High-Nuclear Vanadoniobate {Nb48V8} Multiple-Strand Wheel

Nov 23, 2015 - ACS Journals. ACS eBooks; C&EN Global Enterprise .... High-Nuclear Vanadoniobate {Nb48V8} Multiple-Strand Wheel. Yu-Teng Zhang, Chao ...
0 downloads 0 Views 2MB Size
Download PDF
Article pubs.acs.org/IC

High-Nuclear Vanadoniobate {Nb48V8} Multiple-Strand Wheel Yu-Teng Zhang, Chao Qin, Xin-Long Wang,* Peng Huang, Bai-Qiao Song, Kui-Zhan Shao, and Zhong-Min Su* Institute of Functional Material Chemistry, Key Laboratory of Polyoxometalate Science of Ministry of Education, Northeast Normal University, Changchun, 130024 Jilin, People’s Republic of China S Supporting Information *

ABSTRACT: An unprecedented octavanadium-substituted polyoxoniobate Na18[Nb48V8(OH)30O130]·33H2O (1), with a multiplestrand wheel structure, was successfully synthesized via a conventional aqueous method, which represents the largest vanadoniobate cluster reported to date. Single-crystal X-ray diffraction, ESI-MS spectrum, IR spectra, and UV−vis spectra were investigated. In addition, photocatalytic H2 evolution activity for 1 under UV light was observed with TEA as a sacrificial electron donor.

■

INTRODUCTION Polyoxometalates (POMs) science is an interesting area involving the condensation of “monomeric” metal (W, Mo, V, Nb, Ta)−oxo units into “polymers” of these units via shared oxo ligands.1 POMs have attracted enormous interest in the field of inorganic synthesis and solid state chemistry owing to their unique structure characteristics and multiple functions in catalysis, nanotechnology, medicine, and magnetism.2 Compared with the classic Keggin, Wells−Dawson, and Anderson POMs, the assembly of high-nuclear POMs molecular wheels, such as {Mo154}, {Mo176}, and the “hedgehog-like” {Mo368},3 is striking not only because of their inherent symmetry, molecular complexity, and architectural beauty but also because they represent a new type of self-assembly of POMs building units. Unfortunately, the assembly principle depends on some factors such as reaction temperature, pH, crystallization methods, and so on. Therefore, it is difficult to summarize the interior rule of their synthesis especially for the wheel-type compounds. An intriguing type within the realm of wheel compounds is the single-strand molecular wheel, which simply describes linked monometallic units. The prototype [{Fe(OMe)2(O2CCH2Cl)}10] was praised as a “ferric wheel”.4 Since then many other single-strand wheels have been reported and enriched the family of molecular wheels.5 For another type, multiple-strand wheels are also known, such as the giant torusshaped {Mn84},6 {Mo154}, and {Mo176} species, though they are especially uncommon. Multiple-strand wheels can be classified into two subsets: (i) wheels constructed from repeating metal clusters7 and (ii) complexes that consist of multiple linked parallel wheels. The latter structure type is extremely rare, being limited to {V12}, {Mn10}, {Mn16}, and {Cu12} wheels.8 Inspiringly, Brechin and co-workers reported a beautiful mixed-valent {Mn32} double-decker wheel, which displays single-molecule magnet behavior.9 Recently, Cronin’s group © XXXX American Chemical Society

obtained a 7-fold symmetric {Pd84} wheel and predicted the assembly of nanoscale architectures.10 As a rising subclass of POMs, polyoxoniobates (PONbs) have attracted significant interest due to their unmatched physical and chemical properties and potential applications in nuclear-waste treatment, virology, and photocatalysis.11 Though possessing good potential, the development of PONbs is relatively at an early stage, partly because of the alkalinity that is incompatible with the solubility of most metal cations and the limited building unit that has been dominated by the classical polyanion [Nb6O19]8−.12 Some pioneer works have been made by Nyman, Casey, Cronin, Yagasaki, Niu, Wang, Hu, and others. To the best of our knowledge, the largest number of niobiums in isopolyoxoniobates is still 32 (Figure 1b). Also, abundant heteropolyoxoniobates are known. It is worth noting that the research of transition-metal-substituted PONbs has been made some good progress in recent years. A detailed literature survey of PONbs is shown in Table 1. Inspired by the aforementioned prominent work, we successfully obtained a novel octavanadium-substituted polyoxoniobate Na18[Nb48V(IV)8(OH)30O130]·33H2O (abbreviated as {Nb48V8}, 1) by a conventional aqueous method. The reaction equation for the formation of 1 is speculated as follows 8VCl3 + 2O2 + 18H 2O + 8[HNb6O19]7 − = [V8Nb48(OH)30 O130 ]18 − + 24Cl− + 14OH−

