Synthesis and spectra of N-15 labelled phenylazides

Lešetický, L.; Barth, Richard C.; Němec, Ivan; Štícha, Martin; Tišlerová, Iva

doi:10.1007/s10582-003-0101-0

Cited by 14 publications

(19 citation statements)

References 12 publications

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“…Asymmetric azide stretching is usually observed at wavenumbers between 2080 cm −1 and 2170 cm −1 , and we therefore assign the band at 2114 cm −1 to the azide moiety. The structure of the band is attributed to a Fermi resonance 10. Carbonyl stretching of the carboxylate moiety is expected between 1705 cm −1 and 1730 cm −1 ; carbonyl stretching of the carbamate moiety (amide I) is expected between 1705 cm −1 and 1722 cm −1 9.…”

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confidence: 90%

Ultrafast Hopping from Band to Band: Assigning Infrared Spectra based on Vibrational Energy Transfer

Müller‐Werkmeister

Lerch

et al. 2013

Angew Chem Int Ed

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Infrared spectroscopy is widely used in fundamental and applied chemical research. Applications cover tasks in analytical chemistry, such as process monitoring or product identification, [1] as well as cutting-edge studies elucidating reaction mechanisms [2] or resolving ultrafast biomolecular dynamics and functions. [3] Typically, analysis of an IR spectrum starts with assignment, that is, with establishing a connection between the bands observed in the spectrum and the moieties of the molecule that are involved in the corresponding vibrations. For small molecules, vibrations often can be assigned based on experience, aided by databases that list functional groups and the typical wavenumber range of their absorption bands. However, the database approach quickly becomes unfeasible if several groups are present that cause vibrations in the same wavenumber range or if a certain group is present several times in a molecule. A way to obtain assignment information in such cases is isotope labeling, which might involve complex synthesis. Very frequently, quantum-chemical computations are used for assignment. However, even for seemingly simple cases, contradicting results can be obtained from different computational methods, as illustrated by the results presented herein. Furthermore, there are cases where the computation of vibrational modes can be intrinsically difficult, such as excited states or reaction mixtures containing unknown species. A broadly applicable experimental approach to aid assignment is therefore highly desirable.Herein we show how time-dependent infrared pumpprobe spectroscopy allows assignment problems to be solved. For this purpose, a vibration of the molecule is selectively excited using an infrared excitation pulse with narrow bandwidth and the response of the other vibrations is investigated by a delayed probe pulse. The initially excited vibration relaxes; low-frequency modes become excited, and intramolecular vibrational energy transfer (VET) across the molecule occurs between low-frequency modes. [4] Throughbond transfer rates of 2.6-5.5 ps À1 have been reported for different molecules. [4b, 5] The high-frequency vibrations investigated herein are anharmonically coupled to the lowfrequency modes and respond to VET by red-shifting. [6] Because transfer times correlate with through-bond distances, [4b, 5, 7] the order in which the bands in the spectrum respond to the initial excitation reflects the distance between the vibrating groups in the molecule. This is critically important information for band assignment.As an example for the broadly applicable method of VETbased assignment, we chose the artificial amino acid p-azidol-phenylalanine, [8] which is used as a protein label for IR spectroscopy (Figure 1). We investigated the boc-protected form (abbreviated N 3 Phe), thereby adding a peptide bond to the model system. Figure 1 shows the FTIR absorption spectrum. Referring to a database of group frequencies, [9] as is typically done for IR band assignment, we expect several bands in the w...

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confidence: 90%

Ultrafast Hopping from Band to Band: Assigning Infrared Spectra based on Vibrational Energy Transfer

Müller‐Werkmeister

Lerch

et al. 2013

Angew Chem Int Ed

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“…However, this accuracy in 15 N CS calculations is completely unacceptable for investigations of triazides 1–7 , in which the N α , N β and N γ atoms of nonequivalent azido groups display quite similar 15 N CS . To test the performance of different DFT approaches to calculations of 15 N CS in azides, azidobenzene 8 , diazidotoluene 9 and cyanuryltriazide 10 with 15 N NMR spectra described in the literature were chosen as model systems. The most suitable DFT approach was then used for the assignment of 15 N CS in triazides 1–7 .…”

Section: Introductionmentioning

confidence: 99%

¹⁵N NMR spectra and reactivity of 2,4,6‐triazidopyridines, 2,4,6‐triazidopyrimidine and 2,4,6‐triazido‐s‐triazine

