Organic Chiral Charge Transfer Magnets | ACS Nano

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Organic Chiral Charge Transfer Magnets Zhongxuan Wang, Mingsheng Gao, Mengmeng Wei, Shenqiang Ren, Xiao-Tao Hao, and Wei Qin ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.9b00988 • Publication Date (Web): 14 Mar 2019 Downloaded from http://pubs.acs.org on March 15, 2019

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Organic Chiral Charge Transfer Magnets

Zhongxuan Wang,† Mingsheng Gao,† Mengmeng Wei, † Shenqiang Ren‡, Xiao-Tao Hao, † Wei Qin *,†

†School

of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan,

250100, China ‡

Department of Mechanical and Aerospace Engineering, Research and Education in Energy,

Environment & Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, NY, 14260, United States

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ABSTRACT In this work, through designing organic helix donor-acceptor complexes, one type of room temperature chiral magnet was reported. Within these chiral charge transfer magnets, circularly polarized light could induce a larger saturation magnetization comparing to linearly polarized light illumination with identical intensity. Moreover, the transmission light polarization from chiral magnets could be tuned via applying the magnetic field. Overall, room temperature organic chiral magnets with opto-magnetic effects will enhance the function of organic magneto-chiral materials.

KEYWORDS: chirality; organic magnets; organic opto-magnetic effects; charge transfer complexes; self-assembly

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Self-assembled organic nanostructures have shown the control of their geometric shapes and structural stability. Chiral nanostructure, one of the most important structural characteristics found in nature, has been attracting great interest owing to their relationship to biological structures, specific photophysical properties, chiral medicine and detecting disease.1-3 Through introducing chiral groups in the organic structure,4-7 long-range supramolecular ordering of chirality can be obtained,8-11 and electron vortex beams in organic spiral structure could generate pronounced orbital angular momentum.12-14 In these organic chiral materials, spin selectivity could be induced with the effect of helix structure dependent orbital angular momentum,15,16 which provides a foundation for using chiral materials in spintronics application,17-23 such as magnetic memory without permanent magnet. Generally, with the helix structure of chiral materials, polarized light and electric field possess tunability on orbital angular momentum and spin momentum to result in opto-magnetic effects. Magnetic circular dichroism, originated from the interaction between light and spin of electron, is one of the optomagnetic effects that can be observed in organic chiral materials.24,25 Recently, many nonferromagnetic organic chiral compounds have been fabricated,20,24-27 but, opto-magnetic coupling effects are too weak. To enhance this coupling effect, Train et al. initially let chirality shake hand with ferromagnetism and successfully fabricated Cr ions doped organic chiral magnet N(CH3)(nC3H7)2(sC4H9)MnCr(ox)3,28 where ferromagnetic properties via spin dependent interactions are incorporated within chiral structure to display opto-magnetic phenomena with an enhancement of a factor of 17. Organic ferromagnet with chirality promotes the potential application of opto-magnetic coupling effects. However, Curie temperature (TC) is only 7 K. Thus, if we expect organic chiral materials enter ferromagnetic phase easily, Curie temperature of chiral ferromagnets should increase via specific structure design or other methods. Structure design of organic materials not only realize chiral structures, but also build up different dimensional organic networks to realize room temperature spontaneously ferroelectric 3


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phase,29-32 low temperature33-38 and room temperature ferromagnetic phase,39 for example, ferromagnetic TDAE:C6040 (TC =2 K)

and k-ET2Cu[N(CN)2]Cl41 (TC=26 K). Thus, it is

possible to realize room temperature ferromagnetism with chirality through designing specific structures. Inspired by the progress of chirality research and self-assembly induced organic magnetism, we fabricate room temperature non-ferric organic chiral complexes through selfassembly, where long distance spin ordering and vortex electron beam generated orbital angular momentum show great promise to guide the development of organic magneto-optics. Herein, we report that organic chiral charge transfer magnets display both helix structure and ferromagnetism at room temperature without transition metals. Through tuning poor solvent and chiral solvent doping ratios, poly(3-hexylthiophene) nanowires (nw-P3HTs) with chirality are fabricated, and chiral structure is confirmed via both TEM (transmission electron microscope) and CD (circular dichroism) spectrometer. Under circularly polarized light illumination, chiral nw-P3HT:C60 charge transfer complex displays a larger magnetization than that under linearly polarized light illumination with identical intensity. Furthermore, polarization of transmission light from chiral nanostructure is effectively tuned by external magnetic field, which demonstrates opto-magnetic effects in organic chiral magnets at room temperature.

