research communications
Crystal structures of isotypic poly[bis(benzimidazolium) [tetra-μ-iodido-stannate(II)]] and poly[bis(5,6-difluorobenzimidazolium) [tetra-μ-iodido-stannate(II)]]
aDepartment of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
*Correspondence e-mail: liu@dcb.unibe.ch
The isostructural title compounds, {(C7H7N2)2[SnI4]}n, (1), and {(C7H5F2N2)2[SnI4]}n, (2), show a layered perovskite-type structure composed of anionic {[SnI4]2−}n sheets parallel to (100), which are decorated on both sides with templating benzimidazolium or 5,6-difluorobenzimidazolium cations, respectively. These planar organic heterocycles mainly form N—H⋯I hydrogen bonds to the terminal I atoms of the corner-sharing [SnI6] octahedra (point group symmetry 2) from the inorganic layer, but not to the bridging ones. This is in contrast to most of the reported structures of related compounds where ammonium cations are involved. Here hydrogen bonding to both types of iodine atoms and thereby a distortion of the inorganic layers to various extents is observed. For (1) and (2), all Sn—I—Sn angles are linear and no out-of-plane distortions of the inorganic layers occur, a fact of relevance in view of the material properties. The arrangement of the aromatic cations is mainly determined through the direction of the N—H⋯I hydrogen bonds. The coherence between organic bilayers along [100] is mainly achieved through van der Waals interactions.
1. Chemical context
The title compounds, (1) and (2), belong to an extensive family of materials exhibiting a perovskite-type structure, which can vary with respect to the dimensionality of its extended inorganic framework, ranging from two-dimensional, [MX4]n2n−, to three-dimensional, [MX3]nn− (Mitzi, 1999, 2001, 2004; Mitzi et al., 2001; Zhengtao et al., 2003a,b). The former case is exemplified by anionic [MX4]n2n− sheets (M = divalent metal ion; X = halogen) of corner-sharing MX6 octahedra, which are separated by bilayers of organic cations.
For most reported layered perovskites, these organic molecules are terminated with one or two protonated primary amine groups. Thereby, the ammonium head(s) form N—H⋯X hydrogen bonds to any of the bridging and terminal halogen atoms in the inorganic layers (Mitzi et al., 2002; Mercier et al., 2004; Sourisseau et al., 2007; Pradeesh et al., 2013). In the actual case, however, as a novel aspect, the bicyclic aromatic benzimidazole unit is introduced as an organic part. There are numerous general examples of benzimidazole acting as a neutral ligand (Keene et al., 2010) and similarly in its protonated form (Mouchaham et al., 2010). In this context, the present study explicitly demonstrates that benzimidazolium cations and corresponding derivatives can stabilize the layered perovskite structure as well, while fitting perfectly into the `footprint' provided by the inorganic framework. This observation bears importance since the extent of the in- and out-of-plane angular distortions, twisting and buckling of the anionic sheets, is largely determined by the relative charge density, steric requirements and hydrogen-bonding pattern of the organic cations (Knutson & Martin, 2005; Takahashi et al., 2007). These distortions correlate with the band gaps of the perovskite-type semiconductors. It is interesting to note that perovskite-based solar cells have recently been catapulted to the cutting edge of thin-film photovoltaic research (Hao et al., 2014; Marchioro et al., 2014). Consequently, the chemical variability which comes with the imidazolium cation, especially the range of possible substitutions on its molecular skeleton, gives an additional structural diversity to this class of compounds. As a case in point, consider the difluoro-substituted compound (2) which renders not only modified van der Waals interactions for the organic bilayers, but also tailors the `chemistry' of the crystal surfaces.
2. Structural commentary
Compounds (1) and (2) are isostructural. Their asymmetric units, Figs. 1 and 2, consist of an Sn2+ cation situated on a twofold rotation axis (Wyckoff position 4e), three iodine atoms [one in a general position, one on an inversion centre (4a) and one on a twofold rotation axis (4e)] and a benzimidazolium or 5,6-difluorobenzimidazolium cation, respectively. The main building blocks of the structure are corner-sharing [SnI6] octahedra, which form planar sheets with formula {[SnI4]2−}n which extend parallel to (100). The negative charge of these layers is compensated by the organic cations, which are on both sides of the layer, attached by strong hydrogen-bonding and Coulombic interactions (Figs. 3 and 4). This structural motif can be regarded as an A–B–A layer system, where A represents the aromatic cation and B the tin iodide layer. The coherence between organic bilayers along [100] is mainly achieved through van der Waals interactions. The Sn—I bond lengths for (1) range from 3.0626 (3) Å to 3.1607 (3) Å [(2): 3.0491 (5) Å to 3.1596 (3) Å], with no distinct pattern for bridging compared to terminal iodine atoms (Tables 1 and 2). These values are in agreement with those reported previously for related tin iodide perovskite structures, as for example [(C4H9NH3)2[SnI4]], where the bond lengths range from 3.133 Å to 3.16 Å (Mitzi, 1996). The I—Sn—I angles of the [SnI6] octahedra in the title structures deviate slightly from the ideal octahedral geometry. With 83.886 (4)° for (1) [(2): 84.077 (6)°], the I2—Sn1—I3 angle has the largest difference. On the other hand, all Sn—I—Sn angles are linear, which leads to the formation of an almost rectangular grid (Fig. 5). There is no out-of-plane distortion of the inorganic sheet. The arrangement of the aromatic cations is mainly determined through the direction of N—H⋯I hydrogen bonds to the apical iodine atoms (Tables 3 and 4; Figs. 3 and 4). There is no N—H⋯Ibridging contact smaller than the sum of the respective van der Waals radii (H: 1.2, I: 1.98 Å; Bondi, 1964). This is in contrast to primary ammonium cations, which form hydrogen bonds to both apical and bridging iodine atoms. The shortest H⋯Ibridging distance is C3—H3⋯I2 with 3.12 Å for (1) [(2): 3.19 Å] close to the sum of van der Waals radii. Adjacent cations within an organic layer show a plane-to-plane distance of 3.786 Å for (1) [(2): 3.730 Å] (Fig. 6). The shortest contact distances between the organic bilayers for both compounds are close to the sums of the van der Waals radii [C8⋯H6i 2.801 Å in (1) and F8⋯H9ii 2.557 Å in (2); (i): − x, − + y, − z; (ii): − x, − y, −z]. The larger size of the fluorine atom in comparison to the hydrogen atom is reflected in a larger A–B–A layer spacing of 14.407 Å for (2) compared to 13.950 Å for (1).
