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Syntheses and crystal structures of the quaternary thio­germanates Cu4FeGe2S7 and Cu4CoGe2S7

aDepartment of Chemistry and Biochemistry, Duquesne University, 600 Forbes Ave, Pittsburgh PA 15282, USA
*Correspondence e-mail: aitkenj@duq.edu

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 27 May 2020; accepted 10 June 2020; online 19 June 2020)

The quaternary thio­germanates Cu4FeGe2S7 (tetra­copper iron digermanium hepta­sulfide) and Cu4CoGe2S7 (tetra­copper cobalt digermanium hepta­sulfide) were prepared in evacuated fused-silica ampoules via high-temperature, solid-state synthesis using stoichiometric amounts of the elements at 1273 K. These isostructural compounds crystallize in the Cu4NiSi2S7 structure type, which can be considered as a superstructure of cubic diamond or sphalerite. The monovalent (Cu+), divalent (Fe2+ or Co2+) and tetra­valent (Ge4+) cations adopt tetra­hedral geometries, each being surrounded by four S2− anions. The divalent cation and one of the sulfide ions lie on crystallographic twofold axes. These tetra­hedra share corners to create a three-dimensional framework structure. All of the tetra­hedra align along the same crystallographic direction, rendering the structure non-centrosymmetric and polar (space group C2). Analysis of X-ray powder diffraction data revealed that the structures are the major phase of the reaction products. Thermal analysis indicated relatively high melting temperatures, near 1273 K.

1. Chemical context

The title compounds belong to the family of quaternary thio­germanates, which can be constructed from different [GexSy]z- building blocks, such as [GeS4]4− (Aitken et al., 2001[Aitken, J. A., Larson, P., Mahanti, S. D. & Kanatzidis, M. G. (2001). Chem. Mater. 13, 4714-4721.]) and [Ge2S6]4− (Choudhury et al., 2015[Choudhury, A., Ghosh, K., Grandjean, F., Long, G. J. & Dorhout, P. K. (2015). J. Solid State Chem. 226, 74-80.]). Two GeS4 tetra­hedra can share a corner to create [Ge2S7]6− units, which are featured in the title compounds. Cu4FeGe2S7 and Cu4CoGe2S7 also belong to the family of diamond-like semiconductors (DLSs), with structures that can be derived from the cubic or hexa­gonal (Frondel & Marvin, 1967[Frondel, C. & Marvin, U. B. (1967). Nature, 214, 587-589.]) forms of diamond. The synthesis of new diamond-like materials is guided by valence electron principles and Pauling's rules, and the resulting DLSs can be binary, ternary, or quaternary, depending on the number of elements employed in the reaction (Parthé, 1964[Parthé, E. (1964). Crystal Chemistry of Tetrahedral Structures. New York: Gordon and Breach Science Publishers.]; Pamplin, 1981[Pamplin, B. (1981). Prog. Crystl. Growth Charact. 3, 179-192.]; Goryunova, 1965[Goryunova, N. A. (1965). The Chemistry of Diamond-like Semiconductors. Cambridge, MA: Massachusetts Institute of Technology.]). Increasing the number of elements in the formula allows for greater tunability of the material's properties; thus, quaternary DLSs are a particularly appealing class of materials. As a result of their technologic­ally relevant properties, these materials are of inter­est for a number of applications, such as solar cells (Ito & Nakazawa, 1988[Ito, K. & Nakazawa, T. (1988). Jpn. J. Appl. Phys. 27, 2094-2097.]; Heppke et al., 2020[Heppke, E. M., Berendts, S. & Lerch, M. (2020). Z. Naturforsch. Teil B, 75, 393-402.]; Liu et al., 2018[Liu, Q., Cai, Z., Han, D. & Chen, S. (2018). Sci. Rep. 8, 1604.]), batteries (Brant, Devlin et al., 2015[Brant, J. A., Devlin, K. P., Bischoff, C., Watson, D., Martin, S. W., Gross, M. D. & Aitken, J. A. (2015). Solid State Ionics, 278, 268-274.]; Kaib et al., 2013[Kaib, T., Haddadpour, S., Andersen, H. F., Mayrhofer, L., Järvi, T. T., Moseler, M., Möller, K.-C. & Dehnen, S. (2013). Adv. Funct. Mater. 23, 5693-5699.]) and magnetic devices (Wintenberger, 1979[Wintenberger, M. (1979). Mater. Res. Bull. 14, 1195-1202.]; Greenwood & Whitfield, 1968[Greenwood, N. N. & Whitfield, H. J. (1968). J. Chem. Soc. A, pp. 1697-1699.]). Furthermore, owing to their inherently non-centrosymmetric structures, DLSs are attractive candidates for infrared non-linear optical (IR–NLO) devices that make use of second-harmonic generation (SHG) crystals (Ohmer & Pandey 1998[Ohmer, M. C. & Pandey, R. (1998). MRS Bull. 23, 16-22.]): only crystals that lack an inversion center can exhibit SHG.

