Rhodium–Organic Cuboctahedra as Porous Solids with Strong

Oct 17, 2016 - (20-23) Because of its preorganized internal porosity, we particularly focus on the cuboctahedron structure, [M2(L)2]12, constructed fr...
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Rhodium−Organic Cuboctahedra as Porous Solids with Strong Binding Sites Shuhei Furukawa,*,† Nao Horike,† Mio Kondo,†,‡ Yuh Hijikata,§ Arnau Carné-Sánchez,† Patrick Larpent,† Nicolas Louvain,† Stéphane Diring,† Hiroshi Sato,† Ryotaro Matsuda,† Ryuji Kawano,⊥ and Susumu Kitagawa*,† †

Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, Higashiyama 5-1, Myodaiji, Okazaki 444-8787, Japan § Institute of Transformative Bio-Molecules (WPI-ITbM) and Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan ⊥ Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi Tokyo 184-8588, Japan ‡

S Supporting Information *

Paddlewheel motifs of particular interest are the ones based on dirhodium metal ions (Rh2). Indeed, owing to their high chemical stability and good catalytic activities, such clusters are of significant interest as building nodes for the construction of MOFs.17 However, the relative inertness of their equatorial carboxylates renders their use for the formation of extended structures through ligand-exchange reactions difficult. Therefore, several alternative strategies to incorporate Rh2 units have been suggested; molecular Rh2 units are assembled by noncovalent interaction or by another conventional copper carboxylate coordination bond.18,19 However, both cases lead to the construction of two-dimensional frameworks, and it is still challenging to design the resulting porous structure with targeted properties. Here we demonstrate a rather straightforward approach to fabricating Rh2-based solid-state porous materials by assembling a metal−organic polyhedron (MOP), which is a cage-type molecule with intrinsic porous structure therein and thus is recognized as the smallest pore unit of MOFs.20−23 Because of its preorganized internal porosity, we particularly focus on the cuboctahedron structure, [M2(L)2]12, constructed from 12 units of dimetal paddlewheels (M2) with 24 dicarboxylate bridging linkers (L) such as 1,3-benzendicarboxylate (bdc) derivatives.21−26 We show the synthesis of rhodium-based metal− organic cuboctahedra, [Rh2(bdc)2(solv)2]12·(solv) (1), which have two topological isomers, cuboctahedron (1a) and anticuboctahedron (1b) structures (solv = solvent molecules). The sorption experiments reveal that the rhodium-based MOP of 1b possesses a much higher adsorption capacity than the isostructural copper analogue. Detailed analyses of IR spectroscopy using carbon monoxide (CO) and nitric oxide (NO) molecules, together with theoretical calculations, unveil the strong molecular affinity at the OMSs of Rh2 units due to the characteristic π-back-donation from the Rh2 centers to CO. On the other hand, NO demonstrated irreversible sorption behavior

ABSTRACT: The upbuilding of dirhodium tetracarboxylate paddlewheels into porous architectures is still challenging because of the inertness of equatorial carboxylates for ligand-exchange reaction. Here we demonstrate the synthesis of a new family of metal− organic cuboctahedra by connecting dirhodium units through 1,3-benzenedicarboxylate and assembling cuboctahedra as porous solids. Carbon monoxide and nitric oxide were strongly trapped in the internal cavity thanks to the strong affinity of unsaturated axial coordination sites of dirhodium centers.

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oordination framework materials, known as porous coordination polymers or metal−organic frameworks (MOFs) built from organic links and inorganic clusters,1−3 are recognized as an intriguing class of porous materials because of designable pore functionalities and their potential applications in storage, separation, catalysis, and sensors.4 One of the advantages that MOFs can offer is to incorporate metal ions with unsaturated coordination sites into their scaffold, known as open metal sites (OMSs), with which guest molecules have been shown to strongly interact.5 Such a preferential interaction gives benefits, in particular, for applications in separation and sensors, where the selective binding to a target molecule among others is essential for high performance,6−8 and for catalysis application because most of OMSs work as Lewis acidic sites.9−11 Therefore, a protocol to generate OMSs in MOF structures is key for the further development of MOFs for practical applications. Among a variety of metal clusters, the dimetal paddlewheel cluster with tetracarboxylates is recognized to be one of the most conventional building blocks because several benchmarks of MOFs have been constructed with these types of clusters.12,13 Although classical coordination chemistry allows us to incorporate a variety of transition-metal ions into cluster molecules, connecting them with links is required to synthesize MOFs, which often limits the usage of metal ions, copper and zinc in most cases12,13 and rarely nickel, cobalt, and iron.14−16 © XXXX American Chemical Society

