond with the ortho fluorine substituent reinforced by a C−H···O interaction with the methyl group. This interaction with the methyl group raises the value of the barrier hindering the methyl group rotation from a nearly zero value predicted for 2,3,4,5,6−pentafluorotoluene to a value close to 1.5 kJ/mol as determined from analysis of the rotational spectrum.\end

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\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end\end L. Evangelisti, K. Brendel, H. Mäder, W. Caminati, S. Melandri, Angew. Chem. Int. Ed. 2017, 56 13699−13703

Rotation of the fluoromethyl group in allyl fluoride results in three minima: an achiral rotamer that contains a plane of symmetry and two equivalent, chiral rotamers that form an enantiomeric pair. As revealed though the analysis of the microwave spectra, the gas-phase heterodimers formed between each rotamer and the argon carrier gas share similar structural features showing the expected interactions between argon and heavy atoms in allyl fluoride, specifically the fluorine atom and the carbon atom of the fluoromethyl group. However, the heterodimers with acetylene, while each containing remarkably similar interactions between the fluorine atom and an acetylenic hydrogen, adopt distinctly different geometries.

Structures for the gas-phase heterodimers of 3,3,3-trifluoropene with argon and with acetylene are obtained from the analysis of the microwave spectra of each complex. While the binding of argon to the olefin is similar to previously characterized complexes, with argon locating in the FCC=CH cavity, but away from the olefinic plane, the structure of the heterodimer with acetylene displays a unique structural motif. Namely, the acetylene lies in the symmetry plane of the propene, forming a bifurcated hydrogen bond with the two, equivalent out-of-plane fluorine atoms.

Rotation of the chlorodifluoromethyl group in 3-chloro-3,3-difluoropropene results in three minima: a higher energy, achiral rotamer that contains a plane of symmetry and two equivalent, chiral lower-energy gauche rotamers that form an enantiomeric pair each with the chlorine atom and one of the fluorine atoms out of the olefinic plane. Both rotamers are seen in the 2 to 18 GHz microwave rotational spectrum and their spectra analyzed. Spectra for the gas-phase heterodimers of the gauche rotamer with argon and with acetylene are also observed. In the heterodimer with argon, the rare gas atom interacts primarily with the chlorine atom, but also is located near to the in-plane fluorine atom and the C=C double bond. The structure of the acetylene complex appears to be predominantly the result of favoring electrostatic interactions, containing a hydrogen bond to the out-of-plane fluorine atom and a secondary interaction with an olefinic hydrogen. However, the linear acetylene molecule and these two atoms do not all lie in the same plane, suggesting a potential additional interaction with the out-of-plane chlorine atom.

Weakly bound molecular complexes are involved in many biological and chemical processes, including those occurring in the Earth’s atmosphere. Dinitrogen, being its most abundant component, was found to interact strongly with various molecules, considerably changing their spectroscopic properties. In turn, carbon dioxide is one of the main greenhouse gases present in the atmosphere. Triazoles are characterized by the presence of a rigid structure containing acidic A-H moieties as well as electron pair donors. They are widely used e.g. as building blocks for the formation of various metal–organic frameworks (MOFs) designed for many purposes, including gas storage and separation. Type and mode of interaction of greenhouse gases with organic molecules is a broad topic of investigation, in which it is necessary to gain deeper insight in order to understand how these systems behave at the molecular level. In this work, interactions between selected 1,2,4-triazoles and N₂/CO₂ were studied theoretically by the DFT/B3LYP-D3 method and experimentally by FTIR spectroscopy combined with the matrix isolation technique. It is an especially powerful method in structural studies, including hydrogen bonds and Van der Waals type interactions, allowing to investigate weakly bonded species. The research was aimed at finding correlations between the structure of the heterocyclic compounds and the way they bind with the gas molecules of interest. Based on the direct comparison between theoretical and experimental IR band positions and wavenumber shifts, together with AIM calculation results, it was possible to identify particular geometries of the complexes formed in the matrix cage, as well as learn the influence of the matrix environment on their spectroscopic properties.K. Mucha, M. Pagacz-Kostrzewa, J. Krupa, M. Wierzejewska, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 285 (2023) 121901.^, K. Mucha, M. Pagacz-Kostrzewa, M. Wierzejewska, Journal of Photochemistry Photobiology A: Chemistry 443 (2023) 114873.

A large number of infrared spectroscopic studies have been performed to reveal the microscopic nature of hydrogen bond. Cyclohexane is one of the known nonpolar solvents. In general neutral clusters, nonpolar molecules do not play a role as proton acceptors in hydrogen bonds. However, the proton affinity value of cyclohexane is close to that of water. This suggests that the cyclohexane molecule can act as a proton acceptor in hydrogen bonds. Therefore, it is interesting to see how the cyclohexane molecule behaves in a cluster with phenol. Since phenol has been studied as a proton donor in many systems over a wide range of hydrogen bond strengths, the hydrogen bond structures and their strengths can be compared with other clusters. In the present study, we have performed infrared spectroscopy of phenol-cyclohexane clusters. In the case of the phenol-cyclohexane 1:1 cluster, an infrared spectrum and theoretical calculations revealed that the cyclohexane moiety is located on the phenyl ring like other nonpolar molecules. However, in the case of the phenol-cyclohexane 1:2 cluster, we found a small but significant redshift in the wavenumbers of the OH stretching bands. This suggests that one of the cyclohexane molecules in the cluster plays a proton acceptor role in the cluster.

