scholarly journals Exploring Norrish type I and type II reactions: an ab initio mechanistic study highlighting singlet-state mediated chemistry

2019 ◽  
Vol 21 (26) ◽  
pp. 14418-14428 ◽  
Author(s):  
Barbara Marchetti ◽  
Tolga N. V. Karsili ◽  
Michael N. R. Ashfold
Keyword(s):  
Organic Chemistry ◽  
Ab Initio ◽  
Singlet State ◽  
Mechanistic Study ◽  
Type I ◽  
Type Ii ◽  
Biologically Relevant ◽  
Norrish Type

Norrish reactions are important photo-induced reactions in mainstream organic chemistry and are implicated in many industrially and biologically relevant processes and in the processing of carbonyl molecules in the atmosphere.

scholarly journals The Role of Norrish Type-I Chemistry in Photoactive Drugs: An ab initio Study of a Cyclopropenone-Enediyne Drug Precursor

2020 ◽  
Vol 8 ◽  
Author(s):  
Spencer J. Léger ◽  
Barbara Marchetti ◽  
Michael N. R. Ashfold ◽  
Tolga N. V. Karsili
Keyword(s):  
Ab Initio ◽  
Ground State ◽  
Singlet State ◽  
Substituent Effects ◽  
Type I ◽  
Bergman Cyclization ◽  
Ab Initio Study ◽  
Norrish Type ◽  
Subsequent Loss

We present a contemporary mechanistic description of the light-driven conversion of cyclopropenone containing enediyne (CPE) precusors to ring-opened species amenable to further Bergman cyclization and formation of stable biradical species that have been proposed for use in light-induced cancer treatment. The transformation is rationalized in terms of (purely singlet state) Norrish type-I chemistry, wherein photoinduced opening of one C–C bond in the cyclopropenone ring facilitates non-adiabatic coupling to high levels of the ground state, subsequent loss of CO and Bergman cyclization of the enediyne intermediate to the cytotoxic target biradical species. Limited investigations of substituent effects on the ensuing photochemistry serve to vindicate the experimental choices of Popik and coworkers (J. Org. Chem., 2005, 70, 1297–1305). Specifically, replacing the phenyl moiety in the chosen model CPE by a 1,4-benzoquinone unit leads to a stronger, red-shifted parent absorption, and increases the exoergicity of the parent → biradical conversion.

scholarly journals Competition Between Cyclization and Unusual Norrish Type I and Type II Nitro-Acyl Migration Pathways in the Photouncaging of 1-Acyl-7-nitroindoline Revealed by Computations

2020 ◽  
Author(s):  
Pierpaolo Morgante ◽  
Charitha Guruge ◽  
Yannick P. Ouedraogo ◽  
Nasri Nesnas ◽  
Roberto Peverati
Keyword(s):  
Density Functional ◽  
Acyl Migration ◽  
Density Functional Theory Calculations ◽  
Computational Procedure ◽  
Quantum Yields ◽  
Type I ◽  
Type Ii ◽  
Relative Quantum ◽  
Norrish Type ◽  
Migration Pathways

The 7-nitroindolinyl family of caging chromophores has received much attention in the past two decades. However, its uncaging mechanism is still not clearly understood. In this study, we performed state-of-the-art density functional theory calculations to unravel the photo-uncaging mechanism in its entirety, and we compared the probabilities of all plausible pathways. We found competition between a classical cyclization and acyl migration pathways, and here we explain the electronic and steric reasons behind such competition. The migration mechanism possesses the characteristics of a combined Norrish Type I and a 1,6-nitro-acyl variation of a Norrish Type II mechanism, which is reported here for the first time. We also introduced a computational procedure that allows the estimation of intersystem crossing rate constants useful to compare the relative quantum yield of substituted cages. This procedure may pave the way for improved cage designs that possess higher quantum yields and a more efficient agonist release.<br>

Photolysis of 4-Methyl 3-Hexanone and 2-Methoxy 3-Pentanone in Hydrocarbon Solution

1971 ◽  
Vol 49 (8) ◽  
pp. 1310-1314 ◽  
Author(s):  
L. P-Y. Lee ◽  
B. McAneney ◽  
J. E. Guillet
Keyword(s):  
Quantum Yield ◽  
Hydrogen Abstraction ◽  
Type I ◽  
Type Ii ◽  
Cage Effect ◽  
Predominant Type ◽  
Norrish Type ◽  
Hydrocarbon Solution ◽  
Membered Transition State ◽  
Made In

Studies of the photolysis of 4-methyl 3-hexanone and the iso-electronic 2-methoxy 3-pentanone have been made in hydrocarbon solution using light of wavelength 313 nm. The latter compound gives only Norrish type II products with a quantum yield of 0.19 ±.01. The former gives a predominance of type I products with a total quantum yield of 0.23 ±.01 and the quantum yield for type II is reduced to 0.10 ±.01. The predominant type I reaction appears to involve α-scission to give an ethyl and a 2-methyl butyryl radical, which suggests a "cage effect". It is suggested that the reason for the suppression of the type I reaction in 2-methoxy 3-pentanone is the greater ease of γ-hydrogen abstraction due to the presence of the oxygen atom in a six-membered transition state.

