Crystal structure of a compact three-dimensional metal–organic framework based on Cs+ and (4,5-di­cyano-1,2-phenyl­ene)bis­(phospho­nic acid)

Mendes, R.F.; Venkatramaiah, N.; Tomé, J. P.C.; Almeida Paz, F.A.

doi:10.1107/S2056989016016765

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ISSN: 2056-9890

Volume 72| Part 12| December 2016| Pages 1794-1798

https://doi.org/10.1107/S2056989016016765

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Crystal structure of a compact three-dimensional metal–organic framework based on Cs⁺ and (4,5-dicyano-1,2-phenylene)bis(phosphonic acid)

Ricardo F. Mendes,^a Nutalapati Venkatramaiah,^b João P. C. Tomé ^c,^b and Filipe A. Almeida Paz ^a ^*

^aDepartment of Chemistry, CICECO - Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal, ^bDepartment of Chemistry, QOPNA, University of Aveiro, 3810-193 Aveiro, Portugal, and ^cCentro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
^*Correspondence e-mail: filipe.paz@ua.pt

Edited by G. Smith, Queensland University of Technology, Australia (Received 3 August 2016; accepted 19 October 2016; online 15 November 2016)

A new metal–organic framework compound, poly[[μ₇-dihydrogen (4,5-dicyano-1,2-phenylene)diphosphonato](oxonium)caesium], [Cs(C₈H₄N₂O₆P₂)(H₃O)]_n (I), based on Cs⁺ and the organic linker 4,5-dicyano-1,2-phenylene)bis(phosphonic acid, (H₄cpp), containing two distinct coordinating functional groups, has been prepared by a simple diffusion method and its crystal structure is reported. The coordination polymeric structure is based on a CsO₈N₂ complex unit comprising a monodentate hydronium cation, seven O-atom donors from two phosphonium groups of the (H₂cpp)²⁻ ligand, and two N-atom donors from bridging cyano groups. The high level of connectivity from both the metal cation and the organic linker allow the formation of a compact and dense three-dimensional network without any crystallization solvent. Topologically (I) is a seven-connected uninodal network with an overall Schäfli symbol of {4¹⁷.6⁴}. Metal cations form an undulating inorganic layer, which is linked by strong and highly directional O—H⋯O hydrogen-bonding interactions. These metallic layers are, in turn, connected by the organic ligands along the [010] direction to form the overall three-dimensional framework structure.

Keywords: crystal structure; caesium; metal–organic framework; phosphonic acid ligand.

CCDC reference: 1510674

1. Chemical context

The area of metal–organic frameworks (MOFs) and coordination polymers (CPs) has proven to be of great importance, not only in academic research but also for industrial applications (Silva et al., 2015 ). The simple and easy preparation of these materials, allied with the enormous variety of building blocks (either metal atoms or organic linkers) make these materials ideal to be employed in different applications: gas sorption/separation (Sumida et al., 2012 ), as heterogeneous catalysts (Mendes et al., 2015 ), luminescence (Heine & Müller-Buschbaum, 2013 ), batteries and as corrosion inhibitors (Morozan & Jaouen, 2012 ), among many others. Most of these compounds are obtained by mixing transition metal cations with carboxylic acids. The use of other oxygen-based donor groups such as phosphonic acids has seen a great resurgence in recent years. The use of mixed oxygen–nitrogen donor organic linkers is relatively less common, as confirmed by a search of the Cambridge Structural Database (CSD) (Groom et al., 2016 ).

Although alkali-metal cations are of great interest due to their abundance in biological systems, there is a surprisingly small number of MOFs/CPs based on these elements. Cs⁺-based materials are not as common as other alkali metals, especially when coordinated by either phosphonic or sulfonic acid residues. Reports on these structures are directed to solely structural descriptions rather than to applications. Nevertheless, these compounds can be used as functional materials in batteries, either as proton conductors (Bazaga-Garcia et al., 2015 ) or as insulators (Tominaka et al., 2013 ).

Following our interest in this field of research, we report the preparation of a new compact and dense MOF network, [Cs(H₂cpp)(H₃O)]_n, prepared by the self-assembly of Cs⁺ and the organic linker (4,5-dicyano-1,2-phenylene)bis(phosphonic acid), (H₄cpp), previously reported by our group (Venkatramaiah et al., 2015 ). The title compound, [Cs(H₂cpp)(H₃O)]_n (I), was assembled under atmospheric conditions and represents, to the best of our knowledge, the first reported MOF or CP based on an amino/cyano phosphonate with caesium as the metal cation, and the crystal structure is reported herein.

