Title: Thermodynamics and Spectroscopy of Halogen- and Hydrogen-Bonded Complexes of Haloforms with Aromatic and Aliphatic Amines
Similarities and differences of halogen and hydrogen bonding were explored via UV–Vis and 1H NMR measurements, X-ray crystallography and computational analysis of the associations of CHX3 (X=I, Br, Cl) with aromatic (tetramethyl-p-phenylenediamine) and aliphatic (4-diazabicyclo[2,2,2]octane) amines. When the polarization of haloforms was taken into account, the strengths of these complexes followed the same correlation with the electrostatic potentials on the surfaces of the interacting atoms. However, their spectral properties were quite distinct. While the halogen-bonded complexes showed new intense absorption bands in the UV–Vis spectra, the absorptions of their hydrogen-bonded analogues were close to the superposition of the absorption of reactants. Additionally, halogen bonding led to a shift in the NMR signal of haloform protons to lower ppm values compared with the individual haloforms, whereas hydrogen bonding of CHX3 with aliphatic amines resulted in a shift in the opposite direction. The effects of hydrogen bonding with aromatic amines on the NMR spectra of haloforms were ambivalent. Titration of all CHX3 with these nucleophiles produced consistent shifts in their protons’ signals to lower ppm values, whereas calculations of these pairs produced multiple hydrogen-bonded minima with similar structures and energies, but opposite directions of the NMR signals’ shifts. Experimental and computational data were used for the evaluation of formation constants of some halogen- and hydrogen-bonded complexes between haloforms and amines co-existing in solutions. more »« less
Loy, Cody; Holthoff, Jana M.; Weiss, Robert; Huber, Stefan M.; Rosokha, Sergiy V.
(, Chemical Science)
null
(Ed.)
Halogen-bonded (XB) complexes between halide anions and a cyclopropenylium-based anionic XB donor were characterized in solution for the first time. Spontaneous formation of such complexes confirms that halogen bonding is sufficiently strong to overcome electrostatic repulsion between two anions. The formation constants of such “anti-electrostatic” associations are comparable to those formed by halides with neutral halogenated electrophiles. However, while the latter usually show charge-transfer absorption bands, the UV-Vis spectra of the anion–anion complexes examined herein are determined by the electronic excitations within the XB donor. The identification of XB anion–anion complexes substantially extends the range of the feasible XB systems, and it provides vital information for the discussion of the nature of this interaction.
Lambert, Ethan C.; Williams, Ashley E.; Fortenberry, Ryan C.; Hammer, Nathan I.
(, Physical Chemistry Chemical Physics)
The potential formation of halogen bonded complexes between a donor, heptafluoro-2-iodopropane (HFP), and the three acceptor heterocyclic azines (azabenzenes: pyridine, pyrimidine, and pyridazine) is investigated herein through normal mode analysis via Raman spectroscopy, density functional theory, and natural electron configuration analysis. Theoretical Raman spectra of the halogen bonded complexes are in good agreement with experimental data providing insight into the Raman spectra of these complexes. The exhibited shifts in vibrational frequency of as high as 8 cm −1 for each complex demonstrate, in conjunction with NEC analysis, significant evidence of charge transfer from the halogen bond acceptor to donor. Here, an interesting charge flow mechanism is proposed involving the donated nitrogen lone pair electrons pushing the dissociated fluorine atoms back to their respective atoms. This mechanism provides further insight into the formation and fundamental nature of halogen bonding and its effects on neighboring atoms. The present findings provide novel and deeper characterization of halogen bonding with applications in supramolecular and organometallic chemistry.
Curran, T. P.; Lawrence, A. P.; Murtaugh, T. S.; Ji, W.; Pokharel, N.; Gober, C. B.; Suitor, J.
