Organic Free Radicals as Circularly Polarized Luminescence Emitters

Burrezo, Paula Mayorga; Jiménez, Vicente G.; Blasi, Davide; Ratera, Imma; Campaña, Araceli G.; Veciana, Jaume

doi:10.1002/ange.201909398

Cited by 18 publications

(5 citation statements)

References 68 publications

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“…Lately, two racemic triphenylmethyl (trityl) radical-based chlorinated radicals 7 and 8 resolved into their enantiomers were achieved by chiral stationary phase (CSP)HPLC (Figure ). In addition, the chiroptical properties of these enantiomers were studied. As shown in Figure a, the electronic CD (ECD) spectra of P -7/ M- 7 showed mirror-image Cotton effects with main bands.…”

Section: Cpl From Organic Radicalsmentioning

confidence: 99%

“…Right bottom: CPL spectra of (a) P- 7 /M- 7 and (b) P- 8 /M- 8 (P, red line; M, blue line), with excitation wavelength set to the UV–vis C band of (a) 7 and (b) 8 , respectively. Reprinted from ref . Copyright 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.…”

Section: Cpl From Organic Radicalsmentioning

confidence: 99%

“… Photophysical processes, like energy transfer or charge transfer, can significantly affect the g lum since the excited state parameters | m gn | and |μ gn | are sensitive to these processes. Recently, direct regulation of the excited state of chiral emitters through various photophysical approaches provides more flexible ways for amplifying and manipulating the circular polarization of CPL-active materials. − Interestingly, these photophysical approaches show a unique impact on CPL properties without changing the structural and spatial states of chiral emitters. …”

Section: Introductionmentioning

confidence: 99%

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New Perspectives to Trigger and Modulate Circularly Polarized Luminescence of Complex and Aggregated Systems: Energy Transfer, Photon Upconversion, Charge Transfer, and Organic Radical

et al. 2020

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Conspectus Chiral functional materials with circularly polarized luminescence (CPL) have risen rapidly in recent years because of their fascinating characteristics and potential applications in various research fields. CPL refers to the differential spontaneous emission of left (L)- and right (R)-handed circularly polarized light upon photon or electron excitation. Generally, an outstanding CPL-active material needs to possess a high luminescence dissymmetry factor (g lum) (defined as 2(I L – I R)/(I L + I R) where I is the emission intensity), which is between −2 and +2. Although the exciting development in CPL-active materials was achieved, the modulation of CPL signs is still a challenge. For small organic systems, a relatively small g lum value, one of the key parameters of CPL, limits their practical applications. Searching for efficient approaches for amplifying g lum is important. Therefore, over the past decades, besides optimizing the structure of small molecules, many other strategies to obtain efficient CPL-active materials have been developed. For instance, self-assembly has been well demonstrated as an effective approach to amplify the supramolecular chirality as well as the g lum values. On the other hand, chiral liquid crystals (CLCs), which are capable of selective reflection of left- and right-handed circularly polarized light, also to serve as a host matrix for endowing guest emitters with CPL activity and high g lum values. However, self-assembly focuses on modulating the conformation and spatial arrangement of chiral emitters. And the CPL of a luminophore-doped CLC matrix depends on the helix pitch and band gap positions. Lately, novel photophysical approaches to modulate CPL signs have gradually emerged. In this Account, we discuss the recent progress of excited-state-regulation involved CPL-active materials. The emergence, amplification, and inversion of CPL can be adjusted through regulation of the excited state of chiral emitters. For example, Förster resonance energy transfer (FRET) can amplify the g lum values of chiral energy acceptors in chiral supramolecular assemblies. By combining the concepts of photon upconversion and CPL, high-energy upconverted circularly polarized emission was achieved under excitation of low-energy light, accompanied by an amplified g lum. In addition, the organic systems with unpaired electrons, i.e., charge transfer (CT) system and open-shell π-radical, show favorable CPL properties, which can be flexibly tuned with an applied magnetic field. It should be noted that these photophysical process are associated with the excited state of chiral emitters. So far, while the main focus is on the regulation of the molecular and supramolecular nanostructures, direct regulation of the excited state of the chiral system will serve as a new platform to understand and regulate the CPL activity and will be helpful to develop smart chiroptical materials.

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Section: Cpl From Organic Radicalsmentioning

confidence: 99%

Section: Cpl From Organic Radicalsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New Perspectives to Trigger and Modulate Circularly Polarized Luminescence of Complex and Aggregated Systems: Energy Transfer, Photon Upconversion, Charge Transfer, and Organic Radical

et al. 2020

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“…This was a very challenging project during which we were able to present two trityl-based radical derivatives as the first organic radicals acting as intrinsic CPL emitters. 55 56…”

Section: Cumulenic and Diradicaloid Systemsmentioning

confidence: 99%

Nanographenes Out of Planarity

Campaña,

Cruz

2023

Synlett

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The combination of different distortion motifs in nanographenes and polycyclic conjugated hydrocarbons has been the focus of significant attention during the last decade. The continual discovery of multiple carbon allotropes has fueled the field. A plethora of research groups around the globe are engaged in developing methods for the preparation of discrete graphene or fullerene fragments and new carbon allotropes. The goal is to fully understand the structure–property relationships in these systems. Herein, we present our journey and contributions to the field, from the development of a synthetic methodology towards functionalized heptagon-containing hexa-peri-hexabenzocoronenes through the preparation of saddle-helix hybrid nanographenes, the study of heptagon-containing cumulenic and open-shell systems, nanographenes embedded with higher order carbocycles, and the study of their electronic properties on-surface and by single-molecule conductance.1 Introduction2 The Finding of a Cornerstone Scaffold3 Saddle-Helix Hybrid Nanographenes4 Cumulenic and Diradicaloid Systems5 Supramolecular Studies6 Octagon- and Nonagon-Embedded Nanographenes7 Molecular Electronics and On-Surface Studies8 Outlook

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“…In recent years, various photophysical strategies have been developed to regulate the excited states of chiral emitters, including fluorescence resonance energy transfer, [40][41][42] triplet-triplet annihilation-based photon upconversion (TTA-UC), [43][44][45] charge transfer, 46,47 and organic radical emission. 48,49 While these strategies provide a flexible means of amplifying and manipulating CPL properties, they often result in a loss of emission efficiency. Therefore, it is important to establish a novel platform to improve the overall CPL performance of these materials.…”

Section: Introductionmentioning

confidence: 99%