The Effect of Intramolecular Hydrogen Bond Type on the Gas-Phase Deprotonation of ortho-Substituted Benzenesulfonic Acids. A Density Functional Theory Study

Structural factors have been identified that determine the gas-phase acidity of ortho-substituted benzenesulfonic acid, 2-XC6H4–SO3H, (X = –SO3H, –COOH, –NO2, –SO2F, –C≡N, –NH2, –CH3, –OCH3, –N(CH3)2, –OH). The DFT/B3LYP/cc-pVTZ method was used to perform conformational analysis and study the structural features of the molecular and deprotonated forms of these compounds. It has been shown that many of the conformers may contain anintramolecular hydrogen bond (IHB) between the sulfonic group and the substituent, and the sulfonic group can be an IHB donor or an acceptor. The Gibbs energies of gas-phase deprotonation ΔrG0298 (kJ mol–1) were calculated for all compounds. It has been set that in ortho-substituted benzenesulfonic acids, the formation of various types of IHB is possible, having a significant effect on the ΔrG0298 values of gas-phase deprotonation. If the –SO3H group is the IHB donor, then an ion without an IHB is formed upon deprotonation, and the deprotonation energy increases. If this group is an IHB acceptor, then a significant decrease in ΔrG0298 of gas-phase deprotonation is observed due to an increase in IHB strength and the A− anion additional stabilization. A proton donor ability comparative characteristic of the –SO3H group in the studied ortho-substituted benzenesulfonic acids is given, and the ΔrG0298 energies are compared with the corresponding values of ortho-substituted benzoic acids

Structural investigation of molecules in the vapour over beryllium dichloride using electron diffraction and mass spectrometric data

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Cyclic Dimers of 4-n-Propyloxybenzoic Acid with Hydrogen Bonds in the Gaseous State

A comprehensive study of saturated vapors of 4-n-propyloxybenzoic acid (POBA) by gas electron diffraction (GED) and mass spectrometric (MS) methods supplemented by quantum chemical (QC) calculations was carried out for the first time. An attempt was made to detect dimeric forms of the acid in the gaseous state. It has been established that at the temperature of GED experiment, vapor over a solid sample contains up to 20 mol.% of cyclic dimers with two O-H...O hydrogen bonds. The main geometrical parameters of gaseous monomers and dimers of POBA are obtained. The distance r(O…O) = 2.574(12) Å in the cyclic fragment of the gaseous dimer is close to that in the crystal structure (2.611 Å). In the mass spectrum of the POBA recorded the ions of low intensity with a mass exceeding the molecular mass of the monomer were detected. The presence of ions, whose elemental composition corresponds to the dissociative ionization of the dimer, confirms the results of the GED experiment on the presence of POBA dimers in the gas state. The results of GED studies of acetic acid, benzoic acid, and POBA were compared. It is shown that the COOH fragment saves its geometric structure in monomers, as well as the COOH...HOOC fragment with two hydrogen bonds in dimers of different acids. The intermolecular interaction energy in considered acid dimers was estimated using QC calculations (B97D/6-311++G **). The significant value of last (>84 kJ/mol) is the reason for the noticeable presence of dimers in the gas phase

Gas-phase structure and conformations of copper(II) 2,9,16,23-tetra-tert-butyl phthalocyanine

Pimenov OA, Giricheva NI, Blomeyer S, Mayzlish VE, Mitzel NW, Girichev GV. Gas-phase structure and conformations of copper(II) 2,9,16,23-tetra-tert-butyl phthalocyanine. Structural Chemistry. 2015;26(5-6):1531-1541.The molecular structure of copper(II) 2,9,16,23-tetra-tert-butyl phthalocyanine (Cu(pc (t) )) was investigated by gas-phase electron diffraction with mass spectrometric control of vapor composition. Two conformers of C (4h) symmetry and three conformers of C (s) symmetry are predicted by quantum chemical calculations using the hybrid DFT method UB3LYP with 6-31G* and cc-pVTZ basis sets. According to the relative energies at the temperature of GED experiments (436 A degrees C), the two C (4h) symmetric conformers occur in 1.1 and 2.3 % abundance in the gas phase. The highest mole fraction (66.6 %) and lowest R-factor (4.25 %) correspond to one of the C (s) symmetric conformers; however, the two C (4h) symmetric models cannot be disproved by the Hamilton R-factor ratio test. The GED structural data of the three models mentioned reliably confirm approximate local D (4h) symmetry of the phthalocyanine ligand core

Gas phase structures of potassium tetrakis(hexafluoroacetyl-ace-to-nato)-lanthanate(III) complexes [KLn(C5HF6O2)4] (Ln = La, Gd, Lu)