Compound 1 was synthesized by a conventional aqueous method to give well-grown cuboid crystals (Figure 2c), even though most of the vanadium-containing PONbs were prepared under hydrothermal conditions. Polyoxometalate Received: May 12, 2015

A

DOI: 10.1021/acs.inorgchem.5b01936 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

Figure 2. (a) Ball-and-stick representation of the {Nb48V8} cluster, highlighting the arrangement of the internal eight [VNb6O22]10− units by different colors. The shadow represents the space-filling plane view of 1. (b) Side view of 1. (c) SEM images of the crystals of compound 1 (inset, high-magnification image).

Figure 1. Schematic representation of the self-assembly process of (a) triangular molecular analogous {Nb24} cluster, (b) rectangular molecular analogous {Nb32} cluster, and (c) circular molecular analogous {Nb48V8} cluster. Color scheme for polyhedral: [Nb6O19] (pine green), [NbO6] (red), [VO6] (pink).

■

Table 1. Survey of Known Polyoxoniobates polyanion

ref isopolyoxoniobates

Lindqvist et al. (1953)12 Graeber et al. (1977)13a Yagasaki et al. (2006)13b Nyman et al. (2006)13c Cronin et al. (2010)13d Cronin et al. (2010)13d Wang et al. (2012)13e heteropolyoxoniobates {[Ti2O2][SiNb12O40]}12− Nyman et al. (2002)14a 15− [(PO2)3PNb9O34] Nyman et al. (2006)14b 14− [H2Si4Nb16O56] Nyman et al. (2008)14c [GeNb13O41]13− Nyman et al. (2013)14d 5− [H2TeNb5O19] Casey et al. (2014)14e 4.5− [As2Nb4(O2)4O14H1.5] Niu et al. (2014)14f TM-substituted PONbsa [Cr2(OH)4Nb10O30]8− Casey et al. (2012)15a 6− [H2FeNb9O28] Casey et al. (2013)15b 6− [H3NiNb9O28] Casey et al. (2013)15c [H2MnNb10O32]8− Casey et al. (2013)15c [Cu24(Nb7O22)8H23NaO8]16− Niu et al. (2007)15d 9− [CuNb11O35H4] Niu et al. (2010)15e 20− [Co14(OH)16(H2O)8Nb36O106] Niu et al. (2014)15f [H2Co8O4(Nb6O19)4]18− Niu et al. (2015)15g [Ti2Nb8O28]8− Nyman et al. (2003)16b 10− [Ti12Nb6O44] Casey et al. (2008)16a 7− [TiNb9O28] Casey et al. (2009)16c [VNb12O40(VO)2]9− Hu et al. (2011)17a 4− [H6V4Nb6O30] Hu et al. (2012)17b 12− [V4Nb10O40(OH)2] Wang et al. (2012)17c 9− [PV2Nb12O42] Casey et al. (2013)17d [PNb12O40(VO)6]3− Wang et al. (2014)17e

[Nb6O19]8− [Nb10O28]6− [Nb20O54]8− [H9Nb24O72]15− [HNb27O76]16− [H10Nb31O93(CO3)]23− [Nb32O96H28]4−

