Fifteen 4-(2-methoxyphenyl)piperazin-1-ium salts containing organic anions: supramolecular assembly in zero, one, two and three dimensions

Fifteen 4-(2-methoxyphenyl)piperazin-1-ium salts with organic anions exhibit a range of hydrogen-bonded supramolecular assemblies in the form of finite aggregates, a chain of rings, ribbons, sheets and three-dimensional networks.


Chemical context
We have recently reported the molecular and supramolecular structures of the recreational drug N-(4-methoxyphenyl)piperazine (4-MeOPP) (Kiran Kumar et al., 2020) and those of a range of salts formed by 4-MeOPP with organic acids (Kiran Kiran Kumar et al. 2020), as well as those of a number of N-aroyl derivatives (Kiran Kumar, Yathirajan, Sagar et al., 2019). We have also reported the structures of some salts of N-(4-fluorophen- ISSN 2056-9890 yl)piperazine (4-FPP) (Harish Chinthal, Yathirajan, Archana et al., 2020;Harish Chinthal, Yathirajan, Kavitha et al., 2020). As a continuation of this study, we have now investigated a number of salts of the isomeric N-(2-methoxyphenyl)piperazine (2-MeOPP), which has been used as a building block in the synthesis of both 5-HT 1A receptor ligands (Orjales et al., 1995) and dopamine D 2 and D 3 ligands (Hackling et al., 2003) and also as a building block for the synthesis of derivatives exhibiting antidepressant-like activity (Waszkielewicz et al., 2015). Here we report the syntheses and structures of the salts (I)-(XI)  formed between 2-MeOPP and eleven aromatic carboxylic acids, along with a redetermination of the salt (XII) (Fig. 12) formed with 2,4,6trinitrophenol (picric acid) where the reported structure (Verdonk et al., 1997; CSD refcode NEBGIK) shows signs of unmodelled disorder, and we report here also the structures of three acid salts (XIII)-(XV)  formed with some aliphatic dicarboxylic acids. All of the salts (I)-(XV) were straightforwardly prepared by the acid-base reactions and subsequent crystallizations of equimolar mixtures of 2-MeOPP with the appropriate organic acid.

Structural commentary
Compounds ( The independent components of compound (I) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
The independent components of compound (II) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 3
The independent components of compound (III) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 4
The independent components of compound (IV) showing the atomlabelling scheme and the disorder in the anion; the major disorder component is drawn using full lines and the minor disorder component is drawn using broken lines. Displacement ellipsoids are drawn at the 30% probability level. 0.907 (8) and 0.093 (8) (Fig. 4). There is a significant peak, 1.15 e Å À3 , in the final difference map for compound (V): it was originally thought that this might represent a partialoccupancy water molecule, although no associated H atoms could be located, but its distance from atom O32 is only 2.35 Å , which would require an unusually short O-HÁ Á ÁO hydrogen bond for this assignment to be plausible. Consistent with this, examination of the refined, solvent-free structure of (V) using PLATON (Spek, 2020) showed that the structure contains no solvent-accessible void spaces. Compounds (VI) and (VII) are isomorphous, but whereas the components of (VI) are fully ordered (Fig. 6), in (VII) the carboxylate group in the anion is disordered over two sets of atomic sites having occupancies 0.54 (9) and 0.46 (9) (Fig. 7); hence, these isomorphous compounds cannot be regarded as strictly isostructural (cf. Acosta et al., 2009;Yé pes et al., 2012;Shreekanth et al., 2020), because of the disorder in (VII). The structures of (VI) and (VII) are mutually inverse for the crystals selected for data collection, but this has no chemical significance. Compounds (VIII)-(X)  all crystallize in solvent-free form, but the 3,5-dinitrobenzoate salt (XI) is a dihydrate (Fig. 11). The structure of the picrate salt (XII) was reported a number of years ago (Verdonk et al., 1997), but the deposited anisotropic displacement parameters suggest the presence of unmodelled disorder in one of the nitro groups. The independent components of compound (V) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 6
The independent components of compound (VI) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 7
The independent components of compound (VII) showing the atomlabelling scheme and the disorder in the carboxylate group; the major disorder component is drawn using full lines and the minor disorder component is drawn using broken lines. Displacement ellipsoids are drawn at the 30% probability level.

