scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Highly Elastic Organic Crystals for Flexible Optical Waveguides.

Huapeng Liu1, Zhuoqun Lu1, Zuolun Zhang1, Yue Wang1, Hongyu Zhang1 
09 Jul 2018-Angewandte Chemie (Angew Chem Int Ed Engl)-Vol. 57, Iss: 28, pp 8448-8452
TL;DR: An elastic crystal of a Schiff base, (E)-1-(4-(dimethylamino)phenyl)iminomethyl-2-hydroxyl-naphthalene, which is highly bendable under external stress and able to regain immediately its original straight shape when the stress is released can serve as a low-loss optical waveguide even at the highly bent state.
Abstract: The study of elastic organic single crystals (EOSCs) has emerged as a cutting-edge research of crystal engineering. Although a few EOSCs have been reported recently, those suitable for optical/optoelectronic applications have not been realized. Here, we report an elastic crystal of a Schiff base, (E)-1-(4-(dimethylamino)phenyl)iminomethyl-2-hydroxyl-naphthalene. The crystal is highly bendable under external stress and able to regain immediately its original straight shape when the stress is released. It displays bright orange-red emission with a high fluorescence quantum yield of 0.43. Intriguingly, it can serve as a low-loss optical waveguide even at the highly bent state. Our result highlights the feature and utility of "elasticity" of organic crystals.
Citations
More filters
Journal ArticleDOI
TL;DR: This Account describes efforts at focusing down into mechanical properties of organic molecular crystals from the viewpoint of crystal engineering, which is the synthesis and design of functional molecular solids and presents examples where complex properties may be deliberately turned on or off in organic crystals.
Abstract: ConspectusMechanical properties of organic molecular crystals have been noted and studied over the years but the complexity of the subject and its relationship with diverse fields such as mechanochemistry, phase transformations, polymorphism, and chemical, mechanical, and materials engineering have slowed understanding. Any such understanding also needs conceptual advances—sophisticated instrumentation, computational modeling, and chemical insight—lack of such synergy has surely hindered progress in this important field. This Account describes our efforts at focusing down into this interesting subject from the viewpoint of crystal engineering, which is the synthesis and design of functional molecular solids. Mechanical properties of soft molecular crystals imply molecular movement within the solid; the type of property depends on the likelihood of such movement in relation to the applied stress, including the ability of molecules to restore themselves to their original positions when the stress is removed...

288 citations

Journal ArticleDOI
TL;DR: The most recent developments in the research of adaptive molecular crystals are highlighted and their assets and pitfalls are discussed, providing some hints on the likely future developments that capitalize on the untapped, sequestered potential for applications of this distinct materials class.
Abstract: The anticipated shift in the focal point of interest of solid-state chemists, crystal engineers, and crystallographers from structure to properties to function parallels the need to apply our accumulated understanding of the intricacies of crystal structure to explaining the related properties, with the ultimate goal of harnessing that knowledge in applications that require soft, lightweight, or biocompatible organic solids. In these developments, the adaptive molecular crystals warrant particular attention as an alternative choice of materials for light, flexible, and environmentally benign devices, primarily memories, capacitors, sensors, and actuators. Some of the outstanding requirements for the application of these dynamic materials as high-efficiency energy-storage devices are strongly induced polarization, a high switching field, and narrow hysteresis in the case of reversible dynamic processes. However, having been studied almost exclusively by chemists, molecular crystals still lack the appropriate investigations that reliably evaluate their reproducibility, scalability, and actuating performance, and some important drawbacks have diverted the interest of engineers from these materials in applications. United under the umbrella term crystal adaptronics, the recent research efforts aim to realistically assess the appositeness of dynamic crystals for applications that require fast, reversible, and continuous operation over prolonged periods of time. With the aim of highlighting the most recent developments, this Perspective discusses their assets and pitfalls. It also provides some hints on the likely future developments that capitalize on the untapped, sequestered potential of this distinct materials class for applications.

174 citations

Journal ArticleDOI
TL;DR: A rare one-dimensional optical waveguiding crystal of dithieno[3,2-a:2',3'-c]phenazine with high aspect ratio displaying high mechanical flexibility and selective self-absorbance of the blue part of its fluorescence (FL) is presented.
Abstract: We present the one-dimensional optical-waveguiding crystal dithieno[3,2-a:2',3'-c]phenazine with a high aspect ratio, high mechanical flexibility, and selective self-absorbance of the blue part of its fluorescence (FL). While macrocrystals exhibit elasticity, microcrystals deposited at a glass surface behave more like plastic crystals due to significant surface adherence, making them suitable for constructing photonic circuits via micromechanical operation with an atomic-force-microscopy cantilever tip. The flexible crystalline waveguides display optical-path-dependent FL signals at the output termini in both straight and bent configurations, making them appropriate for wavelength-division multiplexing technologies. A reconfigurable 2×2-directional coupler fabricated via micromanipulation by combining two arc-shaped crystals splits the optical signal via evanescent coupling and delivers the signals at two output terminals with different splitting ratios. The presented mechanical micromanipulation technique could also be effectively extended to other flexible crystals.

