Rb₂CaCu₆(PO₄)₄O₂, a novel oxophosphate with a shchurovskyite-type topology: synthesis, structure, magnetic properties and crystal chemistry of rubidium copper phosphates

Single crystals of Rb₂CaCu₆(PO₄)₄O₂ were synthesized by a hydrothermal method in the multicomponent system CuCl₂–Ca(OH)₂–RbCl–B₂O₃–Rb₃PO₄. The synthesis was carried out in the temperature range from 690 to 700 K and at the general pressure of 480–500 atm [1 atm = 101.325 kPa] from the mixture in the molar ratio 2CuO:CaO:Rb₂O:B₂O₃:P₂O₅. The crystals studied by single-crystal X-ray analysis were found to be monoclinic, space group C2, a = 16.8913 (4), b = 5.6406 (1), c = 8.3591 (3) Å, β = 93.919 (3)°, V = 794.57 (4) ų. The crystal structure of Rb₂CaCu₆(PO₄)₄O₂ is similar to that of shchurovskyite and dmisokolovite and is based upon a heteropolyhedral open framework formed by polar layers of copper polyhedra linked via isolated PO₄ tetrahedra. The presence of well-isolated 2D heteropolyhedral layers in the title compound suggests low-dimensional magnetic behavior which is masked, however, by the fierce competition between multiple ferromagnetic and antiferromagnetic exchange interactions. At T_C = 25 K, Rb₂CaCu₆(PO₄)₄O₂ reaches a magnetically ordered state with large residual magnetization.

Computing details

(I)

Crystal data

CaCu6O18P4Rb2	F(000) = 944
Mr = 1004.2	Dx = 4.196 Mg m^−3
Monoclinic, C2	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: C 2y	Cell parameters from 21970 reflections
a = 16.8913 (4) Å	θ = 4.5–56.1°
b = 5.6406 (1) Å	µ = 14.80 mm^−1
c = 8.3591 (3) Å	T = 293 K
β = 93.919 (3)°	Irregular grain, green
V = 794.57 (4) Å^3	0.24 × 0.22 × 0.15 mm
Z = 2

Data collection

Xcalibur, Sapphire3 with high theta cut-off diffractometer	5108 independent reflections
Radiation source: X-ray tube	3914 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.064
Detector resolution: 16.0628 pixels mm^-1	θmax = 56.1°, θmin = 4.5°
Absorption correction: multi-scan	h = −39→38
Tmin = 0.488, Tmax = 1.000	k = −12→13
21970 measured reflections	l = −19→16

Refinement

Refinement on F	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.000324F^2)
R[F^2 > 2σ(F^2)] = 0.050	(Δ/σ)max = 0.041
wR(F^2) = 0.050	Δρmax = 1.21 e Å^−3
S = 0.97	Δρmin = −1.26 e Å^−3
5108 reflections	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
153 parameters	Extinction coefficient: 370 (50)
0 restraints	Absolute structure: 0 of Friedel pairs used in the refinement
1 constraint

