Photoenols, formed through photoinduced intramolecular H atom abstraction in o-alkyl-substituted arylketones, typically have limited utility as reactive intermediates owing to fast reversion the starting material. Herein, we introduced an azido group on o-alkyl substituent render photoreaction irreversible. Irradiation of 2-azidomethylbenzophenone (1) methanol yielded 2-(hydroxy(phenyl)methyl)benzonitrile (2). Laser flash photolysis 1 revealed formation biradical 3Br1 followed by intersystem...

Laser flash photolysis (LFP, Nd:YAG laser, 35 ps, 266 nm, 10 mJ or KrF excimer ns, 249 50 mJ) of 2-fluoro, 4-fluoro, 3,5-difluoro, 2,6-difluoro, and 2,3,4,5,6-pentafluorophenyl azides produces the corresponding singlet nitrenes. The nitrenes were detected by transient absorption spectroscopy, their spectra are characterized sharp bands with maxima in range 300-365 nm. kinetics decay analyzed as a function temperature to yield observed rate constants, k(OBS). constant inert solvents is sum...

When exposed to UV light, single crystals of the vinyl azides 3-azido-1-phenylpropenone (1a), 3-azido-1-(4-methoxyphenyl)propenone (1b), and 3-azido-1-(4-chlorophenyl)propenone (1c) exhibit dramatic mechanical effects by cracking or bending with release N2. Mechanistic studies using laser flash photolysis, supported quantum calculations, show that each degrades through a vinylnitrene intermediate. However, despite having very similar crystal packing motifs, three compounds distinct...

The Norrish/Yang type II photochemistry of ten even-numbered cyclic diketones ranging in ring size from 10-membered to 26-membered has been studied the crystalline state as well solution. In solid state, undergo stereoselective cyclobutanol formation which cis or trans fusion stereochemistry photoproducts is governed by conformation diketone present crystal determined X-ray crystallography. reactive γ-hydrogen atoms are identified and distance angular parameters associated with their...

Photolysis of beta-azido propiophenone derivatives, 1, with built-in sensitizer units, leads to selective formation triplet alkyl nitrenes 2 that were detected directly laser flash photolysis (lambdamax = 325 nm, tau 27 ms) and ESR spectroscopy (|D/hc| 1.64 cm-1, |E/hc| 0.004 cm-1). Nitrenes further characterized argon matrix isolation, isotope labeling, molecular modeling. The are persistent intermediates do not abstract H-atoms from the solvent but decay by dimerizing another nitrene form...

Photolysis of gamma-azidobutyrophenone derivatives yields 1,4 ketyl biradicals via intramolecular H-atom abstraction. The expel a nitrogen molecule to form 1,5 iminyl biradicals, which decay by ring closure new carbon-nitrogen bond. were characterized with transient spectroscopy. In argon/nitrogen-saturated solutions, the have lambda(max) approximately 300 nm and tau = 15 micros. DFT-TD calculations used support proposed mechanism for formation radicals.

The photoreactivity of (3-methyl-2H-azirin-2-yl)-phenylmethanone, 1, is wavelength-dependent (Singh et al. J. Am. Chem. Soc. 1972, 94, 1199-1206). Irradiation at short wavelengths yields 2P, whereas longer produce 3P. Laser flash photolysis 1 in acetonitrile using a 355 nm laser forms its triplet ketone (T(1K), broad absorption with λ(max) ~ 390-410 nm, τ 90 ns), which cleaves and vinylnitrene 3 (broad 380-400 = 2 μs). Calculations (B3LYP/6-31+G(d)) reveal that T(1K) located 67 kcal/mol...

Photolysis of 1 in argon-saturated acetonitrile yields 2, whereas oxygen-saturated small amounts benzoic acid and benzamide are formed addition to 2. Similarly, photolysis 2 results a trace amount 3, the major product is formation benzamide. Laser flash an absorption due triplet vinylnitrene 4 (broad with λ(max) at 360 nm, τ = 1.8 μs, acetonitrile) that rate constant 1.2 × 10(7) s(-1) decays 5.6 10(5) s(-1). likewise but also ylide 5 (λ(max) 440 13 μs). The for forming 1.6 In acetonitrile,...

The photolysis of 2-azido-1,4-naphthoquinone (1) in argon matrices at 8 K results the corresponding triplet vinylnitrene 32, which was detected directly by IR spectroscopy. Vinylnitrene 32 is stable but forms 2-cyanoindane-1,3-dione (3) upon further irradiation. Similarly, irradiation azide 1 2-methyltetrahydrofuran (MTHF) 5 resulted ESR spectrum up to least 100 K. zero-field splitting parameters for nitrene D/hc = 0.7292 cm–1 and E/hc 0.0048 cm–1, verify that it has significant...

Photolysis of 3-azido-1-indenone (1) with a light-emitting diode (LED, λ = 405 nm) or mercury arc lamp (Pyrex) resulted in the formation heterodimer 3 excellent yield, through dimerization triplet vinylnitrene 32. At ambient temperature, 32 (λmax at 340 and 480 was detected directly laser flash photolysis vinyl azide 1. The intermediate also characterized IR ESR spectroscopy cryogenic matrices. spectrum yielded zero-field splitting parameter |D/hc| 0.460 cm-1 |E/hc| 0.015 cm-1, which reveals...