IR–NLO materials are used to shift the radiation of lasers to more suitable wavelengths for use in military (Hopkins 1998[Hopkins, F. K. (1998). Opt. Photonics News, 9, 32-38.]), medical (Stoeppler et al., 2012[Stoeppler, G., Schellhorn, M. & Eichhorn, M. (2012). Laser Phys. 22, 1095-1098.]) and industrial applications (Bamford et al., 2007[Bamford, D. J., Cook, D. J., Sharpe, S. J. & Van Pelt, A. D. (2007). Appl. Opt. 46, 3958-3968.]). Currently, ternary DLSs, most of which are sulfides, dominate the market of SHG crystals for use in the infrared (Ohmer & Pandey, 1998[Ohmer, M. C. & Pandey, R. (1998). MRS Bull. 23, 16-22.]). Yet the current commercially available IR–NLO materials suffer from serious drawbacks, such as low laser-induced damage thresholds (LIDTs) and multi-photon absorption (Schunemann, 2007[Schunemann, P. G. (2007). Proc. SPIE, 6455, 64550R.]). Turning attention to the discovery of new quaternary DLSs provides a reliable route to next-generation IR–NLO materials that allows for greater control of the material's properties. Compounds such as Li2CdGeS4 (Brant, Clark et al., 2014[Brant, J. A., Clark, D. J., Kim, Y. S., Jang, J. I., Zhang, J.-H. & Aitken, J. A. (2014). Chem. Mater. 26, 3045-3048.]), Li2MnGeS4 (Brant, Clark et al., 2015[Brant, J. A., Clark, D. J., Kim, Y. S., Jang, J. I., Weiland, A. & Aitken, J. A. (2015). Inorg. Chem. 54, 2809-2819.]), and Li4HgGe2S7 (Wu, Yang & Pan, 2017[Wu, K., Yang, Z. & Pan, S. (2017). Chem. Commun. 53, 3010-3013.]) have shown potential to outperform currently used ternary IR–NLO crystals. These DLSs have shown promising SHG capabilities, as well as resilience to high powered lasers, a necessity to broaden future usage (Hopkins, 1998[Hopkins, F. K. (1998). Opt. Photonics News, 9, 32-38.]). For these reasons, we were motivated to investigate the Cu–Fe–Ge–S and Cu–Co–Ge–S systems for new DLSs.

2. Structural commentary

The title compounds, Cu4FeGe2S7 (I) and Cu4CoGe2S7 (II), are isostructural and crystallize in the non-centrosymmetric, monoclinic space group C2 (No. 5) with the Cu4NiSi2S7 structure type (Schäfer et al., 1980[Schäfer, W., Scheunemann, K. & Nitsche, R. (1980). Mater. Res. Bull. 15, 933-937.]). The structure contains two crystallographically unique Cu+ ions, one divalent metal (Fe or Co) sited on a crystallographic twofold axis, one Ge4+ cation and four S2− anions (one with site symmetry 2) (Fig. 1[link]). The sulfide anions create a `cubic' close-packed array and the cations reside in one-half of the tetra­hedral holes; these tetra­hedra share corners to form a three-dimensional network. Two GeS4 tetra­hedra share corners to form (Ge2S7)6− subunits that are isolated from each other (Fig. 1[link]). These subunits are separated by isolated FeS4 tetra­hedra and surrounded by a snaking, three-dimensional network of corner-sharing CuS4 tetra­hedra that serve to link the (Ge2S7)6− and FeS4 subunits. All of the tetra­hedra are aligned along one crystallographic direction, rendering the structure non-centrosymmetric (Fig. 2[link]). All DLSs exhibit a honeycomb pattern in their crystal structure (Fig. 3[link]); the various resulting space groups arise from the different possible cation-ordering patterns.

[Figure 1]
Figure 1
The structure of Cu4FeGe2S7 with crystallographically unique ions labeled. Ellipsoids are shown at 99% probability. Cu4CoGe2S7 is isostructural and has similar atomic displacement parameters.
[Figure 2]
Figure 2
Polyhedral view of Cu4FeGe2S7 showing the polar nature of the structure.
[Figure 3]
Figure 3
The `honeycomb' pattern found in Cu4FeGe2S7, a characteristic of DLSs. Highlighted in the bottom left corner is one of the [Ge2S7]6− subunits that forms in this structure.

