Stable Photoinduced Separated Charge State in Viologen

COMMUNICATION pubs.acs.org/crystal

Stable Photoinduced Separated Charge State in Viologen Halometallates: Some Key Parameters Nicolas Leblanc, Magali Allain, Nicolas Mercier,* and Lionel Sanguinet MOLTECH-Anjou, UMR-CNRS 6200, Universit
e d’Angers—2 Bd Lavoisier, 49045 Angers, France

bS Supporting Information ABSTRACT: With the aim to define key parameters causing the photochromic properties of (MV)[Bi2Cl8] and (MV)4[Bi6Cl26] (MV2þ, methylviologen; 1,10 -dimethyl-4,40 -bipyridinium), the effects of substituting Bi by Sb, Cl by Br, or MV2þ by MOV2þ (1,10 -dimethoxy-4,40 -bipyridinium) or MeMOV2þ (1-methyl-10 methoxy-4,40 -bipyridinium) on the photoinduced charge transfer properties of such viologen halometallates are explored. It appears that only salts containing chlorobismuthate anions undergo a color change upon UV irradiation and that the nature of viologen entities has a key role in the process. We also suggest that a key parameter for observing the stable photoinduced separated charge state in chlorobismuthate viologen hybrids is a high chloride/viologen ratio, rather than the size of the anionic oligomer, as observed in the previously reported unique series (MV)(2nþ2)/2[Bi2nCl8nþ2].

ecently, a methylviologen (1,10 -dimethyl-4,40 -bipyridinium: MV2þ) chlorobismuthate, namely (MV)[Bi(III)2Cl8], with impressive photochomic properties, has been reported.1 The color change upon UV-irradiation, from yellow to black, is explained by the presence of radical cation MV•þ in the irradiated phase, as the result of the photoinduced charge transfer from the inorganic anion to the MV2þ entities. Interestingly, this separatedcharge state is stable, and the initial compound can be recovered by heating the irradiated sample at 130
C. Photochromism, or longlived charge separation, is an interesting phenomenon and can lead to a variety of applications, ranging from clean energy to photo- or electrochromic devices.2,3 The strong electron acceptor methylviologen dication (MV2þ) has afforded a great number of charge transfer or photoinduced charge transfer complexes.311 The transformation of MV2þ to its reduced form (MV•þ) with blue color, while frequently observed in solution, can also be observed under the solid state.610 Weak interactions between viologen and either the host (Nþ(viologen) 3 3 3 X (element of the host)) through σπ interactions4 or neutral molecules through ππ interactions7 (case of hybrids also incorporating neutral guest molecules which form with the viologen dications, so-called CT complex guests) seem to be necessary to observe charge transfer or photoinduced charge transfer; however, the full understanding of the associated photochromism phenomenom remains difficult to elucidate. Recently, we reported two chlorobismuthate hybrids (MV)(2nþ2)/2[Bi2nCl8nþ2] (n = 2, n = 3) whose structures can be related to the structure of (MV)[Bi2Cl8] (n = ¥) by the dimensional reduction concept.12 In particular, the inorganic oligomers consisting of n = 2 or 3 subunits, each formed by two edge-shared BiCl6 octahedra, can be considered as part of the 1D oligomer of the mother structure. And we showed that the photochromic