a

EXPERIMENTAL SECTION

Materials. All reagents except K7HNb6O19·13H2O19 were obtained from commercial sources and used without further purification. Instruments. The size and morphology of the products were investigated by an XL-30 field emission scanning electron microscope (SEM) made by FEI Co. Powder X-ray diffraction (PXRD) measurement was recorded ranging from 5 to 40° at room temperature on a Siemens D5005 diffractometer with Cu Kα (λ = 1.5418 Å). The IR spectrum was performed in the range 4000−400 cm−1 using KBr pellets on an Alpha Centaurt FT/IR spectrophotometer. X-ray photoelectron spectroscopy analyses were performed on a VG ESCALABMKII spectrometer with an Al Kα (1486.6 eV) achromatic X-ray source. The vacuum inside the analysis chamber was maintained at 6.2 × 10−6 Pa during analysis. Elemental analyses (Nb, V, Na) were measured with a Plasma-SPEC (I) ICP atomic emission spectrometer; H was determined on a PerkinElmer 2400 CHN elemental analyzer. Thermogravimetric analysis (TGA) of the samples was performed using a PerkinElmer TG-7 analyzer heated from 50 to 800 °C under nitrogen at a heating rate of 10 °C·min−1. The UV−vis diffuse reflectance spectrum was recorded at ambient temperature on a Cary-500 UV−vis Spectrophotometer. Electrospray ionization mass spectrometry was carried out with a Bruker Micro TOF-QII instrument. Raman scattering spectra were obtained by a Renishaw Invia Raman Microscope using 532 nm laser excitation. Synthesis of K7HNb6O19·13H2O. Nb2O5 (13.3 g) was added slowly to a melt of 26 g of KOH in a nickel crucible. After about 30 min, the melt was cooled to room temperature and dissolved in 100 mL of distilled water. After stirring for a period of time, the mixture was filtered. Then the filtrate was transferred to a 150 mL beaker. The solution volume was reduced to ca. 50 mL. Then crystalline product formed after 12 h at 0 °C. These crystals were filtered off, washed with 1:1 (v/v) ethanol−water and absolute ethanol, and dried in vacuum. Synthesis and Characterization of 1. Vanadium(III) chloride (VCl3, 0.157 g, 1 mmol) was added to 10 mL of distilled water with stirring. Then the clear solution was dropwise added to an aqueous solution (50 mL) containing K7HNb6O19·13H2O (0.685 g, 0.5 mmol) under continuous stirring for 20 min. Subsequently, the resulting cloudy solution was adjusted to pH 11.5−12.0 using NaOH (2.5 mL, 1 M), condensed to 30 mL at 70−75 °C for 5 h, filtered, and then transferred to a 50 mL beaker. The filtrate was allowed to evaporate slowly at room temperature. After several days, green block crystalline product was collected by filtration and washing with deionized water. Yield: 0.22 g (41.50%) for 1 based on K7HNb6O19·13H2O. Anal. Calcd for 1: H, 1.14; Na, 4.89; V, 4.81; Nb, 52.68. Found: H, 1.08, Na, 4.66; V, 4.59; Nb, 52.38. IR (KBr, disks): 867 (s), 671 (s), 540 (s) cm−1 (Figure S2 in the SI). Raman: 278 (s), 318 (ms), 363 (s), 480 (w), 540 (s), 845 (s), 897 (vs) (Figure S3 in the SI). Single-Crystal Study. The intensity data were collected on a Bruker APEX-II CCD diffractometer (Mo Kα, graphite-monochro-

TM refers to transition metal.

“big wheel” can be viewed as an oligomeric assembly of fundamental building blocks. This again reinforced the fact that the conventional aqueous method is a feasible approach to constructing high-nuclear POMs.18 B

DOI: 10.1021/acs.inorgchem.5b01936 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry mated, λ = 0.71073) for 1 at room temperature. Absorption corrections were applied using multiscan techniques. The structure was solved by the direct method of SHELXS-9720 and refined by the full-matrix least-squares method on F2 using the SHELXTL-97 crystallographic program21 within WINGX.22 CCDC-1418346 contains the supplementary crystallographic data for this paper. Data can be obtained free of charge from the Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/datarequest/cif. Photocatalytic Measurements. The photocatalytic reactions were performed in a Pyrex inner-irradiation-type reaction vessel with magnetic stirring at room temperature. The reactant solution was evacuated using N2 several times to ensure complete air removal and then irradiated using a 500 W mercury lamp, and the produced H2 was analyzed by a GC9800 instrument with a thermal conductivity detector and a 5 Å molecular sieve column (2 mm × 2 m) using N2 as carrier gas.

from the [VNb6O22]10− unit. There exist kinds of connectivities of sodium ions and these oxygen atoms, and Na−O bond distances (Angstroms) and connectivity modes in 1 are shown in Table S4. From the BVS (bond valence sum) calculations,24 we can assign the oxidation state of all V atoms as +4 in 1 (Table S1, Supporting Information). This result was further confirmed by the XPS spectrum (Figure S1 in the SI). The binding energy for a V 2p3/2 peak in 1 is observed at 516.25 eV, suggesting the existence of VIV ions.17e,25 The BVS values (Table S2 in the SI) of all terminal oxygen atoms except for water molecules in 1 are in the range 1.14−1.52, revealing that some oxygen atoms can be monoprotonated in polyniobate anion units on the basis of the previous studies by Nyman and Niu.13c,15d After several PXRD measurements, we found there is no good match between calculated and experimental XRD powder data (Figure S8), leading to the powder XRD not accurately representing the title compound. This case might result from the loss of solvent water in 1 during the course of testing. Electrospray Ionization Mass Spectrometry of 1. Additionally, we studied the stability of the {Nb48V8} cluster in solution via ESI-MS. The cluster has good solubility and easily gets solvation. The study revealed that the {Nb48V8} cluster was intact in solution, but a variable number of protons, sodium ions, and water molecules gave overlapping envelopes. The ESI-MS spectrum showed a series of signals of −5 and −6 charged ions that match calculated peak positions for {Nb48V8} adducts of protons, sodium cations, and water molecules (Figure 3 and Table S5 in the SI).