|
|
3. Database survey
In the Cambridge Structural Database (Version 5.35, last update November 2013; Allen, 2002) no structures of compounds containing a (benz)imidazolium cation for layered perovskites are listed, making the two examples presented herein the only ones reported so far.
4. Synthesis and crystallization
Compound (1) was synthesized and crystallized by a solvothermal method using a mixture of tin(II) iodide and benzimidazole in a 1:2 molar ratio. In a 50 ml round-bottom flask, 4 ml concentrated HI (57 wt. %, stabilized with hypophosphorous acid) was mixed with 2 mmol (0.236 g) benzimidazole. After stirring for one minute, this solution was added to a sample flask containing 1 mmol (0.372 g) tin(II) iodide. The reaction flask was put in a 23 ml Teflon container. The reaction was conducted at 363 K for ten h after which the autoclave was slowly cooled (1 K/h) to room temperature. Thin, black plate-like crystals were obtained. The synthetic procedure for (2) was identical to that for (1), only using 0.5 mmol (0.77 g) 5,6-difluorobenzimidazole and 0.25 mmol (0.093 g) tin(II) iodide as starting materials. Thin, black plate-like crystals were obtained.
5. Refinement
Crystal data, data collection and structure . The N-H hydrogen atoms were located in difference Fourier maps and were freely refined. The C-bound hydrogen atoms were included in calculated positions and treated as riding atoms with C—H = 0.95 Å. The isotropic displacement parameters of all H atoms were constrained to 1.2Ueq of their parent atoms. The crystal of compound (2) was a non-merohedral twin. The two twin components were related by a twofold rotation about the c* axis. The data from both twin components were integrated to give 8236 and 7625 non-overlapped reflections for twin components 1 and 2, respectively, plus 13836 overlapping reflections from both twin components. Symmetry-equivalent reflections were merged. The major twin fraction, component 1, refined to 0.6870 (12).
details are summarized in Table 5
|
Supporting information
10.1107/S1600536814019151/wm5043sup1.cif
contains datablocks 1, 2. DOI:Structure factors: contains datablock 1. DOI: 10.1107/S1600536814019151/wm50431sup2.hkl
Structure factors: contains datablock 2. DOI: 10.1107/S1600536814019151/wm50432sup3.hkl
The title compounds, (1) and (2), belong to an extensive family of materials exhibiting a perovskite-type structure, which can vary with respect to the dimensionality of its extended inorganic framework, ranging from two-dimensional, [MX4]n2n-, to three-dimensional, [MX3]nn- (Mitzi, 1999, 2001, 2004; Mitzi et al., 2001; Zhengtao et al., 2003a,b). The former case is exemplified by anionic [MX4]n2n- sheets (M = divalent metal ion; X = halogen) of corner-sharing MX6 octahedra, which are separated by bilayers of organic cations. For most reported layered perovskites, these organic molecules are terminated with one or two protonated primary amine groups. Thereby, the ammonium head(s) form N—H···X hydrogen bonds to any of the bridging and terminal halogen atoms in the inorganic layers (Mitzi et al., 2002; Mercier et al., 2004; Sourisseau et al., 2007; Pradeesh et al., 2013). In the actual case, however, as a novel aspect, the bicyclic aromatic benzimidazole unit is introduced as an organic part. There are numerous general examples of benzimidazole acting as a neutral ligand (Keene et al., 2010) and similarly in its protonated form (Mouchaham et al., 2010). In this context, the present study explicitly demonstrates that benzimidazolium cations and corresponding derivatives can stabilize the layered perovskite structure as well, while fitting perfectly into the `footprint' provided by the inorganic framework. This observation bears importance since the extent of the in- and out-of-plane angular distortions, twisting and buckling of the anionic sheets, is largely determined by the relative charge density, steric requirements and hydrogen-bonding pattern of the organic cations (Knutson & Martin, 2005; Takahashi et al., 2007). These distortions correlate with the band gaps of the perovskite-type semiconductors. It is interesting to note that perovskite-based solar cells have recently been catapulted to the cutting edge of thin-film photovoltaic research (Hao et al., 2014; Marchioro et al., 2014). Consequently, the chemical variability which comes with the imidazolium cation, especially the range of possible substitutions on its molecular skeleton, gives an additional structural diversity to this class of compounds. As a case in point, consider the difluoro-substituted compound (2) which renders not only modified van der Waals interactions for the organic bilayers, but also tailors the `chemistry' of the crystal surfaces.