(, Journal of organometallic chemistry)
In exploring the conformational behavior of cyclic tungsten bis-alkyne complexes, two dialkynylamides (14a and 14c) and two dialkynylesters (14b and 14d) derived from 1,1’-ferrocenedicarboxylic acid were prepared. They were subsequently reacted with W(CO)3(dmtc)2 to yield the desired cyclic tungsten bis-alkyne complexes 8-11. In the cyclization of 14a to yield 8 a dimeric macrocyclic complex, 15, featuring two tungsten bis-alkyne complexes in the ring, also was isolated. The conformational behavior of these complexes was assessed by analysis of the 1H NMR resonances for the alkyne hydrogens, which appear around 11 ppm. The spectra for complexes 10, 11 and 15 show multiple singlets of varying integrations for these protons, while the spectra for complexes 8 and 9 show only two resonances of equal integration for the alkyne hydrogens. The spectra for 8 and 9 changed very little when examined at higher temperatures, indicating that the solution conformation is robust. A ROESY spectrum was obtained for 8. It did not show any crosspeaks between the two alkyne hydrogens. The NMR data shows that the alkyne ligands in 10, 11 and 15 are able to rotate about the tungsten-alkyne bond; these complexes adopted several different solution conformations relating to syn and anti arrangements of the alkyne ligands. In contrast, complexes 8 and 9 adopt only one solution conformation, and the alkyne ligands in these species do not rotate about the tungsten-alkyne bond. The NMR spectra for 8 and 9 also show that these complexes are asymmetric. The 1H NMR spectra for 8 and 9 show that each hydrogen atom has its own unique resonance in the 1H NMR spectrum. There are 8 resonances for the 8 Cp protons, 4 resonances for the methylene protons, 2 resonances for the alkyne protons, and in the case of 8, 2 resonances for the NH protons. The two NH protons on complex 8 were found to have widely different chemical shifts. A DMSO titration was performed and it showed that one of the two NH protons in 8 is involved in an intramolecular hydrogen bond. Given that the diester 9 adopts a similar conformation as the diamide 8, this intramolecular hydrogen bond appears to result from the conformation imposed by cyclization of the ring system. Overall, the data show that the ring system for 8 and 9 provides a unique, rigid, robust, and air stable cyclic molecule where the alkyne ligands are limited to one orientation, presumably the syn orientation. The lack of mobility for the alkyne ligands limits the cyclic molecule to only one solution conformation. Complexes 8 and 9 are the first reported examples of cyclic tungsten bis-alkyne complexes that only adopt a single, robust conformation in solution.
Ujah, Victoria C; AbuSalim, Deyaa I; Lash, Timothy D
(, The Journal of Organic Chemistry)
A series of porphyrin analogues with fused 1,10-phenanthroline units were synthesized. The proton NMR spectra for phenanthroline-fused heteroporphyrins showed significantly upfield shifted meso-proton resonances compared to related porphyrinoid systems and the peaks corresponding to alkyl substituents directly attached to these macrocycles were also observed further upfield. These results indicate that the presence of the phenanthroline unit leads to reduced diatropicity, but the internal NH resonance was also further upfield, a result that is inconsistent with this interpretation. A phenanthrene-fused carbaporphyrin gave an unexpectedly upfield singlet for the internal C−H at nearly −9 ppm, while the NH protons appeared at −6.8 ppm. These unusual chemical shifts again imply enhanced diatropicity but the reduced downfield shifts for the external protons indicates that the aromatic ring current has been significantly reduced. Similar results were obtained for phenanthroline-fused oxybenzi- and oxypyriporphyrins. Detailed analyses of the spectroscopic properties for these systems are reported and protonation studies were conducted. The conjugation pathways and aromatic properties were computationally analyzed using nucleus independent chemical shifts (NICS) and anisotropy of induced current density plots.