■

RESULTS AND DISCUSSION Synthesis. It is widely accepted that vanadium salts are well alkali soluble and active enough to undergo hydrolysis and condensation reactions.23 Moreover, as for vanadium, it could be a promising candidate for the construction of substituted PONbs, particularly owing to the similar ion radii (V(IV) 0.58 Å, Nb(V) 0.64 Å) and coordination number between V and Nb. In the synthesis of compound 1, vanadium chloride (VCl3) was utilized as a vanadium source to react with K7HNb6O19·13H2O in the alkaline aqueous solution. When we attempted to use VOSO4·xH2O (containing a V(IV) metal center) instead of VCl3, no analogous crystals are obtained by the route of the conventional aqueous method. It is found that the oxidation process of the V3+ ions plays a crucial role in the formation of 1. The presence of V4+ ions in 1 has been confirmed (Table S1 and Figure S1 in the SI), indicating that the starting V3+ ions were indeed oxidized by the atmosphere during the course of the reaction. Additionally, we tried to use different kinds of alkaline aqueous solution (e.g., KOH and TMAOH solution) to adjust the pH value, but no single crystals can be obtained. Structure Description of 1. Single-crystal X-ray diffraction analysis reveals that 1 crystallizes in the monoclinic space group P21/n, which exhibits a beautiful multiple-strand wheel structure (Figure 1c, Figure 2). The wheel structure of 1 is derived from eight identical [VNb6O22]10− building units, which are directly linked to each other through terminal oxygen atoms. Notably, this novel [VNb6O22]10− subunit is similar to the fundamental unit [Nb7O22]9− reported in the literature.13e,15d Formation of [VNb6O22]10− subunits should be a self-assembly process, where a single V atom is bonded to the three μ 2 -oxygen atoms of the adjacent Lindqvist-type hexaniobate anion [Nb6O19]8−. Owing to the higher coordination ability of the six-coordinate V atom, two additional terminal oxygen atoms from different [Nb6O19]8− anions are captured, forming the [VNb 6 O 2 2 ] 10 − subunit. The [Nb48V(IV)8(OH)30O130]18− polyanion is a wheel molecule, measuring approximately 2 nm across its circular face (Figure 2a) and approximately 1.2 nm across the side face (Figure 2b). In the [VNb6O22]10− unit, there are four types of oxygen atoms: one central oxygen atom (Oc), nine terminal oxygen atoms (Ot), nine bridging μ2-oxygen atoms, and three bridging μ3oxygen atoms. Additionally, all Nb and V atoms exhibit the octahedral configuration with the Nb−O bond distances in the range 1.751−2.441 Å, and the V−O bond distances in 1 vary from 1.602 to 2.256 Å, respectively. Besides, 18 Na+ cations are identified from single-crystal X-ray diffraction analysis. These Na+ cations are bonded to water oxygens or the oxygen atoms

Figure 3. ESI-MS of 1 in H2O.

UV−vis Diffuse Reflectance Spectra of 1. In an effort to explore the solid conductivity of 1, the UV−vis diffuse reflectance spectrum of the powder samples was measured to obtain its band gap (Eg), which was determined as the intersection point between the energy axis and the line extrapolated from the linear portion of the adsorption edge in a plot of the Kubelka−Munk function F against E.26 As shown in the Supporting Information (Figure S5−S6), the UV−vis absorption spectrum of 1 in solution displays a broad band from 600 to 700 nm (maximum absorption wavelength is 643 nm), which can be ascribed to d−d transitions for eight isolated V centers. Furthermore, the corresponding optical absorption associated with Eg can be assessed at 1.92 eV for 1 (Figure S7 in the SI), which indicates the presence of an optical band gap and the nature of the semiconductivity. Photocatalytic Properties. We also investigated the photocatalytic H2 evolution activity of 1. Experiments were carried out in a quartz cell with 180 mL of a 10% triethylamine C

DOI: 10.1021/acs.inorgchem.5b01936 Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