Selected geometrical data for (I) and (II) are given in Tables 1[link] and 2[link], respectively. The average Fe—S (I) and Co—S (II) bond distances are 2.334 (6) and 2.317 (6) Å, respectively. These values align well with other compounds containing iron or cobalt tetra­hedrally coordinated by sulfur. For example, the average Fe—S distance found in Li2FeGeS4 is 2.34 (2) Å (Brant, dela Cruz et al., 2014[Brant, J. A., dela Cruz, C., Yao, J., Douvalis, A. P., Bakas, T., Sorescu, M. & Aitken, J. A. (2014). Inorg. Chem. 53, 12265-12274.]), while the average Co—S distance found in Li2CoGeS4 is 2.31 (3) Å (Brant, Devlin et al., 2015[Brant, J. A., Devlin, K. P., Bischoff, C., Watson, D., Martin, S. W., Gross, M. D. & Aitken, J. A. (2015). Solid State Ionics, 278, 268-274.]). The average Ge—S distances are 2.240 (4) and 2.244 (5) Å for (I) and (II), respectively. These distances are also close to those of the lithium-containing DLSs: Li2FeGeS4 (Brant, Devlin et al., 2015[Brant, J. A., Devlin, K. P., Bischoff, C., Watson, D., Martin, S. W., Gross, M. D. & Aitken, J. A. (2015). Solid State Ionics, 278, 268-274.]) and Li2CoGeS4 (Brant, dela Cruz et al., 2014[Brant, J. A., dela Cruz, C., Yao, J., Douvalis, A. P., Bakas, T., Sorescu, M. & Aitken, J. A. (2014). Inorg. Chem. 53, 12265-12274.]) possess values of 2.23 (2) and 2.22 (3) Å, respectively. The average tetra­hedral bond angles for all cations in both title compounds is, within uncertainty, ideal. For comparison, the tetra­hedral angular ranges encountered in Cu2FeGeS4 (Wintenberger, 1979[Wintenberger, M. (1979). Mater. Res. Bull. 14, 1195-1202.]) and Cu2CoGeS4 (Gulay et al., 2004[Gulay, L. D., Nazarchuk, O. P. & Olekseyuk, I. D. (2004). J. Alloys Compd. 377, 306-311.]) are 109.471–109.484° and 109.473–109.579°, respectively. The sulfur anions also exhibit tetra­hedral coordination. Both S2 and S4 are coordinated by two copper, one germanium and one iron or cobalt cation. S1 is connected to two germanium and two copper cations, while S3 is surrounded by one germanium and three copper cations.

Table 1
Selected bond lengths (Å) for (I)

Cu1—S3i 2.290 (2) Fe—S4v 2.331 (3)
Cu1—S3 2.302 (2) Fe—S4 2.331 (3)
Cu1—S2ii 2.303 (2) Fe—S2iv 2.337 (3)
Cu1—S1iii 2.353 (2) Fe—S2vi 2.337 (3)
Cu2—S3 2.294 (2) Ge—S3vii 2.196 (2)
Cu2—S2 2.309 (2) Ge—S2 2.221 (2)
Cu2—S4iv 2.309 (2) Ge—S4iii 2.233 (2)
Cu2—S4 2.319 (2) Ge—S1iii 2.3107 (19)
Symmetry codes: (i) [-x+{\script{3\over 2}}, y-{\script{1\over 2}}, -z+2]; (ii) x, y-1, z; (iii) [x-{\script{1\over 2}}, y-{\script{1\over 2}}, z]; (iv) [-x+{\script{3\over 2}}, y-{\script{1\over 2}}, -z+1]; (v) -x+2, y, -z+1; (vi) [x+{\script{1\over 2}}, y-{\script{1\over 2}}, z]; (vii) [x-{\script{1\over 2}}, y+{\script{1\over 2}}, z].

Table 2
Selected bond lengths (Å) for (II)

Cu1—S3i 2.292 (2) Co—S4v 2.308 (3)
Cu1—S2ii 2.295 (2) Co—S4 2.308 (3)
Cu1—S3 2.304 (2) Co—S2iv 2.325 (3)
Cu1—S1iii 2.343 (3) Co—S2vi 2.325 (3)
Cu2—S3 2.290 (2) Ge—S2 2.211 (3)
Cu2—S2 2.298 (3) Ge—S3vii 2.211 (2)
Cu2—S4iv 2.301 (2) Ge—S4iii 2.236 (2)
Cu2—S4 2.311 (2) Ge—S1iii 2.316 (2)
Symmetry codes: (i) [-x+{\script{3\over 2}}, y-{\script{1\over 2}}, -z+2]; (ii) x, y-1, z; (iii) [x-{\script{1\over 2}}, y-{\script{1\over 2}}, z]; (iv) [-x+{\script{3\over 2}}, y-{\script{1\over 2}}, -z+1]; (v) -x+2, y, -z+1; (vi) [x+{\script{1\over 2}}, y-{\script{1\over 2}}, z]; (vii) [x-{\script{1\over 2}}, y+{\script{1\over 2}}, z].