Girichev GV, Giricheva NI, Khochenkov AE, Sliznev VV, Belova NV, Mitzel NW. Gas phase structures of potassium tetrakis(hexafluoroacetyl-ace-to-nato)-lanthanate(III) complexes [KLn(C5HF6O2)4] (Ln = La, Gd, Lu). Chemistry - A European Journal. 2021;27(3):1103-1112.The molecular structures of potassium tetrakis(hexafluoro-acetylacetonato)lanthanate(III) complexes [KLn(hfa) 4 ] (Ln = La, Gd, Lu; hfa = C 5 HF 6 O 2 ,) were studied by synchronous gas-phase electron diffraction / mass spectrometry (GED/MS) supported by quantum-chemical (DFT/PBE0) calculations. The compounds sublimate congruently and the vapors contain single molecular species: the heterobinuclear complex [KLn(hfa) 4 ]. All molecules are of C 1 symmetry with the lanthanide atom in the center of a coordination polyhedron LnO 8 , while the potassium atom is coordinated by three ligands under formation of three K-O and three K-F bonds. Topological analysis of the electron density distributions confirms the existence of ionic-type K-O and K-F bonding. The presence of the potassium ion distorts the coordination polyhedron LnO 8 and takes influence on the structure of the ligands. The structures of the free [KLn(hfa) 4 ] molecules are compared with those of the related compounds [KDy(hfa) 4 ] and [KEr(hfa) 4 ] in their crystalline state. The complex nature of chemical bonding is discussed on the basis of electron density topology analyses. © 2020 Wiley-VCH GmbH

1,8-Bis(phenylethynyl)anthracene - gas and solid phase structures

Lamm J-H, Horstmann J, Stammler H-G, et al. 1,8-Bis(phenylethynyl)anthracene - gas and solid phase structures. Organic & Biomolecular Chemistry. 2015;13(33):8893-8905.1,8-Bis(phenylethynyl) anthracene (1,8-BPEA) was synthesized by a twofold Kumada cross-coupling reaction. The molecular structure of 1,8-BPEA was determined using a combination of gas-phase electron diffraction (GED), mass spectrometry (MS), quantum chemical calculations (QC) and single-crystal X-ray diffraction (XRD). Five rotamers of the molecule with different orientations of phenylethynyl groups were investigated by DFT calculations. According to these, molecules of C-2 symmetry with co-directional rotation of the phenylethynyl groups are predicted to exist in the gas phase at 498 K. This was confirmed by a GED/MS experiment at this temperature. The bonding of this conformer was studied and described in terms of an NBO-analysis. Dispersion interactions in the solid state structure and in the free molecule are discussed. In the solid this symmetry is broken; the asymmetric unit of the single crystal contains 3.5 molecules and a herringbone packing motif of pi-stacked dimers and trimers. The pi-stacking in the dimers is between the anthracene units, and the trimers are linked by pi-stacking between phenyl and anthracene units. The interaction between these stacks can be described in terms of sigma(C-H)center dot center dot center dot pi interactions

Gas-phase structure of 1,8-bis[(trimethylsilyl)ethynyl]anthracene: cog-wheel-type vs. independent internal rotation and influence of dispersion interactions

Otlyotov AA, Lamm J-H, Blomeyer S, et al. Gas-phase structure of 1,8-bis[(trimethylsilyl)ethynyl]anthracene: cog-wheel-type vs. independent internal rotation and influence of dispersion interactions. PHYSICAL CHEMISTRY CHEMICAL PHYSICS. 2017;19(20):13093-13100.The gas-phase structure of 1,8-bis[(trimethylsilyl) ethynyl]anthracene (1,8-BTMSA) was determined by a combined gas electron diffraction (GED)/mass spectrometry (MS) experiment as well as by quantum-chemical calculations (QC). DFT and dispersion corrected DFT calculations (DFT-D3) predicted two slightly different structures for 1,8-BTMSA concerning the mutual orientation of the two -C-C C-SiMe3 units: away from one another or both bent to the same side. An attempt was made to distinguish these structures by GED structural analysis. To probe the structural rigidity, a set of Born-Oppenheimer molecular dynamics (BOMD) calculations has been performed at the DFT-D level. Vibrational corrections Delta r = r(a) - r(e) were calculated by two BOMD approaches: a microcanonically (NVE) sampled ensemble of 20 trajectories (BOMD(NVE)) and a canonical (NVT) trajectory thermostated by the Noose-Hoover algorithm (BOMD(NVT)). In addition, the conventional approach with both, rectilinear and curvilinear approximations (SHRINK program), was also applied. Radial distribution curves obtained with models using both MD approaches provide a better description of the experimental data than those obtained using the rectilinear (SHRINK) approximation, while the curvilinear approach turned out to lead to physically inacceptable results. The electronic structure of 1,8-BTMSA was investigated in terms of an NBO analysis and was compared with that of the earlier studied 1,8-bis(phenylethynyl) anthracene. Theoretical and experimental results lead to the conclusion that the (trimethylsilyl) ethynyl (TMSE) groups in 1,8-BTMSA are neither restricted in rotation nor in bending at the temperature of the GED experiment