n → π* interactions as a versatile tool for controlling dynamic imine chemistry in both organic and aqueous media

Chen, Hang; Ye, Hebo; Yun, Hai; Zhang, Ling; You, Lei

doi:10.1039/c9sc05698j

Cited by 36 publications

(17 citation statements)

References 88 publications

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“…[7] Indeed, this n!p*delocalisation has been increasingly exploited for kinetic reaction selectivity [8a,10] and influencing dynamic covalent equilibria. [11] Despite the recent strong evidence for n!p*d elocalisation from ar ange of experimental and theoretical studies, these results remain unreconciled with earlier studies that indicated an electrostatically driven interaction. [1a, 6] Indeed, both the electrostatic and orbital delocalisation models qualitatively account for the directionality of orthogonal C=O•••C=Oi nteractions resembling the Bürgi-Dunitz nucleophile-carbonyl trajectory.…”

Section: Introductionmentioning

confidence: 89%

Reconciling Electrostatic and n→π* Orbital Contributions in Carbonyl Interactions

et al. 2020

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Interactions between carbonyl groups are prevalent in protein structures. Earlier investigations identified dominant electrostatic dipolar interactions, while others implicated lone pair n→π* orbital delocalisation. Here these observations are reconciled. A combined experimental and computational approach confirmed the dominance of electrostatic interactions in a new series of synthetic molecular balances, while also highlighting the distance‐dependent observation of inductive polarisation manifested by n→π* orbital delocalisation. Computational fiSAPT energy decomposition and natural bonding orbital analyses correlated with experimental data to reveal the contexts in which short‐range inductive polarisation augment electrostatic dipolar interactions. Thus, we provide a framework for reconciling the context dependency of the dominance of electrostatic interactions and the occurrence of n→π* orbital delocalisation in C=O⋅⋅⋅C=O interactions.

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Section: Introductionmentioning

confidence: 89%

Reconciling Electrostatic and n→π* Orbital Contributions in Carbonyl Interactions

et al. 2020

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“…We hypothesized that the amide groups introduced for polymer functionalization perturb the rate and equilibrium constants of the esterification and hydrolysis reactions, through inductive effects, direct coordination to the boron center, 69,70 or internal catalysis. 40,71 To test this hypothesis, we synthesized amide derivatives of each alcohol (Figure 1a, "amide derivatives") and measured the kinetics of their dynamic reactions with PBA using 1D EXSY (Table 1). Indeed, we observed dramatic increases in both esterification and hydrolysis rates for the amide derivatives compared to their simplified alcohol counterparts.…”

Section: Internal Catalysis By the Proximal Amidementioning

confidence: 99%

Internal and external catalysis in boronic ester networks

Kang¹,

Kalow²

2021

Preprint

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In dynamic materials, the reversible condensation between boronic acids and diols provides adaptability, self-healing ability, and responsiveness to small molecules and pH. Recent work has shown that the thermodynamics and kinetics of bond exchange determine the mechanical properties of dynamic polymer networks. However, prior studies have focused on how structural and environmental factors influence boronic acid–diol binding affinity, and design rules for tuning the kinetics of this dynamic bond are lacking. In this work, we investigate the effects of diol (or polyol) structure and salt additives on the rate of bond exchange, binding affinity, and the mechanical properties of the corresponding polymer networks. To better mimic the environment of polymer networks in our small-molecule model systems, we incorporated proximal amide groups, which are used to conjugate diols to polymers, and included salts commonly found in buffers. Using one-dimensional selective exchange spectroscopy (1D EXSY), we find that both proximal amides and buffering anions induce significant rate acceleration consistent with internal and external catalysis, respectively. This rate acceleration is reflected in the stress relaxation of gels formed using PEG modified with different alcohols, and in the presence of salts containing acetate or phosphate. These findings contribute to the fundamental understanding of the boronic ester dynamic bond and offer new molecular strategies to tune the macromolecular properties of dynamic materials.

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“…We wondered the non-covalent intermolecular forces such as n / p* or p / p* interaction generated from the overlapping of the n or p orbital (from the solvent) and Scheme 1 Synthesis route for 3a-d. the p* orbital (from the C]N group) would play a role in stabilizing the imine structures 4c and 4d. [49][50][51][52][53][54] Therefore, using 4c system as a model, the density functional theory (DFT) calculation was performed to study the interactions between solvent molecules and imine 4c. The equilibrium structures and the corresponding natural bonding orbital (NBO) analysis were carried out at the M06-2X-D3/def2TZVP level, and polarizable continuum model (PCM) was employed to simulate the solvation effect.…”

Section: Synthesis Of Picolyl Heterocyclic Amino Aminalsmentioning

confidence: 99%

Physical organic studies and dynamic covalent chemistry of picolyl heterocyclic amino aminals

et al. 2020

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n → π* interactions as a versatile tool for controlling dynamic imine chemistry in both organic and aqueous media

Abstract: A versatile strategy of n → π* interactions was developed for tunable control of dynamic imine chemistry and the regulation of imine formation/exchange in water.

Cited by 36 publications

References 88 publications

Reconciling Electrostatic and n→π* Orbital Contributions in Carbonyl Interactions

Reconciling Electrostatic and n→π* Orbital Contributions in Carbonyl Interactions

Internal and external catalysis in boronic ester networks

Physical organic studies and dynamic covalent chemistry of picolyl heterocyclic amino aminals

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