RESULTS AND DISCUSSION For a traditional achiral material, AL should be equal to AR, where AL (AR) is absorption coefficient of left-hand (right-hand) circular polarization. But, in chiral materials, AL is nor equal to AR, and CD signal (ellipticity θ) is proportional to the difference between AL and AR (θ=α(AL -AR), α is a coefficient). As shown in Figures 1a-c, fabricated chiral nw-P3HT is characterized through TEM and circular dichroism, respectively (details of fabrication are presented in experimental section and Figures S1-S3). Pronounced CD signal provides solid evidence that chiral structure of nw-P3HT is successfully fabricated. Diagram of chiral nw4


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P3HT is shown in Figure 1a. For comparisons, achiral nw-P3HT is also fabricated, and no CD signal is observed (Figure 1c). In chiral nw-P3HT:C60 charge transfer complexes, 0.0026 emu/g Ms (remnant magnetization) with coercivity of 130 Oe is obtained at room temperature without any transition metal doping (Figures 1d-1e). Based on temperature dependent magnetization study, it is note that Curie temperatures of chiral nw-P3HT:C60 is 352 K (inset of Figure 1d), which provides further evidence to confirm that chiral nw-P3HT:C60 composites are room-temperature ferromagnets (details are presented in Figure S4). In the ferromagnetic chiral nw-P3HT:C60, the origin of ferromagnetism shouldn’t be resulted from chiral induced spin selectivity.17-23 or transition metal pollution (Figure S5). Chiral induced spin selectivity could generate spin polarization at one side of chiral molecules to present paramagnetic effect, but ferromagnetism cannot be induced in the pure non-ferromagnetic chiral molecules. Just like pure chiral nwP3HT, no ferromagnetic effect is observed (Figure S6). In addition, amorphous P3HT:C60 charge transfer complexes cannot present ferromagnetism (it is not shown here). Moreover, circularly and linearly polarized light with identical intensity display different tunability on magnetization (Figure 1e). Comparing to linearly polarized light, circularly polarized photons process angular momentum, indicating that circularly polarized light could provide multiapproach tunability on the orbital or spin momentum to display opto-magnetic effects in organic chiral magnets. But, in achiral nw-P3HT:C60 charge transfer complexes, magnetization remain unchanged even changing polarization of incident light (Figure S7). In the following studies, we will provide further understandings on the ferromagnetism and opto-magnetic coupling of chiral nw-P3HT charge transfer magnets. Theoretical simulation of nw-P3HT:C60 change transfer complexes could present the origin of ferromagnetism. As shown in Figures 2a-b, LUMO and HOMO of nw-P3HT:C60 change transfer complexes mainly distribute in C60 and nw-P3HT respectively, where electrons can readily transfer from nw-P3HT to C60 to result in an open-shell structure. Based on 5


