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The Field-Dependent Magnetization ofd5–d7 Metal β-Diketonate Complexes andTheir Macromolecular PolymersMohammed A. Al-Anbera, Haneen Daouda & Mahdi Lataifehb

a Department of Chemical Science, Faculty of Science, MútahUniversity, Al-Karak, Jordanb Department of Physics, Faculty of Science, Mútah University, Al-Karak, JordanAccepted author version posted online: 16 Apr 2014.Publishedonline: 25 Jun 2014.

To cite this article: Mohammed A. Al-Anber, Haneen Daoud & Mahdi Lataifeh (2014) The Field-Dependent Magnetization of d5–d7 Metal β-Diketonate Complexes and Their MacromolecularPolymers, Journal of Macromolecular Science, Part B: Physics, 53:7, 1258-1269, DOI:10.1080/00222348.2014.901872

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Journal of Macromolecular Science R©, Part B: Physics, 53:1258–1269, 2014Copyright © Taylor & Francis Group, LLCISSN: 0022-2348 print / 1525-609X onlineDOI: 10.1080/00222348.2014.901872

The Field-Dependent Magnetization of d5–d7

Metal β−Diketonate Complexes and TheirMacromolecular Polymers

MOHAMMED A. AL-ANBER,1 HANEEN DAOUD,1

AND MAHDI LATAIFEH2

1Department of Chemical Science, Faculty of Science, Mutah University,Al-Karak, Jordan2Department of Physics, Faculty of Science, Mutah University, Al-Karak, Jordan

A vibrating sample magnetometer (VSM) has been used to study the field-dependent mag-netization, M(H), of the d5−d7 metal acetates [M(OAc)2.nH2O], metal β−diketonatecomplexes [M(tba)2(H2O)2] and the macromolecular polymers [M(tba)2(4,4-bipy)]n

(where, M = Mn(II), Fe(II), and Co(II), OAc = O2CCH3, tba = deprotonated 3-benzoyl-1.1.1-trifluoroacetone, and 4,4-bipy = 4,4′-bipyridine). The magnetic field strength (H)was applied in the range of 0−104 Oe at ambient temperature (ca. 23◦C). The experi-mental results showed that the d5−d7 metal acetate, complexes and polymers exhibit lowparamagnetic properties excepting [Fe(tba)2(4,4-bipy)]n polymer, which had negativemagnetization M(emu/g) showing diamagnetic properties in the range 0−104 Oe. Themagnetization was almost equal to zero without an applied magnetic field (H(Oe)) foreach d5−d7 metal acetate, complex, and polymer. The linear M(H) curve had a magneticsaturation for iron and manganese acetate species at the magnetic field strengths of 3.1 ×103 and 4.7 × 103 Oe, respectively. The external magnetic field reached 9.0 × 103

Oe without any saturation magnetization for the cobalt compounds. The coordinationeffect of 3-benzoyl-1.1.1-trifluoroacetone (H-tba) and 4,4′-bipyridine (4,4′-bipy) lig-ands on the field-dependent magnetization M(H) and paramagnetic behavior of d5−d7

metal atoms is discussed. The field-dependent magnetization M(H) curves of metalβ−diketonate complexes and the polymers including d5−d7 metal acetates showed aweak field octahedral geometry.

Keywords magnetic properties, metal β−diketonate polymers, metal acetates,paramagnetic transition metals

Introduction

Multidimensional coordination polymers have recently gained great attention because theyhold promise for constructing poly-functional magneto-active materials.[1–5] In particu-lar, metal β−diketonate and metal nitrogen-based ligand chemistry[6,7] represent a fruitfulsource for synthesizing multi-dimensional polymeric frameworks, in which β−diketonesact as linker(s) and the nitrogen-based ligand acts as spacer between the metal atoms.[8]

In the literature, there have been described some examples of coordination polymeric

