Two new orthophosphates, BaMn2Fe(PO4)3 [barium dimanganese(II) iron(III) tris-(orthophosphate)] and SrMn2Fe(PO4)3 [strontium dimanganese(II) iron(III) tris-(orthophosphate)], were synthesized by solid-state reactions. They are isotypic and crystallize in the ortho-rhom-bic system with space group type Pbcn. Their crystal structures comprise infinite zigzag chains of edge-sharing FeO6 octa-hedra (point group symmetry .2.) and Mn2O10 double octa-hedra running parallel to [001], linked by two types of PO4 tetra-hedra. The so-formed three-dimensional framework delineates channels running along [001], in which the alkaline earth cations (site symmetry .2.) are located within a neighbourhood of eight O atoms.
Two new orthophosphates, BaMn2Fe(PO4)3 [barium dimanganese(II) iron(III) tris-(orthophosphate)] and SrMn2Fe(PO4)3 [strontium dimanganese(II) iron(III) tris-(orthophosphate)], were synthesized by solid-state reactions. They are isotypic and crystallize in the ortho-rhom-bic system with space group type Pbcn. Their crystal structures comprise infinite zigzag chains of edge-sharing FeO6 octa-hedra (point group symmetry .2.) and Mn2O10 double octa-hedra running parallel to [001], linked by two types of PO4tetra-hedra. The so-formed three-dimensional framework delineates channels running along [001], in which the alkaline earth cations (site symmetry .2.) are located within a neighbourhood of eight O atoms.
Considerable attention has been devoted to the preparation of new inorganic materials with open-framework structures (Rao et al., 2001 ▸; Bouzidi et al., 2015 ▸) due to their structural diversity covering a wide range of chemical compositions (Zhou et al., 2002 ▸). In particular, transition-metal-based open-framework phosphates represent a highly attractive class of materials in industrial processes. In fact, their special framework structures lead to interesting properties that depend not only on the inclusion guest in the pores, but also on the chosen transition metal (Durio et al., 2002 ▸; López et al., 2004 ▸; Férey et al., 2005 ▸). Typical examples are ion-exchangers (Jignasa et al., 2006 ▸; Kullberg & Clearfield, 1981 ▸) and compounds with special magnetic (Chouaibi et al., 2001 ▸; Ferdov et al., 2008 ▸) and catalytic properties (Weng et al., 2009 ▸).In this context, our group focuses on the synthesis and characterization of new transition-metalphosphates crystallizing either in alluaudite- (Moore, 1971 ▸) or α-CrPO4-type structures (Attfield et al., 1988 ▸). In attempts to obtain new compounds belonging to the latter structure type, we have synthesized and structurally characterized several new phosphates, including those with oxidation states of both +II and +III for manganese. These compounds have the general formula MMnIIIMn2
II(PO4)3 (M = Pb, Sr, Ba) (Alhakmi et al., 2013a
▸,b
▸; Assani et al., 2013 ▸) and adopt the α-CrPO4 structure type. Recently, the phosphatesNa2Co2Fe(PO4)3 (Bouraima et al., 2015 ▸) and Na1.67Zn1.67Fe1.33(PO4)3 (Khmiyas et al., 2015 ▸) with an alluaudite-like structure were also reported. As a continuation in this regard, we have now extended our investigations to the quaternary system MO/MnO/Fe2O3/P2O5, where M is a divalent cation. The present work deals with the synthesis and the crystal structures of two new isotypic alkaline earth manganeseiron phosphates, namely, BaMn2Fe(PO4)3 and SrMn2Fe(PO4)3. Their structures show a similarity with that of AM
4(PO4)3phosphates where A is a monovalent cation and M a divalent cation (Daidouh et al., 1999 ▸; Assaaoudi et al., 2006 ▸).
Structural commentary
The principal building units in the crystal structures of both phosphates are distorted FeO6 and MnO6 octahedra, PO4tetrahedra and Ba2+ or Sr2+ cations as shown in Figs. 1 ▸ and 2 ▸. In each structure, two MnO6 octahedra are linked together by a common edge to give a Mn2O10 dimer to which FeO6 octahedra (point group symmetry .2.) are alternately connected on both sides. In this way, infinite zigzag chains parallel to [001] are formed (Fig. 3 ▸). Adjacent chains are linked together by sharing corners with two types of PO4tetrahedra, forming a layer-like arrangement parallel to (010) as shown in Fig. 4 ▸. Such layers are stacked along [010] to form a three-dimensional framework (Fig. 5 ▸) with two types of channels running parallel to [001] in which the alkaline earth cations are located on a twofold rotation axis. They are coordinated by eight oxygen atoms (Figs. 1 ▸ and 6 ▸), with bond lengths ranging from 2.6803 (10) to 2.8722 (11) Å for the BaO8 polyhedron and of 2.6020 (9) to 2.7358 (11) Å for the SrO8 polyhedron.
