Tuning the mechanical flexibility of organic molecular crystals by polymorphism for flexible optical waveguides
TL;DR: In this article, two new polymorphic forms of CPMBP were obtained from a solution and fully characterised using a combination of experiments and density functional theory simulations, and the results demonstrated that polymorph engineering would be a promising avenue to achieve concurrent modulation of optical and mechanical properties of photoluminescent molecular crystals for next-generation flexible optical device applications.
Abstract: The ability to selectively tune the optical and the mechanical properties of organic molecular crystals offers a promising approach towards developing flexible optical devices. These functional properties are sensitive to crystallographic packing features and are hence expected to vary with polymorphic modification. Using as a model system the photoluminescent material 4-bromo-6-[(6-chloropyridin-2-ylimino)methyl]phenol (CPMBP), we herein demonstrate the simultaneous tuning of mechanical flexibility and photoluminescence properties via polymorphism. Two new polymorphic forms of CPMBP were obtained from a solution and fully characterised using a combination of experiments and density functional theory simulations. These polymorphic forms exhibit remarkably distinct mechanical properties and an order of magnitude difference in photoluminescence quantum yield. The mechanically plastic form has a higher quantum yield than the brittle polymorphic form. However, their photoluminescence emission profile is largely unaffected by the observed polymorphism, thereby demonstrating that the optical properties and bulk mechanical properties can in principle be tuned independently. By distinguishing between active (involving absorption and emission) and passive (involving no absorption) light propagation, the waveguiding properties of the plastic form of CPMBP (form II) were explored using the straight and bent crystals to highlight the potential applications of CPMBP in designing flexible optical devices. Our results demonstrated that polymorph engineering would be a promising avenue to achieve concurrent modulation of the optical and mechanical properties of photoluminescent molecular crystals for next-generation flexible optical device applications.
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TL;DR: In this article, an organic crystal with the ability of elastic bending and plastic twisting upon loading stress and shearing force, respectively, was reported, which enables the crystal to be a model for tensile-responsive study.
Abstract: Organic crystals with mechanical stimulus-response properties are being developed increasingly nowadays. However, the studies involving tensile-responsive crystals are still lacking due to the strict requirement of crystals with good flexibility. In this work, an organic crystal with the ability of elastic bending and plastic twisting upon loading stress and shearing force, respectively, is reported. The deformability in different directions enables the crystal to be a model for tensile-responsive study. Indeed, blue shifts of fluorescence were observed when the tensile forces loaded upon the needle-shaped crystal were stretched to a certain degree. The mathematical correlation between emission wavelength changes and stretching strain was obtained for the first time, which proves that the crystal has a potential application for tension sensors. In addition, a low detection limit and high sensitivity enabled the crystal to have the ability to detect tension variations in precision instruments. Theoretical calculations and X-ray crystal structure analyses revealed the mechanism of emission wavelength shifts caused by molecular movement during the stretching process. The presented crystal successfully overcame the limitations of traditional mechanochromic organic crystals, which have difficulty in responding to tensile forces.
23 citations
TL;DR: In this article, an anthracene derivative, 9-anthraldehyde, which can respond to mechanical force and light was reported, which possesses two-dimensional (2D) elastic bending, plastic twisting and photoinduced bending properties.
Abstract: Stimuli-responsive crystals have aroused tremendous interest due to their potential as smart materials. However, endowing mono-component crystals with multiple stimuli-responsive and multifunction properties is still a great challenge. Here, we report an anthracene derivative, 9-anthraldehyde, which can respond to mechanical force and light. It possesses two-dimensional (2D) elastic bending, plastic twisting and photoinduced bending properties. Unusual elastic bending of the plastic twisted crystal was achieved in one crystal. The crystal obtained in this work is a multi-dimensional elastic crystal, which is different from reported twistable materials. To reveal the mechanisms of the properties of 2D elastic bending, plastic twisting and photoinduced bending, nanoindentation tests, energy framework analysis and Hirshfeld surface analysis were used to study the property–structure relationship at the molecular level. It was found that these properties can be ascribed to the unique intermolecular interactions and types of molecular arrangement.
18 citations
DOI•
16 Nov 2021
TL;DR: In this paper, a single crystal of (E)-1-(4-bromo-phenyl)iminomethyl-2-hydroxyl-naphthalene (BCPIN) is shown to have elastic bending similar to BPIN, but exhibit a remarkable difference in optical properties as a result of the chemical modification to the backbone of the organic molecule.
Abstract: Organic single crystals that combine mechanical flexibility and optical properties are important for developing flexible optical devices, but examples of such crystals remain scarce. Both mechanical flexibility and optical activity depend on the underlying crystal packing and the nature of the intermolecular interactions present in the solid state. Hence, both properties can be expected to be tunable by small chemical modifications to the organic molecule. By incorporating a chlorine atom, a reportedly mechanically flexible crystal of (E)-1-(4-bromo-phenyl)iminomethyl-2-hydroxyl-naphthalene (BPIN) produces (E)-1-(4-bromo-2-chloro-phenyl)iminomethyl-2-hydroxyl-naphthalene (BCPIN). BCPIN crystals show elastic bending similar to BPIN upon mechanical stress, but exhibit a remarkable difference in their optical properties as a result of the chemical modification to the backbone of the organic molecule. This work thus demonstrates that the optical properties and mechanical flexibility of molecular materials can, in principle, be tuned independently.
4 citations
TL;DR: In this paper , the authors presented three fluorescent plastically bendable crystalline materials, namely, 2.5, 6.5 and 4.5 molecules, which act as active and passive waveguides both in straight and extremely bent (U, J, and O-shaped) geometries.