3. Database survey

Quaternary DLSs exist with several different formulae; examples that incorporate chalcogenides as the anion are I–II2–III–VI4, I2–II–IV–VI4, and I4–II–IV2–VI7. In these formulae, the Roman numerals represent the number of valence electrons for each element. Compounds of the formula I–II2–III–VI4, such as CuMn2InS4 (Delgado & Sagredo, 2016[Delgado, G. E. & Sagredo, V. (2016). Bull. Mater. Sci. 39, 1631-1634.]) and CuFe2InSe4 (Delgado et al., 2008[Delgado, G. E., Mora, A. J., Grima-Gallardo, P. & Quintero, M. (2008). J. Alloys Compd. 454, 306-309.]) include trivalent elements, while the other relevant formulae mentioned above, including the title compounds, contain tetra­valent elements. Numerous DLSs of the general formula I2–II–IV–VI4 have been reported and crystallize in non-centrosymmetric space groups, such as I[\overline{4}]2m and Pmn21 with the stannite and wurtz-stannite structure types that are derived from the cubic and hexa­gonal diamond structures, respectively (Brunetta et al., 2013[Brunetta, C. D., Brant, J. A., Rosmus, K. A., Henline, K. M., Karey, E., MacNeil, J. H. & Aitken, J. A. (2013). J. Alloys Compd. 574, 495-503.]). The monovalent ions incorporated in these materials include Li (Wu, Zhang, et al., 2017[Wu, K., Zhang, B., Yang, Z. & Pan, S. (2017). J. Am. Chem. Soc. 139, 14885-14888.]; Wu & Pan, 2017[Wu, K. & Pan, S. (2017). Crystals, 7, 107.]), Cu (Parthé et al., 1969[Parthé, E., Yvon, K. & Deitch, R. H. (1969). Acta Cryst. B25, 1164-1174.]) or Ag (Brunetta et al., 2013[Brunetta, C. D., Brant, J. A., Rosmus, K. A., Henline, K. M., Karey, E., MacNeil, J. H. & Aitken, J. A. (2013). J. Alloys Compd. 574, 495-503.]) and the divalent ions include a number of metals, such as Mg (Liu et al., 2013[Liu, B.-W., Zhang, M.-J., Zhao, Z., Zeng, H.-Y., Zheng, F.-K., Guo, G.-C. & Huang, J.-S. (2013). J. Solid State Chem. 204, 251-256.]), Mn (Bernert & Pfitzner, 2005[Bernert, T. & Pfitzner, A. (2005). Z. Kristallogr. 220, 968-972.]), Fe (Wintenberger, 1979[Wintenberger, M. (1979). Mater. Res. Bull. 14, 1195-1202.]), Co (Bernert and Pfitzner 2006[Bernert, T. & Pfitzner, A. (2006). Z. Anorg. Allg. Chem. 632, 1213-1218.]), Zn (Parasyuk et al., 2001[Parasyuk, O. V., Gulay, L. D., Romanyuk, Y. E. & Piskach, L. V. (2001). J. Alloys Compd. 329, 202-207.]), Cd (Rosmus et al., 2014[Rosmus, K. A., Brant, J. A., Wisneski, S. D., Clark, D. J., Kim, Y. S., Jang, J. I., Brunetta, C. D., Zhang, J.-H., Srnec, M. N. & Aitken, J. A. (2014). Inorg. Chem. 53, 7809-7811.]) and Hg (Olekseyuk et al., 2005[Olekseyuk, I. D., Marchuk, O. V., Gulay, L. D. & Zhbankov, O. Y. (2005). J. Alloys Compd. 398, 80-84.]). The tetra­valent ions found in these compounds are usually Si, Ge, or Sn, while the hexa­valent atoms (i.e., the divalent anions) can be S (Lekse et al., 2009[Lekse, J. W., Moreau, M. A., McNerny, K. L., Yeon, J., Halasyamani, P. S. & Aitken, J. A. (2009). Inorg. Chem. 48, 7516-7518.]), Se (Gulay, Romanyuk & Parasyuk, 2002[Gulay, L. D., Romanyuk, Y. E. & Parasyuk, O. V. (2002). J. Alloys Compd. 347, 193-197.]), or Te (Parasyuk et al., 2005[Parasyuk, O. V., Olekseyuk, I. D. & Piskach, L. V. (2005). J. Alloys Compd. 397, 169-172.]). Some specific examples include Cu2MgGeS4 (Liu et al., 2013[Liu, B.-W., Zhang, M.-J., Zhao, Z., Zeng, H.-Y., Zheng, F.-K., Guo, G.-C. & Huang, J.-S. (2013). J. Solid State Chem. 204, 251-256.]) and Ag2MnSnS4 (Friedrich et al., 2018[Friedrich, D., Greil, S., Block, T., Heletta, L., Pöttgen, R. & Pfitzner, A. (2018). Z. Anorg. Allg. Chem. 644, 1707-1714.]).

In contrast, considerably fewer compounds of the general formula I4–II–IV2–VI7 have been discovered: only seven of these, which crystallize in either space group C2 or Cc with structures derived from cubic or hexa­gonal diamond, respectively, have been published to date: Li4MnGe2S7 (Cc) (Kaib et al., 2013[Kaib, T., Haddadpour, S., Andersen, H. F., Mayrhofer, L., Järvi, T. T., Moseler, M., Möller, K.-C. & Dehnen, S. (2013). Adv. Funct. Mater. 23, 5693-5699.]), Li4MnSn2Se7 (Cc) (Kaib et al., 2013[Kaib, T., Haddadpour, S., Andersen, H. F., Mayrhofer, L., Järvi, T. T., Moseler, M., Möller, K.-C. & Dehnen, S. (2013). Adv. Funct. Mater. 23, 5693-5699.]), Li4HgGe2S7 (Cc) (Wu, Yang, Pan 2017[Wu, K., Yang, Z. & Pan, S. (2017). Chem. Commun. 53, 3010-3013.]), Ag4HgGe2S7 (Cc) (Gulay, Olekseyuk & Parasyuk 2002[Gulay, L. D., Olekseyuk, I. D. & Parasyuk, O. V. (2002). J. Alloys Compd. 340, 157-166.]), Ag4CdGe2S7 (Cc) (Gulay, Olekseyuk & Parasyuk 2002[Gulay, L. D., Olekseyuk, I. D. & Parasyuk, O. V. (2002). J. Alloys Compd. 340, 157-166.]), Cu4NiSi2S7 (C2) (Schäfer et al., 1980[Schäfer, W., Scheunemann, K. & Nitsche, R. (1980). Mater. Res. Bull. 15, 933-937.]), and Cu4NiGe2S7 (C2) (Schäfer et al., 1980[Schäfer, W., Scheunemann, K. & Nitsche, R. (1980). Mater. Res. Bull. 15, 933-937.]).

