Synthesis, structure and magnetic properties of a new one dimensional manganese coordination polymer constructed by a new asymmetrical ligand

Accepted Manuscript Synthesis, structure and magnetic properties of a new one dimensional Manganese coordination polymer constructed by a new asymmetrical ligand Pan-Pan Liu, Xue-Qin Song, Li Sheng, Wen-Yan Xu, Yuan-An Liu PII: DOI: Reference:

S0020-1693(15)00288-1 http://dx.doi.org/10.1016/j.ica.2015.05.026 ICA 16556

To appear in:

Inorganica Chimica Acta

Received Date: Revised Date: Accepted Date:

2 April 2015 28 May 2015 29 May 2015

Please cite this article as: P-P. Liu, X-Q. Song, L. Sheng, W-Y. Xu, Y-A. Liu, Synthesis, structure and magnetic properties of a new one dimensional Manganese coordination polymer constructed by a new asymmetrical ligand, Inorganica Chimica Acta (2015), doi: http://dx.doi.org/10.1016/j.ica.2015.05.026

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Synthesis, structure and magnetic properties of a new one dimensional Manganese coordination polymer constructed by a new asymmetrical ligand Pan-Pan Liu, Xue-Qin Song∗ , Li Sheng, Wen-Yan Xu, Yuan-An Liu School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China Abstract A new pentadentate chelate-bridging ligand possessing an inner N2O3 coordination site with one amide,

one

imine,

and

two

phenoxo

2-hydroxy-N-(2-(((3-hydroxynaphthalen-2-yl)methylene)amino)ethyl)benzamide

functions, (H3 L),

was

synthesised. Reaction it with Mn(OAc)2·4H2O yielded a novel zigzag penta-coordinated Mn(III) coordination polymer, [MnL]n, due to the bridging ability of the amide function. The crystal structure of [MnL]n has been determined at 293 K which crystallizes in the monoclinic space group P21/c (No. 14): a = 16.0601(12) Å, b = 8.4048(6) Å, c = 12.7168(10) Å, β = 112.395(9), V = 1606.0(2) Å3, Z = 4. The experimental magnetic susceptibilities indicates the Mn(III) coordination polymer exhibits dominant antiferromagnetic interactions between the manganese centers through the amido bridge, and spin canting is observed with a ferromagnetic transition occurring at 8.5 K. Keywords: Pentadentate ligand; Mn(III) Coordination polymer; Crystal structure; Magnetic properties; Spin canting; 1. Introduction Magnetic molecular materials have experienced great popularity in the past decades due to not only the demand to understand the essential science associated with magnetic interactions between the paramagnetic metal ions mediated by bridging ligands to develop magneto-structural correlations but also their potential applications in information storage at the molecular level and in quantum computation [1-4]. Among them, one-dimensional (1D) magnetic chain systems occupy an important position because many of these species were discovered to be able to exhibit not only a long-range magnetic ordering but also behaviors of single-chain magnets (SCMs) [5]. Noteably, 1D Mn(III) coordination polymers have attracted intense interest due to their SCM Corresponding author. Tel.:+86-931-8843385; fax:+86-931-4938755; E-mail: [email protected] ∗

1

properties induced by the intrinsic magnetic anisotropy of their Mn(III) centers. Because Mn(III) ion possesses a large spin value (S = 2) and a pronounced single ion easy axisanisotropy induced by Jahn–Teller elongation of the coordination octahedron. Besides the spin carrier, employment of appropriate types of bridging ligands which can mediate the magnetic coupling between the local spin carriers has allowed access to a variety of high nuclearity products with interesting structural and magnetic properties. Up to now, neutral manganese complexes have essentially been obtained by association of neutral or mono- or dianionic ligands with halide, pseudohalide, carboxylato, hydroxo, and oxo anions in the metal coordination sphere [6-10]. Among various ligands, asymmetrical trianionic ligands with one amide, one imine, and two phenol functions, and an outer amido oxygen donor atom provide a fascinating prospect in preparing Mn(III) CPs possessing interesting magnetic properties as a result of their inner asymmetrical trianionic tetradentate N2O2 coordination site. To date, some Mn(III) CPs with ligands incorporating salicylamide derivatives have been isolated [11], and the previously rerults showed that substituted groups of this kind of ligands can impact the coordination structures as well as the magnetic properties effectively. This observation prompted us to extend the synthesis of this kind of ligands together with their manganese complexes. In