Received: August 29, 2016

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DOI: 10.1021/acs.inorgchem.6b02091 Inorg. Chem. XXXX, XXX, XXX−XXX

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activation.30−32 However, the structures that we demonstrated here, known to be the most primitive derivative of a cuboctahedral MOP, [M2(bdc)2]12, have a lack of such intermolecular interactions, and, therefore, the powder X-ray diffraction (PXRD) experiments demonstrated that crystalline compounds of 1b and its copper analogue21 were converted to amorphous after the activation procedure at 393 K (Figure S1). On the other hand, thermogravimetric analyses of the assynthesized crystalline powders of both compounds showed different behaviors; the decomposition temperature of 1b is over 573 K, which is significantly higher than its copper analogue (around 533 K; Figure S2). The IR spectroscopy experiments after activation support this difference in stability between the rhodium and copper isostructures (Figure S3). No apparent change in the region of the carboxylate stretching vibration observed for 1b suggests the maintenance of the molecular structure. In contrast, those stretching modes of the copper analogue broadened after activation and significantly changed in intensity and position, which implies destruction of the copper paddlewheel structure. These results suggest that, although there is a total loss of the long-range order of the packing structures, the rhodium-based MOP of 1b maintains its molecular structure even after activation, thanks to the strong metal−metal single bond between the rhodium ions. In order to comprehend the stability of the rhodium-based cuboctahedron, we compared the adsorption properties of 1b with those of the copper analogue. The nitrogen adsorption isotherms of 1b and the copper analogue at 77 K are illustrated in Figure 2a. On the one hand, the copper-based MOP showed a very subtle amount of nitrogen uptake after activation at 323 K under vacuum for 3 h and even after a milder activation process using supercritical carbon dioxide (CO2) treatment. These results suggest that the copper analogue became nonporous and did not maintain its porosity after solvent removal. On the other hand, 1b was successfully activated by thermal treatment at 368 K under vacuum for 3 h or by supercritical CO2 treatment. As shown in Figure 2a, 1b showed a typical type I nitrogen sorption at low relative pressure [130 cm3 g−1 (STP) at P/P0 = 0.1], which confirmed that the rhodium-based MOP possesses microporosity due to the rigid Rh2 paddlewheel units (the pore-size distribution is illustrated in Figure S4). Thanks to such a high structural integrity, we further investigated the affinity of OMSs at the axial position of the Rh2 paddlewheel units using the adsorption of NO or CO. The adsorption isotherms of 1b for NO or CO at 273 K are shown in Figure 2b. Both molecules were adsorbed at the very low pressure. Two NO molecules were significantly adsorbed per Rh2 unit, which indicates coordination to two vacant axial sites of the paddlewheel. However, one CO molecule per Rh2 unit was adsorbed, indicating that only one axial site was occupied by CO. Note that dirhodium tetracarboxylate complexes are rarely coordinated by CO.33 Thus, we assume that CO binds to the OMSs exposed to the inner space of the MOP, in which a nanosized confinement effect most likely supports the accumulation of molecules therein. Importantly, the coordinated NO molecules were not desorbed even at very low pressure (0.1 kPa), whereas CO gradually desorbed. To gain insight into the affinity of OMSs, we further investigated the materials through in situ IR spectroscopy. At a high pressure of CO (P = 10 kPa), the characteristic peak of the C−O stretching vibration was observed at 2091 cm−1, which was significantly red-shifted from the vibration of a free CO molecule (2143 cm−1; Figure S5). This lower-energy shift highlights the

because of the formation of a covalent Rh−N bond through breaking of the Rh−Rh bond. Compounds 1a and 1b were synthesized using a solvothermal method by the reactions of Rh2(OAc)4(methanol)2 with H2bdc either in methanol for 1b or in a methanol/DMPU mixture for 1a (OAc = acetate; DMPU = N,N′-dimethylpropyleneurea). We followed the previously reported procedure,27 which described that the use of DMPU distinctively provided the cuboctahedron phase of molybdenum analogues. Compound 1a crystallizes in the triclinic space group P1̅, and each of the Rh2 paddlewheel units is coordinated by four bdc ligands to form a cuboctahedron architecture (Figure 1a),28 in the same manner as the

