Crystal engineering and magnetostructural properties of newly

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Crystal engineering and magnetostructural properties of newly designed azide/acetate-bridged Mn12 coordination polymers Mo Ashafaq, Mohd Khalid, Mukul Raizada, Anzar Ali, Mohd Faizan, M. Shahid, Musheer Ahmad, and Ray J. Butcher Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.9b00058 • Publication Date (Web): 25 Feb 2019 Downloaded from http://pubs.acs.org on February 26, 2019

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Crystal Growth & Design

Crystal engineering and magnetostructural properties of newly designed azide/acetate-bridged Mn12 coordination polymers Mo Ashafaqa, Mohd Khalida*, Mukul Raizadaa, Anzar Alib, Mohd Faizanc, M. Shahida, Musheer Ahmadd, Ray J. Butchere aDepartment bDepartment

of Chemistry, Aligarh Muslim University, Aligarh-202002, India

of Physical Sciences, Indian Institute of Science Education and Research (IISER) Mohali-140306, Punjab, India cDepartment

dDepartment

of Physics, Aligarh Muslim University, Aligarh-202002, India

of Applied Chemistry, ZHCET, Aligarh Muslim University, Aligarh-202002, India

eDepartment

of Chemistry, Howard University, Washington, DC 20059 USA.

*Corresponding author, E-mail: [email protected]

Abstract: Crystal engineering of the coordination polymers where polynuclear clusters are building blocks constitutes an emerging class of chemistry. The fine tuning of the structural motifs leads to interesting and varying magnetic properties. Owing to such properties, two rare μ6-oxo centered

mixed-valent,

azide

or

acetate-bridged

coordination

polymers

viz,

[{MnII2MnIII10Na2(μ6-O)2(N3)10(NO3)(H2O)4(thme)8}·3(Et3NH)]n (1) and [{MnII3MnIII9Na7(μ2O)2(μ6-O)2(O)5(CH3O)(CH3CO2)11(thmp)8}·4(O)]n (2) with retention of Mn12 metallic core in both polymers are obtained using tripodal polyalcohol 1,1,1‒tris (hydroxymethyl)ethane (H3thme) and 1,1,1‒tris (hydroxymethyl)propane (H3thmp) ligands, respectively. X-ray analysis shows that 1 is a 1D coordination polymer where Mn12 units are propagating by bridging azide function. 1 shows the underlying net of 2,2,3C6 topological type. 2 forms a cyclic ring as a result of repeating Mn12 zig-zag chains bridging by sodium and H2O. The topology

of

2

resulting

31-nodal

underlying

3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,6,6,6,6,6,6,6,6,7,7-c net with point symbol of the net is {3.4.5}2{3.47.52}2{32.410.52.6}{32.410.53}4{32.43.5.203.21}{32.43.5}6{32.44}2{32.46.52.63.7.8}{

ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

32.46.52}{34.44.52}{34.46.54.64.72.8}2{412.52.6}2{42.6}2{43}{45.5}3 {45.6}{46.63.8}. In 1, the magnetic study ascertains the presence of antiferromagnetic interaction and exhibited single molecule magnet (SMM) like behaviour with energy barrier of 75.5 K. However, 2 exhibited the strong antiferromagnetic interaction in dc studies. The superparamagnetic-like slow relaxation of its magnetization was not observed for 2 in out-of-phase ac magnetic susceptibility due to the absence of large enough energy barrier. Magnetization versus applied dc field exhibited hysteresis loop at 2 K with coercivity of 1069.10 Oe and remanent magnetization of 0.374 μB in 1 while 2 has no coercivity in hysteresis loop even at the lowest temperature (2.0 K) and no saturation was observed up to 7.0 T field supporting antiferromagnetic interactions present in the polymer.

Keywords: Mn/Na heterometallic, Coordination polymers, Topology, Magnetic properties and Single-molecule magnet (SMM).

Introduction Apart from a mononuclear molecule and polynuclear metal cluster, the polynuclear coordination polymers of paramagnetic metal ions bridged by small ligands, for example, azido, OH−, OR− and carboxylate (RCO2−), are achieving special attention, now-a-days, owing to their structure diversity and with regards to SMMs (single-molecule magnets) [1‒5] behaviours. Especially, azide and carboxylate ions show versatile bridging modes, and play extremely important role in distributing magnetic exchange interaction amongst the paramagnetic ions. Accordingly, large number of azide and acetate bridged transition complexes of paramagnetic nature are gaining focus to explore the magnetic exchange interaction in these species [6‒13]. The combination of Ising type magnetic anisotropy with a high and negative D (zero-field part parameter) value and substantial spin ground-state are the


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significant properties of SMMs [14‒16]. Large S values can come about because of ferrimagnetic or ferromagnetic spin orientations and furthermore from certain Mx topologies with spin frustration (competing antiferromagnetic interactions) that counteract absolutely antiparallel spin arrangements [17, 18]. Intrachain interactions between the spin carriers can be either ferro- (FM) or antiferromagnetic (AF) [19‒22]. In general, the typical binding modes noticed for the azide as bridging ligand are EO (end-on) and EE (end-to end). The end to end bridging mode is fundamentally AF (antiferromagnetic) coupler with a couple of special cases where this mode was viewed also for the ferromagnetic exchange interactions [23, 24]. Moreover, coordination geometries i.e., the dihedral angle between the M‒N‒N‒N and N‒N‒N‒Mˊ mean planes and M‒Nazido‒M angles also play important role for the magnetic coupling between the metal centers [25‒27]. These have received much attention due to their interesting magnetic properties, for example, slow relaxation, QTM (quantum tunneling of magnetisation) and large hysteresis loop [28] and have been mentioned as candidate for potential uses in the field of quantum computation, high-density information storage, and molecular spintronics [28, 29, 30]. In this way these bridging ligands can be additionally used to cooperate with ligands to develop attractive metal coordination polymers. Furthermore, mixed-metal aggregates, including close association of Na+ ions with transition-metal clusters, have additionally drawn extensive intrigue currently on account of their entrancing structures and magnetic properties [31‒34]. For the designing of SMMs, there are lots of reports in which manganese is preferred metal of choice, because Jahn–Teller distorted MnIII ions play significant role to originate high molecular anisotropy in the system [35, 36‒38]. The MnIII ions itself has a high spin number and an undeniable single ion anisotropy, prompting exciting molecule based magnets, particularly for MnIII-containing SMMs [39‒42]. However, Mn(III)based polynuclear cluster polymers bridged by the azide and acetate ions have been rarely reported [43‒45]. In mixed-valence manganese chemistry, the magnetic interactions in MnIII–



