Positive/Negative Phototropism: Controllable Molecular Actuators with Different Bending Behavior

Open AccessCCS ChemistryRESEARCH ARTICLE1 Apr 2021Positive/Negative Phototropism: Controllable Molecular Actuators with Different Bending Behavior Haoran Wang, Jiapeng Liu, Kaiqi Ye, Qiyao Li, Jianyu Zhang, Hao Xing, Peifa Wei, Jingbo Sun, Francesco Ciucci, Jacky W. Y. Lam, Ran Lu and Ben Zhong Tang Wang State Key Laboratory of Supramolecular Structure Materials, College Chemistry, Jilin University, Changchun Department Hong Kong Branch Chinese National Engineering Research Center for Tissue Restoration Reconstruction, Institute Advanced Study, The University Science Technology, Google Scholar More articles by this author , Liu Mechanical Aerospace Engineering, Ye Li Zhang Xing Wei Sun Ciucci Chemical Biomolecular Lam *Corresponding authors: E-mail Address: [email protected] https://doi.org/10.31635/ccschem.020.202000350 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesTrack Citations ShareFacebookTwitterLinked InEmail Herein, a series molecular actuators based on the crystals (E)-2-(4-fluorostyryl)benzo[d]oxazole ( BOAF4), (E)-2-(2,4-difluorostyryl)benzo[d]oxazole BOAF24), (E)-2-(4-fluorostyryl)benzo[d]thiazole BTAF4), (E)-2-(2,4-difluorostyryl)benzo[d]thiazole BTAF24) showed unique bending behavior under UV irradiation. one-dimensional (1D) BOAF4 BTAF4 bent toward light, whereas those BOAF24 BTAF24 away from light. Although chemical structures these compounds are similar, authors found that F···H–C interaction played key role in different packing crystals, which led positive/negative phototropism actuators. Moreover, theoretical calculations were carried out reveal mechanical properties crystals. Taking advantage photomechanical properties, achieved potential application pushing objects, as well enriching removing pollutants. Hence, could be fabricated introducing number F atom, may open novel gate crystal engineering. Download figure PowerPoint Introduction Nature endows organisms tropisms moving or stimulus. For most plants, their stem exhibits positive maximize photosynthetic energy promoting growth.1,2 However, roots some vine shoot tips exhibit negative phototropism, allowing them grow darkness, drill into soil, climb objects.3 combination allows plants correct direction, make better use light energy. Inspired response natural external stimuli, various artificially intelligent materials, such artificial muscles flexible electronics, have been developed.4–10 Among them, responsive materials emerged research hot spot advantages, including easy-to-achieve remote control miniaturization devices.11,12 Especially, conspicuous merits over polymer-based faster time,13 higher Young’s modulus,14 an ordered structure can easily characterized X-ray diffraction (XRD) techniques.6 In addition, offers opportunities rapid transfer between tightly packed molecules, used physical platform actuation nanoscale macroscale.15,16 It has photochemical active organic compounds, azobenzenes, anthracenes, diarylethenes, furylfulgides, capable bending,17–30 curling,31 twisting,31,32 crawling,33–37 leaping5,38 Recently, Naumov et al.39 reported smart cocrystal probenecid 4,4?-azopyridine, reversibly respond multiple stimuli (heat, pressure) twisting, bending, elastic deformation without fracture. Bardeen al.40 controllable movement 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene varying angle incident As far we know, previous efforts regulate motion mainly focused changing conditions controlling habits irradiation direction. Till now, modes through tuning posed significant challenge. our work, introduction chlorine at position benzene styrylbenzoxazoles affect would further topophotochemical reaction.41 Compared chlorine, fluorine possesses smaller atomic radius stronger electronegativity, so conjugated molecules might lead arrangement interesting behavior. With considerations mind, intended study photoinduced