Compounds (1) and (2) are isostructural. Their asymmetric units, Figs. 1 and 2, consist of an Sn2+ cation situated on a twofold rotation axis (Wyckoff position 4e), three iodine atoms [one in a general position, one on an inversion centre (4a) and one on a twofold rotation axis (4e)] and a benzimidazolium or 5,6-difluorobenzimidazolium cation, respectively. The main building blocks of the structure are corner-sharing [SnI6] octahedra, which form planar sheets with formula {[SnI4]2-}n which extend parallel to (100). The negative charge of these layers is compensated by the organic cations, which are on both sides of the layer, attached by strong hydrogen-bonding and Coulombic interactions (Figs. 3 and 4). This structural motif can be regarded as an A–B–A layer system, where A represents the aromatic cation and B the tin iodide layer. The coherence between organic bilayers along [100] is mainly achieved through van der Waals interactions. The Sn—I bond lengths for (1) range from 3.0626 (3) Å to 3.1607 (3) Å [(2): 3.0491 (5) Å to 3.1596 (3) Å], with no distinct pattern for bridging compared to terminal iodine atoms (Tables 1 and 2). These values are in agreement with those reported previously for related tin iodide perovskite structures, as for example [(C4H9NH3)2[SnI4]], where the bond lengths range from 3.133 Å to 3.16 Å (Mitzi, 1996). The I—Sn—I angles of the [SnI6] octahedra in the title structures deviate slightly from the ideal octahedral geometry. With 83.886 (4)° for (1) [(2): 84.077 (6)°], the I2—Sn1—I3 angle has the largest difference. On the other hand, all Sn—I—Sn angles are linear, which leads to the formation of an almost rectangular grid (Fig. 5). There is no out-of-plane distortion of the inorganic sheet. The arrangement of the aromatic cations is mainly determined through the direction of N—H···I hydrogen bonds to the apical iodine atoms (Tables 3 and 4; Figs. 3 and 4). There is no N—H···Ibridging contact smaller than the sum of the respective van der Waals radii (H: 1.2, I: 1.98 Å; Bondi, 1964). This is in contrast to primary ammonium cations, which form hydrogen bonds to both apical and bridging iodine atoms. The shortest H···Ibridging distance is C3—H3···I2 with 3.12Å for (1) [(2): 3.19Å] close to the sum of van der Waals radii (H: 1.2, I: 1.98 Å; Bondi, 1964). Adjacent cations within an organic layer show a plane-to-plane distance of 3.786 Å for (1) [(2): 3.730 Å] (Fig. 6). The shortest contact distances between the organic bilayers for both compounds are close to the sums of the van der Waals radii [C8···H6i 2.801 Å in (1) and F8···H9ii 2.557 Å in (2); (i): 1/2-x, -1/2+y, 1/2-z; (ii): 1/2-x, 1/2-y, -z]. The larger size of the fluorine atom in comparison to the hydrogen atom is reflected in a larger A–B–A layer spacing of 14.407 Å for (2) compared to 13.950 Å for (1).
In the Cambridge Structural Database (Version 5.35, last update November 2013; Allen, 2002) no structures of compounds containing a (benz)imidazolium cation for layered perovskites are listed, making the two examples presented herein the only ones reported so far.
Compound (1) was synthesized and crystallized by a solvothermal method using a mixture of tin(II) iodide and benzimidazole in a 1:2 molar ratio. In a 50 ml round-bottom flask, 4 ml concentrated HI (57 wt. %, stabilized with hypophosphorous acid) was mixed with 2 mmol (0.236 g) benzimidazole. After stirring for one minute, this solution was added to a sample flask containing 1 mmol (0.372 g) tin(II) iodide. The reaction flask was put in a 23 ml Teflon container. The reaction was conducted at 363 K for ten hours after which the autoclave was slowly cooled (1 K/h) to room temperature. Thin, black plate-like crystals were obtained. The synthetic procedure for (2) was identical to that for (1), only using 0.5 mmol (0.77 g) 5,6-difluorobenzimidazole and 0.25 mmol (0.093 g) tin(II) iodide as starting materials. Thin, black plate-like crystals were obtained.
Crystal data, data collection and structure