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theoretical simulation, it is observed that charge transferred nw-P3HT:C60 complexes display splitting of density of states (DOS) (Figure 2d and Figure S8) when pentagon of thiophene faces to pentagon of C60, where spin polarization is generated in C60 (Figure 2e). At ground states, degenerate DOSs can be observed (Figure 2c). If pentagon of thiophene faces to hexagon of C60, energy levels become degenerate (Figure S9), in which spin polarization density disappears (Figure 2f). Moreover, it should be noted that pentagon of thiophene facing to hexagon of C60 is a higher energy state, which is 2.67 eV larger than the configuration with pentagon of thiophene facing to pentagon of C60. Thus, lower energy state of nw-P3HT:C60 complexes with pentagon of thiophene facing to pentagon of C60 play a decisive role for the generation of room temperature magnetization. As shown in Figure 3a, achiral nw-P3HT and chiral P3HT normalized absorption are presented. The intra-chain –* transition could generate one peak at 602 nm,42 where the intensity of chiral nw-P3HT absorption is obviously larger than that in achiral nw-P3HT, indicating that intra-chain interaction is enhanced.43 In addition, larger PL(0-1)/PL(0-0) values44 of chiral nw-P3HT implies better crystallinity comparing to achiral nw-P3HT (the inset of Figure 3a and S10). Furthermore, peak signal-to-noise ratio is larger for chiral nw-P3HT comparing to achiral nw-P3HT. Full width half maximum (FWHM) of XRD of chiral nw-P3HT is 0.6o (inset of Figure 3c), which is smaller than that of achiral nw-P3HT, 0.8o (inset of Figure 3b). In addition, differential scanning calorimetry (DSC) is also as effective method to characterize the crystallinity of polymer.45 As shown in Figures 3c and 3d, melting and crystallization peaks can be observed for both achiral (210 oC) and chiral nw-P3HT (223 oC). It means achiral and chiral nw-P3HT are the crystallized structure at room temperature. Melting enthalpy (∆Hm) of achiral nw-P3HT (1.45 J/g) is smaller than that of chiral nw-P3HT (2.11 J/g) (peaks of red lines in Figures 3d and 3e). Thus, crystallinity ∆Hm/H0 is larger for chiral nwP3HT (5.7%), indicating that chiral nw-P3HT processes better crystallinity comparing to achiral nw-P3HT (4%), where H0 is the melting enthalpy of 100% crystallinity P3HT crystal 6


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(H0=37 J/g for P3HT),46 which is in accord with the results from UV-vis. The average lifetime chiral nw-P3HT is 700 ps, which is longer than that of achiral nw-P3HT, 450 ps (Figure 3f). Based on above theoretical simulation and experimental results, at least three factors should be noted: ordered structure; charge transfer states; specific arrangement of inter-molecules. In chiral nw-P3HT based complexes, excitons with longer lifetime could more easily diffuse to donor/acceptor interfaces to generate substantial charge transfer states, which more seriously break closed-shell to open-shell structure. Thus, magnetization of chiral nw-P3HT based charge transfer complexes (0.1 emu/g) is larger than that of achiral nw-P3HT charge transfer complexes (0.06 emu/g) under identical condition, as shown in Figure 1d. Organic chiral structures are formed via noncovalent binding in which the interaction is relatively weak. Therefore, thermostability of the chiral charge transfer magnets is one of the key factors to determine their potential applications. As seen in Figure 4, the CD values of chiral nw-P3HT become weaken with increasing annealed temperature, and it will disappear around 400 K. However, generally in nw-P3HT:C60 charge transfer complexes, CD keep a good performance (Figure 4b) even the temperature increase to 440 K, and involving C60 cannot change nw-P3HT crystal structure (Figure S13). Importantly, above 440 K threshold temperature of chiral nw-P3HT:C60 complexes provide a solid footstone for the development and application of organic chiral magnets. More charge transfer could be excited to further enhance open-shell structure to increase magnetization and ESR (electron spin resonance) signal (inset of Figure 5a) with increasing light intensity. However, switching incident light from circularly and linearly polarized light cannot change ESR (Figure 5a), indicating that circularly polarized light generates same density of charge transfer with linearly polarized light. In charge transfer complexes, the lifetime is usually smaller than that in pure single phase. The lifetime of pure chiral nw-P3HT film is 700 ps, when chiral nw-P3HT transfer electrons to electron acceptor C60 in chiral nw-P3HT:C60 complexes, the lifetime decreases to 580 ps (Figure 5b). It should be noted that lifetime of chiral 7


