scholarly journals A combined laser flash photolysis, density functional theory and atoms in molecules study of the photochemical hydrogen abstraction by pyrene-4,5-dione

2009 ◽  
Vol 201 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Nanci C. de Lucas ◽  
Mônica M. Elias ◽  
Caio L. Firme ◽  
Rodrigo J. Corrêa ◽  
Simon J. Garden ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Hydrogen Abstraction ◽  
Laser Flash ◽  
Atoms In Molecules ◽  
Functional Theory

Singlet Photoreactivity of 3-Methyl-2-phenyl-2H-azirine

2017 ◽  
Vol 70 (4) ◽  
pp. 413 ◽  
Author(s):  
Geethika K. Weragoda ◽  
Anushree Das ◽  
Sujan K. Sarkar ◽  
H. Dushanee M. Sriyarathne ◽  
Xiaoming Zhang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Density Functional Theory Calculations ◽  
Laser Flash ◽  
Functional Theory ◽  
Argon Matrices ◽  
Irradiation Wavelength

Irradiation of 3-methyl-2-phenyl-2H-azirine (1) at 254 nm in argon matrices results in ylide 6. Similarly, laser flash photolysis (λ = 266 nm) of azirine 1 in acetonitrile yields ylide 6, which has a transient absorption with λmax at ~340 nm and a lifetime of 14 μs. Density functional theory calculations were preformed to support the characterisation of ylide 6 in solution and argon matrices. Irradiation of azirine 1 above 300 nm has previously been reported (J. Org. Chem. 2014, 79, 653) to yield triplet vinylnitrene in solution and ketenimine in cryogenic argon matrices. Thus, the photochemistry of azirine 1 is dependent on the irradiation wavelength.

Formation and Direct Detection of Non-Conjugated Triplet 1,2-Biradical from β,γ-Vinylarylketone

2015 ◽  
Vol 68 (11) ◽  
pp. 1707 ◽  
Author(s):  
H. Dushanee M. Sriyarathne ◽  
Kosala R. S. Thenna-Hewa ◽  
Tianeka Scott ◽  
Anna D. Gudmundsdottir
Keyword(s):  
Rate Constant ◽  
Density Functional ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Direct Detection ◽  
Density Functional Theory Calculations ◽  
Laser Flash ◽  
Triplet Excited State ◽  
Functional Theory

Laser flash photolysis of 2-methyl-1-phenylbut-3-en-1-one (1) conducted at irradiation wavelengths of 266 and 308 nm results in the formation of triplet 1,2-biradical 2 that has λmax at 370 and 480 nm. Biradical 2 is formed with a rate constant of 1.1 × 107 s–1 and decays with a rate constant of 2.3 × 105 s–1. Isoprene-quenching studies support the notion that biradical 2 is formed by energy transfer from the triplet-excited state of the ketone chromophore of 1. Density functional theory calculations were used to verify the characterization of triplet biradical 2 and validate the mechanism for its formation. Thus, it has been demonstrated that intramolecular sensitization of simple alkenes can be used to form triplet 1,2-biradicals with the two radical centres localized on the adjacent carbon atoms.

scholarly journals Towards a density functional theory of molecular fragments. What is the shape of atoms in molecules?

2020 ◽  
Vol 44 (170) ◽  
pp. 269-279
Author(s):  
Victor H. Chávez ◽  
Adam Wasserman
Keyword(s):  
Density Functional Theory ◽  
Schrödinger Equation ◽  
Schrodinger Equation ◽  
Density Functional ◽  
Computational Cost ◽  
Atoms In Molecules ◽  
Electronic Density ◽  
Functional Theory ◽  
New Methods ◽  
The Cost

In some sense, quantum mechanics solves all the problems in chemistry: The only thing one has to do is solve the Schrödinger equation for the molecules of interest. Unfortunately, the computational cost of solving this equation grows exponentially with the number of electrons and for more than ~100 electrons, it is impossible to solve it with chemical accuracy (~ 2 kcal/mol). The Kohn-Sham (KS) equations of density functional theory (DFT) allow us to reformulate the Schrödinger equation using the electronic probability density as the central variable without having to calculate the Schrödinger wave functions. The cost of solving the Kohn-Sham equations grows only as N3, where N is the number of electrons, which has led to the immense popularity of DFT in chemistry. Despite this popularity, even the most sophisticated approximations in KS-DFT result in errors that limit the use of methods based exclusively on the electronic density. By using fragment densities (as opposed to total densities) as the main variables, we discuss here how new methods can be developed that scale linearly with N while providing an appealing answer to the subtitle of the article: What is the shape of atoms in molecules?

Density Functional Theory and Quantum Theory of Atoms in Molecules Analysis: Influence of Intramolecular Interactions on Pirouetting Movement in Tetraalkylsuccinamide[2]rotaxanes

2017 ◽  
Vol 17 (11) ◽  
pp. 5845-5857 ◽  
Author(s):  
Marcos A. P. Martins ◽  
Leticia V. Rodrigues ◽  
Alexandre R. Meyer ◽  
Clarissa P. Frizzo ◽  
Manfredo Hörner ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Quantum Theory ◽  
Density Functional ◽  
Intramolecular Interactions ◽  
Atoms In Molecules ◽  
Functional Theory
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