2. Structural commentary

The asymmetric unit of (I) comprises one Cs⁺ atom coordinated by a dianionic H₂cpp²⁻ ligand, together with a monodentate hydronium cation (Fig. 1). The irregular CsO₈N₂ coordination polyhedron is defined by the O atom of one monodentate hydronium molecule, six hydrogen phosphonate O-atom donors and two cyano N-atom donors. The Cs—O bond-length range is 3.159 (4)–3.410 (3) Å and for Cs—N, 3.234 (7) and 3.334 (6) Å (Table 1). These values are in good agreement with those reported for other phosphonate-based materials as found in a search in the Cambridge Structural Database (CSD; Groom et al., 2016): mean value of 3.24 Å for the Cs—O bond (CSD range, 3.01–3.41 Å), and 3.28 Å for the Cs—N bond (CSD range, 2.35–3.79 Å).

Table 1
Selected bond lengths (Å)

Cs1—O1	3.400 (3)	Cs1—O6^v	3.259 (4)
Cs1—O1W	3.388 (4)	Cs1—O5^vi	3.159 (4)
Cs1—O4	3.269 (4)	P1—O1	1.499 (4)
Cs1—N1ⁱ	3.234 (7)	P1—O2	1.509 (4)
Cs1—N2ⁱⁱ	3.334 (6)	P1—O3	1.558 (4)
Cs1—O1ⁱⁱⁱ	3.229 (3)	P2—O4	1.497 (4)
Cs1—O3^iv	3.356 (4)	P2—O5	1.572 (4)
Cs1—O4^v	3.410 (3)	P2—O6	1.495 (3)
Symmetry codes: (i) $[-x+1, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (ii) $[-x+2, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iii) -x+1, -y+1, -z+1; (iv) -x+1, -y+1, -z+2; (v) -x+2, -y+1, -z+1; (vi) -x+2, -y+1, -z+2.

Figure 1
The asymmetric unit of [Cs(H₂cpp)(H₃O)]_n (I)

showing all non-hydrogen atoms represented as displacement ellipsoids drawn at the 50% probability level and hydrogen atoms as small spheres with arbitrary radius. The coordination sphere of Cs⁺ is completed by generating (through symmetry) the remaining oxygen and nitrogen atoms. For symmetry codes, see Table 1

The crystallographic independent H₂cpp²⁻ residue in (I) acts as a linker connecting seven symmetry-related Cs⁺ metal atoms. The coordination modes between cyano and phosphonate groups are, as expected, different. While the cyano groups connect to two different metal atoms, each in a simple κ¹ coordination mode, the two phosphonate groups coordinate to the remaining metals by κ¹-O, κ²-O and μ₂-O,O coordination modes. This high coordination of the phosphonate groups is responsible for the formation of a metallic undulating inorganic layer lying in the ac plane of the unit cell. Within this layer, the intermetallic Cs⋯Cs distances range from 5.7792 (4) to 7.8819 (5) Å (Fig. 2). The cyano groups are, on the other hand, responsible for the inter-layer connections along the [010] direction. In this case, the intermetallic Cs⋯Cs distances between layers range from 9.7347 (6) to 9.9044 (6) Å. Although the organic linkers are stacked, the minimum inter-centroid distance of 4.6545 (3) Å (as calculated using PLATON: Spek, 2009 ) indicates the absence of any significant π–π stacking interactions.

Figure 2
Schematic representation of the connectivity of (a) the anionic H₂cpp²⁻ ligand; (b) the Cs⁺ cation and (c) the seven-connected [Cs(H₂cpp)(H₃O)] uninodal network with an overall Schäfli symbol of {4¹⁷.6⁴}.

The unusual presence of a coordinating H₃O⁺ ion in this Cs⁺ structure is confirmed by the location of the three hydrogen atoms associated with this cation, which were clearly visible from difference-Fourier maps and by the presence of the double charge with respect to the delocalized P1—O1, P1—O2 and P2—O4, P1—O6 bonds [1.499 (4), 1.509 (3) Å and 1.497 (4), 1.495 (3) Å, respectively]. The P1—O3 and P2—O5 bond lengths for the protonated groups are 1.558 (4) and 1.572 (4) Å, respectively. In addition, although the distance between O1W and O4 is very short, suggesting a possible O4—H⋯O1W interaction, a calculated site for such a hydrogen was found to be sterically impossible in the crowded environment about Cs. Not only that, but any attempts to refine this molecule as a coordination water molecule proved to be not as successful as the hydronium cation. When the proton is connected to the adjacent phosphonic residue, the bond is only possible by restraining the O—H distance between O4 and the proton. Also there was still a residual charge near O1W, which corroborated the initial refinement.