STRUCTURE AND MAGNETIC PROPERTIES IN RUTHENIUM-BASED FULL-HEUSLER ALLOYS: AB INITIO CALCULATIONS

2013 ◽  
Vol 27 (30) ◽  
pp. 1350219 ◽  
Author(s):  
S. BAHLOULI ◽  
Z. AARIZOU ◽  
M. ELCHIKH
Keyword(s):  
Magnetic Properties ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Nearest Neighbor ◽  
Heusler Alloys ◽  
Full Potential ◽  
Type I ◽  
Type Ii ◽  
Full Heusler ◽  
Full Heusler Alloys

In this paper, we present ab initio calculations within density functional theory (DFT) to investigate structure, electronic and magnetic properties of Ru 2 CrZ ( Z = Si , Ge and Sn ) full-Heusler alloys. We have used the developed full-potential linearized muffin tin orbitals (FP-LMTO) based on the local spin density approximation (LSDA) with the PLane Wave expansion (PLW). In particular, we found that these Ruthenium-based Heusler alloys have the antiferromagnetic (AFM) type II as ground state. Then, we studied and discussed the magnetic properties belonging to our different magnetic structures: AFM type II, AFM type I and ferromagnetic (FM) phase. We also found that Ru 2 CrSi and Ru 2 CrGe exhibit a semiconducting behavior whereas Ru 2 CrSn has a semimetallic-like behavior as it is experimentally found. We made an estimation of Néel temperatures (T N ) in the framework of the mean-field theory and used the energy differences approach to deduce the relevant short-range nearest-neighbor (J1) and next-nearest-neighbor (J2) interactions. The calculated T N are somewhat overestimated to the available experimental ones.

Photochemistry of macrocyclic ketones within zeolites: competition between norrish type I and type II reactivity

1991 ◽  
Vol 32 (52) ◽  
pp. 7675-7678 ◽  
Author(s):  
V. Ramamurthy ◽  
Xue-Gong Lei ◽  
Nicholas J. Turro ◽  
Thillairaj J. Lewis ◽  
John R. Scheffer
Keyword(s):  
Type I ◽  
Type Ii ◽  
Norrish Type

Modification of photochemical reactivity through the use of clathrates: the Norrish type I and type II reactions in Dianin's compound

1985 ◽  
Vol 63 (10) ◽  
pp. 2719-2725 ◽  
Author(s):  
P. C. Goswami ◽  
Paul de Mayo ◽  
N. Ramnath ◽  
G. Bernard ◽  
N. Omkaram ◽  
...  
Keyword(s):  
Inclusion Complexes ◽  
Hydrogen Abstraction ◽  
Photochemical Reactions ◽  
Type I ◽  
Type Ii ◽  
Guest Molecules ◽  
Photochemical Reactivity ◽  
Norrish Type ◽  
Restricted Environment ◽  
Dianin's Compound

Dianin's compound (4-p-hydroxyphenyl-2,2,4-trimethylchroman) serves as host in a series of well-defined clathrate inclusion complexes with eleven linear, as well as branched chain, phenyl alkyl ketone guest molecules, chosen for their ability to undergo the Norrish type I and type II photochemical reactions in solution. The photochemical reactivity of the guest ketones within the clathrate cavity was determined by irradiation of the inclusion complexes in the solid state. The results were compared to the photoreactivity of the ketones in polar as well as nonpolar liquid media. In general, the inclusion complex medium brings about an enhancement of type I over type II reactivity and causes an increase in type II fragmentation compared to type II cyclization. This change in reactivity is interpreted as resulting from the relatively restricted environment of the clathrate cavity coupled with the greater motion required for the type II process (γ-hydrogen abstraction) compared to the type I reaction (α-cleavage), as well as from the greater steric requirements for type II cyclization (cyclobutanol formation) as compared to type II cleavage (1,4-hydroxybiradical scission).

Sign in / Sign up

Export Citation Format

Share Document