Figure 8
The independent components of compound (VIII) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 9
The independent components of compound (IX) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 10
The independent components of compound (X) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 11
The independent components of compound (XI) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 12
The independent components of compound (XII) showing the atomlabelling scheme and the disorder in one of the nitro groups, where the dominant disorder component is drawn using full lines, and the two minor disorder components are drawn using broken lines. Displacement ellipsoids are drawn at the 30% probability level.

Figure 13
The independent components of compound (XIII) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 14
The independent components of compound (XIV) showing the atomlabelling scheme and the disorder in one of the anions. The major disorder component is drawn using full lines and the minor disorder component is drawn using broken lines. Displacement ellipsoids are drawn at the 30% probability level. The atoms marked 'a' or 'b' are at the symmetry positions (2 À x, 1 À y, 2 À z) and (Àx, Ày, 2 À z), respectively. The H atoms bonded to atoms O32, O34 and O42 have occupancies 0.286 (9), 0.214 (9) and 0.5, respectively, as do their inversion-related equivalents.

Figure 15
The independent components of compound (XV) showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 30% probability level. the 1:1 salt (XIV) derived from fumaric acid, which is isomeric with maleic acid, crystallizes with two independent hydrogen fumarate anions, each lying across a centre of inversion: one of the anions is fully ordered but the other is disordered over two sets of atomic sites having occupancies 0.572 (9) and 0.428 (9) (Fig. 14). The 1:1 acid salt (XV) derived from (2R,3R)-tartaric acid crystallizes as a dihydrate (Fig. 15).
In none of the salts reported does the cation exhibit any internal symmetry: hence all are conformationally chiral but, with the exception of compounds (VI) and (VII), the space groups indicate that equal numbers of both conformational enantiomers are present. For all compounds except (VII), the reference cation was selected to be one for which the ringpuckering angles (Cremer & Pople, 1975) is close to zero, as calculated for the atom sequence (N1,C2,C3,N4,C5,C6). For the crystal of (VII) chosen for data collection, the value of this angle is 177.2 (5) , confirming that this salt and (VI) have opposite absolute structures. In all of the cations, the piperazine ring adopts a chair conformation with the N-aryl substituent in an equatorial site. In the 2-methoxyphenyl units, the methoxy C atom is always close to coplanar with the adjacent aryl ring: the displacement of this atom from the plane of the ring ranges from 0.038 (5) Å in compound (I) to 0.288 (5) Å in compound (VII). Associated with this near planarity, the two exocyclic C-C-O angles differ in each compound by ca 10 , as is usually observed in planar or nearplanar alkoxyarenes (Seip & Seip, 1973;Ferguson et al., 1996).
The two independent ions in compound (XIII) both contain a very short O-HÁ Á ÁO hydrogen bond (Table 1): while these are both nearly linear, the two O-H distances in each are significantly different, as established both by refinement of the atomic coordinates for the H atom, and from the final difference maps.

Supramolecular features
The supramolecular assembly in the salts (I)-(XV) is based on N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds augmented in a number of cases by C-HÁ Á ÁO and C-HÁ Á Á(arene) hydrogen bonds. In general, we have discounted hydrogen bonds having D-HÁ Á ÁA angles that are significantly less than 140 , as the interaction energies associated with such contacts are likely to be very low, so that these cannot be regarded as structurally significant (Wood et al., 2009). We have also discounted short contacts involving the H atoms of the methyl groups, as such groups are likely to be undergoing very rapid rotation about the adjacent C-O bonds (Riddell & Rogerson, 1996. Most of the C-HÁ Á Á(arene) contacts have HÁ Á ÁCg distances in excess of 2.85 Å , and we have therefore only considered the effects of such contacts in the assembly of compounds (III) and (IV), where these distances are below 2.80 Å . It should perhaps be conceded here that these are somewhat arbitrary judgments, made with the primary aim of avoiding over-interpretation of the longer contacts and overcomplication of the crystal structure descriptions.
In each of the isostructural pair of compounds (I) and (II), two N-HÁ Á ÁO hydrogen bonds (Table 1) link the ionic components into a centrosymmetric four-ion aggregate, char-

Figure 16
Part of the crystal structure of compound (I) showing the formation of a centrosymmetric four-ion aggregate. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms bonded to C atoms have been omitted. The atoms marked with an asterisk (*) are at the symmetry position (1 À x, 1 À y, 1 À z).

