Article pubs.acs.org/IC
Networked Spin Cages: Tunable Magnetism and Lithium Ion Storage via Modulation of Spin-Electron Interactions Guo-Hong Ning,† Bingbing Tian,†,¶ Li-Min Tan,† Zijing Ding,†,¶ Tun Seng Herng,‡ Jun Ding,‡ and Kian Ping Loh*,† †
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore Department of Materials Science & Engineering, Faculty of Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 117574, Singapore ¶ SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China ‡
S Supporting Information *
ABSTRACT: A networked spin cage comprising infinite CoII6L4 cages arrays (where Co = Co(NCS)2 and L = 1,3,5tri-(4-pyridyl)-verdazal radical) is synthesized and found to exhibit tunable magnetic and electrochemical properties via inclusion of guests. SQUID investigation reveals the coexistence of ferromagnetic and anti-ferromagnetic interactions between the Co(II) ion center and radical ligands. Inclusion of electron-deficient guests (e.g., tetracyanoethylene) dramatically enhances spin concentration and increases antiferromagnetic interactions due to the formation of chargetransfer complex between the host and the guest. In addition, introduction of electron-rich guests (e.g., tetrathiafulvalene) into the networked spin cages doubles the capacity for binding the lithium ions.
■
INTRODUCTION In the past decade, a wide range of metal−organic frameworks (MOFs) with different applications including gas storage, separation,1 catalysis,2 and molecule recognition3 have been developed. However, there are relatively few studies on the electrochemical activities and long-range magnetic ordering in MOFs, which have relevance to applications in energy storage, electrochemical sensors, electrocatalysis, and spintronics.4 Recent advances in organic radical chemistry provide the opportunities to introduce radicals or unpaired electrons into the framework, thus enriching electronic properties such as redox activities, charge transfer, and long-range electronic communication.5 Other than a few reports on the use of triphenylmethyl radicals as building blocks in MOFs,6 radical MOFs with unpaired electron in their frameworks are generally not well-studied, and their host−guest chemistry, particularly spin-electron interactions, remains unexplored. The challenges involved in synthesizing stable radical ligands with open coordination site, as well as constructing radical host with well-defined cavities in MOFs, must be addressed. Host−guest chemistry is a well-established approach for tuning the reactivity, stability,7 photonic,8 and magnetic properties at the molecular level.9 Although chemists have designed a multitude of solution hosts,10 solid-state hosts have received much less attention, especially with regard to the © XXXX American Chemical Society
design of pores with strong binding ability. Recently we have shown that ingenious design of networked cages and capsules based on the blueprint of the isostructural solution host allows us to precisely prepare the solid-state host by networking solution host.11,12 With this strategy, not only the rigid but also dynamic solution host can be reproduced and constructed as networked solid-state host with strong binding pocket.12 Previously, Fujita group reported a molecular spin cage from self-assembly of verdazyl radical and palladium metal ion; new spin−spin host−guest interactions were observed by inclusion of radical guests.13 Herein, we report the facile synthesis of networked spin cages 1 comprising infinite Co6L4 (where L = 1,3,5-tri-(4-pyridyl)-verdazal radical (TPV)) arrays with multiple spin centers around cage framework by networking the solution molecular spin cage (Figure 1). Despite the long distance between neighboring paramagnetic Co(II) ions, the bridged verdazyl radical ligand mediates spin−spin interactions effectively, resulting in a magnetic and redox-active radical solid-state host. The well-defined cavity surrounded by four verdazyl radical-core ligands 2 is able to bind incoming guests, displaying guest-modulated spin concentration, magnetism, and lithium ion storage. On the one hand, accommodation of Received: July 22, 2016
A
DOI: 10.1021/acs.inorgchem.6b01740 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
was replaced three times with a freshly prepared solution of guest by decantation. The crystals were separated and collected by filtration and washed with toluene to give the inclusion complex 1•3 or 1•4. Inclusion Complex 1•3. Anal. Calcd for {[(Co(NCS)2)3(2)4] •(3)5}n: C 51.25, H 2.38, N, 30.77; found: C 51.22, H 2.37, N 30.79%. IR (KBr): 3235 (m), 3097 (m), 2202 (m, CN st), 2067 (s, SCN st), 1639 (m), 1602 (s), 1504 (s), 1414 (m), 1346 (m), 1242 (m), 1206 (s), 1144 (m), 1016 (m), 812 cm−1 (m). Inclusion complex 1•4. Anal. Calcd for {[(Co(NCS)2)3(2)4] •(4)2.5}n: C 46.35, H 3.10, N, 20.65; found: C 46.36, H 3.12, N 20.62%. IR (KBr): 3245 (m), 3027 (m), 2065 (s, SCN st), 1637 (m), 1601 (s), 1503 (s), 1415 (m), 1347 (m), 1217 (s), 1203 (m), 1134 (m), 1012 (m), 821 cm−1 (m).
