The photocycloaddition of dibenzoylmethanatoboron difluoride (DBMBF2) with conjugated enones and en-esters

1993 ◽  
Vol 71 (6) ◽  
pp. 846-854 ◽  
Author(s):  
Yuan L. Chow ◽  
Shi-Sen Wang ◽  
Xian-En Cheng
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Ring Opening ◽  
Electron Donors ◽  
Head Orientation ◽  
Singlet Excited State ◽  
Methyl Substitution ◽  
Unsaturated Ketones ◽  
Dibenzoylmethanatoboron Difluoride

Dibenzoylmethanatoboron difluoride (DBMBF2), the BF2 complex of dibenzoylmethane, reacted from its singlet excited state with α,β-unsaturated ketones and esters to give 1,5-diketones by a [2+2] cycloaddition and ring-opening sequence in an analogous pathway to that observed in the photocycloaddition to olefins and dienes. The present photoreaction is unexpected since conjugated enones and en-esters are poor electron donors to comply with the previously proposed charge transfer requirement in DBMBF2 photoreactions. The photocycloaddition to these substrates was highly regioselective and stereoselective, giving the head-to-head orientation, which could be enhanced by α-methyl substitution; β-methyl substitution increased the alternate head-to-tail orientation. The photolysis of a mixture of DBMBF2 and a cyclic enone also caused the latter to dimerize to give head-to-head and head-to-tail dimers in significant yields. These photodimerizations were apparently caused by DBMBF2 sensitization. The mechanism of the sensitization is discussed.

The dual pathway in photocycloaddition of 1,3-diketonatoboron difluorides: excimer reactions

1991 ◽  
Vol 69 (10) ◽  
pp. 1575-1583 ◽  
Author(s):  
Yuan L. Chow ◽  
Xianen Cheng
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Model Compound ◽  
Singlet State ◽  
Quantum Yields ◽  
Singlet Excited State ◽  
Dibenzoylmethanatoboron Difluoride ◽  
Dual Pathway ◽  
Excimer Formation ◽  
Simple Olefin

The lowest singlet excited state of dibenzoylmethanatoboron difluoride DBMBF2, a model compound of the BF2 complexes of 1,3-diketones, reacted with various simple olefins to give regiospecific and stereospecific photocycloadducts of 1,5-diketones similar to those from the de Mayo type reaction. DBMBF2 in acetonitrile exhibited two discrete fluorescences at 398 and 416 nm for the monomer and at 522 nm for the excimer; they were both quenched, but in different proportions, by a simple olefin. An "oxygen test" showed that the excimer of DBMBF2 is formed irreversibly in acetonitrile. The quantum yields of the photocycloaddition were shown to be proportional not only to olefin concentrations but also to DBMBF2 concentrations. Kinetic analysis has established that the total quantum yield is the sum of those arising from the interactions of the singlet excited DBMBF2 and its excimer, respectively, with an olefin, i.e., the sum of the quantum yields of exciplex and triplex pathways. The contributions from the two pathways are determined by the type of olefins and the range of DBMBF2 concentrations. For endocyclic olefins, the triplex pathway is more important and the corresponding photocycloaddition becomes very efficient as soon as the excimer starts to form in [DBMBF2] > 0.001 M. For the monosubstituted olefins, on the contrary, the exciplex pathway is always more important than the triplex pathway; they react primarily from the singlet excited state of DBMBF2. Key words: singlet state photocycloaddition, irreversible excimer formation, excimer cycloaddition, triplex and exciplex reactions.

Ground state and excited state charge transfer complexes between electron donors and pyrylium salts

1984 ◽  
Vol 26 (2-3) ◽  
pp. 131-140 ◽  
Author(s):  
V. Wintgens ◽  
J. Pouliquen ◽  
M. Simalty ◽  
J. Kossanyi ◽  
F.K. Justesen ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Ground State ◽  
Electron Donors ◽  
Charge Transfer Complexes ◽  
Pyrylium Salts ◽  
State Charge

Picosecond Infrared Spectra of Isotope-Substituted 4-(Dimethylamino)benzonitriles and Molecular Structure of the Charge-Transfer Singlet Excited State

2001 ◽  
Vol 105 (17) ◽  
pp. 4182-4188 ◽  
Author(s):  
Hiromi Okamoto ◽  
Hironori Inishi ◽  
Yuko Nakamura ◽  
Shigeru Kohtani ◽  
Ryoichi Nakagaki
Keyword(s):  
Molecular Structure ◽  
Excited State ◽  
Charge Transfer ◽  
Infrared Spectra ◽  
Singlet Excited State

Spektroskopische Untersuchung von Hetero-Excimeren mit heterozyklischen aromatischen Kohlenwasserstoffen als Elektronakzeptoren

1970 ◽  
Vol 25 (10) ◽  
pp. 1442-1447 ◽  
Author(s):  
Dieter Rehm
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Aromatic Hydrocarbons ◽  
Dipole Moments ◽  
Electron Donors ◽  
Emission Maximum ◽  
Charge Transfer Interaction

Abstract Heterocyclic aromatic hydrocarbons form hetero-excimers with electron donors. The correlation which exists between the energy corresponding to the complex emission maximum and the redoxpotentials of acceptors and donors shows that charge-transfer interaction is predominant in these hetero-excimers.For some complexes the thermodynamic parameters of complex formation as well as the dipole moments in the excited state are reported.

