Issue 25, 2007

Fluorescence quenching in cyclic hydrogen-bonded complexes of 1H-pyrrolo[3,2-h]quinoline with methanol: cluster size effect

Abstract

Laser induced fluorescence (LIF) excitation spectra of molecular complexes of 1H-pyrrolo[3,2-h]quinoline (PQ) with methanol (n = 1, 2, 3) as well as vibrational spectra of their electronic ground state are reported. The latter have been recorded in the mid-infrared region by fluorescence depletion (FDIR). The only PQ·methanoln complex clearly identified in the LIF spectrum is the triply hydrogen-bonded cyclic 1 ∶ 2 aggregate. Its stoichiometry has been proven by the femtosecond multiphoton ionization detected infrared measurements [J. Am. Chem. Soc., 2006, 128, 10 000]. The structure of the 1 ∶ 2 cluster is determined by means of FDIR spectroscopy in combination with ab initio and DFT calculations. No fluorescence was detected that could be attributed to the 1 ∶ 1 cluster. This behaviour of the 1 ∶ 1 complex is explained in terms of rapid excited state double proton transfer followed by a non-radiative relaxation. The n = 3 and heavier clusters are fluorescent. Their electronic spectra overlap, preventing the selective measurement of the FDIR spectra of individual complexes.

Graphical abstract: Fluorescence quenching in cyclic hydrogen-bonded complexes of 1H-pyrrolo[3,2-h]quinoline with methanol: cluster size effect

Supplementary files

Article information

Article type
Paper
Submitted
15 Mar 2007
Accepted
24 Apr 2007
First published
16 May 2007

Phys. Chem. Chem. Phys., 2007,9, 3276-3285

Fluorescence quenching in cyclic hydrogen-bonded complexes of 1H-pyrrolo[3,2-h]quinoline with methanol: cluster size effect

Y. Nosenko, A. Kyrychenko, R. P. Thummel, J. Waluk, B. Brutschy and J. Herbich, Phys. Chem. Chem. Phys., 2007, 9, 3276 DOI: 10.1039/B703908E

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