Versatile method for chemical reactions with self-assembled monolayers of alkanethiols on gold

Self-assembled monolayers (SAMs) of 11-mercapto-1-undecanol (TOH) and mixed monolayers of TOH and dodecanethiol (TCH3) were transformed to isocyanate- bearing layers by reaction of the hydroxyl groups in the monolayers and mix ed layers with 1,4-phenylene diisocyanate (PDI). PDI reacts with only one o f its isocyanate groups, yielding a carbamate (urethane) group; conversion of the hydroxyl groups is nearly quantitative, and the attached phenylene i socyanate moiety is oriented perpendicularly to the surface, as indicated b y IR reflection measurements at grazing incidence. The free isocyanate grou ps readily react under mild conditions with a variety of substances, for ex ample, water, alcohols, and amines. Hence, the conversion of surface hydrox yl groups with PDI offers a versatile and straightforward method to modify surfaces and to facilitate further reactions with additional compounds.