Search results for "Light induced"

Light-Induced Alkylation of (Hetero)aromatic Nitriles in a Transition-Metal-Free C–C-Bond Metathesis

2017

A light-induced C–C-σ-bond metathesis was achieved through transition-metal-free activation of an unstrained C(sp3)–C(sp3)-σ-bond in 1-benzyl-1,2,3,4-tetrahydroisoquinolines. A photoredox-mediated single-electron oxidation of these precursor amines yield radical cations which undergo a homolytic cleavage of a C(sp3)–C(sp3)-σ-bond rather than the well-known α-C–H-scission. The resulting carbon-centered radicals are used in the ipso-substitution of (hetero)aromatic nitriles proceeding through another single-electron transfer-mediated C–C-bond cleavage and formation.

Light Induced C-C Coupling of 2-Chlorobenzazoles with Carbamates, Alcohols, and Ethers.

2016

A light induced, transition-metal-free C-C coupling reaction of 2-chlorobenzazoles with aliphatic carbamates, alcohols, and ethers is presented. Inexpensive reagents, namely sodium acetate, benzophenone, water, and acetonitrile, are employed in a simple reaction protocol using a cheap and widely available 25 W energy saving UV-A lamp at ambient temperature.

Light-induced opening and closing of the intramolecular hydrogen bond in glyoxylic acid.

2013

The isomerization process of glyoxylic acid (GA) conformers and their complexes with a water molecule were studied in a low temperature argon matrix. The research target was to understand how starting conformation and complexation affects the near-IR (NIR) induced conformer interconversion. The most stable GA conformer (Tc) is characterized by an intramolecular hydrogen bond, and it is found to undergo light-induced conformer interconversion slower than the open (Tt) conformer. Upon complexation with water, the isomerization processes slow down in the case of the Tc conformer, whereas for the Tt-based complex the influence of water is negligible on the isomerization process.

A Light-Induced Vinylogous Nazarov-Type Cyclization

2016

The first examples of a photochemically induced vinylogous Nazarov-type cyclization forming a cycloheptadienone core are described. The reaction can be included in a three-step cascade consisting of a photochemical isoxazole-azirine ring contraction, cobalt(II)-catalyzed ring expansion, and the photochemical cyclization. Furthermore, the first representative of the hitherto unknown 1-azatricyclo[2.2.0.0(2,6)]hexanes has been identified as a side product of the azirine formation.

ChemInform Abstract: A Light-Induced Vinylogous Nazarov-Type Cyclization.

2016

The title reaction is incorporated in a three-step cascade transformation providing novel tetracyclic ring structures containing a seven-membered ring.

Light Induced Excited Pair Spin State in an Iron(II) Binuclear Spin-Crossover Compound

1999

Simulating Terahertz Field-Induced Ferroelectricity in Quantum Paraelectric SrTiO3

2021

Recent experiments have demonstrated that light can induce a transition from the quantum paraelectric to the ferroelectric phase of SrTiO3. Here, we investigate this terahertz field-induced ferroelectric phase transition by solving the time-dependent lattice Schrödinger equation based on first-principles calculations. We find that ferroelectricity originates from a light-induced mixing between ground and first excited lattice states in the quantum paraelectric phase. In agreement with the experimental findings, our study shows that the nonoscillatory second harmonic generation signal can be evidence of ferroelectricity in SrTiO3. We reveal the microscopic details of this exotic phase transi…

Light-induced excited spin-state trapping of the Fe(ppi)2(NCS)2 complex

1996

Intersystem Crossing and Light-Induced Bistability in Iron(?) Spin-Crossover Compounds

1996

Abstract The dynamics of the high-spin→low-spin intersystem crossing process in iron(?) spin-crossover compounds are strongly influenced by cooperative effects of elastic origin which are due to the large difference in volume between high-spin and low-spin complexes. The deviation from first order kinetics is attributed to a build-up of an internal pressure as the relaxation proceeds, leading to a characteristic self-acceleration. The elastic interactions may lead to a light-induced bistability for systems which otherwise remain in the high-spin state down to cryogenic temperatures.

Light-Induced Formation of Pb3+Paramagnetic Species in Lead Halide Perovskites

2018

Hybrid halide perovskites are soft materials processed at room temperature, revolutionary players in the photovoltaic field. Nowadays, investigation of the nature and role of defects is seen as one of the key challenges toward full comprehension of their behavior and achievement of high device stability under working conditions. We reveal the reversible generation, under illumination, of paramagnetic Pb3+ defects in CH3NH3PbI3, synthesized in ambient conditions, induced by the presence of Pb-O defects in the perovskite structure that may trap photogenerated holes, possibly mediated by the concomitant oxidation and migration of ions. According to the mechanism that we hypothesize, one charge…