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Rb1	0.29009 (5)	0.20623 (17)	0.15752 (15)	0.03440 (16)
Cu1	0.32143 (2)	−0.25821 (9)	0.47267 (5)	0.00957 (9)
Cu2	0.5	0.42111 (10)	0.5	0.01119 (14)
Cu3	0.5	0.91300 (10)	0.5	0.00924 (13)
Cu4	0.08396 (3)	0.18216 (9)	0.22561 (5)	0.01106 (9)
Ca1	0.5	0.17531 (18)	0	0.01053 (18)
P1	0.64484 (5)	0.20090 (15)	0.35178 (10)	0.00694 (16)
P2	0.41010 (5)	−0.29307 (17)	0.14827 (11)	0.00888 (17)
O1	0.33645 (15)	−0.2696 (6)	0.2451 (3)	0.0136 (6)
O2	0.57620 (14)	0.1756 (5)	0.4677 (3)	0.0117 (5)
O4	0.07301 (13)	0.1655 (4)	0.4508 (3)	0.0076 (4)
O5	0.47637 (17)	−0.1144 (5)	0.2054 (4)	0.0153 (7)
O6	0.4428 (2)	−0.5435 (5)	0.1571 (4)	0.0174 (8)
O7	0.3822 (2)	−0.2162 (7)	−0.0248 (4)	0.0188 (8)
O8	0.71142 (15)	0.3504 (5)	0.4381 (4)	0.0124 (6)
O9	0.67462 (15)	−0.0515 (4)	0.3216 (3)	0.0088 (5)
O10	0.61381 (18)	0.3236 (5)	0.1953 (4)	0.0135 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Rb1	0.02171 (19)	0.0191 (2)	0.0644 (4)	0.00215 (16)	0.0179 (2)	−0.0025 (2)
Cu1	0.00617 (12)	0.01417 (16)	0.00841 (16)	0.00142 (11)	0.00088 (12)	−0.00108 (13)
Cu2	0.0087 (2)	0.00583 (17)	0.0199 (3)	0	0.0073 (2)	0
Cu3	0.0080 (2)	0.00605 (16)	0.0142 (3)	0	0.0041 (2)	0
Cu4	0.01258 (15)	0.01362 (16)	0.00720 (16)	0.00153 (13)	0.00222 (13)	0.00069 (14)
Ca1	0.0136 (3)	0.0096 (3)	0.0087 (3)	0	0.0026 (3)	0
P1	0.0062 (2)	0.0064 (3)	0.0083 (3)	−0.0002 (2)	0.0009 (2)	−0.0002 (2)
P2	0.0081 (3)	0.0117 (3)	0.0069 (3)	0.0022 (2)	0.0014 (2)	0.0009 (3)
O1	0.0107 (8)	0.0204 (11)	0.0102 (10)	0.0020 (9)	0.0038 (8)	0.0004 (9)
O2	0.0099 (8)	0.0092 (7)	0.0169 (11)	0.0005 (7)	0.0069 (8)	0.0003 (9)
O4	0.0067 (7)	0.0090 (7)	0.0072 (8)	−0.0009 (6)	0.0006 (6)	−0.0001 (7)
O5	0.0110 (10)	0.0160 (11)	0.0186 (14)	−0.0035 (8)	−0.0006 (10)	0.0010 (9)
O6	0.0181 (13)	0.0131 (10)	0.0210 (16)	0.0064 (9)	0.0016 (12)	−0.0015 (10)
O7	0.0200 (12)	0.0291 (15)	0.0074 (11)	0.0110 (11)	0.0007 (10)	0.0014 (10)
O8	0.0057 (8)	0.0122 (9)	0.0193 (13)	−0.0007 (7)	0.0004 (8)	−0.0050 (9)
O9	0.0088 (8)	0.0077 (7)	0.0101 (10)	0.0018 (6)	0.0022 (8)	−0.0001 (6)
O10	0.0174 (11)	0.0123 (9)	0.0102 (11)	0.0032 (8)	−0.0020 (9)	0.0007 (8)

Geometric parameters (Å, º)

