Synthesis of a Two‐Dimensional Covalent Organic Monolayer through Dynamic Imine Chemistry at the Air/Water Interface

Abstract

A two‐dimensional covalent organic monolayer was synthesized from simple aromatic triamine and dialdehyde building blocks by dynamic imine chemistry at the air/water interface (Langmuir–Blodgett method). The obtained monolayer was characterized by optical microscopy, scanning electron microscopy, and atomic force microscopy, which unambiguously confirmed the formation of a large (millimeter range), unimolecularly thin aromatic polyimine sheet. The imine‐linked chemical structure of the obtained monolayer was characterized by tip‐enhanced Raman spectroscopy, and the peak assignment was supported by spectra simulated by density functional theory. Given the modular nature and broad substrate scope of imine formation, the work reported herein opens up many new possibilities for the synthesis of customizable 2D polymers and systematic studies of their structure–property relationships.

Equilibration of Imine‐Linked Polymers to Hexagonal Macrocycles Driven by Self‐Assembly

“…[12] The solid-state ordering of shape-persistent macrocycles mimics that of 2D covalent organic frameworks (COFs), whicha re extended, periodics tructures with permanent porositya nd high internal surface areas. These findings provide insight into the crystallization of imine-linked 2D COFs and portendf uture efforts to obtain 2D polymers by cross-linking assembled macrocycles in the solid-state, [23] at the air-water interface, [24] or on surfaces. For example, both boronate ester-linked macrocycles [16] and 2D COFs assemble into layered, hexagonally packed structures through similar nucleation-elongation growth mechanisms.…”

“…[21] Am echanistics tudy of the 2D COF derived from TAPB and PDA demonstrated that the monomersr apidly condense into an amorphous network that later crystallizes into aT APB-PDA COF. These findings provide insight into the crystallization of imine-linked 2D COFs and portendf uture efforts to obtain 2D polymers by cross-linking assembled macrocycles in the solid-state, [23] at the air-water interface, [24] or on surfaces. Truncated analogueso fT APB react with PDA similarly to first form linear polymers and oligomers (Scheme 1).…”

Soluble Two‐Dimensional Covalent Organometallic Polymers by (Arene)Ruthenium‐Sulfur Chemistry

“…Various strategies yielding extended sheets of mono-molecular thickness, often described as 2D covalent polymers with a high degree of crosslinking, have been reported in the last few years. [10][11][12] Synthesis at heterogeneous interfaces, vacuum/solid, [13][14][15][16][17][18] air/liquid [19][20][21] , liquid/liquid, 22,23 and in solid phases, [24][25][26] have been demonstrated indeed. All these methods need to be followed by a transfer or exfoliation process, yielding individual layers onto a support of relevance for future applications.…”

Imine‐Based Architectures at Surfaces and Interfaces: From Self‐Assembly to Dynamic Covalent Chemistry in 2D

“…[2][3][4][5][6] Both DCC and supramolecular chemistry are adaptable and modular because they allow for the selection and exchange of molecular components. [11] In particular,D CC includes the chemistry of disulfides, [12,13] acetals, [14,15] esters, [16,17] oxime, [18] boroxine, [19,20] alkynes, [21] and imines [22][23][24][25][26][27][28][29] to allow the generation of new covalents tructures. The equilibration processes are much faster in supramolecular systemsw hen compared to DCC systems, because in the latter the covalentb onds need to be broken and reformed.…”

“…[10] Whereas classical covalent chemistry operates under kinetic control,t he DCC approacht akes advantage of the reversible natureo fb ond formation to generate new covalent structures under thermodynamic control. [11] In particular,D CC includes the chemistry of disulfides, [12,13] acetals, [14,15] esters, [16,17] oxime, [18] boroxine, [19,20] alkynes, [21] and imines [22][23][24][25][26][27][28][29] to allow the generation of new covalents tructures. Chemicalg roups that include aC =No rc arbonyl units, such as imines,e sters, or amides, are of particular interests ince they can undergo disconnection/reconnection cycles (e.g., trans reactions such as esterification, imination, and amidation).…”