Synthesis, crystal structure and magnetic property of an iron(III) coordination polymer with N-acyl-salicylhydrazide ligand

Article abstract of DOI:10.1016/j.inoche.2011.03.066

A one-dimensional coordination polymer of iron(III) with N-dehydroabietoyl-salicylhydrazide (H₃L) ligand, [Fe(HL)Cl(CH ₃OH)]_n·nCH₃OH (1), was synthesized and characterized by single-crystal X-ray diffraction, el

Full text of DOI:10.1016/j.inoche.2011.03.066

Inorganic Chemistry Communications 14 (2011) 1036–1038
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Synthesis, crystal structure and magnetic property of an iron(III) coordination
polymer with N-acyl-salicylhydrazide ligand
Suni Qin a,b, Chao Zu a, Zilu Chen a, Wanyun Huang a,b, Jiangke Qin a, Fupei Liang a,
⁎
a
Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources (Ministry of Education of China), School of Chemistry and Chemical Engineering,
Guangxi Normal University, Guilin 541004, PR China
b
State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A one-dimensional coordination polymer of iron(III) with N-dehydroabietoyl-salicylhydrazide (H3L) ligand, [Fe
(HL)Cl(CH3OH)]n·nCH3OH (1), was synthesized and characterized by single-crystal X-ray diffraction, elemental
analysis, and infrared spectra analysis. The N-dehydroabietoyl-salicylhydrazide ligand in the compound is doubly
deprotonated and acts as a tetradentate ligand to Fe(III) ions in tridentate-monodentate/back-to-back fashion,
giving rise to a linear chain structure. The 1D chain is further extended to 2D supramolecular network by
intermolecular hydrogen bonds. The magnetic study of the compound indicates an antiferromagnetic coupling
interaction between Fe(III) ions.
Received 25 February 2011
Accepted 31 March 2011
Available online 8 April 2011
Keywords:
Coordination polymer
Iron(III)
N-acyl-salicylhydrazide
Crystal structure
Magnetic property
© 2011 Elsevier B.V. All rights reserved.
Metallamacrocycles, an important class of multinuclear clusters,
have attracted great research interest for decades because of their
intriguing molecular architectures, unique magnetic and catalytic
properties, potential use as host systems for various guest molecules'
recognition chemistry and as secondary building blocks for the
construction of metal-organic frameworks [1–3]. In this context,
metallacrowns with [M–N–N]n cyclic repeating units, known as
metalladiazamacrocycles, are an important class of metallamacro-
cycles and have been intensively studied since the first report of a
hexanuclear manganese metalladiazamacrocycle in 1998 [4–6]. This
class of metallamacrocycle is typically prepared by using trianionic
pentadentate N-acyl-salicylhydrazide or its analogues as ligand and
trivalent octahedral metal ion such as Mn(III), Fe(III), Co(III) and Ga
(III) as centre ion [7–19]. It has been found that the nature of N-acyl
groups of the N-acyl-salicylhydrazide ligand can influence the size
and nuclearity of the metallamacrocycle formed. The introduction of a
Cβ substituent at the N-acyl site of the ligand does not affect the
nuclearity of the metallamacrocycle, except for the case that the Cβ
position with an extremely bulky residue [20], while the introduction
of the Cα substituent results in the expansion of the macrocyclic ring
to give metallamacrocycle with higher nuclearity. Metalladiazama-
crocycles with different nuclearities ranging from 6 to 20 have been
obtained by tuning the rigidity and steric volume of the Cα substituted
moiety [21–27].
For further understanding the coordination chemistry of the
N-acyl-salicylhydrazide and the influence of the N-acyl residue of
the ligand on the structures of the complexes formed, we designed
and synthesized a new N-acyl-salicylhydrazide ligand, N-dehydroa-
bietoyl-salicylhydrazide (H3L) (Scheme 1) [28]. This compound
possesses three chiral carbon atoms. More interesting, it bears a
rigid and extremely bulky N-acyl residue. We hoped that higher
nuclear metalladiazamacrocycle would be obtained with such a
compound as ligand. However, reaction of H3L ligand with FeCl3·6H2O
[29] afforded unexpectedly a one-demensional iron(III) chain [Fe(HL)
Cl(CH3OH)]n·nCH3OH (1), but not a metalladiazamacrocycle. To the
best of our knowledge, this is the first coordination polymer of
trivalent octahedral metal ion bridged only by N-acyl-salicylhydrazide
ligand. The crystal structure and properties of 1 are discussed in detail
as below.
The single-crystal X-ray structural analysis [30] reveals that 1
crystallizes in the triclinic space group P1, showing a 1D chain
structure with building monomer of [Fe(HL)Cl(CH3OH)] which
comprises one iron ion, one N-dehydroabietoyl-salicylhydrazide
ligand, one chloride anion and one methanol molecule. As depicted
in Fig. 1, the iron(III) ion is six-coordinated in a distorted octahedral
geometry with one carbonyl oxygen atom (O2), one phenolic oxygen
atom (O1) from a HL2− ligand, one chloride anion (Cl1) and one
oxygen atom (O3) of methanol molecule in the equatorial plane. The
axial sites are occupied by one hydrazide nitrogen atom (N1) from the
same HL2− ligand as above and one carbonyl oxygen atom (O4B) from
the other HL2− ligand. The Fe–N and Fe–Cl distances are 2.084 and
2.319 Å, respectively, while the Fe–O distances are in the range 1.874
to 2.134 Å. The N-dehydroabietoyl-salicylhydrazide in 1 is doubly
⁎
Corresponding author. Tel.: +86 773 5856302; fax: +86 773 5832294.
E-mail address: fliangoffice@yahoo.com (F. Liang).
1387-7003/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2011.03.066