Figure 17
Part of the crystal structure of compound (III) showing the formation of a centrosymmetric four-ion aggregate. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms bonded to C atoms have been omitted. The atoms marked with an asterisk (*) are at the symmetry position (1 À x, 1 À y, 1 À z). research communications Table 1 Hydrogen bonds and short inter-ion contacts (Å , ).
Cg1, Cg2 and Cg3 represent the centroids of the rings (C31-C36), (C21-C26) and (C41-C46), respectively. acterized by an R 4 4 (12) (Etter, 1990;Etter et al., 1990;Bernstein et al., 1995) motif (Fig. 16). A similar motif occurs in the structure of compound (III) (Fig. 17), but the different orientations of the unit-cell outline in Figs. 16 and 17, illustrate the different arrangements of the components in compounds (I) and (II) on the one hand and compound (III) on the other. In (III), the four-ion aggregates are linked into chains by a C-HÁ Á Á(arene) interaction, but the C-HÁ Á ÁO contact in (III) has a very small D-HÁ Á ÁA angle and is thus not structurally significant (Wood et al., 2009).

Figure 18
Part of the crystal structure of compound (IV) showing the linking of the ion pairs by a further N-HÁ Á ÁO hydrogen bond to form a C 2 2 (6) chain running parallel to [001]. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the minor disorder component and the H atoms bonded to C atoms have been omitted.

Figure 19
Part of the crystal structure of compound (IV) showing the linking of the ions pairs by a C-HÁ Á Á(arene) hydrogen bond to form a chain parallel to [101]. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the minor disorder component and the H atoms not involved in the motif shown have been omitted.
combination. The ion pairs are linked by a second N-HÁ Á ÁO hydrogen bond to form a C 2 2 (6) chain running parallel to the [001] direction (Fig. 18), and they are linked by the C-HÁ Á Á(arene) hydrogen bond to form a chain running parallel to [101] (Fig. 19). The N-HÁ Á ÁO and C-HÁ Á Á hydrogen bonds, acting alternately, generate a chain running parallel to the [112] direction (Fig. 20), and the combination of chains running parallel to [001], [101] and [112] suffices to generate a three-dimensional structure. In the 2-chlorobenzoate analogue, compound (V), two independent N-HÁ Á ÁO hydrogen bonds again link the ions into a centrosymmetric R 4 4 (12) motif, of the type observed in compounds (I)-(III). There are two C-HÁ Á Á(arene) contacts in (V), but these are both long, and probably not structurally significant.
The ion pairs in compounds (VI) and (VII) are again linked into three-dimensional arrays, by a combination of N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, as opposed to the N-HÁ Á ÁO and C-HÁ Á Á(arene) interactions in the structure of (IV). An N-HÁ Á ÁO hydrogen bond links ion pairs which are related by the 2 1 screw axis along (x, 1/4, 1/2) to form a C 1 2 (4) chain along [100] (Fig. 21). In addition, the ion pairs which are related by the 2 1 screw axis along (1/4, 1/2, z) are linked by a C-HÁ Á ÁO hydrogen bond to form a C 2 2 (12) chain along [001] ( Part of the crystal structure of compound (IV) showing the alternating action of N-HÁ Á ÁO and C-HÁ Á Á(arene) hydrogen bonds in linking the ion pairs into a chain parallel to [112]. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the minor disorder component and the H atoms not involved in the motif shown have been omitted.

Figure 21
Part of the crystal structure of compound (VI) showing the formation of a C 1 2 (4) chain running parallel to [100], in which ion pairs are linked by a further N-HÁ Á ÁO hydrogen bond. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms bonded to C atoms have been omitted.

Figure 22
Part of the crystal structure of compound (VI) showing the formation of a C 2 2 (12) chain running parallel to [001], in which ion pairs are linked by a C-HÁ Á ÁO hydrogen bond. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms not involved in the motif shown have been omitted.

Figure 23
Part of the crystal structure of compound (VI) showing the formation of a chain running parallel to [010], in which ion pairs are linked by alternating N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms not involved in the motif shown have been omitted.

Figure 24
Part of the crystal structure of compound (IX) showing the formation of a hydrogen-bonded sheet lying parallel to (100). Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms bonded to C atoms have been omitted.

Figure 25
Part of the crystal structure of compound (XI) showing the formation of a hydrogen-bonded ribbon running parallel to [100]. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms bonded to C atoms have been omitted.