this

contribution,

we

synthesised

a

new

asymmetrical trianionic

2-hydroxy-N-(2-(((3-hydroxynaphthalen-2-yl)methylene)amino)ethyl)benzamide

(H3 L)

ligand, on

account of the following considerations: (a) H3 L possesses two phenolic hydroxyl group and one NH group that may be completely or partially deprotonated. (b) it is a flexible ligand which can allow the rotation of two aromatic rings around the C−C single bond; (c) To the best of our knowledge, this ligand has not been previously reported not only to chelate Mn(III) but also to any other transition metal ion. In fact, the search of the SciFinder reveals that there is no example of a

coordination

compound

derived

from

H3 L,

2-hydroxy-N-(2-(((3-hydroxynaphthalen-2-yl)methylene)amino)ethyl)benzamide. We herein report the synthesis, crystal structure and magnetic properties of a new 1D amido-bridged Mn(III) coordination polymer [MnL] n which was characterized by single crystal

X-ray diffraction, IR, elemental, thermogravimetric, and powder X-ray diffraction analyses. The magnetic determination indicates the Mn(III) complex behaving as a antiferromagnetic chain with a spin-canting effect at low temperature. 2

2. Experimental 2.1. Materials and instrumentation All chemicals and solvents were obtained from commercial sources and used as received. N-(2-aminoethyl)-2-hydroxybenzamide was prepared according to the literature [12]. Carbon, nitrogen, and hydrogen analyses were performed using an EL elemental analyzer. Melting points were determined on a Kofler apparatus. Powder X-ray diffraction patterns (PXRD) were determined with Rigaku-D/ Max-II X-ray diffractometer with graphite-monochromatized Cu-Kα radiation. Thermogravimetric analyses were carried out on a SDT Q600 thermogravimetric analyzer from room temperature to 800 °C under N2 atmosphere. A platinum pan was used for heating the sample with a heating rate of 10 °C/min. Infrared spectra (4000–400 cm−1) were obtained with KBr discs on a Nicolet FT-170SX instrument in the wavenumber range of 4000–400 cm−1 with an average of 128 scans and 4 cm−1 of spectral resolution. 1H NMR spectra were recorded in CDCl3 solution at room temperature on a Bruker 400 instrument operating at a frequency of 400 MHz and referenced to tetramethylsilane (0.00 ppm) as an internal standard. Chemical shift multiplicities are reported as s = singlet, d = doublet, t = triplet and m = multiplet. The magnetic measurements were carried out on polycrystalline samples using a Quantum Design MPMS SQUID magnetometer. 2.2. Synthesis of the ligands The

synthetic

route

for

2-hydroxy-N-(2-(((3-hydroxynaphthalen-2-yl)methylene)amino)ethyl)benzamide (H3 L) is shown in Scheme 1. General procedure: 5 mmol (0.86 g) 3-hydroxy-2-naphthaldehyde in 20 mL anhydrous ethanol was added dropwise in 10 min to a 10 mL ethanol solution of 5 mmol (0.90 g) N-(2-aminoethyl)-2-hydroxybenzamide. The resulted mixture was stirred and heated at reflux for 4 h. Then the mixture was allowed to stand overnight at room temperature. The crude product was separated by filtration and further recrystallized with ethanol to give a pale yellow solid which was washed with diethyl ether and dried in air. H3 L: 1.12 g, Yield 67.0 %. m. p. 159–161 °C. Analytical data, Calc. for C20H18N2O3: C, 71.84; H, 5.43; N, 8.38; Found: C, 71.97, H, 5.44, N, 8.37; IR (KBr, υ, cm–1): 3384(w), 3136(w), 2939(w), 2871(w), 1622(s), 1581(s), 1544 (s), 1452(m), 1347(m), 1310 (m),1236(m), 835(m), 744(s), 3

