Reaction of the 4-Biphenylnitrenium Ion with 4-Biphenyl Azide to Produce a 4,4′-Azobisbiphenyl Stable Product: A Time-Resolved Resonance Raman and Density Functional Theory Study

Xue, Jingling; Du, Yong; Guan, Xiangguo; Guo, Zhen; Phillips, David Lee

doi:10.1021/jp805353q

Cited by 9 publications

(7 citation statements)

References 42 publications

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“…1 mM), with loss of N 2 , to yield cis - and trans -4,4′-azobisbiphenyl 24 (Scheme 6). 40 A similar reaction of 11 with N 3 - would yield the diazene 25 . Aryldiazenes are known to spontaneously decompose into the corresponding arene with loss of N 2 41.…”

Section: Results and Discusionmentioning

confidence: 99%

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Characterization of the 4-(Benzothiazol-2-yl)phenylnitrenium Ion from a Putative Metabolite of a Model Antitumor Drug

et al. 2010

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The 4-(benzothiazol-2-yl)phenylnitrenium ion 11 is generated from hydrolysis or photolysis of O-acetoxy-N-(4-(benzothiazol-2-yl)phenyl)hydroxylamine 8, a model metabolite of 2-(4-aminophenyl)benzothiazole 1 and its ring substituted derivatives that are being developed for a variety of medicinal applications including anti-tumor, anti-bacterial, anti-fungal, and imaging agents. Previously we showed that 11 had an aqueous solution lifetime of 530 ns, similar to the 560 ns lifetime of the 4-biphenylylnitrenium ion 12 derived from the well known chemical carcinogen 4-aminobiphenyl. We now show that the analogy between these two cations extends well beyond their lifetimes. The initial product of hydration of 11 is the quinolimine 16 which can be detected as a long-lived reactive intermediate that hydrolyzes in a pH-dependent manner into the final hydrolysis product, the quinol 15. This hydrolysis behavior is equivalent to that previously described for a large number of ester metabolites of carcinogenic arylamines including 4-aminobiphenyl. The major azide trapping product (90% of azide products) of 11, 20, is generated by substitution on the carbons ortho to the nitrenium ion center of 11. This product is a direct analogue of the major azide adducts, such as 22, generated from trapping of the nitrenium ions of carcinogenic arylamines. The azide/solvent selectivity for 11, kaz/ks, is also nearly equivalent to that of 12. A minor product of the reaction of 11 with N3-, 21, contains no azide functionality, but may be generated by a process in which N3- attacks 11 at the nitrenium ion center with loss of N2 to generate a diazene 25 that subsequently decomposes into 21 with loss of another N2. The adduct derived from attack of 2′-deoxyguanosine (d-G) on 11, 28, is a familiar C-8 adduct of the type generated from the reaction of d-G with a wide variety of arylnitrenium ions derived from carcinogenic arylamines. The rate constant for reaction of d-G with 11, kd-G, is very similar to that observed for the reaction of d-G with 12. The similar lifetimes and chemical reactivities of 11 and 12 can be rationalized by B3LYP/6-31G(d) calculations on the two ions that show that they are of nearly equivalent stability relative to their respective hydration products. The calculations also help to rationalize the different regiochemistry observed for the reaction of N3- with 11 and its oxenium ion analogue, 13. Since 8 is the likely active metabolite of 1 and a significant number of derivatives of 1 are being developed as pharmaceutical agents, the similarity of the chemistry of 11 to that of carcinogenic arylnitrenium ions is of considerable importance. Consideration should be given to this chemistry in continued development of pharmaceuticals containing the 2-(4-aminophenyl)benzothiazole moiety.

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Section: Results and Discusionmentioning

confidence: 99%

“…Recently, Phillips and co-workers have shown that photolytically generated 12 reacts with 4-biphenyl azide 23 at relatively high concentrations of 23 (ca. 1 mM), with loss of N 2 , to yield cis - and trans -4,4′-azobisbiphenyl 24 (Scheme ) . A similar reaction of 11 with N 3 − would yield the diazene 25 .…”

Section: Results and Discusionmentioning

confidence: 99%

Characterization of the 4-(Benzothiazol-2-yl)phenylnitrenium Ion from a Putative Metabolite of a Model Antitumor Drug

et al. 2010

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“…Comparison of experimental vibrational frequencies to those predicted from density functional theory (DFT) or ab initio calculations for probable intermediates has been successfully employed to identify and assign time-resolved infrared (TR-IR) and time-resolved resonance Raman (TR 3 ) spectra to arylnitrenium ions, arylnitrenes, and arylnitrene photoproducts. ,,,,− We shall use similar methodology to help assign the four species observed in the TR 3 spectra of Figures and . DFT calculations were performed to test these possibilities.…”