O–MnIV and MnIV–O–MnIV bridges are generally strongly antiferromagnetic as compared to those in MnIII–O–MnIII and MnII–O–MnIII bridges which have either weakly antiferromagnetic or weakly ferromagnetic [17, 18, 46, 47]. Consequently, bridging ligands incorporation approach is very helpful that can generally show ferromagnetic coupling and which can therefore increase the possibilities of a larger ground-state spin (S) value [48]. This approach will be of the great interest to study influence of the small bridging ions in the magnetic interactions and structure in cluster systems. Since numerous kinds of organic ligands have been utilized as a part of manganese chemistry, viz., alcoholates or polyalcoholates [49, 50]. To develop new synthetic routes for designing of metal complexes, the selection of the ligands always play important role [51‒53]. One of the best synthetic ways to deal with new polynuclear clusters includes the utilization of chelates containing alcohol groups in light of the fact that alkoxides are excellent bridging groups and therefore support the designing of polynuclear products [54‒57]. The flexible tripodal polyalcohol ligands like H3thme and H3thmp (Scheme 1) [58] are wonderful units and very effective for the designing of polynuclear complexes with large covalent or non‒covalent supramolecular networks. The reactivity of tripodal polyalcohols has been utilized broadly in synthesis of oxido‒bridged polynuclear complexes of paramagnetic 3d transition metal ions [59‒61]. In this way, the combinatory utilization of appropriate ligands and auxiliary chelating/bridging ligands, for example, azide and/or acetate potentially has given access to extremely fascinating polynuclear complexes with amazing architecture, mostly have large ground states S value [62] and large metal nuclearities [63]. Till date, there are so many reports in which azido and acetate anions are used as a versatile bridging ligands and lead to the designing of various manganese based clusters [64, 65], but to the best of our knowledge, very rare cases are seen where an azide and acetate have been utilized to connect discrete mixed-metal (Mn/Na) clusters in a stepwise way to develop coordination polymers [66, 67].


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Subsequently, it is very significant to investigate the chemistry of polynuclear clusters based on polyalcohol ligands with the addition of an azide and acetate to connect these discrete large clusters. These specifics excited us to further explore reaction system of manganese chemistry as a potential route for new high spin cluster polymers of polyalcohol ligands in which metal ions are bridged by azide/acetate chelators. Herein, we report two novel heterometallic (Mn/Na) with unique μ6-oxo-centered mixed-valent (MnII/III) azide/acetate-bridged coordination polymers [{MnII2MnIII10Na2(μ6-O)2(N3)10(NO3)(H2O)4(thme)8}·3(Et3NH)]n (1) and [{MnII3MnIII9Na7(μ2-O)2(μ6-O)2(O)5(CH3O)(CH3CO2)11(thmp)8}·4(O)]n (2). 1 represents new class of mixed-metal coordination polymer containing single end to end azide bridge and shows SMM like behavior with an energy barrier of 75.5 K. This is the rare example of SMM based on Mn12Na2 repeating unit furthermore in regards to mixed valent Mn-polyol SMM with straight chain structure. In contrast, 2 has μ3-η1:η2 acetate bridging and Mn12Na7 as repeating unit but exhibits completely different polymeric topologies. The interest in these new polymers, apart from the above considerations, is found in the fact that mixed-metal (Mn/Na) coordination polymers bridged by azide/acetate ligands are still rare and further exploration to link large discrete mixed-metal clusters by small bridging ions to develop coordination polymers is still desirable.

Experimental Materials All chemicals (that were commercially available) utilized as received without further purification. H3thme, H3thmp, sodium acetate and sodium azide were purchased from SigmaAldrich Chemical Co. India. Triethylamine (S. d. fine) and manganese salts (Sigma‒Aldrich) were purchased and utilized as taken. The reagent grade solvents were used in the reactions without further purification.



Caution! The metal complexes containing azide are potentially explosive. Though, no problem was experienced in the present experiment, but materials should be prepared in small amount and treated with precaution at all the times.

Physical measurements Melting points of crystals were determined by open capillary method and are uncorrected. All manipulations were performed under aerobic conditions. IR Spectra were recorded on a Perkin‒Elmer spectrum GX automatic recording Spectrometer as KBr disc in the range of 4000‒400 cm−1. The elemental C, H and N analyses were obtained from micro‒analytical Laboratory of Central Drug Research Institute (CDRI), Lucknow, India. PXRD patterns have been recorded by “Miniflexll X-ray diffractometer” with Cu-Kα radiation. DC magnetic susceptibility studies were done using Cryogenic Limited 7T SQUID Magnetometer operating in the temperature range 1.8–300 K. AC magnetic susceptibility measurements were achieved using a Quantum Design (QD) PPMS (Physical Property Measurement System). Samples were embedded in eicosane to prevent torquing. Pascal’s constants were employed for the diamagnetic corrections.