3. Topology

The various coordination modes of the ligand and the presence of a compact undulating inorganic layer formed by the metal atoms to form the MOF architecture can be better understood from a pure topological perspective. Based on the recommendations of Alexandrov et al. (2011 ), any moiety (ligand, atom or clusters of atoms) connecting more than two metallic centers (μ_n) should be considered as a network node. For (I), all crystallographically independent moieties comprising the asymmetric unit, both the Cs⁺ cation and the anionic H₂cpp²⁻ ligand, should therefore be considered as nodes. Using the software package TOPOS (Blatov & Shevchenko, 2006 ), (I) could be classified as a seven-connected uninodal network with an overall Schäfli symbol of {4¹⁷.6⁴}. Fig. 2 illustrates the breakdown of the network of (I) into nodes and connecting rods, with the individual connectivity of each node being superimposed into the crystal structure itself (Fig. 2a and 2b). The metal atom and the organic linker are connected to each other in every direction of the unit cell (Fig. 2c), forming a compact and robust three-dimensional network (Fig. 3). The absence of water molecules of crystallization leads to this very compact structure having no solvent-accessible pores: only 0.2% of the unit cell volume [calculated using Mercury (Macrae et al., 2006 )] corresponds to voids.

Figure 3
Schematic representation of the crystal packing of [Cs(H₂cpp) (H₃O)]_n viewed in perspective (a) along [001] and (b) along [100]. The representations emphasize the connection of the undulating inorganic layers located in the ac plane of the unit cell (and formed by the metal cations) through the organic ligand. The bottom representation further emphasizes the stacking of the organic linkers with inter-centroid ring distances of 4.6545 (3) Å.

4. Supramolecular features

The lack of crystallization solvent molecules in (I) results in a rather small number of crystallographically different hydrogen-bonding supramolecular interactions (Table 2). Indeed, although the structure is rich in hydrogen-bonding acceptors, only the POH and the H₃O⁺ moieties can establish strong interactions. A total of five distinct hydrogen bonds are present, two of these involving the phosphonic acid donor groups [O3—H3⋯O6^vii and O5—H5⋯O2) and three involving the H₃O⁺ moiety (O1W—H1X⋯O2^iv, O1W—H1Y⋯O1 and O1W—H1Z⋯O4ⁱⁱⁱ (for symmetry codes, see Tables 1 and 2)]. An overall three-dimensional network structure is generated in which there are 62 Å³ voids (though not solvent-accessible ones). No π–π ring interactions are present (minimum ring-centroid separation = 4.655 Å). These hydrogen bonds are confined within the inorganic undulating layer (Fig. 4).

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O6^vii	0.95 (1)	1.59 (12)	2.528 (5)	172 (5)
O5—H5⋯O2	0.94 (1)	1.60 (12)	2.545 (5)	175 (5)
O1W—H1X⋯O2^iv	0.95 (1)	1.64 (16)	2.553 (5)	160 (4)
O1W—H1Y⋯O1	0.96 (1)	1.66 (11)	2.526 (5)	149 (4)
O1W—H1Z⋯O4ⁱⁱⁱ	0.95 (1)	1.56 (15)	2.485 (5)	162 (4)
Symmetry codes: (iii) -x+1, -y+1, -z+1; (iv) -x+1, -y+1, -z+2; (vii) x-1, y, z.

Figure 4
Schematic representation of a portion of the undulating inorganic layer comprising the crystal structure of (I)

, emphasizing the various strong and directional supramolecular O—H⋯O hydrogen-bonding interactions (orange dashed lines) present within this layer. For geometrical details and symmetry codes, see Table 2

5. Database survey

Although unusual in the case of Cs, in the Cambridge Structural Database (CSD) a total of 45 structures in which coordination between the metal cation and the hydronium cation is present, e.g. among the metal complexes (Reyes-Martínez et al., 2009 ; Jennifer et al., 2014 ; Teng et al., 2016 ; Hu & Mak, 2013 ) and coordination polymer/metal–organic frameworks (Yotnoi et al., 2015 ; Wang et al., 2013 ; Humphrey et al., 2005 ). Wang et al. (2013) in fact reported the structures of an isotypic series of crystal materials involving lanthanides (Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Y), in which the presence of the coordinating hydronium cation was confirmed.

6. Synthesis and crystallization

Chemicals were purchased from commercial sources and used without any further purification steps. (4,5-Dicyano-1,2-phenylene)bis(phosphonic acid) (H₄cpp) was prepared according to published procedures (Venkatramaiah et al., 2015).

Synthesis of [Cs(H₂cpp)(H₃O)]_n, (I): H₄cpp (29 mg, 0.1 mM) was dissolved in 4 ml of methanol. A 1 ml aliquot of a methanolic caesium hydroxide solution (45 mg, 0.3 mM; Sigma Aldrich, puriss p.a. ≥ 96%) was added slowly. The resulting mixture was stirred at ambient temperature for 10 min for uniform mixing. The final solution was allowed to slowly evaporate at ambient temperature. White transparent crystals of the title compound were obtained after one week. Crystals were filtered and dried under vacuum.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. Hydrogen atoms bound to carbon were placed at idealized positions with C—H = 0.95 Å and included in the final structural model in a riding-motion approximation with the isotropic displacement parameters fixed at 1.2U_eq(C). Hydrogen atoms associated with the H₃O⁺ moiety and the phosphonate groups were clearly located from difference-Fourier maps and were included in the refinement with the O—H and H⋯H (only for the cation) distances restrained to 0.95 (1) and 1.55 (1) Å, respectively, in order to ensure a chemically reasonable environment for these moieties. These hydrogen atoms were modelled with the isotropic displacement parameters fixed at 1.5U_eq(O). In order to avoid a close proximity between the H atoms associated with the POH group and the H₃O⁺ cation and the central Cs⁺ ion in the crystal structure, an antibump restraint [3.5 (1) Å)] was included in the overall refinement.