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nw-P3HT:C60 films is independent on polarization change of incident light. Thus, it is predicated that circularly polarized light induced magnetization enhancement (Figure 1e) is not resulted from the change of charge transfer density. For the polarized light dependent magnetization of ferromagnetic chiral nw-P3HT:C60, both right-hand and left-hand circular polarization enhance magnetization comparing to linear polarization with identical intensity (Figure 1e). Theoretically, it is reported that orbital angular momentum dependent magnetization can be generated by helix electric field component of circular polarization to enhance overall magnetization.47 It is expected that this theoretical result can be also introduced into organic chiral charge transfer ferromagnetic complexes for studying circular polarization dependent magnetization. For the chiral nw-P3HT:C60, as shown in Figure 5c, electron beams propagate follows spiral-type, in which they carry orbital angular momentum.12-14 It means, even no heavy metals doping in organic chiral materials, spiral-type structure could effectively generate orbital angular momentum, which can be further tune by circularly polarized light. Because both left-hand and right-hand helix structure can be observed in one thin film, right-hand and left-hand circular polarization will enhance right-hand and lefthand helix structure dependent orbital angular momentum to increase magnetization, respectively. For linearly polarized light, electric field component is not helix type, which is difficult to tune helix structure dependent orbital magnetic moment in chiral nw-P3HT:C60. Thus, it is observed that both right-hand and left-hand circular polarization could increase magnetization of ferromagnetic chiral nw-P3HT:C60 comparing to linearly polarized light with identical intensity (Figure 1e). Because CD signal of the chiral nw-P3HT thin film is negative (Figure 1c), the density of right-hand structure is larger than that of left-hand structure in one thin film, in which right-hand circularly polarized light shows larger enhancement on magnetization of nw-P3HT:C60 comparing to left-hand circularly polarized light (Figure 1e). On the contrary, in achiral nw-P3HT:C60 complexes, due to extremely small orbital angular momentum, magnetization keeps the same even changing light from circular to linear 8


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polarization (Figure S7). Furthermore, external electric field is also applied to further break symmetry to tune spiral structure induced orbital angular momentum in chiral nw-P3HT:C60 complexes. Magnetization displays a pronounced enhancement once increasing electric field from 1×104 V/cm to 2×104 V/cm (Figure 5d). Laser with extinction ratio of 330:1 is used to study opto-magnetic effects in chiral charge transfer magnets. It is noted that smaller extinction ratio is observed when the laser beam goes through chiral nw-P3HT:C60 (Figure 6b). Magnetic field is applied on charge-transfer chiral nw-P3HT:C60 charge transfer complexes to change transmission light extinction ratio. During the measurements, magnetic field is perpendicular to laser beam (Figure 6a). Increasing the value of applied magnetic field could further decrease transmission light extinction ratio, which presents a kind of organic opto-magnetic effect at room temperature.

CONCLUSIONS In summary, a type of room temperature organic chiral charge transfer magnet was successfully designed and fabricated without transition metal doping. The chiral structure is confirmed through both electron microscopy and CD spectrometer. Within these chiral charge transfer magnets, circularly polarized light shows a better tunability on both saturation magnetization and magnetoelectric coupling effect, comparing to the linearly polarized light. Furthermore, chiral charge transfer magnets possess excellent thermostability. Polarization of transmission light from chiral nanostructure is effectively tuned by external magnetic field. Overall, room temperature organic chiral magnets demonstrate opto-magnetic effects which can be used in low energy consumption multiferroic magnetic recording and biological detecting.

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METHODS Chiral P3HT nanowire preparation. In the preparation of organic chiral nanowire structure, typical solvent is composed of three different ones: poor solvent for P3HT, chiral solvent ((R)-(+)-limonene), and good solvent for P3HT. They play the roles of crystallization, dissolving the P3HT, and the chiral source, respectively. First, 30 mg/mL P3HT solution is made at room temperature (solvent is 1,2-dichlorobenzene (1,2-DCB)), then ACN (acetonitrile) with 10:1 volume ratio (1,2-DCB:ACN) is added to facilitate P3HT nanowires (nw-P3HT). At last, (R)-(+)-limonene is added into the mixed solution with 1:2 volume ratio (1,2-DCB:(R)(+)-limonene) to form a 10 mg/mL nw-P3HT solution, where one-dimensional twisted chiral nw-P3HT structure is formed. Chiral nw-P3HT thin films is prepared by coating prepared nwP3HT solution on the quartz glass. All of the thin films are dried in a vacuum with the pressure of 1×10-3 pa for half an hour, and then thin films were annealed on the hot plate at 100 oC 10 minutes to remove chiral solvent (R)-(+)-limonene. After that, these films are used to measure the optical properties, including CD, absorption, photoluminescence, XRD, EPR, fluorescence lifetime and magneto-optical properties. Measurements. TEM (Tecnai G2 F20 S-TWIN) is used to provide crystal morphology. X-Ray diffraction (Bruker AXS, D8 ADVANCE) is used to analysis crystal structure. The fluorescence lifetime is measured through an Edinburgh instruments FLS980 spectrometer with 500 nm excitation wavelength. Steady-state PL data are obtained from PG3000 (Pro., Idea Optics Co. Ltd). JASCO J-810 spectrophotometer is used to characterized circular dichroism properties. Magnetization dependent measurements are measured via superconducting quantum interference device (SQUID). Electric field and polarized light dependent MS are characterized though vibrating sample magnetometer (VSM). Calculation Details. The Quantum Espresso (QE) is used to carry out theoretical simulations. The cutoff energy of a plane-wave is 500 eV. Gradient approximation (GGA) is

