An inter­penetrating primitive cubic net formed by hydrogen bonds and coordination bonds in catena-poly[[bis­(methanol-[kappa]O)bis­(thio­cyanato-[kappa]N)iron(II)]-[mu]-1,2-bis(4-pyridyl­methylene)hydrazine-[kappa]²N:N']

In the title compound, [Fe(NCS)₂(C₁₂H₁₀N₄)(CH₄O)₂]_n, at 153 (2) K, the Fe atom is located on an inversion centre, as is the centre of the N-N bond in the ligand mol­ecule. The structure contains a one-dimensional coordination polymer with an Fe...Fe distance of 15.866 (7) Å and can be described as two inter­penetrating six-connected primitive cubic (pcu) three-dimensional networks when additional inter­molecular O-H...S hydrogen bonds are taken into account. The compound is not isostructural with the corresponding Mn^II compound as they differ in the rotation around the M-O bond by 90°, giving rise to completely different hydrogen-bond patterns. This study demonstrates the impact of conformational differences on the final supramolecular arrangement.

S1. Comment

Great interest is currently devoted to exploring the versatility of coordination and hydrogen bonds with the aim of obtaining rational control over the creation of molecular framework materials (Delgado-Friedrichs et al., 2007; Champness, 2006; Öhrström & Larsson, 2005). In this context, the monodentate rigid rod-like ligand 1,4-bis(4-pyridyl)methylene hydrazine has frequently been used, giving rise to one- and two-dimensional frameworks (Diskin-Posner et al., 2002; Shi et al., 2002; Patra & Goldberg, 2003; Kennedy et al., 2005; Granifo et al., 2006; Zhang et al., 2006; Zhou et al., 2006; Dong et al., 2000; Shen, 2003). 1,4-Bis(4-pyridyl)methylene hydrazine and similar ligands have limited influence over network topology since in most complexes the ligand occupies only two metal coordination sites, offering a weak influence over the rest of the metal coordination environment. However, further support of the molecular architecture may be acquired through hydrogen bonds. We reported recently on two different hydrogen-bonding motifs observed in compounds of this ligand, depending on the counterions (Ghazzali et al., 2007), and we present here the structure of the title compound, (I), and show how conformational differences have a large impact on the final supramolecular arrangement in the crystal structure.

A perspective displacement ellipsoid drawing of (I) with the atomic numbering scheme is shown in Fig. 1. Selected bond distances and angles are summarized in Table 1. The Fe^II centre exhibits a nearly ideal high-spin octahedral geometry with two trans N-isothiocyanate anions [maximum SCN^- deviation from linearity 1.082 (2)°], two O atoms of two methanol molecules and the repeating 1,4-bis(4-pyridyl)methylene hydrazine ligands propagating in a perfect linear pattern, giving a one-dimensional chain topology with an Fe···Fe distance of 15.866 (7) Å. The N1—N1ⁱⁱ single bond lies on a crystallographic centre of symmetry exhibiting a perfect antiperiplanar conformation (see Table 1 for symmetry code). As a result, the two pyridinyl rings are parallel, with an interplanar distance of 0.417 (2) Å and a dihedral angle of 12.389 (1)° with the mean plane of the –CH═N—N═ CH– symmetrical spacer.

There are a fair number of isostructural Fe^II and Mn^II coordination polymers in the literature (see, for example, Abu-Youssef et al., 2008) and although the structure presented here is topologically similar to that of [Mn^II(1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene)(NCS)₂(CH₃OH)₂] (Shen, 2003), exhibiting a similar chain architecture with a slightly longer M···M distance of 16.036 (2) Å, the two compounds are not isostructural.

In the present Fe^II case, the chains are interconnected with O—H···S hydrogen bonds between MeOH and SCN^- groups, supporting the molecular arrays with a C(6) chain pattern at the first-level graph-set, as defined by Bernstein et al. (1995) and Grell et al. (1999) (Table 2). The supramolecular architecture can be described as a two-dimensional (8.4 × 8.4 Å) square grid based on hydrogen bonds (Fig. 2), combined with the one-dimensional coordination polymer, giving a three-dimensional net with pcu topology (O'Keeffe et al., 2008), the most common of the six-connected three-dimensional nets. The complete structure can then be described as two interpenetrating networks (Fig. 3). In contrast, [Mn^II(1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene)(NCS)₂(CH₃OH)₂] (Shen, 2003) contains O—H···N hydrogen bonds to the diaza unit, giving a (4,4) grid consolidating a sheet structure.