R

r 2011 American Chemical Society

properties upon irradiation depend on the oligomer size, with a gradually increase of color change as the oligomer size increases.13 Searching for other key parameters influencing the photochromic properties of these methylviologen chlorobismuthates, we aimed to substitute Bi(III) by Sb(III), Cl by Br, and MV2þ by other nonbulky viologens. We report in this communication on the synthesis, structural characterization, and UV irradiation investigations of six new viologen halometalates: (MOV)2[Bi2Cl10] (1) (MOV2þ = 1,10 -diMethOxy-4,40 -bipyridinium), (MOV)2[Bi2Br10] (2), and (MeMOV)2[Bi2Cl10] (3) (MeMOV2þ = 1-Methyl-10 MethOxy-4,40 -bipyridinium), whose inorganic anion formed by two edge-shared BiX6 octahedra corresponds to the n = 1 member of the [Bi2nX8nþ2] series, (MV)[Sb2Cl8] (4) and (MOV)[Sb2Cl8] (5), whose structures are roughly similar to the one of (MV)[Bi2Cl8], and (MV)[BiCl5] (6), built up from infinite chains of corner trans-connected BiCl6 octahedra. Crystals of 1, 2, 3, 4, and 5 were synthesized by using a slow liquid-gaz diffusion method: a pillbox containing the viologen salt ((MOV)(BF4)2, (MeMOV)(BF4)2, or (MV)Cl2), the metal halide salt, and corresponding HX (X = Cl, Br) dissolved in H2O is put in a sealed jar filled with acetonitrile. After a few hours, crystals are formed (Supporting Information).14 Crystals of 6 were synthesized under solvothermal conditions from BiIIICl3, 4,40 -bipyridine, and concentrated HCl in methanol. The in situ formation of MV2þ dications results from the reaction of 4,40 -bipyridine, methanol, and HCl.15 The synthesis of starting materials (MOV)(BF4)2 and (MeMOV)(BF4)2 has been prepared according to the literature16 (Supporting Information). Received: March 15, 2011 Revised: April 8, 2011 Published: April 18, 2011 2064

dx.doi.org/10.1021/cg2003244 | Cryst. Growth Des. 2011, 11, 2064–2069

Crystal Growth & Design

COMMUNICATION

Figure 1. (a) UVvis spectra in the 250880 nm range and photos of crystals of (MOV)2[Bi2Cl10] (1) before (full line) and after (dashed line) UV irradiation; (b) photo of an irradiated crystal of 1 heated at 120
C.

Irradiation of crystallized samples 16 by sunlight or 366 nm UV radiation (150 W Hg lamp) only results in a great color change, from yellow to black for (MOV)2[Bi2Cl10] (1) and to a slight darkening of (MeMOV)[Bi2Cl10] (3) (the permanent colors are obtained after approximately 2 h of irradiation at 366 nm). Obviously, the change from yellowish to black for crystals (1) takes place at or near the surface of crystals, as nicely highlighted by the heating of crystals (120
C), which involves the cleavage of the irradiated layered parts (Figure 1b). This photoinduced color change is probably due to charge transfer from the inorganic anion to the organic cation, resulting in a viologen radical cation. For 1, this is confirmed both by the in situ EPR measurement showing the growth of a signal with a g value of 2.003 (Supporting Information), as observed in the irradiated compound (MV)[Bi2Cl8],1 and by the UVvis spectroscopy, which reveals a broad absorption band in the visible region, typical of a V•þ radical cation (Figure 1a).3 While the photoinduced process is partially reversible by heating the samples of (MV)[Bi2Cl8]1 or (MV)4[Bi6Cl26]13 (and becomes irreversible after a few cycles), the phenomenon is not reversible from the first heating of samples 1 or 3. This raises the question: what is the nature of the anionic chlorobismuthate donor after irradiation? This has not been answered by Guo et al. about the (MV)[Bi2Cl8] compound,1 also. The fact that the photoreaction takes place at or near the surface renders a X-ray diffraction study difficult. Moreover, as reported in other photochromic viologen solids,8b only a small percentage of viologen entities may have been transformed on irradiation. Anyway, it will remain a great challenge in the future to characterize the anionic donor entities which are present in the irradiated phases in order to understand either the reversibility, the partially reversibility, or the irreversibility of the phenomenon in such compounds. The asymmetric unit of the crystal structures of 1, 2, and 317 contains one independent viologen molecule and half a Bi2X10 (X = Cl, Br) anionic cluster. The crystal structures of the MOV compounds (1, X = Cl) and (2, X = Br (see the Supporting Information)) are isomorphous. The views along a of structures