Received 16 May 2013; accepted 4 February 2014.Address correspondence to Mohammed A. Al-Anber, Department of Chemical Science, Mutah

University, 61710 Al-Karak, P.O. Box 7, Jordan. E-mail: masachem@mutah.edu.jo(Dr. M. Al-Anber)

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Magnetic Behavior of d5−d7 Metal β−Diketonates 1259

framework constructed from organic ligands with mixed functionalities.[9–11] Many ex-amples of β−diketonate complexes including divalent first row transition metals havebeen reported as starting materials in the synthesis of supramolecular aggregates,[12–16]

cubane-type metallic clusters,[17–20] and heterometallic complexes.[21–23] Self-linkage ofparamagnetic metal atoms through mixed oxygen- and nitrogen-based ligands produce co-ordination polymers with the general formula [M(ox)(4,4′-bipy)]n (where, ox = oxalate,bipy = 4,4′-bipyridine, and M = Fe(II), Co(II), or Ni(II)).[24,25] The preparation of het-erometallic β−diketonates and their potential application as single-source precursors forthe synthesis of mixed-metal oxide materials have been reported.[26,27] The magnetic prop-erties of β−diketonates metal complexes M(hfac)2 (M = Mn, Fe, Co, and Ni; hfac =hexaluoroacetylacetonate) have also been studied.[28]

Our current interest has focused on the synthesis of mononuclear complexes andpolymeric materials including β−diketonate ligands and divalent metal atoms.[29–33,34]

To keep these materials in touch with potential applications, the physical and chemicalproperties have recently been studied. For example, the field-dependent magnetizationM(H) of d8−d10 metal β−diketonate complexes, such as [M(tba)2.nH2O] metal complexesand [M(tba)2(4,4′−bipy)]n coordination polymers (where, M = Ni(II), Cu(II) and Zn(II);tba = deprotenated 3-benzoyl-1.1.1-triflouroacetone; 4,4′−bipy = 4,4′−bipyridine) wereinvestigated using a vibrating sample magnetometer (VSM) at ambient temperature (ca.23◦C).[35] The ligands of 3-benzoyl-1.1.1-triflouroacetone (H-tba) and 4,4′−bipyridine(4,4′−bipy) were able to reduce the paramagnetic properties of the Ni(II) and Cu(II)metal atoms. Metal acetate species exhibited the strongest paramagnetic properties,and then followed by metal complexes. The polymerization of the paramagnetic metalcomplexes was accomplished by using 4,4′−bipy producing diamagnetic polymers of[Ni(tba)2(4,4′−bipy)]n and [Cu(tba)2(4,4′−bipy)]n. On the other hand, the diamagnetic be-havior of the [Zn(tba)2(H2O)2] metal complex was not highly affected by the presence of thebidentate H-tba ligand. The diamagnetic behavior of the [Zn(tba)2(H2O)2] metal complexwas increased by bridging the Zn(II) atoms with the 4,4′−bipy to produce the coordinationpolymer of [Zn(tba)2(4,4′-bipy)]n. In general, the produced polymers of [Ni(tba)2(4,4-bipy)]n, [Cu(tba)2(4,4-bipy)]n, and [Zn(tba)2(4,4-bipy)]n had nearly the same diamagneticbehavior. The magnetization curves M(H) of the metal acetates species, complexes, andpolymers were nearly linear with the increase in the applied magnetic field, as is usuallytrue for paramagnetic and diamagnetic samples.[35,36] In the presence of the external mag-netic field, the magnetization of the metal acetate species, complexes, and polymers wereaffected in different ways. Therefore, we can conclude that these supramolecular complexesand their acetate species may separate from one another under the action of an externalmagnetic field of nonzero magnetization up to 104 Oe. However, the coordination polymerscould not be separated from one another because of the convergence of their diamagneticvalues.[35]