Rammer, Megan_L; Gonnering, Emily_R; Driscoll, Zakarias_L; Vang, Herh_G; Bosch, Eric; Bowling, Nathan_P
(, European Journal of Organic Chemistry)
Abstract A molecular rotor is created when a 2,1,3‐benzothiadiazole rotator is incorporated into a rigid arylene ethynylene framework supported by pyridine coordination to a metal (Ag+or PdCl2) guest. Comparisons to a similarly sized naphthyl rotator via1H NMR spectroscopy provide insights into the movement of these bicyclic rotators relative to the rigid stator framework. Chemical shift increases of 0.3 ppm, or more, upon metal complexation are consistent with through‐space interaction of the central arene with a bound PdCl2guest. Further study via X‐ray crystallography illustrates that rotation of the 2,1,3‐benzothiadiazole unit in the solid state is likely hampered by relatively strong chalcogen bonding (N⋅⋅⋅S distance of 2.93 Å), forming 2S‐2N squares between benzothiadiazoles of neighboring complexes. Strong π–π interactions (3.29–3.36 Å) between neighboring complexes likewise restrict solid‐state rotation of the potential benzothiadiazole rotator. Modest changes to UV–vis spectra upon metal coordination suggest that electronic properties are mostly independent of stator configuration.
Adeniyi, Emmanuel, Grounds, Olivia, Stephens, Zachary, Zeller, Matthias, and Rosokha, Sergiy V. Thermodynamics and Spectroscopy of Halogen- and Hydrogen-Bonded Complexes of Haloforms with Aromatic and Aliphatic Amines. Retrieved from https://par.nsf.gov/biblio/10432620. Molecules 27.18 Web. doi:10.3390/molecules27186124.
Adeniyi, Emmanuel, Grounds, Olivia, Stephens, Zachary, Zeller, Matthias, & Rosokha, Sergiy V. Thermodynamics and Spectroscopy of Halogen- and Hydrogen-Bonded Complexes of Haloforms with Aromatic and Aliphatic Amines. Molecules, 27 (18). Retrieved from https://par.nsf.gov/biblio/10432620. https://doi.org/10.3390/molecules27186124
Adeniyi, Emmanuel, Grounds, Olivia, Stephens, Zachary, Zeller, Matthias, and Rosokha, Sergiy V.
"Thermodynamics and Spectroscopy of Halogen- and Hydrogen-Bonded Complexes of Haloforms with Aromatic and Aliphatic Amines". Molecules 27 (18). Country unknown/Code not available. https://doi.org/10.3390/molecules27186124.https://par.nsf.gov/biblio/10432620.
@article{osti_10432620,
place = {Country unknown/Code not available},
title = {Thermodynamics and Spectroscopy of Halogen- and Hydrogen-Bonded Complexes of Haloforms with Aromatic and Aliphatic Amines},
url = {https://par.nsf.gov/biblio/10432620},
DOI = {10.3390/molecules27186124},
abstractNote = {Similarities and differences of halogen and hydrogen bonding were explored via UV–Vis and 1H NMR measurements, X-ray crystallography and computational analysis of the associations of CHX3 (X=I, Br, Cl) with aromatic (tetramethyl-p-phenylenediamine) and aliphatic (4-diazabicyclo[2,2,2]octane) amines. When the polarization of haloforms was taken into account, the strengths of these complexes followed the same correlation with the electrostatic potentials on the surfaces of the interacting atoms. However, their spectral properties were quite distinct. While the halogen-bonded complexes showed new intense absorption bands in the UV–Vis spectra, the absorptions of their hydrogen-bonded analogues were close to the superposition of the absorption of reactants. Additionally, halogen bonding led to a shift in the NMR signal of haloform protons to lower ppm values compared with the individual haloforms, whereas hydrogen bonding of CHX3 with aliphatic amines resulted in a shift in the opposite direction. The effects of hydrogen bonding with aromatic amines on the NMR spectra of haloforms were ambivalent. Titration of all CHX3 with these nucleophiles produced consistent shifts in their protons’ signals to lower ppm values, whereas calculations of these pairs produced multiple hydrogen-bonded minima with similar structures and energies, but opposite directions of the NMR signals’ shifts. Experimental and computational data were used for the evaluation of formation constants of some halogen- and hydrogen-bonded complexes between haloforms and amines co-existing in solutions.},
journal = {Molecules},
volume = {27},
number = {18},
author = {Adeniyi, Emmanuel and Grounds, Olivia and Stephens, Zachary and Zeller, Matthias and Rosokha, Sergiy V.},
}
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