Immobilization of Ethynyl‐π‐Extended Electron Acceptors with Amino‐Terminated SAMs by Catalyst‐Free Click Reaction

• Published in: Chemistry : a European journal 2020-12, Vol.26 (68), p.15931-15937
• Main Authors: Nakano, Kyohei, Sanematsu, Haruki, Kaji, Yumiko, Takai, Atsuro, Tajima, Keisuke
• Format: Article
• Language: English
• Subjects: Catalysts; Chemical reactions; Chemistry; click chemistry; Immobilization; naphthalenediimide; organic–inorganic hybrid composites; Photoelectric emission; self-assembled monolayers; Silicon dioxide; Spectroscopy; Steric hindrance; surface immobilization; Surface properties; Thickness
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202001750

Surface modification of SiO2 using a catalyst‐free quantitative reaction between an amine and an ethynyl‐π‐extended naphthalenediimide was investigated. A post‐reaction method, in which the catalyst‐free reaction was performed at the surface after the formation of amino‐terminated self‐assembled monolayers (SAMs), resulted in dense, uniform modification of the SiO2 surface with the naphthalenediimide molecules. Both X‐ray reflectivity and angle‐resolved X‐ray photoemission spectroscopy showed consistent results for the layer thickness and density. In contrast, a pre‐reaction method, in which an amino‐silane and the ethynyl‐π‐extended naphthalenediimide reacted first and then formed a SAM, afforded a sparse SAM on the SiO2 surface, probably due to the steric hindrance of the naphthalenediimide moieties. The in situ decoration of the SiO2 surface by a catalyst‐free quantitative reaction offers a facile route for modifying surface properties with various π‐conjugated molecules suitable for many applications. Surface modification of SiO2 with naphthalenediimides (NDIs) was achieved through a catalyst‐free click reaction between an amine and an ethynyl‐substituted NDI. An in situ click reaction on amino‐terminated self‐assembled monolayers (SAMs) was much more effective to attach NDIs densely than an ex situ click reaction which afforded an NDI‐attached silane coupling reagent, followed by the SAM formation (see Figure).