Чапышев

Ushakov

Chernyak

2013

Magnetic Reson in Chemistry

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2,4,6-Triazido-s-triazine, 2,4,6-triazidopyrimidine and six different 2,4,6-triazidopyridines were studied by (15)N NMR spectroscopy. The assignment of signals in the spectra was performed using the gauge-independent atomic orbital (GIAO)-Tao-Perdew-Staroverov-Scuseria exchange-correlation functional (TPSS)h/6-311+G(d,p) calculations on the M06-2X/6-311+G(d,p) optimized molecular geometries. The Truhlar and coworkers' continuum solvation model called SMD was applied to treat solvent effects. With this approach, the root mean square error in estimations of the (15)N chemical shifts for the azido groups was just 1.9 ppm. It was shown that the different reactivity of the α- and γ-azido groups in pyridines correlates well with the chemical shifts of the Nα signals of these groups. Of two nonequivalent azido groups of azines, the azido group with the most shielded Nα signal is the most electron-deficient and reactive toward electron-rich reagents. By contrast, the azido group of azines with the most deshielded Nα signal is the most reactive toward electron-poor reagents.

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“…into dinitrogen and a mesityl radical . To test our hypothesis that 5 is formed by γ‐N abstraction from MesN 3 , we reacted 1 with terminally 15 N‐labeled mesityl azide, MesNN 15 N, which was synthesized following a procedure analogous to that used by Lešetický to synthesize PhNN 15 N . To determine whether the reaction of 1 with MesNN 15 N in THF produced ( tbs L)Cr 3 ( μ 3 ‐ 15 N) ( 5‐ 15 N ), the product of the reaction was decomposed using HCl to produce ammonium chloride and then treated with base to liberate ammonia, which was vacuum transferred into a solution of HCl in diethyl ether.…”

Section: Figurementioning

confidence: 99%

Ligand‐Based Control of Single‐Site vs. Multi‐Site Reactivity by a Trichromium Cluster

et al. 2019

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The trichromium cluster ( tbs L)Cr 3 (thf) ([ tbs L] 6À = [1,3,5-C 6 H 9 (NC 6 H 4 -o-NSi t BuMe 2 ) 3 ] 6À )exhibits steric-and solvation-controlled reactivity with organic azides to form three distinct products:r eaction of ( tbs L)Cr 3 (thf) with benzyl azide forms as ymmetrized bridging imido complex ( tbs L)Cr 3 (m 3 -NBn);reaction with mesityl azide in benzene affords at erminally bound imido complex ( tbs L)Cr 3 (m 1 -NMes);w hereas the reaction with mesityl azide in THF leads to terminal N-atom excision from the azide to yield the nitride complex ( tbs L)Cr 3 -(m 3 -N). The reactivity of this complex demonstrates the ability of the cluster-templating ligand to produce aw ell-defined polynuclear transition metal cluster that can access distinct single-site and cooperative reactivity controlled by either substrate steric demands or reaction media.

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Synthesis and spectra of N-15 labelled phenylazides

Cited by 14 publications

References 12 publications

Ultrafast Hopping from Band to Band: Assigning Infrared Spectra based on Vibrational Energy Transfer

Ultrafast Hopping from Band to Band: Assigning Infrared Spectra based on Vibrational Energy Transfer

¹⁵N NMR spectra and reactivity of 2,4,6‐triazidopyridines, 2,4,6‐triazidopyrimidine and 2,4,6‐triazido‐s‐triazine

Ligand‐Based Control of Single‐Site vs. Multi‐Site Reactivity by a Trichromium Cluster

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Synthesis and spectra of N-15 labelled phenylazides

Cited by 14 publications

References 12 publications

Ultrafast Hopping from Band to Band: Assigning Infrared Spectra based on Vibrational Energy Transfer

Ultrafast Hopping from Band to Band: Assigning Infrared Spectra based on Vibrational Energy Transfer

15N NMR spectra and reactivity of 2,4,6‐triazidopyridines, 2,4,6‐triazidopyrimidine and 2,4,6‐triazido‐s‐triazine

Ligand‐Based Control of Single‐Site vs. Multi‐Site Reactivity by a Trichromium Cluster

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¹⁵N NMR spectra and reactivity of 2,4,6‐triazidopyridines, 2,4,6‐triazidopyrimidine and 2,4,6‐triazido‐s‐triazine