Figure 1. Crystal structures and schematic illustrations of (a) the cuboctahedral architecture of 1a and (b) the anticuboctahedral architecture of 1b. Coordinated molecules at axial positions were modeled as oxygen atoms. Crystal solvent molecules and hydrogen atoms were omitted for clarity.

molybdenum analogues.27 The six crystallographically distinct Rh−Rh distances of Rh2 paddlewheels are in the range from 2.3962(12) to 2.4032(12) Å, recognized as typical Rh−Rh single-bond distances.17 On the other hand, compound 1b crystallizes in the hexagonal space group P63/m and forms an anticuboctahedron architecture with typical Rh−Rh distances [in the range from 2.3959(10) to 2.3997(14) Å].29 Similar to other analogues, both cuboctahedron and anticuboctahedron possess eight triangular and six square windows. Compounds 1a and 1b are chemically identical, except for the axial coordination molecules on the Rh2 dimer unit (DMPU for 1a and methanol for 1b), but are geometrically different; the cuboctahedron structure of 1a has higher symmetry, in which the upward triangular panel is arranged parallel to the downward triangular panel at the opposite side. The square panel is arranged parallel to the square panel at the opposite side. On the other hand, the anticuboctahedron of 1b has lower symmetry; two out of eight triangular panels are aligned parallel in an upward fashion, and each of the other six triangular panels is arranged parallel to the square panel, which means that the anticuboctahedron structure possesses a specific direction in its molecular geometry with the view from the triangle−triangle panels, as illustrated in Figure 1b. Compared to MOFs that have extended structures with highorder connectivity between the metal clusters, three-dimensional arrangements of a discrete MOP simply rely on intermolecular interactions, which easily lead to an amorphous phase by the removal of crystal solvents and thus to almost no permanent porosity after the removal of solvents (activation). One of the ways to overcome this shortcoming is to interconnect MOPs by introducing stronger interactions such as coordination bonds. Several research groups succeeded in the formation of one-, two-, and three-dimensional arrays of copper-based MOPs and in the maintenance of their crystallinity and porosity even after B

DOI: 10.1021/acs.inorgchem.6b02091 Inorg. Chem. XXXX, XXX, XXX−XXX

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molecule per paddlewheel cluster was adsorbed. This is most likely due to electronic repulsion through the dσ orbital of the Rh−Rh bond between the lone pair of CO molecules. In the case of NO, at high pressure (P = 30 kPa), a characteristic N−O stretching vibration peak appeared at 1698 cm−1, which also shifted to the lower energy from free NO (1900 cm−1). However, this peak remained after a decrease in the pressure to 50 Pa (Figure 2c) or even after thermal treatment at 353 K for 30 min (Figure S7). Theoretical analysis using the model Rh2(HCO2)4(NO)2 suggested the breaking of the Rh−Rh bond and the reformation of covalent Rh−N bonds (Figure S8), which is in agreement with the previous report.36 In contrast to the case of CO coordination, the second NO coordination is more favored; Eb of the first coordination was estimated to be 29.0 kcal mol−1 and that of the second coordination to be 35.6 kcal mol−1. Because NO coordination involves Rh−Rh bond breaking, the second coordination should be expected to compensate for unpaired electrons of both rhodium ions by covalent Rh−N bond formation with a NO radical. These calculation results unambiguously address the irreversible adsorption of NO in 1b. In conclusion, we demonstrated the synthesis of rhodium− organic cuboctahedra with Rh2 paddlewheel units as porous solids. Thanks to the characteristic electronic structure of the Rh−Rh bond, the axial coordination site works as a strong binding site, in particular, to π-acceptor ligands such as CO. These types of porous solids would give a new opportunity not only for applications in separation or catalysis but also for the synthesis of new framework materials by the incorporation of cuboctahedra as building blocks.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b02091. Full experimental procedures, thermogravimetric analysis data, PXRD data, IR and in situ IR spectroscopic data, and theoretical calculation data (PDF) X-ray crystallographic data in CIF format for 1a (CIF) X-ray crystallographic data in CIF format for 1b (CIF)

Figure 2. (a) Nitrogen adsorption isotherms of 1b and the copper analogue at 77 K after supercritical CO2 activation. (b) Sorption isotherms of 1b for NO and CO. (c) In situ IR spectra of 1b at 195 K under decreasing pressure of NO.