1,3-Diketonatoboron difluoride sensitized cation radical reactions

1991 ◽  
Vol 69 (8) ◽  
pp. 1331-1336 ◽  
Author(s):  
Y. L. Chow ◽  
Xianen Cheng
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Ground State ◽  
Cation Radical ◽  
Radical Reactions ◽  
Singlet Excited State ◽  
Anti Isomer ◽  
Cation Radicals ◽  
Dibenzoylmethanatoboron Difluoride ◽  
Boron Complexes

Dibenzoylmethanatoboron difluoride (DBMBF2) and allied BF2 complexes interact from their singlet excited state with trans-anethole (t-A), quadricyclene (QC), and norbornadiene (NBD) by electron transfer to generate the corresponding cation radicals, which undergo the reported reactions. By sensitization, t-A undergoes dimerization to form the anti head-to-head and syn head-to-head dimers with retention of stereochemistry. The formation is reversible under sensitization conditions, leading to accumulation of the more stable anti isomer. However, irradiation of the absorption band of the DBMBF2 – t-A ground state complex did not lead to dimerization of t-A. By DBMBF2 sensitization, QC is cleanly converted to NBD while NBD is not affected. The calculation shows QC+• possesses higher energy than NBD+• by 7.5 kcal/mol, hence an irreversible rearrangement. Other sensitizers (e.g., cyanoaromatics and tetrachlorobenzoquinone) also promote these cation radical reactions but not as cleanly as DBMBF2. Key words: photosensitization by boron complexes, cation radical rearrangement, cation radical cycloaddition, electron transfer sensitization, photoreaction of ground state complexes.

Dynamic adjustment of emission from both singlets and triplets: the role of excited state conformation relaxation and charge transfer in phenothiazine derivates

2021 ◽  
Author(s):  
Weidong Qiu ◽  
Xinyi Cai ◽  
Mengke Li ◽  
Liangying Wang ◽  
Yanmei He ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Intramolecular Charge Transfer ◽  
Dynamic Adjustment ◽  
Twisted Intramolecular Charge Transfer

Dynamic adjustment of emission behaviours by controlling the extent of twisted intramolecular charge transfer character in excited state.

Novel Carbazole-based Multifunctional Materials with Hybridized Local and Charge-Transfer Excited State Acting as Deep Blue Emitters and Phosphorescent Hosts for Highly Efficient Organic Light-Emitting Diodes

2021 ◽  
Author(s):  
Haitao Zhou ◽  
Mengna Yin ◽  
Zhenhong Zhao ◽  
Yanqin Miao ◽  
Xin Jin ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
Multifunctional Materials ◽  
Light Emitting ◽  
Highly Efficient ◽  
Deep Blue ◽  
Organic Light ◽  
Blue Emitters

In this work, two carbazole- and benzo[d]oxazole-based novel multifunctional materials with hybridized local and charge-transfer (HLCT) characteristic, namely OCI and OCT, which could act as deep-blue fluorophors and phosphorescent hosts,...

scholarly journals Anion-enhanced excited state charge separation in a spiro-locked N-heterocycle-fused push-pull zinc porphyrin

2021 ◽  
Author(s):  
Mandeep K. Chahal ◽  
Anuradha Liyanage ◽  
Ajyal Z. Alsaleh ◽  
Paul A. Karr ◽  
Jonathan P. Hill ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Charge Separation ◽  
Charge Transfer Complex ◽  
Zinc Porphyrin ◽  
New Type ◽  
State Charge

A new type of push–pull charge transfer complex, viz., a spiro-locked N-heterocycle-fused zinc porphyrin, ZnP-SQ, is shown to undergo excited state charge separation, which is enhanced by axial F− binding to the Zn center.

Charge Transfer States and Carrier Generation in 1D Organolead Iodide Semiconductors

2021 ◽  
Author(s):  
Eric Amerling ◽  
Yaxin Zhai ◽  
Bryon W. Larson ◽  
Yi Yao ◽  
Brian Fluegel ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Energy Harvesting ◽  
Metal Halide ◽  
Triplet Energy ◽  
Carrier Generation ◽  
Inorganic Components

Excited-state interactions between organic and inorganic components in hybrid metal halide semiconductors open up the possibility of moving charge and energy in deliberate ways, including energy funneling, triplet energy harvesting,...

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