details are summarized in Table 5. The N—H hydrogen atoms were located in difference Fourier maps and were freely refined. The C-bound hydrogen atoms were included in calculated positions and treated as riding atoms with C—H = 0.95 Å. The isotropic displacement parameters of all H atoms were constrained to 1.2Ueq of their parent atoms. The crystal of compound (2) was a non-merohedral twin. The two twin components were related by a twofold rotation about the c* axis. The data from both twin components were integrated to give 8236 and 7625 non-overlapped reflections for twin components 1 and 2, respectively, plus 13836 overlapping reflections from both twin components. Symmetry-equivalent reflections were merged. The major twin fraction, component 1, refined to 0.6870 (12).For both compounds, data collection: APEX2 (Bruker, 2001); cell
SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008) and VESTA (Momma & Izumi, 2011); software used to prepare material for publication: publCIF (Westrip, 2010).Fig. 1. The main building units of (1), showing atom labeling and thermal ellipsoids drawn at the 50% probability level. [Symmetry codes: (i) x, y+1, z; (ii) -x, y, -z+1/2.] | |
Fig. 2. The main building units of (2), showing atom labeling and thermal ellipsoids drawn at the 50% probability level. [Symmetry codes: (i) x, y+1, z; (ii) -x, y, -z+1/2.] | |
Fig. 3. The crystal packing of compound (1) viewed along [010]. N—H···I hydrogen bonds are shown as dashed lines. | |
Fig. 4. The crystal packing of compound (2) viewed along [010]. N—H···I hydrogen bonds are shown as dashed lines. | |
Fig. 5. View along the a* axis of a tin iodide layer of (2). For clarity, the atoms are represented as spheres with uniform sizes selected for each atom type. | |
Fig. 6. View along the a* axis of a double layer of tin iodide and the organic cations of (2). For clarity, the [SnI6] octahedra are shown as polyhedra, the atoms of the organic cations are represented as spheres with uniform sizes selected for each atom type. |
(C7H7N2)2[SnI4] | F(000) = 1552 |
Mr = 864.58 | Dx = 2.662 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 29.6316 (5) Å | Cell parameters from 9894 reflections |
b = 6.22328 (10) Å | θ = 2.9–33.1° |
c = 12.4258 (2) Å | µ = 6.91 mm−1 |
β = 109.6798 (8)° | T = 123 K |
V = 2157.55 (6) Å3 | Plate, black |
Z = 4 | 0.15 × 0.10 × 0.05 mm |
Bruker APEXII CCD diffractometer | 3713 independent reflections |
Radiation source: fine-focus sealed tube | 3222 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.033 |
ω scans | θmax = 33.3°, θmin = 2.9° |
Absorption correction: multi-scan (SADABS; Bruker, 2001) | h = −44→45 |
Tmin = 0.570, Tmax = 0.747 | k = −8→9 |
24695 measured reflections | l = −18→18 |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.022 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.045 | w = 1/[σ2(Fo2) + (0.0195P)2 + 1.2708P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max = 0.001 |
3713 reflections | Δρmax = 0.70 e Å−3 |
113 parameters | Δρmin = −1.15 e Å−3 |
(C7H7N2)2[SnI4] | V = 2157.55 (6) Å3 |
Mr = 864.58 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 29.6316 (5) Å | µ = 6.91 mm−1 |
b = 6.22328 (10) Å | T = 123 K |
c = 12.4258 (2) Å | 0.15 × 0.10 × 0.05 mm |
β = 109.6798 (8)° |
Bruker APEXII CCD diffractometer | 3713 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2001) | 3222 reflections with I > 2σ(I) |
Tmin = 0.570, Tmax = 0.747 | Rint = 0.033 |
24695 measured reflections |
R[F2 > 2σ(F2)] = 0.022 | 0 restraints |
wR(F2) = 0.045 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.06 | Δρmax = 0.70 e Å−3 |
3713 reflections | Δρmin = −1.15 e Å−3 |
113 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
Sn1 | 0.0000 | 0.05346 (3) | 0.2500 | 0.01164 (5) | |
I1 | 0.11310 (2) | 0.06766 (2) | 0.33720 (2) | 0.01725 (5) | |
I2 | 0.0000 | 0.0000 | 0.0000 | 0.01759 (5) | |
I3 | 0.0000 | −0.45442 (3) | 0.2500 | 0.01775 (5) | |
C1 | 0.15716 (9) | 0.4629 (4) | 0.0612 (2) | 0.0185 (5) | |
N2 | 0.11246 (8) | 0.3669 (4) | 0.02976 (18) | 0.0233 (4) | |
H2 | 0.1040 (10) | 0.271 (5) | −0.017 (2) | 0.028* | |
C3 | 0.08537 (9) | 0.4715 (4) | 0.0783 (2) | 0.0244 (5) | |
H3 | 0.0530 | 0.4374 | 0.0692 | 0.029* | |
N4 | 0.11030 (7) | 0.6311 (4) | 0.14131 (18) | 0.0218 (4) | |
H4 | 0.0991 (10) | 0.726 (5) | 0.175 (2) | 0.026* | |
C5 | 0.15559 (8) | 0.6333 (4) | 0.1327 (2) | 0.0192 (5) | |
C6 | 0.19471 (9) | 0.7684 (4) | 0.1792 (2) | 0.0259 (5) | |
H6 | 0.1937 | 0.8850 | 0.2278 | 0.031* | |