■

(TEA) aqueous solution (9/1 v/v) containing 100 mg of photocatalyst 1. The catalyst solution was irradiated under UV light from a 500 W mercury lamp. During the photocatalytic reaction an electron is first excited from the valence band (VB) O2p to the conduction band (CB) of the metal cation. Then the electron transfers from the metal to H2O to produce H2. TEA acts as a sacrificial electron donor, and the produced H2 was monitored by gas chromatography. As shown in Figure 4, for 2

Article

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.5b01936. Text, figures, and tables giving additional structural figures, XPRD, TGA, and UV−vis diffuse reflectance spectra (PDF) CIF files giving crystallographic data (CIF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was financially supported by the NSFC of China (nos. 21471027, 21171033, 21131001, 21222105), the National Key Basic Research Program of China (no. 2013CB834802), the Foundation for Author of National Excellent Doctoral Dissertation of P. R. China (FANEDD) (no. 201022), Changbai mountain scholars of Jilin Province, and FangWu distinguished young scholar of NENU.

Figure 4. Time course of H2 evolution under UV irradiation in 180 mL of 10% TEA aqueous solution: (a) in the presence of 100 mg of photocatalyst 1 and (b) in the absence of 1.

■

h the amount of the evolved H2 continued to rise, and the average H2 evolution rate during this period was 4687.0 μmol h−1 g−1. For compound 1, the total evolved H2 for 2 h was 960.5 μmol. This result confirms that compound 1 has the ability to photocatalyze H2 evolution from water under UV light. In addition, we compared the photocatalytic activity of 1 with those of related high-nuclear isopolyoxoniobates ({Nb24} and {Nb32} in our previous work13e); it is found that either the amount of total evolved H2 of 1 or the H2 evolution rate of 1 is lower than those of {Nb24} and {Nb32}. From our experience, we can infer that the photocatalytic H2 evolution activities of vanadium-substituted PONbs are inferior among the PONbs chemistry. To date, there have been no reports that introduce a significant amount of total evolved H2 of vanadium-substituted PONbs.

■

REFERENCES

(1) (a) Pope, M. T. Heteropoly and Isopoly Oxometalates; Springer: Berlin, 1983. (b) Cronin, L.; Müller, A. Chem. Soc. Rev. 2012, 41, 7333−7334. (c) Long, D. T.; Burkholder, E.; Cronin, L. Chem. Soc. Rev. 2007, 36, 105−121. (2) (a) Li, M.; Xu, C.; Ren, J. S.; Wang, E. B.; Qu, X. G. Chem. Commun. 2013, 49, 11394−11396. (b) Zheng, X. X.; Zhang, L.; Li, J. Y.; Luo, S. Z.; Cheng, J. P. Chem. Commun. 2011, 47, 12325−12327. (c) Nakagawa, Y.; Kamata, K.; Kotani, M.; Yamaguchi, K.; Mizuno, N. Angew. Chem., Int. Ed. 2005, 44, 5136−5141. (d) Nogueira, L. S.; Ribeiro, S.; Granadeiro, C. M.; Pereira, E.; Feio, G.; Cunha-Silva, L.; Balula, S. S. Dalton Trans. 2014, 43, 9518−9528. (e) Geng, J.; Li, M.; Ren, J. S.; Wang, E. B.; Qu, X. G. Angew. Chem. 2011, 123, 4270− 4274. (f) Fang, X. K.; Hansen, L.; Haso, F.; Yin, P. C.; Pandey, A.; Engelhardt, L.; Slowing, I.; Li, T.; Liu, T. B.; Luban, M.; Johnston, D. C. Angew. Chem., Int. Ed. 2013, 52, 10500−10504. (3) (a) Müller, A.; Krickemeyer, E.; Meyer, J.; Bögge, H.; Peters, F.; Plass, W.; Diemann, E.; Dillinger, S.; Nommenbruch, F.; Randerath, M.; Menke, C. Angew. Chem., Int. Ed. Engl. 1995, 34, 2122−2124. (b) Müller, A.; Shah, S. Q. N.; Bögge, H.; Schmidtmann, M. Nature 1999, 397, 48−50. (c) Müller, A.; Beckmann, E.; Bögge, H.; Schmidtmann, M.; Dress, A. Angew. Chem., Int. Ed. 2002, 41, 1162− 1166. (4) Taft, K. L.; Lippard, S. J. J. Am. Chem. Soc. 1990, 112, 9629− 9630. (5) (a) Beattie, J. K.; Hambley, T. W.; Klepetko, J. A.; Masters, A. F.; Turner, P. Chem. Commun. 1998, 45−46. (b) Brechin, E. K.; Cador, O.; Caneschi, A.; Cadiou, C.; Harris, S. G.; Parsons, S.; Vonci, M.; Winpenny, R. E. P. Chem. Commun. 2002, 1860−1861. (c) Eshel, M.; Bino, A.; Felner, I.; Johnston, D. C.; Luban, M.; Miller, L. L. Inorg. Chem. 2000, 39, 1376−1380. (d) Affronte, M.; Carretta, S.; Timco, G. A.; Winpenny, R. E. P. Chem. Commun. 2007, 1789−1797. (e) Mezei, G.; Baran; Raptis, P.; Raptis, R. G. Angew. Chem. 2004, 116, 584−587. (f) Murugesu, M.; Wernsdorfer, W.; Abboud, K. A.; Christou, G. Angew. Chem., Int. Ed. 2005, 44, 892−896. (g) Dearden, A. L.; Parsons, S.; Winpenny, R. E. P. Angew. Chem., Int. Ed. 2001, 40, 151−154. (h) King, P.; Stamatatos, T. C.; Abboud, K. A.; Christou, G. Angew. Chem. 2006, 118, 7539−7383. (i) Stamatatos, T. C.; Mukherjee, S.; Abboud, K. A.; Christou, G. Chem. Commun. 2009, 62−64.