607(m), 530(w), 435(w). 1H NMR (CDCl3, 400 MHz): δ: 3.76 (m, 2H, CH2), 3.87 (t, 2H, CH2, J = 4 Hz), 6.71 (m, 3H, ArH), 6.95 (d, 1H, J = 8 Hz, ArH), 7.18 (t, 1H, ArH, J = 4 Hz), 7.35 (m, 1H, ArH), 7.47 (m, 2H, ArH), 7.57 (dd, 4H, ArH, J = 4 Hz), 8.07 (t, 1H, NH, J = 4 Hz), 8. 70 (s, 1H, CH). 2.3. Synthesis of the complexes [MnL]n Mn(OAc)2·4H2O (245 mg, 1 mmol) in 5mL ethanol was added to a 10 mL ethanol solution of H3 L (314 mg, 1 mmol) to give a dark brown solution and a small amount of precipitate. The mixture was stirred for another 4 hours, then methanol (15 mL) was added to make a dark brown solution and filtered. The dark brown filtrate was allowed to slowly evaporate for about three weeks, giving dark-brown block single crystals suitable for X-ray structure determination. The crystals were collected by filtration and washed with methanol several times. (Yield: 220.1 mg (57%) base on Mn. Anal. Calcd for C20H15MnN2O3: C, 62.19; H, 3.91; N, 7.25. Found: C, 62.46; H, 3.88; N, 7.28. IR (KBr, cm–1): 3426(w), 3056(w), 2916(w), 1622 (s), 1600(s), 1571(s), 1496(s), 1466(s), 1450(s), 1338(m), 1251(m), 826(m), 755(m), 592(m), 487(w). 2.4. X-ray single-crystal diffraction analysis Single crystals of dimensions 0.14 × 0.05 × 0.03 mm3 for Mn(III) complex was mounted on a glass rod. The crystal data were collected with a Bruker SMART CCD diffractometer using monochromated Mo Kα radiation (λ = 0.71073 Å) at 293 K. A hemisphere of data was collected in the θ range of 0.98–25.00° using a narrow-frame method with scan widths of 0.30° in ω and an exposure time of 5 s/frame. The numbers of observed and unique reflections are 8065 and 1992 (Rint = 0.0291). The data were integrated using the Siemens SAINT program [13], with the intensities corrected for Lorentz factor, polarization, air absorption, and absorption due to variation in the path length through the detector faceplate. Multiscan absorption corrections were applied. The structure was solved by direct were solved by the Direct Method of SHELXS-97 [14] and refined by full-matrix least-squares techniques using the SHELXL-97 program [15]. Nonhydrogen atoms of the compounds were refined with anisotropic temperature parameters. All H atoms were placed in geometrically idealized positions (C–H = 0.96 Å for methyl groups, C–H = 0.97 Å for CH2 groups, C–H = 0.93 Å for phenyl groups and O–H = 0.82 Å for hydroxyl groups) and constrained to ride on their parent atoms with Uiso(H) = 1.5Ueq(C) for methyl groups, 4

