DFT, spectroscopic, and photoproduct study of 2-aminoethyldiphenylborinate and tetraphenyldiboroxane

Santos, Willy G.; Cardoso, Daniel; Arrivetti, Leandro de Oliveira Rodrigues; Cavalheiro, Carla Cristina Schmitt; Neumann, Miguel G.

doi:10.1016/j.jorganchem.2014.01.010

Cited by 2 publications

(3 citation statements)

References 23 publications

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“…S2, ESI †). [71][72][73] The values of the phosphorescence quantum yields at 77 K are shown in Table 2. For tetraarylborate, the phosphorescence yield is lower than that observed for B(Ph) 3 .…”

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New insight into the photophysics and reactivity of trigonal and tetrahedral arylboron compounds

Santos

Pina

Burrows

et al. 2016

Photochem Photobiol Sci

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The photophysics and reactivity of two tetraphenylborate salts and triphenylborane have been studied using ultrafast transient absorption, steady-state fluorescence, electron paramagnetic resonance with spin trapping, and DFT calculations. The singlet excited state of tetraarylborates exhibit extended π-orbital coupling between two adjacent aryl groups. The maximum fluorescence band, as well as the transient absorption bands centered at 560 nm (τ = 1.05 ns) and 680 nm (τ = 4.35 ns) are influenced by solvent viscosity and polarity, indicative of a twisted intramolecular charge transfer (TICT) state. Orbital contour plots of the HOMO and LUMO orbitals of the tetraarylboron compounds support the existence of electron delocalization between two aryl groups in the LUMO. This TICT-state and aryl-aryl electron extension is not observed for the trigonal arylboron compound, in which excited π-orbital coupling only occurs between the boron atom and one aryl group, which restricts the twist motion of the aryl-boron bond. The excited triplet state is deactivated primarily through aryl-boron bond cleavage, yielding aryl and diphenylboryl radicals. In the presence of oxygen, this photochemistry results in phenoxyl and diphenylboroxyl radicals, as confirmed by EPR spectroscopy of spin trapped radical adducts. The TICT transition and radical generation is not expected for BoDIPY molecules where the rotational vibration of the B-aryl bond is rigid, restricting changes in the geometric structure. In this sense, this work contributes to the development of new BoDIPY derivatives where the TICT transition may be observed for aryl ligands with free rotational vibrations in the BoDIPY structure.

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confidence: 99%

New insight into the photophysics and reactivity of trigonal and tetrahedral arylboron compounds

Santos

Pina

Burrows

et al. 2016

Photochem Photobiol Sci

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“…Other conventional photoinitiation systems such as riboflavin/amine ,, or safranine/borinate ,− have been observed with low values of activation energy ( E a < 10 kJ mol –1 ). In this sense, the activation energy found for the tetraarylborate systems reveals a moderate stability against thermal process, also indicating that the use of the tetraarylborate as initiator or co-initiator systems may be useful in polymerization studies where the major polymerization pathway is the photochemical process.…”

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“…Electron transfer reactions from the photoinduced excited state of riboflavin represent an important route of free radical formation that in the presence of an electron donor or co-initiator (i.e., amine) may initiate vinyl monomer polymerization. − , Alkylboron derivatives have been used as co-initiators of photopolymerization reactions − as well. The irradiation of the two-component system made by a dye and an alkylboron compound release a free and reactive alkyl radical with subsequent reaction with monomer units, initiating the polymerization process. ,,− …”

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Polymerization Rate Modulated by Tetraarylborate Anion Structure: Direct Correlation of Hammett Substituent Constant with Polymerization Kinetics of 2-Hydroxyethyl Methacrylate

2018

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A series of para-substituted tetraarylborates were investigated as aryl radical generator for photopolymerization reactions, using 2-hydroxyethyl methacrylate as monomer. The first steps of the photopolymerization process involve the use of tetraarylborate as monocomponent photoinitiator or combination of two-component systems (riboflavin and tetraarylborate anion) to generate the aryl radical species, which is used to initiate the radicalar polymerization of vinyl monomers. Both photoinitiator systems herein investigated are very attractive for vinyl polymerization upon light irradiation. The polymerization and photochemical results indicate that the changes on the para-substituted ligand may be used to improve the formation of aryl radical species and the rate constant of electron transfer into two-component systems. In consequence of this reaction, the kinetics of radical polymerization is also modulated by electron donor/acceptor features of para-substituent ligands.

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DFT, spectroscopic, and photoproduct study of 2-aminoethyldiphenylborinate and tetraphenyldiboroxane

Cited by 2 publications

References 23 publications

New insight into the photophysics and reactivity of trigonal and tetrahedral arylboron compounds

New insight into the photophysics and reactivity of trigonal and tetrahedral arylboron compounds

Polymerization Rate Modulated by Tetraarylborate Anion Structure: Direct Correlation of Hammett Substituent Constant with Polymerization Kinetics of 2-Hydroxyethyl Methacrylate

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