S. Qin et al. / Inorganic Chemistry Communications 14 (2011) 1036–1038
1037
Scheme 1. Ligand H3L and basic biding sites in 1.
deprotonated. It acts as a dianion tetradentate ligand with its phenolic
oxygen atom, one hydrazide nitrogen atom (salicylyl side), and one
carbonyl oxygen atom (dehydroabietoyl side) binding to one Fe(III)
ion in the meridianal mode, and the another carbonyl oxygen atom
(salicylyl side) bridging to adjacent Fe(III) ion in a back-to-back mode.
The hydrazide nitrogen atom on the dehydroabietoyl side is
protonated, and is free from coordination. This tridentate–mono-
dentate binding mode of the ligand leads to the formation of the 1D
chain structure of 1, as shown in Fig. 2. The neighboring Fe∙∙∙Fe
distance in the chain is 6.264 Å, which is quite larger than those in the
Fe(III) metalladiazamacrocycles reported (ca. 4.9 Å) [21,22,31]. The
Fe∙∙∙Fe∙∙∙Fe angle is of 180°, indicating that the 1D chain is perfectly
linear. Two end groups around the N–N bond of the HL2− ligand are
arranged regularly with all the salicylyl groups on one side and the
dehydroabietoyl groups on the other side of the chain.
N-acyl-salicylhydrazide ligands in all complexes of trivalent octahe-
dral metal ions reported so far are triply deprotonated and act as
pentadentate ligands to metal ions. The ligand adopts tridentate-
bidentate/back-to-back fashion to bridge the adjacent metal ions,
producing metalladiazamacrocycle with [M–N–N] repeating units.
Utilization of ferric chloride as reaction material does not affect the
formation of Fe(III) metalladiazamacrocycle [32,33]. In our case, the
N-dehydroabietoyl-salicylhydrazide acts as a dianion tetradentate
ligand, which is very different from other N-acyl-salicylhydrazides
reported. The ligand takes tridentate-monodentate/back-to-back bind-
ing mode, leading to the formation of 1D chain coordination polymer,
but not metalladiazamacrocycle. Such a result can be ascribed to the
steric effect of the N-acyl residue of the N-dehydroabietoyl-salicylhy-
drazide ligand. The rigid and extremely bulky dehydroabietoyl group
will cause very large steric repulsion between N-acyl residues if the
ligand takes tridentate-bidentate/back-to-back fashion to form a
metalladiazamacrocycle with shorter M∙∙∙M distance and M∙∙∙M∙∙∙M
interatomic angle smaller than 180°. Thus, it turns to take tridentate-
monodentate fashion, giving rise to a chain structure with longer M∙∙∙M
distance and M∙∙∙M∙∙∙M angle of 180°, to release the steric repulsion.
Indeed, it can be seen from the references that the M∙∙∙M distance and the
M∙∙∙M∙∙∙M interatomic angle increase with the increase of the steric
crowding of the N-acyl residues and the expansion of the macrocyclic
ring of metalladiazamacrocycle. For example, the average Fe∙∙∙Fe
distances and Fe∙∙∙Fe∙∙∙Fe interatomic angles are 4.881, 4.889, 4.946 Å
and 117.6, 130.9, 140.4° for hexanuclear, octanuclear, and decanuclear
iron metalladiazamacrocycles, respectively [21,22,31]. Based on this fact,
Fig. 2. 1D chain of 1 linked by the Ocarbonyl atom of HL2− ligand. All H atoms and guest
CH3OH molecules are omitted for clarity. Symmetry codes: A) x−1, y, z; B) x+1, y, z.
it can be rationally concluded that if the steric crowding of the N-acyl
residues great enough, the macrocyclic ring will be expanded infinitely,
and the M∙∙∙M distance will increase further and M∙∙∙M∙∙∙M angle tend to
180°, which will lead to the broken of the metallmacrocycle and the
formation of the coordination chain.
Intermolecular hydrogen bonds are observed in 1. The guest CH3OH
molecule forms hydrogen bonds with the coordinated chloride anion
and the coordinated CH3OH molecule from adjacent 1D chains (O5-H5∙∙∙
Cl1i, O3-H10C∙∙∙ O5ii, i=x+1, y−1, z+1, ii=x−1, y, z−1), which
extend 1 into a 2D hydrogen-bonded network as shown in Fig. 3. The
O···Cl distance and the O–H···Cl angle are 3.126 Å and 162.0°, while
the O···O distance and the O–H···O angle are 2.618 Å and 125.0°,
respectively.
The temperature dependence of the molar susceptibility χM and
the product χMT for 1, measured at a magnetic field of 1000 Oe in the
temperature range of 2–300 K, is shown in Fig. 4. In the high
temperature region, the χMT value at 300 K is 3.42 cm3 K mol–1
,
smaller than the expected value of 4.38 cm3 K mol–1 for one spin-only
Fe(III) ion with S=5/2, which is due to the antiferromagnetic
interaction between Fe(III) ions in the compound. When the
temperature decreases, the χMT value decreases gradually from
3.42 cm3 K mol–1 at 300 K to 2.23 cm3 K mol–1 at 60 K, and then
abruptly to 0.14 cm3 K mol−1 at 2 K. The χMT versus T curve is in
agreement with an antiferromagnetic behavior of iron complexes. The
best linear fit according to the Curie–Weiss law in the temperature
ranging from 70 to 300 K yields C=4.01 cm3 K mol–1 and a Weiss
constant θ=−52.95 K (see the inset of Fig. 4). The negative Weiss
constant further suggests the presence of an antiferromagnetic
coupling interaction among spin carriers.
Fig. 1. The Fe(III) coordination environment with 50% thermal ellipsoids in the
mononuclear unit of 1. All H atoms and guest CH3OH molecule are omitted for clarity.
Symmetry codes: A) x−1, y, z; B) x+1, y, z.
Fig. 3. 2D network of 1 formed by intermolecular hydrogen bonds indicated by broken
lines.