Synthesis Synthesis of [{MnII2MnIII10Na2(μ6-O)2(N3)10(NO3)(H2O)4(thme)8}·3(Et3NH)]n (1) H3thme (0.240 g, 2.0 mmol) and NaN3 (0.195 g, 3.0 mmol) were stirred in methanol (10 mL) and a colourless solution was obtained at room temperature. To this solution, methanolic solution (10 ml) of Mn(NO3)2·4H2O (0.6275 g, 2.5 mmol) was added slowly (dropwise) over a period of 3 min when light brown colour started appearing. The colour of the solution immediately turned to dark brown after addition of triethylamine (NEt3) (0.21 mL, 1.5 mmol). The resulting solution was stirred further for 1 h. After that, the resultant solution was stirred


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at 60 °C for 8 h and then cooled down. Solution was filtered, layered with diethyl ether, and left undisturbed for slow evaporation. After two weeks, dark brown crystals of X-ray quality appeared which were isolated by filtration and dried under vacuum after washing with cold acetonitrile. Yield: 48 %; m. p. > 300 °C; Elemental (C, H and N) analysis, Calcd. (%) for C58H128Mn12Na2N34O33: C, 27.47; H, 5.05; N, 18.79; Found: C, 27.45; H, 5.04; N, 18.77. FTIR data (KBr pellets, cm−1): 3417, 2855, 2071, 1631, 1557, 1410, 1125, 1035, 815, 611, 513. Synthesis of [{MnII3MnIII9Na7(μ2-O)2(μ6-O)2(O)5(CH3O)(CH3CO2)11(thmp)8}·4(O)]n (2) H3thmp (0.268 g, 2.0 mmol) and sodium acetate (0.246 g, 3.0 mmol) were stirred in methanol (10 mL) and a colourless solution was obtained at room temperature. To this solution, methanolic solution (10 ml) of Mn(NO3)2·4H2O (0.6275 g, 2.5 mmol) was added slowly for 3 min and a light brown colour appeared immediate after the addition of triethylamine (NEt3) (0.21 mL, 1.5 mmol). The stirring was further continued for 1h. After that, solution was heated at 60 °C with stirring for 8 h and cooled down to room temperature. Solution was filtered, layered with diethyl ether and left undisturbed for slow evaporation. Well-shaped brown crystals suitable for X-ray crystallography were obtained after two weeks which were isolated by filtration and washed with cold acetonitrile. Yield: 45 %; m. p. > 300 °C; Elemental (C and H) analysis, Calcd. (%) for C71H119Mn12Na7O60: C, 30.98; H, 4.32. Found: C, 30.79; H, 4.28. FTIR data (KBr pellets, cm−1): 3411, 2862, 2065, 1612, 1412, 1117, 1048, 615, 485.

X‒ray Crystallographic data collection and structure solution Crystal data for 1 and 2 were collected using BRUKER SMART APEX CCD diffractometer with graphite monochromator utilizing Mo‒kα (λ = 0.71073 Å) radiation and transferred to a goniostat where they were cooled to 296 K for data collection. The crystal structures were solved by direct method and refined by full-matrix least squares refinement technique on F2 using SHELXL-2016/17 [68]. The coordinates of non-hydrogen atoms were refined



anisotropically using SHELXL-2016. SAINT Software [69] was used for data integration and reduction. The space groups P21/n (1) and P−1 (2) were determined using XPREP [70]. Absorption corrections by integration were applied for the crystals based on measured indexed crystal faces. An empirical absorption correction based on symmetry counterpart was applied using the SADABS program [71]. SIR‒97 [72] structure solution program package was used for solving the structures by direct solution method. The selection, integration and averaging procedure of the measured reflex intensities, data reduction, the determination of the unit cell by a least‒squares fit of the 2Θ values, LP correction, and the space group determination were performed using the X‒Area software package provided with the diffractometer. The non‒H atoms were treated anisotropically in all the cases, while the hydrogen atoms involved to carbon were placed in calculated, ideal positions and refined as riding on their respective C atoms. The H atoms attached to oxygen atoms were experimentally positioned from the Fourier difference maps and refined with isotropic displacement parameters set to 1.2 × Ueq of the attached atoms. There are some hydrogen atoms of the lattice water molecules that could not be located. Crystal data and selected structural parameters of both the complexes are shown in Table 1. The molecular structure, space filling and packing pictures were produced with MERCURY 3.8. Crystallographic data of the complexes have been deposited at the Cambridge Crystallographic Data Center [CCDC No. 1820166 (1) and 1813726 (2)].

Results and discussion Synthetic strategy To date several synthetic methodologies for manganese chemistry have been employed, most of which exploited reaction of carboxylate as starting materials, either in the form of MnII carboxylate salts (viz. Mn(O2CR)2) or MnIII or MnIII/IV complexes, having bridging/chelating ligands [73‒81]. The present work demonstrates the exploitation of the reactivity of MnII salt