■
Figure 1. (a) Synthesis of the network spin cages 1. (b) The crystal structure of networked spin cages 1, stick model (cubic, space group Fm3̅m). The guests used for synthesis of inclusion complex (c) electron-deficient guest 3 and (d) electron-rich guest 4 (electrostatic potential surfaces are shown by DFT calculation; red and blue represent positive and negative potentials, respectively. The plot scales have been set to the same color scale).
electron-deficient guests dramatically enhances the spin concentration and increases the anti-ferromagnetic interactions of 1 due to the formation of charge-transfer (CT) complex between the host and the guests. On the other hand, encapsulation of electron-rich guests improves the lithium ion storage performance of host 1. Thus, a unique networked spin cage in which the magnetic and redox properties can be mediated via tuning of spin-electron interactions were successfully synthesized.
■
RESULTS AND DISCUSSION
Networked spin cage 1 was prepared during the slow diffusion of a methanol solution of Co(NCS)2 into a solution of verdazal radical ligand 2. Dark green crystals of 1 formed after ∼one week, and these crystals were isolated by filtration with 64% yield. The structure of 1 was elucidated using single-crystal Xray crystallographic analysis.14 It crystallizes in the cubic space group Fm3̅m and consists of an infinite array of CoII6L4 spin cages with six Co(II) ion vertexes and four TPV panels15 that is isostructural to previous reported molecular spin cage (Figures 1c and S1).13 The cubic crystal system results in the four TPV ligands in 1 sitting on three threefold axes and two minor; therefore, the verdazyl core is unable to be properly modeled, and the refinement is performed by modeling a C3-symmetric triazine ring instead of the verdazyl ring (see Figure S1 for asymmetric unit). Notwithstanding, the crystal structure provides reliable indication for the formation of the networked spin cages 1 with four organic spin centers per cage. The introduction of certain guests into the cavity of 1 is proposed to tune the electronic character of 1 through the spinelectron interactions. Thus, we chose tetracyanoethylene (TCNE, 3), electron-poor guest, and tetrathiafulvalene (4), electron-rich guest, for the synthesis of clathrate complex. Soaking the crystals of 1 into a toluene solution of guest 3 or 4 gives the inclusion complex 1•3 or 1•4. The encapsulation of guests was unambiguously confirmed by the elemental analysis and NMR analysis. The elemental analysis revealed the molecule formulas of inclusion complex 1•3 and 1•4 are {[(Co(NCS)2)3(2)4]·(3)5}n and {[(Co(NCS)2)3(2)4]·(4)2.5}n, respectively. Moreover, the inclusion crystals 1•3 and 1•4 were digested with HCl (aq) and extracted with CHCl3 to give the guest 3 and 4 as solid residual with 21 and 28 wt %, respectively. It agrees well with the elemental analysis results that suggest 22 and 26 wt % of guest 3 and 4 in corresponding inclusion complexes, respectively. Importantly, the IR and solid-state UV−vis spectrum of 1•3 reveals the formation of CT complex between host and guests.15,16 The IR absorbance shows that two sharp peaks at 2258 and 2221 cm−1, assigned to the vibration of the CN triple bond in guest 3, shifts to a lower frequency as a broad peak at 2201 cm−1, which is attributed to the vibration of the CN in the inclusion complex 1•3 (Figure 2). In addition, the solid-state UV−vis spectrum of 1 shows two strong absorption bands at 450 and 695 nm, which are red-shifted to 464 and 696 nm for inclusion complex 1•3 (Figure 2). The radical nature of 1 was confirmed by ESR analysis. Free ligand 2 exhibits nine sharp signals derived from four nitrogen nuclei (Figure S4). In contrast, the ESR spectrum of 1 shows only one broad peak (Figures 3a and S4). The signal broadening might arise from the anisotropic magnetic