CONCLUSION

In summary, we synthesized and structurally characterized a vanadium-containing polyoxoniobate 1 by a conventional aqueous method. Compound 1 possesses a unique multiplestrand wheel architecture, which is the first example in PONb chemistry. Furthermore, 1 represents the largest vanadoniobate cluster reported to date. The ESI-MS revealed that the {Nb48V8} cluster was intact in solution by showing a series of signals of −5 and −6 charged ions that match calculated peak positions for {Nb48V8} adducts. Moreover, the photocatalytic H2 evolution activity of 1 was investigated under UV light irradiation. The discovery of this novel vanadoniobate cluster not only provides new insights into the rational synthesis of polyoxoniobate chemistry under mild conditions but also enriches the structural diversity of transition-metal-substituted polyoxoniobates. D

DOI: 10.1021/acs.inorgchem.5b01936 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry (6) Tasiopoulos, A. T.; Vinslava, A.; Wernsdorfer, W.; Abboud, K. A.; Christou, G. Angew. Chem. 2004, 116, 2169−2173. (7) (a) Manoli, M.; Prescimone, A.; Bagai, R.; Mishra, A.; Murugesu, M.; Parsons, S.; Wernsdorfer, W.; Christou, G.; Brechin, E. K. Inorg. Chem. 2007, 46, 6968−6979. (b) Scott, R. T. W.; Milios, C. J.; Vinslava, A.; Lifford, D.; Parsons, S.; Wernsdorfer, W.; Christou, G.; Brechin, E. K. Dalton Trans. 2006, 3161−3163. (c) Stamatatos, T. C.; Abboud, K. A.; Wernsdorfer, W.; Christou, G. Angew. Chem., Int. Ed. 2008, 47, 6694−6698. (8) (a) Zhao, Y.; Zhu, G.; Liu, W.; Zou, Y.; Pang, W. Chem. Commun. 1999, 2219−2220. (b) Hoshiko, J. A.; Wang, G.; Ziller, J. W.; Yee, G. T.; Heyduk, A. F. Dalton Trans. 2008, 5712−5724. (c) Lee, J.; Gorun, S. M. Angew. Chem., Int. Ed. 2003, 42, 1512−1515. (d) Begum, M. S. A.; Seewald, O.; Flörke, U.; Henkel, G. Inorg. Chim. Acta 2008, 361, 1868−1874. (9) Manoli, M.; Inglis, R.; Manos, M. J.; Nastopoulos, V.; Wernsdorfer, W.; Brechin, E. K.; Tasiopoulos, A. J. Angew. Chem., Int. Ed. 2011, 50, 4441−4444. (10) (a) Xu, F.; Miras, H. N.; Scullion, R. A.; Long, D. L.; Thiel, J.; Cronin, L. Proc. Natl. Acad. Sci. U. S. A. 2012, 109, 11609−11612. (b) Scullion, R. A.; Surman, A. J.; Xu, F.; Mathieson, J. S.; Long, D. L.; Haso, F.; Liu, T.; Cronin, L. Angew. Chem., Int. Ed. 2014, 53, 10032− 10037. (11) (a) Kinnan, M. K.; Creasy, W. R.; Fullmer, L. B.; SchreuderGibson, H. L.; Nyman, M. Eur. J. Inorg. Chem. 2014, 2014, 2361− 2367. (b) Bonhomme, F.; Larentzos, J. P.; Alam, T. M.; Maginn, E. J.; Nyman, M. Inorg. Chem. 2005, 44, 1774−1785. (c) Besserguenev, A. V.; Dickman, M. H.; Pope, M. T. Inorg. Chem. 2001, 40, 2582−2586. (d) Russell, A. J.; Berberich, J. A.; Drevon, G. F.; Koepsel, R. R. Annu. Rev. Biomed. Eng. 2003, 5, 1−27. (e) Nyman, M.; Powers, C. R.; Bonhomme, F.; Alam, T. M.; Maginn, E. J.; Hobbs, D. T. Chem. Mater. 