Conformational analysis by laser spectroscopy in the gas phase: p-methoxyphenethylamine (a neurotransmitter)

Yi, John T.; Robertson, Evan G.; Pratt, David W.

doi:10.1039/b206864h

Cited by 17 publications

(37 citation statements)

References 12 publications

(21 reference statements)

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“…Similarly, all conformers exhibit similar values of ÁA, ÁB, and ÁC, indicating that the structural changes upon excitation mainly occur in the indole ring system. These results stand in sharp contrast to those for MPEA, where it was found that the S 1 -S 0 TM orientations and rotational constant differences are quite different among the different conformers [11].…”

Section: Discussioncontrasting

confidence: 75%

“…Therefore, we conclude that the N-H-p (py) interaction is responsible for the stability of conformers GPyout and GPyup in both the S 0 and S 1 states. This effect is analogous to the findings in MPEA [11]. The stronger intensity of band A comes from an additional stabilizing interaction due to a weak intramolecular hydrogen bond between the lone pair of the nitrogen atom and the C hydrogen atom (cf.…”

Section: Discussionsupporting

confidence: 65%

“…Similar techniques were recently applied to assign the seven origin bands in an analogous molecule, p-methoxyphenethylamineu (MPEA), which also has an ethylamine side chain [11]. In TRA, seven conformers also have been unambiguously identified.…”

Section: Introductionmentioning

confidence: 93%

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Tryptamine in the gas phase. A high resolution laser study of the structural and dynamic properties of its ground and electronically excited states

Nguyen¹,

Korter²,

Pratt³

2005

Molecular Physics

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High resolution S 1 S 0 fluorescence excitation spectra of tryptamine have been observed in the collision-free environment of a supersonic molecular beam. Each origin band has been assigned to a unique conformer of the isolated molecule based on its observed rotational constants. For the first time, subbands have been detected in the rotationally resolved spectra of bands C blue and D. A possible hindered motion is proposed to account for the appearance of these subbands. This motion connects the minima associated with the Antipy and Antiph conformers, and thus explores new regions of the energy landscape of this important biomolecule.

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Section: Discussioncontrasting

confidence: 75%

Section: Discussionsupporting

confidence: 65%

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Tryptamine in the gas phase. A high resolution laser study of the structural and dynamic properties of its ground and electronically excited states

Nguyen¹,

Korter²,

Pratt³

2005

Molecular Physics

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“…The remaining conformer is a cis amide anti structure with the amide plane perpendicular to the ring plane, so that a 180°rotation of the O -CH 3 bond produces an equivalent structure. Furthermore, comparison with MPEA where gauche-trans and gauche-cis structures occur in pairs, with gauche-trans conformer origins appearing red of gauche-cis, 10 suggests an assignment of A to the gauche-trans structure, NMPEA-II, and B to the gauche-cis structure, NMPEA-I. All four of these conformers have a trans amide configuration and calculations predict an energetic preference of gauche over anti conformers, as was found for NPEA.…”

Section: B Nmpeamentioning

confidence: 56%

“…[1][2][3][4][5][6][7][8][9][10][11][12] By cooling the molecules in a supersonic expansion, ultraviolet transitions due to single conformers can often be resolved. One of the fruitful strategies used to study these molecules is to incorporate into the molecule an ultraviolet chromophore that can be readily detected using either laser-induced fluorescence or resonant two-photon ionization.…”

Section: Introductionmentioning

confidence: 99%

Entropy-driven population distributions in a prototypical molecule with two flexible side chains: O-(2-acetamidoethyl)-N-acetyltyramine

