An MC-SCF/MP2 Study of the Photochemistry of 2,3-Diazabicyclo[2.2.1]hept-2-ene:  Production and Fate of Diazenyl and Hydrazonyl Biradicals

Yamamoto, Naoko; Olivucci, Massimo; Celani, Paolo; Bernardi, Fernando; Robb, Michael A.

doi:10.1021/ja971733v

Cited by 64 publications

(66 citation statements)

References 52 publications

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“…The HTs of azo dyes bearing a keto group at the O13 position have a strong tendency to adopt the enol structure (due to a pK a shift [57,58]), resulting in ATs in the excited states. Photochemical and thermal decompositions of photoinduced radicals derived from cyclic azoalkanes in the liquid phase were shown to occur in the excited and ground states with large rate constants [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76].) (The photochemistry of azo groups has been extensively studied for azoalkanes, including thermal reactions between photoinduced radicals.…”

Section: Short Summary Of the Analysis In The Liquid Phasesmentioning

confidence: 99%

Radical mechanism of azo cleavage for monoazo reactive dyes, a QSPR study: the similarity between photoreduction on polyamide substrates and thermal reduction in aqueous dithionite solutions

Okada¹,

Hihara

Morita

2016

Coloration Technology

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The same radical mechanism occurs in reductive azo cleavage via monohydrogenated radicals generated as the starting reactants in photo-and thermal (by dithionite) reduction on a nylon 6 substrate and in aqueous and alcoholic solutions. The rates of photo-and thermal azo cleavage in the solid and liquid phases have been thermochemically analysed by calculating the heats of formation of the reactants, intermediates, and products for (1) intramolecular hydrogen transfer (self-decomposition via rearrangement) in the photo-and radically induced hydrazinyl radicals as well as for (2) the disproportionation (redox reaction) between the radicals via a molecular orbital method. The rates of reductive fading (or azo cleavage) are controlled by the heats of reaction via reaction pathways (1) and (2) as well as by rearrangement, depending on the reaction system. Photoreduction of these dyes on polyamide generated the same end productsdiazo components and iminooxoquinones from the coupling componentas the products of thermal reduction in aqueous sodium dithionite and of photoreduction in the liquid phase. Photofading on polyamide substrates owing to continuous irradiation is controlled by three factors: the quantum yield of photoinduced hydrazinyl radicals, its rearrangement processes, and the heats of reaction for the thermal azo cleavage reactions via the two pathways. These factors may become molecular descriptors that correlate the rates of fading with molecular structures. The present study may become an introductory trial to construct quantitative structure-property relationship modelling for reduction-fast azo dyes. Coloration Technology Society of Dyers and ColouristsAbbreviations and symbols AC = azo cleavage; AT = azo tautomer; HT = hydrazone tautomer; PA = polyamide 6; QSPR = quantitative structure-property relationship; VS = vinylsulphonyl; K PA and K PET = initial rates of fading on PA and PET respectively. Radical moieties attached to or contained in a dye molecule: (N11) = N11-hydrazinyl dye radical; (N12) = N 12-hydrazinyl dye radical; (MHN) = monohydrogenated dye radical. In order to distinguish clearly the position and the position-centred radical, only the Ni-and Oicentred monohydrogenated dye radicals are described, respectively, as (Ni) and (Oi) in parentheses in the text, scheme, chemical equations, and tables; (MHN) is their general name; i describes the number of atoms including carbon: 2 1The numbering of atoms used in molecular orbital (MO) calculations is different from the normal chemical nomenclature (see the 'MO calculations' section).

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Section: Short Summary Of the Analysis In The Liquid Phasesmentioning

confidence: 99%

Radical mechanism of azo cleavage for monoazo reactive dyes, a QSPR study: the similarity between photoreduction on polyamide substrates and thermal reduction in aqueous dithionite solutions

Okada¹,

Hihara

Morita

2016

Coloration Technology

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“…[32][33][34][35][36][37] To our knowledge, there are only two reports 38,39 that involve ab initio studies on the mechanistic photochemistry of aromatic carbonyl compounds. We recently observed that several aromatic carbonyl compounds have a triple potential energy crossing point between the S 1 , T 1 , and T 2 states; this was reported in a short communication.…”

Section: Introductionmentioning

confidence: 99%

Photochemistry of Butyrophenone: Combined Complete-Active-Space Self-Consistent Field and Density Functional Theory Study of Norrish Type I and II Reactions