Rb1—Rb1^i	4.0294 (15)	Cu3—O2^iv	1.993 (3)
Rb1—Rb1^ii	4.0294 (15)	Cu3—O2^x	1.993 (3)
Rb1—Cu1	3.7272 (12)	Cu3—O4^ix	1.925 (2)
Rb1—Cu1^iii	3.7337 (13)	Cu3—O4^iii	1.925 (2)
Rb1—Cu4	3.5688 (11)	Cu4—O4	1.907 (3)
Rb1—Ca1	3.8696 (10)	Cu4—O7^ii	1.899 (3)
Rb1—P2	3.4740 (13)	Ca1—O5	2.423 (3)
Rb1—P2^iv	3.4804 (13)	Ca1—O5^xi	2.423 (3)
Rb1—O1	2.876 (3)	Ca1—O6^iv	2.312 (3)
Rb1—O6^iv	2.940 (3)	Ca1—O6^xii	2.312 (3)
Rb1—O9^v	2.814 (3)	P1—O2	1.568 (3)
Cu1—O1	1.937 (3)	P1—O8	1.544 (3)
Cu1—O4^vi	1.902 (2)	P1—O9	1.536 (2)
Cu1—O8^vii	1.959 (3)	P1—O10	1.540 (3)
Cu2—O2	1.922 (3)	P2—O1	1.536 (3)
Cu2—O2^viii	1.922 (3)	P2—O5	1.557 (3)
Cu2—O4^ix	1.913 (2)	P2—O6	1.517 (3)
Cu2—O4^iii	1.913 (2)	P2—O7	1.553 (3)
Rb1^i—Rb1—Rb1^ii	88.84 (3)	O2^viii—Cu2—O4^ix	175.59 (11)
Rb1^i—Rb1—Cu1	89.72 (3)	O2^viii—Cu2—O4^iii	92.37 (11)
Rb1^i—Rb1—Cu1^iii	114.37 (3)	O4^ix—Cu2—O4^iii	87.78 (10)
Rb1^i—Rb1—Cu4	77.85 (2)	O2^iv—Cu3—O2^x	83.97 (11)
Rb1^i—Rb1—Ca1	91.20 (3)	O2^iv—Cu3—O4^ix	94.64 (10)
Rb1^i—Rb1—P2	65.71 (3)	O2^iv—Cu3—O4^iii	175.41 (11)
Rb1^i—Rb1—P2^iv	136.36 (4)	O2^x—Cu3—O4^ix	175.41 (11)
Rb1^i—Rb1—O1	65.59 (6)	O2^x—Cu3—O4^iii	94.64 (10)
Rb1^i—Rb1—O6^iv	126.22 (8)	O4^ix—Cu3—O4^iii	87.07 (10)
Rb1^i—Rb1—O9^v	116.45 (6)	Rb1—Cu4—O4	108.72 (7)
Rb1^ii—Rb1—Cu1	168.25 (3)	Rb1—Cu4—O7^ii	59.43 (10)
Rb1^ii—Rb1—Cu1^iii	109.72 (3)	O4—Cu4—O7^ii	160.61 (13)
Rb1^ii—Rb1—Cu4	80.96 (2)	Rb1—Ca1—Rb1^xi	174.83 (4)
Rb1^ii—Rb1—Ca1	94.82 (3)	Rb1—Ca1—O5	65.80 (7)
Rb1^ii—Rb1—P2	136.34 (4)	Rb1—Ca1—O5^xi	118.08 (7)
Rb1^ii—Rb1—P2^iv	65.65 (3)	Rb1—Ca1—O6^iv	49.27 (8)
Rb1^ii—Rb1—O1	153.24 (7)	Rb1—Ca1—O6^xii	126.20 (9)
Rb1^ii—Rb1—O6^iv	85.34 (7)	Rb1^xi—Ca1—O5	118.08 (7)
Rb1^ii—Rb1—O9^v	76.44 (6)	Rb1^xi—Ca1—O5^xi	65.80 (7)
Cu1—Rb1—Cu1^iii	60.52 (2)	Rb1^xi—Ca1—O6^iv	126.20 (9)
Cu1—Rb1—Cu4	87.34 (3)	Rb1^xi—Ca1—O6^xii	49.27 (8)
Cu1—Rb1—Ca1	96.87 (2)	O5—Ca1—O5^xi	95.21 (11)
Cu1—Rb1—P2	52.48 (2)	O5—Ca1—O6^iv	87.97 (11)
Cu1—Rb1—P2^iv	122.09 (3)	O5—Ca1—O6^xii	163.81 (11)
Cu1—Rb1—O1	30.82 (6)	O5^xi—Ca1—O6^iv	163.81 (11)
Cu1—Rb1—O6^iv	104.84 (7)	O5^xi—Ca1—O6^xii	87.97 (11)
Cu1—Rb1—O9^v	93.81 (6)	O6^iv—Ca1—O6^xii	93.39 (12)