EXPERIMENTAL SECTION
Synthesis of Networked Spin Cages (1). A solution of TPV 2 (6.3 mg, 0.02 mmol) in a 4 mL dichlorobenzene and 1 mL MeOH mixture was placed in the bottom of a test tube (inner diameter 1 cm, height 10 cm). MeOH (1 mL) was layered on the top of the reaction mixture as a buffer. After that, a solution of Co(NCS)2 (7.0 mg, 0.04 mmol) in methaol (1 mL) was carefully layered on the top of the resultant solution, and the test tube was allowed to stand at room temperature (RT) for ∼one week. The networked spin cage 1 was produced as dark green cubic crystals on the surface of the test tube and was collected, filtrated, and dried at 120 °C under reduced pressure for one day. (64% yield, 6 mg; averaged value over three batches). IR (KBr): 3421 (m), 3050 (m), 2060 (s, SCN), 1654 (m), 1599 (s), 1502 (s), 1408 (m), 1375 (s), 1218 (m), 1148 (m), 1013 (m), 821 cm − 1 (m). Anal. Calcd for {[Co(NCS) 2 ] 3 (2) 4 (C6H4Cl2)0.5}n: C 49.61, H 3.14, N 25.55; found: C 49.51, H 3.11, N 25.58%. Synthesis of Inclusion Complexes. As-synthesized 1 (∼100 mg) was immersed in a toluene solution of guest molecules (i.e., tetracyanoethylene (3) or tetrathiafulvalene (4); 2 mL) and allowed to stand at room temperature for 5 d, during which the supernatant B
DOI: 10.1021/acs.inorgchem.6b01740 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
delocalization of host 1 owing to the very weak host−guest interaction at high temperature. The large increase of spin concentration in 1•3 motivates us to further evaluate the influences of electron-poor guests on magnetic behaviors of host. The magnetic susceptibility of 1 and 1•3 was measured on a superconducting quantum interference device (SQUID) magnetometer. The profile of molar magnetic susceptibility with temperature (χmT) versus temperature (Figure 3b) reveals the RT χmT value of 1 is 10.67 emu K mol−1. On the one hand, it is higher than the expected spin-only value of 7.13 emu K mol−1 calculated for three Co(II) ions and four TPV radicals with g = 2.0 and local spin SCo = 3/2 and STPV = 1/2, respectively, indicating a magnetic orbital contribution derived from the high-spin Co(II) ions in the sixcoordinated octahedral geometry. On the other hand, with the introduction of guest 3, magnetic susceptibility dramatically reduced to 5.96 emu K mol−1 because the formation of CT complex between TPV ligand and guest 3 decreased the local spin on the TPV ligand (STPV < 1/2). When the temperature was lowered, the χmT value of 1 and 1•3 smoothly declines to a value of 5.48 and 2.58 emu K mol−1, respectively, at 2 K. Such a decrease may be associated with an anti-ferromagnetic exchange coupling between the Co(II) ions and/or to the depopulation of the higher-energy Kramers doublets of the Co(II) centers with a 4T1 term as the ground state. The temperature dependence of the magnetic susceptibilities from 100 to 300 K is fitted with a Curie−Weiss law as shown in the Figure 3b inset. The Weiss constant (θ) values of 1 and 1•3 are −25.1 and −50.3 K, respectively. The corresponding Curie constant is 11.48 and 6.92 emu k mol−1 for 1 and 1•3, respectively. The more negative Weiss value indicates the much stronger anti-ferromagnetic interactions between Co(II) ions and radicals in 1•3 than that of 1. It is worth noting that there is slight enhancement of magnetic susceptibility in host 1 from 6−12 K (Figures 4b and S6) and provides Curie and Weiss constants of C = 7.36 cm3 K mol−1 and θ = 0.39 K, respectively. Such a small increase can be ascribed to a weak ferromagnetic interaction between Co(II) ion and TPV radicals, and the spins arrangement overcomes the thermal depopulation of Co(II) Kramer levels. However, these ferromagnetic interactions between Co(II) ions and radicals