Table 3
Experimental details

Crystal data
Chemical formula	[Cs(C₈H₄N₂O₆P₂)(H₃O)]
M_r	438.01
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	180
a, b, c (Å)	7.8819 (5), 24.5497 (14), 7.3137 (4)
β (°)	98.739 (2)
V (Å³)	1398.76 (14)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	2.91
Crystal size (mm)	0.15 × 0.06 × 0.02

Data collection
Diffractometer	Bruker D8 QUEST
Absorption correction	Multi-scan (SADABS; Bruker 2012 )
T_min, T_max	0.647, 0.747
No. of measured, independent and observed [I > 2σ(I)] reflections	27787, 2550, 2499
R_int	0.021
(sin θ/λ)_max (Å⁻¹)	0.602

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.031, 0.080, 1.50
No. of reflections	2550
No. of parameters	196
No. of restraints	10
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.70, −0.60
Computer programs: APEX2 and SAINT (Bruker, 2012), SHELXS (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ) and DIAMOND (Brandenburg, 1999 ).

Supporting information

CCDC reference: 1510674

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: https://doi.org/10.1107/S2056989016016765/zs2366sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989016016765/zs2366Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2012); cell refinement: SAINT (Bruker, 2012); data reduction: SAINT (Bruker, 2012); program(s) used to solve structure: SHELXS (Sheldrick, 2015); program(s) used to refine structure: SHELXL2014/6 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL2014/6 (Sheldrick, 2015).

Poly[[µ₇-dihydrogen (4,5-dicyano-1,2-phenylene)diphosphonato](oxonium)caesium] top

Crystal data top

[Cs(C₈H₄N₂O₆P₂)(H₃O)]	F(000) = 840
M_r = 438.01	D_x = 2.080 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.8819 (5) Å	Cell parameters from 9290 reflections
b = 24.5497 (14) Å	θ = 2.7–36.7°
c = 7.3137 (4) Å	µ = 2.91 mm⁻¹
β = 98.739 (2)°	T = 180 K
V = 1398.76 (14) Å³	Plate, colourless
Z = 4	0.15 × 0.06 × 0.02 mm

Data collection top

Bruker D8 QUEST diffractometer	2550 independent reflections
Radiation source: Sealed tube	2499 reflections with I > 2σ(I)
Multi-layer X-ray mirror monochromator	R_int = 0.021
Detector resolution: 10.4167 pixels mm^-1	θ_max = 25.4°, θ_min = 3.6°
ω/φ scans	h = −9→9
Absorption correction: multi-scan (SADABS; Bruker 2012)	k = −29→29
T_min = 0.647, T_max = 0.747	l = −8→8
27787 measured reflections

Refinement top

Refinement on F²	10 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.031	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.080	w = 1/[σ²(F_o²) + (0.0134P)² + 6.7796P] where P = (F_o² + 2F_c²)/3
S = 1.50	(Δ/σ)_max = 0.002
2550 reflections	Δρ_max = 0.70 e Å⁻³
196 parameters	Δρ_min = −0.60 e Å⁻³