140 citations

Journal ArticleDOI
TL;DR: Two fluorescent and highly flexible organic crystals (1 and 2) which could bend under an applied stress are reported on, which showed a unique bending mechanofluorochromism.
Abstract: To create low band-gap, fluorescent, and elastic organic crystal emitters, we focused on an extended π-conjugated system based on: a) a planar conformation,b) a rigid structure, and c) controlled intermolecular interactions. Herein, we report on two fluorescent and highly flexible organic crystals (1 and 2) which could bend under an applied stress. The bent crystals rapidly recover their straight shape upon release of the stress. Crystal 1 with a tetrafluoropyridyl terminal unit and a lower band-gap energy (orange emission, λem =573 nm, ΦF =0.50), showed no bending mechanofluorochromism and had superior performance as an optical waveguide with reddish orange emission. The waveguide performance of the crystal did not decrease under bending stress. For crystal 2 with a pentafluorophenyl terminal unit (green emission, λem =500 nm, ΦF =0.38), the original waveguide performance decreased under an applied bending stress; however, this crystal showed a unique bending mechanofluorochromism.

139 citations

Journal ArticleDOI
TL;DR: This prototypical dual-mode organic optical crystalline fiber brings mechanically compliant molecular organic crystals closer to applications as novel light-transducing media for wireless transfer of information in all-organic micro-optoelectronic devices.
Abstract: An anthracene derivative, 9,10-dicyanoanthracene, crystallizes as fluorescent needle-like single crystals that can be readily plastically bent in two directions. Spatially resolved photoluminescence analysis revealed that this material has robust optoelectronic properties that are preserved upon extreme crystal deformation. The highly flexible crystals were successfully tested as efficient switchable optical waveguiding elements for both active and passive light transduction, and the mode of operation depends on the wavelength of the incident light. This prototypical dual-mode organic optical crystalline fiber brings mechanically compliant molecular organic crystals closer to applications as novel light-transducing media for wireless transfer of information in all-organic micro-optoelectronic devices.

138 citations

References
More filters
Journal ArticleDOI
TL;DR: This paper presents a meta-analyses of the chiral stationary phase of the H2O/O2 mixture and shows clear trends in the direction of increasing chiral insensitivity to Naumov’s law.
Abstract: Pancě Naumov,*,† Stanislav Chizhik,‡,§ Manas K. Panda,† Naba K. Nath,† and Elena Boldyreva*,‡,§ †New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates ‡Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of Russian Academy of Sciences, ul. Kutateladze, 18, Novosibirsk 630128, Russia Novosibirsk State University, ul. Pirogova, 2, Novosibirsk 630090, Russia