Metal acetates of the general formula [M(OAc)2.4H2O] (where, M = Mn(II), Fe(II)or Co(II); OAc = O2CCH3) are considered to be starting materials for a wide range ofmetal complexes that exhibit interesting magnetic properties. Recently, the magnetic andstructural properties of iron acetate species have been reported.[37] The study confirmed thatthe complex is a high-spin complex with a magnetic moment 5.4 μβ . The field-dependentmagnetization results revealed a slight sigmodial curve progression, which is typical formetamagnetization. Moreover, cobalt acetate has been reported as being a ferromagneticcompound at a low temperature of 1.8 K.[38] Mn12 acetate (Mn12O12(CH3COO)16(H2O)4)contains four Mn4+ (S = 3/2, where S is the spin angular momentum) ions in a central tetra-hedron surrounded by eight Mn3+ (S = 2) ions. The Mn ions are coupled by superexchange

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1260 M. A. Al-Anber et al.

through oxygen bridges. These experiments, which are previously reported, indicated alarge magneto-crystalline anisotropy and super-paramagnetic behavior.[37] It is these metalacetates that we used for this research.

Herein, we reinvestigated the magnetic properties of the hydrated acetate to completeour investigations. Furthermore, we were interested in studying the field-dependent magne-tization for the metal acetates [M(OAc)2.nH2O], β−diketonate complexes [M(tba)2.nH2O],and coordination polymers [M(tba)2(4,4-bipy)]n (where, M = Mn(II), Fe(II), and Co(II);OAc = O2CCH3; tba = deprotenated 3-benzoyl-1.1.1-triflouroacetone (H-tba); 4,4′−bipy = 4,4′−bipyridine) by using a VSM.

Experimental

Chemicals and Preparation Procedures

All chemicals were of analytical reagent grade and used directly without further purifi-cation. Metal-organics [M(tba)2(H2O)2] (M = Mn, Fe, and Co) were synthesized bythe treatment of [M(OAc)2.4H2O] (M = Mn, Fe, and Co; OAc = O2CCH3) with 3-benzoyl-1.1.1-triflouroacetone (H-tba) in a 1:2 molar ratio in boiling ethanol.[34,39] Themacromolecular coordination polymers of [M(tba)2(4,4-bipy)]n (M = Mn(II), Fe(II), andCo(II); tba = deprotenated 3-benzoyl-1.1.1-triflouroacetone (H-tba); 4,4-bipy = 4,4′-bipyridine) were prepared by the reaction of [M(tba)2(H2O)2] (M = Mn, Fe, and Co)with one equivalent of 4,4-bipy; Herein, the aqua ligands in [M(tba)2(H2O)2] were re-placed by 4,4′−bipy ligand. All materials were characterized by Fourier transform infraredspectroscopy, ultraviolet visible spectrometry, single crystal X-ray diffraction, powderX-ray diffraction, and thermogravimetric analysis-differential scanning colorimetry.

Magnetic Measurements

The vibrating sample magnetometer (VSM model 9600), supplied by LDJ Eelectronics(USA), was used to study the magnetic properties of our materials. The system was cali-brated before taking measurements by using a pure nickel sphere from the National Bureauof Standards (USA). The accuracy of the magnetic induction measurements was 1% witha sensitivity of 0.01 emu. Initial magnetization measurements (curves) were recorded atroom temperature (23◦C) in the range limit of our magnet, between 0 and 104 Oe. Thepowder samples were inserted in a cylindrical sample holder which was nonmagnetic. Theheight of the powder sample in the cylinder was more than seven times its radius, in orderto reduce the demagnetization effect.