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used to treat the exchange-correlation. The k points for the calculations of spin polarized P3HT nanowire based charge transfers through Monkhorts-Pack k-mesh with 2×2×2.

ASSOCIATED CONTENT The authors declare no competing financial interest. Supporting information CD of nw-P3HT films, temperature dependent magnetization of chiral and achiral nwP3HT:C60 complexes, analysis of transition metals concentration in chiral nw-P3HT:C60 complexes, magnetic measurement of pure chiral nw-P3HT, theoretical simulation of nwP3HT:C60 complexes, M-H loops of achiral nw-P3HT:C60 complexes, temperature dependent PL of chiral nw-P3HT, and ESR, XRD, DSC of chiral nw-P3HT:C60 complexes.

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]

ACKNOWLEDGEMENTS This work is supported by the NSFC (Grant No. 11774203, 11574181), Taishan Scholar of Shandong Province and the Fundamental Funds of Shandong University (2018JC021). Work at the University at Buffalo (S.R.) is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DESC0018631.

REFERNECES (1) Li, S.; Xu, L.; Ma, W.; Wu, X.; Sun, M.; Kuang, H.; Wang, L.; Kotov, N. A.; Xu, C., DualMode Ultrasensitive Quantification of MicroRNA in Living Cells by Chiroplasmonic Nanopyramids Self-Assembled from Gold and Upconversion Nanoparticles. J. Am. Chem. 11