Cu1^iii—Rb1—Cu4	46.927 (17)	O2—P1—O8	107.86 (16)
Cu1^iii—Rb1—Ca1	144.10 (3)	O2—P1—O9	106.34 (15)
Cu1^iii—Rb1—P2	112.96 (3)	O2—P1—O10	110.06 (16)
Cu1^iii—Rb1—P2^iv	107.60 (3)	O8—P1—O9	110.26 (14)
Cu1^iii—Rb1—O1	89.04 (6)	O8—P1—O10	110.24 (16)
Cu1^iii—Rb1—O6^iv	117.87 (8)	O9—P1—O10	111.93 (16)
Cu1^iii—Rb1—O9^v	33.34 (5)	Rb1^xiii—P2—Rb1	108.40 (3)
Cu4—Rb1—Ca1	168.29 (4)	Rb1^xiii—P2—O1	64.17 (12)
Cu4—Rb1—P2	123.36 (3)	Rb1^xiii—P2—O5	157.84 (13)
Cu4—Rb1—P2^iv	127.63 (3)	Rb1^xiii—P2—O6	56.88 (13)
Cu4—Rb1—O1	100.11 (6)	Rb1^xiii—P2—O7	96.15 (14)
Cu4—Rb1—O6^iv	152.11 (7)	Rb1—P2—O1	54.78 (12)
Cu4—Rb1—O9^v	39.15 (5)	Rb1—P2—O5	82.91 (12)
Ca1—Rb1—P2	53.58 (2)	Rb1—P2—O6	164.80 (14)
Ca1—Rb1—P2^iv	58.69 (3)	Rb1—P2—O7	69.74 (14)
Ca1—Rb1—O1	78.74 (6)	O1—P2—O5	111.94 (17)
Ca1—Rb1—O6^iv	36.58 (7)	O1—P2—O6	111.10 (19)
Ca1—Rb1—O9^v	150.39 (6)	O1—P2—O7	105.17 (17)
P2—Rb1—P2^iv	108.40 (3)	O5—P2—O6	109.68 (17)
P2—Rb1—O1	25.86 (6)	O5—P2—O7	105.74 (19)
P2—Rb1—O6^iv	82.87 (6)	O6—P2—O7	113.1 (2)
P2—Rb1—O9^v	146.04 (7)	Rb1—O1—Cu1	99.64 (12)
P2^iv—Rb1—O1	127.88 (6)	Rb1—O1—P2	99.36 (15)
P2^iv—Rb1—O6^iv	25.59 (6)	Cu1—O1—P2	133.29 (16)
P2^iv—Rb1—O9^v	92.34 (6)	Cu2—O2—Cu3^xiii	94.11 (11)
O1—Rb1—O6^iv	102.99 (8)	Cu2—O2—P1	123.49 (16)
O1—Rb1—O9^v	120.98 (8)	Cu3^xiii—O2—P1	131.54 (17)
O6^iv—Rb1—O9^v	113.87 (9)	Cu1^iii—O4—Cu2^vii	133.95 (13)
Rb1—Cu1—Rb1^vi	124.58 (3)	Cu1^iii—O4—Cu3^vii	111.33 (12)
Rb1—Cu1—O1	49.54 (10)	Cu1^iii—O4—Cu4	99.72 (11)
Rb1—Cu1—O4^vi	118.76 (8)	Cu2^vii—O4—Cu3^vii	92.57 (10)
Rb1—Cu1—O8^vii	65.70 (9)	Cu2^vii—O4—Cu4	110.80 (12)
Rb1^vi—Cu1—O1	156.71 (8)	Cu3^vii—O4—Cu4	106.37 (11)
Rb1^vi—Cu1—O4^vi	102.94 (8)	Ca1—O5—P2	111.64 (17)
Rb1^vi—Cu1—O8^vii	67.17 (10)	Rb1^xiii—O6—Ca1^xiii	94.14 (10)
O1—Cu1—O4^vi	98.04 (11)	Rb1^xiii—O6—P2	97.53 (15)
O1—Cu1—O8^vii	92.97 (12)	Ca1^xiii—O6—P2	140.9 (2)
O4^vi—Cu1—O8^vii	168.04 (12)	Cu4^i—O7—P2	130.4 (2)
O2—Cu2—O2^viii	87.82 (11)	Cu1^ix—O8—P1	123.47 (17)
O2—Cu2—O4^ix	92.37 (11)	Rb1^xiv—O9—P1	140.85 (15)
O2—Cu2—O4^iii	175.59 (11)

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