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(manganese nitrate tetrahydrate i.e., non-carboxylate) as starting material, with tripodal polyol ligands and azides or acetates as linker/bridging ligands that can facilitate the designing of high nuclearity coordination polymers. The reaction between manganese nitrate and H3thme with NaN3

at

60

°C

in

methanol

gives

[{MnII2MnIII10Na2(μ6-

O)2(N3)10(NO3)(H2O)4(thme)8}·3(Et3NH)]n (1) in 48 % isolated yield. The same methodology was

applied

for

the

synthesis

of

[{MnII3MnIII9Na7(μ2-O)2(μ6-

O)2(O)5(CH3O)(CH3CO2)11(thmp)8}·4(O)]n (2), the only difference being the replacement of sodium acetate and H3thmp ligand with sodium azide and H3thme ligands. The latter was intended to reaction having acetate bridged product different from 1, but the main, manganese metallic core remained same in both the polymers. Thus, 2 is different from 1 in containing a different bridging and peripheral ligands. Our primary attempt was to develop coordination polymers, by the bridging of manganese clusters with azides and/or acetates as bridging ligands. The observed colour change from light brown to dark brown may be due to the aerial oxidation of MnII as starting manganese source to MnIII upon long time stirring. At the high temperature, the diffusion of reactants increases due to reduce viscosity and also because of diverse solubilizing properties of the solvents i.e., as temperature of the solution mixture increases the dielectric constant of the solvent falls very fast [82]. Such kind of reaction conditions can produce the desired products in comparison to ambient reaction conditions (e.g. no product or crystal was yielded at room temperature with the present reaction conditions). Hence, the reaction temperature, rate of cooling of the reaction and also relative solubility are major factors for the isolation of the desired product.

Crystal structure investigations of [{MnII2MnIII10Na2(N3)10(thme)8(μ6O)2(NO3)(H2O)4}·3(Et3NH)]n (1)



The fully labelled central metallic core of the asymmetric unit of coordination polymer 1 is shown in Fig. 1. The crystallographic data collection and structural refinement is listed in Table 1. The unit cell packing of 1 shows that four asymmetric units are parallely arranged in the cell (Fig. S1). Selected bond length and angles are given in Table S1. X‒ray diffraction analyses show that 1 has monoclinic system with space group P21/n. The single-crystal structure analysis confirmed that 1 is a 1D coordination polymer designed by bridging two Mn12 moieties through an end-to-end azide ligand as shown in the Fig. 2. The asymmetric unit of 1 contains twelve manganese ions and two sodium ions, peripheral ligation is given by the ten azide and eight thme3− ligands in which two hexameric Mn6 units are bridged by the azide and nitrate ions and forms dumbbell like structure. The space filled diagram noticeably indicate that there is very small apace inside which is created by the bridged azide and the nitrate ions and the Mn6 metallic cores are so much buried, hard to see clearly (Fig. S2). The repeating unit of polymer is a [Mn12Na2(μ3-O)6(μ2-O)18(NO3)(N3)] core which is comprised of two Mn6 octahedral cores bridged by the nitrate and the azide ions. The azide ligand bridges two asymmetric units through Mn atoms in end-to-end fashion with an average angle of 144.40° for Mn-N-N (azide) within the asymmetric unit and 126.50° Mn-N-N (azide) for coordinated cluster chain. Mn1 atom of the symmetric unit linked through one end nitrogen (N(13)) of the pendant azide to Mn5 atom of the newly created empty axial position of the neighboring unit. The terminal azide ligands bind to the metal in end on style and have average angle of 122.73° Mn-N-N (azide). All manganese ions are six‒coordinated and have distorted octahedral geometry. The geometry of each MnIII ion is not perfectly octahedral, rather is noticeably distorted, in which two bonds are longer than the four other bonds (Fig. S3) (the axial elongations of the two Mn–N/O(R) or Mn–O(R) Mn bonds in trans arrangement). The Jahn– Teller (JT) distortion is present in MnIII ions (axial elongations) although these are not coparallel shown in Fig. S4. The average bond distances of Mn–O in polymer of manganese ions


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(MnII and MnIII) are 2.150 and 2.044 Å, respectively which comes in the usual range MnII–O and MnIII–O bonds, validating the +2 and +3 oxidation state of manganese ions [83]. Two oxygen atoms O31 and O33 of the nitrate ion work as a linking agent and link the two Mn6 clusters units within the asymmetric unit of the polymer through Na+ ions (Na1 and Na2). The charge observations demonstrate a “2MnII, 10MnIII” depiction for 1 and the bond valence sum (BVS) [84, 85] calculations (Table 2) further substantiated the oxidation state of manganese ions and ascertained Mn3 and Mn11 as the MnII ions, and rest as MnIII ions. The metallic core III

can be depicted as a mixed‒valence MnII2Mn10 (Table 2) and have two octahedral core of the manganese ions, (Fig. 1) with two unusual µ6‒O2− bridges (O13 and O30) confirmed by bond‒valence sum (BVS) calculations (Table S2) [84, 85], that bind to all six manganese ions together (Fig. S5). The azides having bridging modes η1:µ1 and η1:η1:µ2 (Scheme 2) and thme3− ligands provided the peripheral ligation to the central metallic core. All the eight fully deprotonated thme3− ligands bind in two different ways, the six ligands (thme3−) have the similar binding mode as η3:η2:η2:µ4‒bridging mode in which four manganese ions are connected to one ligand, the remaining two thme3− ligands adopt η2:η2:η2:µ3‒bridging mode (Scheme 3). The coordination numbers around of the each sodium ions (Na1 and Na2) are achieved by four terminal water (O15, O16, O17 and O18) molecules. Each sodium ion is six coordinated and have distorted octahedral geometry in which the coordination is provided by the two terminal water molecules, three alkoxide arms of the three different ligands and one oxygen atom of the nitrate ion. This coordination polymer has the shortest intercluster Mn···Mn distance of 3.047 Å and the longest Mn···Mn distance is 3.23 Å. The protonation level of O2− and H2O ligands was likewise corroborated by BVS calculations (Table S2). Further, 1 consists of significant intra and intermolecular hydrogen bonding interactions (i.e., N–H · · · O, N–H · · · N, C–H · · · O and C–H · · · N). The terminal water molecules which are coordinated to the sodium ions (Na1 and Na2) form hydrogen bonds to the nitrogen atoms of