1.2Ueq(C) for aromatic and CH2 groups, and 1.5Ueq(O) for hydroxyl groups. The detailed crystallographic data and structure refinement parameters of compounds are summarized in Table 1. Selected bond distances and angles for these compounds are listed in Table 2 and Table 3. CCDC reference numbers: 1057288. Graphics were drawn with DIAMOND (Version 3.2) [16]. 3. Results and discussion 3.1. Synthesis and physical measurements H3 L characterized by 1H NMR, elemental analysis, FT-IR and melting point data was synthesized in good yield by condensation of N-(2-aminoethyl)-2-hydroxybenzamide with 3-hydroxy-2-naphthaldehyde in 1 : 1 molar ratio as depicted in Scheme 1. The Mn(III) chainlike coordination polymer which was found to be rather insoluble in most solvents other than methanol, DMSO and DMF was obtained by the method of solvent evaporation. The manganese oxidation states were established as +3 by bond-valence sum (BVS) calculations and the elemental analysis was consistent with its chemical formulas. It is well established that Mn(II) can readily be oxidized by atmospheric oxygen to Mn(III) and stabilized by complex formation on reacting with Schiff-base ligands, as can be inferred from numerous reports in this field [17]. In the infrared spectra of H3 L, the characteristic sharp NH stretching of the amide function are present in the IR spectra of H3 L at 3388 cm–1 with the C=O and C=N stretch appears at 1622 cm–1 as the strongest broad band. 1HNMR results, obtained in CDCl3 solutions, confirm this behavior, with a sharp triplet for the amide HN proton at 8.07 ppm resulting from its coupling with the neighboring methylene group. Amide II bands are not easily assigned, due to the presence of C=C and imine C=N bands in the same spectral zone. The relative low frequency of phenolic hydroxyl group at 3136 cm−1 with respect to the free hydroxyl group may be due to intramolecular H-bonding between H of OH and the azomethine nitrogen as well as carbonyl oxygen. The absence of characteristic sharp NH band in the Mn(III) complex IR spectra indicates the deprotonation of the amide group. The appearance of a broad band at 3426 cm–1 as well as the splitting of the C=O and C=N group of the Mn(III) complex compared to the free ligand, clearly indicates Mn(III) ion of the complex is coordinated to the amido and imine nitrogen and the two phenoxo oxygen atoms as well as amide oxygen atom which were further validated by the structural

analysis as follows. 5

The room temperature PXRD patterns of the Mn(III) compound as well as that of simulation of single crystal are unfolded from 5° to 50° as shown in Fig.1. The experimental patterns for the compound correlated well with its simulated one generated from single-crystal X-ray diffraction data, which clearly testify the purity of the Mn(III) complexes. The differences in intensity may be attributed to the variation in preferred orientation of the powder sample during the collection of the experimental PXRD pattern. 3.3 Crystal structure Descriptions A single-crystal X-ray diffraction study revealed that Mn(III) complex of the ligand is a 1D polymeric chain crystallizing in the monoclinic space group P21/c. The asymmetric unit of Mn(III) complex contains one independent Mn(III) ions and one trianion L3‒ with Mn(III) ion unusually five-coordinating to one carbonyl oxygen atom, two hydroxy oxygen atoms and two nitrogen atoms that come from two different fully deprotonated ligands. As shown in Fig. 2, Mn1 exhibits a slightly distorted square pyramidal configuration with O1, O2, N1 and N2 atoms from the same ligand trianion consisting of the equatorial plane and an amide oxygen atom from another ligand trianion occupying the apical site. The equatorial plane is with the least square plane deviation of 0.040 Å, and the Mn(III) atom strays from the equatorial plane 0.235 Å. The Mn‒O bond distances in equatorial plane are 1.847(2) and 1.898(2) Å and Mn‒N distances are 1.965(3) and 1.973 (3) Å. The axial position is occupied by O3 from another ligand anion with the longer bond length of 2.109(3) Å. It is worth noticing that in the the complex the bond lengths is in the increasing order of Mn–O(phenoxo of the amido moiety) < Mn–O(phenoxo of the imine moiety) < Mn–Namido < Mn–Nimine < Mn–Oamido, which is also comparable to those previously reported [11]. The angles of O1–Mn1–N1, and O2–Mn1–N2 are 165.90(12)° and 164.19(19)°, respectively, which are deviated from the theoretical value of 180 °. Therefore, the local coordination geometry around the Mn(III) center can be described as a slightly distorted square pyramid which is very rare for Mn(III) [11 (b)]. The central Mn-N-C-C-N five-membered ring is not planar and has a λ gauche conformation. As a whole, the ligand is distorted with phenyl ring and naphthalene ring deviating from the N2O2 equatorial coordination plane of 6.44ºand 15.37ºrespectively. Noteably, the fully deprotonated ligand anion L3‒ in cis-configuration adopts pentadentate coordination modes with two phenolic oxygen atoms and two nitrogen atoms chelating to one manganese as well as one carbonyl oxygen atom of amide group bridging another manganese. As shown in Fig. 6