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Soc. 2016, 138, 306-312. (2) Yang, M.; Kotov, N. A., Nanoscale Helices from Inorganic Materials. J. Mater. Chem. 2011, 21, 6775. (3) Cornelissen, J.; Rowan, A.; Nolte, R.; Sommerdijk, N., Chiral Architectures from Macromolecular Building Blocks. Chem. Rev. 2001, 101, 4039-4070. (4) Wang, R.; Li, X.; Bai, J.; Zhang, J.; Liu, A.; Wan, X., Chiroptical and Thermotropic Properties of Helical Styrenic Polymers: Effect of Achiral Group. Macromolecules 2014, 47, 1553-1562. (5) Kawagoe, Y.; Fujiki, M.; Nakano, Y., Limonene Magic: Noncovalent Molecular Chirality Transfer Leading to Ambidextrous Circularly Polarised Luminescent π-Conjugated Polymers. New J. Chem. 2010, 34, 637-647. (6) Mathew. G.; Weiss, R., Molecular Organogels. Soft Matter Comprised of Low-MolecularMass Organic Gelators and Organic Liquids. Acc. Chem. Res. 2006, 39, 489-497. (7) Yang, Y.; Costa, R.; Fuchter, M.; Campbell, A., Circularly Polarized Light Detection by a Chiral Organic Semiconductor Transistor. Nat. Photonics 2013, 7, 634-638. (8) Mugarza, A.; Lorente, N.; Ordejon, P.; Krull, C.; Stepanow, S.; Bocquet, M. L.; Fraxedas, J.; Ceballos, G.; Gambardella, P., Orbital Specific Chirality and Homochiral Self-Assembly of Achiral Molecules Induced by Charge Transfer and Spontaneous Symmetry Breaking. Phys. Rev. Lett. 2010, 105, 115702. (9) Liu, M.; Zhang, L.; Wang, T., Supramolecular Chirality in Self-Assembled Systems. Chem. Rev. 2015, 115, 7304-7397. (10)Zhang, L.; Qin, L.; Wang, X.; Cao, H.; Liu, M., Supramolecular Chirality in Self ‐ Assembled Soft Materials: Regulation of Chiral Nanostructures and Chiral Functions. Adv. Mater. 2014, 26, 6959-6964. (11)Yashima, E.; Ousaka, N.; Taura, D.; Shimomura, K.; Ikai, T.; Maeda, K., Supramolecular Helical Systems: Helical Assemblies of Small Molecules, Foldamers, and Polymers with Chiral Amplification and Their Functions. Chem. Rev. 2016, 116, 13752-13990. (12)Harris, J.; Grillo, V.; Mafakheri, E.; Gazzadi, G.; Frabboni, S.; Boyd, R. W.; Karimi, E., Structured Quantum Waves. Nat. Phys. 2015, 11, 629-634. (13)Saitoh, K.; Hasegawa, Y.; Hirakawa, K.; Tanaka, N.; Uchida, M., Measuring the Orbital Angular Momentum of Electron Vortex Beams Using a Forked Grating. Phys. Rev. Lett. 2013, 111, 074801. (14)Uchida, M.; Tonomura, A., Generation of Electron Beams Carrying Orbital Angular Momentum. Nature 2010, 464, 737-739. (15)Gutierrez, R.; Diaz, E.; Naaman, R.; Cuniberti, G., Spin Selective Transport Through Helical Molecular Systems. Phys. Rev. B 2012, 85, 081404. (16)Matityahu, S.; Utsumi, Y.; Aharony, A.; Entin-Wohlman, O.; Balseiro, C. A., SpinDependent Transport Through a Chiral Molecule in the Presence of Spin-Orbit Interaction and Nonunitary Effects. Phys. Rev. B 2016, 93, 075407. (17)Ray, S.; Daube, S.; Leitus, G.; Vager, Z.; Naaman, R., Chirality-Induced Spin-Selective Properties of Self-Assembled Monolayers of DNA on Gold. Phys. Rev. Lett. 2006, 96 , 036101. (18)Naaman, R.; Waldeck, D. H., Chiral-Induced Spin Selectivity Effect. J. Phys. Chem. Lett. 2012, 3, 2178–2187. (19)Naaman, R.; Waldeck, D., Spintronics and Chirality: Spin Selectivity in Electron Transport Through Chiral Molecules. Annu. Rev. Phys. Chem. 2015, 66, 263-281. (20)Ben, O.; Morali, N.; Yochelis, S.; Baczewski, L. T.; Paltiel, Y., Local Light-Induced Magnetization Using Nanodots and Chiral Molecules. Nano Lett. 2014, 14, 6042-6049. (21)Xie, Z.; Markus, T.; Cohen, S..; Vager, Z.; Gutierrez, R.; Naaman, R., Spin Specific Electron Conduction Through DNA Oligomers. Nano Lett. 2011, 11, 4652-4655. (22)Mondal, P.; Kantor, N.; Mathew, S.; Tassinari, F.; Fontanesi, C.; Naaman, R., Chiral 12