Figure 26
Part of the crystal structure of compound (XII) showing the formation of a centrosymmetric four-ion aggregate. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms bonded to C atoms have been omitted and only the major disorder component is shown. The atoms marked with an asterisk (*) are at the symmetry position (1 À x, 1 À y, 1 À z). parallel to the [100] direction (Fig. 25). In the picrate salt (XII), a combination of two independent N-HÁ Á ÁO hydrogen bonds links the components into a centrosymmetric four-ion aggregate of R 4 4 (16) type, where the two acceptor are the phenolic atom O31 and one of the nitro O atoms (Fig. 26). Aggregates of this type are weakly linked into a chain of rings by a C-HÁ Á ÁO hydrogen bond.
In compound (XIII), where Z 0 = 2, each of the anions contains a very short O-HÁ Á ÁO hydrogen bond, although in each of these interactions the two O-H distances are significantly different (Table 1). The supramolecular assembly depends upon three independent two-centre N-HÁ Á ÁO hydrogen bonds and one three-centre N-HÁ Á Á(O) 2 hydrogen bond. These link the ions into a ribbon, or molecular ladder, running parallel to the [010] direction and in which R 4 2 (14) rings centred at (0, n + 1/2, 1/2) alternate with R 8 8 (30) rings centred at (0, n, 1/2), where n represents an integer in each case (Fig. 27). Analysis of the supramolecular assembly in compound (XIV) is complicated by the combination of centrosymmetric anions and the disorder exhibited by one of them. However, since the hydrogen bonds involving the two disorder components are very similar, only the major disorder components need to be considered here. The ordered anions are linked by O-HÁ Á ÁO hydrogen bonds into a chain along (x, 0, 1) and the disordered anions are similarly linked into a chain along (x, 1/2, 1). The two types of chain, which alternate along the [010] direction, are linked by the cations to form a sheet of R 6 6 (26) rings lying parallel to (001) (Fig. 28). In the structure of compound (XV), the anions are linked by three independent O-HÁ Á ÁO hydrogen bonds, in which both of the hydroxyl groups as well as the carboxyl group act as donors, to form a sheet lying parallel to (001), in which both R 4 4 (18) and R 4 4 (20) rings can be identified (Fig. 29). The cations and the water molecules are tethered to this sheet, markedly increasing its complexity but without changing the dimensionality of the overall assembly. The result is a thick tripartite sheet, occupying the whole domain 0 < z < 1.0 and having a hydrogen-bonded layer in the centre with the aryl groups on the outside surfaces: there are no direction-specific interactions between adjacent sheets. Part of the crystal structure of compound (XIII) showing the formation of a hydrogen-bonded ribbon of R 4 2 (14) and R 8 8 (30) rings running parallel to [010]. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms bonded to C atoms have been omitted.

Figure 28
Part of the crystal structure of compound (XIV) showing the formation of a hydrogen-bonded sheet of R 6 6 (26) rings lying parallel to [001]. Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms bonded to C atoms have been omitted.

Figure 29
Part of the crystal structure of compound (XV) showing the formation of a hydrogen-bonded sheet of anions lying parallel to (001). Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the H atoms bonded to C atoms have been omitted.