Result and Discussion

Magnetism of d5−d7 Metal Acetate

Figure 1 shows the experimental VSM measurements of the field dependent magnetizationM(H) for [Mn(OAc)2.4H2O], [Fe(OAc)2.4H2O], and [Co(OAc)2.4H2O] (OAc = O2CCH3).The M(H) curves were recorded between 0 and 104 Oe. These d5−d7 metal acetate speciesexhibited positive values of magnetization M(H), as shown in Fig. 1, indicating their para-magnetic behaviors. However, the slope of the magnetization M(H) curves for these d5−d7

metal acetates had high value relative to d8−d9 metal acetates.[35] This behavior shows that

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Magnetic Behavior of d5−d7 Metal β−Diketonates 1261

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M(e

mu/

g)

H(Oe)× 10²

□ [Co(OAc)2.4H2O]◊ [Mn(OAc)2.4H2O]Δ [Fe(OAc)2.4H2O]

Figure 1. Magnetization (M) vs. applied magnetic field (H) at ambient temperature for [M(OAc)2.4H2O] (where M = Mn, Fe, and Co).

the manganese, iron, or cobalt acetates had high paramagnetic properties compared to thed8−d9 metal acetates.[35] These d5−d7 metal acetates, however, still had low magnetizationcompared to the ferromagnetism materials. The low magnetization can be explained by thechemical structure of the d5−d7 metal acetates. The coordinated water (H2O) acts like amagnetic solvent in each metal acetate. As a result, the magnetic moments of the d5−d7

metal acetates cannot be coupled directly with their neighbors to give a strong magnetiza-tion, i.e., the coupling occurs through the intervening water molecules.[40] In addition, itmay involve a direct metal−metal bond or a super-exchange mechanism via the bridgingacetate ligands.[41,42]

The magnetization was almost equal to zero without an applied magnetic field for eachd5−d7 metal ion (see Fig. 1). The reason is the random orientation of magnetic moments ofthe unpaired electrons due to thermal agitation of the parent molecules or ions. Thus, themagnetic moments of these metal ions can cancel one another. In the presence of an externalmagnetic field, the magnetic moments of the unpaired electrons (domain) turn toward thefield direction. Therefore, we observed a net magnetization in these metal acetates.

In our field range, we did not observe any saturation magnetization for cobalt acetateup to 104 Oe. The magnetization curves of iron and manganese acetate show a saturationmagnetization at 3.1 × 103 Oe with 0.18 emu g−1 and 4.7 × 103 Oe with 0.30 emu g−1,respectively.[43] This behavior can be explained; it is suggested to be due to the differentcoordination modes of the acetate ion found in the crystal structures of iron acetate,[44]

manganese acetate[45] and cobalt acetate,[46] wherein, the crystal structure of cobalt acetate

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consists of discrete centro-symmetric trans-Co(C2H3O2)(H2O)4 complexes, linked by athree-dimensional (3D) network of hydrogen bonds. Each complex participates in 14 hy-drogen bonds, 12 intermolecular, and 2 intramolecular.[46] Each cobalt atom is surroundedoctahedrally by four water molecules and two oxygen atoms which belong to two differ-ent acetate groups. Because the cobalt atom occupies a center of symmetry at (0,0,0), anoctahedron is formed from three symmetry-related pairs of oxygen atoms.[47] The crys-tal structure of iron acetate has been identified as a two-dimensional (2D)-coordinationpolymer consisting of iron atoms and acetate moieties with all the iron atoms hexacoor-dinated with different coordination modes for the acetate moieties. Additional hydrogenbond contacts lead to the formation of the coordination polymer. The crystal structureof manganese acetate is based on trinuclear manganese clusters. It has a 2D structurewith a 4-connected sql topology (The uninodal topology sql is a square grid sheet. Thestructures of sql topology represent 4-connected metal atoms as vertexes and 2-connectedligands as edges) and is further extended to a 3D-supramolecular framework by hydrogenbonds, where the trinuclear Mn3 cluster units can be nodes and acetates are connectors.Thus, manganese acetate is not isostructural with cobalt and iron acetate.[45] Generally,the d5−d7 metal atoms adopt octahedral coordination geometry, coordinated by four wa-ter molecules and two oxygen atoms which belong to two acetate groups. The d5−d7

metal atoms locate at a special site with a symmetry center corresponding to “octahedral”symmetry.[47,48]

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M(e

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g)

H(Oe) × 10²

[Mn(tba)2(H2O)2]◊ [Co(tba)2(H2O)2]Δ [Fe(tba)2(H2O)2]

Figure 2. Magnetization (M) vs. applied magnetic field (H) at ambient temperature for [Mn(tba)2

(H2O)2], [Fe(tba)2(H2O)2], and [Co(tba)2(H2O)2].

