Jump to main content
Jump to site search

Issue 8, 2010
Previous Article Next Article

Excited state intramolecular proton transfer (ESIPT) in six-coordinated zinc(II)-quinoxaline complexes with ligand hydrogen bonds: their fluorescent properties sensitive to axial positions

Author affiliations

Abstract

Zinc(II)-quinoxaline complexes, [Zn(hqxc)2(py)2] and [Zn(hqxc)2(DMSO)2] (hqxc = 3-hydroxy-2-quinoxalinecarboxylate, py = pyridine, DMSO = dimethyl sulfoxide), were prepared and characterized by X-ray crystallography and fluorescence spectroscopy. In both complexes, the zinc ion is six-coordinated by two equatorial bidentate hqxc ligands with an intramolecular hydrogen bond and two axial monodentate ligands such as pyridine or DMSO. In spite of similar coordination geometries, there is a remarkable difference between their solid-state fluorescent properties. The pyridine complex is strongly fluorescent (fluorescence quantum yield Φ = 0.22), giving rise to a significantly Stokes-shifted spectrum. From its thin film photopumped by a nitrogen gas laser, amplified spontaneous emission was observed. These results suggest that the fluorescence occurs by way of excited-state intramolecular proton-transfer (ESIPT) in the hydrogen bond of hqxc. On the other hand, the DMSO complex shows fluorescent intensity (Φ = 0.08) lower than that of the pyridine complex, and shows normal emission in addition to ESIPT emission. From IR measurements for these complexes, it is concluded that axial ligands influence the hydrogen bond strength of the equatorial hqxc ligand via zinc and thus the ESIPT efficiency.

Graphical abstract: Excited state intramolecular proton transfer (ESIPT) in six-coordinated zinc(ii)-quinoxaline complexes with ligand hydrogen bonds: their fluorescent properties sensitive to axial positions

Back to tab navigation

Supplementary files

Publication details

The article was received on 21 Sep 2009, accepted on 20 Nov 2009 and first published on 05 Jan 2010


Article type: Paper
DOI: 10.1039/B919613G
Citation: Dalton Trans., 2010,39, 1989-1995
  •   Request permissions

    Excited state intramolecular proton transfer (ESIPT) in six-coordinated zinc(II)-quinoxaline complexes with ligand hydrogen bonds: their fluorescent properties sensitive to axial positions

    K. Sakai, S. Takahashi, A. Kobayashi, T. Akutagawa, T. Nakamura, M. Dosen, M. Kato and U. Nagashima, Dalton Trans., 2010, 39, 1989
    DOI: 10.1039/B919613G

Search articles by author

Spotlight

Advertisements