572 citations

Journal ArticleDOI
TL;DR: A remarkably flexible, elastically bendable cocrystal solvate 1 is reported, formed from caffeine, 4-chloro-3-nitrobenzoic acid, and methanol in a 1:1:< 1 ratio (Figure 1).
Abstract: Molecular crystals are among the most ancient and highly investigated materials in chemistry. However, mechanical properties of these materials have remained relatively unexplored despite their unique applications in optoelectronics, mechanical actuators, artificial muscles, pharmaceuticals, and explosives. Conserving the orientational order of molecules and bonds is important for efficient charge transport and for the lifetime of organic light-emitting diodes, transistors, and solar cells. Hence, the realization of high-performance materials with excellent self-healing capabilities or efficient stress dissipating behaviors is attractive. For this reason, the remarkable properties displayed by natural fibres such as spider silk, muscle protein titin, cytoskeleton microtubules, etc. have recently sparked tremendous interest in establishing a reliable structure–property correlation to guide the design of their mimics for various applications. A good starting point for achieving such a goal is to study much simpler and easy-to-characterize organic crystals, which selfassemble through the same noncovalent interactions. It remains a challenge to simultaneously achieve both flexibility and crystallinity in organic materials because crystallinity positively correlates with brittleness. For example, compared to highly ordered molecular crystals, liquid crystals show greater flexibility, but are less crystalline. Desiraju and co-workers showed irreversible mechanical bending in organic crystals as mediated by the movement of molecular sheets through weak interactions between them. The plastic deformation disrupts the long-range order permanently. It was also shown that reversible molecular movements in organic crystals (e.g., in photomechanical bending), can perform work in devices. Herein we report a remarkably flexible, elastically bendable cocrystal solvate 1, formed from caffeine (CAF), 4-chloro-3-nitrobenzoic acid (CNB), and methanol in a 1:1:< 1 ratio (Figure 1). The cocrystal solvate 1 retains a high internal order through an efficient stress dissipation mechanism, and hence is important in the context of crystal engineering and for the design of flexible organic materials. The single crystals of 1 could be obtained from a 1:1 molar solution of CAF and CNB in methanol by using a slow evaporation method (Figure 1). H NMR and thermogravimetric (TG) analyses have confirmed the presence of CAF, CNB, and methanol molecules in a 1:1:< 1 ratio within the lattice (see Figures S1 and S2 in the Supporting Information). The typically long needle crystals of 1 grow along the a axis (Figure 1 and Figure S4). When a straight crystal, having about a 0.1 mm thickness and 5 mm length, was pushed with a metal pin while being held with a pair of forceps (tweezers) from the opposite end, it transformed into a bent shape without breaking (Figure 2a–d and Figure S5). Further, it could be made into a loop by joining the two ends with a smooth curve (see Videos S1–S3 in the Supporting Information). Upon withdrawal of the force, the crystal quickly Figure 1. Single-crystal preparation of the cocrystal solvate 1 from a methanol solution of caffeine and 4-chloro-3-nitrobenzoic acid.

294 citations

Journal ArticleDOI
TL;DR: The morphostructural consequences of plastic deformation in crystals of hexachlorobenzene that can be bent mechanically at multiple locations to 360° with retention of macroscopic integrity are described.
Abstract: The exceptional mechanical flexibility observed with certain organic crystals defies the common perception of single crystals as brittle objects. Here, we describe the morphostructural consequences of plastic deformation in crystals of hexachlorobenzene that can be bent mechanically at multiple locations to 360° with retention of macroscopic integrity. This extraordinary plasticity proceeds by segregation of the bent section into flexible layers that slide on top of each other, thereby generating domains with slightly different lattice orientations. Microscopic, spectroscopic and diffraction analyses of the bent crystal showed that the preservation of crystal integrity when stress is applied on the (001) face requires sliding of layers by breaking and re-formation of halogen-halogen interactions. Application of stress on the (100) face, in the direction where π···π interactions dominate the packing, leads to immediate crystal disintegration. Within a broader perspective, this study highlights the yet unrecognized extraordinary malleability of molecular crystals with strongly anisotropic supramolecular interactions.

234 citations

Journal ArticleDOI
TL;DR: The study, which reports the preparation of a series of exotic plastic crystals by design for the first time, demonstrates the potential of soft interactions for tuning the mechanical behavior of ordered molecular materials, including those from π-conjugated systems.
Abstract: Controlling mechanical properties of ordered organic materials remains a formidable challenge, despite their great potential for high performance mechanical actuators, transistors, solar cells, photonics, and bioelectronics. Here we demonstrate a crystal engineering approach to design mechanically reconfigurable, plastically flexible single crystals (of about 10) of three unrelated types of compounds by introducing active slip planes in structures via different noninterfering supramolecular weak interactions, namely van der Waals (vdW), π-stacking, and hydrogen bonding groups. Spherical hydrophobic groups, which assemble via shape complementarity (shape synthons), reliably form low energy slip planes, thus facilitating an impressive mechanical flexibility, which allowed molding the crystals into alphabetical characters to spell out “o r g a n i c c r y s t a l”. The study, which reports the preparation of a series of exotic plastic crystals by design for the first time, demonstrates the potential of soft ...

231 citations

Journal ArticleDOI
TL;DR: The intermolecular interactions and structural features in crystals of seven halogenated N-benzylideneanilines (Schiff bases), all of which exhibit remarkable flexibility, were examined to identify the common packing features that are the raison d'être for the observed elasticity.
Abstract: The intermolecular interactions and structural features in crystals of seven halogenated N-benzylideneanilines (Schiff bases), all of which exhibit remarkable flexibility, were examined to identify the common packing features that are the raison d’etre for the observed elasticity. The following two features, in part related, were identified as essential to obtain elastic organic crystals: 1) A multitude of weak and dispersive interactions, including halogen bonds, which may act as structural buffers for deformation through easy rupture and reformation during bending; and 2) corrugated packing patterns that would get interlocked and, in the process, prevent long-range sliding of molecular planes.

183 citations