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Conductive Polymers as Spin Filters. Adv. Mater. 2015, 27, 1924-1927. (23)Kiran, V.; Mathew, S.; Cohen, S.; Hernández, I.; Lacour, J.; Naaman, R., Helicenes—a New Class of Organic Spin Filter. Adv. Mater. 2016, 28, 1957-1962. (24)Kitagawa, Y.; Segawa, H.; Ishii, K., Magneto‐Chiral Dichroism of Organic Compounds. Angew. Chem. Int. Ed. 2011, 50, 9133-9136. (25)Rikken, G; Raupach, E., Observation of Magneto-Chiral Dichroism. Nature 1997, 390, 493-494. (26)Cao, Hai.; Zhu, X.; Liu, M., Self-Assembly of Racemic Alanine Derivatives. Angew. Chem. Int. Ed. 2013, 52, 4122-4126. (27)Hattori, S.; Yamamoto, Y.; Miyatake, T.; Ishii, K., Magneto-Chiral Dichroism Measurements Using a Pulsed Electromagnet. Chem. Phys. Lett. 2017, 674, 38-41. (28)Train, C.; Gheorghe, R.; Krstic, V.; Chamoreau, L.-M.; Ovanesyan, N. S.; Rikken, G. L. J. A.; Gruselle, M.; Verdaguer, M., Strong Magneto-Chiral Dichroism in Enantiopure Chiral Ferromagnets. Nat. Mater. 2008, 7, 729-734. (29)Fu, D. W.; Cai, H. L.; Liu, Y.; Ye, Q.; Zhang, W.; Zhang, Y.; Chen, X. Y.; Giovannetti, G.; Capone, M.; Li, J. Diisopropylammonium Bromide Is a High-Temperature Molecular Ferroelectric Crystal. Science 2013, 339, 425-428. (30)Tayi, A.; Shveyd, A.; Sue, A.; Szarko, J.; Rolczynski, B.; Cao, D.; Kennedy, T. J.; Sarjeant, A. A.; Stern, C.; Paxton, W.; Wu, W.; Dey, S.; Fahrenbach, A.; Guest, J.; Mohseni, H.; Chen, L.; Wang, K.; Stoddart, J.; Stupp, S., Room-Temperature Ferroelectricity in Supramolecular Networks of Charge-Transfer Complexes. Nature 2012, 488, 485-489. (31)Horiuchi, S.; Tokunaga, Y.; Giovannetti, G.; Picozzi, S.; Itoh, H.; Shimano, R.; Kumai, R.; Tokura, Y., Above-Room-Temperature Ferroelectricity in a Single-Component Molecular Crystal. Nature 2010, 463, 789-792. (32)You, Y.; Liao, W.; Zhao, D.; Ye, H.; Zhang, Y.; Zhou, Q.; Niu, X.; Wang, J.; Li, P.; Fu, D.; Wang, Z.; Gao, S.; Yang, K.; Liu, J.; Li, J.; Yan, Y.; Xiong, R., An Organic-Inorganic Perovskite Ferroelectric with Large Piezoelectric Response. Science 2017, 357, 306-309. (33)Deligiannakis, Y.; Fardis, M.; Milia, F.; Christides, C.; Barchuk, V., Direct Observation of Electron Spin Density on TDAE Cations in TDAE-C60. Phys. Rev. Lett. 1999, 83, 1435-1438. (34)Mihailovic, D.; Venturini, P., Orientational of Buckyballs in TDAE-C60. Science 1995, 268, 400-402. (35)Schilder, A.; Rystau, I.; Gotschy, B., Microwave Conductivity of the Soft Ferromagnet (TDAE)- C60. Phys. Rev. Lett. 1994, 73, 1299-1302. (36)Stephens, P. W.; Lauher, J. W.; Wiley, J. B.; Hirsch, A.; Li, Q.; Thompson, J. D.; Wudl, F., Lattice Structure of the Fullerene Ferromagnet TDAE-C60. Nature 1992, 355, 331-332. (37)Rajca, A.; Wongsriratanakul, J.; Rajca, S., Magnetic Ordering in an Organic Polymer. Science 2001, 294, 1503-1505. (38)Alberola, A.; Less, R. J.; Rawson, J. M.; Oliete, P.; Paulsen, C.; Farley, R. D.; Murphy, D. M., A Thiazyl-Based Organic Ferromagnet. Angew. Chem. Int. Ed. 2003, 42, 4782-4785. (39)Manriquez, J.; Yee, G.; Mclean, R.; Epstein, A.; Miller, J., A Room-Temperature Molecular/Organic-Based Magnet. Science 1991, 252, 1415-1417. (40)Narymbetov, B.; Omerzu, A.; Kabanov, V.; Tokumoto, M.; Kobayashi, H.; Mihailovic, D., Origin of Ferromagnetic Exchange Interactions in a Fullerene-Organic Compound. Nature 2000, 407, 883-885. (41)Lunkenheimer, P.; Müller, J.; Krohns, S.; Schrettle, F.; Loidl, A.; Hartmann, B.; Rommel, R.; Hotta, C.; Schlueter, J. A.; Lang, M., Multiferroicity in an Organic Charge-Transfer Salt that Is Suggestive of Electric-Dipole-Driven Magnetism. Nat. Mater. 2012, 11, 755758. (42)Moule, A.; Meerholz, K., Controlling Morphology in Polymer–Fullerene Mixtures. Adv. Mater. 2008, 20, 240-245. (43)Zhou, X.; Yang, X., Improved Dispersibility of Graphene Oxide in O-dichlorobenzene by 13