The striking difference between the Fe and Mn structures may be traced to the different orientations of the MeOH ligand. In the Fe^II compound the O—H bond is nearly parallell to the Fe—N(pyridine) bond (dihedral angle 12.15°) and the methyl group has a weak intramolecular hydrogen bond to the thiocyanate N atom (Table 2), and there is possibly also an interaction between O—H and the pyridine (O···N = 3.072 Å, H···N = 2.792 Å and O—H···N = 101.49°). In the Mn^II compound, the O—H bond is parallel to the Mn—NCS link and no corresponding weak interactions can be detected. Probably the slightly longer metal–ligand bond distances in the Mn^II compound (average Mn—L = 2.23 Å versus average Fe—L = 2.17 Å) mean that the ligands are too far from each other to interact, giving rise to another conformation, and thus the resulting supramolecular arrangement in the crystal structure of the Fe^II compound is determined by the ligand–MeOH interactions.

Further evidence for this argument comes from quantum mechanical DFT calculations. The bridging ligand was replaced by pyridine molecules and two single-point calculations were carried out for each compound to probe the effects of the different MeOH orientations. The results show that, while changing the conformation of MeOH in the Mn^II compound is only slightly unfavourable from an energetic point of view (31 kJ mol^-1), the energy of the Fe^II compound is strongly dependent on the orientation of the MeOH ligand: a 90° rotation around the Fe—O bond to give a similar conformation to the Mn^II compound gives an energy increase of 141 kJ mol^-1. In the latter case, this corresponds to the loss of up to six hydrogen-bond interactions between the methanol and the other ligands (Table 2). Summing over six weak interactions with average bond energies of 16.7 kJ mol^-1 (Jeffrey, 1997) yields 100 kJ mol^-1 which can be considered an upper-limit estimate. Thus, the calculated value is of a reasonable magnitude, although probably exaggerated.

In conclusion, these results suggest that seemingly minor conformational changes may have a large effect on the overall topology of the network.

S2. Experimental

Caution: Perchlorate salts of metal complexes are potentially explosive. Only small quantities of the compound should be prepared and handled with care! Bis-N,N'-pyridinyl methylenehydrazine (1 mmol) was prepared as described previously (El-Rayyes & Katrib, 1983). A methanolic solution of bis-N,N'-pyridinyl methylenehydrazine (0.2 mmol, 0.04 g) was added dropwise to a stirred solution of iron(II) perchlorate hydrate (0.2 mmol, 0.05 g) and potassium thiocyanate (0.3 mmol, 0.03 g) in MeOH/EtOH/MeCN (15 ml, 1:1:1 v/v). The solution was stirred under N₂ for 1 h at room temperature and then filtered. Uniform reddish–orange prisms were collected after 1 week and dried in air. Spectroscopic analysis: IR: (ν, cm^-1, KBr): 496 (m, υ_MN), 687 (m, SCN^-), 810 (m, SCN^-), 1012 (m, υ_MeOH), 1310 (s, υ_OH), 1427 (s, δ_C═N), 2070 (s, SCN^-), 3274 (m, b, OH_stretching).

Density functional theory calculations were performed using the B3LYP function (Lee et al. 1988; Becke, 1993) as implemented in SPARTAN 06 (Wavefunction, 2007) with the 6-31G** basis set.

S3. Refinement

H atoms were constrained to ideal geometry using an appropriate riding model, with C—H = 0.95–0.98 Å and O—H = 0.84 Å, and with U_iso(H) = 1.2U_eq(C_aryl), 1.5U_eq(C_methyl) or 1.5U_eq(O). [Please check added text]

Computing details

Data collection: SMART (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT (Bruker, 2003); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2005) and CrystalMaker (Palmer, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. A perspective drawing of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. For symmetry codes, see Table 1.
	Fig. 2. The hydrogen-bond pattern (dashed lines) in (I) in the bc plane. For full details, see Table 2.
	Fig. 3. The two interpenetrating (light and dark) six-connected three-dimensional pcu nets in (I) formed by hydrogen and coordination bonds

catena-poly[[bis(methanol-κO)bis(thiocyanato-κN)iron(II)]- µ-pyridine-4-carbaldehyde azine-κ²N:N']

Crystal data

[Fe(SCN)2(C12H10N4)(CH4O)2]	F(000) = 460
Mr = 446.33	Dx = 1.449 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3168 reflections
a = 7.6903 (4) Å	θ = 2.5–25.4°
b = 12.8591 (7) Å	µ = 0.96 mm^−1
c = 10.8707 (6) Å	T = 153 K
β = 107.941 (1)°	Prism, orange
V = 1022.73 (10) Å^3	0.09 × 0.08 × 0.04 mm
Z = 2