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azide ligands d [(H2O)H15A···N27(N3)] = 2.013 Å and d [(H2O)H17A···N12(N3)] = 2.247 Å]. The nitrogen of the azide ligands also form the hydrogen bonding to the hydrogens of the thme−3 ligands d [(C4)H4A···N26(N3)] = 2.676 Å and d [(C1)H1C···N27(N3)] = 2.644 and play a significant role for the development of supramolecular networks (Fig. 3). The intramolecular H‒bonding d [N20···H20A(C20)] = 2.704 Å, d [N21···H14C(C14)] = 2.721 Å and d [N21··· H19B(C19)] = 2.673 Å involves between bridged azide group and hydrogens of the ligand (Fig. S6). Moreover, the significant intermolecular H‒bonding interactions like d [(N31)H31· ··N33(NO3)] = 2.618 Å, d [(H2O)O17···H42B(C42)] = 2.538 Å, d [(N3)N12···H42(C42)] = 2.723 Å, d [(N3)N27···H45(C45A)] = 2.594 Å, d [(NO3)O31···H31(N31)] = 2.166 Å and d [(NO3)O33···H31(N31)] = 2.273 Å (Fig. S7) along with some other uncommon interactions i.e., C···H(C) contacts are observed in 1 and play important role in the further consolidation of the crystal lattice (Fig. S7). The presence of these interactions additionally develops an inventive perspective to the crystallography, which may in this way be supposed to facilitate the supramolecular architectures. The topological analysis was performed with the ToposPro program package and the TTD collection of periodic network topologies [86]. The chains can be described by the underlying net of 2,2,3C6 topological type whose nodes correspond to Mn clusters, azide and nitrate anions (Fig. 4). The way the cluster chains are packed in the crystal can be described by the rod-packing net of hxl topological type (Fig. 5) [87].

Crystal

structure

investigations

of

[{MnII3MnIII9Na7(thmp)8(CH3O)(CH3CO2)11(μ2-O)2(μ6-O)2(O)5}·4(O)]n (2) The fully labelled central metallic core of the coordination polymer 2 is represented in Fig. 6, while selected bond length and angles are given in Table S1. 2 is crystallized in triclinic system with space group P−1 and has [Mn12Na7(μ2-O)4(μ3-O)21(μ3-OAc)2] core. The detailed information about crystallographic data collection and structure refinements is listed in Table


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1. The unit cell packing of the monomeric unit of 2 shown that only two asymmetric units are parallel arranged in the cell (unlike polymer 1 having six asymmetric units) (Fig. S8). The space-filling view of 2 shows a small central hole unoccupied by any guest molecule where the coordinated cyclic system which is created by six Mn6 core clusters of the four asymmetric units linked together via coordination bonds resulting in a cyclic hexagonal ring like structure. In this structure also, the manganese ions are so much buried and are not clearly visible (Fig. S9). The asymmetric unit of 2 consists of twelve manganese ions and seven sodium ions, water molecules, alkoxide (methanol), acetates and eight thmp3− ligands give peripheral ligation to metallic core in which two hexameric Mn6 units are bridged by the two acetates and oxygen atom of the water molecule producing a dumbbell like structure. The repeating unit is [Mn12Na7(μ2-O)4(μ3-O)21(μ3-OAc)2] core in which all Mn ions are in distorted octahedral geometry and create zig-zag chain like structure (Fig. S10) which is further linked through the coordination bond between sodium ion (Na1) and bridged O1W atom of the water, leading to the formation of the cyclic system in which six Mn6 cluster units are involved from the four asymmetric units (Fig. 7). Charge considerations, bond valence sum (BVS) calculations [84, 85] reveal a mixed-valence 3MnII9MnIII situation where Mn1A, Mn3A and Mn5B are as MnII ions and rest others are MnIII ions. The metallic core contains two unusual µ6‒O2− bridges (O1 and O2) (Fig. 6) as corroborated by bond‒valence sum (BVS) calculations (Table S2) [84, 85] that bind to all six central manganese ions together (Fig. S11). The protonation level of H2O and O2− was also supported by BVS calculations (Table S2). The coordination geometry around each MnIII ion is actually not a perfect octahedral, instead is significantly distorted, having two bonds longer than the other four bonds (Fig. S3), the axial elongations of the two Mn–O(R) Mn bonds being trans arrangement and Jahn–Teller (JT) distortion is present in MnIII ions (axial elongations) although these are not co-parallel as shown in Fig. S12. The +2 and +3 oxidation state of Mn ions further substantiated by the observed average bond lengths 2.123



