Tri Nguyen

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

High resolution S1←S0 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 Cblue 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.

Permanent electric dipole moments of four tryptamine conformers in the gas phase: A new diagnostic of structure and dynamics

Rotationally resolved electronic spectroscopy in the gas phase, in the absence and presence of an applied electric field, has been used to determine the charge distribution of a cross section of the energy landscape of tryptamine (TRA). We report the magnitude and direction of the permanent electric dipole moments of the four TRA conformers GPyout, GPyup, GPhup, and Antiup in their S0 and S1 electronic states. Each dipole moment is unique, providing a powerful new tool for the conformational analysis of biomolecules in the gas phase. A comparison of the results for the different conformers of TRA reveals that the position and orientation of the ethylamine side chain play a major role in determining both the permanent and induced electric dipole moments of the different species in both electronic states.

Rotationally resolved electronic spectroscopy of some divinylbenzenes in the gas phase. Platt’s rule revisited

Abstract Platt’s rule, as interpreted by Heilbronner and Murrell, states that “if a (an aromatic) molecule has a twofold symmetry axis passing through an atom, then (electronic) transitions to a states are polarized parallel to that axis, and transitions to b states at right angles to this”. We have observed and assigned the fully resolved electronic spectra of three divinylbenzenes, and used this rule to assign the character of their lowest excited electronic states in cases where the molecule has an in-plane C2 axis.

On the energy landscapes of 3-indole acetic acid and 3-indole propionic acid. A study of side chain flexibilities in their S0 and S1 electronic states

The tandem of 3-indole acetic acid (IAA) and 3-indole propionic acid (IPA) is ideally suited for a detailed study of the intramolecular forces responsible for the conformational properties of species containing side chains. Toward this end, high resolution S(1)<-- S(0) excitation spectra of the three origin bands in IAA and the two origin bands in IPA were recorded and analyzed. Each origin is assigned to a unique conformer. A discussion of the resulting energy landscape is given.