Characterization of Halogen Bonded Adducts in Solution by Advanced NMR Techniques

Ciancaleoni, Gianluca

doi:10.20944/preprints201709.0023.v1

Cited by 5 publications

(4 citation statements)

References 40 publications

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“…Finally, as spectroscopic techniques have been widely used in this field , ESR and NMR spectroscopy experiments were carried out (Supporting Information) to gain an insight into the sensitivity of the techniques toward some 4,4′‐bipyridyl XBD probes. These experiments poorly confirmed the XBD activity proving the higher sensitivity of HPLC for detection of weak stereoselective XBs in solution.…”

Section: Resultsmentioning

confidence: 99%

“…Another open issue concerns the application of XB in chiral systems, and few chiral molecules having σ‐holes on halogens as recognition sites were described recently . Perfluorinated and cationic N‐heterocyclic substructures (Figure B) are able to activate potential σ‐hole sites and generate strong XBs, which are detectable by means of a variety of spectroscopic techniques, of which NMR spectroscopy is the most widely used . On the other hand, iodinated and brominated neutral XB donors (XBDs) lacking perfluorination are needed for real‐life applications in drug design and supramolecular chemistry .…”

Section: Introductionmentioning

confidence: 99%

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Polysaccharide‐based chiral stationary phases as halogen bond acceptors: A novel strategy for detection of stereoselective σ‐hole bonds in solution

Peluso

Mamane

Dallocchio

et al. 2018

J of Separation Science

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In the last few years, halogen bonds have been exploited in a variety of research areas both in the solid state and in solution. Nevertheless, several factors make formation and detection of halogen bonds in solution challenging. Moreover, to date, few chiral molecules containing electrophilic halogens as recognition sites have been reported. Recently, we described the first series of halogen-bond-driven enantioseparations performed on cellulose tris(3,5-dimethylphenylcarbamate) by high-performance liquid chromatography. Herein the performances of amylose tris(3,5-dimethylphenylcarbamate) as halogen bond acceptor were also investigated and compared with respect to cellulose tris(3,5-dimethylphenylcarbamate). With the aim to explore the effect of polysaccharide backbone on the enantioseparations, the thermodynamic parameters governing the halogen-dependent enantioseparations on both cellulose and amylose polymers were determined by a study at variable temperature and compared. Molecular dynamics were performed to model the halogen bond in polysaccharide-analyte complexes. Chiral halogenated 4,4'-bipyridines were used as test compounds (halogen bond donors). On this basis, a practical method for detection of stereoselective halogen bonds in solution was developed, which is based on the unprecedented use of high-performance liquid chromatography as technical tool with polysaccharide polymers as molecular probes (halogen bond acceptors). The analytical strategy showed higher sensitivity for the detection of weak halogen bonds.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polysaccharide‐based chiral stationary phases as halogen bond acceptors: A novel strategy for detection of stereoselective σ‐hole bonds in solution

Peluso

Mamane

Dallocchio

et al. 2018

J of Separation Science

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“…14,15 In order to better describe the XB adduct in solution, it is important to use independent techniques that yield comparable information from a different point of view, such as nuclear Overhauser effect- [16][17][18] and diffusion- 15,19,20 based NMR techniques. 21 The coupling of different techniques, in fact, makes the picture clearer and more reliable.…”

Section: Introductionmentioning

confidence: 99%

Cooperativity between hydrogen- and halogen bonds: the case of selenourea

Ciancaleoni

2018

Phys. Chem. Chem. Phys.

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A combined experimental/computational study of cooperativity between halogen-(XB) and hydrogen bonding (HB) is presented. Selenourea (SeU) has been chosen due to its ability to act at the same time as an XB acceptor toward I(CF2)5CF3 (I1) through the two lone pairs on the selenium atom, and as a HB donor to the benzoate anion through its two amino moieties. All equilibrium constants have been estimated using either diffusion NMR and NMR titration techniques. Experimental results demonstrate that the -NH2anion interaction strongly enhances the SeI one of about one order of magnitude (in terms of formation constant of the adduct), whereas DFT results rationalize such results revealing that the presence of a HB between the benzoate and SeU strongly polarizes the latter, enhancing the negative partial charge on selenium and, consequently, its Lewis basicity and its XB acceptor properties.

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“…67 In fact, by means of the latter, the diffusion coefficient (D t ) of the species under examination can be measured, and aggregation processes can be evaluated, even if very weak or involving many species. 68,69 The hydrodynamic volume of SeU (V H ) which can be derived from the value of D t 70 goes from 176 to 205 Å 3 in the absence and presence of an excess of TEAPF 6 (Table 1). The corresponding association constant (K PF 6 ,SeU ) is 2.0 ± 0.3 M −1 .…”

Section: ■ Introductionmentioning

confidence: 99%

Interplay between Gold(I)-Ligand Bond Components and Hydrogen Bonding: A Combined Experimental/Computational Study

2019

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The influence of weak interactions on the donation/back-donation bond components in the complex [(NHC)Au( SeU )] + (NHC = N-heterocyclic carbene; SeU = selenourea) has been studied by coupling experimental and theoretical techniques. In particular, NMR 1 H and pulsed-field gradient spin-echo titrations allowed us to characterize the hydrogen bond (HB) between the −NH 2 moieties of SeU and the anions PF 6 – and ClO 4 – , whereas 77 Se NMR spectroscopy allowed us to characterize the Au–Se bond. Theoretically, the Au–Se and Au–C orbital interactions have been decomposed using the natural orbital for the chemical valence framework and the bond components quantified through the charge displacement analysis. This methodology provides the quantification of the Dewar–Chatt–Duncanson (DCD) components for the Au–C and Au–Se bonds in the absence and presence of the second-sphere HB. The results presented here show that the anion has a dual mode action: it modifies the conformation of the cation by ion pairing (and this already influences the DCD components) and it induces new polarization effects that depend on the relative anion/cation relative orientation. The perchlorate polarizes SeU , enhancing the Se → Au σ donation and the Au → C back-donation and depressing the C → Au σ donation. On the contrary, the hexafluorophosphate depresses both the Se → Au and C → Au σ donations.

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Characterization of Halogen Bonded Adducts in Solution by Advanced NMR Techniques

Cited by 5 publications

References 40 publications

Polysaccharide‐based chiral stationary phases as halogen bond acceptors: A novel strategy for detection of stereoselective σ‐hole bonds in solution

Polysaccharide‐based chiral stationary phases as halogen bond acceptors: A novel strategy for detection of stereoselective σ‐hole bonds in solution

Cooperativity between hydrogen- and halogen bonds: the case of selenourea

Interplay between Gold(I)-Ligand Bond Components and Hydrogen Bonding: A Combined Experimental/Computational Study

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