are not observed within the guest inclusion complex 1•3. Networked spin cages 1 show a strong magnetization below a critical temperature Tc of 10 K. In particular, the ferromagnetic nature of the transition is confirmed by the field-dependent isothermal magnetization performed at 2 K, which shows an abrupt increase to a saturated value of 4.33 μB at 7 T (Figure S7), which is an intermediate value between ∼10.3 μB (all magentic interactions are ferromagnetic interactions) and ∼2.3 μB (all magentic interactions are anti-ferromagnetic interactions),6c suggesting the coexistence of ferro- and antiferromagnetic interactions within the host 1. In addition, the inclusion complex 1•3 shows a saturation of magnetization Ms, with a value of 2.56 μB. This value is only slightly higher than that of ∼2.3 μB, indicating the magnetic interations of inclusion complex 1•3 are only anti-ferromagetic interations. It is known that π−π stacking of electron-rich or πconjugated molecules can stabilize the charged states.19 Inspired by this, we further studied the effects of the electron-rich guests on lithium ion binding abilities of networked spin cages 1. The CV profiles of 1 show one pair of reversible peaks centered at E1/2 = 2.67 V (vs Li/Li+), which is similar to that of 2 (centered at E1/2 = 2.66 V) at the same
Figure 2. (a) Comparison of IR spectrum of networked spin cages 1 (black); 1•3 (red); and TCNE guest 3 (blue). (b) Diffuse reflectance spectra in BaSO4 powder of 1 (black) and 1•3 (red).
Figure 3. (a) Temperature dependence of ESR spectrum of networked spin cages 1. Comparison of ESR intensity at (b) 123 K and (c) 323 K. (inset) ESR signal of 1 and 1•4 magnified by 30 times (black, 1; blue, 1•3; red, 1•4).
interaction in solid-state as well as the proximity of four spin centers on the ligand within the framework of 1. In addition, the position and peak-to-peak width of signal is independent of temperature, suggesting the magnetic dipole−dipole interactions between the neighboring spins can be discounted within the temperature range from 323 to 123 K.17,18 Furthermore, the intensity of ESR signals of 1 rapidly decreases with temperature increase (Figure 3), which can be explained by the delocalization of free spins within the frameworks at high temperature. The inclusion complexes 1•3 and 1•4 show similar tendency as host 1 (Figure S5). The variable-temperature ESR spectra of inclusion complexes 1•3 and 1•4 indicate that the electronic character of 1 is readily modulated by the clathration of guests. At temperature as low as 123 K (Figure 2b), the spin intensity of 1•3 is 25 times larger than that of original host 1, which can be attributed to the formation of CT complex; however, the ESR signal intensity of 1•4 is 5 times smaller that that of host 1, suggesting the inclusion of electron-rich guest 4 helps the spin delocalization within the frameworks and therefore lowers the intensity of signals of 1•4. As temperature rises to 323 K, the spin intensity of 1•3 exhibits slight decline and becomes 100 times higher than that of host 1, indicating CT complex is extremely stable even at high temperature; in contrast, the spin intensity of 1•4 is similar to that of host 1 (Figures 3b and S5), suggesting electron-rich guest 4 does not affect the spin C
DOI: 10.1021/acs.inorgchem.6b01740 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
Figure 5. (a) Schematic representations of two-electron uptake in the inclusion complex 1•4 during the redox reactions. (b) Voltage composition profiles of 1 (black line) and 1•4 (red line) at the current density of 100 mA g−1. (inset) Cyclic voltammograms of the networked spin cages 1 and inclusion complex 1•4 at a scan rate of 0.1 mV s−1 within the potential range of 1.5−3.5 V vs Li/Li+ (the second cycle was shown for clarity).