1 and 3 show apparently similar layers parallel to (a,b) which consist of molecules sandwiched by the inorganic units. However, a clear shift of consecutive layers is observed in 3 (Figure 2). It is interesting to note that the Bi2Cl10 cluster built from two edge-shared BiCl6 octahedra is the first member of the series of inorganic networks with the general formula [Bi2nCl8nþ2], with n = 2, n = 3, and n = ¥ being crystallized with the methylviologen dication as (MV)3[Bi4Cl18],13 (MV)4[Bi6Cl18],13 and (MV)2[Bi2Cl8],1 respectively. In structures 1 and 2, the MOV2þ molecular entities are bent with an angle between lines [N2C10] and [N1C4] of 6.4
, and a dihedral angle between the two pyridinium cycles of 11.0
for 1 (Figure 2) or 9.0
for (2) (Supporting Information). In contrast, the bipyridinium core of the MeMOV2þ entities is planar in the structure of 3 (Figure 2). In addition, we notice in all the structures 1, 2, and 3 a shift of O atoms out of the pyridinium planes: in 1, the angles between lines [N1O1] or [N2O2] and the pyridinium planes containing N1, C4 or N2, C10 are 7.6
and 5.2
, respectively; in 3, the angle between line [N1O1] and the pyridinium plane containing N1, C4 is 4.6
. Two adjacent molecules are faced-forming dimers surrounded by four inorganic clusters (Figure 3). Weak O 3 3 3 Nþ intradimer contacts of 3.279(1) Å (1) or 3.327(1) Å (2) are observed in MOV2þ compounds, while the shortest Nþ 3 3 3 O distance is 3.650(2) Å in 3. Moreover, some differences in weak bonding at the interface are also observed between the MOV2þ and MeMOV2þ based structures. Particularly, short Nþ 3 3 3 Cl contacts, with equatorial Cl atoms being almost perpendicular to the pyridinium ring at the nitrogen atom, are observed in 1 (d = 3.446(9) Å and 3.467(9) Å), as observed in photochromic chlorobismuthate viologen materials,1,13 while longer Nþ 3 3 3 Cl contacts involving equatorial and apical Cl atoms are present in 3 (d = 3.690(8) Å and 3.695(9) Å, Figure 3). We also notice in 3 that the angle between the pyridinium ring and the “Nþ 3 3 3 Cl” direction moves away from 90
. The MV2þ and MOV2þ viologens afford two 1D chloroantimonate hybrids, (MV)[Sb2Cl8] (4), whose structure was already determined,18 and (MOV)[Sb2Cl8] (5).17 Their structural layout 2065

dx.doi.org/10.1021/cg2003244 |Cryst. Growth Des. 2011, 11, 2064–2069

Crystal Growth & Design

COMMUNICATION

Figure 2. Crystal structures of (MOV)2[Bi2Cl10] (1) (a) and (MeMOV)2[Bi2Cl10] (3) (b): general view (up) and viologen dications (down).

Figure 3. Part of the structures of (MOV)2[Bi2Cl10] (1) (a) and (MeMOV)2[Bi2Cl10] (3) (b) showing contacts (dashed lines) between molecules (Nþ 3 3 3 O in 1) and at the organicinorganic interface (H 3 3 3 Cl and Nþ 3 3 3 Cl).

and the one of the photochromic (MV)[Bi2Cl8] are close to each other. In all structures, planar viologen molecules are sandwiched between 1D inorganic networks, forming sheets (Figure 4) shifted to each other along the b axis (4) or c axis (5) in such a way that a chessboard arrangement is defined when the structures are viewed along the chain axis. As observed in (MV)[Bi2Cl8], there are short Nþ 3 3 3 Cl contacts (4, d = 3.410(2) Å and 3.500(2) Å; 5, d = 3.429(2) Å and 3.525(2) Å), and in 4 all molecular planes are parallel to each other (Figure 4a). In contrast, the planes of molecules belonging to consecutive layers along the c axis in 5 are almost perpendicular to each other (Figure 4b). It is worth noting that these features are correlated to the nature of the inorganic network. These last are shown in Figure 5 for (MV)[Bi2Cl8] as well as for 4 and 5. First, it is easy to notice that only one type of BiCl bond distance (d = 2.763(1) Å) is observed along the chain axis in (MV)[Bi2Cl8], while an alternation of short and long SbCl distances occurs in 4, d = 2.382(1) Å and d = 3.313(1) Å, and in 5, d = 2.379(2) Å and d = 3.347(2) Å. Such a distorted octahedron reveals the 5s2 Sb(III) lone pair stereoactivity, and we notice that the geometrical characteristics