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cs1	0.78119 (4)	0.56625 (2)	0.69290 (4)	0.02080 (11)
O1W	0.3543 (5)	0.54753 (15)	0.6850 (5)	0.0224 (8)
H1X	0.330 (6)	0.5549 (18)	0.806 (3)	0.034*
H1Y	0.3732 (16)	0.5092 (4)	0.675 (6)	0.034*
H1Z	0.258 (4)	0.5572 (15)	0.597 (5)	0.034*
P1	0.56069 (15)	0.42656 (5)	0.83441 (16)	0.0139 (2)
P2	0.97399 (15)	0.40970 (5)	0.72111 (17)	0.0147 (3)
O1	0.5083 (4)	0.45821 (14)	0.6597 (5)	0.0197 (7)
O2	0.6914 (4)	0.45406 (14)	0.9768 (5)	0.0186 (7)
O3	0.4048 (4)	0.41059 (15)	0.9310 (5)	0.0185 (7)
H3	0.311 (5)	0.403 (2)	0.837 (6)	0.028*
O4	0.8955 (4)	0.44573 (15)	0.5659 (5)	0.0237 (8)
O5	0.9966 (4)	0.44125 (15)	0.9103 (5)	0.0217 (8)
H5	0.886 (3)	0.4463 (14)	0.943 (7)	0.033*
O6	1.1438 (4)	0.38507 (14)	0.7016 (5)	0.0203 (7)
N1	0.4101 (9)	0.1823 (3)	0.7906 (11)	0.0603 (19)
N2	0.9099 (8)	0.1597 (2)	0.7224 (8)	0.0435 (14)
C1	0.6536 (6)	0.36144 (19)	0.7793 (6)	0.0143 (9)
C2	0.8230 (6)	0.3543 (2)	0.7429 (6)	0.0160 (10)
C3	0.8843 (6)	0.3016 (2)	0.7237 (7)	0.0189 (10)
H3A	0.9990	0.2968	0.7014	0.023*
C4	0.7834 (7)	0.2561 (2)	0.7360 (6)	0.0201 (10)
C5	0.6129 (7)	0.2632 (2)	0.7663 (7)	0.0222 (11)
C6	0.5506 (6)	0.3153 (2)	0.7867 (7)	0.0194 (10)
H6A	0.4350	0.3198	0.8061	0.023*
C7	0.5014 (8)	0.2170 (2)	0.7777 (9)	0.0333 (14)
C8	0.8522 (8)	0.2021 (2)	0.7244 (8)	0.0294 (12)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cs1	0.02062 (17)	0.02091 (18)	0.02049 (17)	−0.00137 (12)	0.00196 (12)	−0.00099 (12)
O1W	0.0225 (18)	0.0260 (19)	0.0182 (18)	0.0044 (15)	0.0015 (15)	−0.0030 (15)
P1	0.0117 (6)	0.0164 (6)	0.0135 (6)	0.0012 (5)	0.0021 (4)	−0.0005 (5)
P2	0.0109 (6)	0.0189 (6)	0.0142 (6)	−0.0009 (5)	0.0014 (5)	−0.0007 (5)
O1	0.0225 (18)	0.0222 (18)	0.0151 (17)	0.0047 (14)	0.0051 (14)	0.0011 (14)
O2	0.0139 (16)	0.0240 (18)	0.0177 (17)	0.0003 (14)	0.0020 (13)	−0.0046 (14)
O3	0.0126 (16)	0.0276 (19)	0.0156 (17)	0.0001 (14)	0.0034 (13)	−0.0003 (14)
O4	0.0198 (18)	0.0239 (19)	0.0257 (19)	−0.0040 (15)	−0.0019 (15)	0.0079 (16)
O5	0.0160 (17)	0.028 (2)	0.0216 (18)	−0.0040 (14)	0.0041 (14)	−0.0063 (15)
O6	0.0136 (17)	0.0279 (19)	0.0187 (18)	0.0005 (14)	0.0003 (14)	−0.0020 (15)
N1	0.067 (4)	0.037 (3)	0.082 (5)	−0.024 (3)	0.029 (4)	−0.006 (3)
N2	0.054 (3)	0.029 (3)	0.045 (3)	0.012 (3)	0.000 (3)	−0.003 (2)
C1	0.018 (2)	0.014 (2)	0.010 (2)	0.0009 (18)	−0.0006 (18)	0.0020 (18)
C2	0.013 (2)	0.018 (2)	0.015 (2)	−0.0004 (19)	−0.0017 (18)	−0.0024 (19)
C3	0.017 (2)	0.023 (3)	0.015 (2)	0.005 (2)	−0.0022 (19)	0.000 (2)
C4	0.029 (3)	0.021 (3)	0.008 (2)	0.004 (2)	−0.002 (2)	−0.0014 (19)
C5	0.026 (3)	0.020 (3)	0.020 (3)	−0.006 (2)	0.003 (2)	−0.002 (2)
C6	0.017 (2)	0.022 (3)	0.019 (3)	−0.002 (2)	0.0028 (19)	−0.001 (2)
C7	0.040 (3)	0.023 (3)	0.039 (4)	−0.006 (3)	0.015 (3)	−0.004 (3)
C8	0.037 (3)	0.024 (3)	0.026 (3)	0.002 (2)	0.002 (2)	−0.004 (2)

Geometric parameters (Å, º) top

Cs1—O1	3.400 (3)	O1W—H1X	0.95 (3)
Cs1—O1W	3.388 (4)	O1W—H1Y	0.957 (11)
Cs1—O4	3.269 (4)	O1W—H1Z	0.95 (3)
Cs1—N1ⁱ	3.234 (7)	O3—H3	0.95 (4)
Cs1—N2ⁱⁱ	3.334 (6)	O5—H5	0.95 (3)
Cs1—O1ⁱⁱⁱ	3.229 (3)	N1—C7	1.128 (9)
Cs1—O3^iv	3.356 (4)	N2—C8	1.137 (7)
Cs1—O4^v	3.410 (3)	C1—C2	1.412 (7)
Cs1—O6^v	3.259 (4)	C1—C6	1.399 (7)
Cs1—O5^vi	3.159 (4)	C2—C3	1.396 (7)
P1—O1	1.499 (4)	C3—C4	1.382 (7)
P1—O2	1.509 (4)	C4—C8	1.440 (7)
P1—O3	1.558 (4)	C4—C5	1.406 (8)
P1—C1	1.829 (5)	C5—C7	1.445 (8)
P2—O4	1.497 (4)	C5—C6	1.386 (7)
P2—O5	1.572 (4)	C3—H3A	0.9500
P2—O6	1.495 (3)	C6—H6A	0.9500
P2—C2	1.830 (5)

