Charge-transfer interactions of amines with tetrahalomethanes. X-ray crystal structures of the donor-acceptor complexes of quinuclidine and diazabicyclo [2.2.2]octane with carbon tetrabromide

Blackstock, Silas C.; Lorand, John P.; Kochi, J. K.

doi:10.1021/jo00384a013

Cited by 100 publications

(59 citation statements)

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“…Nitrogen compounds are known to form weak electron donor-acceptor complexes with the polyhalogenated molecules, [76][77][78][79] which are now called halogen-bonded complexes. [80,81] As a first approximation, we have modelled this interaction by the association of one solvent molecule halogen-bonded to one or more nitrogen atoms.…”

Section: Piperidine Conformermentioning

confidence: 99%

A Theoretical Evaluation of the pK_HBand Δ$H{{{\,\ominus}\hfill \atop {\rm HB}\hfill}}}$ Hydrogen‐Bond Scales of Nitrogen Bases

Besseau

Graton

Berthelot

2008

Chemistry A European J

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The experimental pKHB hydrogen-bond (HB) basicity scale and the corresponding DeltaH[symbol: see text]HB enthalpic scale of nitrogen compounds are extended and analysed in light of simple theoretical descriptors using the B3LYP density functional method and a medium-size basis set (6-31+G(d,p)).The selected training set includes 59 monofunctional unhindered nitrogen bases for which homogeneous and accurate experimental pKHB and DeltaH[symbol: see text]HB data have been determined by means of the association equilibrium of the bases with a reference hydrogen-bond acid, 4-fluorophenol, in CCl4. The three hybridisation states encountered in the nitrogen atom, sp, sp2 and sp3, are equally represented in this data set. A proper estimation of their experimental enthalpy (DeltaH[symbol: see text]HB) is directly attainable from the theoretical enthalpy of the complexation reaction with hydrogen fluoride (DeltaH[symbol: see text](HF)). However, a second parameter is required to calculate with good accuracy the experimental free energy of association represented by pKHB. About 99% of the variance of the pKHB scale is described by a bilinear equation using the minimum electrostatic potential (Vs,min) of the monomer in addition to the interaction energy (D0(HF). The equations are tested for an external set of 99 additional compounds including very different nitrogen bases such as ortho-substituted pyridines, polyazines and azoles.Theoretical calculations give a reliable estimation of hydrogen-bond basicity provided that the populations of the different isomers of the bases are taken into account by using the Boltzmann law, and that a specific halogen-bond interaction with the solvent CCl4 is considered for polybasic molecules.The pKHB scale can thus be extended to important classes of species experimentally inaccessible in CCl4, to polynitrogen compounds and to molecules of biological significance.

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Section: Piperidine Conformermentioning

confidence: 99%

A Theoretical Evaluation of the pK_HBand Δ$H{{{\,\ominus}\hfill \atop {\rm HB}\hfill}}}$ Hydrogen‐Bond Scales of Nitrogen Bases

Besseau

Graton

Berthelot

2008

Chemistry A European J

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“…Halogen bonding involves a favorable noncovalent interaction between a covalently-bonded halogen and a negative site, such as a lone pair. Such interactions were already known to experimentalists in the 19th century [3,4], and were studied extensively in the 20th [5][6][7][8][9][10], with crystallography playing a major role [10][11][12][13]. Nevertheless the basis for halogen bonding was not really understood.…”

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confidence: 99%

σ-Hole Interactions: Perspectives and Misconceptions

2017

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After a brief discussion of the σ-hole concept and the significance of molecular electrostatic potentials in noncovalent interactions, we draw attention to some common misconceptions that are encountered in that context: (1) Since the electrostatic potential reflects the contributions of both the nuclei and the electrons, it cannot be assumed that negative potentials correspond to "electron-rich" regions and positive potentials to "electron-poor" ones; (2) The electrostatic potential in a given region is determined not only by the electrons and nuclei in that region, but also by those in other portions of the molecule, especially neighboring ones; (3) A σ-hole is a region of lower electronic density on the extension of a covalent bond, not an electrostatic potential; (4) Noncovalent interactions are between positive and negative regions, which are not necessarily associated with specific atoms, so that "close contacts" between atoms do not always indicate the actual interactions.Keywords: σ-holes; noncovalent interactions; electrostatic potential; close contacts A Brief History of the σ-HoleThe σ-hole concept was introduced by Clark in the context of halogen bonding, at a conference in 2005 [1], although it did not appear in the chemical literature until 2007 [2]. Halogen bonding involves a favorable noncovalent interaction between a covalently-bonded halogen and a negative site, such as a lone pair. Such interactions were already known to experimentalists in the 19th century [3,4], and were studied extensively in the 20th [5][6][7][8][9][10], with crystallography playing a major role [10][11][12][13]. Nevertheless the basis for halogen bonding was not really understood. It was frequently rationalized as "charge transfer" from an electron "donor" (e.g., the lone pair) to an "acceptor" (the halogen), invoking the valence bond formalism of Mulliken [14] (which was later put in molecular orbital terms by Flurry [15,16]).However, the halogen is the most electronegative atom in each row of the periodic table, and a singly-bonded halogen atom is generally viewed as being negative in character. So why should it interact attractively with a donor of electronic charge? It was in fact pointed out long ago [7,17] that Mulliken's charge-transfer formalism was not intended to be an elucidation of the bonding in a ground-state noncovalent complex; it was purely a mathematical modeling of the transition of the ground-state complex to a low-lying excited state. The existence of halogen bonding was thus viewed by many as an enigma.The key to resolving the enigma was the molecular electrostatic potential. This is the potential V(r) that is created at any point r in the space of a molecule by its nuclei and electrons, given rigorously by Equation (1):Z A is the charge on nucleus A, located at R A , and ρ(r) is the molecule's electronic density. Regions in which V(r) is positive, indicating the dominance of the nuclear contribution, are attractive to