3, the amido oxygen atoms are involved in the coordination process as well as the related nitrogen atom, allowing the amido function with a head to tail arrangement to actually bridge adjacent manganese(III) ions, thus leading to a one-dimensional zigzag chain running along the crystallographic c-axis. It is worth noting that the adjacent MnN2O2 equatorial coordination planes in the chain are nearly perpendicular and the corresponding dihedral angle is 87.63º, larger than that of previously reported Mn(III) analogues [11]. The amido oxygen atom coordinates to Mn(III) with the shorter bond length of 2.109(3) Å than those previously reported[11(a)]. The amido-bridged Mn···Mn distance is 5.953(2) Å with the C‒O‒Mn bond angle is 162.9 (2)ºand the torsion of Mn‒amide-Mn of 169.19 º , which is slight longer than that of 1D complexes [Mn(L1)(MeOH)]n (5.828 Å) and shorter than those of 1D complexes [Mn(L2-4)(MeOH)]n (6.035-6.120

Å)

and

[Mn(L5)(H2O)]n

(6.330(1)

1-(2-hydroxybenzamido)-2-((2-hydroxybenzylidene)amino)ethane,

Å)

H3 L2-4b =

(H3 L1

=

derivatives

of

3-aza-4-(3,5-di-tert-butyl-2-hydroxyphenyl)-N-(2-hydroxyphenyl)but-3-enamide), and H3 L5 = 1-(2-hydroxybenzamido)-2-((2-hydroxy-3-methoxybenzylidene)amino)ethane. Upon careful investigation of the structure, it can be seen that two neighboring 1D chains are held together to a puckered two-dimensional(2D) supramolecular network via C–H…O hydrogen bonding with methylene carbon atoms as donor and the phenoxy oxygen atoms of adjacent chains as acceptor (Fig. 4). The C9…O1 distance (3.414(5)Å), as well as C9–H9B…O1 angle (153º), are all within the ranges of those reported C–H…O hydrogen bonds[18]. The nearest interchain Mn···Mn separation is 6.361(4) Å, slight longer than the intrachain Mn···Mn distance (5.953(2) Å). 3.3 Magnetic behavior The temperature dependent magnetization of Mn(III) complex was recorded on a polycrystalline samples under a 1 kOe direct current (dc) field in the temperature range 2–300 K as shown in Fig.5. At 300 K the χMT value is 2.97 cm3·K·mol−1 (4.87 µB), which is very close to the theoretical value of 3.0 cm3· mol−1 · K (4.92 µB) for non-interacting high-spin Mn(III) ions with S = 2 and g=2. As the temperature is lowered, the χMT decreases continuously with decreasing temperature and reaches a minimum of 1.33 cm3·mol−1·K near 13 K. Upon further cooling the temperature, it rises quickly, reaching to a maximum value of 8.11 cm3·mol−1·K at 7 K which is much larger than its room-temperature value. Below 7 K, the χMT drops abruptly again and approaches to a value of 2.95 cm3·mol−1·K at 2 K which is partly due to the saturation effect, as 7