O1—Cs1—O1W	43.71 (8)	O2—P1—C1	106.8 (2)
O1—Cs1—O4	58.15 (8)	O3—P1—C1	104.5 (2)
O1—Cs1—N1ⁱ	113.35 (14)	O4—P2—O5	110.8 (2)
O1—Cs1—N2ⁱⁱ	170.46 (11)	O4—P2—O6	116.1 (2)
O1—Cs1—O1ⁱⁱⁱ	55.63 (9)	O4—P2—C2	107.8 (2)
O1—Cs1—O3^iv	80.81 (9)	O5—P2—O6	107.5 (2)
O1—Cs1—O4^v	114.27 (8)	O5—P2—C2	106.1 (2)
O1—Cs1—O6^v	114.88 (9)	O6—P2—C2	108.1 (2)
O1—Cs1—O5^vi	106.05 (9)	Cs1—O1—P1	104.72 (16)
O1W—Cs1—O4	100.85 (9)	Cs1—O1—Cs1ⁱⁱⁱ	124.37 (11)
O1W—Cs1—N1ⁱ	69.68 (14)	Cs1ⁱⁱⁱ—O1—P1	130.85 (18)
O1W—Cs1—N2ⁱⁱ	142.36 (12)	Cs1^iv—O3—P1	143.32 (19)
O1ⁱⁱⁱ—Cs1—O1W	51.81 (9)	Cs1—O4—P2	114.80 (18)
O1W—Cs1—O3^iv	58.71 (8)	Cs1—O4—Cs1^v	119.82 (11)
O1W—Cs1—O4^v	143.40 (9)	Cs1^v—O4—P2	96.45 (15)
O1W—Cs1—O6^v	110.36 (8)	Cs1^vi—O5—P2	138.83 (19)
O1W—Cs1—O5^vi	114.73 (9)	Cs1^v—O6—P2	102.81 (17)
O4—Cs1—N1ⁱ	163.38 (15)	H1X—O1W—H1Z	109 (3)
O4—Cs1—N2ⁱⁱ	116.78 (11)	H1Y—O1W—H1Z	108 (3)
O1ⁱⁱⁱ—Cs1—O4	78.26 (9)	Cs1—O1W—H1Z	132 (2)
O3^iv—Cs1—O4	124.05 (9)	Cs1—O1W—H1X	107 (3)
O4—Cs1—O4^v	60.18 (9)	Cs1—O1W—H1Y	88.2 (9)
O4—Cs1—O6^v	89.17 (9)	H1X—O1W—H1Y	108 (4)
O4—Cs1—O5^vi	94.02 (9)	P1—O3—H3	108 (3)
N1ⁱ—Cs1—N2ⁱⁱ	73.64 (16)	Cs1^iv—O3—H3	104 (3)
O1ⁱⁱⁱ—Cs1—N1ⁱ	85.23 (15)	P2—O5—H5	108 (3)
O3^iv—Cs1—N1ⁱ	63.64 (15)	Cs1^vi—O5—H5	100 (3)
O4^v—Cs1—N1ⁱ	119.25 (15)	Cs1^vii—N1—C7	167.2 (6)
O6^v—Cs1—N1ⁱ	81.85 (15)	Cs1^viii—N2—C8	155.5 (5)
O5^vi—Cs1—N1ⁱ	102.33 (15)	P1—C1—C2	124.9 (4)
O1ⁱⁱⁱ—Cs1—N2ⁱⁱ	133.14 (12)	C2—C1—C6	118.5 (4)
O3^iv—Cs1—N2ⁱⁱ	97.40 (12)	P1—C1—C6	116.4 (4)
O4^v—Cs1—N2ⁱⁱ	64.93 (12)	P2—C2—C3	116.1 (4)
O6^v—Cs1—N2ⁱⁱ	71.74 (12)	P2—C2—C1	124.8 (4)
O5^vi—Cs1—N2ⁱⁱ	65.30 (12)	C1—C2—C3	119.1 (4)
O1ⁱⁱⁱ—Cs1—O3^iv	110.02 (8)	C2—C3—C4	122.1 (5)
O1ⁱⁱⁱ—Cs1—O4^v	92.16 (8)	C3—C4—C5	118.9 (5)
O1ⁱⁱⁱ—Cs1—O6^v	64.05 (8)	C5—C4—C8	120.1 (5)
O1ⁱⁱⁱ—Cs1—O5^vi	161.55 (9)	C3—C4—C8	121.0 (5)
O3^iv—Cs1—O4^v	157.79 (8)	C6—C5—C7	119.3 (5)
O3^iv—Cs1—O6^v	145.49 (9)	C4—C5—C7	121.1 (5)
O3^iv—Cs1—O5^vi	60.47 (8)	C4—C5—C6	119.6 (5)
O4^v—Cs1—O6^v	44.67 (8)	C1—C6—C5	121.7 (5)
O4^v—Cs1—O5^vi	98.52 (8)	N1—C7—C5	177.0 (7)
O5^vi—Cs1—O6^v	133.23 (8)	N2—C8—C4	177.2 (6)
O1—P1—O2	115.3 (2)	C2—C3—H3A	119.00
O1—P1—O3	112.52 (19)	C4—C3—H3A	119.00
O1—P1—C1	109.5 (2)	C1—C6—H6A	119.00
O2—P1—O3	107.6 (2)	C5—C6—H6A	119.00

