First π-linker featuring mercapto and isocyano anchoring groups within the same molecule: synthesis, heterobimetallic complexation and self-assembly on Au(111)Electronic supplementary information (ESI) available: Experimental procedures, spectroscopic and analytical data, details of the crystallographic and computational studies. CCDC 1410785. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc04017e

• Published in: Chemical science (Cambridge) Vol. 7; no. 2; pp. 1422 - 1429
• Main Authors: Applegate, Jason C, Okeowo, Monisola K, Erickson, Nathan R, Neal, Brad M, Berrie, Cindy L, Gerasimchuk, Nikolay N, Barybin, Mikhail V
• Format: Journal Article
• Language: English
• Published: Royal Society of Chemistry 26.01.2016
• Subjects: Chemistry
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c5sc04017e

Mercapto (-SH) and isocyano (-N&z.tbd;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&z.tbd;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) 5 Cr(η 1 -2-isocyano-1,3-diethoxycarbonyl-6-mercaptoazulene)] ( 7 ) with Ph 3 PAuCl, under basic conditions, afforded X-ray structurally characterized heterobimetallic Cr 0 /Au I ensemble [(OC) 5 Cr(μ-η 1 :η 1 -2-isocyano-1,3-diethoxycarbonyl-6-azulenylthiolate)AuPPh 3 ] ( 8 ). Analysis of the 13 C NMR chemical shifts for the [(NC)Cr(CO) 5 ] core in a series of the related complexes [(OC) 5 Cr(2-isocyano-6-X-1,3-diethoxy-carbonylazulene)] (X = -N&z.tbd;C, Br, H, SH, SCH 2 CH 2 CO 2 CH 2 CH 3 , SAuPPh 3 ) unveiled remarkably consistent inverse-linear correlations δ ( 13 CO trans ) vs. δ ( 13 CN) and δ ( 13 CO cis ) vs. δ ( 13 CN) that appear to hold well beyond the above 2-isocyanoazulenic series to include complexes [(OC) 5 Cr(CNR)] containing strongly electron-withdrawing substituents R, such as CF 3 , CFClCF 2 Cl, C 2 F 3 , and C 6 F 5 . In addition to functioning as a sensitive 13 C NMR handle, the essentially C 4v -symmetric [(-NC)Cr(CO) 5 ] moiety proved to be an informative, remote, ν N&z.tbd;C / ν C&z.tbd;O infrared reporter in probing chemisorption of 7 on the Au(111) surface. Azulene is a convenient platform for accessing heterobimetallic complexes and self-assembled monolayers of a π-linker with asymmetric junctions.