of SbCl6 polyhedra (1 strong, 1 weak, and 4 intermediate bonds) are well corresponding to one of the configurations described in Brown’s model,19 indicating that the lone pair orbital extends along the direction opposite to the short SbCl bond. Moreover, these different geometries around Bi3þ and Sb3þ well correspond to general trends that heavier metal centers favor regular octahedra.20 Second, the resulting polar chains are related by a symmetry center leading to an apolar double chain in 4, while they are adjacent in 5, thus building polar double chains (Figure 5). Finally, we notice that the Nþ 3 3 3 Cl contacts in 5 are all opposite to the short SbCl bond distance previously defined (Figure 4b). In the Bi(III)/Cl/MV2þ system, we obtained a fourth kind of phase, (MV)[BiCl5] (6).17 Contrary to the three first known compounds whose inorganic networks belong to the [Bi2nCl8nþ2] series (n = 2,13 n = 3,13 n = ¥),1 the structure of 6 has a BiCl5 inorganic network of trans-connected BiCl6 octahedra which can be considered as the n = ¥ member of the [BinCl5nþ1] series. The structure of 6 is the isotype of the room temperature phase of (MV)[BiBr5].21 The inorganic chains which extend along the a axis are surrounded by the methylviologen cations. 2066

dx.doi.org/10.1021/cg2003244 |Cryst. Growth Des. 2011, 11, 2064–2069

Crystal Growth & Design

COMMUNICATION

Figure 4. Part of structures of (MV)[Sb2Cl8] (4) (a) and (MOV)[Sb2Cl8] (5) (b) showing Nþ 3 3 3 Cl contacts (dashed lines).

Figure 5. Part of the [M2Cl8] 1D network in (MV)[Bi2Cl8] (a), (MV)[Sb2Cl8] (4) (b), and (MOV)[Sb2Cl8] (5).

Interestingly, 6 has structural features similar to those of the photochromic (MV)[Bi2Cl8]: planar MV2þ entities, stereoinactivity of the 6s2 Bi(III) lone pair with equal BiBrbridging bond distances (d = 2.926(1) Å), and same kind of H 3 3 3 Cl and Nþ 3 3 3 Cl contacts at the organicinorganic interface (Figure 6). Four kinds of viologen chlorobismuthates whose inorganic network belong to the [Bi2nCl8nþ2] series are known: the 1D chain (n = ¥) and the n = 3 and n = 2 oligomers have been crystallized with the methylviologen dication (MV2þ), while the n = 1 oligomer is crystallized with both the MOV2þ and MeMOV2þ entities. In methylviologen hybrids, the photochromic properties depend on the size of the oligomer, with a gradually decrease of color change as the oligomer size decreases, with the n = 2 (MV)3[Bi4Cl18] yellow hybrid remaining almost unchanged when irradiated by UV irradiation.13 In this context, it is interesting to note that (MOV)2[Bi2Cl10] (1), containing the

Figure 6. Part of the structure of (MV)[BiCl5] (6) showing Nþ 3 3 3 Cl and H 3 3 3 Cl contacts (dashed lines). 2067