Section: Resultsmentioning

confidence: 99%

“…The experimental apparatus and methods used for the ns-TR 3 experiments have been detailed elsewhere, ,− so only a brief account will be given here. The fourth harmonic of a Nd:YAG nanosecond pulsed laser system provided the 266 nm laser as pump and 319.9 nm as probe (the third anti-Stokes hydrogen Raman shifted laser line of the 532 nm second harmonic) wavelengths used in the ns-TR 3 experiments.…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

Time-Resolved Resonance Raman and Computational Investigation of the Influence of 4-Acetamido and 4-N-Methylacetamido Substituents on the Chemistry of Phenylnitrene

Xue

Vyas

et al. 2011

J. Phys. Chem. A

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A time-resolved resonance Raman (TR(3)) and computational investigation of the photochemistry of 4-acetamidophenyl azide and 4-N-methylacetamidophenyl azide in acetonitrile is presented. Photolysis of 4-acetamidophenyl azide appears to initially produce singlet 4-acetamidophenylnitrene which undergoes fast intersystem crossing (ISC) to form triplet 4-acetamidophenylnitrene. The latter species formally produces 4,4'-bisacetamidoazobenzene. RI-CC2/TZVP and TD-B3LYP/TZVP calculations predict the formation of the singlet nitrene from the photogenerated S(1) surface of the azide excited state. The triplet 4-acetamidophenylnitrene and 4,4'-bisacetamidoazobenzene species are both clearly observed on the nanosecond to microsecond time-scale in TR(3) experiments. In contrast, only one species can be observed in analogous TR(3) experiments after photolysis of 4-N-methylacetamidophenyl azide in acetonitrile, and this species is tentatively assigned to the compound resulting from dimerization of a 1,2-didehydroazepine. The different photochemical reaction outcomes for the photolysis of 4-acetamidophenyl azide and 4-N-methylacetamidophenyl azide molecules indicate that the 4-acetamido group has a substantial influence on the ISC rate of the corresponding substituted singlet phenylnitrene, but the 4-N-methylacetamido group does not. CASSCF analyses predict that both singlet nitrenes have open-shell electronic configurations and concluded that the dissimilarity in the photochemistry is probably due to differential geometrical distortions between the states. We briefly discuss the probable implications of this intriguing substitution effect on the photochemistry of phenyl azides and the chemistry of the related nitrenes.

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“…The resonance Raman (RR) and nanosecond time-resolved resonance Raman (ns-TR 3 ) experiments were done using an experimental apparatus and methods discussed in detail previously, [16][17][18][19][20][21] so only a brief description will be given here. The pump laser pulse with a wavelength of 266 nm generated from the fourth harmonic of a Nd:YAG nanosecond pulsed laser and a 355-nm probe laser pulse from the third harmonic of the second laser were employed in the TR 3 experiments.…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

Time‐resolved spectroscopic and density functional theory investigation of the photochemistry of suprofen

Zhu

Xue

et al. 2014

J Raman Spectroscopy

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The photochemistry of suprofen (SPF) was investigated by femtosecond transient absorption (fs-TA), resonance Raman (RR) and nanosecond time-resolved resonance Raman (ns-TR 3 ) spectroscopic methods to gain additional information so as to better elucidate the possible photochemical reaction mechanism of suprofen in several different solvents. In neat acetonitrile (MeCN), the fs-TA and ns-TR 3 experimental data indicated that the lowest lying excited singlet state S 1 (nπ*) underwent an efficient intersystem crossing process (ISC) to the excited triplet state T 3 (ππ*), followed by an internal conversion (IC) process to T 1 (ππ*). In the aqueous solution, a triplet biradical species ( 3 ETK-1) was obtained as the product of a decarboxylation process from triplet suprofen anion ( 3 SPF À ) and the reaction rate of the decarboxylation process was determined by the concentration of H 2 O. A protonation process for 3 ETK-1 leads to formation of a neutral species ( 3 ETK-3) that was directly observed by ns-TR 3 spectra, then this 3 ETK-3 species decayed via ISC process to generate final product.

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Reaction of the 4-Biphenylnitrenium Ion with 4-Biphenyl Azide to Produce a 4,4′-Azobisbiphenyl Stable Product: A Time-Resolved Resonance Raman and Density Functional Theory Study

Cited by 9 publications

References 42 publications

Characterization of the 4-(Benzothiazol-2-yl)phenylnitrenium Ion from a Putative Metabolite of a Model Antitumor Drug

Characterization of the 4-(Benzothiazol-2-yl)phenylnitrenium Ion from a Putative Metabolite of a Model Antitumor Drug

Time-Resolved Resonance Raman and Computational Investigation of the Influence of 4-Acetamido and 4-N-Methylacetamido Substituents on the Chemistry of Phenylnitrene

Time‐resolved spectroscopic and density functional theory investigation of the photochemistry of suprofen

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