C7 | 0.23491 (9) | 0.7241 (5) | 0.1511 (2) | 0.0290 (6) | |
H7 | 0.2626 | 0.8114 | 0.1821 | 0.035* | |
C8 | 0.23624 (10) | 0.5553 (4) | 0.0788 (2) | 0.0270 (6) | |
H8 | 0.2646 | 0.5321 | 0.0610 | 0.032* | |
C9 | 0.19775 (9) | 0.4211 (4) | 0.0323 (2) | 0.0247 (5) | |
H9 | 0.1988 | 0.3059 | −0.0169 | 0.030* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Sn1 | 0.01576 (10) | 0.00942 (10) | 0.01029 (10) | 0.000 | 0.00511 (8) | 0.000 |
I1 | 0.01570 (8) | 0.01759 (8) | 0.01778 (8) | −0.00079 (5) | 0.00476 (6) | −0.00078 (5) |
I2 | 0.02292 (11) | 0.01962 (11) | 0.01103 (10) | −0.00274 (9) | 0.00676 (8) | −0.00021 (8) |
I3 | 0.02441 (11) | 0.00891 (10) | 0.02168 (11) | 0.000 | 0.01005 (9) | 0.000 |
C1 | 0.0188 (11) | 0.0171 (12) | 0.0178 (11) | 0.0025 (9) | 0.0035 (9) | 0.0000 (9) |
N2 | 0.0235 (11) | 0.0231 (11) | 0.0228 (11) | −0.0026 (9) | 0.0073 (9) | −0.0078 (9) |
C3 | 0.0188 (12) | 0.0264 (14) | 0.0282 (14) | −0.0015 (10) | 0.0084 (10) | −0.0034 (11) |
N4 | 0.0212 (10) | 0.0219 (11) | 0.0235 (11) | 0.0002 (9) | 0.0092 (9) | −0.0062 (9) |
C5 | 0.0199 (11) | 0.0186 (11) | 0.0187 (11) | 0.0027 (10) | 0.0059 (9) | 0.0005 (9) |
C6 | 0.0240 (13) | 0.0264 (13) | 0.0248 (13) | −0.0027 (11) | 0.0049 (10) | −0.0057 (11) |
C7 | 0.0184 (12) | 0.0337 (15) | 0.0290 (14) | −0.0031 (11) | 0.0002 (10) | −0.0004 (12) |
C8 | 0.0201 (12) | 0.0331 (15) | 0.0298 (14) | 0.0061 (11) | 0.0111 (11) | 0.0055 (11) |
C9 | 0.0246 (13) | 0.0262 (13) | 0.0244 (13) | 0.0067 (11) | 0.0096 (11) | 0.0006 (10) |
Sn1—I1 | 3.1571 (2) | N4—C5 | 1.382 (3) |
Sn1—I2 | 3.1242 (1) | N4—H4 | 0.85 (3) |
Sn1—I3 | 3.1607 (3) | C5—C6 | 1.390 (3) |
Sn1—I3i | 3.0626 (3) | C6—C7 | 1.377 (4) |
C1—N2 | 1.384 (3) | C6—H6 | 0.9500 |
C1—C9 | 1.390 (3) | C7—C8 | 1.392 (4) |
C1—C5 | 1.394 (3) | C7—H7 | 0.9500 |
N2—C3 | 1.326 (3) | C8—C9 | 1.374 (4) |
N2—H2 | 0.81 (3) | C8—H8 | 0.9500 |
C3—N4 | 1.325 (3) | C9—H9 | 0.9500 |
C3—H3 | 0.9500 | ||
I1—Sn1—I2 | 89.357 (3) | C1—N2—H2 | 124 (2) |
I1—Sn1—I2ii | 90.984 (3) | N4—C3—N2 | 109.6 (2) |
I1—Sn1—I1ii | 176.793 (9) | N4—C3—H3 | 125.2 |
I2—Sn1—I2ii | 167.773 (7) | N2—C3—H3 | 125.2 |
I1—Sn1—I3 | 91.604 (4) | C3—N4—C5 | 108.9 (2) |
I2—Sn1—I3 | 83.886 (4) | C3—N4—H4 | 125.2 (19) |
I1—Sn1—I3i | 88.396 (4) | C5—N4—H4 | 125.5 (19) |
I2—Sn1—I3i | 96.114 (4) | N4—C5—C6 | 132.0 (2) |
I3—Sn1—I3i | 180.0 | N4—C5—C1 | 106.5 (2) |
I3i—Sn1—I2ii | 96.113 (4) | C6—C5—C1 | 121.5 (2) |
I3i—Sn1—I1ii | 88.396 (4) | C7—C6—C5 | 116.4 (2) |
I2—Sn1—I1ii | 90.984 (3) | C7—C6—H6 | 121.8 |
I2ii—Sn1—I1ii | 89.357 (3) | C5—C6—H6 | 121.8 |
I2ii—Sn1—I3 | 83.887 (4) | C6—C7—C8 | 122.0 (3) |
I1ii—Sn1—I3 | 91.604 (4) | C6—C7—H7 | 119.0 |
Sn1iii—I2—Sn1 | 180.0 | C8—C7—H7 | 119.0 |
Sn1iv—I3—Sn1 | 180.0 | C9—C8—C7 | 122.0 (2) |
N2—C1—C9 | 132.5 (2) | C9—C8—H8 | 119.0 |
N2—C1—C5 | 105.9 (2) | C7—C8—H8 | 119.0 |
C9—C1—C5 | 121.6 (2) | C8—C9—C1 | 116.5 (2) |
C3—N2—C1 | 109.2 (2) | C8—C9—H9 | 121.8 |
C3—N2—H2 | 127 (2) | C1—C9—H9 | 121.8 |
C9—C1—N2—C3 | −178.0 (3) | C9—C1—C5—C6 | −0.5 (4) |
C5—C1—N2—C3 | 0.2 (3) | N4—C5—C6—C7 | −179.3 (3) |
C1—N2—C3—N4 | −0.7 (3) | C1—C5—C6—C7 | −0.2 (4) |
N2—C3—N4—C5 | 0.8 (3) | C5—C6—C7—C8 | 0.9 (4) |
C3—N4—C5—C6 | 178.5 (3) | C6—C7—C8—C9 | −0.9 (4) |
C3—N4—C5—C1 | −0.7 (3) | C7—C8—C9—C1 | 0.1 (4) |
N2—C1—C5—N4 | 0.3 (3) | N2—C1—C9—C8 | 178.6 (3) |
C9—C1—C5—N4 | 178.7 (2) | C5—C1—C9—C8 | 0.6 (4) |
N2—C1—C5—C6 | −179.0 (2) |
Symmetry codes: (i) x, y+1, z; (ii) −x, y, −z+1/2; (iii) −x, −y, −z; (iv) x, y−1, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2···I1v | 0.81 (3) | 2.85 (3) | 3.615 (2) | 158 (3) |
N4—H4···I1i | 0.85 (3) | 2.86 (3) | 3.630 (2) | 151 (2) |
Symmetry codes: (i) x, y+1, z; (v) x, −y, z−1/2. |
(C7H5F2N2)2[SnI4] | F(000) = 1680 |
Mr = 936.55 | Dx = 2.744 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 31.3825 (6) Å | Cell parameters from 9949 reflections |
b = 6.18011 (12) Å | θ = 5.5–65.4° |
c = 12.38507 (13) Å | µ = 6.61 mm−1 |
β = 109.3241 (7)° | T = 123 K |
V = 2266.72 (7) Å3 | Plate, black |
Z = 4 | 0.33 × 0.33 × 0.01 mm |
Bruker APEXII CCD diffractometer | 5792 independent reflections |
Radiation source: fine-focus sealed tube | 5179 reflections with I > 2σ(I) |
Graphite monochromator | θmax = 33.1°, θmin = 2.8° |
rotation method scans | h = −47→43 |