clarified by the M–H measurements. The overall profile of the χMT versus T plot reveals the existence of a magnetic phase transition. The susceptibility data of the compound above 30 K follow the Curie-Weiss law, with C = 3.27 cm3· K· mol–1 and θ = –29.25 K indicating antiferromagnetic interactions predominate between Mn(III) ions at 30 K–300K. The C value is close to the spin-only value of 3.0 cm3 ·K·mol−1 expected from two high-spin d4 (S = 2) species. The nearest-neighbor interaction can be attributed to the through bond Mn3+–Mn3+ coupling across the amide bridges. Field-cooled (FCM) and the zero-field-cooled (ZFCM) magnetizations in the 2-15 K temperature range were also measured, and the plot is reported in Fig. 6. The difference between FCM and ZFCM at low temperature represents the remnant magnetization, which almost disappears on warming to a critical temperature of ca. 8.5 K. The zero-field ac magnetic susceptibility measurement under Hac = 50 Oe and a frequency of 111 Hz shows both in-phase [χ'M (T)] and out-of-phase [χ''M (T)] signals with peaks appearing at ca. 8.5K (Fig. 7), confirming the onset of a long-range ferromagnetic-like ordering at low temperature. Similar magnetic behavior has recently been observed in a related Mn(III) canted antiferromagnetic chain [20]. The ferromagnetic-like ordering is attributed to spin canting, i.e., perfect antiparallel alignment of the spins on neighboring metal ions within the ordered antiferromagnetic state is not achieved so that residual spins are generated. Usually, the canting effect is caused by antisymmetric interactions linked to the symmetry of the exchange pathways joining the magnetic centers, and also to single ion anisotropy. In the Mn(III) coordination polymer, the maganese atoms which has large single-ion magnetic anisotropy are bridged purely through O=C–N units. Probably, the canted antiferromagnetism observed in the compound can be related to its structure in which no inversion center exists between neighboring Mn(III) ions and the relative orientation of metal centers alternate systematically within the chain. The magnetizations measured below 9 K show hysteresis loops. Fig. 8 shows the isothermal magnetization vs. field plot at 2 K. The magnetization at 80 kOe (1.39 Nβ) is far below the saturation value of 4.0 Nβ expected for an S = 2 system, consistent with a canted antiferromagnetism. Extrapolating the linear part of the magnetization curve at high fields to H = 0 gives a magnetization value of 0.0312 Nβ. If we assume this to be the uncompensated magnetization, the canting angle is estimated to be 4.5˚. [21] The coercive field (Hc) and the 8

remnant magnetization (Mr) at 2 K are 26.5 Oe and 0.0032 Nβ, respectively (Fig. 8, inset). 3.7. Thermogravimetric analysis(TGA) To characterize the Mn(III) compound in terms of thermal stability, thermal gravimetric analysis (TGA) were carried out in the temperature range of 25 ~ 1000 ℃ under nitrogen atmosphere as shown in Fig. 9. Thermogravimetric analysis indicates that [MnL]n does not undergo significant mass loss below 400 ℃, the temperature at which it decomposes. This confirms that, as indicated by the crystal structure and infrared spectroscopy, there is no solvent present in the structure. The result from TGA analysis revealed that ligand L3− has greater binding capacity for Mn (III) which is in perfect agreement with the proposed structural results. Supplementary material Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Center, CCDC nos. 1057288. Copies of this information may be obtained free of charge from the director, CCDC, 12 Union Road, Cambridge CB2 IEZ, UK (e-mail: [email protected] or www: http://www.ccdc.cam.ac.uk). Conclusions A new 1D Mn(III) coordination polymer of a new trianionic asymmetrical ligand with amide and imine functions was prepared owing to the bridging ability of the oxygen atom of the amido function. The adjacent 1D chains of the Mn(III) complex are connected by C–H…O hydrogen bonding to form a 2D puckered supramolecular architecture. The experimental magnetic susceptibilities indicates the

Mn(III) coordination polymer exhibits the existence of a weak antiferromangetic coupling along the chain through the amido bridge with a spin canting that leads to a long-range antiferromagnetic order at Tc ≈ 13 K and a canting leading to a weak ferromagnetic long-range order at Tc ≈ 8.5 K. This work demonstrates that the introduction of substituents of this kind of trianionic asymmetrical ligand could result in varied structures, which is expected to provide more novel model compounds to investigate fascinating magnetic behaviors.