dx.doi.org/10.1021/cg2003244 |Cryst. Growth Des. 2011, 11, 2064–2069

Crystal Growth & Design smallest inorganic cluster of the series, undergoes a great color change upon irradiation (due to photoinduced charge transfer). Taking account that the surrounding of the MOV2þ dications in 1 is comparable to that of MV2þ in (MV)3[Bi4Cl18] (and in the photochromic n = ¥ and n = 3 oligomer based salts), it appears that the nature of viologen entities, here a better electron acceptor viologen (MOV2þ) than MV•þ,3,22 has a key role in the photoinduced charge transfer properties. This situation has similarities with the one observed by Nishikiori et al. for charge transfer complexes of MV2þ and neutral donor molecules included in a polycyano-polycadmate host where the photochromism due to the photoinduced charge transfer from the neutral molecule to MV2þ depends on the nature of donors (characterized by their ionization potential).7 In the case of hybrid 3, based on the MeMOV2þ entity, which has electron acceptor behavior a little worse than the one of MOV2þ,22 it also undergoes a photoinduced charge transfer, but with a color change much less developed than that for 1. This could also be explained by the geometry of the Nþ 3 3 3 Cl contacts, which differs from 1 and photochromic methylviologen chlorobismuthates.1,13 Changing the nature of the halide X, by using Br instead of Cl in the MV2þ/Bi(III)/X system, did not allow us to obtain any hybrid whose bromobismuthate anion belongs to the [Bi2nX8nþ2] series. However, in the MOV2þ/Bi/Br system, compound 2, based on the smallest cluster of the series, Bi2Br104, is obtained. In contrast with the isotype compound (1) based on Bi2Cl104 clusters, 2 does not undergo a color change under UV irradiation, showing that the presence of Cl is necessary in the photoinduced process. This may be correlated to the ability of chloride anions to give more stable radical entities compared to heavier halide anions.23 Substituting Bi3þ by Sb3þ in our system leads to the 1D compounds 4 and 5, whose band gaps are similar, and the structures are almost isomorphous to the photochromic (MV)[Bi2Cl8]. The main difference comes from the stereoactivity of the Sb(III) electronic lone pair, resulting in an alternation of short and long SbCl bond distances along the chain axis. The fact that any of these viologen chloroantimonates display a stable separated charge state after UV irradiation clearly shows that the nature of the group 15 metal is a key parameter for observing this phenomenon in viologen chlorometallates. The case of (MV)[BiCl5] is interesting because its structure has several features similar to those of the photochromic (MV)[Bi2Cl8]; particularly, the same kinds of interactions at the organicinorganic interface are observed. However, this 1D chlorobismuthate compound does not undergo any color change upon UV irradiation. This result shows that the dimensionality of the chlorobismuthate network, if clearly related to the photochromic properties in the case of the [Bi2nCl8nþ2] series, is not a key parameter. The stable charge separated state means that viologen radical cations, on one hand, and an electron deficient anionic cluster, on the other hand, are stabilized in the solid state. Finally, one key parameter could be a high chloride/viologen ratio, which would mean that the transfer of one electron from the inorganic anion to one MV2þ entity would be all the more efficient, since the inorganic anion is big. And in fact, we observe for the methylviologen series that the color change upon UV irradiation gradually decreases as the Cl/MV ratio decreases: Cl/MV = 8, 6.5, 6, and 5 in (MV)[Bi2Cl8], (MV)4[Bi6Cl26], (MV)3[Bi4Cl18], and (MV)[BiCl5], respectively. All these first results open a route to achieve new photochromic materials, particularly the selection of suitable viologen,

COMMUNICATION

and the stabilization of viologen chlorobismuthates with condensed inorganic networks should be good strategies. Works in these directions are in progress.

’ ASSOCIATED CONTENT

bS

Supporting Information. Details of synthesis procedures, complete crystal data, X-ray powder diffraction patterns, and UVvis spectra of all six compounds 16. EPR spectrum of the in situ irradiated phase 1. This material is available free of charge via the Internet at http://pubs.acs.org.

’ AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected]. Fax: 33.(2).41.73.54.05. Telephone: 33.(2).41.73.50.83.