O1W—Cs1—O1—P1	−114.0 (2)	O1—Cs1—O5^vi—P2^vi	−110.8 (3)
O1W—Cs1—O1—Cs1ⁱⁱⁱ	68.38 (14)	O1W—Cs1—O5^vi—P2^vi	−64.9 (3)
O4—Cs1—O1—P1	79.83 (17)	O4—Cs1—O5^vi—P2^vi	−168.8 (3)
O4—Cs1—O1—Cs1ⁱⁱⁱ	−97.75 (14)	O1—P1—C1—C2	79.5 (4)
N1ⁱ—Cs1—O1—P1	−116.3 (2)	O1—P1—C1—C6	−105.0 (4)
N1ⁱ—Cs1—O1—Cs1ⁱⁱⁱ	66.1 (2)	O2—P1—C1—C2	−46.0 (4)
O1ⁱⁱⁱ—Cs1—O1—P1	177.6 (2)	O2—P1—C1—C6	129.6 (4)
O1ⁱⁱⁱ—Cs1—O1—Cs1ⁱⁱⁱ	−0.02 (14)	O3—P1—C1—C2	−159.8 (4)
O3^iv—Cs1—O1—P1	−60.36 (16)	O3—P1—C1—C6	15.7 (4)
O3^iv—Cs1—O1—Cs1ⁱⁱⁱ	122.06 (13)	O3—P1—O1—Cs1	132.24 (17)
O4^v—Cs1—O1—P1	102.56 (17)	C1—P1—O1—Cs1	−112.09 (19)
O4^v—Cs1—O1—Cs1ⁱⁱⁱ	−75.03 (14)	O2—P1—O1—Cs1ⁱⁱⁱ	−174.33 (19)
O6^v—Cs1—O1—P1	151.95 (15)	O3—P1—O1—Cs1ⁱⁱⁱ	−50.4 (3)
O6^v—Cs1—O1—Cs1ⁱⁱⁱ	−25.63 (15)	C1—P1—O1—Cs1ⁱⁱⁱ	65.3 (3)
O5^vi—Cs1—O1—P1	−4.83 (18)	O1—P1—O3—Cs1^iv	−111.9 (3)
O5^vi—Cs1—O1—Cs1ⁱⁱⁱ	177.59 (11)	O2—P1—O1—Cs1	8.3 (2)
O1—Cs1—O4—P2	−89.90 (19)	C1—P1—O3—Cs1^iv	129.5 (3)
O1—Cs1—O4—Cs1^v	156.05 (16)	O2—P1—O3—Cs1^iv	16.2 (4)
O1W—Cs1—O4—P2	−99.61 (18)	O4—P2—C2—C3	121.5 (4)
O1W—Cs1—O4—Cs1^v	146.34 (11)	O5—P2—C2—C1	59.4 (4)
N2ⁱⁱ—Cs1—O4—P2	80.8 (2)	O6—P2—C2—C1	174.4 (4)
N2ⁱⁱ—Cs1—O4—Cs1^v	−33.23 (17)	O6—P2—C2—C3	−4.7 (4)
O1ⁱⁱⁱ—Cs1—O4—P2	−146.54 (19)	O5—P2—C2—C3	−119.8 (4)
O1ⁱⁱⁱ—Cs1—O4—Cs1^v	99.41 (12)	O4—P2—C2—C1	−59.4 (4)
O3^iv—Cs1—O4—P2	−40.2 (2)	O5—P2—O4—Cs1	−4.8 (2)
O3^iv—Cs1—O4—Cs1^v	−154.24 (10)	O6—P2—O4—Cs1	−127.67 (19)
O4^v—Cs1—O4—P2	114.1 (2)	C2—P2—O4—Cs1	110.9 (2)
O4^v—Cs1—O4—Cs1^v	−0.02 (9)	O5—P2—O4—Cs1^v	122.33 (16)
O6^v—Cs1—O4—P2	149.81 (18)	O6—P2—O4—Cs1^v	−0.5 (2)
O6^v—Cs1—O4—Cs1^v	35.76 (12)	C2—P2—O4—Cs1^v	−121.95 (17)
O5^vi—Cs1—O4—P2	16.53 (19)	O4—P2—O5—Cs1^vi	−158.3 (2)
O5^vi—Cs1—O4—Cs1^v	−97.52 (12)	O6—P2—O5—Cs1^vi	−30.5 (3)
O1W—Cs1—N2ⁱⁱ—C8ⁱⁱ	−38.5 (13)	C2—P2—O5—Cs1^vi	85.0 (3)
O4—Cs1—N2ⁱⁱ—C8ⁱⁱ	140.8 (11)	O4—P2—O6—Cs1^v	0.6 (2)
O1—Cs1—O1ⁱⁱⁱ—Cs1ⁱⁱⁱ	0.00 (10)	O5—P2—O6—Cs1^v	−124.03 (17)
O1—Cs1—O1ⁱⁱⁱ—P1ⁱⁱⁱ	176.9 (3)	C2—P2—O6—Cs1^v	121.81 (17)
O1W—Cs1—O1ⁱⁱⁱ—Cs1ⁱⁱⁱ	−54.81 (12)	P1—C1—C2—P2	−6.5 (6)
O1W—Cs1—O1ⁱⁱⁱ—P1ⁱⁱⁱ	122.1 (3)	P1—C1—C2—C3	172.7 (4)
O4—Cs1—O1ⁱⁱⁱ—Cs1ⁱⁱⁱ	59.28 (12)	C6—C1—C2—P2	178.1 (4)
O4—Cs1—O1ⁱⁱⁱ—P1ⁱⁱⁱ	−123.8 (2)	C6—C1—C2—C3	−2.8 (7)
O1—Cs1—O3^iv—P1^iv	−14.9 (3)	P1—C1—C6—C5	−173.3 (4)
O1W—Cs1—O3^iv—P1^iv	25.8 (3)	C2—C1—C6—C5	2.5 (7)
O4—Cs1—O3^iv—P1^iv	−55.9 (3)	P2—C2—C3—C4	−179.6 (4)
O1—Cs1—O4^v—Cs1^v	−22.22 (15)	C1—C2—C3—C4	1.2 (7)
O1—Cs1—O4^v—P2^v	101.24 (17)	C2—C3—C4—C5	0.9 (7)
O1W—Cs1—O4^v—Cs1^v	−65.93 (19)	C2—C3—C4—C8	−177.0 (5)
O1W—Cs1—O4^v—P2^v	57.5 (2)	C3—C4—C5—C6	−1.2 (7)
O4—Cs1—O4^v—Cs1^v	0.00 (10)	C3—C4—C5—C7	179.1 (5)
O4—Cs1—O4^v—P2^v	123.46 (19)	C8—C4—C5—C6	176.7 (5)
O1—Cs1—O6^v—P2^v	−99.78 (17)	C8—C4—C5—C7	−2.9 (7)
O1W—Cs1—O6^v—P2^v	−147.10 (15)	C4—C5—C6—C1	−0.5 (7)
O4—Cs1—O6^v—P2^v	−45.83 (17)	C7—C5—C6—C1	179.2 (5)