Absorption correction: multi-scan (TWINABS; Bruker, 2001) | k = 0→9 |
Tmin = 0.322, Tmax = 0.522 | l = 0→18 |
29697 measured reflections |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.035 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.124 | w = 1/[σ2(Fo2) + (0.0948P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.07 | (Δ/σ)max = 0.001 |
5792 reflections | Δρmax = 1.95 e Å−3 |
132 parameters | Δρmin = −1.74 e Å−3 |
(C7H5F2N2)2[SnI4] | V = 2266.72 (7) Å3 |
Mr = 936.55 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 31.3825 (6) Å | µ = 6.61 mm−1 |
b = 6.18011 (12) Å | T = 123 K |
c = 12.38507 (13) Å | 0.33 × 0.33 × 0.01 mm |
β = 109.3241 (7)° |
Bruker APEXII CCD diffractometer | 29697 measured reflections |
Absorption correction: multi-scan (TWINABS; Bruker, 2001) | 5792 independent reflections |
Tmin = 0.322, Tmax = 0.522 | 5179 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.035 | 0 restraints |
wR(F2) = 0.124 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.07 | Δρmax = 1.95 e Å−3 |
5792 reflections | Δρmin = −1.74 e Å−3 |
132 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refined as a 2-component twin. |
x | y | z | Uiso*/Ueq | ||
Sn1 | 0.0000 | 0.05198 (5) | 0.2500 | 0.01458 (10) | |
I1 | 0.10663 (2) | 0.06742 (4) | 0.33581 (3) | 0.02019 (10) | |
I2 | 0.0000 | 0.0000 | 0.0000 | 0.02079 (11) | |
I3 | 0.0000 | −0.45465 (5) | 0.2500 | 0.02092 (11) | |
C1 | 0.14859 (19) | 0.4618 (7) | 0.0571 (4) | 0.0227 (9) | |
N2 | 0.10624 (15) | 0.3704 (7) | 0.0285 (3) | 0.0249 (8) | |
H2 | 0.092 (2) | 0.260 (10) | −0.025 (5) | 0.030* | |
C3 | 0.08158 (18) | 0.4824 (8) | 0.0780 (5) | 0.0271 (10) | |
H3 | 0.0511 | 0.4521 | 0.0709 | 0.033* | |
N4 | 0.10586 (15) | 0.6417 (7) | 0.1383 (3) | 0.0251 (8) | |
H4 | 0.099 (2) | 0.714 (9) | 0.178 (5) | 0.030* | |
C5 | 0.14871 (16) | 0.6384 (8) | 0.1291 (4) | 0.0232 (9) | |
C6 | 0.18595 (18) | 0.7714 (8) | 0.1732 (4) | 0.0283 (10) | |
H6 | 0.1860 | 0.8918 | 0.2210 | 0.034* | |
C7 | 0.22244 (18) | 0.7166 (9) | 0.1429 (5) | 0.0319 (11) | |
F7 | 0.26085 (11) | 0.8325 (7) | 0.1827 (3) | 0.0460 (9) | |
C8 | 0.22240 (19) | 0.5394 (9) | 0.0718 (5) | 0.0307 (12) | |
F8 | 0.26118 (12) | 0.5015 (6) | 0.0508 (4) | 0.0447 (8) | |
C9 | 0.18591 (19) | 0.4095 (9) | 0.0276 (4) | 0.0279 (10) | |
H9 | 0.1861 | 0.2901 | −0.0205 | 0.033* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Sn1 | 0.0230 (2) | 0.00982 (18) | 0.01224 (19) | 0.000 | 0.00759 (19) | 0.000 |
I1 | 0.02280 (16) | 0.01818 (15) | 0.01977 (16) | −0.00088 (9) | 0.00728 (14) | −0.00114 (10) |
I2 | 0.0304 (2) | 0.02089 (19) | 0.01304 (19) | −0.00124 (18) | 0.00977 (19) | −0.00007 (13) |
I3 | 0.0319 (2) | 0.00964 (17) | 0.0243 (2) | 0.000 | 0.0134 (2) | 0.000 |
C1 | 0.029 (3) | 0.022 (2) | 0.019 (2) | 0.0032 (17) | 0.0095 (19) | −0.0028 (15) |
N2 | 0.027 (2) | 0.022 (2) | 0.0249 (19) | −0.0011 (17) | 0.0085 (17) | −0.0036 (16) |
C3 | 0.030 (3) | 0.029 (2) | 0.024 (2) | −0.002 (2) | 0.012 (2) | −0.0046 (19) |
N4 | 0.030 (2) | 0.023 (2) | 0.025 (2) | 0.0035 (17) | 0.0123 (18) | −0.0023 (16) |
C5 | 0.027 (2) | 0.026 (2) | 0.0158 (18) | 0.0022 (18) | 0.0064 (17) | −0.0023 (17) |
C6 | 0.035 (3) | 0.026 (2) | 0.025 (2) | −0.003 (2) | 0.010 (2) | −0.0064 (18) |
C7 | 0.027 (2) | 0.034 (3) | 0.030 (2) | −0.006 (2) | 0.004 (2) | −0.003 (2) |
F7 | 0.0326 (18) | 0.055 (2) | 0.048 (2) | −0.0165 (17) | 0.0106 (16) | −0.0163 (19) |
C8 | 0.024 (3) | 0.042 (3) | 0.027 (3) | 0.005 (2) | 0.011 (2) | −0.002 (2) |
F8 | 0.0299 (18) | 0.057 (2) | 0.050 (2) | 0.0018 (16) | 0.0168 (19) | −0.0133 (19) |
C9 | 0.034 (3) | 0.026 (2) | 0.025 (2) | 0.001 (2) | 0.011 (2) | −0.0035 (18) |
Sn1—I1 | 3.1596 (3) | C3—H3 | 0.9500 |
Sn1—I2 | 3.1129 (1) | N4—C5 | 1.387 (6) |
Sn1—I3 | 3.1310 (5) | N4—H4 | 0.75 (5) |
Sn1—I3i | 3.0491 (5) | C5—C6 | 1.385 (7) |
Sn1—I1ii | 3.1596 (3) | C6—C7 | 1.361 (7) |
C1—C9 | 1.376 (7) | C6—H6 | 0.9500 |
C1—N2 | 1.378 (7) | C7—F7 | 1.348 (6) |
C1—C5 | 1.408 (6) | C7—C8 | 1.404 (7) |
N2—C3 | 1.330 (7) | C8—F8 | 1.347 (6) |
N2—H2 | 0.95 (6) | C8—C9 | 1.357 (8) |
C3—N4 | 1.316 (7) | C9—H9 | 0.9500 |
I1—Sn1—I2 | 89.374 (6) | C1—N2—H2 | 131 (3) |
I1—Sn1—I2ii | 90.984 (6) | N4—C3—N2 | 109.6 (5) |
I1—Sn1—I1ii | 176.539 (14) | N4—C3—H3 | 125.2 |
I2—Sn1—I2ii | 168.154 (12) | N2—C3—H3 | 125.2 |
