Intramolecular hydrogen bonds and conformational properties of biogenic amines: A free-jet microwave study of tyramine
17 May 2004-Physical Chemistry Chemical Physics (The Royal Society of Chemistry)-Vol. 6, Iss: 10, pp 2863-2866
TL;DR: In this paper, the conformational properties of tyramine, an important biologically active molecule, were studied by free jet microwave absorption spectroscopy aided by quantum chemical calculations, and structural assignments were made on the basis of ab initio predicted spectral properties calculated at the MP2/6-31G* level of theory.
Abstract: The conformational properties of tyramine, an important biologically active molecule, were studied by free jet microwave absorption spectroscopy aided by quantum chemical calculations. Structural assignments were made on the basis of ab initio predicted spectral properties calculated at the MP2/6-31G* level of theory in the minima found in the conformational hypersurface and four conformational species were detected in the jet expansion. The most stable conformers are the folded ones in which the amino hydrogen atoms interact with the aromatic π cloud showing that the conformational properties of tyramine are mainly determined by non-bonding interactions.
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TL;DR: The present review surveys the in-solution competition of the conformations with intramolecular vs. intermolecular hydrogen bonds for different types of small organic molecules and considers the solvent effects on the stability of simple dimeric systems as revealed from molecular dynamics simulations or on the basis of the calculated potential of mean force curves.
Abstract: A hydrogen bond for a local-minimum-energy structure can be identified according to the definition of the International Union of Pure and Applied Chemistry (IUPAC recommendation 2011) or by finding a special bond critical point on the density map of the structure in the framework of the atoms-in-molecules theory. Nonetheless, a given structural conformation may be simply favored by electrostatic interactions. The present review surveys the in-solution competition of the conformations with intramolecular vs. intermolecular hydrogen bonds for different types of small organic molecules. In their most stable gas-phase structure, an intramolecular hydrogen bond is possible. In a protic solution, the intramolecular hydrogen bond may disrupt in favor of two solute-solvent intermolecular hydrogen bonds. The balance of the increased internal energy and the stabilizing effect of the solute-solvent interactions regulates the new conformer composition in the liquid phase. The review additionally considers the solvent effects on the stability of simple dimeric systems as revealed from molecular dynamics simulations or on the basis of the calculated potential of mean force curves. Finally, studies of the solvent effects on the type of the intermolecular hydrogen bond (neutral or ionic) in acid-base complexes have been surveyed.
116 citations
Cites methods from "Intramolecular hydrogen bonds and c..."
...Indeed, MP2/6-31G* calculations by Melandri and Maris above, where the dispersion interactions are considered, clearly indicate the gauche preference....
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...For tyramine, the gas-phase conformations were determined by Melandri and Maris [203] using a free-jet microwave study....
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TL;DR: This paper analyses several examples of molecular adducts bound by weak hydrogen bonds formed in free jet expansions and recently characterized by rotational spectroscopy to highlight that weak hydrogen Bonds are extremely important in chiral recognition phenomena and as driving forces of the conformational landscape of important biomolecules.
Abstract: Recently reported rotational spectroscopic studies on small dimers and oligomers bound by weak hydrogen bonds show that the driving forces, the spatial arrangement and the dynamical features displayed are very different from those involved in stronger and conventional hydrogen bonds. The very small binding energies (similar to those of van der Waals interactions) imply that the stabilization of the dimer is often obtained by networks of weak hydrogen bonds. Even in the presence of multiple bonds the partner molecules show a high degree of internal freedom within the complex. This paper analyses several examples of molecular adducts bound by weak hydrogen bonds formed in free jet expansions and recently characterized by rotational spectroscopy. They include weakly bound complexes of weak donors with strong acceptors (C–H⋯O,N, S–H⋯O,N), strong donors (O–H, N–H) with weak acceptors such as the halogen atoms and π systems but also the elusive interactions between weak donors and weak acceptors (C–H⋯π and C–H⋯halogen). Examples are also given where rotational spectroscopy highlights that weak hydrogen bonds are extremely important in chiral recognition phenomena and as driving forces of the conformational landscape of important biomolecules.
