Nature of halogen bonding involving π-systems, nitroxide radicals and carbenes: a highlight of the importance of charge transfer

Ang, Shi Jun; Mak, Adrian M.; Wong, Ming Wah

doi:10.1039/c8cp04075c

Cited by 28 publications

(31 citation statements)

References 67 publications

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“…In our previous works, we concluded that isolated benzene···X 2 dimers adopt the η 2 (over‐bond) binding mode and noted that η 1 (over‐atom) binding mode is very close in energy as compared to the former . Hence, AR‐type XBs are rim‐specific.…”

Section: Resultsmentioning

confidence: 92%

“…Recently, we highlighted the importance of π‐type XBs in an extensive crystallographic database search and elucidated their intriguing site specificity . Along with several other groups, we also emphasized the importance of charge transfer interactions in obtaining accurate interaction energies and XB geometries . In order to accelerate the process of material discovery and to reduce the number of experimental trial‐and‐error cycles, it is important to utilize computational chemistry and physics tools tactfully in directing experiments.…”

Section: Introductionmentioning

confidence: 99%

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Modeling halogen bonding with planewave density functional theory: Accuracy and challenges

Ang¹,

Ser

Wong

2019

J Comput Chem

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Inspired by the recent interest of halogen bonding (XB) in the solid state, we detail a comprehensive benchmark study of planewave DFT geometry and interaction energy of lone‐pair (LP) type and aromatic (AR) type halogen bonded complexes, using PAW and USPP pseudopotentials. For LP‐type XB dimers, PBE‐PAW generally agrees with PBE/aug‐cc‐pVQZ(−pp) geometries but significantly overbinds compared to CCSD(T)/aug‐cc‐pVQZ(‐pp). Grimme's D3 dispersion corrections to PBE‐PAW gives better agreement to the MP2/cc‐pVTZ(‐pp) results for AR‐type dimers. For interaction energies, PBE‐PAW may overbind or underbind for weaker XBs but clearly overbinds for stronger XBs. D3 dispersion corrections exacerbate the overbinding problem for LP‐type complexes but significantly improves agreement for AR‐type complexes compared to CCSD(T)/CBS. Finally, for periodic XB crystals, planewave PBE methods slightly underestimate the XB lengths by 0.03 to 0.05 Å. © 2019 Wiley Periodicals, Inc.

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Modeling halogen bonding with planewave density functional theory: Accuracy and challenges

Ang¹,

Ser

Wong

2019

J Comput Chem

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“…It is important to note that the molecular orbital interaction provides a proper description of the charge transfer contribution in XB formation. Various energy decomposition analyses showed strong supporting evidence for the role of charge transfer [8][9][10]. In particular, the frontier orbital interaction explains the site specificity of XB involving aromatic XB-acceptors, while the electrostatic model based on ESP fails to explain the site specificity [5].…”

Section: Introductionmentioning

confidence: 99%

Application of Halogen Bonding to Organocatalysis: A Theoretical Perspective

Hui

Wong

2020

Molecules

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The strong, specific, and directional halogen bond (XB) is an ideal supramolecular synthon in crystal engineering, as well as rational catalyst and drug design. These attributes attracted strong growing interest in halogen bonding in the past decade and led to a wide range of applications in materials, biological, and catalysis applications. Recently, various research groups exploited the XB mode of activation in designing halogen-based Lewis acids in effecting organic transformation, and there is continual growth in this promising area. In addition to the rapid advancements in methodology development, computational investigations are well suited for mechanistic understanding, rational XB catalyst design, and the study of intermediates that are unstable when observed experimentally. In this review, we highlight recent computational studies of XB organocatalytic reactions, which provide valuable insights into the XB mode of activation, competing reaction pathways, effects of solvent and counterions, and design of novel XB catalysts.

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“…This approach has been employed to investigate observable shifts induced by intermolecular binding, such as the red or blue shifts in vibrational frequencies upon the formation of hydrogen or halogen bonds. [44][45][46][47][48] However, it has not been made generally possible yet to separate the observable effects of forward/backward CT in a manner that is similar to how the ALMO-CTA identifies the A→B and B→A contributions for a pair of fragments A and B, 9 even though such a partition is highly desirable in particular for interpretation purposes. One early exception was the already mentioned CSOV approach, which employed full SCF for one fragment in the field of e.g.…”

Section: Introductionmentioning

confidence: 99%

Variational Forward–Backward Charge Transfer Analysis Based on Absolutely Localized Molecular Orbitals: Energetics and Molecular Properties

Loipersberger

Mao

Head‐Gordon

2020

J. Chem. Theory Comput.

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To facilitate the understanding of charge transfer (CT) effects in dative complexes, we propose a variational forward-backward (VFB) approach to decompose the overall CT stabilization energy into contributions from forward and backward donation in the framework of energy decomposition analysis based on absolutely localized molecular orbitals (ALMO-EDA). Such a decomposition is achieved by introducing two additional constrained intermediate states in which only one direction of CT is permitted. These two "one-way" CT states are variationally relaxed such that the associated nuclear forces can be readily obtained. This allows for a facile integration into the previously developed adiabatic EDA scheme so that the molecular property changes arising from 1 forward and back donation can be separately assigned. Using ALMO-EDA augmented by this VFB model, we investigate the energetic, geometric, and vibrational features of complexes composed of CO and main group Lewis acids (BH 3 , BeO/BeCO 3), and complexes of the N 2 , CO, and BF isoelectronic series with [Ru(II)(NH 3) 5 ] 2+. We identify that the shift in the stretching frequency of a diatomic π-acidic ligand (XY), such as CO, results from a superposition of the shifts induced by permanent electrostatics and backward CT: permanent electrostatics can cause an either red or blue shift depending on the alignment of the XY dipole in the dative complex, and this effect becomes more pronounced with a more polar XY ligand; the back-donation to the antibonding π orbital of XY always lowers the X−Y bond order and thus red-shifts its stretching frequency, and the strength of this interaction decays rapidly with the intermolecular distance. We also reveal that while σ forward donation contributes significantly to energetic stabilization, it affects the vibrational feature of XY mainly by shortening the intermolecular distance, which enhances both the electrostatic interaction and backward CT but in different rates. The synergistic effect of the forward and backward donations appears to be more significant in the transition metal complexes, where the forward CT plays an essential role in overcoming the strong Pauli repulsion. These findings highlight that the shift in the XY stretching frequency is not a reliable metric for the strength of π back-donation. Overall, the VFB-augmented EDA scheme that we propose and apply in this work provides a useful tool to characterize the role played by each physical component that all together lead to the frequency shift observed.

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Nature of halogen bonding involving π-systems, nitroxide radicals and carbenes: a highlight of the importance of charge transfer

Abstract: The adiabatic ALMO-EDA analyses indicate that charge transfer is important in accurate description of halogen bonding (XB) involving π-systems, nitroxide radicals and carbenes as XB acceptors.

Cited by 28 publications

References 67 publications

Modeling halogen bonding with planewave density functional theory: Accuracy and challenges

Modeling halogen bonding with planewave density functional theory: Accuracy and challenges

Application of Halogen Bonding to Organocatalysis: A Theoretical Perspective

Variational Forward–Backward Charge Transfer Analysis Based on Absolutely Localized Molecular Orbitals: Energetics and Molecular Properties

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