The study of secondary effects in vibrational and hydrogen bonding properties of 2- and 3-ethynylpyridine and ethynylbenzene by IR spectroscopy (original) (raw)
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2-Ethynylpyridine dimers: IR spectroscopic and computational study
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2018
2-ethynylpyridine (2-EP) presents a multifunctional system capable of participation in hydrogen-bonded complexes utilizing hydrogen bond donating (CH, Aryl-H) and hydrogen bond accepting functions (N-atom, CC and pyridine π-systems). In this work, IR spectroscopy and theoretical calculations are used to study possible 2-EP dimer structures as well as their distribution in an inert solvent such as tetrachloroethene. Experimentally, the CH stretching vibration of the 2-EP monomer absorbs close to 3300 cm, whereas a broad band with maximum around 3215 cm emerges as the concentration rises, indicating the formation of hydrogen-bonded complexes involving the CH moiety. The CC stretching vibration of monomer 2-EP close to 2120 cm is, using derivative spectroscopy, resolved from the signals of the dimer complexes with maximum around 2112 cm. Quantum chemical calculations using the B3LYP + D3 model with counterpoise correction predict that the two most stable dimers are of the π-stacked var...
The exploration of hydrogen bonding properties of 2,6- and 3,5-diethynylpyridine by IR spectroscopy
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2014
Hydrogen bonding properties of 2,6- and 3,5-diethynylpyridine were analyzed by exploring of their interactions with trimethylphosphate, as hydrogen bond acceptor, or phenol, as hydrogen bond donor, in tetrachloroethene C2Cl4. The employment of IR spectroscopy enabled unravelling of their interaction pattern as well as the determination of their association constants (Kc) and standard reaction enthalpies (ΔrH(⦵)). The association of diethynylpyridines with trimethylphosphate in stoichiometry 1:1 is established through CH⋯O hydrogen bond, accompanied by the secondary interaction between CC moiety and CH3 group of trimethylphosphate. In the complexes with phenol, along with the expected OH⋯N interaction, CC⋯HO interaction is revealed. In contrast to 2,6-diethynylpyridine where the spatial arrangement of hydrogen bond accepting groups enables the simultaneous involvement of phenol OH group in both OH⋯N and OH⋯CC hydrogen bond, in the complex between phenol and 3,5-diethynylpyridine this...
Acta Crystallographica Section E Crystallographic Communications
In 2-amino-4-(4-bromophenyl)-6-oxo-1-phenyl-1,4,5,6-tetrahydropyridine-3-carbonitrile hemihydrate, C18H14BrN3O·0.5H2O, (I), pairs of molecules are linked by pairs of N—H...N hydrogen bonds, forming dimers with an R 2 2(12) ring motif. The dimers are connected by N—H...Br and O—H...O hydrogen bonds, and C—Br...π interactions, forming layers parallel to the (010) plane. 1,6-Diamino-2-oxo-4-phenyl-1,2-dihydropyridine-3,5-dicarbonitrile, C13H9N5O, (II), crystallizes in the triclinic space group P\overline{1} with two independent molecules (IIA and IIB) in the asymmetric unit. In the crystal of (II), molecules IIA and IIB are linked by intermolecular N—H...N and N—H...O hydrogen bonds into layers parallel to (001). These layers are connected along the c-axis direction by weak C—H...N contacts. C—H...π and C—N...π interactions connect adjacent molecules, forming chains along the a-axis direction. In (I) and (II), the stability of the packing is ensured by van der Waals interactions betwee...
The Magnitude of [C−H···O] Hydrogen Bonding in Molecular and Supramolecular Assemblies
Journal of the American Chemical Society, 2001
Ab initio calculations at the MP2/6-311++G** level on model systems (N-methylpyridinium complexes of dimethyl ether and dimethyl phosphate anion) provide quantitative measures of the large stabilization energies that arise from [C-H‚‚‚O] contacts in charged systems. These attractive interactions control (i) the self-assembly of bipyridinium-based catenanes and rotaxanes in solution, (ii) the self-organization of left-handed Z-DNA with alternating [dC-dG] sequences in the solid state, and (iii) the binding of pyridinium derivatives with single-and double-stranded DNA. Slightly attractive interactions occur between the donor ether and phosphate moieties and a neutral pyridine molecule in the gas phase. Electrostatic potential and solvation calculations demonstrate that [C-H‚‚‚O] interactions which involve a cationic [C-H] donor are dominated by electrostatic terms.