4. X-ray powder diffraction and thermal analysis

The calculated and observed X-ray powder diffraction patterns match well (Fig. 4[link]), indicating that the title compounds are the major phases of the respective reactions. An optimization of the synthetic protocol is needed to isolate the desired phases in phase-pure form.

[Figure 4]
Figure 4
Comparison of experimental X-ray powder diffraction patterns before and after DTA with those calculated using the single-crystal structures for Cu4FeGe2S7 (left) and Cu4CoGe2S7 (right).

Differential thermal analysis (DTA) reveals that Cu4FeGe2S7 and Cu4CoGe2S7 show relatively high thermal stability and melting and recrystallization events with appropriate hysteresis around 1000°C (Fig. 5[link]). Multiple heating-cooling cycles for each sample were consistent, suggesting that the thermal events are reversible. X-ray powder diffraction of the DTA residues indicated that the samples were not changed by the thermal analyses, implying that they melt congruently. DTA also suggests that neither compound is a single phase, as there are some small shoulders on the peaks indicative of the thermal events.

[Figure 5]
Figure 5
Differential thermal analysis diagrams obtained for the title compounds showing the melting and recrystallization events.

5. Materials and methods

All powdered elements were acquired from commercial suppliers and used as obtained with the exception of germanium metal, which was purchased as chunks and ground to a fine powder using a Diamonite™ mortar and pestle prior to use. Powder X-ray diffraction data were recorded from 10–100° 2θ using a PANalytical X'Pert Pro MPD powder X-ray diffractometer operating with Cu Kα radiation (λ = 1.541871 Å), a tube power of 45 kV and 40 mA and a step size of 0.017°. DTA data were obtained using a Shimadzu DTA50 thermal analyzer. Each sample was vacuum-sealed in a fused-silica ampoule, placed alongside an ampoule containing an Al2O3 reference of comparable mass, heated from room temperature to 1050°C at a rate of 10°C min−1 and subsequently cooled to room temperature at the same rate. A second heating–cooling cycle was conducted in order to determine the reproducibility of the thermal events.

6. Synthesis and crystallization

Cu4FeGe2S7 and Cu4CoGe2S7 were synthesized by combining stoichiometric amounts of Cu (99.999%), Fe (99.99%) or Co (99.99%), Ge (99.999%) and S (99.5%, sublimed) powders. The powders were mixed and placed into 12 mm o.d. fused-silica tubes that were subsequently attached to a vacuum line, evacuated and flame sealed. The reaction vessels were placed upright into ceramic containers inside programmable furnaces, where they were heated to 1000°C in 24 h, held there for 48 h, cooled to 900°C over the course of 50 h, and held there for 96 h, before being allowed to cool to room temperature over a 24 h period. Subsequently, the reaction vessels were cut open and the contents were examined under a light microscope. The products consisted of loose silvery gray microcrystalline powders from which small single crystals were selected for single-crystal X-ray diffraction.

7. Refinement

Crystal data, data collection parameters, and structure refinement details are summarized in Table 3[link]. Extinction parameters were refined for each compound. After the final refinement, the Flack parameter for both structures refined to 0.06 (3), indicating that the absolute structure is correct. In Cu4FeGe2S7, the largest difference peak is located 1.15 Å from Cu2 while the deepest difference hole is 1.50 Å from S3. For Cu4CoGe2S7, the largest difference peak is 0.67 Å from Co while the deepest difference hole is 0.83 Å from Ge.

Table 3
Experimental details

  (I) (II)
Crystal data
Chemical formula Cu4FeGe2S7 Cu4CoGe2S7
Mr 679.61 682.69
Crystal system, space group Monoclinic, C2 Monoclinic, C2
Temperature (K) 296 296
a, b, c (Å) 11.7405 (6), 5.3589 (2), 8.3420 (4) 11.7280 (2), 5.33987 (10), 8.33133 (14)
β (°) 98.661 (3) 98.6680 (12)
V3) 518.86 (4) 515.80 (2)
Z 2 2
Radiation type Mo Kα Mo Kα
μ (mm−1) 16.46 16.76
Crystal size (mm) 0.08 × 0.08 × 0.03 0.08 × 0.07 × 0.06
 