and 2.067 of Mn–O for MnII and MnIII Å and these are in the normal range of MnII–O and MnIII–O bonds [83]. The sodium ions are present in two different type of the coordination environments (hexa and hepta), and such type of unique coordination numbers in one crystal system are not generally observed. All completely deprotonated thmp3− ligands bind in two different ways. Three of the eight thmp3− ligands adopt η3:η3:η2:µ5‒bridging mode and uses two arms in a μ3‒fashion, whereas the third arm acts as a μ2‒bridge mode of the alkoxide oxygen atoms to link five manganese ions (Scheme 2). Remaining five thme3− ligands adopt η3:η3:η3:µ6‒bridging to connect six manganese ions. The acetate ligands exhibited two types of bridging modes: seven adopt the common syn, syn, (η1:η1) μ2‒bridging mode to bridge two Mn ions, remaining four shown a less common η2:η1:µ2‒bridging mode that binds two manganese ions (Scheme 1) [88]. The methoxy group of the methanol solvent bridged to Mn1B ion in η1:µ1‒bridging fashion through O11D. 2 also forms significant intra and intermolecular hydrogen bonding (i.e., C–H · · · C and C–H · · · O). The intramolecular H‒bonding involves between oxygen and hydrogen atoms of the acetate and thme3− ligand (Fig. S13). Furthermore, the H‒bonding interactions like [(OAc)O42C · · · H16C(C16)], d = 2.551 Å present between oxygen atom of the acetate groups and the hydrogen atoms of the ligand molecules leads to the formation of supramolecular networks as shown in the Fig. S13. These secondary interactions C–H···O and C–H···C {d [(OAc)H52C···C62C] = 2.887 Å, d [(C26B)H26G···C16B] = 2.817 Å} (Fig. S14) play important role for the consolidation of crystal lattice. Further, ToposPro program package and the TTD collection of periodic network topologies [87] was used also for 2 to investigate the topological features. If we consider standard representation of the crystal structure taking into account Na and Mn atoms as complexing centers and all other atoms belonging to ligands, the topology of the resulting 31-nodal underlying 3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,6,6,6,6,6,6,6,6,7,7-c net with stoichiometry (3-c)2(3-c)(3-c)(3-c)(4-c)(4-c)(4-c)2(4-c)(4-c)(4-c)(4-c)(4-c)(4-c)(4-c)(4-c)(5-c)(5-c)(5-c)(5-


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c)(5-c)(5-c)(6-c)(6-c)(6-c)(6-c)(6-c)(6-c)(6-c)(6-c)(7-c)(7-c) is new and the point symbol of the

net

is

{3.4.5}2{3.47.52}2{32.410.52.6}{32.410.53}4{32.43.5.203.21}{32.43.5}6{32.44}2{32.46.52.63.7.8}{ 32.46.52}{34.44.52}{34.46.54.64.72.8}2{412.52.6}2{42.6}2{43}{45.5}3 {45.6}{46.63.8} (Fig. S15). An alternative consideration of the structure does not include sodium atoms as complexing since their bonds are weaker than the Mn-O bonds. In this case the structure is represented by isolated C34H59O24Mn6 complexes (Fig. 8 (a) and (b)). Assuming that the C34H59O24Mn6 cluster units are structural building blocks which are connected to each other through sodium atoms then chain with the (4,4)(0,2) topology will be the underlying net of the structure (Fig. 8 (c)). The main difference between 1 and 2 is that, in polymer 1 the azide and H3thme ligands provide the peripheral ligation and two Mn6 cluster units are bridged by the end to end azide ligand and nitrate ion while in 2, acetates and H3thmp ligands provide the peripheral ligation and two Mn6 cluster units are connected by the acetate ligands and oxygen atom of the water molecule. The difference between 1 and 2 is also represented in the polymeric chains and packing arrangements of the asymmetric unit in the unit cell. The four asymmetric units are arranged in unit cell for 1, which is different from 2 (having only two asymmetric units in the unit cell in nearly parallel style along the axis). 1 and 2 display an unprecedented structural topology, having novel feature as Na+ ions are intimately associated with Mn12 cores and can be considered as heterometallic with high nuclearities mixed-metal MnxMy coordination polymers. The most interesting structural feature of 2 is the unusual and exceptional “chain of rings” topology and to the best of our knowledge such type of coordination polymers have rarely been reported till date.

FT-IR spectral and Powder X-ray diffraction (PXRD) studies



The FT-IR spectra of the synthesized polymers 1, 2 and the free ligands were recorded within the range 4000–400 cm−1 (Fig. S16 and S17). The prominent peaks in the spectra of the complexes showed negative shift as compared to those observed in the free ligands ascertaining the binding of the metal to the ligand. In the spectra of 1 and 2, the sharp band due to the coordinated as well as the lattice water {νO–H(H2O)} molecules appears at ∼3400 cm−1. The metal clusters with polyalcohol ligands that exhibited the characteristic O‒H (hydrogen bonded) stretching vibration broad band at about 3320‒3360 cm−1 region is absent in both polymers indicating that ligands (H3thme and H3thmp) bind to metal ion as anionic form. For 1 and 2, stretching bands appeared at ∼2920 and ∼2850 cm−1 are representative of νas(C–H) and νs(C–H) vibrations. The vibration band at ∼1050 cm−1 is the characteristic of ν(C–O) frequency. 1 exhibits strong absorption band at 2070 cm−1 is assignable to the asymmetric stretching vibration of the N3 moiety [89]. The presence of the coordinated nitrates in 1 is ascertained by the stretching vibration band of nitrate (–ONO2) at 1410 cm−1. For 2, the stretching vibration bands are observed at 1600 cm−1 and ∼1430 cm−1 are due to νasym(–COO−) and νsym(COO−) stretching vibrations, respectively. The band at 1700 cm−1 that ascribed to (COO)asym of free carboxylic acids is shifted to lower frequency region of ∼1575 cm−1 corroborated that acetate ligands bind to metal through carboxyl group [90, 91]. A band appeared in the region of 940‒960 cm−1 is the characteristic of bridged ν(Mn–O–Mn) stretching vibrations. The coordination of ligands through N-atom and O-atoms to metal ion was further confirmed by the appearance of new bands in the low frequency 400–550 cm−1 region that are assignable to M−N and M−O bond stretching frequencies [90, 91]. Single crystal X‒ray crystallographic data for 1 and 2 further substantiated the azide and acetate bridging in the structures. For confirming the phase purity of samples, the powder X-ray diffraction (PXRD) measurements were done on bulk crystalline samples of 1 and 2. The observed PXRD patterns


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of both samples are in good agreement with the simulated patterns as shown in Figs. S18 and S19, corroborating the phase purity of 1 and 2. The negligible differences were observed in the intensity and the peaks may be due to the different orientation of the crystalline sample.