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effect of π-back bonding from the dπ* orbital of the Rh−Rh bond to the pπ* orbital of CO. When the pressure was decreased, the intensity of this peak also decreased and finally disappeared after thermal treatment at 353 K for 40 min (Figure S4). We further confirmed significant π-back-donation by theoretical analysis using the paddlewheel model complex of Rh2(HCO2)4(CO)2 (Figure S6); the contribution from π-back-donation to the Rh− C coordination bond formation (0.184 e) is much larger than that from σ donation (0.098 e). This guest binding affinity of the Rh2 complex is distinguishable from the conventional copper analogue of Cu2(HCO2)4(CO)2, in which the σ donation dominates the coordination interaction with CO (Figure S6).34,35 Importantly, theoretical analysis gave further insight into the binding mechanism of CO on the rhodium center. The binding energy (Eb) of the first CO coordination on the rhodium center was estimated to be 25.4 kcal mol−1 and that of the second coordination of CO and to be 17.0 kcal mol−1 (see the Supporting Information for a detailed description). This result indicates that the second coordination is rather less favored compared to the first coordination, and, therefore, only one CO

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (S.F.). *E-mail: [email protected] (S.K.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by a Grant-in-Aid for Scientific Research (Grant 15K13771 to S.F.). iCeMS is supported by the World Premier International Research Initiative, Ministry of Education, Culture, Sports, Science and Technology of Japan. N.L., P.L., and A.C.-S. are grateful to the JSPS Postdoctoral Fellowship Program for Foreign Researchers.

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REFERENCES

(1) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Reticular synthesis and the design of new materials. Nature 2003, 423, 705−714.