Data collection

Bruker SMART CCD area-detector diffractometer	2549 independent reflections
Radiation source: fine-focus sealed tube	1950 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.054
ω scans	θmax = 28.3°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	h = −10→10
Tmin = 0.871, Tmax = 0.962	k = −17→17
14356 measured reflections	l = −14→14

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.084	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0407P)^2 + 0.3402P] where P = (Fo^2 + 2Fc^2)/3
2549 reflections	(Δ/σ)max = 0.001
126 parameters	Δρmax = 0.38 e Å^−3
0 restraints	Δρmin = −0.28 e Å^−3

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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq
Fe1	0.5000	0.0000	0.5000	0.01727 (12)
S1	0.78749 (7)	0.26381 (4)	0.30208 (5)	0.02902 (15)
N1B	0.6090 (2)	0.10991 (14)	0.39959 (16)	0.0257 (4)
C2B	0.6815 (3)	0.17423 (16)	0.35895 (19)	0.0212 (4)
C1A	0.3227 (4)	0.2164 (2)	0.5436 (3)	0.0552 (8)
H1A1	0.2826	0.2554	0.6074	0.083*
H1A2	0.2155	0.1929	0.4738	0.083*
H1A3	0.3981	0.2613	0.5077	0.083*
O1A	0.42808 (19)	0.12770 (11)	0.60489 (14)	0.0280 (3)
H1A	0.5228	0.1480	0.6620	0.042*
N1	−0.4234 (2)	−0.01217 (14)	0.05369 (17)	0.0290 (4)
C1	−0.2850 (3)	0.04268 (17)	0.0538 (2)	0.0244 (4)
H1	−0.2954	0.0926	−0.0125	0.029*
C2	−0.1103 (3)	0.02909 (16)	0.15562 (19)	0.0211 (4)
C3	0.0467 (3)	0.07343 (17)	0.1409 (2)	0.0277 (5)
H3	0.0409	0.1125	0.0656	0.033*
C4	0.2112 (3)	0.06022 (17)	0.2369 (2)	0.0265 (5)
H4	0.3177	0.0898	0.2244	0.032*
N5	0.2286 (2)	0.00802 (12)	0.34638 (15)	0.0201 (3)
C6	0.0760 (3)	−0.03521 (16)	0.3593 (2)	0.0226 (4)
H6	0.0855	−0.0734	0.4358	0.027*
C7	−0.0935 (3)	−0.02724 (16)	0.2677 (2)	0.0234 (4)
H7	−0.1971	−0.0598	0.2811	0.028*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.01201 (19)	0.0192 (2)	0.0188 (2)	−0.00087 (15)	0.00216 (14)	0.00115 (16)
S1	0.0286 (3)	0.0248 (3)	0.0358 (3)	−0.0040 (2)	0.0130 (2)	0.0053 (2)
N1B	0.0179 (8)	0.0312 (10)	0.0241 (9)	−0.0020 (7)	0.0009 (7)	0.0054 (7)
C2B	0.0151 (9)	0.0242 (10)	0.0210 (10)	0.0030 (8)	0.0007 (8)	0.0013 (8)
C1A	0.0484 (16)	0.0399 (15)	0.0639 (19)	0.0210 (13)	−0.0023 (14)	−0.0160 (14)
O1A	0.0236 (8)	0.0273 (8)	0.0306 (8)	0.0015 (6)	0.0046 (6)	−0.0065 (6)
N1	0.0160 (8)	0.0396 (11)	0.0247 (9)	−0.0032 (8)	−0.0036 (7)	0.0064 (8)
C1	0.0165 (9)	0.0304 (11)	0.0235 (11)	−0.0011 (8)	0.0019 (8)	0.0041 (9)
C2	0.0150 (9)	0.0252 (10)	0.0201 (10)	0.0000 (7)	0.0010 (8)	−0.0023 (8)
C3	0.0203 (10)	0.0359 (12)	0.0219 (10)	−0.0042 (9)	−0.0006 (8)	0.0062 (9)
C4	0.0167 (10)	0.0350 (12)	0.0256 (11)	−0.0070 (8)	0.0030 (8)	0.0041 (9)
N5	0.0144 (7)	0.0243 (9)	0.0197 (8)	0.0001 (7)	0.0026 (6)	−0.0002 (7)
C6	0.0168 (9)	0.0281 (10)	0.0229 (10)	−0.0003 (8)	0.0058 (8)	0.0026 (8)
C7	0.0147 (9)	0.0307 (11)	0.0247 (10)	−0.0019 (8)	0.0058 (8)	0.0004 (8)