Data collection
Diffractometer Bruker SMART APEXII Bruker SMART APEXII
Absorption correction Multi-scan (SADABS; Sheldrick, 2002[Sheldrick, G. M. (2002). SADABS. University of Göttingen, Germany.]) Multi-scan (SADABS; Sheldrick, 2002[Sheldrick, G. M. (2002). SADABS. University of Göttingen, Germany.])
Tmin, Tmax 0.246, 0.435 0.356, 0.435
No. of measured, independent and observed [I > 2σ(I)] reflections 2258, 1187, 994 2239, 1177, 1039
Rint 0.021 0.017
(sin θ/λ)max−1) 0.649 0.649
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.034, 0.094, 1.06 0.030, 0.075, 1.11
No. of reflections 1187 1177
No. of parameters 67 67
No. of restraints 1 1
Δρmax, Δρmin (e Å−3) 0.75, −0.89 0.88, −0.49
Absolute structure Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]) Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.])
Absolute structure parameter 0.06 (3) 0.06 (3)
Computer programs: SMART and SAINT (Bruker, 1998[Bruker (1998). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2018/3 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]) and CrystalMaker (Palmer, 2014[Palmer, D. C. (2014). CrystalMaker. CrystalMaker Software Ltd, Begbroke, Oxfordshire, England.]).

Supporting information


Computing details top

For both structures, data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015); molecular graphics: CrystalMaker (Palmer, 2014); software used to prepare material for publication: SHELXL2018/3 (Sheldrick, 2015).

Tetracopper iron digermanium heptasulfide (I) top
Crystal data top
Cu4FeGe2S7F(000) = 636
Mr = 679.61Dx = 4.350 Mg m3
Monoclinic, C2Mo Kα radiation, λ = 0.71073 Å
a = 11.7405 (6) ÅCell parameters from 4891 reflections
b = 5.3589 (2) Åθ = 4.2–31.4°
c = 8.3420 (4) ŵ = 16.46 mm1
β = 98.661 (3)°T = 296 K
V = 518.86 (4) Å3Irregular, grey
Z = 20.08 × 0.08 × 0.03 mm
Data collection top
Bruker SMART APEXII
diffractometer
994 reflections with I > 2σ(I)
φ and ω Scans scansRint = 0.021
Absorption correction: multi-scan
(SADABS; Sheldrick, 2002)
θmax = 27.5°, θmin = 2.5°
Tmin = 0.246, Tmax = 0.435h = 1515
2258 measured reflectionsk = 66
1187 independent reflectionsl = 1010
Refinement top
Refinement on F2 w = 1/[σ2(Fo2) + (0.0315P)2]
where P = (Fo2 + 2Fc2)/3
Least-squares matrix: full(Δ/σ)max < 0.001
R[F2 > 2σ(F2)] = 0.034Δρmax = 0.75 e Å3
wR(F2) = 0.094Δρmin = 0.89 e Å3
S = 1.06Extinction correction: SHELXL-2018/3 (Sheldrick 2018), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1187 reflectionsExtinction coefficient: 0.0123 (9)
67 parametersAbsolute structure: Flack (1983)
1 restraintAbsolute structure parameter: 0.06 (3)
Primary atom site location: structure-invariant direct methods
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refined as a two-component inversion twin