Figure 1
The principal building units in the structure of BaMn2Fe(PO4)3. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) x, −y + 1, z + ; (ii) −x + , −y + , −z + 2; (iii) x, y, z + 1; (iv) −x + , −y + , −z + 1; (v) −x + 1, y, −z + ; (vi) x, y, z − 1; (vii) −x + 1, y, −z + ; (viii) x − , −y + , z − ; (ix) −x + 1, −y + 1, −z + 1; (x) x, −y + 1, z − ; (xi) −x + 2, y, −z + ; (xii) −x + 2, −y + 1, −z + 1.]
Figure 2
The principal building units in the structure of SrMn2Fe(PO4)3. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) x, −y + 1, z + ; (ii) −x + , −y + , −z + 2; (iii) x, y, z + 1; (iv) −x + , −y + , −z + 1; (v) −x + 1, y, −z + ; (vi) x, y, z − 1; (vii) −x + 1, y, −z + ; (viii) x − , −y + , z − ; (ix) −x + 1, −y + 1, −z + 1; (x) x, −y + 1, z − ; (xi) −x + 2, y, −z + ; (xii) −x + 2, −y + 1, −z + 1.]
Figure 3
Edge-sharing [FeO6] octahedra and Mn2O10 dimers forming an infinite zigzag chain running parallel to [001]. Data are from BaMn2Fe(PO4)3.
Figure 4
A layer perpendicular to (010), resulting from the connection of metal oxide chains through PO4 tetrahedra. Data are from BaMn2Fe(PO4)3.
Figure 5
A view of stacked layers along [010]. Data are from BaMn2Fe(PO4)3.
Figure 6
Polyhedral representation of the BaMn2Fe(PO4)3 structure showing Ba2+ cations situated in channels running along [001].
Bond-valence-sum calculations (Brown & Altermatt, 1985 ▸) are in good agreement with the expected values for alkaline earth, manganese(II) and iron(III) cations and the phosphorus(V) atom. BaMn2Fe(PO4)3 (values in valence units): Ba2+ 2.10; Mn2+ 2.00; Fe3+ 3.12; PV 4.94. SrMn2Fe(PO4)3: Sr2+ 1.80; Mn2+ 2.07; Fe3+ 3.18; PV 5.00.
Database survey
A comparison between the structures of the title compounds and those of other phosphates such as the AM
4(PO4)3 compounds (A = monovalent cation and M = divalent cation) (Im et al., 2014 ▸), reveals that all these compounds crystallize with orthorhombic symmetry and nearly the same unit-cell parameters despite the differences between their chemical formulae and space groups. In order to give an illustrative picture of the similarity between these two formula types, we can write the general formula of AM
4(PO4)3 compounds as follows: M′2+(A
+
M
2+)M
2
2+(PO4)3 and that of the title compounds as M′2+Fe3+Mn2
2+(PO4)3. The principal structures of the title compounds and that of the AM
4(PO4)3 compounds are formed by stacking of the same infinite zigzag chains of edge-sharing octahedra. Furthermore, these structures are characterized by the presence of two types of channels in which the large cations are located.
Synthesis and crystallization
Single crystals of the title compounds were isolated as a result of solid-state reactions. Stoichiometric amounts of alkaline earth (M = Ba, Sr), manganese, iron and phosphate precursors in a molar ratio M:Mn:Fe:P = 1:2:1:3, were dissolved in 40 ml water that was placed into a 100 ml capacity pyrex glass beaker. The mixture was stirred at room temperature for 20 h and was evaporated under stirring at 363 K until dryness. The obtained black powder was ground in an agate mortar and pre-heated at 573 K in a platinum crucible for 24 h to eliminate gaseous materials. Subsequently, the resulting residue was reground and melted for 30 min at 1293 K, followed by slow cooling down to 1093 K at a rate 5K h−1 and a rapid cooling to room temperature by switching off the furnace. In the case of the BaO–MnO–Fe2O3–P2O5 system, the reaction product consisted of two types of crystals, viz. orange crystals of the title compound, BaMn2Fe(PO4)3, and dark-violet crystals that were identified to be another new phase. In the case of the SrO–MnO–Fe2O3–P2O5 system, the reaction product contained dark-brown crystals corresponding to the title compound, SrMn2Fe(PO4)3.