Figure 4. (a) Schematic representations of CT complex formation in the inclusion complex 1•3 (left, (TPV) • •(TCNE); right, (TPV)+•(TCNE)−•). (b) The profile of molar magnetic susceptibility with temperature (χmT) vs temperature for networked spin cages 1 and inclusion complex 1•3 at H = 5000 Oe in the temperature range of 2−300 K. (inset) The temperature dependence of inverse molar magnetic susceptibility (1/χm) of 1 and 1•3, which are well-fitted to Curie−Weiss law from 100 to 300 K.
ferromagnetic and anti-ferromagnetic interactions between Co(II) ions and radical ligands. Encapsulation of electronpoor guests increases the spin concentration and enhances the anti-ferromagnetic interactions, attenuating the ferromagnetic interactions. In contrast, inclusion of electron-rich guests provides the π−π interactions and improves the lithium ion binding abilities of networked spin cages, which could be potentially used as cathode materials for lithium batteries. Therefore, our results provide valuable insights for manipulating magnetic and redox properties of a highly ordered solidstate host at the molecular level through the tuning of the spinelectron interactions.
condition (Figures 4b and S8). In addition, the charge/ discharge profiles of 1 show that one mole of lithium ions (x = 1.0) reversibly insert and extract from the networked spin cages 1, indicating a one-electron reaction of TPV radical during lithiation and delithiation processes. Interestingly, 1•4 shows not only one pair of reversible peaks centered at E1/2 = 2.68 V but one additional cathodic peak located at 1.93 V (vs Li/Li+), indicating uptake of additional Li ions (Figure 4b). Such lithium ion bonded state might be stabilized by the π−π interaction of host and electron-rich guest 4 (Figure 5a).20 Therefore, two moles of lithium ions (x = 2.0) can insert in 1•4 when discharged, with ∼1.95 mol extracted during the recharging process (Figure 5). To qualitatively understand lithium binding in the cage, lithium atom binding energy is calculated using DFT (Figures S11 and S12). DFT calculation shows very low binding energy for the second lithium insertion of radical ligand 2, suggesting that only one lithium ion can be inserted into 1, which agrees well with the experimental data shown above. In contrast, the introduction of guest 4 increases the binding energy of the second lithium insertion, indicating the occurrence of synergetic interaction between radical ligand 2 and electron-rich guest 4, which helps the uptake of two lithium ions.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b01740. Additional experimental procedures and IR, solid-state UV−vis spectra, variable-temperature ESR, variabletemperature magnetism data, CV, charge−discharge date, and computational details (PDF) Crystallographic data for 1 (CIF)
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected].
■
Notes
The authors declare no competing financial interest.
CONCLUSION In summary, our work demonstrates a novel networked spin cage constructed from the self-assembly of Co(II) ions and stable verdazyl radicals, which exhibits magnetic and electrochemical activities. The studies of the spin-electron interactions between the host and the guests reveal that the spin concentration and magnetic and redox properties can be modulated. The original host displays coexistence of
■
ACKNOWLEDGMENTS This work is supported by NRF investigator award: “Graphene Oxide−A new case of catalytic, ionic, and molecular sieving materials [R-143-000-610-281]”. B. Tian also acknowledges support from National Natural Science Foundation of China (Grant No. 21506126), Science and Technology Planning D
DOI: 10.1021/acs.inorgchem.6b01740 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