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“…Solution NMR spectroscopy has proven to be a convenient and sensitive tool to establish the occurrence of XB in supramolecular adducts, to rank the ability of XB donors and acceptors, and even to describe thermodynamic and geometric characteristics of formed adducts. 34 Recently, efforts are directed to indepth, specialized SSNMR analysis, with multinuclear approaches and systematic resort to quantum chemical calculations with DFT-based methods.…”

mentioning

confidence: 99%

Natural Abundance ¹⁵N and ¹³C Solid‐State NMR Chemical Shifts: High Sensitivity Probes of the Halogen Bond Geometry

Vioglio

Catalano

Vasylyeva

et al. 2016

Chemistry A European J

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Solid-State Nuclear Magnetic Resonance (SSNMR) is a versatile characterization technique that can provide a plethora of information complementary to Single Crystal X-Ray Diffraction (SCXRD) analysis. However, the latter is still pivotal in assessing the halogen bond (XB) occurrence and having a rough estimation of its strength through the normalized distance parameter (RXB), obtained from experimental crystallographic data. Herein, we present an experimental and computational investigation of the relationship between the strength of an XB and the SSNMR chemical shifts of the nonquadrupolar nuclei either directly involved in the interaction ( 15 N) or covalently bonded to the halogen atom ( 13 C). We have prepared two series of X-bonded co-crystals based upon two different dipyridyl modules, and several halobenzenes and diiodoalkanes, as XB-donors. SCXRD structures of three novel co-crystals between 1,2-bis(4-pyridyl)ethane, and 1,4-diiodobenzene, 1,6-diiodododecafluorohexane, and 1,8-diiodohexadecafluorooctane are reported. For the first time, the change in the 15 N SSNMR chemical shifts upon XB formation is shown to experimentally correlate with the strength of the XB. The same overall trend is confirmed by density functional theory (DFT) calculations of the chemical shifts.13 C NQS experiments show a positive, linear correlation between the chemical shifts and the C-I elongation, which is an indirect probe of the strength of the XB. These correlations can be of general utility to estimate the strength of the XB occurring in diverse adducts by using affordable SSNMR analysis.In recent years, halogen bonding (XB) has been attracting increasing attention thanks to its applications in different fields, e.g., crystal engineering, materials chemistry, and biochemistry.1-3 The success of this specific noncovalent interaction derives from its unique physico-chemical properties, namely strength, selectivity, tunability, and directionality.4,5 XB spans an energy range similar to that of the more commonly used hydrogen bonding, i.e., 5-200 kJ/mol.6 By changing the XB-donor atom involved in the interaction or its covalently-bound substituents it is possible to fine-tune the final strength of the XB, an extremely useful feature for the design of new supramolecular species. 7 In addition, XB is strongly directional, 8,9 thus enabling the predictable alignment of molecular building blocks into crystalline architectures and functional materials, such as photoresponsive polymers, pharmaceutical co-crystals, porous materials, among others.10-14 XB plays also a key role in anion recognition and coordination both in solid state and in solution, 15,16 ability of relevant interest especially for biological systems. 17 The 2013 IUPAC XB definition states: "A halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity". 18 The counterintuitive electrophilic b...

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Charge-transfer interactions of amines with tetrahalomethanes. X-ray crystal structures of the donor-acceptor complexes of quinuclidine and diazabicyclo [2.2.2]octane with carbon tetrabromide

Cited by 100 publications

References 1 publication

A Theoretical Evaluation of the pK_HBand Δ$H{{{\,\ominus}\hfill \atop {\rm HB}\hfill}}}$ Hydrogen‐Bond Scales of Nitrogen Bases

A Theoretical Evaluation of the pK_HBand Δ$H{{{\,\ominus}\hfill \atop {\rm HB}\hfill}}}$ Hydrogen‐Bond Scales of Nitrogen Bases

σ-Hole Interactions: Perspectives and Misconceptions

Natural Abundance ¹⁵N and ¹³C Solid‐State NMR Chemical Shifts: High Sensitivity Probes of the Halogen Bond Geometry

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Charge-transfer interactions of amines with tetrahalomethanes. X-ray crystal structures of the donor-acceptor complexes of quinuclidine and diazabicyclo [2.2.2]octane with carbon tetrabromide

Cited by 100 publications

References 1 publication

A Theoretical Evaluation of the pKHBand Δ$H{{{\,\ominus}\hfill \atop {\rm HB}\hfill}}}$ Hydrogen‐Bond Scales of Nitrogen Bases

A Theoretical Evaluation of the pKHBand Δ$H{{{\,\ominus}\hfill \atop {\rm HB}\hfill}}}$ Hydrogen‐Bond Scales of Nitrogen Bases

σ-Hole Interactions: Perspectives and Misconceptions

Natural Abundance 15N and 13C Solid‐State NMR Chemical Shifts: High Sensitivity Probes of the Halogen Bond Geometry

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A Theoretical Evaluation of the pK_HBand Δ$H{{{\,\ominus}\hfill \atop {\rm HB}\hfill}}}$ Hydrogen‐Bond Scales of Nitrogen Bases

A Theoretical Evaluation of the pK_HBand Δ$H{{{\,\ominus}\hfill \atop {\rm HB}\hfill}}}$ Hydrogen‐Bond Scales of Nitrogen Bases

Natural Abundance ¹⁵N and ¹³C Solid‐State NMR Chemical Shifts: High Sensitivity Probes of the Halogen Bond Geometry