Refinement
Crystal data, data collection and structure refinement details for the two compounds are summarized in Table 1 ▸. For BaMn2Fe(PO4)3, the maximum and minimum remaining electron densities are located 0.60 and 0.42 Å from atom Ba1. For SrMn2Fe(PO4)3, they are 0.58 and 0.31 Å from Sr1.
Table 1
Experimental details
(I)
(II)
Crystal data
Chemical formula
BaMn2Fe(PO4)3
SrMn2Fe(PO4)3
Mr
587.98
538.25
Crystal system, space group
Orthorhombic, Pbcn
Orthorhombic, Pbcn
Temperature (K)
296
296
a, b, c (Å)
6.5899 (2), 17.6467 (4), 8.5106 (2)
6.4304 (3), 17.8462 (7), 8.4906 (3)
V (Å3)
989.70 (4)
974.37 (7)
Z
4
4
Radiation type
Mo Kα
Mo Kα
μ (mm−1)
8.41
10.00
Crystal size (mm)
0.32 × 0.25 × 0.22
0.30 × 0.27 × 0.23
Data collection
Diffractometer
Bruker X8 APEX
Bruker X8 APEX
Absorption correction
Multi-scan (SADABS; Krause et al., 2015 ▸)
Multi-scan (SADABS; Krause et al., 2015 ▸)
Tmin, Tmax
0.596, 0.748
0.404, 0.748
No. of measured, independent and observed [I > 2σ(I)] reflections
29422, 3088, 2731
23889, 2843, 2564
Rint
0.033
0.031
(sin θ/λ)max (Å−1)
0.907
0.887
Refinement
R[F2 > 2σ(F2)], wR(F2), S
0.018, 0.044, 1.05
0.021, 0.048, 1.08
No. of reflections
3088
2843
No. of parameters
89
89
Δρmax, Δρmin (e Å−3)
1.29, −1.11
1.19, −0.81
Computer programs: APEX2 and SAINT (Bruker, 2014 ▸), SHELXT2014 (Sheldrick, 2015a
▸), SHELXL2014 (Sheldrick, 2015b
▸), ORTEP-3 for Windows (Farrugia, 2012 ▸), DIAMOND (Brandenburg, 2006 ▸) and publCIF (Westrip, 2010 ▸).
Crystal structure: contains datablock(s) I, II, global. DOI: 10.1107/S2056989017006120/wm5384sup1.cifStructure factors: contains datablock(s) I. DOI: 10.1107/S2056989017006120/wm5384Isup2.hklStructure factors: contains datablock(s) II. DOI: 10.1107/S2056989017006120/wm5384IIsup3.hklCCDC references: 1545505, 1545504Additional supporting information: crystallographic information; 3D view; checkCIF report
BaMn2Fe(PO4)3
Dx = 3.946 Mg m−3
Mr = 587.98
Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbcn
Cell parameters from 3088 reflections
a = 6.5899 (2) Å
θ = 3.3–40.1°
b = 17.6467 (4) Å
µ = 8.41 mm−1
c = 8.5106 (2) Å
T = 296 K
V = 989.70 (4) Å3
Block, orange
Z = 4
0.32 × 0.25 × 0.22 mm
F(000) = 1092
Bruker X8 APEX diffractometer
3088 independent reflections
Radiation source: fine-focus sealed tube
2731 reflections with I > 2σ(I)
Graphite monochromator
Rint = 0.033
φ and ω scans
θmax = 40.1°, θmin = 3.3°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)
h = −8→11
Tmin = 0.596, Tmax = 0.748
k = −31→32
29422 measured reflections
l = −15→15
Refinement on F2
0 restraints
Least-squares matrix: full
w = 1/[σ2(Fo2) + (0.0178P)2 + 1.2088P] where P = (Fo2 + 2Fc2)/3
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.