’ ACKNOWLEDGMENT We thank Alain Mari from the LCC laboratory of Toulouse (France) for electron paramagnetic resonance (EPR) measurements. ’ REFERENCES (1) Xu, G.; Guo, G.-C.; Wang, M.; Zhang, Z.; Chen, W.; Huang, J. Angew. Chem., Int. Ed. 2007, 46, 3249. (2) Wang, M.-S.; Xu, G.; Zhang, Z.-J.; Guo, G.-C. Chem. Commun. 2010, 46, 361. (3) Monk, P. M. S. The Viologens: Physicochemical Properties, Synthesis, and Application of the Salt of 4,40 -Bipyridine; Wiley: New York, 1998. (4) Prout, C. K.; Wright, J. D. Angew. Chem., Int. Ed. 1968, 7, 659. (5) (a) Yoshikawa, H.; Nishikiori, S.; Ishida, T. J. Phys. Chem. B 2003, 107, 9261. (b) Yoshikawa, H.; Nishikiori, S.; Suwinska, K.; Luboradzki, T.; Lipkowski, J. Chem. Commun. 2001, 1398. (6) (a) Park, Y. S.; Um, S. Y.; Yoon, K. B. J. Am. Chem. Soc. 1999, 121, 3193. (b) Clennan, E. L. Coord. Chem. Rev. 2004, 248, 477. (c) Alvaro, M.; Garcia, H.; Garcia, S.; Marquez, F.; Scaiano, J. C. J. Phys. Chem. B 1997, 101, 3043. (7) Yoshikawa, H.; Nishikiori, S. Dalton Trans. 2005, 3056. (8) (a) Yoshikawa, H.; Nishikiori, S. Chem. Lett. 2000, 142. (b) Yoshikawa, H.; Nishikiori, S.; Watanabe, T.; Ishida, T.; Watanabe, G.; Murakami, M.; Suwinska, K.; Luboradzki, T.; Lipkowski, J. J. Chem. Soc., Dalton Trans. 2002, 1907. (9) Vermeulen, L. A.; Snover, J. L.; Sapochak, L. S.; Thomson, M. E. J. Am. Chem. Soc. 1993, 115, 11767. (10) Abouelwafa, A. S.; Mereacre, V.; Balaban, T. S.; Anson, C. E.; Powell, A. K. CrystEngComm 2010, 12, 94. (11) (a) Chen, Y.; Yang, Z.; Guo, C.-X.; Ni, C.-Y.; Ren, Z.-G.; Li, H.-X.; Lang, J.-P. Eur. J. Inorg. Chem. 2010, 5326. (b) Chen, Y.; Yang, Z.; Guo, C.-X.; Ni, C.-Y.; Li, H.-X.; Ren, Z.-G.; Lang, J.-P. CrystEngComm 2011, 13, 243. (c) Tang, Z.; Guloy, A. M. J. Am. Chem. Soc. 1999, 121, 452. (d) Tang, Z.; Litvinchuk, A. P.; Lee, H.-G.; Guloy, A. M. Inorg. Chem. 1998, 37, 4752. (12) (a) Tulsky, E.; Long, J. Chem. Mater. 2001, 13, 1149. (b) Mercier, N.; Louvain, N.; Bi, W. CrystEngComm 2009, 11, 720. (13) Leblanc, N.; Bi, W.; Mercier, N.; Auban-Senzier, P.; Pasquier, C. Inorg. Chem. 2010, 49, 5824. (14) Compounds 1, 2, 4, and 5 are obtained as pure phases, while 3 is the minor phase, with the main phase being a crystallized powder which has not been characterized. (15) Hou, J.-J.; Guo, C.-H.; Zhang, X.-M. Inorg. Chim. Acta 1996, 359, 39. (16) (a) Wang, D.; Crowe, W. E.; Strongin, R. M.; Sibrian-Vazquez, M. Chem. Commun. 2009, 1876–1878. (b) Fielden, R.; Summers, L. A. 2068

