Effect of N-Methylation on Dopamine Surface Chemistry

Abstract

Dopamine (DA) surface chemistry has received significant attention because of its applicability in a wide range of research fields and the ability to graft functional molecules onto numerous solid surfaces. Various DA derivatives have been newly synthesized to identify key factors affecting the coating efficiency and to advance the coating system development. The oxidation of catechol into quinone followed by internal cyclization via the nucleophilic attack of primary amine is crucial for DA-based surface coating. Thus, it is expected that the amine group’s nucleophilicity control directly affects the coating efficiency. However, it has not been systematically investigated, and most studies have been conducted with the focus on the transformation of amines into amides, despite such approaches decreasing the coating efficiency; the nitrogen in amides is less nucleophilic than that in free amines. In this study, we investigated the effect of N-alkylation on dopamine surface chemistry. N,N-Dimethyldopamine (DMDA) was newly synthesized, and the coating efficiency was systematically compared with DA and N-methyldopamine (MDA). DA N-monomethylation improved the coating rate by increasing the nitrogen nucleophilicity, whereas N,N-dimethylation dramatically decreased the DA surface coating property. In addition, MDA remained capable of universal surface coating and secondary reactions using the surface catechols. This study provides opportunities for developing coating materials with advanced functions and an improved coating rate.

Control of Intermolecular Interactions toward the Production of Free-Standing Interfacial Polydopamine Films

“…55 Simultaneously, secondary amine abundance in the DA oxidation products indicates the elevated intramolecular cyclization rate. 56,57 Therefore, the effect of the Cu 2+ ions appears in both intermolecular and intramolecular interactions. Moreover, XPS showed that copper is present in the obtained films only in the form of the +2 ion (Figure S10).…”

Laser-Induced Graphitization of Polydopamine on Titania Nanotubes

“…Those procedures can include monomer alteration at the synthesis level (adrenaline, noradrenaline, L-DOPA, tyrosine derivatives, and more) 9−11 or direct modification of functional groups including amination, carboxylation, 12 and recently also N-methylation. 13 Alternatively, it is possible to include other chemical entities inside the PDA matrix such as transition metals 14,15 or organic molecules during the course of either oxidative or electropolymerization. 16−18 Proposed modifications are aimed at an incredibly vast scope of applications such as supercapacitors, 19 protection from photocorrosion, 20 generation of fluorescence, 21 flexible electronics, 2 and biomedicine including biosensing; PDA can act as an element of the organic layer onto the electrode 18,22 or as an imprinted polymer.…”

“…Polydopamine (PDA) and melanin-based materials represent a vast research topic in electrochemistry photochemistry, surface science, and electronics with many promising applications in each field. − Despite its intrinsically rich chemistry − associated with the amine–catechol–quinone interplayand possibilities for various physical structures including π–π stacking, π-cation, or aryl–aryl linking − there are still numerous procedures for altering its structure on various levels. Those procedures can include monomer alteration at the synthesis level (adrenaline, noradrenaline, l -DOPA, tyrosine derivatives, and more) − or direct modification of functional groups including amination, carboxylation, and recently also N-methylation . Alternatively, it is possible to include other chemical entities inside the PDA matrix such as transition metals , or organic molecules during the course of either oxidative or electropolymerization. − Proposed modifications are aimed at an incredibly vast scope of applications such as supercapacitors, protection from photocorrosion, generation of fluorescence, flexible electronics, and biomedicine including biosensing; PDA can act as an element of the organic layer onto the electrode , or as an imprinted polymer …”

Poly-2-aminomethyl-3-(3,4-dihydroxyphenyl)propionamide: From Structure to Proprieties

“…There are mainly three distinct routes usually followed for obtaining such analogues: by post modification of PDA using various functional groups, by copolymerization with other monomeric units or other polymers, and by synthesizing new catecholamine monomers and their subsequent polymerization. − As the catechol ring, which is essential for both self-polymerization and surface coating, is the common structural unit also for any dopamine derivative, the development of new catecholamine monomers relies on modifications to the side chain, including the terminal amino group. The most numerous examples of such derivatives are based on l -DOPA , and norepinephrine, , though the series of analogues also extends to derivatives with alkyl chain length-related variants, N -methylation, amine group substitution to azide, or derivatives such as 3,4-dihydroxybenzhydrazide, each of which with its own peculiarities is related to the mechanism of formation or the ability to coat different surfaces.…”