motions fluorine-containing [(E)-2-(4-fluorostyryl)benzo[d]oxazole BOAF4) BOAF24)] styrylbenzothiazoles [(E)-2-(4-fluorostyryl)benzo[d]thiazole BTAF4) BTAF24); Scheme 1] effect was BOAF4, BOAF24, BTAF4, curling, fragmentation, swelling, photosalient Interestingly, but oppositely 1 | styrylebenthiazoles. Experimental Methods General information 1H NMR 13C spectra recorded Mercury plus instrument (Varian. Palo Alto, California, USA) 400 101 MHz using deuterated chloroform (CDCl3) deuterium dimethyl sulfoxide (DMSO-d6) solvents. Fourier transform infrared (FT-IR) obtained Nicolet-360 FT-IR (Thermo Scientific, Middlesex County, Massachusetts, spectrometer incorporation samples potassium bromide (KBr) disks. Mass measured AXIMA CFR matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass (compact, Shimadzu, Kyoto, Japan). UV–Vis absorption Mapada UV-1800pc spectrophotometer (Shimadzu, Fluorescence emission taken Cary Eclipse fluorescence (Agilent, Santa Clara, USA). microscopy images Microscope (Olympus Reflected System BX51, Olympus, XRD patterns Empyrean (Malvern Instruments, London, UK), equipped graphite monochromatized Cu-K? radiation (? = 1.5418 Å), employing scanning rate 0.00267°s?1 2? range 2°–40°. single slow evaporation solutions dichloromethane (CH2Cl2)/petroleum ether (v/v 1/4). photodimerization products D-BTAF4 D-BTAF24 gained via irradiating microcrystals 365 nm 30 min, followed recrystallization petroleum ether. CH2Cl2 steam vapor diffusion method. above selected analysis APEX II diffractometer (Bruker, USA), graphite-monochromated Mo-K? 0.71073 Å). solved direct methods refined F2 full-matrix least-squares SHELXTL-97 program (George M. Sheldrick, Thomas R. Schneider, Lower Saxony, Germany). nonhydrogen atoms (S, C, N, F) placed subsequent difference maps anisotropically. H introduced calculated positions fixed geometry respect carrier atoms. Cambridge Crystallographic Data Centre (CCDC) 1814131, 1814889, 1850307, 1850304 contain supplementary crystallographic data BTAF24, D-BTAF4, D-BTAF24, respectively. single-crystal D-BOAF4, D-BOAF24 work.42 Photomechanical behaviors observed microscope, put glass substrate irradiated pocket lamp (365 nm, 3 W) times 298 K. fibers dropping solution tetrahydrofuran (THF; 1.0 × 10?2 mol/L) sodium dodecyl sulfate aqueous (2 mg/mL) stirring. THF dried benzophenone. calcium hydride. other reagents purification. Computational We performed all spin-unpolarized first-principle Vienna ab initio simulation package (VASP, Vienna, Austria)43,44 plane-wave basis set projector-augmented wave (PAW) approach.45 exchange correlation is described Perdew–Burke–Ernzerhof (PBE) functional46 generalized gradient approximation (GGA) scheme. To obtain accurate constant, kinetic cutoff large 700 eV sampled Brillouin zone Gamma-centered k-meshes least 5000 k points per reciprocal atom (pra). first fully relaxed ensure each self-consistent calculation (SCF) than 10?6 eV, maximum force converged below 0.005 eV/Å. tensor then performing two magnitudes displacement (0.01 ?0.01 Å) along Cartesian directions. bulk modulus shear finally stiffness tensor.47 Synthesis syntheses previously.41,48 synthesized according procedure.41 synthetic route characterization shown Supporting Information. Results Discussion First, slice-like rod-like ether/CH2Cl2 3/1) one test tube. case low aspect ratio, swinging swelling Information Figure S1 Video S1). Accompanied effect, became blue-shifted gradually.42 thinner displayed behavior, it bend S2 S2). irregular high comparable Besides exhibiting roll up its tail (Figure S3). detail, induced emergence cracks backlight side crystal, When time prolonged 90 s, raised plane, ca. 135° break. 