2008, 20, 2513−2521. (f) Zhang, Z. Y.; Lin, Q. P.; Kurunthu, D.; Wu, T.; Zuo, F.; Zheng, S. T.; Bardeen, C. J.; Bu, X. H.; Feng, P. Y. J. Am. Chem. Soc. 2011, 133, 6934−6937. (g) Wang, Z. L.; Tan, H. Q.; Chen, W. L.; Li, Y. G.; Wang, E. B. Dalton Trans. 2012, 41, 9882−9884. (h) Zhang, D. D.; Liang, Z. J.; Xie, S. Q.; Ma, P. T.; Zhang, C.; Wang, J. P.; Niu, J. Y. Inorg. Chem. 2014, 53, 9917−9922. (i) Abramov, P. A.; Vicent, C.; Kompankov, N. B.; Gushchin, A. L.; Sokolov, M. N. Chem. Commun. 2015, 51, 4021−4023. (12) Lindqvist, I. Ark. Kemi 1953, 5, 247−250. (13) (a) Graeber, E. J.; Morosin, B. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1977, 33, 2137−2143. (b) Maekawa, M.; Ozawa, Y.; Yagasaki, A. Inorg. Chem. 2006, 45, 9608−9069. (c) Bontchev, R. P.; Nyman, M. Angew. Chem., Int. Ed. 2006, 45, 6670−6672. (d) Tsunashima, R.; Long, D. L.; Miras, H. N.; Gabb, D.; Pradeep, C. P.; Cronin, L. Angew. Chem., Int. Ed. 2010, 49, 113−116. (e) Huang, P.; Qin, C.; Su, Z. M.; Xing, Y.; Wang, X. L.; Shao, K. Z.; Lan, Y. Q.; Wang, E. B. J. Am. Chem. Soc. 2012, 134, 14004−14010. (14) (a) Nyman, M.; Bonhomme, F.; Alam, T. M.; Rodriguez, M. A.; Cherry, B. R.; Krumhansl, J. L.; Nenoff, T. M.; Sattler, A. M. Science 2002, 297, 996−998. (b) Nyman, M.; Celestian, A. J.; Parise, J. B.; Holland, G. P.; Alam, T. M. Inorg. Chem. 2006, 45, 1043−1052. (c) Anderson, T. M.; Alam, T. M.; Rodriguez, M. A.; Bixler, J. N.; Xu, W. Q.; Parise, J. B.; Nyman, M. Inorg. Chem. 2008, 47, 7834−7839. (d) Hou, Y.; Zakharov, L. N.; Nyman, M. J. Am. Chem. Soc. 2013, 135, 16651−16657. (e) Son, J. H.; Wang, J.; Osterloh, F. E.; Yu, P.; Casey, W. H. Chem. Commun. 2014, 50, 836−838. (f) Geng, Q. H.; Liu, Q. S.; Ma, P. T.; Wang, J. P.; Niu, J. Y. Dalton Trans. 2014, 43, 9843−9846. (15) (a) Son, J. H.; Ohlin, C. A.; Casey, W. H. Dalton Trans. 2012, 41, 12674−12677. (b) Son, J. H.; Ohlin, C. A.; Casey, W. H. Dalton Trans. 2013, 42, 7529−7533. (c) Son, J. H.; Casey, W. H. Dalton Trans. 2013, 42, 13339−13342. (d) Niu, J. Y.; Ma, P. T.; Niu, H. Y.; Li, J.; Zhao, J. W.; Song, Y.; Wang, J. P. Chem. - Eur. J. 2007, 13, 8739− 8748. (e) Niu, J. Y.; Chen, G.; Zhao, J. W.; Ma, P. T.; Li, S. Z.; Wang, J. P.; Li, M. X.; Bai, Y.; Ji, B. S. Chem. - Eur. J. 2010, 16, 7082−7086. (f) Niu, J. Y.; Li, F.; Zhao, J. W.; Ma, P. T.; Zhang, D. D.; Bassil, B.; Kortz, U.; Wang, J. P. Chem. - Eur. J. 2014, 20, 9852−9857. (g) Liang, Z. J.; Zhang, D. D.; Ma, P. T.; Niu, J. Y.; Wang, J. P. Chem. - Eur. J. 2015, 21, 8380−8383.