Laser flash photolysis (LFP) (XeCl, 308 nm, 17 ns) of phenyldiazomethane and pentafluorophenyldiazomethane releases phenylcarbene (PC) pentafluorophenylcarbene (PFPC), respectively. In acetonitrile solvent the carbenes react rapidly to form nitrile ylides which have convenient absorption maxima for optical detection (λmax = 350 nm). Phenylcarbene each with an absolute rate constant 2.4 × 106 M-1 s-1 in CF2ClCFCl2 (Freon-113) at ambient temperature. The lifetimes spin-equilibrated PC PFPC are...

We report the first detection of triplet alkyl nitrenes in fluid solution by laser flash photolysis alpha-azido acetophenone derivatives, 1. Alphazides 1 contain an intramolecular sensitizer, which ensures formation nitrene bypassing singlet intermediate. At room temperature, azides cleave to form benzoyl and methyl azide radicals competition with energy transfer nitrene. The major photoproduct 3 arises from interception radicals. intermediates are also trapped molecular oxygen yield...

Molecular modeling demonstrates that the first excited state of triplet ketone (T1K) in azide 1b has a (pi,pi*) configuration with an energy is 66 kcal/mol above its ground and second (T2K) 10 higher (n,pi*) configuration. In comparison, T1K T2K 1a are almost degenerate at 74 77 configuration, respectively. Laser flash photolysis (308 nm) methanol yields transient absorption (lambdamax=450 due to formation T1K, which decays rate 2.1 x 105 s-1 form alkylnitrene 2b (lambdamax=320 nm). The...

Photolysis of 3-methyl-2-phenyl-2H-azirine (1a) in argon-saturated acetonitrile does not yield any new products, whereas photolysis oxygen-saturated yields benzaldehyde (2) by interception vinylnitrene 5 with oxygen. Similarly, 1a the presence bromoform allows trapping 5, leading to formation 1-bromo-1-phenylpropan-2-one (4). Laser flash (λ = 308 nm) results a transient absorption λmax at ∼440 nm due triplet 5. Likewise, irradiation cryogenic argon matrixes through Pyrex filter ketene imine...

3-p-Tolyl-3-trifluoromethyldiazirine was studied by laser flash photolysis (LFP) to obtain the absolute kinetics of p-tolyl(trifluoromethyl)carbene 1. The rate constants for reactions 1 with pyridine, ketones and quenchers biological interest were obtained. implications data photoaffinity labeling experiments are discussed.

We have designed molecules which release alcohols upon exposure to UV light independent of the reaction media, making it possible liberate in a controlled manner applications. Photolysis 2-(2-isopropylbenzoyl)benzoate ester derivatives 4 various solvents and thin films results liberation alcohol moiety from ester. The mechanism for has been elucidated by time-resolved laser flash photolysis. Upon irradiation triplet excited state ketone, is formed, its lifetime can be estimated between 0.08...

[reaction: see text] Photolysis of 3 in argon-saturated 2-propanol led to formation 5 via intermolecular H-atom abstraction followed by lactonization. Irradiation 4 gave compounds 6 and 7 that also come from abstraction. In contrast, photolysis an oxygen-saturated solution yields products 8, 9, 10, which were all formed intramolecular trapping the corresponding biradical with oxygen. Laser flash methanol showed 3BR (lambda(max) 330 nm, tau = 50 ns) as main photoreactivity 3. Biradical...

Solid-state photolysis of 1a,b yields selectively cis-3a,b. X-ray analysis reveals the molecules adopt an extended structure and as such crystal packing arrangement consists planar, pi-stacked molecules. The shortest intermolecular distance between adjacent N-atoms is approximately 3.76 A would lead to formation trans-3a,b, whereas cis-3a,b formed by dimerization that are 3.9 apart. We propose molecular orbital alignment nitrenes controls solid-state reactivity.

Abstract The enthalpies for H‐atom abstraction reactions by triplet imidogen as well ethyl, alkoxycarbonyl, acyl, phenyl, and vinyl nitrenes were calculated using density functional theory calculations. These calculations show that are only feasible imidogen, acyl in solution. charges on the N‐atoms ( Q NPA ) nitrene correlate with magnitude of transition state barrier from methanol a model reactant. Electron‐withdrawing substituents these make them less stable but do not affect...

Photolysis of vinylazide 1, which has a built-in acetophenone triplet sensitizer, in argon-saturated toluene results azirine 2, whereas irradiation oxygen-saturated yields cyanide derivatives 3 and 4. Laser flash photolysis azide 1 acetonitrile shows formation vinylnitrene 1c, λmax at ∼300 nm lifetime ∼1 ms. Vinylnitrene 1c is formed with rate constant 4.25 × 10(5) s(-1) from 1,2-biradical 1b. 1c-O (λmax = 430 nm, τ ≈ 420 μs acetonitrile). Density functional theory (DFT) calculations were...

Well-defined dinuclear silver(I) complexes have been targeted for applications in catalysis and materials chemistry, the effect of close silver–silver interactions on electronic structure remains an area active inquiry. In this study, we describe synthesis, structure, photophysical properties dimeric silver featuring a redox-active naphthyridine diimine ligand. Unusually silver(I), these display absorption features visible region due to metal–metal ligand charge transfer (MMLCT) transitions,...

Several bromophenyl alkyl ketones undergo photoinduced radical cleavage of bromine atoms; the resulting acylphenyl radicals are trapped as dehalogenated either by alkane solvents or added thiols. Quantum yields for this process decrease with increasing solvent viscosity; behavior indicates that recoupling phenyl/bromine pairs competes their diffusion apart. In some cases Norrish type II elimination reaction. Steady state studies indicate room temperature rate constants triplet C−Br 2 and 1 ×...