63 citations
TL;DR: The proposed HS-SPME-MIR-IMS method can be successfully used in biogenic amines analysis in water and food samples by ion mobility spectrometry (IMS), results indicate.
38 citations
TL;DR: The rotational spectrum of neutral dopamine has been investigated for the first time using a combination of Fourier transform microwave spectroscopy with laser ablation and the parameters extracted from the analysis of the spectrum unequivocally identify the existence of seven conformers of dopamine.
Abstract: The rotational spectrum of neutral dopamine has been investigated for the first time using a combination of Fourier transform microwave spectroscopy with laser ablation. The parameters extracted from the analysis of the spectrum unequivocally identify the existence of seven conformers of dopamine. (14)N nuclear quadrupole coupling interactions have been used to determine the orientation of the amino group probing the existence of stabilizing N-H···π interactions for all observed conformers.
38 citations
TL;DR: Tautomeric equilibria have been studied for five-member N-heterocycles and their methyl derivatives in the gas phase and in different solvents with dielectric constants of epsilon = 4.7-78.4 and using the FEP/MC method, one observes that the preferred tautomers differ in several cases from those predicted by the continuum solvent model.
Abstract: Tautomeric equilibria have been studied for five-member N-heterocycles and their methyl derivatives in the gas phase and in different solvents with dielectric constants of e = 4.7−78.4. The free en...
33 citations
References
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TL;DR: In this paper, a free jet millimeter wave spectrometer has been modified in order to observe the rotational spectra of van der Waals molecular complexes in the 60-78 GHz frequency range.
134 citations
TL;DR: In this article, a mass-selected R2PI excitation spectra of the S 1 − S 0 electronic transitions in 2phenylethyl alcohol and 2-phenylethylamine has been recorded in a jet-cooled environment.
Abstract: Laser-induced fluorescence and one- and two-color, mass- selected R2PI excitation spectra of the S1 ← S0 electronic transitions in 2-phenylethyl alcohol and 2-phenylethylamine have been recorded in a jet-cooled environment. Five conformers of 2-phenylethyl alcohol and four of 2-phenylethylamine have been identified, together with a number of 1:1 hydrated water clusters. The fifth origin band in the excitation spectrum of 2-phenylethylamine has been reassigned to a water cluster, primarily on the basis of its ion fragmentation pattern. Analysis of their partially resolved rotational band contours has been aided by ab initio molecular orbital calculations, conducted at levels of theory ranging from MP2/3-21G* to MP2/6-311G** for the ground state and CIS/6-311G** for the first electronically excited singlet state. The reliability of the CIS method has also been tested through benchmark calculations, including computations on a related, experimentally known conformational system, methyl 3-hydroxybenzoate. 2-P...
115 citations
TL;DR: In this paper, the observed relative abundances of the several different tautomers and conformers observed in the millimeter-wave jet spectroscopy of histamine were analyzed.
Abstract: It has been found possible to understand the observed relative abundances of the several different tautomers and conformers observed in the millimeter-wave jet spectroscopy of histamine by using ab...
113 citations
71 citations
TL;DR: In this paper, the excitation spectrum of PEA exhibits a group of five transition bands in the S1 ← region, which appear repetitively with the same spectral separations and intensity pattern in the higher energy regions up to 1000 cm-1 above the origin.
Abstract: The neurotransmitter molecule phenethylamine (PEA) is studied by fluorescence excitation, mass-resolved excitation, hole burning, and dispersed emission spectroscopies. The excitation spectrum of PEA exhibits a group of five transition bands in the S1 ← region. This group of transitions appears repetitively with the same spectral separations and intensity pattern in the higher energy regions up to 1000 cm-1 above the origin. The hole burning spectra of these five bands show different independent spectral hole depletion features. With the observation of no blue shifted emission bands higher than the excitation energy in the dispersed emission spectra, these five transition bands can be assigned to five different molecular conformers of PEA. These molecular conformers are distinguished from each other in their alkylamine side chain conformations and the amino group spatial orientations. With the assistance of ab initio calculations, we are able to identify the conformations of these five isomers. The effect...
70 citations