1. Optical photographs before after vertically 365-nm (the arrow indicates direction). Therefore, thicknesses ratios tend source. Notably, needle-like (E)-2-(2,4-dichlorostyryl)benzo[d]oxazole BOACl24) light,41 opposite BOAF4. irradiation, designed comparison BOAF4.48 formed block, ribbon-like, 3/1). long block swing upon small pieces jumped body. prolonging more cross sections S4). also accumulation state process al.6 proposed. S5, turning off 23 lay still began break s. This proves occurs induction period during accumulates. Furthermore, 1D markedly exhibited compared thicker ones S6 S3a). downside, right elongated marked red circle down around Meanwhile, part yellow gave slight thicker. Also, bouquet-like consisting lots ribbons similar S3b). Except bouquet ribbon-like even jump S7). clearly observe direction selected. S8 2, source being reversed, straightened. Prolonging time, 11 s continued backward Such repeated several times, meaning reversible. 2. arrows indicate deep understanding effects analogs obtained. anticipated, straightened when changed 3). enhanced intensity S4).49–51 rod-like, cyclohexane/CH2Cl2 4/1). Under source, just any bending. upside vertically, straight upward time. S9). “turn on” S6). original exploded body S10). beginning splitting parts perpendicular axis S11). 3. directions). Mechanism [2 + 2] cycloaddition reaction took place driving effects. Particularly, movement, “turned nonemissive emissive. typical aggregation-caused quenching (ACQ) molecules,42 broke conjugation extent, intensified due intramolecular intermolecular through-space conjugation.42 spectral changes suggested occurred microcrystals. depicted S7, 2 double 5.20 ppm, ascribed protons newly cyclobutane. new peaks 6.93, 7.11, 7.60 ppm product (named D-BTAF24) detected. S8). transformation BTAF24. demonstrate collected dimers (?- ?-types), D-BTAF24. ?-types) had Schmidt52 distance “olefin pair” (<4.2 angles ?2 ?3 (close 90°) Chart geometric criteria photodimerization. 3.896 3.681 Å S9a), 77.00°/69.99° 87.97°/83.04°, respectively Table made accessible. Subsequently, D-BOAF4 analyzed. isomers I photocycloaddition S9b). isomer example, bond lengths C–C four-membered ring 1.578 1.579 Å. carbon C=C move 1.1–1.3 cyclobutane impelled benzoxazole ring, like bird spreads wings. result, distances outermost C reached 7.132 7.811 Similar results Figures S9b, S10, Since volume amplified dimerization, strain yielded, leading movements interestingly, seems will yield only ?-type dimer, ?-type ratio amount ?- about 20:1 column chromatography. arranged head-to-head main dynamic product.53 possible reason formation S12. unparalleled 8.513 strains generated satisfied Schmidt’s squeezed thus affording D-BOAF24. On contrary, dimerization concerned prearrangement <4.2 pairs” discuss why while performance. 2003, Ikeda al.54 Yu al.55 monodomain polydomain liquid elastomer (LCE) films light-induced LCE alignment azobenzene mesogens., 2006, they initial photoactive mesogens significantly affected films: homogeneous actinic homotropic source.56 Thus, proposed crucial impact proven phototropic surface irradiation.57 4a, (010) face largest superficial area. Before longitudinally aligned crystal. length decreased 12.268 11.091 average value photodimerization). width increased 3.56 molecules) 7.476 longitudinal (FL) shrink, transverse (FT) crystal’s expansion. extended FL compressed Similarly, (011) decrease 12.286 11.046 D-BOAF24) increase 3.863 6.822 D-BOAF24). Molecules perpendicularly 4b). face, observations 4. Schematic illustration (a) (b) Theoretical investigate within Hirshfeld two-dimensional (2D) fingerprint plots stacking initially S13). there kind H-bond C(3)–H(3)···F(1) 2.74 Å, colored 5a) makes molecule align except C(4)–H(4)···F(1) (2.69 four additional H-bonds C(14)–H(14)···F(1) C(3)–H(3)···F(2) (2.88 (2.87 C(12)–H(12)···F(2) (2.97 BOAF24. Besides, map shows tends form plane 5c). interactions account 23.0% total interactions, twice much (12.2%) believe plays (Figures 5b 5d). 5. surfaces (mapped di) (c) (d) explore density functional theory VASP software. Calculations conducted imposing specific tensor. listed S9, Pugh 2.7280, 2.1115, 2.2372, 1.9556, All values larger 1.75, indi