Geometrical Features of Hydrogen Bonded Complexes Involving Sterically Hindered Pyridines
The Journal of Physical Chemistry A, 2006
The ability of strongly sterically hindered pyridines to form hydrogen bonded complexes was inspected using low-temperature 1 H and 15 N NMR spectroscopy in a liquefied Freon mixture. The proton acceptors were 2,6-di(tert-butyl)-4-methyl-and 2,6-di(tert-butyl)-4-diethylaminopyridine; the proton donors were hydrogen tetrafluoroborate, hydrogen chloride, and hydrogen fluoride. The presence of the tert-butyl groups in the ortho positions dramatically perturbed the geometry of the forming hydrogen bonds. As revealed by experiment, the studied crowded pyridines could form hydrogen bonded complexes with proton donors exclusively through their protonation. Even the strongest small proton acceptor, anion F-, could not be received by the protonated base. Instead, the simplest hydrogen bonded complex involved the [FHF]anion. This complex was characterized by the shortest possible N‚‚‚F distance of about 2.8 Å. Because the ortho tert-butyl groups did not prevent the hydrogen bond interaction between the protonated center and the anion completely, an increase of the pyridine basicity caused a further shortening of the N-H distance and a weakening of the hydrogen bond to the counterion. * To whom correspondence should be addressed. shender@ chemie.fu-berlin.de.
Hydrogen-Bonding Fingerprints in Electronic States of Two-Dimensional Supramolecular Assemblies
ChemPhysChem, 2009
During the last years, the transfer and adaptation of the concepts of supramolecular chemistry to the formation of twodimensional (2D) supramolecular nanostructures on surfaces has become a particularly active area of research. A variety of one-dimensional (1D) and 2D hydrogen-bonded structures have been reported, ranging from homomolecular systems to binary assemblies on well characterized single-crystal surfaces. In particular, regular heteromolecular assemblies based upon hydrogen bonding have been successfully formed by coadsorption of molecular species exhibiting complementary functional amine/imide end-groups on nanostructured template substrates, such as vicinal Au surfaces. So far, most studies concerned the exploration and description of basic pattern formation using simple prototype building blocks. With the aim of achieving better control of the structures resulting from hydrogen-bond-driven self-assembly, recent efforts have been devoted to obtain a thorough understanding of all relevant physico-chemical interactions in these systems. A very important, but hitherto less addressed question is that of the impact of hydrogen bonding on the molecular electronic structure. A quantitative understanding of the energetics and electronics of different hydrogenbonding configurations will contribute to better control in the fabrication of specific supramolecular assemblies, and might ultimately allow the design of the electronic properties of hydrogen-bonded supramolecular architectures by engaging the building blocks in specific hydrogen-bonding configurations.
The Journal of Physical Chemistry A, 2004
The present work focuses on the influence of aromatic stacking on the ability of an aromatic nitrogen base to accept a hydrogen bond. Substituent effects were studied at the MP2 level for 10 complexes of a substituted benzene stacked with pyridine in a parallel offset conformation. The interaction energies between each substituted benzene and pyridine were analyzed in terms of Hartree-Fock, correlation, and electrostatic contributions. It appears that the basicity of pyridine is directly related to the electrostatic interaction between the cycles. It increases with increasing electron donating character of the benzene substituents. Also, density functional theory based descriptors such as global and local hardnesses and the benzene ring polarizability are found to adequately predict the interaction energy. These findings may be important in the study of DNA/ RNA chains.
Journal of Physical Chemistry A, 1999
The H-bond interaction of the cytosine model compound 2-hydroxypyridine and its tautomer 2-oxopyridine with HCl is investigated using the combined matrix-isolation FT-IR and theoretical density functional and ab initio methods. The theoretical calculations have been carried out at the B3-LYP/6-31++G** and RHF/6-31++G** levels of theory. Different types of hydrogen-bonding have been found: two closed complexes of the proton transfer type, each containing two hydrogen bonds, i.e., N + sH‚‚‚Cl-‚‚‚HsO and CdO + s H‚‚‚Cl-‚‚‚HsN; two open complexes of intermediate strength, N‚‚‚H-Cl and CdO‚‚‚H-Cl; and one weak complex, HsO‚‚‚HsCl. The theoretical results indicate that the closed H-bonded complexes are the most stable systems for both the hydroxy and the oxo tautomers. The increased stability of these complexes is due to a cooperative H-bonding effect. The experimental spectra are consistent with this prediction, but the weaker complexes are also identified. A comparison of the experimental and calculated IR frequencies demonstrates that the frequency shifts of the vibrational modes directly involved in the H-bond interactions, especially the X-H stretching modes, are better predicted by the DFT method than by the RHF method. For the other vibrational modes not directly involved in the H-bonds, the RHF methodology has a similar accuracy compared to the DFT method.