RESUMEN
Organic small molecules exhibiting both thermally activated delayed fluorescence (TADF) and wide-ranging piezochromism (Δλ > 150 nm) in the near-infrared region have rarely been reported in the literature. We present three emitters MeTPA-BQ, tBuTPA-BQ and TPPA-BQ based on a hybrid acceptor, benzo[g]quinoxaline-5,10-dione, that emit via TADF, having photoluminescence quantum yields, ΦPL, of 39-42% at photoluminescence (PL) maxima, λPL, of 625-670 nm in 2 wt% doped films in 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP). Despite their similar chemical structures, the PL properties in the crystalline states of MeTPA-BQ (λem = 735 nm, ΦPL = 2%) and tBuTPA-BQ (λem = 657 nm, ΦPL = 11%) are significantly different. Further, compounds tBuTPA-BQ and TPPA-BQ showed a significant PL shift of â¼98 and â¼165 nm upon grinding of the crystalline samples, respectively. Deep-red organic light-emitting diodes with MeTPA-BQ and tBuTPA-BQ were also fabricated, which showed maximum external quantum efficiencies, EQEmax, of 10.1% (λEL = 650 nm) and 8.5% (λEL = 670 nm), respectively.
RESUMEN
The development of materials that emit in the deep-red to near-infrared region of the spectrum has attracted significant attention due to their potential as optical sensing and imaging reagents in biology. Herein, we report the synthesis and optoelectronic characterization of four anthraquinone-based emitters, T-tBuCz-AQ, T-MeOCz-AQ, C-tBuCz-AQ, and C-MeOCz-AQ, and two pyrazoloanthrone-based emitters, tBuCz-PA and DMAC-PA. Depending on the donor, these compounds emit in the spectral range between 640 and 750 nm in the neat film, while the emission of the 10 wt% doped films in poly(methyl methacrylate) (PMMA) is blue-shifted between 600 and 700 nm and has low photoluminescence quantum yields between 2.6% and 6.6%. Of these compounds, T-tBuCz-AQ, T-MeOCz-AQ, and C-tBuCz-AQ exhibited thermally activated delayed fluorescence (TADF) in 10 wt% doped films in PMMA, while the crystals of T-tBuCz-AQ also showed TADF. Compound tBuCz-PA showed a high-contrast and reversible photoluminescence (PL) response upon mechanical grinding and hexane fuming.
RESUMEN
We present a new class of blue circularly polarized luminescent emitters based on tetraarylaminoborane (TAAB) with considerable dissymmetry factor in the solid state. The chiral pendant 1-phenylethylamine in BN-RR and BN-SS imparts chirality to the core chromophore, resulting in circularly polarized luminescence signals (glum = 0.8 × 10-3) with a quantum yield of 33% in the crystalline state. This novel set of compounds also showcases intriguing thermally reversible piezochromism.
RESUMEN
Extensive research has been devoted to the development of thermally activated delayed fluorescence emitters, especially those showing pure-blue emission for use in lighting and full-color display applications. Toward that goal, herein we report a novel weak donor, 1,4-azaborine (AZB), with complementary electronic and structural properties compared to the widely used dimethylacridan (DMAC) or carbazole (Cz) donors. Coupled with a triazine acceptor, AZB-Ph-TRZ is the direct structural analogue of the high-performance and well-studied green TADF emitter DMAC-TRZ and has ΔEST = 0.39 eV, a photoluminescence quantum yield (ΦPL) of 27%, and λPL = 415 nm in 10 wt % doped mCP films. The shortened analogue AZB-TRZ possesses red-shifted emission with a reduced singlet-triplet gap (ΔEST = 0.01 eV) and fast reverse intersystem crossing (kRISC of 5 × 106 s-1) in mCP. Despite a moderate ΦPL of 34%, OLEDs with AZB-TRZ in mCP showed sky-blue emission with CIE1931(x,y) of (0.22,0.39) and a maximum external quantum efficiency (EQEmax) of 10.5%. Expanding the chemist's toolkit for the design of blue donor-acceptor TADF materials will enable yet further advances in the future, as AZB is paired with a wider range of acceptor groups.
RESUMEN
The ultrasonic technique has received considerable attention in several fields; in particular, it gained rapid momentum in organic synthesis due to the larger reaction rates, milder reaction conditions, and better yields. We report herein a facile synthesis of a series of styrylpyridinium based dyes under ultrasonic irradiation. Within short reaction time (15 min) under ultrasonic irradiation, compared to normal laboratory conditions, (4-16 h), we can achieve good to excellent yields. The reaction time is shortened because ultrasound can accelerate the generation of the nucleophile of the pyridinium salt and subsequently a nucleophilic addition of an aldehyde followed by dehydration affords the styrylpyridinium dye, (Knoevenagel condensation). The photophysical properties of all compounds are comprehensively investigated in different solvents. All the compounds exhibit negative solvatochromism both in absorption and fluorescence emission spectra. Such behavior is due to the higher dipole moment of these molecules at the ground state. DFT calculations were performed to understand the electronic structure of the molecules. Our results show the high efficacy of sonochemistry over other methods for preparation of styrylpyridinium dyes.