Shubert

Baquero

Clarkson

et al. 2007

The Journal of Chemical Physics

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Resonant two-photon ionization (R2PI), resonant ion-dip infrared (RIDIR), and UV-UV hole-burning spectroscopies have been employed to obtain conformation-specific infrared and ultraviolet spectra under supersonic expansion conditions for O-(2-acetamidoethyl)-N-acetyltyramine (OANAT), a doubly substituted aromatic in which amide-containing alkyl and alkoxy side chains are located in para positions on a phenyl ring. For comparison, three single-chain analogs were also studied: (i) N-phenethyl-acetamide (NPEA), (ii) N-(p-methoxyphenethyl-acetamide) (NMPEA), and (iii) N-(2-phenoxyethyl)-acetamide (NPOEA). Six conformations of OANAT have been resolved, with S(0)-S(1) origins ranging from 34,536 to 35,711 cm(-1), denoted A-F, respectively. RIDIR spectra show that conformers A-C each possess an intense, broadened amide NH stretch fundamental shifted below 3400 cm(-1), indicative of the presence of an interchain H bond, while conformers D-F have both amide NH stretch fundamentals in the 3480-3495 cm(-1) region, consistent with independent-chain structures with two free NH groups. NPEA has a single conformer with S(0)-S(1) origin at 37,618 cm(-1). NMPEA has three conformers, two that dominate the R2P1 spectrum, with origin transitions between 35,580 and 35,632 cm(-1). Four conformations, one dominate and three minor, of NPOEA have been resolved with origins between 35,654 and 36,423 cm(-1). To aid the making of conformational assignments, the geometries of low-lying structures of all four molecules have been optimized and the associated harmonic vibrational frequencies calculated using density functional theory (DFT) and RIMP2 methods. The S(0)-S(1) adiabatic excitation energies have been calculated using the RICC2 method and vertical excitation energies using single-point time-dependent DFT. The sensitivity of the S(0)-S(1) energy separation in OANAT and NPOEA primarily arises from different orientations of the chain attached to the phenoxy group. Using the results of the single-chain analogs, tentative assignments have been made for the observed conformers of OANAT. The RIMP2 calculations predict that interchain H-bonded conformers of OANAT are 25-30 kJ/mol more stable than the extended-chain structures. However, the free energies of the interchain H-bonded and extended structures calculated at the preexpansion temperature (450 K) differ by less than 10 kJ/mol, and the number of extended structures far outweighs the number of H-bonded conformers. This entropy-driven effect explains the presence of the independent-chain conformers in the expansion, and cautions future studies that rely solely on relative energies of conformers in considering possible assignments.

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New Techniques in Microwave Spectroscopy

Shipman¹,

Pate²

2011

Handbook of High‐resolution Spectroscopy

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We discuss the design principles and performance of a true broadband chirped‐pulse Fourier transform microwave spectrometer capable of operation from 800 MHz to 18.5 GHz. This spectrometer utilizes recent advances in high‐speed digital electronics to both directly generate linear frequency sweeps spanning more than 10 GHz and to directly digitize the molecular free induction decay (FID). Signal averaging is performed in the time domain to improve the signal‐to‐noise ratio. This spectrometer has a number of capabilities that are well suited for studies on large‐molecule systems, including the ability to perform multiplexed Stark effect measurements and selective‐excitation microwave double‐resonance measurements. These characteristics are demonstrated using the molecule 1,2,2,2‐tetrafluoroethyl difluoromethyl ether (C 3 H 2 F 6 O, molecular weight 168 g mol −1 , also known by its trade names of suprane or desflurane ) as an example. The simultaneous use of multiple‐pulsed nozzles as well as the acquisition of multiple FIDs per valve pulse is also demonstrated in the context of strategies for increasing spectrometer sensitivity by 2 orders of magnitude.

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Conformational analysis by laser spectroscopy in the gas phase: p-methoxyphenethylamine (a neurotransmitter)

Cited by 17 publications

References 12 publications

Tryptamine in the gas phase. A high resolution laser study of the structural and dynamic properties of its ground and electronically excited states

Tryptamine in the gas phase. A high resolution laser study of the structural and dynamic properties of its ground and electronically excited states

Entropy-driven population distributions in a prototypical molecule with two flexible side chains: O-(2-acetamidoethyl)-N-acetyltyramine

New Techniques in Microwave Spectroscopy

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