Quaternary 2:2 Complexes as Kinetic Intermediates: Unveiling an Overlooked Pathway in Cucurbit[8]uril-Mediated Assembly

Abstract

Molecular assembly is typically viewed as a stepwise process from lower- to higher-order structures. Here, we uncovered an alternative kinetic pathway in the cucurbit[8]uril (CB[8])-mediated assembly, where a transient quaternary (2:2) complex formed before the thermodynamically favored ternary (2:1) product. Stopped-flow spectroscopy and structural analysis confirmed the 2:2 intermediate, which formed 36-fold faster than the direct 1:1 → 2:1 pathway at 298 K. The system thus accumulated in the 2:2 state before relaxing to the 2:1 product. These findings revise the conventional binary-to-ternary model and highlight the mechanistic relevance of higher-order intermediates. It also refines our understanding of apparent cooperativity within a complex assembly network. Recognizing such kinetic complexity opens new avenues for dynamic control in the design of high-performance functional and structural materials.

Tianyi Yang

PhD Candidate (2021)

She is very casual most of the time, and occasionally very obsessed with something.

Yuanchen Shen

Undergraduate student (2019)

Yuanchen Shen is currently a 2${}^{nd}$ year undergraduate student majoring in Chemistry.

Haoyuan Qu

PhD Candidate (2022)

This student is a genuine Changchun native, friendly and approachable.

Yibin Sun

Assistant Professor

Research interests: catassembly, assembly kinetics, protein-protein assembly, and protein engineering

Guanglu Wu

Professor

Research interests: multi-component functional assemblies, noncovalent dimerization, supramolecular catalysis, and smart soft matter