Fang

Phillips

2004

J. Phys. Chem. A

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The complete-active-space self-consistent field (CASSCF) and density functional theory (DFT) approaches have been used to study the mechanistic details of Norrish type I and II reactions of aromatic carbonyl compounds, with butyrophenone (PhCOCH 2 CH 2 CH 3 ) as a representative. A minimum energy crossing point was found to exist among three potential energy surfaces (S 1 , T 1 , and T 2 ), and the three-surface crossing allows the T 2 state to act as a relay that enables the intersystem crossing (ISC) from S 1 to T 1 to occur with a high efficiency for PhCOCH 2 CH 2 CH 3 . Once the molecule is in the T 1 state, the 1,5-H shift reaction is the predominant reaction pathway and yields a triplet 1,4-biradical of PhC(OH)CH 2 CH 2 CH 2 as an intermediate species. Since the formation of excited triplet products is energetically improbable, the subsequent decomposition, cyclicization, and disproportionation of the 1,4-biradical proceed after intersystem crossing from the triplet to singlet state. The singlet 1,4-biradical was found to have three isomers, which determine to a certain extent the branching ratios of the subsequent reactions. The study given here provides new insights into the S 1 relaxation dynamics of aromatic carbonyl compounds and their subsequent reaction mechanisms.

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“…The stereoselectivity of this reaction can be determined with the deuterium-labeled analog 31-d 2 : the exo 32x to endo 32n product ratio is 3 : 1. 63,64 Given the distinctly different natures of critical points along these surfaces, multiconfiguration wavefunctions with corrections for dynamic correlation is needed. Allred and Smith offered a third mechanism (Scheme 8.8).…”

Section: Deazetization Of 23-diazabicyclo[221]hept-2-ene 31mentioning

confidence: 99%

Organic Reaction Dynamics

Bachrach

2014

Computational Organic Chemistry

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In the previous chapters, we have focused our discussion of reaction mechanisms on the critical points along the reaction path. These critical points-local energy minima (reactants, intermediates, and products) and transition states (TSs)-were discussed in terms of their geometries and energies. We discussed the nature of the mechanism in terms of the topology of the potential energy surface (PES), the structure of the TSs, and the presence or absence of intermediates. We think of reactants progressing over TSs on to intermediates, perhaps through multiple intermediates and ending at products. This path is called the reaction coordinate and corresponds to the intrinsic reaction coordinate (IRC) or the minimum energy path (MEP) (see Section 1.6 for discussion on these two paths).This standard mechanistic analysis has a long successful history. Organic chemistry textbooks are filled with PESs and discussions of the implication of single-step versus multiple-step mechanisms, concerted TSs, and so on. 1,2 Transition state theory (TST) and Rice-Ramsperger-Kassel-Marcus (RRKM) theory provide tools for predicting rates based upon simple assumptions built upon the notion of reaction on the PES following the reaction coordinate. 3,4 An often-overlooked aspect of standard reaction mechanistic thought is that it really addresses only half of the picture. We talk about the positions of the atoms during the course of the reaction and the relative energies of points along the reaction path, but no mention is made of the time evolution of this process. In classical mechanics, description of a reactive system requires not just the particle positions but their momenta as well. The same is true for a quantum mechanical description, though one must keep in mind the limits imposed by the Heisenberg Uncertainty Principle. A complete description of a molecular reaction requires knowledge of both the position and the momentum of every atom for the entire time it takes for reactants to convert into products. This kind of description falls under the term molecular dynamics (MD).A few simple examples should suffice to demonstrate the critical role that MD plays in chemical reactions. Conservation of momentum must be enforced. Atoms and molecular fragments in motion must maintain their motion unless some barrier or force is applied to them. Consider the reaction of cis-2-butene with Computational Organic Chemistry, Second Edition. Steven M. Bachrach

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An MC-SCF/MP2 Study of the Photochemistry of 2,3-Diazabicyclo[2.2.1]hept-2-ene: Production and Fate of Diazenyl and Hydrazonyl Biradicals

Cited by 64 publications

References 52 publications

Radical mechanism of azo cleavage for monoazo reactive dyes, a QSPR study: the similarity between photoreduction on polyamide substrates and thermal reduction in aqueous dithionite solutions

Radical mechanism of azo cleavage for monoazo reactive dyes, a QSPR study: the similarity between photoreduction on polyamide substrates and thermal reduction in aqueous dithionite solutions

Photochemistry of Butyrophenone: Combined Complete-Active-Space Self-Consistent Field and Density Functional Theory Study of Norrish Type I and II Reactions

Organic Reaction Dynamics

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