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The rotational spectrum of an acrolein–formaldehyde complex has been characterized using pulsed jet Fourier transform microwave spectroscopy complemented with quantum chemical calculations. One isomer has been observed in pulsed jets, which is stabilized by a dominant O=C⋯O tetrel bond (n → π* interaction) and a secondary C–H⋯O hydrogen bond. Splittings arising from the internal rotation of formaldehyde around its C2v axis were also observed, from which its V2 barrier was evaluated. It seems that when V2 equals or exceeds 4.61 kJ mol−1, no splitting of the spectral lines of the rotational spectrum was observed. The nature of the non-covalent interactions of the target complex is elucidated through natural bond orbital analysis. These findings contribute to a deeper understanding on the non-covalent interactions within the dimeric complex formed by two aldehydes. [ABSTRACT FROM AUTHOR]

Chromones are a class of naturally occurring compounds, renowned for their diverse biological activities with significant relevance in medicine and biochemistry. This study marks the first analysis of rotational spectra of both the chromone monomer and its monohydrate through Fourier transform microwave spectroscopy. The observation of nine mono-substituted 13C isotopologues facilitated a semi-experimental determination of the equilibrium structure of the chromone monomer. In the case of chromone monohydrate, two distinct isomers were identified, each characterized by a combination of O–H⋯O and C–H⋯O hydrogen bonds involving the chromone's carbonyl group. This study further delved into intermolecular non-covalent interactions, employing different theoretical approaches. The relative population ratio of the two identified isomers was estimated to be about 2:1 within the supersonic jet. [ABSTRACT FROM AUTHOR]

1,3-difluoropropane and its complex with water were characterized by using Fourier transform microwave spectroscopy with the aid of quantum chemical calculations. Rotational spectra of the monomer were extended to the 13C isotopologues which lead to a precise structural determination of the two observed conformers. For the 1,3-difluoropropane-water complex, the most stable isomer has been observed and assigned in the supersonic jet expansion. In the observed isomer, water acts as a proton donor and a proton acceptor forming one O–H⋯F weak hydrogen bond and two C–H⋯O weak hydrogen bonds, respectively. The measurements on the three 13C, 18O, and deuterated water allowed determination of the skeleton structure and evaluation of the weak hydrogen bond parameters. Quantum theory of atoms in molecules, non-covalent interaction, and symmetry-adapted perturbation theory analyses were performed to reveal the nature of the intermolecular non-covalent interactions. [ABSTRACT FROM AUTHOR]

The rotational spectrum of the chloropentafluoroethane-water complex has been investigated by pulsed jet Fourier transform microwave spectroscopy. Experimental rotational and quadrupole coupling constants of five isotopologues imply that the two subunits are held together by an almost linear C–Cl⋯O halogen bond. Water lies effectively in the symmetric plane of C2F5Cl and undergoes a plausible free internal rotation. The experimental structure and dissociation energies of the complex are also deduced. [ABSTRACT FROM AUTHOR]

Uranium (U) ion contamination in aquatic systems has received considerable attention worldwide. In this paper, an adsorption material was synthesized with a Fe/Ca-based phosphate (CFB-PM) by a sol–gel method. The effect of pH, reaction time and initial concentration of U ions on its capacity to remove U ions from aqueous solution was investigated via static batch experiments. Comparative studies of U ion removal by CFB-PM with four sorbents, namely: nano zero-valent iron (nZVI), hydroxyapatite (HAP), hydroxyapatite-loaded nano zero-valent iron (HAP@nZVI) and high basicity steel slag-loaded hydroxyapatite (HBSS@HAP), were performed. Results showed that U ion adsorption capacity of CFB-PM was better than that of all four. The adsorption capacity showed a decreasing order as: CFB-PM (643.34 mg g–1) > HAP (549.86 mg g–1) > HBSS@HAP (321.82 mg g–1) > HAP@nZVI (153.62 mg g–1) > nZVI (102.65 mg g–1). Scanning electron microscopy energy-dispersive spectrometry examination suggested that the adsorbed U ions were mainly in the form of spheres, sheets or petals on the surfaces of CFB-PM. X-ray diffraction revealed several U-bearing mineral phases (i.e. Ca(UO2)2(PO4)2·3H2O, HPUO6·4H2O and (UO2)3PO4·4H2O). The U ion adsorption behaviours were further explored by Fourier transform IR spectroscopy. The U ion adsorption process of CFB-PM could be well described by a quasi-second-order adsorption kinetics model and the Langmuir adsorption isotherm model. The separation coefficient (RL) was close to zero, indicating that U ion adsorption was dominated by single-layer chemisorption. The findings reported in this study have implications for applying the synthesized material for remediation of U ion-contaminated groundwater. [ABSTRACT FROM AUTHOR]