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Magnetic Behavior of d5−d7 Metal β−Diketonates 1263

Based on the VSM experimental results (see Fig. 1) and crystal field theory, theparamagnetic behavior of these d5−d7 metal acetates was the result of being high-spinsix coordination compounds with a weak-field octahedral symmetry. The weak satura-tion of magnetization (M) noted for the two metal atoms (Fe(II) and Mn(II)) confirmsthat the compounds had low paramagnetic properties with the paramagnetic order being[Mn(OAc)2.4H2O] > [Fe(OAc)2.4H2O] in the range of 0–3.1 × 103 Oe. On the other hand,the [Co(OAc)2.4H2O] was still paramagnetic in the range of 0–104 Oe without any magneticsaturation appearing.

Magnetism of the d5−d7 Metal Complexes

The coordination of Mn(II), Fe(II), and Co(II) with the 3-benzoyl-1.1.1-triflouroacetone (H-tba) ligand produces neutral [Mn(tba)2(H2O)2], [Fe(tba)2(H2O)2], and [Co(tba)2(H2O)2](tba = deprotenated form of H-tba) β−diketonate complexes (see Scheme 1).[34] In general,the new complexes have different magnetic characteristics than that of their d5−d7 metalacetate species. Thus, it is important to study the effect of the H-tba ligand on the magneticproperties of these d5−d7 metal complexes, because they could possess potentially newmagnetic properties, and then construct poly-functional magneto-active materials.[1–5] Inaddition, it was desired to know the effect of the tba ligand on the magnetic properties ofthe d5−d7 divalent metals and compare it with our recent study involving d8−d10 divalentmetals.[35]

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H(Oe) × 10²

[Mn(OAc)2.4H2O]◊ [Mn(tba)2(4,4'-bipy)]nΔ [Mn(tba)2(H2O)2]

Figure 3. Magnetization (M) vs. applied magnetic field (H) at ambient temperature for [Mn(OAc)2.4H2O], [Mn(tba)2(H2O)2], and [Mn(tba)2(4,4′-bipy)]n.

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The experimental VSM results (Fig. 2) show that in the absence of an applied magneticfield H(Oe), the field-dependent magnetization M(H) was nearly zero. The reason is therandom orientation of the magnetic moments of the unpaired electrons, which can cancelone another. In the presence of an external magnetic field, the magnetic moments of theunpaired electrons in the d−orbitals of the complexes turn toward the field direction.Therefore, we observed a net magnetization in these complexes similar to what was seenin the case of the d5−d7 metal acetate curves.

Figure 2 shows the experimental VSM of the dependent magnetization fields for thesecomplexes. The magnetization curves M(H) for [Mn(tba)2(H2O)2], [Fe(tba)2(H2O)2], or[Co(tba)2(H2O)2] exhibited positive values and it does not reach saturation up to 104

Oe indicating all had a paramagnetic behavior. The slopes of the M(H) magnetizationcurve for the [Mn(tba)2(H2O)2], Fe(tba)2(H2O)2], and [Co(tba)2(H2O)2] complexes hadlower values compared to their paramagnetic M(H) curves of d5−d7 metal acetate species,especially as the presence of the applied magnetic field increased. The maximum mag-netization value for Mn(II), Fe(II), and Co(II) β−diketonate complexes were 0.26, 0.09,and 0.04 emu g−1, respectively, while, the maximum magnetization values for Mn(II),Fe(II), and Co(II) acetates were 0.30, 0.18, and 0.48 emu g−1, respectively. This indi-cates that the tba-ligand can decrease the paramagnetic properties of the metal atom (seeFigs. 3–5). The experimental VSM results show that the slopes of the M(H) magnetizationcurves decreased in the trend of [Mn(tba)2(H2O)2] > Fe(tba)2(H2O)2] > [Co(tba)2(H2O)2]