Acknowledgements This work was supported by the National Natural Science Foundation of China (Grants 21161011). References 9

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Table 1 Crystal data and structure refinement parameters for [MnL] n Empirical formula

C 20 H15 Mn N 2 O 3

Crystal system, space group

Monoclinic, P21/c a = 16.0601(12) Ǻ, α = 90 (6) ˚

Unit cell dimensions

b = 8.4048(6) Ǻ, β = 112.395(9) ˚ c = 12.7168(10) Ǻ, γ = 90 ˚

Volume

1606.0(2) Ǻ3

Z, Calculated density

4, 1.598 kg/m3

Absorption coefficient

0.846 mm-1

F(000)

792

Crystal size

0.14 × 0.05 × 0.03 mm

Theta range for data collect

3.47 to 25.00 ˚

Limiting indices

-18 ≤ h ≤ 19, -10 ≤ k ≤ 10, -15 ≤l ≤ 14

Reflections collected / unique

8065 / 2758 [R(int) = 0.0662]

Completeness to theta = 25.01

97.7 %

Data / restraints / parameters

2758/ 0 / 235

Goodness-of-fit on F

1.076

Final R indices [I>2sigma(I)]

R1 = 0.0494, wR2 = 0.0963

R indices (all data)

R1 = 0.0769, wR2 = 0.11

Largest diff. peak and hole

0.397 and -0.418 e.Å-3

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Table 2 Selected bond lengths (Å ) and angles for [MnL]n Mn1−O1

1.846(2)

Mn1−O2

1.901(2)

Mn1−N2

1.940(3)

92.48(11)

O2−Mn1−N2

164.19(12)

O1− Mn1−N1 165.90(12)

O1−Mn1−O3

104.65(10)

O2−Mn1−O3

O1−Mn1−O2

92.36(10)

O1−Mn1−N2

O2−Mn1−N1

88.14(11)

N2−Mn1−N1

83.54(12)

N2− Mn1−O3

96.86(12)

N1−Mn1−O3

89.28(11)

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Mn1−N1

1.972(3)

Mn1−O3

2.109(3)

96.45(11)

Scheme. 1 The synthetic route of the ligand H3 L. Fig. 1 Powder X-ray diffraction patterns of Mn(III) complex. Fig. 2 (a) View of the coordination environment of Mn1 centre with thermal ellipsoids at 30% probability with a labelling scheme (All H atoms have been omitted for clarity). (b) The coordination polyhedron of Mn1. Fig. 3 1D Mn(III) coordination chain view along c-axis. Fig. 4 2D puckered supramolecular architecture constructed by C–H···O hydrogen bond. Fig. 5 Thermal dependence of χMT and χM–1 for Mn(III) complex collected in an applied dc field of 0.1 T. Fig. 6 ZFCM and FCM curves for Mn(III) complex. Fig. 7 Temperature dependence of ac magnetic susceptibility for Mn(III) complex. Fig. 8 Field dependent magnetization and hysteresis loop (inset) for Mn(III) complex at 2 K. Fig. 9 TGA curves of the Mn(III) complex under N2 atmosphere.

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A novel zigzag penta-coordinated Mn(III) coordination polymer [MnL]n has been synthesised and structurally characterized. The experimental magnetic susceptibilities indicates the Mn(III) coordination polymer exhibits the existence of a weak antiferromangetic coupling along the chain through the amido bridge with a spin canting that leads to a long-range antiferromagnetic order at Tc ≈ 13 K and a canting leading to a weak ferromagnetic long-range order at Tc ≈ 7 K.

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A novel coordination polymer of a pentadentate ligand has been synthesized. Crystal structure analysis revealed [MnL]n was a zigzag penta-coordinated chain. Magnetic properties has been studied.

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