G.; Rovira, C.; Lloret, F.; Tejada, J.; Veciana, J. Coexistence of Ferroand Antiferromagnetic Interactions in a Metal-organic Radical-based (6,3)-helical Network with Large Channels. Chem. Commun. 2005, 41, 5035−5037. (7) For reactivity and stability control: (a) Rebek, J., JR. Molecular Behavior in Small Spaces. Acc. Chem. Res. 2009, 42, 1660−1668. (b) Yoshizawa, M.; Klosterman, J. K.; Fujita, M. Functional Molecular Flasks: New Properties and Reactions within Discrete, Self-assembled Hosts. Angew. Chem., Int. Ed. 2009, 48, 3418−3438. (c) Pluth, M. D.; Bergman, R. G.; Raymond, K. N. Proton-Mediated Chemistry and Catalysis in a Self-Assembled Supramolecular Host. Acc. Chem. Res. 2009, 42, 1650−1659. (d) Breiner, B.; Clegg, J. K.; Nitschke, J. R. Reactivity Modulation in Container Molecules. Chem. Sci. 2011, 2, 51−56. (e) Yoshizawa, M.; Tamura, M.; Fujita, M. Diels-alder in Aqueous Molecular Hosts: Unusual Regioselectivity and Efficient Catalysis. Science 2006, 312, 251−254. (e) Mal, P.; Breiner, B.; Rissanen, K.; Nitschke, J. R. White Phosphorus Is Air-Stable Within a Self-Assembled Tetrahedral Capsule. Science 2009, 324, 1697−1669. (f) Ning, G.-H.; Inokuma, Y.; Fujita, M. Stable Encapsulation of Acrylate Esters in Networked Molecular Capsules. Chem. - Asian J. 2014, 9, 466−468. (8) For photonic control: (a) Saha, S.; Stoddart, J. F. Photo-driven Molecular Devices. Chem. Soc. Rev. 2007, 36, 77−92. (b) Ko, Y. H.; Kim, E.; Hwang, I.; Kim, K. Supramolecular Assemblies Built with Host-stabilized Charge-transfer Interactions. Chem. Commun. 2007, 43, 1305−1315. (c) Wurthner, F.; You, C.-C.; Saha-Moller, C. R. Metallosupramolecular Squares: from Structure to Function. Chem. Soc. Rev. 2004, 33, 133−146. (d) Ning, G.-H.; Yao, L.-Y.; Liu, L.-X.; Xie, T.-Z.; Li, Y.-Z.; Qin, Y.; Pan, Y.-J.; Yu, S.-Y. Self-Assembly and Host-Guest Interaction of Metallomacrocycles Using Fluorescent Dipyrazole Linker with Dimetallic Clips. Inorg. Chem. 2010, 49, 7783− 7792. (9) For magnetic control: (a) Halder, G. J.; Kepert, C. J.; Moubaraki, B.; Murray, K. S.; Cashion, J. D. Guest-dependent Spin Crossover in A Nanoporous Molecular Framework Material. Science 2002, 298, 1762− 1765. (b) Ono, K.; Yoshizawa, M.; Akita, M.; Kato, T.; Tsunobuchi, Y.; Ohkoshi, S.; Fujita, M. Spin Crossover by Encapsulation. J. Am. Chem. Soc. 2009, 131, 2782−2783. (c) Bao, X.; Shepherd, H. J.; Salmon, L.; Molnar, G.; Tong, M.-L.; Bousseksou, A. The Effect of An Active Guest on the Spin Crossover Phenomenon. Angew. Chem., Int. Ed. 2013, 52, 1198−1202. (10) For solution host: (a) Chakrabarty, R.; Mukherjee, P. S.; Stang, P. J. Supramolecular Coordination: Self-Assembly of Finite Two- and Three-Dimensional Ensembles. Chem. Rev. 2011, 111, 6810−6918. (b) Fujita, M.; Tominaga, M.; Hori, A.; Therrien, B. Coordination Assemblies from a Pd (II)-Cornered Square Complex. Acc. Chem. Res. 2005, 38, 369−378. (11) Inokuma, Y.; Arai, T.; Fujita, M. Networked Molecular Cages as Crystalline Sponges for Fullerenes and Other Guests. Nat. Chem. 2010, 2, 780−783. (12) Ning, G.-H.; Inokuma, Y.; Fujita, M. Dynamic Behavior of M6L4 Capsules in Solution and Crystalline States. Chem. - Asian J. 2013, 8, 2596−2599. (13) Nakabayashi, K.; Ozaki, Y.; Kawano, M.; Fujita, M. A SelfAssembled Spin Cage. Angew. Chem., Int. Ed. 2008, 47, 2046−2048. (14) C26H16CoN10S2, Mr = 591.54, cubic Fm3̅m, a = b = c = 36.793 (10) Å, V = 49808 (41) Å3, T = 90(2) K, Z = 24, ρcalcd = 0.473, 900 unique reflections out of 2574 with I > 2σ(I), 58 parameters, final R1 = 0.1486 and wR2 = 0.3790 for all data. CCDC Deposit No. 1487717. Residual electron densities in the solvent-accessible void due to disordered solvent molecules were treated with the PLATON SQUEEZE program. (A. L. Spek, PLATON, An Integrated Tool for the Analysis of the Results of a Single Crystal Structure Determination. Acta Crystallogr., Sect. A: Fundam. Crystallogr., 1990, 46, C34.) Before the treatment of SQUEEZE program, the maximum electron density remaining was 2.259, R1 = 0.3573, and wR2 = 0.6386 for all data. (15) Nakatsuji, S.; Kitamura, A.; Takai, A.; Nishikawab, K.; Morimoto, Y.; Yasuoka, N.; Kawamura, H.; Anzai, H. CT Complexes
Project of Guangdong Province (Grant No. 2016B050501005), Shenzhen Science and Technology Research Foundation (Grant No. JCYJ20150324141711645), and China Postdoctoral Science Foundation (2015M572349).