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H(Oe)× 10²

[Fe(OAc)2.4H2O]◊ [Fe(tba)2(4,4'-bipy)]nΔ [Fe(tba)2(H2O)2]

Figure 4. Magnetization (M) vs. applied magnetic field (H) at ambient temperature for[Fe(OAc)2.4H2O], [Fe(tba)2(H2O)2], and [Fe(tba)2(4,4′-bipy)]n.

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Magnetic Behavior of d5−d7 Metal β−Diketonates 1265

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M(e

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g)

H(Oe)× 10²

[Co(OAc)2.4H2O]◊ [Co(tba)2(4,4'-bipy)]nΔ [Co(tba)2(H2O)2]

Figure 5. Magnetization (M) vs. applied magnetic field (H) at ambient temperature for[Co(OAc)2.4H2O], [Co(tba)2(H2O)2], and [Co(tba)2(4,4′-bipy)]n.

-0.04

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M(e

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g)

H(Oe)× 10²

[Mn(tba)2(4,4'-bipy)]n◊ [Fe(tba)2(4,4'-bipy)]nΔ [Co(tba)2(4,4'-bipy)]n

Figure 6. Magnetization (M) vs. applied magnetic field (H) at room temperature for [Fe(tba)2(4,4′-bipy)]n, [Mn(tba)2(4,4′-bipy)]n, and [Co(tba)2(4,4′-bipy)]n.

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1266 M. A. Al-Anber et al.

(see Fig. 2). This trend of a decline in the slope can be explained by the electron donationby tba-ligand to the d5−d7 metal centre. This reduces the number of unpaired electrons inthe d-orbital’s of eg

1 × eg1 (eg = dx2−dy2 and dz2) energy levels of Mn2+, Fe2+ and Co2+

and then decreases the paramagnetic properties of the d5−d7 metal atom. From anotherpoint of view, the unpaired electrons in the d-orbital (t2g × eg; where t2g = dxy, dxz, dyz)of the metal complex could be shielded by the two chelated tba-ligands. Thus, there was avery weak interaction between the magnetic moments of the d5−d7 metal atoms themselvesand the external applied magnetic field. In particular, the tba-ligand has the ability to shieldthree unpaired electrons (in case of cobalt atom) and more than four and five (in caseof manganese and iron atoms, respectively). Therefore, this weak interaction leads to thelow magnetization properties for the d5−d7 metal complex. Based on these suggestions,the slope of magnetization curve were predicted to be in the trend of [Mn(tba)2(H2O)2]> [Fe(tba)2(H2O)2] > [Co(tba)2(H2O)2], which is consistent with the experimental VSMresults [19].

