Dynamic Covalent Self‐sorting in Molecular and Polymeric Architectures Enabled by Spiroborate Bond Exchange

Abstract

Self-sorting is commonly observed in complex reaction systems, which has been utilized to guide the formation of single major by-design molecules. However, most studies have been focused on non-covalent systems, and using self-sorting to achieve covalently bonded architectures is still relatively less explored. Herein, we first demonstrated the dynamic nature of spiroborate linkage and systematically studied the selfsorting behavior observed in the transformation between spiroborate-linked well-defined polymeric and molecular architectures, which is enabled by spiroborate bond exchange. The scrambling between a macrocycle and a 1D helical covalent polymer led to the formation of a molecular cage, whose structures are all unambiguously elucidated by single-crystal X-ray diffraction. The results indicate that the molecular cage is the thermodynamically favored product in this multi-component reaction system. This work represents the first example of a 1D polymeric architecture transforming into a shape-persistent molecular cage, driven by dynamic covalent self-sorting. This study will further guide the design of spiroborate-based materials and open the possibilities for the development of novel complex yet responsive dynamic covalent molecular or polymeric systems.

Cavity-Shape-Dependent Divergent Chemical Reaction inside Aqueous Pd6L4 Cages

“…The tripyridyl ligand L1 with a pyrimidine core was synthesized by the basemediated condensation of 4-acetylpyridine and 4-pyridinecarbonitrile at 120 °C in an autoclave reactor (Scheme S1). The ligand was characterized by electrospray ionization mass spectrometry (ESI-MS), proton nuclear magnetic resonance (1 HNMR) and (carbon NMR) 13 C NMR in CDCl 3 (Figures S1 and S2). Due to the unsymmetrical nature of the ligand L1, it had 2:1 splitting of the αand β-hydrogen of the pyridine rings (Figures 1 and S1).…”

“…Organic cages or macrocycles are generally neutral and soluble in common organic solvents. For this reason, most organic cages − and macrocycles do not bind strongly to soluble organic guests, and instances of guest uptake and subsequent chemical transformation inside the cavity are less explored . Metal–organic cages, on the other hand, are charged.…”

Dual reactivity based dynamic covalent chemistry: mechanisms and applications

“…A number of DCRs have been added into the toolbox of DCC. 4 Some recently reported reversible covalent bonds include orthoester exchange, 33 silyl ether exchange, 34,35 spiroborate bond exchange, 36 and ring opening of cyclic anhydride/amide. 37,38 Moreover, the manipulation of unique reactivity of heterocycles led to the development of reversible nucleophilic aromatic substitution reactions 39–41 and cycloaddition reactions.…”

Uncovering tetrazoles as building blocks for constructing discrete and polymeric assemblies

“…On the other hand, discrete coordination assemblies, which are comprised of metal-organic cages (MOCs) and metallacycles (MCs), exhibit better solubility in polar and non-polar solvents. [46][47][48][49] These structures have diverse applications ranging from catalysis, [50][51][52][53][54][55][56][57] selective separation, [58][59][60][61][62] fluorescence tuning, [63][64][65][66][67][68] sensing, [69][70][71] to photochromism. 72,73 Most self-assembled coordination assemblies use pyridines, carboxylates and imidazoles as the primary linking motifs to the metal centres.…”