Issue 2, 2016

First π-linker featuring mercapto and isocyano anchoring groups within the same molecule: synthesis, heterobimetallic complexation and self-assembly on Au(111)

Abstract

Mercapto (–SH) and isocyano (–N[triple bond, length as m-dash]C) terminated conducting π-linkers are often employed in the ever-growing quest for organoelectronic materials. While such systems typically involve symmetric dimercapto or diisocyano anchoring of the organic bridge, this article introduces the chemistry of a linear azulenic π-linker equipped with one mercapto and one isocyano terminus. The 2-isocyano-6-mercaptoazulene platform was efficiently accessed from 2-amino-6-bromo-1,3-diethoxycarbonylazulene in four steps. The 2-N[triple bond, length as m-dash]C end of this 2,6-azulenic motif was anchrored to the [Cr(CO)5] fragment prior to formation of its 6-SH terminus. Metalation of the 6-SH end of [(OC)5Cr(η1-2-isocyano-1,3-diethoxycarbonyl-6-mercaptoazulene)] (7) with Ph3PAuCl, under basic conditions, afforded X-ray structurally characterized heterobimetallic Cr0/AuI ensemble [(OC)5Cr(μ-η11-2-isocyano-1,3-diethoxycarbonyl-6-azulenylthiolate)AuPPh3] (8). Analysis of the 13C NMR chemical shifts for the [(NC)Cr(CO)5] core in a series of the related complexes [(OC)5Cr(2-isocyano-6-X-1,3-diethoxy-carbonylazulene)] (X = –N[triple bond, length as m-dash]C, Br, H, SH, SCH2CH2CO2CH2CH3, SAuPPh3) unveiled remarkably consistent inverse-linear correlations δ(13COtrans) vs. δ(13CN) and δ(13COcis) vs. δ(13CN) that appear to hold well beyond the above 2-isocyanoazulenic series to include complexes [(OC)5Cr(CNR)] containing strongly electron-withdrawing substituents R, such as CF3, CFClCF2Cl, C2F3, and C6F5. In addition to functioning as a sensitive 13C NMR handle, the essentially C4v-symmetric [(–NC)Cr(CO)5] moiety proved to be an informative, remote, νN[triple bond, length as m-dash]C/νC[triple bond, length as m-dash]O infrared reporter in probing chemisorption of 7 on the Au(111) surface.

Graphical abstract: First π-linker featuring mercapto and isocyano anchoring groups within the same molecule: synthesis, heterobimetallic complexation and self-assembly on Au(111)

Supplementary files

Article information

Article type
Edge Article
Submitted
22 Oct 2015
Accepted
20 Nov 2015
First published
20 Nov 2015
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2016,7, 1422-1429

Author version available

First π-linker featuring mercapto and isocyano anchoring groups within the same molecule: synthesis, heterobimetallic complexation and self-assembly on Au(111)

J. C. Applegate, M. K. Okeowo, N. R. Erickson, B. M. Neal, C. L. Berrie, N. N. Gerasimchuk and M. V. Barybin, Chem. Sci., 2016, 7, 1422 DOI: 10.1039/C5SC04017E

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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