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S. Qin et al. / Inorganic Chemistry Communications 14 (2011) 1036–1038
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In conclusion, an unexpectedly coordination polymer of trivalent
octahedral metal ion with N-acyl-salicylhydrazide ligand, [Fe(HL)Cl
(CH3OH)]n·nCH3OH, was prepared by the reaction of N-dehydroa-
bietoyl-salicylhydrazide with FeCl3·6H2O. The compound presents a
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Acknowledgements
The authors thank the financial support by National Natural Science
Foundation of China (No. 20971029) and Guangxi Natural Science
Foundation (No. 2010GXNSFD013018 and 2010GXNSFF013001).
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Appendix A. Supplementary material
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metallamacrocycle having a multidentate bridging ligand in two different binding
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CCDC 806940 contains the supplementary crystallographic data for
this paper. These data canbeobtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in the
online version, at doi:10.1016/j.inoche.2011.03.066.
[27] W. Luo, X.T. Wang, X.G. Meng, G.Z. Cheng, Z.P. Ji, Metal coordination architectures of
N-acyl-salicylhydrazides: the effect of metal ions and steric repulsion of ligands to
their structures of polynuclear metal complexes, Polyhedron 28 (2009) 300–306.
[28] Synthesis of H3L: A sample of dehydroabieticacyl chloride (4.8 g, 15 mmol) was
added dropwise to 100 mL of chloroform at 0 °C containing 1 mL (7 mmol) of
triethylamine. After stirring for 30 min, the solution was slowly warmed to room
temperature. Then, salicylhydrazide (3.4 g, 22 mmol) was added and the resulting
solution was further stirred for 24 h. A yellow precipitate of H3L was isolated by
filtration and recrystallized from ethanol and H2O solutions (71%, Yield). Anal. Calc.
for C27H34N2O3 (%): C, 74.62; H, 7.89; N, 6.45. Found: C, 74.91; H, 8.04; N, 6.27. IR data
(KBrpellets, cm–1): 3278(m), 2957(s), 2930(s), 1637(s), 1599(s), 1520(s), 1495(m),
1384(m), 1360(m),1250(m), 1210(m), 826(m), 754(m).
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