(16) (a) Nyman, M.; Criscenti, L. J.; Bonhomme, F.; Rodriguez, M. A.; Cygan, R. T. J. Solid State Chem. 2003, 176, 111−119. (b) Ohlin, C. A.; Villa, E. M.; Fettinger, J. C.; Casey, W. H. Angew. Chem. 2008, 120, 5716−5718. (c) Ohlin, C. A.; Villa, E. M.; Fettinger, J. C.; Casey, W. H. Dalton Trans. 2009, 2677−2678. (17) (a) Guo, G. L.; Xu, Y. Q.; Cao, J.; Hu, C. W. Chem. Commun. 2011, 47, 9411−9413. (b) Guo, G. L.; Xu, Y. Q.; Cao, J.; Hu, C. W. Chem. - Eur. J. 2012, 18, 3493−3497. (c) Huang, P.; Qin, C.; Wang, X. L.; Sun, C. Y.; Yang, G. S.; Shao, K. Z.; Jiao, Y. Q.; Zhou, K.; Su, Z. M. Chem. Commun. 2012, 48, 103−105. (d) Son, J. H.; Ohlin, C. A.; Johnson, R. L.; Yu, P.; Casey, W. H. Chem. - Eur. J. 2013, 19, 5191− 5197. (e) Shen, J. Q.; Zhang, Y.; Zhang, Z. M.; Li, Y. G.; Gao, Y. Q.; Wang, E. B. Chem. Commun. 2014, 50, 6017−6019. (18) (a) Xuan, W. M.; Surman, A. J.; Miras, H. N.; Long, D. L.; Cronin, L. J. Am. Chem. Soc. 2014, 136, 14114−14120. (b) Cronin, L.; Beugholt, C.; Krickemeyer, E.; Schmidtmann, M.; Bögge, H.; Kögerler, P.; Luong, T. K. K.; Müller, A. Angew. Chem. 2002, 114, 2929−2932. (c) de la Oliva, A. R.; Sans, V.; Miras, H. N.; Yan, J.; Zang, H. Y.; Richmond, C. J.; Long, D. L.; Cronin, L. Angew. Chem., Int. Ed. 2012, 51, 12759−12762. (d) Müller, A.; Gouzerh, P. Chem. Soc. Rev. 2012, 41, 7431−7463. (19) Filowitz, M.; Ho, R. K. C.; Klemperer, W. G.; Shum, W. Inorg. Chem. 1979, 18, 93−103. (20) Sheldrick, G. M. SHELXS-97: Programs for X-ray Crystal Structure Solution; University of Göttingen: Göttingen, Germany, 1997. (21) Sheldrick, G. M. SHELXL-97: Programs for X-ray Crystal Structure Refinement; University of Göttingen: Göttingen, Germany, 1997. (22) Farrugia, L. J. WINGX, A Windows Program for Crystal Structure Analysis; University of Glasgow: Glasgow, UK, 1988. (23) Nyman, M. Dalton Trans. 2011, 40, 8049−8058. (24) Brown, I. D.; Altermatt, D. Acta Crystallogr., Sect. B: Struct. Sci. 1985, 41, 244−247. (25) Leus, K.; Couck, S.; Vandichel, M.; Vanhaelewyn, G.; Liu, Y. Y.; Marin, G. B.; Van Driessche, I.; Depla, D.; Waroquier, M.; Van Speybroeck, V.; Denayer, J. F. M.; Van Der Voort, P. Phys. Chem. Chem. Phys. 2012, 14, 15562−15570. (26) Pankove, J. I. Optical Processes in Semiconductors; Prentice-Hall: Englewood Cliffs, NJ, 1971; p 34.

E

DOI: 10.1021/acs.inorgchem.5b01936 Inorg. Chem. XXXX, XXX, XXX−XXX