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Inorganic Chemistry (2) Kitagawa, S.; Kitaura, R.; Noro, S. Functional porous coordination polymers. Angew. Chem., Int. Ed. 2004, 43, 2334−2375. (3) Feŕey, G. Hybrid porous solids: past, present, future. Chem. Soc. Rev. 2008, 37, 191−214. (4) Metal−organic frameworks were the topic of recent special themed issues in Chem. Rev. and Chem. Soc. Rev.: (a) Zhou, H.-C.; Long, J. R.; Yaghi, O. M. Introduction to Metal−Organic Frameworks. Chem. Rev. 2012, 112, 673−674. (b) Zhou, H.-C.; Kitagawa, S. Metal−Organic Frameworks (MOFs). Chem. Soc. Rev. 2014, 43, 5415−5418. (5) Kim, K.; Seo, J. S.; Whang, D.; Lee, H.; Jun, S. I.; Oh, J.; Jeon, Y. J. A homochiral metal−organic porous material for enantioselective separation and catalysis. Nature 2000, 404, 982−986. (6) Li, J.-R.; Sculley, J.; Zhou, H.-C. Metal−Organic Frameworks for Separations. Chem. Rev. 2012, 112, 869−932. (7) Nugent, P.; Belmabkhout, Y.; Burd, S. D.; Cairns, A. J.; Luebke, R.; Forrest, K.; Pham, T.; Ma, S.; Space, B.; Wojtas, L.; Eddaoudi, M.; Zaworotko, M. J. Porous materials with optimal adsorption thermodynamics and kinetics for CO2 separation. Nature 2013, 495, 80−84. (8) McDonald, T. M.; Mason, J. A.; Kong, X.; Bloch, E. D.; Gygi, D.; Dani, A.; Crocellá, V.; Giordanino, F.; Odoh, S. O.; Drisdell, W. S.; Vlaisavljevich, B.; Dzubak, A. L.; Poloni, R.; Schnell, S. K.; Planas, N.; Lee, K.; Pascal, T.; Wan, L. F.; Prendergast, D.; Neaton, J. B.; Smit, B.; Kortright, J. B.; Gagliardi, L.; Bordiga, S.; Reimer, J. A.; Long, J. R. Cooperative insertion of CO2 in diamine-appended metal-organic frameworks. Nature 2015, 519, 303−308. (9) Corma, A.; García, H.; Llabrés I Xamena, F. X. Engineering Metal Organic Frameworks for Heterogeneous Catalysis. Chem. Rev. 2010, 110, 4606−4655. (10) Vermoortele, F.; Bueken, B.; Le Bars, G.; Van de Voorde, B.; Vandichel, M.; Houthoofd, K.; Vimont, A.; Daturi, M.; Waroquier, M.; Van Speybroeck, V.; Kirschhock, C.; De Vos, D. E. Synthesis Modulation as a Tool To Increase the Catalytic Activity of Metal− Organic Frameworks: The Unique Case of UiO-66(Zr). J. Am. Chem. Soc. 2013, 135, 11465−11468. (11) Aguirre-Díaz, L. M.; Gándara, F.; Iglesias, M.; Snejko, N.; Gutiérrez-Puebla, E.; Monge, M. A. Tunable Catalytic Activity of Solid Solution Metal−Organic Frameworks in One-Pot Multicomponent Reactions. J. Am. Chem. Soc. 2015, 137, 6132−6135. (12) Chui, S. S.-Y.; Lo, S. M.-F.; Charmant, J. P. H.; Orpen, A. G.; Williams, I. D. A chemically functionalizable nanoporous material. Science 1999, 283, 1148−1150. (13) Li, H.; Eddaoudi, M.; Groy, T. L.; Yaghi, O. M. Establishing Microporosity in Open Metal−Organic Frameworks: Gas Sorption Isotherms for Zn(BDC) (BDC = 1,4-Benzenedicarboxylate). J. Am. Chem. Soc. 1998, 120, 8571−8572. (14) Lee, S. W.; Kim, H. J.; Lee, Y. K.; Park, K.; Son, J.-H.; Kwon, Y.-U. Triply interpenetrating coordination polymers based on paddle-wheel type secondary-building units of M 2 (CO 2 R) 4 : [Ni 3 (2,6NDC)3(bipy)1.5], [Co3(2,6-NDC)3(bipy)1.5], and [Co(1,3-BDC) (bipyen)] (2,6-NDC = 2,6-naphthalenedicarboxylate; 1,3-BDC = 1,3benzenedicarboxylate; bipy = 4,4′-bipyridine; bipyen = trans-1,2-bis(4pyridyl)ethylene). Inorg. Chim. Acta 2003, 353, 151−158. (15) Wang, H.; Getzschmann, J.; Senkovska, I.; Kaskel, S. Structural transformation and high pressure methane adsorption of Co2(1,4bdc)2dabco. Microporous Mesoporous Mater. 2008, 116, 653−657. (16) Kongpatpanich, K.; Horike, S.; Sugimoto, M.; Kitao, S.; Seto, M.; Kitagawa, S. A porous coordination polymer with a reactive diiron paddlewheel unit. Chem. Commun. 2014, 50, 2292−2294. (17) Cotton, F. A.; Walton, R. A. Multiple Bonds between Metal Atoms, 2nd ed.; Oxford University Press: New York, 1993. (18) Matsunaga, S.; Hasada, K.; Sugiura, K.; Kitamura, N.; Kudo, Y.; Endo, N.; Mori, W. Hetero Bi-Paddlewheel Coordination Networks: a New Synthetic Route to Rh-containing Metal-Organic Frameworks. Bull. Chem. Soc. Jpn. 2012, 85, 433−438. (19) Itoh, T.; Kondo, M.; Sakamoto, H.; Wakabayashi, K.; Kanaike, M.; Itami, K.; Masaoka, S. Porous frameworks constructed by non-covalent linking of substitution-inert metal complexes. Dalton Trans. 2015, 44, 15334−15342.

