Structure and magnetic properties of a new iron(II) citrate coordination polymer

The new compound [Fe(H₂cit)(H₂O)]_n (NICS-2) is the first neutral ferrous citrate carboxylate that has been synthesized up to now. The iron citrate coordination polymer was hydrothermally synthesized and the structure was solved using single-crystal X-ray diffraction. It crystallizes in an orthorhombic space group P2₁2₁2₁ (No. 19), with a = 5.9470 (4), b = 10.4021 (5), c = 13.5773 (7) Å, V = 839.91 (8) ų, Z = 4. Its structure consists of one-dimensional chains of corner-sharing Fe^IIO₆ octahedra that are additionally cross-linked with citrate ligands. Chains are additionally stabilized into a pseudo-three-dimensional structure by hydrogen bonds. The measurement of magnetic properties revealed that the magnetic moment is almost constant above 100 K (μ_eff = 5.1 µ_B), but decreases rapidly below this temperature most probably due to the appearance of weak antiferromagnetic interactions between Fe atoms. Additionally, analysis of Mossbauer spectra confirmed the presence of divalent Fe atoms in the structure. Thermogravimetrical and X-ray high-temperature diffraction analyses showed the thermal stability of the material up to 548 K.

S1. Experimental

S1.1. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

S2. Results and discussion

Computing details

Data collection: CrysAlis PRO (Agilent, 2011); cell refinement: CrysAlis PRO (Agilent, 2011); data reduction: CrysAlis PRO (Agilent, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: ORTEP-3, DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXL2013, WinGX (Faruggia, 2012).

Figures

(I)

Crystal data

C6H8FeO8	Dx = 2.088 Mg m^−3
Mr = 263.97	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121	Cell parameters from 4978 reflections
a = 5.9470 (4) Å	θ = 3.0–30.3°
b = 10.4021 (5) Å	µ = 1.82 mm^−1
c = 13.5773 (7) Å	T = 293 K
V = 839.91 (8) Å^3	Prism, colourless
Z = 4	0.35 × 0.18 × 0.17 mm
F(000) = 536

Data collection

SuperNova, Dual, Cu at zero, Atlas diffractometer	2321 independent reflections
Radiation source: SuperNova (Mo) X-ray	2193 reflections with I > 2σ(I)
Detector resolution: 10.4933 pixels mm^-1	Rint = 0.065
/w scans	θmax = 30.4°, θmin = 3.0°
Absorption correction: multi-scan CrysAlis PRO, (Agilent, 2011)	h = −7→8
Tmin = 0.568, Tmax = 0.747	k = −11→14
8571 measured reflections	l = −18→18

Refinement

Refinement on F^2	Hydrogen site location: mixed
Least-squares matrix: full	Only H-atom displacement parameters refined
R[F^2 > 2σ(F^2)] = 0.036	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.102	(Δ/σ)max = 0.001
S = 0.81	Δρmax = 0.81 e Å^−3
2321 reflections	Δρmin = −0.71 e Å^−3
156 parameters	Absolute structure: Flack x determined using 843 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons and Flack (2004), Acta Cryst. A60, s61).
4 restraints	Absolute structure parameter: −0.009 (12)