Magnetochemistry: Direct current (dc) magnetic susceptibility studies Solid state variable-temperature dc magnetic susceptibility measurements were done on powdered polycrystalline samples of 1 and 2 in 1.8‒300 K range and in 0.10 T applied field. The experimental data for both the coordination polymers are shown as χMT (molar susceptibity) vs T plots in Fig. 9. At 300 K, the χMT value as per formula of 1 is 27.6 cm3mol−1K which is lower than the spin-only theoretical (g = 2.00) value of 38.75 cm3mol−1K for a complex containing 10MnIII (S = 2, g = 2.00) and 2MnII (S = 5/2, g = 2.00) centers. The χMT value drops gradually as the temperature is lowered, to a lowest value of 15.15 cm3mol−1K at 27 K, and then abruptly increases to a maximum of 56.5 cm3mol−1K at 9 K, after that it drops again down to 18.5 cm3mol−1K till 1.8 K (Fig. 9 (a)). The magnetic behavior at 9–30 K indicates intrachain ferromagnetic interactions between Mn6 clusters. The sharp decrease of χMT below 9 K is due to the interchain dominant antiferromagnetic interactions. The sharp increase of the χMT upto a maximum and then its sudden drop suggests the long-range magnetic ordering and antiferromagnetic interactions or field saturation effect at low temperature [92]. The χMT value at 30 K implies a virtual ground state spin value (ST) of 5 for the ‘MnII2 MnIII10’ repeating unit induced by considerable antiferromagnetic coupling. 1 approximates the Curie-Weiss behavior and generated best-fit parameters above 50 K are, Curie constant (C) = 33.33 cm3mol−1K and Weiss constant (Θ) = −59.66 K (Fig. S20 (a)). Though, χMT value does not reach to zero even at 1.8 K signifying that 1 has a relatively high-spin ground state i.e., low-lying excited states are however considerably populated.



The experimental χMT value for 2 at 300K is 11.20 cm3mol−1K which is quite lower than the expected (40.12 cm3mol−1K) for nine non interacting high spin MnIII (S = 2) and three highspin MnII (S = 5/2) ions. This lower magnitude of the χMT at RT is attributed to the presence of strong antiferromagnetic interactions. The χMT value progressively falls from 11.20 cm3mol−1K at 300 K to ~0 cm3mol−1K at the lowest temperature 1.8 K (Fig. 9 (b)). The χMT value and the nature of curve in case of 2 is suggestive of a strong antiferromagnetically coupled system which is different from that of 1. The value at 1.8 K is consistent with an S = 0 ground state. In 𝜒M―1 versus T plot, the deviation from the linearity was observed below 55 K. The 𝜒M―1 versus T approximate the Curie-Weiss behaviour and the estimated parameters, Curie constant (C) is 14.72 cm3mol−1K and Weiss constant (Θ) is −49.87 K (Fig. S20 (b)). Further, the high negative Weiss constant (Θ) value substantiated the presence of strong antiferromagnetic interactions. Being the large size and complexity of both the polymers, it is not conceivable to determine the individual pairwise exchange interaction parameters between the manganese centers by applying the Kambe method [93], and likewise the direct matrix diagonalization methods are computationally not feasible.

Alternating current (ac) magnetic susceptibility studies The ac susceptibility studies were done on polycrystalline samples of 1 and 2 in the 2.0‒15 K temperature range in applied zero dc field and in a 5.0 G ac field oscillating at frequencies 10‒1500 Hz. If the magnetization vector can relax so quickly to continue with the oscillating field, no out of phase susceptibility χMʹʹ signal will be observed and in-phase susceptibility χMʹT signal will be equivalent to the dc susceptibility. On the other hand, if the magnetization relaxation barrier is significant compared to thermal energy (kT), at that point the in-phase signal drops and a non-zero, frequency-dependent χMʹʹ signal appears, which is indicative of the superparamagnetic-like nature of an SMM. To probe the SMM behavior for 1, ac magnetic


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susceptibility studies as a function of temperature and frequency were performed. The in-phase (χMʹT) and out-of-phase (χMʹʹ) magnetic susceptibility indicated noticeable frequency dependency in the 2.0–15 K temperature range (Fig. 10), as the frequency increases the peak maxima shifting to higher temperature. This behavior signifies the slow relaxation of the magnetization, as observed for SMMs. Moreover, observation of frequency dependence of peak shifting toward higher temperatures with increase in frequency in out of phase component is in line with the characteristic of spin glasses (SGs) or superparamagnets. The frequency dependence, ϕ = (ΔTp/Tp)/Δ(log f ) (Tp being the temperature at which χMʹʹ reaches a maximum) is calculated to be 0.09, which is the typical value for SGs (ϕ < 0.1) [94, 95]. Henceforth, the present system (1) is also an example of spin glass. Furthermore, the relaxation time was obtained by the Arrhenius equation τ = τ0 exp(Δτ/KBT). The best fitting of the experimental data provides parameters for the effective energy barrier (Δτ/KB) for the reversal of magnetization of 75.5 K and τ0 = 4.35 × 10−12 s (Fig. 10 (b) inset). This energy barrier may originate from the combination of the magnetic anisotropy and high-spin ground state of manganese ions in 1. It is accepted that the χMT value is corresponding to the correlation length (ξ) and rises exponentially with decreasing temperature for an anisotropic Heisenberg or Isinglike one-dimensional system. The observed linear behavior in ln(χMT) vs. 1/T plot in the 12-25 K temperature range is suggestive of the strong Ising-like anisotropy of 1 and linear fitting of the data using the equation χMT = Ceff exp(Δξ/kBT) [96] gives Ceff = 5.30 cm3mol−1K and Δξ/kB = 26.07 K, respectively (Fig. 11). The Ceff is the effective Curie constant, and Δξ is the correlation energy, which provides an approximation of the intrachain exchange energy needed to create a domain wall within the chain [97‒99]. For 2, frequency dependent in phase signal (χMʹT) decreases very slightly (negligible) in this temperature range, and is distinctly close to ∼0 cm3mol−1K (Fig. S21), confirming ground state S = 0 (not too much isolated from the exited states i.e., there is very little population of the latter up to 14 K). 2 did not show out-of-phase



ac signals even at the lowest temperature (i.e., 2.0 K) (Fig. 12), demonstrating that it does not display a large enough barrier to show the superparamagnet-like relaxation of its magnetization vector corroborating that, it is not an SMM. Hence, our initial expectation, from the dc information, of very low-lying excited states for 2 is additionally substantiated by the ac susceptibility studies (vide supra).