Symmetry codes: (i) −x+1, y+1/2, −z+3/2; (ii) −x+2, y+1/2, −z+3/2; (iii) −x+1, −y+1, −z+1; (iv) −x+1, −y+1, −z+2; (v) −x+2, −y+1, −z+1; (vi) −x+2, −y+1, −z+2; (vii) −x+1, y−1/2, −z+3/2; (viii) −x+2, y−1/2, −z+3/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O6^ix	0.95 (1)	1.59 (12)	2.528 (5)	172 (5)
O5—H5···O2	0.94 (1)	1.60 (12)	2.545 (5)	175 (5)
O1W—H1X···O2^iv	0.95 (1)	1.64 (16)	2.553 (5)	160 (4)
O1W—H1Y···O1	0.96 (1)	1.66 (11)	2.526 (5)	149 (4)
O1W—H1Z···O4ⁱⁱⁱ	0.95 (1)	1.56 (15)	2.485 (5)	162 (4)

Symmetry codes: (iii) −x+1, −y+1, −z+1; (iv) −x+1, −y+1, −z+2; (ix) x−1, y, z.

Acknowledgements

(a) Funding sources and entities: Fundação para a Ciência e a Tecnologia (FCT, Portugal), the European Union, QREN, FEDER through Programa Operacional Factores de Competitividade (COMPETE), CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013) financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement. (b) Projects and individual grants: We wish to thank the FCT for funding the R&D project FCOMP-01–0124-FEDER-041282 (Ref. FCT EXPL/CTM-NAN/0013/2013), and also CICECO for specific funding towards the purchase of the single-crystal diffractometer. The FCT is also gratefully acknowledged for the post-doctoral research grant No. SFRH/BPD/79000/2011 (to NV) and the PhD research grant No. SFRH/BD/84231/2012 (to RFM).

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