Special details

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

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

	x	y	z	Uiso*/Ueq
Fe1	0.41542 (7)	0.33217 (4)	0.94876 (3)	0.01198 (16)
O1	0.5451 (4)	0.4980 (2)	0.88421 (18)	0.0145 (5)
O2	0.0928 (4)	0.3672 (3)	0.8894 (2)	0.0210 (5)
O3	0.2836 (4)	0.1695 (2)	1.02115 (17)	0.0140 (5)
O4	0.5276 (4)	0.2360 (2)	0.81842 (17)	0.0161 (5)
O5	0.6089 (5)	0.2249 (2)	0.65950 (18)	0.0192 (5)
O6	0.9071 (7)	0.6263 (3)	1.0001 (2)	0.0301 (7)
O7	0.8753 (6)	0.8057 (3)	0.9114 (2)	0.0310 (7)
O8	0.3431 (5)	0.4322 (3)	1.0811 (2)	0.0251 (6)
C1	0.7611 (5)	0.4767 (3)	0.8414 (2)	0.0102 (5)
C2	−0.1067 (5)	0.3860 (3)	0.9094 (2)	0.0114 (6)
C3	0.7328 (7)	0.4119 (3)	0.7408 (2)	0.0154 (6)
H3A	0.6505	0.4700	0.6981	0.025 (12)*
H3B	0.8807	0.3999	0.7122	0.040 (16)*
C4	0.6125 (6)	0.2829 (3)	0.7410 (2)	0.0132 (6)
C5	0.8875 (6)	0.6041 (3)	0.8271 (2)	0.0138 (6)
H5A	1.0417	0.5853	0.8089	0.019 (11)*
H5B	0.8193	0.6505	0.7728	0.040 (15)*
C6	0.8888 (6)	0.6902 (3)	0.9169 (3)	0.0162 (6)
H1	0.487 (7)	0.563 (3)	0.858 (3)	0.012 (11)*
H6	0.906 (10)	0.681 (5)	1.044 (3)	0.050 (19)*
H8A	0.223 (6)	0.403 (4)	1.106 (3)	0.018 (11)*
H8B	0.349 (10)	0.512 (3)	1.086 (4)	0.038 (16)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.0107 (2)	0.0113 (3)	0.0138 (2)	−0.00036 (16)	0.00133 (15)	0.00232 (17)
O1	0.0114 (11)	0.0103 (11)	0.0217 (11)	0.0026 (9)	0.0035 (8)	0.0059 (9)
O2	0.0113 (11)	0.0262 (13)	0.0255 (12)	0.0015 (10)	−0.0010 (10)	0.0061 (10)
O3	0.0160 (11)	0.0101 (11)	0.0161 (10)	0.0005 (9)	−0.0001 (8)	0.0041 (9)
O4	0.0205 (13)	0.0144 (11)	0.0136 (11)	−0.0034 (9)	0.0008 (8)	0.0000 (9)
O5	0.0258 (14)	0.0148 (11)	0.0171 (11)	−0.0053 (11)	0.0023 (11)	−0.0039 (9)
O6	0.057 (2)	0.0171 (13)	0.0166 (12)	−0.0058 (15)	−0.0058 (13)	−0.0034 (10)
O7	0.044 (2)	0.0113 (12)	0.0374 (16)	−0.0022 (12)	0.0046 (15)	−0.0029 (11)
O8	0.0328 (15)	0.0147 (13)	0.0277 (14)	−0.0032 (11)	0.0091 (11)	−0.0032 (11)
C1	0.0098 (13)	0.0082 (13)	0.0127 (12)	−0.0008 (11)	0.0005 (10)	0.0009 (10)
C2	0.0126 (14)	0.0072 (13)	0.0144 (12)	0.0005 (11)	−0.0008 (11)	−0.0005 (11)
C3	0.0222 (18)	0.0134 (15)	0.0107 (12)	−0.0036 (13)	0.0000 (12)	−0.0005 (11)
C4	0.0121 (15)	0.0121 (13)	0.0155 (13)	0.0008 (11)	−0.0018 (12)	0.0003 (11)
C5	0.0177 (16)	0.0102 (14)	0.0136 (12)	−0.0044 (12)	0.0009 (12)	0.0004 (11)
C6	0.0127 (14)	0.0158 (15)	0.0201 (14)	−0.0031 (12)	0.0017 (12)	−0.0033 (12)

Geometric parameters (Å, º)

Fe1—O1	2.083 (2)	O5—C4	1.261 (4)
Fe1—O3	2.108 (2)	O6—C6	1.316 (5)
Fe1—O2	2.113 (3)	O7—C6	1.207 (5)
Fe1—O8	2.120 (3)	C1—C3	1.533 (4)
Fe1—O4	2.139 (2)	C1—C5	1.536 (4)
Fe1—O3^i	2.227 (2)	C1—C2^iii	1.536 (4)
O1—C1	1.427 (4)	C2—O3^ii	1.284 (4)
O2—C2	1.233 (4)	C2—C1^iv	1.536 (4)
O3—C2^i	1.284 (4)	C3—C4	1.521 (5)
O3—Fe1^ii	2.227 (2)	C5—C6	1.512 (5)
O4—C4	1.264 (4)
O1—Fe1—O3	177.01 (10)	Fe1—O3—Fe1^ii	117.23 (11)
O1—Fe1—O2	91.88 (10)	C4—O4—Fe1	129.2 (2)
O3—Fe1—O2	88.78 (10)	O1—C1—C3	109.4 (3)
O1—Fe1—O8	91.45 (10)	O1—C1—C5	111.0 (2)
O3—Fe1—O8	85.60 (10)	C3—C1—C5	108.7 (3)
O2—Fe1—O8	93.11 (12)	O1—C1—C2^iii	108.1 (2)
O1—Fe1—O4	85.62 (9)	C3—C1—C2^iii	108.8 (2)
O3—Fe1—O4	97.26 (9)	C5—C1—C2^iii	110.8 (3)
O2—Fe1—O4	92.78 (11)	O2—C2—O3^ii	125.4 (3)
O8—Fe1—O4	173.51 (12)	O2—C2—C1^iv	117.2 (3)
O1—Fe1—O3^i	73.72 (9)	O3^ii—C2—C1^iv	117.2 (3)
O3—Fe1—O3^i	105.88 (7)	C4—C3—C1	116.0 (3)
O2—Fe1—O3^i	164.58 (10)	O5—C4—O4	122.6 (3)
O8—Fe1—O3^i	92.74 (11)	O5—C4—C3	115.4 (3)
O4—Fe1—O3^i	80.88 (10)	O4—C4—C3	122.0 (3)
C1—O1—Fe1	112.12 (18)	C6—C5—C1	114.3 (3)
C2—O2—Fe1	144.8 (2)	O7—C6—O6	124.1 (3)
C2^i—O3—Fe1	121.0 (2)	O7—C6—C5	122.7 (3)
C2^i—O3—Fe1^ii	111.2 (2)	O6—C6—C5	113.2 (3)

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