Recent Progress in the Development of Solid‐State Luminescent <i>o</i>‐Carboranes with Stimuli Responsivity

Ochi, Junki; Tanaka, Kazuo; Chujo, Yoshiki

doi:10.1002/ange.201916666

Cited by 51 publications

(32 citation statements)

References 87 publications

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“…The designed structure is believed to separate the two PBI units in a suitable distance owing to the steric structure of o-carborane, endowing them with partial rotational freedom. 58 The bay position modified PBI derivative was selected as the chromophore not only because of its superior fluorescence properties as aforementioned, but also because of its acceptable solubility in common organic solvents to avoid the strong tendency of forming intermolecular aggregates. This design enables us to mainly focus on the intramolecular excitonic interactions of two PBI moieties and their interplay between two different configurations (vide infra).…”

Section: Introductionmentioning

confidence: 99%

Excimer Formation of Perylene Bisimide Dyes within Stacking-Restrained Folda-Dimers: Insight into Anomalous Temperature Responsive Dual Fluorescence

et al. 2022

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By tethering two PBI moieties to the ortho-carbon positions of a carborane unit, we are able to build up a new PBI folda-dimer (BPBI-CB-1). The synthesized compound adopts different configurations in different solvents with dual emissions as its characteristic. The two PBI moieties in the molecule are either appearing in a weakly interacted, monomer-like state or brought in close π-π contact to each other, forming an interacted stacking state. The equilibrium between these two states is governed by the nature of solvents and testing temperature.Spectroscopic and theoretical studies conclude that dual emission bands originate from intramolecular monomer-like and stacking states, respectively. Remarkably, in certain solvent such as 1,2-dichloroethane, both emission intensities increase with raising temperature. The positive temperature response of the monomer emission is ascribed to increased amount of monomer-like population owing to its endothermic energy state, while for the excimer emission it is rationalized by the increase of the population in bright exciton state, resulting in an increase of emission yield that compensates the decrease of the population of the stacking state. To our knowledge, this is the first report on positive temperature responsive dual emissions associated with the synergism of intramolecular inter-subunit aggregation/dissociation and excimer transformation.

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Section: Introductionmentioning

confidence: 99%

Excimer Formation of Perylene Bisimide Dyes within Stacking-Restrained Folda-Dimers: Insight into Anomalous Temperature Responsive Dual Fluorescence

et al. 2022

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“…Over the past few decades, π-conjugated aromatic compounds bearing an icosahedral c loso - ortho -carborane ( closo - o -1,2-C 2 B 10 H 12 ) cluster have been extensively investigated [ 1 , 2 , 3 , 4 , 5 ] because of their unique photophysical properties and reasonable electrochemical stabilities [ 1 , 3 , 6 , 7 , 8 ]. Owing to these features, such o -carboranyl compounds have recently been proposed as promising optoelectronic materials for organic light emitting diodes [ 7 , 8 ] and organic thin-film transistors [ 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

“…Owing to these features, such o -carboranyl compounds have recently been proposed as promising optoelectronic materials for organic light emitting diodes [ 7 , 8 ] and organic thin-film transistors [ 9 , 10 ]. The intriguing photophysical properties of o -carboranyl luminophores originate from the electronic donor‒acceptor (D–A) dyad formed by combining a π-conjugated aromatic organic fluorophore (donor) with an o -carborane (acceptor) [ 4 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. The strong electron-withdrawing ability of the carbon atoms in the o -carborane cage, which is derived from the high polarizability of the σ-aromaticity [ 37 , 38 , 39 , 40 , 41 ], allows this moiety to act as an electron acceptor during external excitation and relaxation processes.…”

Section: Introductionmentioning

confidence: 99%

“…The strong electron-withdrawing ability of the carbon atoms in the o -carborane cage, which is derived from the high polarizability of the σ-aromaticity [ 37 , 38 , 39 , 40 , 41 ], allows this moiety to act as an electron acceptor during external excitation and relaxation processes. As a result, intramolecular charge transfer (ICT) can be induced between aromatic groups and the o -carborane cage [ 2 , 4 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. The luminescence behavior of o -carborane-based D‒A dyads is characterized by the radiative decay of the ICT transition [ 2 , 4 , 7 , 8 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ,…”

Section: Introductionmentioning

confidence: 99%

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Influence of Electronic Environment on the Radiative Efficiency of 9-Phenyl-9H-carbazole-Based ortho-Carboranyl Luminophores