Abstract: Fluorescent plastically bendable crystals are a promising alternative to silicon‐based materials for fabricating photonic integrated circuits, owing to their optical attributes and mechanical compliance. Mechanically bendable plastic organic crystals are rare. Their formation requires anisotropic intermolecular interactions and slip planes in the crystal lattice. This work presents three fluorescent plastically bendable crystalline materials namely, 2‐((E)‐(6‐methylpyridin‐2‐ylimino)methyl)‐4‐chlorophenol (SB1), 2‐((E)‐(6‐methylpyridin‐2‐ylimino)methyl)‐4‐bromophenol (SB2), and 2‐((E)‐(6‐Bromopyridin‐2‐ylimino)methyl)‐4‐bromophenol (SB3) molecules. The crystal plasticity in response to mechanical stress facilitates the fabrication of various monolithic and hybrid (with a tip‐to‐tip coupling) photonic circuits using mechanical micromanipulation with an atomic force microscope cantilever tip. These plastically bendable crystals act as active (self‐guiding of fluorescence) and passive waveguides both in straight and extremely bent (U‐, J‐, and O‐shaped) geometries. These microcircuits use active and passive waveguiding principles and reabsorbance and energy‐transfer mechanisms for their operation, allowing input‐selective and direction‐specific signal transduction.
3 citations
TL;DR: In this paper , an unprecedented giant cyclic supramolecular Br8 synthon with a fused triangular prism-like geometry formed exclusively through hypervalent Br···Br interactions in the crystal structure of α, α,α, α′,α′-tetrabromo-o-xylene with a Br4 tetrahedral synthon was isolated and characterized by single-crystal X-ray diffraction.
Abstract: Architecting unique supramolecular structures requires robust and reproducible supramolecular synthons. Noncovalent halogen bonding offers rich crystal packing possibilities through diverse synthons and thus constitutes a useful structural domain in crystal groups. The variations in halogen synthon patterns with bromine substitution was explored by means of crystal packing analyses of a series of bromine-substituted o-xylenes. We report an unprecedented giant cyclic supramolecular Br8 synthon with a fused triangular prism-like geometry formed exclusively through hypervalent Br···Br interactions in the crystal structure of α,α,α′,α′-tetrabromo-o-xylene. A new polymorph of the compound α,α,α′,α′-tetrabromo-o-xylene with a Br4 tetrahedral synthon was isolated and characterized by single-crystal X-ray diffraction. Additionally, a rectangular Br4 synthon was found to direct the crystal packing in α,α,α′-tribromo-o-xylene. Lines of evidence for the noncovalent intermolecular Br···Br interactions rendering the Br8 and the Br4 synthons were quantitatively obtained by Bader’s quantum theory of atoms in molecules (QTAIM). Noncovalent interaction index isosurfaces exposed the intramolecular interactions, which were not evident from QTAIM. Penda’s interacting quantum atom energy partitioning provided insight into the Br···Br interaction energy in terms of electrostatic and exchange–correlation components. Despite the presence of σ holes as characterized by electrostatic potential analysis, the Br···Br interactions constituting the Br8 and Br4 synthons are stabilized through nonelectrostatic components. The current study intends to reinforce the potential of nonelectrostatic weak halogen···halogen contacts to give rise to a wide variety of synthon patterns and develop solid supramolecular assemblies that find applications in numerous fields of research.
3 citations
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TL;DR: A simple derivation of a simple GGA is presented, in which all parameters (other than those in LSD) are fundamental constants, and only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked.
Abstract: Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. [S0031-9007(96)01479-2] PACS numbers: 71.15.Mb, 71.45.Gm Kohn-Sham density functional theory [1,2] is widely used for self-consistent-field electronic structure calculations of the ground-state properties of atoms, molecules, and solids. In this theory, only the exchange-correlation energy EXC › EX 1 EC as a functional of the electron spin densities n"srd and n#srd must be approximated. The most popular functionals have a form appropriate for slowly varying densities: the local spin density (LSD) approximation Z d 3 rn e unif
146,533 citations
TL;DR: This paper could serve as a general literature citation when one or more of the open-source SH ELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.
Abstract: An account is given of the development of the SHELX system of computer programs from SHELX-76 to the present day. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. SHELXL is the most widely used program for small-molecule refinement and SHELXS and SHELXD are often employed for structure solution despite the availability of objectively superior programs. SHELXL also finds a niche for the refinement of macromolecules against high-resolution or twinned data; SHELXPRO acts as an interface for macromolecular applications. SHELXC, SHELXD and SHELXE are proving useful for the experimental phasing of macromolecules, especially because they are fast and robust and so are often employed in pipelines for high-throughput phasing. This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.
81,116 citations
IBM1
TL;DR: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way and can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function.
Abstract: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way. The method allows high-quality first-principles molecular-dynamics calculations to be performed using the original fictitious Lagrangian approach of Car and Parrinello. Like the LAPW method it can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function. The augmentation procedure is generalized in that partial-wave expansions are not determined by the value and the derivative of the envelope function at some muffin-tin radius, but rather by the overlap with localized projector functions. The pseudopotential approach based on generalized separable pseudopotentials can be regained by a simple approximation.
61,450 citations
TL;DR: In this article, a method for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector is given, where the integration can be over the entire zone or over specified portions thereof.
Abstract: A method is given for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector. The integration can be over the entire Brillouin zone or over specified portions thereof. This method also has applications in spectral and density-of-state calculations. The relationships to the Chadi-Cohen and Gilat-Raubenheimer methods are indicated.
51,059 citations
TL;DR: New features added to the refinement program SHELXL since 2008 are described and explained.
Abstract: The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as `a CIF') containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.
28,425 citations