■
REFERENCES
(1) For the gas storage and separation, see: (a) Kitagawa, S.; Kitaura, R.; Noro, S. Functional Porous Coordination Polymers. Angew. Chem., Int. Ed. 2004, 43, 2334−2375. (b) Ferey, G. Hybrid Porous Solids: Past, Present, Future. Chem. Soc. Rev. 2008, 37, 191−214. (c) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W. H.; Chae, K.; Eddaoudi, M.; Kim, J. A Route to High Surface Area, Porosity and Inclusion of Large Molecules in Crystals. Nature 2003, 423, 705−714. (d) Li, J.-R.; Kuppler, R. J.; Zhou, H.-C. Selective Gas Adsorption and Separation in Metal−organic Frameworks. Chem. Soc. Rev. 2009, 38, 1477−1504. (e) Czaja, A. U.; Trukhan, N.; Mueller, U. Industrial Applications of Metal−organic Frameworks. Chem. Soc. Rev. 2009, 38, 1284−1294. (f) Murray, L. J.; Dinca, M.; Long, J. R. Hydrogen Storage in Metalorganic Frameworks. Chem. Soc. Rev. 2009, 38, 1294−1314. (2) For catalysis, see: (a) Lee, J. Y.; Farha, O. K.; Roberts, J.; Scheidt, K. A. S.; Nguyen, T.; Hupp, J. T. Metal-organic Framework Materials as Catalysts. Chem. Soc. Rev. 2009, 38, 1450−1459. (b) Ma, L.; Abney, C.; Lin, W. Enantioselective Catalysis with Homochiral Metal−organic Frameworks. Chem. Soc. Rev. 2009, 38, 1248−1256. (c) Corma, A.; Garcia, H.; Llabres i Xamena, X. L. Engineering Metal Organic Frameworks for Heterogeneous Catalysis. Chem. Rev. 2010, 110, 4606−4655. (d) Yoon, M.; Srirambalaji, R.; Kim, K. Homochiral Metal−Organic Frameworks for Asymmetric Heterogeneous Catalysis. Chem. Rev. 2012, 112, 1196−1231. (3) For molecule recognition, see: (a) Inokuma, Y.; Yoshioka, S.; Ariyoshi, J.; Arai, T.; Hitora, Y.; Takada, K.; Matsunaga, S.; Rissanen, K.; Fujita, M. X-ray Analysis on The Nanogram to Microgram Scale Using Porous Complexes. Nature 2013, 495, 461−466. (b) Inokuma, Y.; Kawano, M.; Fujita, M. Crystalline Molecular Flasks. Nat. Chem. 2011, 3, 349−358. (c) Ning, G.-H.; Matsumura, K.; Inokuma, Y.; Fujita, M. A Saccharide-based Crystalline Sponge for Hydrophilic Guests. Chem. Commun. 2016, 52, 7013−7015. (d) Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura, K. Preparation, Clathration Ability, and Catalysis of a Two-Dimensional Square Network Material Composed of Cadmium(II) and 4,4′-Bipyridine. J. Am. Chem. Soc. 1994, 116, 1151−1152. (4) For electronic and magnetism applications: (a) Kurmoo, M. Magnetic Metal−organic Frameworks. Chem. Soc. Rev. 2009, 38, 1353−1379. (b) Dechambenoit, P.; Long, J. R. Microporous Magnets. Chem. Soc. Rev. 2011, 40, 3249−3265. (c) Coronado, E.; Mínguez Espallargas, G. Dynamic Magnetic MOFs. Chem. Soc. Rev. 2013, 42, 1525−1539. (5) (a) Power, P. P. Persistent and Stable Radicals of the Heavier Main Group