Photoluminescent discotic liquid crystals derived from tris( N -salicylideneaniline) and stilbene conjugates: Structure–property correlations

Achalkumar, Ammathnadu S.; Veerabhadraswamy, B. N.; Hiremath, Uma S.; Rao, D. S. Shankar; Prasad, S. Krishna; Yelamaggad, C. V.

doi:10.1016/j.dyepig.2016.05.010

Cited by 30 publications

(19 citation statements)

References 60 publications

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“…Recently, our group developed families of pentafluorinated tolane [13] and bistolane derivatives with alkoxy-type flexible chains (Figure 1a) [14,15] as promising LE materials and revealed that their PL can change depending on the electron-density distribution [16] or the molecular arrangement in the aggregated structure [13][14][15]. It was of great interest that the bistolane-type LE molecules showed not only PL, but also liquid-crystalline (LC) properties, namely light-emitting liquid crystals 2 of 16 (LELCs) [17][18][19][20], and the PL behaviors were found to change through the crystal (Cr) LC thermal phase transition. In addition, we recently developed novel LELCs with V-or Y-shaped molecular geometry, which showed intriguing switching characteristics induced by thermal stimulus [21].…”

Section: Introductionmentioning

confidence: 99%

2-Chloroalkoxy-Substituted Pentafluorinated Bistolanes as Novel Light-Emitting Liquid Crystals

et al. 2019

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In this study, we designed and synthesized novel pentafluorinated bistolane derivatives with 2-chloropentyl or 2-chlorohexyl flexible units as novel light-emitting liquid crystals (LELCs). By measuring the phase-transition behaviors, all derivatives were found to display liquid-crystalline (LC) phases during both heating and cooling processes. Among the novel bistolanes, the S- and R-configured derivatives exhibited a chiral nematic (N*) phase with a typical Grandjean optical texture. Interestingly, the chiral derivatives also exhibited a blue phase with a typical platelet texture in a narrow temperature range (2–4 °C). Photophysical measurements revealed that the 2-chloroalkoxy-substituted pentafluorinated bistolanes exhibited intense photoluminescence (PL) both in solution and in crystalline phases. The PL characteristics, especially the maximum PL wavelength, were found to switch sensitively during the heating and cooling cycles depending on the molecular aggregates through the crystal (Cr) ⇄ N* phase transition. The 2-chloroalkoxy flexible units induced dynamic changes in the LC and PL properties, providing valuable insight into the potential of various LELCs as PL sensing materials.

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Section: Introductionmentioning

confidence: 99%

2-Chloroalkoxy-Substituted Pentafluorinated Bistolanes as Novel Light-Emitting Liquid Crystals

et al. 2019

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“…Light-emitting liquid crystals show intriguing optical characteristics in various molecular arrangements formed through phase transition by applying external heat or an electrical stimulus. 12,13 Among such light-emitting liquid crystals, our LC bistolane derivative ( 1 ) demonstrated to show intriguing switching of their PL behavior through the phase transition between the Cr ⇄ LC phases. 10b,14 The temperature-dependent PL switching was likely attributable to a dynamic change in molecular aggregation via a thermal phase transition.…”

Section: Introductionmentioning

confidence: 99%

Novel V- and Y-Shaped Light-Emitting Liquid Crystals with Pentafluorinated Bistolane-Based Luminophores

et al. 2019

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Herein, we describe the synthesis of novel light-emitting liquid-crystalline (LC) compounds bearing pentafluorinated bistolane-based luminophores with a V- or a Y-shaped molecular geometry and the evaluation of their LC and photophysical characteristics. The V- or Y-shaped compounds exhibited a unique LC phase and showed photoluminescence (PL) behavior under various circumstances, such as in dilute solution or in the solid state. Notably, PL characteristics were observed even under high-temperature conditions with a crystal (Cr) to LC phase transition, although the PL efficiency ( Φ PL ) was gradually reduced because of thermal molecular motion. Interestingly, Φ PL was found to be completely recovered through the LC → Cr phase transition during the cooling process; the PL characteristics of the V- or Y-shaped compounds were sensitively changed by external thermal stress, giving these compounds the ability to act as thermoresponsive PL sensing materials.