The rotational spectrum of 2,2,2-trifluoroacetophenone has been measured and assigned by supersonic-jet Fourier transform microwave spectroscopy in the 2.0–20.0 GHz region. The measurement has been also extended to all its mono- 13 C substituted species, from which the accurate structural parameters for the carbon skeleton have been determined. [ABSTRACT FROM AUTHOR]

[Display omitted] • The rotational spectrum of anisole-CO 2 was analyzed. • The complex is characterized by a dominant C···O tetrel bond and two secondary C H ∙∙∙O weak hydrogen bonds. • The network of the cooperative non-covalent interactions in the anisole-CO 2 complex is revealed. Rotational spectrum of the 1:1 anisole-CO 2 complex has been investigated using a pulsed jet Fourier transform microwave spectrometer supplemented with quantum chemical calculations. In the pulsed jet, only one isomer has been observed which is characterized by a dominant C···O tetrel bond and two C H···O CO2 weak hydrogen bonds. Different theoretical methods predict different orders of relative energies of plausible conformations. The experimental observation is most consistent with the theoretical estimation at the B3LYP-D3(BJ)/6–311++G(d,p) level of theory. Johnson's non-covalent interaction, quantum theory of atoms in molecules and natural bond orbital analyses have been applied to better understand the nature of non-covalent interactions at play in the anisole-CO 2 complex. [ABSTRACT FROM AUTHOR]

The structure and non-covalent bonding features of the complex of thiazole and water were studied by using supersonic jet Fourier transform microwave spectroscopy and theoretical calculations. One isomer was observed which corresponds to the global minimum of the complex predicted theoretically. The rotational spectra of 9 additional isotopologues, including 5 mono-substituted heavy atoms of thiazole (34S, 13C and 15N), and 4 water isotopic species (H 2 18O, DOH, HOD and D 2 O), were also measured and analyzed. The experimental spectroscopic parameters were used to determine the structural parameters of the observed isomer. Theoretical analyses based on quantum theory of atoms in molecules and natural bond orbital revealed that the two moieties are linked by a N···H—O hydrogen bond. The total interaction energy of the complex is calculated to be −25.1 kJmol−1 with electrostatics being the major term according to energy decomposition analysis. The structural and energetic properties of thiazole-water complex have been characterized by microwave spectroscopy with theoretical calculations. Unlabelled Image • The thiazole-water complex were characterized with rotational spectroscopy and quantum chemical calculations. • The structure of the thiazole-water complex was precisely determined. • The nature of non-bonding interaction within the complex was revealed by NCI and SAPT analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two isomers of the 2-(trifluoromethyl)acrylic acid–water complex are observed by rotational spectroscopy complemented by quantum chemical calculations. • The structures, populations, and non-covalent interactions of the two isomers are determined. • The fluorination effect is proved to only enhance the energy of O-H···O w hydrogen bond by compared the energies of the corresponding hydrogen bonds formed in similar complexes. This study explores the effects of the −CF 3 group on non-covalent interactions through a comprehensive rotational investigation of the 2-(trifluoromethyl)acrylic acid–water complex. Employing Fourier transform microwave spectroscopy complemented by quantum chemical calculations, two isomers, i.e., s-cis and s-trans structures, have been observed in the pulsed jet. Based on relative intensity measurements, the s-cis to the s-trans population ratio was experimentally estimated to be ∼ 1:1.2. Subsequently, a comparison of the non-covalent interactions was carried out between the three similar complexes, acrylic acid–water, methacrylic acid–water, and 2-(trifluoromethyl)acrylic acid–water, offering quantitative insights into fluorination affecting the strength of the formed hydrogen bonds important, e.g., in molecular recognition. [ABSTRACT FROM AUTHOR]