Issue 7, 2013
From the journal:

Dalton Transactions

Unexpected reversible pyrazine based methylation in a Ru(ii) complex bearing a pyrazin-2′-yl-1,2,4-triazolato ligand and its effect on acid/base and photophysical properties†‡

Claire Brennan,a   Apparao Draksharapu,b   Wesley R. Browne,b   John J. McGarvey,c   Johannes G. Vosa  and  Mary T. Pryce*a  

* Corresponding authors

a SRC for Solar Energy Conversion, School of Chemical Sciences, Faculty of Science and Health, Dublin City University, Dublin 9, Ireland
E-mail: mary.pryce@dcu.ie
Fax: +00353-1-7005503
Tel: +00353-1-7008005

b Stratingh Institute for Chemistry and Zernike Institute for Advanced materials, Faculty of Mathematics and Natural Sciences, The University of Groningen, Nijenborgh 4, Groningen, The Netherlands

c School of Chemistry and Chemical Engineering, Queen's University Belfast, Belfast, Northern Ireland, UK

Abstract

The regioselective methylation of a ruthenium polypyridyl complex bearing both a 1,2,4-triazolato and a pyrazine moiety is reported. In contrast to previous studies in which methylation of the 1,2,4-triazolato ring was observed, in the present system methylation takes place exclusively at the non-coordinated nitrogen of the pyrazine ring. The monomethylation is confirmed by 1H NMR spectroscopy and ESI-MS and the electronic properties of the methylated complexes are studied by UV/vis absorption, emission, surface enhanced, resonance and transient resonance Raman spectroscopy. Ligand deuteriation is used to simplify the 1H NMR spectra and to assign definitively the Raman spectra. Acid–base studies show that the triazolato ring of the N-methylated complexes can be protonated at low pH and that at high pH the N-methyl group can be deprotonated reversibly. Furthermore it is shown that under conditions where the methyl group is deprotonated, demethylation occurs to recover the initial complex.

Graphical abstract: Unexpected reversible pyrazine based methylation in a Ru(ii) complex bearing a pyrazin-2′-yl-1,2,4-triazolato ligand and its effect on acid/base and photophysical properties

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Article information

DOI
https://doi.org/10.1039/C2DT31589K
Article type
Paper
Submitted
17 Jul 2012
Accepted
21 Nov 2012
First published
21 Nov 2012

Dalton Trans., 2013,42, 2546-2555

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Unexpected reversible pyrazine based methylation in a Ru(II) complex bearing a pyrazin-2′-yl-1,2,4-triazolato ligand and its effect on acid/base and photophysical properties

C. Brennan, A. Draksharapu, W. R. Browne, J. J. McGarvey, J. G. Vos and M. T. Pryce, Dalton Trans., 2013, 42, 2546 DOI: 10.1039/C2DT31589K

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