x
y
z
Uiso*/Ueq
Ba1
0.5000
0.44269 (2)
0.7500
0.01037 (3)
Fe1
1.0000
0.31799 (2)
0.7500
0.00461 (4)
Mn1
0.83899 (3)
0.36570 (2)
0.39874 (2)
0.00647 (4)
P1
0.83270 (5)
0.17935 (2)
0.53771 (3)
0.00490 (5)
P2
1.0000
0.47123 (2)
0.7500
0.00513 (7)
O1
1.01958 (15)
0.12822 (6)
0.55338 (13)
0.01186 (16)
O2
0.66250 (15)
0.15480 (5)
0.64868 (11)
0.00865 (14)
O3
0.76365 (15)
0.17592 (5)
0.36487 (10)
0.00794 (14)
O4
0.88706 (16)
0.26335 (5)
0.57277 (11)
0.01031 (15)
O5
0.89269 (15)
0.41422 (5)
0.63609 (10)
0.00656 (13)
O6
0.83805 (16)
0.51729 (5)
0.83211 (12)
0.00988 (15)
U11
U22
U33
U12
U13
U23
Ba1
0.00562 (5)
0.01428 (5)
0.01119 (5)
0.000
−0.00082 (3)
0.000
Fe1
0.00537 (9)
0.00435 (8)
0.00411 (8)
0.000
0.00015 (7)
0.000
Mn1
0.00598 (7)
0.00785 (6)
0.00559 (7)
−0.00021 (5)
0.00041 (6)
0.00013 (5)
P1
0.00360 (11)
0.00666 (10)
0.00443 (10)
−0.00050 (9)
−0.00036 (9)
−0.00071 (8)
P2
0.00571 (17)
0.00355 (13)
0.00611 (15)
0.000
0.00000 (13)
0.000
O1
0.0058 (4)
0.0170 (4)
0.0128 (4)
0.0047 (3)
−0.0016 (3)
−0.0004 (3)
O2
0.0064 (3)
0.0126 (3)
0.0070 (3)
−0.0017 (3)
0.0007 (3)
0.0021 (3)
O3
0.0066 (4)
0.0127 (3)
0.0045 (3)
0.0002 (3)
−0.0018 (3)
−0.0017 (3)
O4
0.0136 (4)
0.0087 (3)
0.0086 (3)
−0.0047 (3)
−0.0002 (3)
−0.0028 (3)
O5
0.0084 (3)
0.0058 (3)
0.0055 (3)
−0.0007 (3)
−0.0009 (3)
−0.0003 (2)
O6
0.0091 (4)
0.0071 (3)
0.0134 (4)
0.0017 (3)
0.0011 (3)
−0.0031 (3)
Ba1—O6
2.6803 (10)
Mn1—O6vi
2.1413 (9)
Ba1—O6i
2.6803 (10)
Mn1—O1ii
2.1466 (10)
Ba1—O3ii
2.7861 (9)
Mn1—O2vii
2.1587 (9)
Ba1—O3iii
2.7861 (9)
Mn1—O2v
2.1997 (10)
Ba1—O5
2.8087 (10)
Mn1—O5
2.2223 (9)
Ba1—O5i
2.8087 (10)
Mn1—O4
2.3572 (10)
Ba1—O1ii
2.8722 (11)
P1—O2
1.5289 (10)
Ba1—O1iii
2.8722 (11)
P1—O1
1.5325 (10)
Fe1—O4
1.9387 (9)
P1—O3
1.5409 (9)
Fe1—O4iv
1.9387 (9)
P1—O4
1.5540 (9)
Fe1—O3v
1.9965 (9)
P2—O6
1.5126 (10)
Fe1—O3iii
1.9965 (9)
P2—O6iv
1.5126 (10)
Fe1—O5iv
2.0792 (9)
P2—O5
1.5659 (9)
Fe1—O5
2.0793 (9)
P2—O5iv
1.5660 (9)
O6—Ba1—O6i
121.17 (4)
O4iv—Fe1—O5iv
85.00 (4)
O6—Ba1—O3ii
157.68 (3)
O3v—Fe1—O5iv
83.59 (4)
O6i—Ba1—O3ii
79.21 (3)
O3iii—Fe1—O5iv
91.36 (4)
O6—Ba1—O3iii
79.21 (3)
O4—Fe1—O5
85.00 (4)
O6i—Ba1—O3iii
157.68 (3)
O4iv—Fe1—O5
154.09 (4)
O3ii—Ba1—O3iii
82.60 (4)