I1—Sn1—I3 | 91.731 (7) | C3—N4—C5 | 109.7 (4) |
I2—Sn1—I3 | 84.077 (6) | C3—N4—H4 | 125 (5) |
I1—Sn1—I3i | 88.269 (7) | C5—N4—H4 | 124 (5) |
I2—Sn1—I3i | 95.923 (6) | C6—C5—N4 | 132.3 (4) |
I3—Sn1—I3i | 180.0 | C6—C5—C1 | 122.3 (5) |
I3i—Sn1—I2ii | 95.923 (6) | N4—C5—C1 | 105.3 (4) |
I2ii—Sn1—I3 | 84.077 (6) | C7—C6—C5 | 114.9 (4) |
I3i—Sn1—I1ii | 88.270 (7) | C7—C6—H6 | 122.6 |
I2—Sn1—I1ii | 90.984 (6) | C5—C6—H6 | 122.6 |
I2ii—Sn1—I1ii | 89.374 (6) | F7—C7—C6 | 119.9 (5) |
I3—Sn1—I1ii | 91.730 (7) | F7—C7—C8 | 117.4 (5) |
Sn1iii—I2—Sn1 | 180.0 | C6—C7—C8 | 122.7 (5) |
Sn1iv—I3—Sn1 | 180.0 | F8—C8—C9 | 121.0 (5) |
C9—C1—N2 | 131.9 (4) | F8—C8—C7 | 116.3 (5) |
C9—C1—C5 | 121.7 (5) | C9—C8—C7 | 122.7 (5) |
N2—C1—C5 | 106.3 (4) | C8—C9—C1 | 115.6 (5) |
C3—N2—C1 | 109.1 (4) | C8—C9—H9 | 122.2 |
C3—N2—H2 | 119 (3) | C1—C9—H9 | 122.2 |
C9—C1—N2—C3 | −179.2 (6) | C1—C5—C6—C7 | −0.8 (7) |
C5—C1—N2—C3 | 0.5 (6) | C5—C6—C7—F7 | −178.7 (5) |
C1—N2—C3—N4 | −0.5 (6) | C5—C6—C7—C8 | 0.3 (8) |
N2—C3—N4—C5 | 0.2 (6) | F7—C7—C8—F8 | 0.4 (8) |
C3—N4—C5—C6 | 178.4 (5) | C6—C7—C8—F8 | −178.7 (5) |
C3—N4—C5—C1 | 0.1 (6) | F7—C7—C8—C9 | 179.2 (5) |
C9—C1—C5—C6 | 0.9 (8) | C6—C7—C8—C9 | 0.2 (9) |
N2—C1—C5—C6 | −178.9 (4) | F8—C8—C9—C1 | 178.7 (5) |
C9—C1—C5—N4 | 179.4 (5) | C7—C8—C9—C1 | −0.2 (8) |
N2—C1—C5—N4 | −0.4 (5) | N2—C1—C9—C8 | 179.4 (5) |
N4—C5—C6—C7 | −178.9 (5) | C5—C1—C9—C8 | −0.4 (8) |
Symmetry codes: (i) x, y+1, z; (ii) −x, y, −z+1/2; (iii) −x, −y, −z; (iv) x, y−1, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2···I1v | 0.95 (6) | 2.79 (6) | 3.610 (4) | 145 (4) |
N4—H4···I1i | 0.75 (5) | 2.88 (6) | 3.587 (4) | 157 (6) |
Symmetry codes: (i) x, y+1, z; (v) x, −y, z−1/2. |
Sn1—I1 | 3.1571 (2) | Sn1—I3 | 3.1607 (3) |
Sn1—I2 | 3.1242 (1) | Sn1—I3i | 3.0626 (3) |
I1—Sn1—I2 | 89.357 (3) | I2—Sn1—I3 | 83.886 (4) |
I1—Sn1—I2ii | 90.984 (3) | I1—Sn1—I3i | 88.396 (4) |
I1—Sn1—I1ii | 176.793 (9) | I2—Sn1—I3i | 96.114 (4) |
I2—Sn1—I2ii | 167.773 (7) | I3—Sn1—I3i | 180.0 |
I1—Sn1—I3 | 91.604 (4) |
Symmetry codes: (i) x, y+1, z; (ii) −x, y, −z+1/2. |
Sn1—I1 | 3.1596 (3) | Sn1—I3 | 3.1310 (5) |
Sn1—I2 | 3.1129 (1) | Sn1—I3i | 3.0491 (5) |
I1—Sn1—I2 | 89.374 (6) | I2—Sn1—I3 | 84.077 (6) |
I1—Sn1—I2ii | 90.984 (6) | I1—Sn1—I3i | 88.269 (7) |
I1—Sn1—I1ii | 176.539 (14) | I2—Sn1—I3i | 95.923 (6) |
I2—Sn1—I2ii | 168.154 (12) | I3—Sn1—I3i | 180.0 |
I1—Sn1—I3 | 91.731 (7) |
Symmetry codes: (i) x, y+1, z; (ii) −x, y, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2···I1iii | 0.81 (3) | 2.85 (3) | 3.615 (2) | 158 (3) |
N4—H4···I1i | 0.85 (3) | 2.86 (3) | 3.630 (2) | 151 (2) |
Symmetry codes: (i) x, y+1, z; (iii) x, −y, z−1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2···I1iii | 0.95 (6) | 2.79 (6) | 3.610 (4) | 145 (4) |
N4—H4···I1i | 0.75 (5) | 2.88 (6) | 3.587 (4) | 157 (6) |
Symmetry codes: (i) x, y+1, z; (iii) x, −y, z−1/2. |
Experimental details
(1) | (2) | |
Crystal data | ||
Chemical formula | (C7H7N2)2[SnI4] | (C7H5F2N2)2[SnI4] |
Mr | 864.58 | 936.55 |
Crystal system, space group | Monoclinic, C2/c | Monoclinic, C2/c |
Temperature (K) | 123 | 123 |
a, b, c (Å) | 29.6316 (5), 6.22328 (10), 12.4258 (2) | 31.3825 (6), 6.18011 (12), 12.38507 (13) |
β (°) | 109.6798 (8) | 109.3241 (7) |
V (Å3) | 2157.55 (6) | 2266.72 (7) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 6.91 | 6.61 |
Crystal size (mm) | 0.15 × 0.10 × 0.05 | 0.33 × 0.33 × 0.01 |
Data collection | ||
Diffractometer | Bruker APEXII CCD diffractometer | Bruker APEXII CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2001) | Multi-scan (TWINABS; Bruker, 2001) |
Tmin, Tmax | 0.570, 0.747 | 0.322, 0.522 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 24695, 3713, 3222 | 29697, 5792, 5179 |
Rint | 0.033 | ? |
(sin θ/λ)max (Å−1) | 0.772 | 0.768 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.022, 0.045, 1.06 | 0.035, 0.124, 1.07 |
No. of reflections | 3713 | 5792 |
No. of parameters | 113 | 132 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.70, −1.15 | 1.95, −1.74 |
Computer programs: APEX2 (Bruker, 2001), SAINT-Plus (Bruker, 2001), SIR97 (Altomare et al., 1999), SHELXL2014 (Sheldrick, 2008), Mercury (Macrae et al., 2008) and VESTA (Momma & Izumi, 2011), publCIF (Westrip, 2010).