Geometric parameters (Å, º)

Fe1—N1B^i	2.1105 (17)	N1—N1^ii	1.415 (3)
Fe1—N1B	2.1105 (17)	C1—C2	1.464 (3)
Fe1—O1A^i	2.1659 (14)	C1—H1	0.9500
Fe1—N5	2.2381 (15)	C2—C3	1.388 (3)
Fe1—N5^i	2.2381 (15)	C2—C7	1.389 (3)
S1—C2B	1.638 (2)	C3—C4	1.380 (3)
N1B—C2B	1.159 (3)	C3—H3	0.9500
C1A—O1A	1.438 (3)	C4—N5	1.337 (3)
C1A—H1A1	0.9800	C4—H4	0.9500
C1A—H1A2	0.9800	N5—C6	1.344 (2)
C1A—H1A3	0.9800	C6—C7	1.378 (3)
O1A—H1A	0.8400	C6—H6	0.9500
N1—C1	1.276 (3)	C7—H7	0.9500
N1B^i—Fe1—N1B	180.0	N1—C1—H1	119.8
N1B^i—Fe1—O1A^i	88.34 (7)	C2—C1—H1	119.8
N1B—Fe1—O1A^i	91.66 (6)	C3—C2—C7	117.75 (18)
N1B^i—Fe1—N5	89.38 (6)	C3—C2—C1	119.48 (18)
N1B—Fe1—N5	90.62 (6)	C7—C2—C1	122.77 (18)
O1A^i—Fe1—N5	88.44 (6)	C4—C3—C2	119.33 (19)
N1B^i—Fe1—N5^i	90.62 (6)	C4—C3—H3	120.3
N1B—Fe1—N5^i	89.38 (6)	C2—C3—H3	120.3
O1A^i—Fe1—N5^i	91.56 (5)	N5—C4—C3	123.49 (18)
N5—Fe1—N5^i	180.0	N5—C4—H4	118.3
C2B—N1B—Fe1	171.79 (16)	C3—C4—H4	118.3
N1B—C2B—S1	178.93 (18)	C4—N5—C6	116.69 (17)
O1A—C1A—H1A1	109.5	C4—N5—Fe1	120.14 (13)
O1A—C1A—H1A2	109.5	C6—N5—Fe1	123.14 (13)
H1A1—C1A—H1A2	109.5	N5—C6—C7	123.75 (19)
O1A—C1A—H1A3	109.5	N5—C6—H6	118.1
H1A1—C1A—H1A3	109.5	C7—C6—H6	118.1
H1A2—C1A—H1A3	109.5	C6—C7—C2	118.96 (18)
C1A—O1A—H1A	109.5	C6—C7—H7	120.5
C1—N1—N1^ii	111.2 (2)	C2—C7—H7	120.5
N1—C1—C2	120.36 (19)
N1^ii—N1—C1—C2	−179.1 (2)	O1A^i—Fe1—N5—C4	−83.17 (16)
N1—C1—C2—C3	167.2 (2)	N1B^i—Fe1—N5—C6	10.50 (16)
N1—C1—C2—C7	−12.5 (3)	N1B—Fe1—N5—C6	−169.50 (16)
C7—C2—C3—C4	−0.1 (3)	O1A^i—Fe1—N5—C6	98.85 (16)
C1—C2—C3—C4	−179.8 (2)	C4—N5—C6—C7	−0.8 (3)
C2—C3—C4—N5	−1.3 (3)	Fe1—N5—C6—C7	177.23 (15)
C3—C4—N5—C6	1.8 (3)	N5—C6—C7—C2	−0.5 (3)
C3—C4—N5—Fe1	−176.34 (17)	C3—C2—C7—C6	1.0 (3)
N1B^i—Fe1—N5—C4	−171.53 (16)	C1—C2—C7—C6	−179.3 (2)
N1B—Fe1—N5—C4	8.47 (16)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1A—H1A···S1^iii	0.84	2.42	3.2451 (15)	169
C4—H4···N1B	0.95	2.47	3.092 (3)	123
C6—H6···N1B^i	0.95	2.52	3.123 (3)	121
O1A—H1A···N5^i	0.84	2.79	3.072 (3)	102
C1A—H1A2···N5	0.98	2.77	3.368 (3)	120
C1A—H1A3···N1B	0.98	3.00	3.361 (3)	103

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