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“…[8] General Figure S1. Absorption (black curve) and emission (red curve) spectra of (a) BPM-(R)-C8(2) (C = 2.53x10 To relate the average effective nonlinear optical coefficient at room temperature to its value at different temperatures the following formula was used:…”

Section: Differential Scanning Calorimetry (Dsc) Andmentioning

confidence: 99%

“…[8] However, crystalline materials lack processability and growing large high-quality crystals remains challenging. Alternatively, NLO activity can be achieved in polymeric films by using the "poling process", in which a strong electric field is applied to align dipolar organic chromophores inside a polymer matrix near its glass transition temperature (T g ).…”

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Chiral Side Groups Trigger Second Harmonic Generation Activity in 3D Octupolar Bipyrimidine‐Based Organic Liquid Crystals

et al. 2017

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Abstract.Design of organic noncentrosymmetric materials remains the Holy Grail in the field of second-order nonlinear optics. Unlike inorganic crystals currently used in second-order nonlinear optical applications, organic materials represent an attractive alternative due to their fast electro-optical response and processability, but their alignment into noncentrosymmetric film still remains challenging. Here, symmetry breaking by judicious functionalization of 3D organic octupoles allows the emergence of multifunctional liquid crystalline chromophores which can easily be processed into large, flexible, thin and self-oriented films presenting second harmonic generation responses competitive to the prototypical inorganic KH 2 PO 4 crystals. Additionally, liquid crystalline nature of these chiral organic films permits the modulation of the nonlinear optical properties due to the sensitivity of the supramolecular organization to temperature leading to the development of tunable macroscopic material. The development of numerous nonlinear optical (NLO) inorganic crystals, such as BaB 2 O 4 (BBO), [2] LiB 3 O 5 (LBO), [3] KH 2 PO 4 (KDP), [4] KTiOPO 4 (KTP), [5] AgGaS 2 (AGS) [6] and AgGaGeS 4 (AGGS), [7] has led to significant advances in the application of laser devices from UV to IR spectral wavelengths.NCS crystals of organic molecules such as nitroaniline derivatives are efficient for second order applications as well. [8] However, crystalline materials lack processability and growing large high-quality crystals remains challenging. Alternatively, NLO activity can be achieved in polymeric films by using the "poling process", in which a strong electric field is applied to align dipolar organic chromophores inside a polymer matrix near its glass transition temperature (T g ). Unfortunately, after cooling, the obtained NLO-active polymeric materials lack long-term stability and reproducibility of the preparation process, while the strong electric fields used during the poling process can lead to degradation. The Langmuir-Blodgett film deposition technique has also been used to create NCS films using amphiphilic chromophores but the tedious monolayer-by-monolayer deposition method remains a main obstacle. [10] Liquid crystalline materials open another route for creating functional organic NLO materials.They offer numerous advantages such as their ease of processing into high-quality thin films, their self-healing capacity and the possibility of alignment by shear forces, surface treatment or electric or magnetic fields.[11]The formation of NCS liquid crystals containing optically active cores is a promising way to achieve efficient organic thin films for SHG.Engineering organic liquid crystalline materials for second-order nonlinear optical applications is challenging, since at least 3 requirements must be met: i) a large molecular NLO response (i.e. first hyperpolarizability β), requiring NCS on the molecular level, ii) liquid crystalline behavior and iii) a supramolecular NCS organization. Since this approach re...

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Photoluminescent discotic liquid crystals derived from tris( N -salicylideneaniline) and stilbene conjugates: Structure–property correlations

Cited by 30 publications

References 60 publications

2-Chloroalkoxy-Substituted Pentafluorinated Bistolanes as Novel Light-Emitting Liquid Crystals

2-Chloroalkoxy-Substituted Pentafluorinated Bistolanes as Novel Light-Emitting Liquid Crystals

Novel V- and Y-Shaped Light-Emitting Liquid Crystals with Pentafluorinated Bistolane-Based Luminophores

Chiral Side Groups Trigger Second Harmonic Generation Activity in 3D Octupolar Bipyrimidine‐Based Organic Liquid Crystals

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