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Issue 12, 2011
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2,3-Bis(1-methylimidazol-2-yl)quinoxaline (bmiq), a new ligand with decoupled electron transfer and metal coordination sites: the very different redox behaviour of isoelectronic complexes with [PtCl2] and [AuCl2]+

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Abstract

The new, potentially ambidentate heterocyclic ligand 2,3-bis(1-methylimidazol-2-yl)quinoxaline (bmiq) was obtained from 2,3-bis(1-methylimidazol-2-yl)glyoxal and 1,2-diaminobenzene. Its coordination to PtCl2 and to the isoelectronic [AuCl2]+ in [AuCl2(bmiq)](AuCl4) occurs via the imine N donors of the imidazolyl groups, leading to the formation of seven-membered chelate rings with boat conformation. According to the spectroelectrochemistry (UV-vis-NIR, EPR), the reversible electron addition to the [PtCl2(bmiq)] and the free ligand takes place in the (non-coordinated) quinoxaline part of the molecule, similarly as for related complexes of dipyrido[3,2-a:2′,3′-c]phenazines (dppz), 2,3-bis(2-pyridyl)quinoxalines (bpq) and 2,3-bis(dialkylphosphino)quinoxalines (QuinoxP). DFT calculations confirm the experimental results (structures, spectroscopy) and also point to the coordination potential of the quinoxaline N atoms. The electron addition to [AuCl2(bmiq)]+ takes place not at the ligand but at the metal site, according to experimental and DFT results.

Graphical abstract: 2,3-Bis(1-methylimidazol-2-yl)quinoxaline (bmiq), a new ligand with decoupled electron transfer and metal coordination sites: the very different redox behaviour of isoelectronic complexes with [PtCl2] and [AuCl2]+

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Supplementary files

Article information


Submitted
24 Sep 2010
Accepted
09 Dec 2010
First published
07 Feb 2011

Dalton Trans., 2011,40, 2757-2763
Article type
Paper

2,3-Bis(1-methylimidazol-2-yl)quinoxaline (bmiq), a new ligand with decoupled electron transfer and metal coordination sites: the very different redox behaviour of isoelectronic complexes with [PtCl2] and [AuCl2]+

E. Bulak, T. Varnali, B. Schwederski, B. Sarkar, I. Hartenbach, J. Fiedler and W. Kaim, Dalton Trans., 2011, 40, 2757
DOI: 10.1039/C0DT01282C

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