Patterned Surface Derivatization Using Diels-Alder Photoclick Reaction

The utility of photochemically induced hetero-Diels Alder reaction for the light-directed surface derivatization and patterning was demonstrated. Glass slides functionalized with vinyl ether moieties are covered with aqueous solution of substrates conjugated to 3-(hydroxymethyl)-2-naphthol (NQMP). Subsequent irradiation via shadow mask results in an efficient conversion of the latter functionality into reactive 2-napthoquinone-3-methide (oNQM) in the exposed areas. oNQM undergoes very facile hetero Diels-Alder addition (k(D-A) approximate to 4 x 10(4) M(-1)s(-1)) to immobilized vinyl ether molecules resulting in a photochemically stable covalent link between a substrate and a surface. Unreacted oNQM groups are rapidly hydrated to regenerate NQMP. The click chemistry based on the addition of photochemically generated oNQM to vinyl ether works well in aqueous solution, proceeds at high rate under ambient conditions, and does not require catalyst or additional reagents. This photoclick strategy represents an unusual paradigm in photopatterning: the surface itself is photochemically inert, while photoreactive component is present in the solution. The short lifetime (tau approximate to 7 ms in H2O) of the active form of a photoclick reagent in aqueous solution prevents its migration from the site of irradiation, thus allowing for the spatial control of surface derivatization. Both o-napthoquinone methide precursors and vinyl ethers are stable in dark and the reaction is orthogonal to other derivatization techniques, such as acetylene-azide click reaction.