Lee

Mun

et al. 2021

Molecules

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The photophysical properties of closo-ortho-carboranyl-based donor–acceptor dyads are known to be affected by the electronic environment of the carborane cage but the influence of the electronic environment of the donor moiety remains unclear. Herein, four 9-phenyl-9H-carbazole-based closo-ortho-carboranyl compounds (1F, 2P, 3M, and 4T), in which an o-carborane cage was appended at the C3-position of a 9-phenyl-9H-carbazole moiety bearing various functional groups, were synthesized and fully characterized using multinuclear nuclear magnetic resonance spectroscopy and elemental analysis. Furthermore, the solid-state molecular structures of 1F and 4T were determined by X-ray diffraction crystallography. For all the compounds, the lowest-energy absorption band exhibited a tail extending to 350 nm, attributable to the spin-allowed π–π* transition of the 9-phenyl-9H-carbazole moiety and weak intramolecular charge transfer (ICT) between the o-carborane and the carbazole group. These compounds showed intense yellowish emission (λem = ~540 nm) in rigid states (in tetrahydrofuran (THF) at 77 K and in films), whereas considerably weak emission was observed in THF at 298 K. Theoretical calculations on the first excited states (S1) of the compounds suggested that the strong emission bands can be assigned to the ICT transition involving the o-carborane. Furthermore, photoluminescence experiments in THF‒water mixtures demonstrated that aggregation-induced emission was responsible for the emission in rigid states. Intriguingly, the quantum yields and radiative decay constants in the film state were gradually enhanced with the increasing electron-donating ability of the substituent on the 9-phenyl group (‒F for 1F < ‒H for 2P < ‒CH3 for 3M < ‒C(CH3)3 for 4T). These features indicate that the ICT-based radiative decay process in rigid states is affected by the electronic environment of the 9-phenyl-9H-carbazole group. Consequently, the efficient ICT-based radiative decay of o-carboranyl compounds can be achieved by appending the o-carborane cage with electron-rich aromatic systems.

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“…The diverse regioreactivity of o -carborane, has been exploited and adapted to make o -carborane an exceptional core for developing a large variety of multibranched molecules, globular macromolecules, dendrimers ( Figure 2 b), and so on [ 14 , 15 , 16 , 17 , 18 ]. Moreover, new versatile synthons have been explored through the multi-functionalization of B and C c atoms jointly, which make the o -carborane clusters an exciting platform for new materials [ 6 , 8 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ].…”

Section: Introductionmentioning

confidence: 99%

m-Carborane as a Novel Core for Periphery-Decorated Macromolecules

et al. 2020

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Closo m-C2B10H12 can perform as a novel core of globular periphery-decorated macromolecules. To do this, a new class of di and tetrabranched m-carborane derivatives has been synthesized by a judicious choice of the synthetic procedure, starting with 9,10-I2-1,7-closo-C2B10H10. The 2a-NPA (sum of the natural charges of the two bonded atoms) value for a bond, which is defined as the sum of the NPA charges of the two bonded atoms, matches the order of electrophilic reaction at the different cluster bonds of the icosahedral o-and m- carboranes that lead to the formation of B-I bonds. As for m-carborane, most of the 2a-NPA values of B-H vertexes are positive, and their functionalization is more challenging. The synthesis and full characterization of dibranched 9,10-R2-1,7-closo-carborane (R = CH2CHCH2, HO(CH2)3, Cl(CH2)3, TsO(CH2)3, C6H5COO(CH2)3, C6H5COO(CH2)3, N3(CH2)3, CH3CHCH, and C6H5C2N3(CH2)3) compounds as well as the tetrabranched 9,10-R2-1,7-R2-closo-C2B10H8 (R = CH2CHCH2, HO(CH2)3) are presented. The X-ray diffraction of 9,10-(HO(CH2)3)2-1,7-closo-C2B10H10 and 9,10-(CH3CHCH)2-1,7-closo-C2B10H10, as well as their Hirshfeld surface analysis and decomposed fingerprint plots, are described. These new reported tetrabranched m-carborane derivatives provide a sort of novel core for the synthesis of 3D radially grown periphery-decorated macromolecules that are different to the 2D radially grown core of the tetrabranched o-carborane framework.

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Recent Progress in the Development of Solid‐State Luminescent o‐Carboranes with Stimuli Responsivity

Cited by 51 publications

References 87 publications

Excimer Formation of Perylene Bisimide Dyes within Stacking-Restrained Folda-Dimers: Insight into Anomalous Temperature Responsive Dual Fluorescence

Excimer Formation of Perylene Bisimide Dyes within Stacking-Restrained Folda-Dimers: Insight into Anomalous Temperature Responsive Dual Fluorescence

Influence of Electronic Environment on the Radiative Efficiency of 9-Phenyl-9H-carbazole-Based ortho-Carboranyl Luminophores

m-Carborane as a Novel Core for Periphery-Decorated Macromolecules

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