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Adding a Poly(3-alkylthiophene). Carbon 2012, 50, 4566-4572. (44)Brown, P.; Thomas, D.; Kohler, A.; Wilson, J.; Kim, J.; Ramsdale, C.; Sirringhaus, H.; Friend, R., Effect of Interchain Interactions on the Absorption and Emission of Poly(3hexylthiophene). Phys. Rev. B 2003, 67, 064203. (45)Van, M.; Van, L.; Koeckelberghs, G., Expression of Chirality in Tailor-Made Conjugated Polymers. Macromolecules 2018, 51, 6602-6608. (46)Pascui, O.; Lohwasser, R.; Sommer, M.; Thelakkat, M.; Thurn-Albrecht, T.; Saalwächter, K., High Crystallinity and Nature of Crystal−Crystal Phase Transformations in Regioregular Poly(3-hexylthiophene). Macromolecules 2010, 43, 9401-9410. (47)Berritta, M.; Mondal, R.; Carva, K.; Oppeneer, P., Ab Initio Theory of Coherent LaserInduced Magnetization in Metals. Phys. Rev. Lett. 2016, 117, 137203.

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Figure 1. (a) Schematic diagram (a) and TEM (b) of chiral nw-P3HT structure. (c) CD spectra of chiral and achiral nw-P3HT structure. (d) M-H loops of chiral nw-P3HT:C60 (red line) charge transfer complexes and achiral nw-P3HT:C60 charge transfer complexes (black line). Inset is temperature dependent magnetization. (e) Magnetization characterization of chiral nwP3HT:C60. The inset shown the coercivities of chiral nw-P3HT:C60 under different polarized light excitation. Circular-Right (Circular-Left) means right-hand (left-hand) circular polarization.

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LUMO

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HOMO

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Figure 2. (a) LUMO of nw-P3HT:C60. (b) HOMO of nw-P3HT:C60. DOS at ground states (c) and excited states (d) in nw-P3HT:C60 change transfer complexes. (e) Charge transfer states induced spin polarization distribution with pentagon of thiophene facing to pentagon of C60. (f) No spin polarization distribution in nw-P3HT:C60 change transfer complexes with pentagon of thiophene facing to hexagon of C60.

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Figure 3. (a) Absorption and photoluminescence of chiral and achiral nw-P3HT films. (b) XRD (X-ray diffraction) of achiral nw-P3HT, FWHM of achiral nw-P3HT are shown in the inset. (c) XRD (X-ray diffraction) of chiral nw-P3HT. The inset shows FWHM of chiral nw-P3HT. (d) DSC of achiral nw-P3HT. (e) DSC of chiral nw-P3HT. (f) Fluorescence lifetime ts of chiral and achiral nw-P3HT films. ts is 450 ps for achiral nw-P3HT, while it is 700 ps for chiral nw-P3HT.

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(a) 3

(b) CD (mdeg)

0 CD (mdeg)

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500 600 Wavelength (nm)

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Figure 4. (a)Temperature dependent CD signals of chiral nw-P3HT films. (b) Temperature dependent CD signals of chiral nw-P3HT:C60 charge transfer complexes films.

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Normalized Intensity (a.u.)

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Figure 5. (a) Electron spin resonance of chiral nw-P3HT:C60 films. 532nm laser is used as incident light (100 mW/cm2). Light intensity dependent electron spin resonance is shown in the inset. (b) Fluorescence lifetime ts of chiral nw-P3HT:C60 films under linearly and circularly polarized light illumination. Detecting wavelength is 650 nm. (c) Diagram of vortex electron beam transport in helix structure. (d) External electric field and polarized light dependent magnetization. ON (OFF) indicates electric field is tuned on (off).

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Figure 6. (a) Diagram of magneto-optical measurements in chiral nw-P3HT:C60 films, where LP is linear polarizer, QWP is quarter wave plate. (b) Extinction ratio dependence of transmission light from chiral nw-P3HT:C60 films on magnetic field. The inset shows Θ dependent transmission light intensity from chiral nw-P3HT:C60 films under different magnetic field. Θ is zero when right linear polarizer is in vertical direction. The extinction ratio is ratio between maximum and minimum intensity.

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TOC 40

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Organic Chiral Charge Transfer Magnets | ACS Nano

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