Database survey
It is of interest briefly to compare the structures of the compounds reported here with those of some closely related examples, in particular the salts formed by the isomeric N-(4methoxyphenyl)piperazine (4-MeOPP) and the analogous N-(4-fluorophenyl)piperazine (4-FPP). The salts formed between 4-MeOPP and the benzoic acids 4-XC 6 H 4 COOH, where X = H, F, Cl, and Br, all crystallize as stoichiometric monohydrates and they are all isomorphous in space group P1 (Kiran , a combination of N-HÁ Á ÁO, O-HÁ Á ÁO, C-HÁ Á ÁO and C-HÁ Á Á(arene) hydrogen bonds links the components into complex sheets. By contrast, compounds (I)-(III) reported here all crystallize in solvent-free form and all form finite centrosymmetric four-ion aggregates (Figs. 16 and 17). The salt formed between 4-MeOPP and 4-aminobenzoate crystallizes as a monohydrate (Kiran Kumar et al., 2020), as compared with the solvent free analogues (IX) reported here, and the components are linked by a combination of N-HÁ Á ÁO, O-HÁ Á ÁO and C-HÁ Á Á(arene) hydrogen bonds to form a three-dimensional assembly, as compared with the two-dimensional assembly in (IX). The 3,5-dinitrobenzoate salt with 4-MeOPP crystallizes in solvent-free form (Kiran Kumar et al., 2020), as opposed to the dihydrate (XI) reported here, and the component ions are linked into the simple R 4 4 (12) motif found here for compounds (I)-(III), (VIII) and (X). The picrate salt of 4-MeOPP exhibits orientational disorder in one of the nitro groups (Kiran Kumar et al., 2020), as observed in compound (XII) here, but the supramolecular aggregation is more complex than the simple aggregate found for (XII), in that a combination of N-HÁ Á ÁO and C-HÁ Á Á(arene) hydrogen bonds generates a sheet structure. The anion in the hydrogen maleate salt of 4-MeOPP, which crystallizes with Z 0 = 1 (Kiran  unlike the Z 0 = 2 for compound (XIII), contains a very short, but unsymmetrical O-HÁ Á ÁO hydrogen bond, and the ions are linked into a chain of rings by a combination of two-centre N-HÁ Á ÁO and three-centre N-HÁ Á Á(O,O) hydrogen bonds. By contrast with compound (XIV) reported here where there are two independent hydrogen fumarate anions each lying across a centre of inversion, in the hydrogen fumarate salt of 4-MeOPP, there is only one type of anion, although this exhibits some orientational disorder and Z 0 = 1: a combination of N-HÁ Á ÁO and O-HÁ Á ÁO and C-HÁ Á Á(arene) hydrogen bonds links the ions into a threedimensional structure, as opposed to the two-dimensional structure of (XIV). Finally, we note some salts formed by 4-FPP with organic acids (Harish Chinthal, Yathirajan, Archana et al., 2020; Harish Chinthal, Yathirajan, Kavitha et al., 2020). The 2-fluorobenzoate crystallizes as a stoichiometric monohydrate, and the 2-bromobenzoate as a partial hydrate, while the 2-iodobenzoate crystallizes in solvent-free form (Harish Chinthal, Yathirajan, Kavitha et al., 2020), in contrast to compounds (IV)-(VII), which are all solvent-free, and the 3,5-dinitrobenzoate salt of 4-FPP is also solvent-free, as opposed to the dihydrate (XI). The 1:1 acid salt formed between (2R,3R)-tartaric acid and 4-FPP crystallizes as a monohydrate (Harish Chinthal, Yathirajan, Archana et al., 2020), whereas the analogous compound (XV) crystallizes as a 1.70 (hydrate).

Refinement
Crystal data, data collection and refinement details are summarized in Table 2. Two bad outlier reflections [(1,4,0) and (1,2,2)] were removed from the dataset for compound (V), and one bad outlier reflection (0,7,13) was removed from the dataset for compound (XV) before the final refinements. For compound (IV), calculation of the Flack x parameter (Flack, 1983)    , the bonded distances and the 1,3-non-bonded distances were restrained to be the same as the corresponding distances in the major disorder components, subject to s.u. values of 0.01 and 0.02 Å , respectively, and the anisotropic displacement parameters for corresponding pairs of atoms in the two disorder components were constrained to be the same, giving occupancies of 0.907 (8) and 0.093 (8). Similar distance restraints were applied to the disordered carboxylate group in compound (VII), where the displacement parameters for the disordered O atoms were subjected to similarity restraints, giving occupancies of 0.53 (9) and 0.47 (9). The disordered nitro group in compound (XII) was modelled over three sets of atomic sites, with similar restraints to those imposed in (VII) giving occupancies of 0.860 (5), 0.080 (4) and 0.069 (4). All H atoms, apart from those in the minor disorder component of compound (IV) and in the partial-occupancy water molecule in compound (V), were located in difference maps. The H atoms bonded to C atoms, apart from those in the disordered anion of compound (XIV) which were permitted to ride at the locations found in difference maps, were then treated as riding atoms in geometrically idealized positions with C-H distances of 0.93 Å (alkenyl and aromatic), 0.96 Å (CH 3 ), 0.97 Å (CH 2 ) or 0.98 Å (aliphatic C-H), and with U iso (H) = kU eq (C), where k = 1.5 for the methyl groups, which were permitted to rotate but not to tilt, and   SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: PLATON (Spek, 2020); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015b) and PLATON (Spek, 2020).

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.15 e Å −3 Δρ min = −0.24 e Å −3 Extinction correction: SHELXL, Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.019 (2) Special details Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.