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cu10.64298 (8)0.2054 (3)0.93484 (11)0.0174 (7)
Cu20.71147 (8)0.7098 (2)0.64229 (10)0.0165 (6)
Fe1.0000000.7200 (6)0.5000000.0112 (6)
Ge0.42524 (6)0.7285 (3)0.78371 (7)0.0092 (3)
S11.0000000.9789 (6)1.0000000.0091 (6)
S20.56834 (15)0.9593 (5)0.71791 (18)0.0111 (6)
S30.78390 (14)0.4527 (4)0.85310 (17)0.0091 (6)
S40.85688 (15)0.9704 (5)0.58180 (19)0.0101 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0171 (6)0.0169 (15)0.0184 (6)0.0019 (5)0.0032 (4)0.0025 (5)
Cu20.0171 (6)0.0142 (13)0.0185 (6)0.0005 (8)0.0037 (4)0.0017 (4)
Fe0.0115 (8)0.0137 (17)0.0093 (7)0.0000.0041 (6)0.000
Ge0.0080 (5)0.0100 (8)0.0096 (5)0.0009 (8)0.0018 (3)0.0007 (4)
S10.0095 (13)0.0093 (16)0.0087 (11)0.0000.0014 (9)0.000
S20.0089 (11)0.0128 (15)0.0120 (9)0.0029 (10)0.0030 (7)0.0009 (9)
S30.0081 (11)0.0076 (14)0.0122 (9)0.0004 (8)0.0033 (8)0.0003 (8)
S40.0101 (10)0.0094 (13)0.0107 (9)0.0012 (7)0.0010 (7)0.0004 (10)
Geometric parameters (Å, º) top
Cu1—S3i2.290 (2)Fe—S4v2.331 (3)
Cu1—S32.302 (2)Fe—S42.331 (3)
Cu1—S2ii2.303 (2)Fe—S2iv2.337 (3)
Cu1—S1iii2.353 (2)Fe—S2vi2.337 (3)
Cu2—S32.294 (2)Ge—S3vii2.196 (2)
Cu2—S22.309 (2)Ge—S22.221 (2)
Cu2—S4iv2.309 (2)Ge—S4iii2.233 (2)
Cu2—S42.319 (2)Ge—S1iii2.3107 (19)
S3i—Cu1—S3111.52 (5)Geviii—S1—Geix109.23 (13)
S3i—Cu1—S2ii108.81 (12)Geviii—S1—Cu1viii112.37 (4)
S3—Cu1—S2ii107.60 (6)Geix—S1—Cu1viii109.92 (4)
S3i—Cu1—S1iii112.79 (6)Geviii—S1—Cu1ix109.92 (4)
S3—Cu1—S1iii106.23 (13)Geix—S1—Cu1ix112.37 (4)
S2ii—Cu1—S1iii109.75 (6)Cu1viii—S1—Cu1ix102.96 (15)
S3—Cu2—S2109.84 (6)Ge—S2—Cu1x109.71 (8)
S3—Cu2—S4iv109.30 (11)Ge—S2—Cu2110.72 (12)
S2—Cu2—S4iv111.38 (6)Cu1x—S2—Cu2109.87 (7)
S3—Cu2—S4109.17 (7)Ge—S2—Fevii109.96 (9)
S2—Cu2—S4107.49 (11)Cu1x—S2—Fevii108.33 (14)
S4iv—Cu2—S4109.62 (5)Cu2—S2—Fevii108.21 (7)
S4v—Fe—S4109.72 (19)Gevi—S3—Cu1viii108.48 (7)
S4v—Fe—S2iv107.13 (6)Gevi—S3—Cu2109.52 (7)
S4—Fe—S2iv113.18 (6)Cu1viii—S3—Cu2106.84 (11)
S4v—Fe—S2vi113.18 (6)Gevi—S3—Cu1111.62 (11)
S4—Fe—S2vi107.13 (6)Cu1viii—S3—Cu1108.31 (7)
S2iv—Fe—S2vi106.58 (17)Cu2—S3—Cu1111.89 (8)
S3vii—Ge—S2112.97 (13)Geix—S4—Cu2xi107.94 (11)
S3vii—Ge—S4iii109.74 (6)Geix—S4—Cu2113.68 (8)
S2—Ge—S4iii110.97 (6)Cu2xi—S4—Cu2109.46 (7)
S3vii—Ge—S1iii108.92 (5)Geix—S4—Fe112.60 (9)
S2—Ge—S1iii107.64 (6)Cu2xi—S4—Fe105.12 (7)
S4iii—Ge—S1iii106.34 (12)Cu2—S4—Fe107.68 (14)
Symmetry codes: (i) x+3/2, y1/2, z+2; (ii) x, y1, z; (iii) x1/2, y1/2, z; (iv) x+3/2, y1/2, z+1; (v) x+2, y, z+1; (vi) x+1/2, y1/2, z; (vii) x1/2, y+1/2, z; (viii) x+3/2, y+1/2, z+2; (ix) x+1/2, y+1/2, z; (x) x, y+1, z; (xi) x+3/2, y+1/2, z+1.
Tetracopper cobalt digermanium heptasulfide (II) top
Crystal data top
Cu4CoGe2S7F(000) = 638
Mr = 682.69Dx = 4.396 Mg m3
Monoclinic, C2Mo Kα radiation, λ = 0.71073 Å
a = 11.7280 (2) ÅCell parameters from 4827 reflections
b = 5.33987 (10) Åθ = 4.2–32.6°
c = 8.33133 (14) ŵ = 16.76 mm1
β = 98.6680 (12)°T = 296 K
V = 515.80 (2) Å3Irregular, grey
Z = 20.08 × 0.07 × 0.06 mm
Data collection top
Bruker SMART APEXII
diffractometer
1039 reflections with I > 2σ(I)
φ and ω Scans scansRint = 0.017
Absorption correction: multi-scan
(SADABS; Sheldrick, 2002)
θmax = 27.5°, θmin = 2.5°
Tmin = 0.356, Tmax = 0.435h = 1515
2239 measured reflectionsk = 66
1177 independent reflectionsl = 1010
Refinement top
Refinement on F2 w = 1/[σ2(Fo2) + 3.9921P]
where P = (Fo2 + 2Fc2)/3
Least-squares matrix: full(Δ/σ)max < 0.001
R[F2 > 2σ(F2)] = 0.030Δρmax = 0.88 e Å3
wR(F2) = 0.075Δρmin = 0.49 e Å3
S = 1.11Extinction correction: SHELXL2018/3 (Sheldrick 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1177 reflectionsExtinction coefficient: 0.060 (3)
67 parametersAbsolute structure: Flack (1983)
1 restraintAbsolute structure parameter: 0.06 (3)
Primary atom site location: structure-invariant direct methods
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refined as a two-component inversion twin