Acknowledgements
This work was supported by the Swiss National Science Foundation (grant No. 200021–147143).
References
Allen, F. H. (2002). Acta Cryst. B58, 380–388. Web of Science CrossRef CAS IUCr Journals Google Scholar
Altomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115–119. Web of Science CrossRef CAS IUCr Journals Google Scholar
Bondi, A. (1964). J. Phys. Chem. 68, 441–451. CrossRef CAS Web of Science Google Scholar
Bruker (2001). APEX2, SAINT-Plus, SADABS and TWINABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Hao, F., Stoumpos, C. C., Chang, R. P. H. & Kanatzidis, M. G. (2014). J. Am. Chem. Soc. 136, 8094–8099. Web of Science CrossRef CAS PubMed Google Scholar
Keene, T. D., Zimmermann, I., Neels, A., Sereda, O., Hauser, J., Bonin, M., Hursthouse, M. B., Price, D. J. & Decurtins, S. (2010). Dalton Trans. 39, 4937–4950. Web of Science CSD CrossRef CAS PubMed Google Scholar
Knutson, J. L. & Martin, J. D. (2005). Inorg. Chem. 44, 4699–4705. Web of Science CrossRef PubMed CAS Google Scholar
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470. Web of Science CrossRef CAS IUCr Journals Google Scholar
Marchioro, A., Teuscher, J., Friedrich, D., Kunst, M., van de Krol, R., Moehl, T., Grätzel, M. & Moser, J.-E. (2014). Nature Photonics, 8, 250–255. Web of Science CrossRef CAS Google Scholar
Mercier, N., Poiroux, S., Riou, A. & Batail, P. (2004). Inorg. Chem. 43, 8361–8366. Web of Science CSD CrossRef PubMed CAS Google Scholar
Mitzi, D. B. (1996). Chem. Mater. 8, pp. 791–800. CSD CrossRef CAS Web of Science Google Scholar
Mitzi, D. B. (1999). Progress in Inorganic Chemistry, Vol. 48, edited by K. D. Karlin. New York: Wiley & Sons Inc. Google Scholar
Mitzi, D. B. (2001). J. Chem. Soc. Dalton Trans. pp. 1–12. Web of Science CrossRef Google Scholar
Mitzi, D. B. (2004). J. Mater. Chem. 14, 2355–2365. Web of Science CrossRef CAS Google Scholar
Mitzi, D. B., Dimitrakopoulos, C. D. & Kosbar, L. L. (2001). Chem. Mater. 13, 3728–3740. Web of Science CSD CrossRef CAS Google Scholar
Mitzi, D. B., Medeiros, D. R. & Malenfant, R. L. (2002). Inorg. Chem. 41, 2134–2145. Web of Science CSD CrossRef PubMed CAS Google Scholar
Momma, K. & Izumi, F. (2011). J. Appl. Cryst. 44, 1272–1276. Web of Science CrossRef CAS IUCr Journals Google Scholar
Mouchaham, G., Roques, N., Imaz, I., Duhayon, C. & Sutter, J.-P. (2010). Cryst. Growth Des. 10, 4906–4919. CSD CrossRef CAS Google Scholar
Pradeesh, K., Rao, K. N. & Prakash, G. V. (2013). J. Appl. Phys. 113, 083523–9. Web of Science CrossRef Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sourisseau, S., Louvain, N., Bi, W., Mercier, N., Rondeau, D., Boucher, F., Buzaré, J.-Y. & Legein, C. (2007). Chem. Mater. 19, 600–607. Web of Science CSD CrossRef CAS Google Scholar
Takahashi, Y., Obara, R., Nakagawa, K., Nakano, M., Tokita, J. & Inabe, T. (2007). Chem. Mater. 19, 6312–6316. Web of Science CSD CrossRef CAS Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Zhengtao, X., Mitzi, D. B., Dimitrakopoulos, C. D. & Maxcy, K. R. (2003b). Inorg. Chem. 42, 2031–2039. Web of Science PubMed Google Scholar
Zhengtao, X., Mitzi, D. B. & Medeiros, D. R. (2003a). Inorg. Chem. 42, 1400–1402. Web of Science PubMed Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.