Highly photostable luminescent open-shell (3,5-dihalo-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radicals: significant effects of halogen atoms on their photophysical and photochemical properties

Abstract

Novel luminescent radicals, Br 2 PyBTM and F 2 PyBTM were synthesized and their structures, spectroscopic properties, photostability, and electronic structures were compared with those of Cl 2 PyBTM. Br 2 -PyBTM showed the highest photostability and F 2 PyBTM displayed the highest photoluminescence quantum yield of the three radicals.

Modulated Luminescence of a Stable Open‐Shell Triarylmethyl Radical: Effects of Chemical Modification on Its Electronic Structure and Physical Properties

“…D 0 electronic excitation. [17] Conclusion This study represents the first example of the reversible control of an emission colour of aluminescent radical by external stimuli. D 0 transition energies calculated by TDDFT (E calc ;T able1).…”

“…The spectral change wass imilar to that seen upon addition of H + to PyBTM in CH 2 Cl 2 , [14] and the final spectrum( blue in Figure4a) was also similar to that of [MeN-PyBTM](BF 4 )( Figure 5). The lowest-energy absorption band (l LE )a t 575 nm was attributedt ot he transition from the doublet ground state (D 0 )t ot he lowest-energy doublete xcited state (D 1 ), [14,17] which was red-shifted compared with that of PyBTM. The lowest-energy absorption band (l LE )a t 575 nm was attributedt ot he transition from the doublet ground state (D 0 )t ot he lowest-energy doublete xcited state (D 1 ), [14,17] which was red-shifted compared with that of PyBTM.…”

“…[8,9] In general,c hemicallyu nstable radicalsa re employed in examiningt he relevante mission properties, and such speciesa re transiently generated in situ by laser photolysis or pyrolysis in ar igid matrix. [15][16][17] PyBTMi sp ersistent under ambient conditions and upon UV irradiation.I ts excellentp hotostability is up to 115t imes higher than that of the tris(2,4,6-trichlorophenyl)methyl radical, and is distinct from those of other previously reported radicals. [11][12][13] We prepared the luminescent (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM;F igure 1), [14] and investigated its properties and photostability upon coordinationt oA u I or Cu II or substitution with halogen atoms.…”

An Enantiopure Propeller‐Like Trityl‐Brominated Radical: Bringing Together a High Racemization Barrier and an Efficient Circularly Polarized Luminescent Magnetic Emitter

“…Moreover, the less electron‐withdrawing effect of the Br atoms might be behind such a lower yield in comparison with the TTM one. In fact, similar LQY were observed by Hattori et al . when performing a partial substitution of the ortho ‐positions in one ring of the TTM radical with bromine atoms, underlining the importance of the halogens in determining the optical properties.…”

Design of Perchlorotriphenylmethyl (PTM) Radical‐Based Compounds for Optoelectronic Applications: The Role of Orbital Delocalization

“…Moreover, Möller‐Plesset perturbation approaches were also discarded due to problems linked to spin contamination for open‐shell systems such as the PTM radical, which are found to be significantly reduced in the case of Unrestricted DFT approaches. At the DFT level of theory, standard hybrid functionals such as (U)B3LYP have been used to successfully describe the energy levels in PTM radical‐based compounds,, or to calculate Raman spectra ,. However, their use in the description of excited states has been limited,, due to the inherent problems of this functional to deal with the charge‐transfer (CT) character of excited states,, leading to a typical overestimation of their transition energies.…”