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cu10.64303 (9)0.2051 (4)0.93412 (12)0.0177 (7)
Cu20.71154 (9)0.7108 (2)0.64143 (12)0.0158 (6)
Co1.0000000.7206 (7)0.5000000.0141 (8)
Ge0.42703 (6)0.7276 (4)0.78209 (9)0.0092 (4)
S11.0000000.9762 (6)1.0000000.0090 (6)
S20.56898 (15)0.9604 (5)0.7167 (2)0.0118 (6)
S30.78425 (15)0.4533 (4)0.8520 (2)0.0092 (6)
S40.85742 (15)0.9682 (5)0.5803 (2)0.0094 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0181 (6)0.0182 (18)0.0167 (6)0.0026 (5)0.0023 (4)0.0018 (6)
Cu20.0168 (6)0.0131 (14)0.0175 (6)0.0004 (8)0.0029 (4)0.0014 (6)
Co0.0118 (7)0.021 (2)0.0096 (7)0.0000.0028 (5)0.000
Ge0.0090 (5)0.0100 (9)0.0086 (5)0.0011 (7)0.0012 (3)0.0019 (6)
S10.0102 (12)0.0092 (18)0.0072 (11)0.0000.0001 (9)0.000
S20.0101 (9)0.0160 (15)0.0097 (9)0.0022 (11)0.0028 (7)0.0007 (9)
S30.0095 (9)0.0076 (16)0.0109 (9)0.0012 (8)0.0025 (7)0.0017 (9)
S40.0113 (9)0.0090 (13)0.0076 (8)0.0008 (7)0.0008 (7)0.0012 (10)
Geometric parameters (Å, º) top
Cu1—S3i2.292 (2)Co—S4v2.308 (3)
Cu1—S2ii2.295 (2)Co—S42.308 (3)
Cu1—S32.304 (2)Co—S2iv2.325 (3)
Cu1—S1iii2.343 (3)Co—S2vi2.325 (3)
Cu2—S32.290 (2)Ge—S22.211 (3)
Cu2—S22.298 (3)Ge—S3vii2.211 (2)
Cu2—S4iv2.301 (2)Ge—S4iii2.236 (2)
Cu2—S42.311 (2)Ge—S1iii2.316 (2)
S3i—Cu1—S2ii109.37 (12)Geviii—S1—Geix109.14 (15)
S3i—Cu1—S3111.62 (6)Geviii—S1—Cu1viii111.56 (4)
S2ii—Cu1—S3107.25 (7)Geix—S1—Cu1viii110.41 (4)
S3i—Cu1—S1iii112.08 (6)Geviii—S1—Cu1ix110.41 (4)
S2ii—Cu1—S1iii109.73 (7)Geix—S1—Cu1ix111.56 (4)
S3—Cu1—S1iii106.65 (13)Cu1viii—S1—Cu1ix103.68 (17)
S3—Cu2—S2109.96 (7)Ge—S2—Cu1x109.59 (8)
S3—Cu2—S4iv108.79 (11)Ge—S2—Cu2110.30 (13)
S2—Cu2—S4iv111.31 (7)Cu1x—S2—Cu2109.95 (8)
S3—Cu2—S4108.88 (8)Ge—S2—Covii109.91 (9)
S2—Cu2—S4107.97 (11)Cu1x—S2—Covii108.57 (14)
S4iv—Cu2—S4109.90 (5)Cu2—S2—Covii108.48 (8)
S4v—Co—S4110.11 (19)Gevi—S3—Cu2109.57 (8)
S4v—Co—S2iv107.45 (6)Gevi—S3—Cu1viii108.46 (8)
S4—Co—S2iv112.63 (7)Cu2—S3—Cu1viii107.17 (11)
S4v—Co—S2vi112.63 (7)Gevi—S3—Cu1111.81 (11)
S4—Co—S2vi107.45 (6)Cu2—S3—Cu1111.81 (8)
S2iv—Co—S2vi106.59 (18)Cu1viii—S3—Cu1107.84 (7)
S2—Ge—S3vii112.75 (14)Geix—S4—Cu2xi107.42 (11)
S2—Ge—S4iii111.49 (7)Geix—S4—Co111.98 (10)
S3vii—Ge—S4iii109.30 (7)Cu2xi—S4—Co105.80 (7)
S2—Ge—S1iii108.43 (7)Geix—S4—Cu2113.66 (9)
S3vii—Ge—S1iii108.34 (6)Cu2xi—S4—Cu2109.24 (7)
S4iii—Ge—S1iii106.29 (12)Co—S4—Cu2108.42 (14)
Symmetry codes: (i) x+3/2, y1/2, z+2; (ii) x, y1, z; (iii) x1/2, y1/2, z; (iv) x+3/2, y1/2, z+1; (v) x+2, y, z+1; (vi) x+1/2, y1/2, z; (vii) x1/2, y+1/2, z; (viii) x+3/2, y+1/2, z+2; (ix) x+1/2, y+1/2, z; (x) x, y+1, z; (xi) x+3/2, y+1/2, z+1.
 

Acknowledgements

We gratefully acknowledge Mr Daniel J. Bodnar, instrument maintenance manager of the Bayer School of Natural and Environmental Sciences at Duquesne University, for keeping the diffractometers running.

Funding information

This research was supported by the National Science Foundation, Division of Materials Research under grant No. DMR-1611198. The single-crystal and powder X-ray diffractometers were purchased with funds from the National Science Foundation under grant Nos. CHE-0234872 and DUE-0511444, respectively.

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