Using a hydrazone-protected benzenediazonium salt to introduce a near-monolayer of benzaldehyde on glassy carbon surfaces

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Title: Using a hydrazone-protected benzenediazonium salt to introduce a near-monolayer of benzaldehyde on glassy carbon surfaces
Author(s): Malmos, Kristoffer; Dong, Mingdong; Pillai, Saju; Kingshott, Peter; Besenbacher, Flemming; Pedersen, Steen U.; Daasbjerg, Kim
Abstract: A methodology is described for introducing a thin layer of covalently attached benzaldehyde on glassy carbon surfaces using aryl diazonium chemistry. Usually the electroreduction of aryl diazonium salts leads to the formation of an ill-defined multilayer because of the involvement of highly reactive aryl radicals that can add to already-grafted aryl groups. However, in this study we used a two-step "formationdegradation" procedure to solve this problem with the first step consisting of an electrografting of an aryl diazonium salt of a long-chain and bulky alkyl hydrazone onto a glassy carbon surface. The design of the hydrazone group serves to minimize multilayer formation by greatly diminishing the grafting rate after the first-layer formation and at the same time preventing radical additions from taking place at the inner aryl ring. Another valuable property of the hydrazone group is that it easily can be deprotected to the corresponding aldehyde by acid hydrolysis (i.e., the degradation step). In this manner, a thin and welldefined film of covalently attached benzaldehyde with an estimated coverage of 4 × 10-10 mol cm-2 was formed. The electrochemical responses of benzaldehyde were highly reproducible and largely independent of grafting medium (water or DMSO) and along with that also the thickness of the initially grafted film. AFM and contact angle measurements support the findings. The "formation- degradation" approach thus lays the foundation for carrying out further functionalization reactions in a controlled manner.
Publication type: Journal article
Source: Journal of the American Chemical Society, Vol. 131, no. 13 (2009), pp. 4928-4936
Publication year: 2009
FOR Code(s): 03 Chemical Sciences; 06 Biological Sciences; 09 Engineering
Keyword(s): Acid hydrolysis; AFM; Aldehydes; Angle measurement; Aryl group; Aryl rings; Aryldiazonium salts; Atomic force microscopy; Benzaldehyde; Benzene; Benzenediazonium salt; Carbon; Chemical analysis; Chemical reaction; Chemical structure; Contact angle; Degradation; Diazonium chemistry; Diazonium compound; Dimethyl sulfoxide; Electro reduction; Electrochemical response; Electrografting; Electrolytic reduction; Functionalisation reactions; Glassy carbon surfaces; Grafted films; Grafting; Grafting rate; Hydrazone; Hydrazone derivative; Layer formation; Monolayers; Multilayer formation; Multilayers; Radical addition; Thin layers
Publisher: American Chemical Society
ISSN: 0002-7863
Publisher URL: http://dx.doi.org/10.1021/ja809816x
Peer reviewed