Study of photochemical transformations of organic azides by matrix isolation techniques and quantum chemistry

Gritsan, Nina P.

doi:10.1070/rc2007v076n12abeh003702

Cited by 65 publications

(58 citation statements)

References 204 publications

(280 reference statements)

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“…These triplet diradicals had <S 2 > values close to 2 before and after spin annihilation with large Mulliken spin densities on atoms N(3) and O(2), but of the same sign. As expected, diradicals 2T, 3T and 3T′ are nearly isoenergetic with each other, and bear some resemblance to nitroso-O-oxide (45)(46)(47), a species that can transfer an oxygen to toluene (48) or cyclize to dioxaziridine (18).…”

Section: Potential Energy Surfacessupporting

confidence: 71%

Theoretical Study of the Reaction Formalhydrazone with Singlet Oxygen. Fragmentation of the C=N Bond, Ene Reaction and Other Processes

Rudshteyn

Castillo

Ghogare

et al. 2013

Photochem & Photobiology

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Photobiologic and synthetic versatility of hydrazones has not yet been established with 1O2 as a route to commonly encountered nitrosamines. Thus, to determine whether the “parent” reaction of formalhydrazone and 1O2 leads to facile C=N bond cleavage and resulting nitrosamine formation, we have carried out CCSD(T)//DFT calculations and analyzed the energetics of the oxidation pathways. A [2 + 2] pathway occurs via diradicals and formation of 3-amino-1,2,3-dioxazetidine in a 16 kcal/mol process. Reversible addition or physical quenching of 1O2 occurs either on the formalhydrazone carbon for triplet diradicals at 2–3 kcal/mol, or on the nitrogen (N(3)) atom forming zwitterions at ~15 kcal/mol, although the quenching channel by charge-transfer interaction was not computed. The computations also predict a facile conversion of formalhydrazone and 1O2 to hydroperoxymethyl diazene in a low-barrier ‘ene’ process, but no 2-amino-oxaziridine-O-oxide (perepoxide-like) intermediate was found. A Benson-like analysis (group increment calculations) on the closed shell species are in accord with the quantum chemical results.

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Section: Potential Energy Surfacessupporting

confidence: 71%

Theoretical Study of the Reaction Formalhydrazone with Singlet Oxygen. Fragmentation of the C=N Bond, Ene Reaction and Other Processes

Rudshteyn

Castillo

Ghogare

et al. 2013

Photochem & Photobiology

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“…Acyl azides undergo Curtius rearrangement upon either thermal or photochemical activation . The light‐induced decomposition of pivaloyl azide produces both the corresponding isocyanate and acylnitrene . Physical organic chemists have explored nitrenes for several decades.…”

Section: Introductionmentioning

confidence: 99%

An ultrafast time‐resolved infrared and UV–vis spectroscopic and computational study of the photochemistry of acyl azides

Vyas

Kubicki

Luk

et al. 2012

J of Physical Organic Chem

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The photochemistry of pivaloyl, benzoyl, 4‐phenylbenzoyl, and 2‐anthroyl azides has been studied using femtosecond (fs) time‐resolved infrared (TRIR) and UV–vis spectroscopy and interpreted with the aid of computational chemistry. Density functional theory calculations revealed a significant difference in the nature of the lowest singlet excited state for these carbonyl azides. The lowest singlet excited states (S1) of p‐phenylbenzoyl and 2‐anthroyl azides are (π,π*) in nature, while the pivaloyl and benzoyl azides S1 states involve (n,π*) excitations. Nevertheless, for all acyl azides studied here, a similar, and intense, IR band at about 2100 cm−1 has been detected in the ultrafast TRIR experiments following 270 nm excitation. These bands were shifted to lower energy by about 100 cm−1 relative to the N3 stretching mode for the ground states of these azides. These 2100 cm−1 vibrational bands were assigned to the S1 states of acyl azides in agreement with density functional theory calculations. The decay of the acyl azide S1 states was described by bi‐exponential functions. The fast component was attributed to the decay of the hot S1 state and the longer component to the decay of the thermally relaxed S1 state. A strong and broad transient absorption in the 350–650 nm spectral range was observed in the fs UV–vis experiments for p‐phenylbenzoyl and 2‐anthroyl azides. The carrier of this absorption also decayed bi‐exponentially, and the time constants were in excellent agreement with those found in the fs TRIR experiments. The slow component of the S1 state decay was found to be dependent on the solvent polarity. When the lifetime of the acyl azide S1 state is substantially longer than the time constant for vibrational cooling of nascent (hot) isocyanate, the correlation between the S1 decay and isocyanate formation was clear. The 270 nm excitation populates the Sn (n ≥ 2) states of these acyl azides. It was established that a hot nitrene is produced more efficiently from both the Sn and hot S1 states than from the relaxed S1 state of these acyl azides. Thus, time‐resolved study provides direct experimental evidence that the S1 state is the precursor of nitrene only when the S1 state is pumped directly and when the S1 state lifetime is longer than the time constant of vibrational cooling of the newborn nitrene. All of these results are consistent with the data obtained recently for 2‐napththoyl azide. Copyright © 2012 John Wiley & Sons, Ltd.

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“…These defects formed upon polymerization under UV light compromise the structural integrity of the film. It is well recognized in the literature that the azide functional group exhibits susceptibility to photodecomposition, particularly under ultraviolet (UV) light exposure, forming a reactive nitrene species and emitting nitrogen gas 24–27 . For example, aromatic azides are used in light-initiated azide-amine bioconjugation reactions, where azides photodecompose to form a reactive nitrene followed by ring expansion and reaction with the amine substrate 28–29 .…”

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confidence: 99%

Blue-light activated rapid polymerization for defect-free bulk Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) crosslinked networks

et al. 2016

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Study of photochemical transformations of organic azides by matrix isolation techniques and quantum chemistry

Cited by 65 publications

References 204 publications

Theoretical Study of the Reaction Formalhydrazone with Singlet Oxygen. Fragmentation of the C=N Bond, Ene Reaction and Other Processes

Theoretical Study of the Reaction Formalhydrazone with Singlet Oxygen. Fragmentation of the C=N Bond, Ene Reaction and Other Processes

An ultrafast time‐resolved infrared and UV–vis spectroscopic and computational study of the photochemistry of acyl azides

Blue-light activated rapid polymerization for defect-free bulk Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) crosslinked networks

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