NoteProducts of hydrolysis of (ferrocenylmethyl)trimethylammonium iodide: Synthesis of hydroxymethylferrocene and bis(ferrocenylmethyl) ether
Graphical abstract
Hydroxymethylferrocene and bis(ferrocenylmethyl)ether have been isolated as hydrolysis products of (ferrocenylmethyl)trimethylammonium iodide during the synthesis of 1-(ferrocenemethyl)-4,7,10-(triformyl)-1,4,7,10-tetraazacyclododecane.
Introduction
Our group has recently focused attention on the development of redox (bio)sensors using metal complexes for the possible electrochemical recognition of thymine derivatives [1] and the nitrate anion [2]. The ligand used in these studies was the previously reported 1-(ferrocenemethyl)-1,4,7,10-tetraazacyclododecane [3] (6) (Fig. 1) with the ferrocene (Fc) of 6 being used as the redox-active moiety. We also demonstrated that the complexation of 6 with CuII added a supplementary redox moiety that enabled a double electrochemical recognition of nitrate in acetonitrile and nitromethane [2]. A larger electrochemical shift was obtained upon the addition of nitrate for the CuII/I centre than for Fc0/+ due to coordination of the nitrate to the copper centre. These promising results led us to investigate a shorter synthetic pathway to 6 [2], than the previously published procedure [3], involving the formation of 1,4,7-tris-tert-butoxycarbonyl-10-(ferrocenylmethyl)-1,4,7,10-tetraazacyclododecane with the subsequent acidic cleavage of the tert-butoxycarbonyl (BOC) groups, Unfortunately, this method did not yield the desired product. Furthermore, during another attempt to prepare 3, the unexpected formation of hydroxymethylferrocene (4) (also known as ferrocenemethanol) and bis(ferrocenylmethyl) ether (5) was observed (Fig. 1). Due to the importance of attaching ferrocene to molecules of biological interest or for electrochemical sensing, as recently underlined by Metzler-Nolte and van Staveren [4] and Tucker and Collinson [5], we report, in this paper, these results and the X-ray crystal structures of 4 and 5.
Section snippets
Materials
All chemicals were of reagent grade purity or better, and used as obtained from the commercial suppliers. Deionised water was distilled prior to use.
Instrumentation
1H and 13C NMR spectra were recorded at 30 °C in deuterated solvents using either Bruker AC200, Bruker DPX300 or Avance DRX400 Bruker spectrometers. The residual solvent resonances were used as the internal reference for spectra recorded in non-aqueous solvents. Low resolution electrospray mass spectra were obtained with a Micromass Platform II
Synthesis
Sisti et al. recently reported the synthesis of 1-(ferrocenemethyl)-4,7,10-(triformyl)-1,4,7,10-tetraazacyclododecane (3) [3]. Their method involved the coupling of the two known compounds (ferrocenylmethyl)trimethylammonium iodide [6] (1) and 1,4,7-(triformyl)-1,4,7,10-tetraazacyclododecane (2) in DMF in the presence of K2CO3. To avoid the use of the high boiling and environmentally unfriendly solvent DMF, the same coupling reaction was successfully attempted by our group in deoxygenated
Conclusion
Two known compounds, namely hydroxymethylferrocene (4) and bis(ferrocenylmethyl) ether (5), have been isolated during the synthesis of 1-(ferrocenemethyl)-4,7,10-(triformyl)-1,4,7,10-tetraazacyclododecane (3). The X-ray structures of 4 and 5 were determined and, in the case of 4, an interesting hydrogen-bonded helicoidal chain arrangement of hydroxymethylferrocene units was observed. The O⋯O separation was found to be significantly shorter than in similar examples previously reported. The
Supplementary material
CCDC 641127 and 641128 contain the supplementary crystallographic data for 4 and 5. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected].
Acknowledgements
This work was supported by the Swiss National Science Foundation (SNSF) and the Australian Research Council (ARC) through the Australian Centre for Electromaterials Science (ACES). G.G. was the recipient of a Swiss Fellowship for Prospective Researchers Grant (PBNE2-106771).
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