O3v—Fe1—O5
91.36 (4)
O6—Ba1—O5
53.99 (3)
O3iii—Fe1—O5
83.59 (4)
O6i—Ba1—O5
139.79 (3)
O5iv—Fe1—O5
70.50 (5)
O3ii—Ba1—O5
105.04 (3)
O6vi—Mn1—O1ii
89.96 (4)
O3iii—Ba1—O5
58.11 (3)
O6vi—Mn1—O2vii
84.29 (4)
O6—Ba1—O5i
139.79 (3)
O1ii—Mn1—O2vii
101.01 (4)
O6i—Ba1—O5i
53.99 (3)
O6vi—Mn1—O2v
96.48 (4)
O3ii—Ba1—O5i
58.11 (3)
O1ii—Mn1—O2v
173.39 (4)
O3iii—Ba1—O5i
105.04 (3)
O2vii—Mn1—O2v
78.23 (4)
O5—Ba1—O5i
159.39 (3)
O6vi—Mn1—O5
82.51 (4)
O6—Ba1—O1ii
114.27 (3)
O1ii—Mn1—O5
87.96 (4)
O6i—Ba1—O1ii
90.97 (3)
O2vii—Mn1—O5
164.03 (4)
O3ii—Ba1—O1ii
51.86 (3)
O2v—Mn1—O5
94.35 (4)
O3iii—Ba1—O1ii
87.88 (3)
O6vi—Mn1—O4
154.91 (4)
O5—Ba1—O1ii
64.56 (3)
O1ii—Mn1—O4
92.91 (4)
O5i—Ba1—O1ii
105.89 (3)
O2vii—Mn1—O4
119.45 (3)
O6—Ba1—O1iii
90.97 (3)
O2v—Mn1—O4
81.90 (4)
O6i—Ba1—O1iii
114.27 (3)
O5—Mn1—O4
72.70 (3)
O3ii—Ba1—O1iii
87.88 (3)
O2—P1—O1
111.65 (6)
O3iii—Ba1—O1iii
51.86 (3)
O2—P1—O3
111.22 (5)
O5—Ba1—O1iii
105.89 (3)
O1—P1—O3
107.29 (6)
O5i—Ba1—O1iii
64.55 (3)
O2—P1—O4
108.71 (5)
O1ii—Ba1—O1iii
128.34 (4)
O1—P1—O4
111.08 (6)
O4—Fe1—O4iv
120.35 (6)
O3—P1—O4
106.79 (5)
O4—Fe1—O3v
88.85 (4)
O6—P2—O6iv
115.00 (8)
O4iv—Fe1—O3v
94.22 (4)
O6—P2—O5
108.22 (5)
O4—Fe1—O3iii
94.22 (4)
O6iv—P2—O5
112.20 (5)
O4iv—Fe1—O3iii
88.85 (4)
O6—P2—O5iv
112.20 (5)
O3v—Fe1—O3iii
173.83 (5)
O6iv—P2—O5iv
108.22 (5)
O4—Fe1—O5iv
154.09 (4)
O5—P2—O5iv
100.05 (7)
SrMn2Fe(PO4)3
Dx = 3.669 Mg m−3
Mr = 538.25
Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbcn
Cell parameters from 2843 reflections
a = 6.4304 (3) Å
θ = 3.3–39.1°
b = 17.8462 (7) Å
µ = 10.00 mm−1
c = 8.4906 (3) Å
T = 296 K
V = 974.37 (7) Å3
Block, dark brown
Z = 4
0.30 × 0.27 × 0.23 mm
F(000) = 1020
Bruker X8 APEX diffractometer
2843 independent reflections
Radiation source: fine-focus sealed tube
2564 reflections with I > 2σ(I)
Graphite monochromator
Rint = 0.031
φ and ω scans
θmax = 39.1°, θmin = 3.3°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)
h = −11→10
Tmin = 0.404, Tmax = 0.748
k = −31→31
23889 measured reflections
l = −8→15
Refinement on F2
0 restraints
Least-squares matrix: full
w = 1/[σ2(Fo2) + (0.0183P)2 + 1.2279P] where P = (Fo2 + 2Fc2)/3
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.