Magnetism of the d5−d7 Metal Macromolecular Polymers

The d5−d7 metal complexes [M(tba)2(H2O)2] (M = Mn, Fe, and Co) were polymerized byaddition of 4,4′-bipy, producing the macromolecular polymers of [Mn(tba)2(4,4-bipy)]n,[Fe(tba)2(4,4-bipy)]n, and [Co(tba)2(4,4-bipy)]n (where, M = Ni(II), Cu(II) and Zn(II);tba = deprotonated 3-benzoyl-1.1.1-triflouroacetone; 4,4-bipy = 4,4′-bipyridine).[34] Thefield-dependent magnetization M(H) of these d5−d7 metal macromolecular polymers[M(tba)2(4,4-bipy)]n are shown in Figs. 3–6. The results were similar to the magnetizationcurves of their metal complexes [M(tba)2(H2O)2] (M = Mn, Fe, and Co) (see Figs. 3–5).The similarities lay in several aspects of: (i) the curves linearity and lack of a saturation mag-netization within the range of 0–104 Oe, and (ii) zero magnetization M(H) in the absence ofan external applied magnetic field H(Oe). Figure 6 shows positive magnetization values forboth the [Co(tba)2(4,4-bipy)]n and [Mn(tba)2(4,4-bipy)]n macromolecular polymers, indi-cating the presence of paramagnetic behaviors for these polymers. Generally, the slope ofthe M(H) magnetization curve of the [Co(tba)2(4,4-bipy)]n polymer and [Co(tba)2(H2O)2]complex were superimposed on each other. The slope of the magnetization curves of the[Mn(tba)2(4,4-bipy)]n and [Fe(tba)2(4,4-bipy)]n polymers had lower values compared totheir corresponding complexes. On the other hand, the polymerization of the paramagnetic[Fe(tba)2(H2O)2] complex generated a diamagnetic [Fe(tba)2(4,4-bipy)]n polymer, with anegative slope. The behavior of the [Fe(tba)2(4,4-bipy)]n polymer, with a negative slope,could be due to one or more of: (i) further electron donation to the d5−d7 metal centre;(ii) encapsulation of the metal ions by the tba and 4,4′-bipyridin ligands could enhancethe demagnetization process based on Lenses Law [41]; and (iii) the free delocalizationof electrons in the network of the macromolecular polymers through the 4,4-bipy ligandresulting in the free movement of the electron cloud (or electron density) in the wholepolymer network.

Conclusions

In summary, the ligands of both 3-benzoyl-1.1.1-triflouroacetone (H-tba) and 4,4′-bipyridine (4,4-bipy) were able to reduce the paramagnetic properties of the Mn(II), Fe(II)and Cu(II) metal ions. The Mn2+, Fe2+, and Co2+ can be coordinated by H-tba in weak fieldoctahedral complexes (i.e., high-spin d5−d7 metal complexes and polymers). The strongestparamagnetic properties occurred for the d5−d7 metal acetates, followed by the d5−d7 metal

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complexes. The bridging ligand of the 4,4′-bipy can reduce the paramagnetic property ofthe [Mn(tba)2(H2O)2] and [Co(tba)2(H2O)2] complexes. The polymerization outcome ofthe paramagnetic [Fe(tba)2(H2O)2] complex generated a diamagnetic [Fe(tba)2(4,4-bipy)]n

polymer.The magnetization curves M(H) for the d5−d7 metal acetates had nearly the same

paramagnetic properties up to 2.9 × 103 Oe, and then they behaved differently. Iron andmanganese acetate were magnetically saturated at fields higher than 2.9 × 103 Oe and4.6 × 103 Oe, achieving 0.18 and 0.31 emu g−1, respectively. However, this saturation wasnot seen in their polymers and complexes. The magnetization curve for [Co(OAc)2.4H2O]did not reach saturation, indicating paramagnetic behavior along the measurement scale(from 0 to 104 Oe).

The magnetization curves M(H) for the d5−d7 metal complexes and polymers werenearly linear with the increase in the applied magnetic field, as is usually true for para-magnetic and diamagnetic samples.[36] In the presence of the external applied magneticfield, the magnetization of the d5−d7 metal acetates, complexes and polymers were af-fected in different ways. Therefore, we can conclude that these polymers, complexes andtheir acetate specie for a given metal could be separated from one another by applyingan external magnetic field below 104 Oe. However, the macromolecular 1D-polymer of[Co(tba)2(4,4′-bipy)2] could not be separated from the [Co(tba)2(H2O)2] complex becauseof the convergence of their paramagnetic values.

Acknowledgments

The authors would like to thank Mu′tah University (Jordan) for the support needed forthis research. We would like to extend my sincere thanks to Prof. P. Geil for his fruitfulobservations and suggestions.

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