Non-covalent interactions have an important impact on atmospheric chemistry, affecting existing reactions and contributing to new reaction channels. Molecular complexes formed in dense environments at low temperature can affect the chemistry of interstellar media and some planetary atmospheres. Isothiocyanic acid (HNCS) and isocyanic acid (HNCO) represent important prebiotic interstellar molecules and were detected in the rich molecular cloud Sagittarius B2 (Sgr B2). We will present results of theoretical and experimental studies of aggregates and complexes formed by HNCS and HNCO with small molecules. As the main experimental method, matrix isolation (MI) combined with the infrared spectroscopy (FTIR) was used. Matrix isolation technique allows to trap and investigate weakly bonded systems, and may be considered as a good approximation to the gas phase, as well as microscopic molecular confinement. The experimental studies were supported by theoretical calculations at the MP2 and B3LYPD3 levels with the 6-311++G(3df,3pd) basis set. Direct comparison between computed and experimental spectra, considering both wavenumber shifts of the bands and their relative intensities will be presented for HNCSKrupa J., Wierzejewska M. Chem.Phys.Lett. 652, (2016), 46-49.nd HNCOKrupa J., Wierzejewska M., Lundell J. Molecules 28, (2023), 1430/1-1430/14.imers as well as their complexes with N₂Krupa J., Wierzejewska M., Lundell J. Molecules 27, (2022), 495/1-495/16.nd SO₂Krupa J., Wierzejewska M. Spectrochim. Acta A 183, (2017), 144-149.^, Krupa J., Wierzejewska M., Lundell J. Molecules 26, (2021), 6441/1-6441/13..

r0pt Figure The B²Σ⁺_1/2 interatomic potentials of alkali-rare gas pairs can be determined through calculations of Franck-Condon factors. Through white light absorption spectroscopy, the free-free optical transitions of these atomic collision pairs can be observed. In particular, the X²Σ⁺_1/2←B²Σ⁺_1/2 transition is measured as shown in the figure for a RbXe molecule. Through these experiments, the relative absorption coefficient, k(λ), is recorded for the blue satellite features. From these measurements, a comparison of the experimental results and theoretical models is made. Current theoretical models do not correctly determine the alkali-rare gas blue satellites. The free-particle wave functions are calculated for the theoretical models using the appropriate J values, and k(λ) is calculated using the equation below. Through an iterative process the B²Σ⁺_1/2 interatomic potentials are calculated, correctly predicting the blue satellite feature.

Novel morpholine derived compounds were docked to Homo sapiens anticholinesterase (AChE) enzymes. The induced fit docking analysis were performed for AChE with the compounds and galantamine. The binding free energies of the compounds were determined using the MM/GBSA approach. ADME analyses conducted using the QikProp program indicate that all compounds adhere to Lipinski’s rule of five without any violations. Additionally, both the constituents and their cognate drugs underwent a 100 ns and molecular dynamic simulation to forecast their stability within the enzymes' active sites. The Schrodinger module was utilized for molecular docking (IFD) and molecular dynamic (Desmond) analyses.

The structure of the hydrated electron has been the subject of much recent debate. The classical model based on EPR and room temperature resonance Raman studies, which suggested that hydrated electron carves out a cavity, locally expelling the water and behaving roughly as a particle in a quasi-spherical box, was recently confronted by calculations indicating that the excess electron’s wavefunction incorporates several water molecules in a structure with only a small or even no central cavity. The non-cavity computational model matched some of the earlier room temperature resonance Raman observations, additionally forecasting no spectrum sensitivity to the temperature variation. The same model anticipated a substantial decrease in the hydrated electron fluorescence emission amplitude underlying the Raman features upon the temperature increase from 0 to 40^°C. We performed inelastic light scattering measurements of aqueous solutions containing hydrated electrons, allowing observation of their Raman and fluorescence emission in the temperature range from 4 to 60^°C. The spectra were measured in resonance with hydrated electron light absorption at 633 nm. Our room temperature spectra of hydrated electrons agreed very well with earlier observations showing enhancement of water inter- and intramolecular vibrations in the presence of electrons accompanied by frequency downshifts of the resonantly enhanced H₂O bend to 1610 cm⁻¹and of the OH stretch to  3100 cm⁻¹. Upon temperature decrease to 4^°C, the resonantly enhanced H₂O bend position upshifts  8.8 cm⁻¹closer to the bulk solvent position. Upon temperature increase to 60^°C, the resonantly enhanced H₂O bend position downshifts 10 cm⁻¹from the room temperature position. The fluorescence emission amplitude to enhanced bend peak amplitude ratio remains unchanged within the experimental error in the studied temperature range. Qualitatively analogous observations were also obtained for the temperature dependence of hydrated electron spectra in heavy water. All these observations contradict predictions from non-cavity computational models of hydrated electrons.