Rotationally resolved electronic spectroscopy of water clusters of 7-azaindole

Abstract

Electronically excited states of water clusters of 7-azaindole: Structures, relative energies, and electronic nature of the excited states J. Chem. Phys. 128, 214310 (2008) The rotationally resolved electronic spectra of the electronic origin of the 7-azaindole-͑H 2 O͒ 1 and of the 7-azaindole-͑H 2 O͒ 2 clusters have been measured in a molecular beam. From the rotational constants the structures in the S 0 and S 1 electronic states were determined as cyclic with the pyrrolo NH and the pyridino N atoms being bridged by one and two water molecules, respectively. Excited state lifetimes of about 10 ns for both clusters have been found. In the spectrum of the 7-azaindole-͑H 2 O͒ 2 cluster a splitting of the rovibronic band is observed, which can be traced back to a large amplitude motion, involving the out-of-plane hydrogen atoms of the water chain. Both the changes of the rotational constants upon electronic excitation and the orientation of the transition dipole point to a solvent induced state reversal between the L a and the L b states upon microsolvation.

Electronically excited states of water clusters of 7-azaindole: Structures, relative energies, and electronic nature of the excited states

“…15 The present publication attempts to explain the experimental findings in a parallel experimental study on the excited states of the n = 1 and 2 water clusters of 7-azaindole. These results are presented in the accompanying study by Vu et al 16…”

“…The values in parentheses give the experimentally determined rotational constants from Ref 13. for the monomer and from Ref 16. for the n = 1 and 2 water clusters.…”

Rotationally resolved electronic spectroscopy of 3-cyanoindole and the 3-cyanoindole–water complex

“…Some molecular systems change the energetic order of the excited states already upon addition of the first water molecules to the chromophore like azaindole. 3 Indole, as the chromophore of the aromatic amino acid tryptophane, has been extensively studied, mainly regarding the location of the higher electronically excited 1 L a state relative to the lowest 1 L b state, both experimentally [4][5][6][7][8][9][10][11][12] as well as theoretically. [13][14][15][16][17][18] Exchange of one hydrogen atom in the chromophore for the highly polar cyano group, changes the fluorescence properties of the indole chromophore considerably.…”

“…It could be shown that the lowest excited singlet state has 1 L b character, while the excitation in the n = 1 and n = 2 water clusters is to the 1 L a state. 3 Ahn et al 26 investigated 3-cyanoindole and several 3-cyanoindolewater clusters, using mass-selected resonant two-photon ionization (R2PI) and UV-UV hole-burning (UVHB) spectroscopy. Assignments of the different cluster structures were made on the basis of a Franck-Condon analysis of the vibronic spectra.…”

Polymorphism, Hydrogen Bond Properties, and Vibrational Structure of 1H-Pyrrolo[3,2-h]Quinoline Dimers

“…A well-known example is 7-azaindole (7AI, Figure 1), which forms doubly hydrogen bonded dimers in solution [2], while the X-ray data reveal a tetrameric structure in the crystalline state [3]. Different stoichiometries and structures are possible for the complexes of 7AI with methanol and water: 1 : 1, 1 : 2, and 1 : 3 species have been detected [4][5][6][7][8][9].…”