(20) Tranchemontagne, D. J.; Ni, Z.; O’Keeffe, M.; Yaghi, O. M. Reticular chemistry of metal-organic polyhedral. Angew. Chem., Int. Ed. 2008, 47, 5136−5147. (21) Eddaoudi, M.; Kim, J.; Wachter, J. B.; Chae, H. K.; O’Keeffe, M.; Yaghi, O. M. Porous Metal−Organic Polyhedra: 25 Å Cuboctahedron Constructed from 12 Cu2(CO2)4 Paddle-Wheel Building Blocks. J. Am. Chem. Soc. 2001, 123, 4368−4369. (22) Moulton, B.; Lu, J.; Mondal, A.; Zaworotko, M. J. Nanoballs: nanoscale faceted polyhedra with large windows and cavities. Chem. Commun. 2001, 863−864. (23) Li, J.-R.; Zhou, H.-C. Bridging-ligand-substitution strategy for the preparation of metal−organic polyhedral. Nat. Chem. 2010, 2, 893−898. (24) Li, J.-R.; Yakovenko, A. A.; Lu, W.; Timmons, D. J.; Zhuang, W.; Yuan, D.; Zhou, H.-C. Ligand Bridging-Angle-Driven Assembly of Molecular Architectures Based on Quadruply Bonded Mo−Mo Dimers. J. Am. Chem. Soc. 2010, 132, 17599−17610. (25) Young, M. D.; Zhang, Q.; Zhou, H.-C. Metal−organic polyhedra constructed from dinuclear ruthenium paddlewheels. Inorg. Chim. Acta 2015, 424, 216−220. (26) Teo, J. M.; Coghlan, C. J.; Evans, J. D.; Tsivion, E.; Head-Gordon, M.; Sumby, C. J.; Doonan, C. J. Hetero-bimetallic metal−organic polyhedral. Chem. Commun. 2016, 52, 276−279. (27) Ke, Y.; Collins, D. J.; Zhou, H.-C. Synthesis and Structure of Cuboctahedral and Anticuboctahedral Cages Containing 12 Quadruply Bonded Dimolybdenum Units. Inorg. Chem. 2005, 44, 4154−4156. (28) Crystal data for 1a: C192H96O120Rh24, triclinic, space group P1̅ (No. 2), a = 22.543(5) Å, b = 24.369(5) Å, c = 24.845(5) Å, α = 97.049(2)°, β = 114.1070(10)°, γ = 111.849(2)°, V = 10939(4) Å3, Z = 1, T = 153(2) K, ρcalcd = 1.031 g cm−3, μ(Mo Kα) = 0.932 cm−1, 75518 reflections measured, 37886 observed, 1513 parameters; R1 [I > 2.00σ(I)] = 0.0698, wR2 = 0.1934, GOF = 0.868 (CCDC 1501072). (29) Crystal data for 1b: C32H16O20Rh4, trigonal, space group P63/m (No. 176), a = 28.671(8) Å, c = 28.464(8) Å, V = 20263(10) Å3, Z = 12, T = 153(2) K, ρcalcd = 1.113 g cm−3, μ(Mo Kα) = 1.006 cm−1, 158184 reflections measured, 12131 observed, 553 parameters; R1 [I > 2.00σ(I)] = 0.0927, wR2 = 0.2733, GOF = 1.082 (CCDC 1501073). (30) Liu, T.-F.; Chen, Y.-P.; Yakovenko, A. A.; Zhou, H.-C. Interconversion between Discrete and a Chain of Nanocages: SelfAssembly via a Solvent-Driven, Dimension-Augmentation Strategy. J. Am. Chem. Soc. 2012, 134, 17358−17361. (31) Niu, Z.; Fang, S.; Liu, X.; Ma, J.-G.; Ma, S.; Cheng, P. Coordination-Driven Polymerization of Supramolecular Nanocages. J. Am. Chem. Soc. 2015, 137, 14873−14876. (32) Chen, T.-H.; Wang, L.; Trueblood, J. V.; Grassian, V. H.; Cohen, S. M. Poly(isophthalic acid) (ethylene oxide) as a Macromolecular Modulator for Metal−Organic Polyhedra. J. Am. Chem. Soc. 2016, 138, 9646−9654. (33) Pirrung, M. C.; Morehead, A. T., Jr. Electronic Effects in Dirhodium(II) Carboxylates. Linear Free Energy Relationships in Catalyzed Decompositions of Diazo Compounds and CO and Isonitrile Complexation. J. Am. Chem. Soc. 1994, 116, 8991−9000. (34) Sato, H.; Kosaka, W.; Matsuda, R.; Hori, A.; Hijikata, Y.; Belosludov, R. V.; Sakaki, S.; Takata, M.; Kitagawa, S. Self-accelerating CO sorption in a soft nanoporous crystal. Science 2014, 343, 167−170. (35) Hijikata, Y.; Sakaki, S. Interaction of Various Gas Molecules with Paddle-Wheel-Type Open Metal Sites of Porous Coordination Polymers: Theoretical Investigation. Inorg. Chem. 2014, 53, 2417−2426. (36) Sizova, O. V. The valence structure analysis for dirhodium(II) tetracarboxylato complexes with nitric oxide as axial ligand. J. Mol. Struct.: THEOCHEM 2006, 760, 183−187.

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DOI: 10.1021/acs.inorgchem.6b02091 Inorg. Chem. XXXX, XXX, XXX−XXX