Elements and Related Species. Chem. Rev. 2003, 103, 789−810. (b) Hicks, R. G. What’s New in Stable Radical Chemistry? Org. Biomol. Chem. 2006, 5, 1321−1338. (c) Power, P. P. Main-group Elements as Transition Metals. Nature 2010, 463, 171−177. (d) Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron Compounds; Hicks, R. G., Ed.; John Wiley & Sons, Inc; London, U.K, 2010. (e) Train, C.; Norel, L.; Baumgarten, M. Organic Radicals, a Promising Route Towards Original Molecule-based Magnetic Materials. Coord. Chem. Rev. 2009, 253, 2342−2351. (f) Ratera, I.; Veciana, J. Playing with Organic Radicals as Building Blocks for Functional Molecular Materials. Chem. Soc. Rev. 2012, 41, 303−349. (6) (a) Maspoch, D.; Ruiz-Molina, D.; Wurst, K.; Domingo, N.; Cavallini, M.; Biscarini, F.; Tejada, J.; Rovira, C.; Veciana, J. A Nanoporous Molecular Magnet with Reversible Solvent-induced Mechanical and Magnetic Properties. Nat. Mater. 2003, 2, 190−195. (b) Maspoch, D.; Ruiz-Molina, D.; Wurst, K.; Veciana, J.; et al. A New (63)·(69.81) Non-interpenetrated Paramagnetic Network with Helical Nanochannels Based on a Tricarboxylic Perchlorotriphenylmethyl Radical. Chem. Commun. 2004, 40, 1164−1165. (c) Maspoch, D.; Domingo, N.; Ruiz-Molina, D.; Wurst, K.; Hernandez, J.-M.; Vaughan, E
DOI: 10.1021/acs.inorgchem.6b01740 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry Derived from Verdazyl Radicals. Z. Naturforsch., B: J. Chem. Sci. 1998, 53b, 495−502. (16) (a) Chappell, J. S.; Bloch, A. N.; Bryden, W. A.; Maxfield, M.; Poehler, T. O.; Cowan, D. O. Degree of Charge Transfer in Organic Conductors by Infrared Absorption Spectroscopy. J. Am. Chem. Soc. 1981, 103, 2443−2446. (b) Stires, J. C., IV; McLaurin, E. J.; Kubiak, C. P. Infrared Spectroscopic Determination of the Degree of Charge Transfer in Complexes of TCNE with Methyl-substituted Benzenes. Chem. Commun. 2005, 28, 3532−3534. (17) Poole, C. P.; Farach, H. A. Line Shapes in Electron Spin Resonance. Bull. Magn. Reson. 1979, 1, 162−194. (18) Weil, J. A.; Bolton, J. R. Electron Paramagnetic Resonance. Elementary Theory and Practical Applications, 2nd ed.; WileyIntersciene, 2007; pp 322−324. (19) Wang, C.; Dong, H.; Hu, W.; Liu, Y.; Zhu, D. Semiconducting π-conjugated Systems in Field-effect Transistors: A Material Odyssey of Organic Electronics. Chem. Rev. 2012, 112, 2208−2267. (20) It is noteworthy that when the TPV ligand is simply mixed with guest 4, the plateau at ∼1.9 V does not appear, revealing that the rigid three-dimensional arrangement of TPV ligand and guest 4 are essential for the stabilization of intermediate state.
F
DOI: 10.1021/acs.inorgchem.6b01740 Inorg. Chem. XXXX, XXX, XXX−XXX