RESUMEN
Herein, the design, synthesis, optical properties, and mechanofluorochromism characteristics of a series of conjugates having covalently linked triarylborane (TAB) and anil/boranil units (TAB-anil: 1 a-3 a and TAB-boranil: 1-3) are reported. The electronic interactions between TAB and anil/boranil in 1 a-3 a and 1-3 were fine-tuned by changing the boryl moiety's position on the phenyl spacer connecting the BMes2 (Mes=mesityl) and anil/boranil units. A boryl moiety at the meta position (1 a) of the phenyl spacer stabilizes the enolic form (E-OH), whereas a boryl moiety at the para position (2 a and 3 a) stabilizes the keto form (Z-NH) in the solid state. However, in solution 1 a, 2 a, and 3 a exhibit keto-enol tautomerism in both ground and excited states. Compoundsâ 1 a-3 a and 1-3 show red-shifted absorption compared with 4 a and 4, which are devoid of TAB moieties, which indicate effective participation of an empty p orbital on the boron center in 1 a-3 a and 1-3. Compoundsâ 1 and 2 showed fluorescence variations in response to external stimuli such as mechanical grinding. Long phosphorescence lifetimes of 18-46â ms were observed for compoundsâ 1-3. The observed optical properties of 1 a-3 a and 1-3 are rationalized in the context of quantum mechanical calculations.
RESUMEN
Molecular materials with weak but extended and pliable supramolecular interactions are versatile candidates for eliciting stimuli-sensitive optical responses. A novel diaminodicyanoquinodimethane (DADQ) molecule, 7,7-bis(2-(2-pyridyl)ethylamino)-8,8-dicyanoquinodimethane (BPEDQ), has been synthesized and structurally characterized; it exhibits enhanced fluorescence emission in the aggregated and solid states, characteristic of DADQs. The pyridine moieties in the molecule, in addition to the amino and cyano groups of the strongly dipolar fluorophore moiety, induce extensive H-bonding interactions which can impart structural integrity to the solid material; this enables reversible crystalline-amorphous transformations triggered by mechanical grinding and solvent fuming. The concomitant fluorescence color and intensity switching are prominent and reversible. Protonation-deprotonation events induced by acidic and basic vapors also produce stark fluorescence response variations; the chemical stimuli also lead to amorphization of the solid. The full cycle of chemical and physical stimuli, and the consequence of their individual and coupled impact on the fluorescence emission, are illustrated using a BPEDQ-doped polymer thin film.
RESUMEN
Triarylboryl appended perylenediimide (PDI-TAB) is designed and synthesized. The incorporation of triarylboranes (TABs) decreases self-aggregation and increases the solubility of PDI-TAB in common organic solvents. Fluorescence emission colors ranging from red, yellow and green are realized by judiciously modulating the concentration of PDI-TAB in solution. The morphology and dimensions of the self-assemblies formed by PDI-TAB can be controlled by changing the experimental conditions. For example, PDI-TAB forms fibers of finite length when bulk powder is dispersed in methanol; it shows flexible lengthy 1D fibers when dichloromethane solution of PDI-TAB is injected into methanol solvent. PXRD analysis indicates that the molecular organization remains the same in both cases. PDI-TAB functions as a selective fluorogenic sensor for toxic fluoride anions; the sensing mechanism is explained by using theoretical calculations.
RESUMEN
A photoredox-catalyst- and template-free sunlight-induced molecular dimerization of a vinylpyridine-functionalized tetraarylaminoborane (TAAB) has been accomplished for the first time. The reaction is quantitative, highly regioselective, and thermally irreversible. The presence of the propeller-shaped TAAB framework allows selective photodimerization of one of the two vinyl pyridine units. Monomer 1 and photodimer 2 exhibit distinct photophysical properties with delayed fluorescence (DF) both in solution and the solid state, which was confirmed by steady-state and time-resolved luminescence studies. Quantum mechanical calculations were performed to support the experimental observations. Our new approach using [2+2] cycloaddition chemistry paves the way for the development of highly sought-after deep-blue DF materials.
RESUMEN
Herein we report the multifunctional characteristics such as aggregation induced emission (AIE), triboluminescence (TL), mechanofluorochromism and temperature sensing of molecular siblings 1 (10-(dimesitylboryl)phenothiazine) and 2 (10-(bis(2,6-dimethylphenyl)boryl)phenothiazine).