dx.doi.org/10.1021/cg2003244 |Cryst. Growth Des. 2011, 11, 2064–2069

Crystal Growth & Design

COMMUNICATION

J. Heterocycl. Chem. 1974, 11, 299–301. (c) Brunner, H.; St€oriko, R.; Rominger, F. Eur. J. Inorg. Chem. 1998, 771–781. (17) Data collections were carried out on a Bruker Kappa CCD diffractometer using graphite-monochromated Mo KR radiation (λ = 0.71073 Å). The structures were solved by direct methods and refined by full-matrix least-squares routines against F2 using the Shelxl97 package. The hydrogen atoms were treated with a riding model. In 5, a residue peak higher than the background appeared along the SbClbridging direction at the end of refinements. Then, a statistical disorder of the bridging Cl was applied, leading to occupation rates of 0.977 and 0.023 for Cl1A and Cl1B, respectively. Cl1B was refined isotropically. (MOV)2[Bi2Cl10] (1) (C24H28Bi2Cl10N4O4): M = 1209.0, trilinic P1, a = 8.982(1) Å, b = 9.087(1) Å, c = 12.535(2) Å, R = 101.27(1)
, β = 110.41(1)
, γ = 95.29(1)
, V = 925.9(2) Å3, Z = 1, Dcalc 2.168, T = 293 K, μ = 10.25 mm1, 2θmax = 60
, 21266 measured reflns, 5384 unique reflns (R(int) = 0.096), R(F) = 0.056 (3606 reflns, I/σ(I) > 2, 201 parameters), wR2(F2) = 0.118 (all data). (MOV)2[Bi2Br10] (2) (C24H28Bi2Br10N4O4): M = 1653.6, trilinic P1, a = 9.259(1) Å, b = 9.403(1) Å, c = 12.710(2) Å, R = 101.80(1)
, β = 110.52(1)
, γ = 95.04(1)
, V = 999.1(2) Å3, Z = 1, Dcalc 2.748, T = 293 K, μ = 18.83 mm1, 2θmax = 60
, 22599 measured reflns, 5758 unique reflns (R(int) = 0.067), R(F) = 0.045 (3881 reflns, I/σ(I) > 2, 201 parameters), wR2(F2) = 0.099 (all data). (MeMOV)2[Bi2Cl10] (3) (C24H28Bi2Cl10N4O2): M = 1177.0, triclinic P1, a = 7.801(1) Å, b = 10.490(1) Å, c = 12.691(2) Å, R = 71.25(1)
, β = 72.55(1)
, γ = 85.43(1)
, V = 938.0(2) Å3, Z = 1, Dcalc 2.084, T = 293 K, μ = 10.11 mm1, 2θmax = 60
, 25367 measured reflns, 5390 unique reflns (R(int) = 0.090), R(F) = 0.053 (3845 reflns, I/σ(I) > 2, 192 parameters), wR2(F2) = 0.096 (all data). (MV)[Sb2Cl8] (4) (C12H14Cl8N2Sb2): M = 713.4, trilinic P1, a = 5.6935(5) Å, b = 9.3611(4) Å, c = 11.7186(8) Å, R = 66.70(1)
, β = 89.36(1)
, γ = 78.69(1)
, V = 561.0(1) Å3, Z = 1, Dcalc 2.112, T = 293 K, μ = 3.36 mm1, 2θmax = 70
, 24452 measured reflns, 4904 unique reflns (R(int) = 0.032), R(F) = 0.035 (4254 reflns, I/σ(I) > 2, 110 parameters), wR2(F2) = 0.091 (all data). (MOV)[Sb2Cl8] (5) (C12H14Cl8N2O2Sb2): M = 745.35, monoclinic P2/n, a = 12.0791(9) Å, b = 5.7189(5) Å, c = 18.1444(10) Å, β = 109.12(1)
, V = 1184.2(1) Å3, Z = 2, Dcalc 2.090, T = 293 K, μ = 3.19 mm1, 2θmax = 60
, 17289 measured reflns, 3469 unique reflns (R(int) = 0.052), R(F) = 0.041 (2371 reflns, I/σ(I) > 2, 124 parameters), wR2(F2) = 0.139 (all data). (MV)[BiCl5] (6) (C12H14Bi1Cl5N2): M = 572.48, monoclinic P21/c, a = 5.5376(2) Å, b = 16.1358(6) Å, c = 10.0789(4) Å, β = 100.89(1)
, V = 884.38(6) Å3, Z = 2, Dcalc 2.15, T = 293 K, μ = 10.71 mm1, 2θmax = 60
, 16174 measured reflns, 2307 unique reflns (R(int) = 0.031), R(F) = 0.021 (1702 reflns, I/σ(I) > 2, 95 parameters), wR2(F2) = 0.038 (all data). (18) Marsh, R. E. Acta Crystallogr., B 2005, 61, 359. (19) Brown, D. J. J. Solid State Chem. 1974, 11, 214. (20) (a) Wheeler, R. A.; Kumar, V. P. N. J. Am. Chem. Soc. 1992, 114, 4776. (b) Atanasov, M.; Reinen, D. J. Am. Chem. Soc. 2002, 124, 6693. (21) Bi, W.; Leblanc, N.; Mercier, N.; Auban-Senzier, P.; Pasquier, C. Chem. Mater. 2009, 21, 4099. (22) The first reduction potential of MV2þ, MeMOV2þ, and MOV2þ derivatives, respectively, at Epc = 0.922, 0.687 and 0.650 V vs Fc/ FcþC, was determined by cyclic voltammetry (CV). CV was performed in a three-electrode cell equipped with a platinum millielectrode, a platinum wire counter-electrode, and a silver wire used as a quasireference electrode. The electrochemical experiments were carried out under a dry and oxygen-free atmosphere (H2O < 1 ppm, O2 < 1 ppm) in dry DMF (with a viologen concentration of ca. 104 M) with TBAP (0.1 M) as the supporting electrolyte. The voltammograms were recorded on a Biologic SP150 potentiostat with positive feedback compensation. Based on repetitive measurements, absolute errors on potentials were estimated to be ≈ ( 5 mV. (23) Jarzeba, W.; Pommeret, S.; Mialocq, J. C. Chem. Phys. Lett. 2001, 333, 419.

2069

dx.doi.org/10.1021/cg2003244 |Cryst. Growth Des. 2011, 11, 2064–2069