Magnetization versus dc field hysteresis studies. To investigate further the conclusion of the ac out-of-phase data that 1 and 2 might be an SMM, the field dependence of the magnetization was determined in the 2.0, 3.0 and 4.0 K temperatures with a fixed-field sweep rate of 0.05 T s−1 (Fig. 13), the hysteresis loop can be distinctly observed for 1 at 2.0 K (Fig. 13 (a) inset), giving a coercive field (HC = 1069.10 Oe) and a remanent magnetization (MR = 0.374 μB) and coercivity decreases significantly as the temperature increases. The magnetization rises swiftly as the field is raised from zero, and then gradually increases to 0.90 μB for 1 at 6.0 T. It is clear from the figure that this is lower than the saturation value, corroborating the antiferromagnetic ground state associated with the competition between ferromagnetic and antiferromagnetic coupling, a behavior which is suggestive of several other one-dimensional manganese chain compounds [98, 100]. This behavior might be due to the presence of a frozen magnetized state without regard to the three dimensional ordering. No steps characteristic of QTM were observed in the hysteresis loops that are generally noticeable in the smaller SMMs, and this is normal case for large complexes [101, 102] for which steps are broadened and smeared out from a distribution of molecular environments [103]. For 2 there are clearly no hysteresis loops observed at the given temperatures (i.e., 2.0, 3.0 and 4.0 K). There is a fast increment in magnetization at low field, following a gradual rise at high field, however no saturation was seen even at the highest field (7.0 T) (Fig. 13 (b)), which is again suggestive of antiferromagnetic interactions [104]. This is


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not characteristic SMM behavior, for that one would generally assume a considerably high dependence of the coercivity on the temperature [63].

Conclusion In this work, two new azido and acetate bridged heterometallic coordination polymers, [{MnII2MnIII10Na2(μ6-O)2(N3)10(NO3)(H2O)4(thme)8}·3(Et3NH)]n (1) and [{MnII3MnIII9Na7(μ2O)2(μ6-O)2(O)5(CH3O)(CH3CO2)11(thmp)8}·4(O)]n (2) using tripodal polyalcohol ligands have been synthesized and characterized. The lots of efforts have been given to develop the novel structures in determining magneto-structural correlations and to produce magnetic materials using small bridging ligands i.e., azide and acetate in coordination chemistry and molecular magnetism. The results demonstrate here that the flexible polyalcohol ligands with bridging auxiliary ligands play very important role in the designing of the topological architectures. Magnetic investigations suggest that 1 behaves as SMM with relaxation energy barrier of 75.5 K, while 2 shows antiferromagnetic interaction. To the extent of our knowledge, both are new type of coordination polymers with retaining Mn12 metallic core. While 1 has straight polymeric chain, 2 is unique polymer of hexameric ring of the four monomeric unit. This is very interesting that replacing the bridging ligand can modify the structural designs of the systems which leads to distinctive type of magnetic interactions and furthermore causing in remarkable changes in magnetic behaviors. This work could significantly contribute to the field of molecular magnetism to get desirable magnetic properties by modulating the structure and bridging ligands in coordination polymers.

Acknowledgements The authors thank Chairman, Department of Chemistry, AMU, Aligarh, for providing required research facilities. Mo Ashafaq thanks UGC, New Delhi, for Junior Research Fellowship. We



thank Dr. Yogesh Singh, IISER Mohali for assistance with QD (Quantum Design) PPMS (Physical Property Measurement System) and Cryogenic Ltd SQUID facilities at IISER Mohali. M.K. thanks UGC New Delhi for start-up grant. Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: xxxxxxxxxx. X-ray structural studies, FTIR spectra, PXRD patterns, magnetic data and BVS parameters, and X-ray crystallographic data of 1 and 2 (PDF). Accession Codes CCDC 1820166 and 1813726 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.


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Figure captions

Fig. 1. Central metallic core of the polymeric unit of 1. H-atoms have been omitted for the clarity. Color code: Mn, magenta; Na, gold; O, red; N, green; and C, blue. Fig. 2. View of the azido-bridged 1D chain unit in 1. Fig. 3. The packing arrangement of the 1. Fig. 4. (a) NaMn6O15N12C20H40 cluster (b) Coordination polyhedra are shown for Mn atoms; (c) Chains of 2,2,3C6 topological type of clusters run in [001] direction in 1. Fig. 5. Fragment of the crystal structure (left) and corresponding rod-packing net of hxl topological type (right) of 1. Triethylammonium cations are omitted for clarity. Fig. 6. Central metallic core of the polymeric unit of 2. H-atoms have been omitted for the clarity. Color code: Mn, magenta; Na, gold; O, red and C, green. Fig. 7. View of the water and acetate-bridged polymeric chain of hexameric cyclic rings of Mn6 metallic core in 2. Fig. 8. (a) The topology of the complex (C34H59O24Mn6) is 3,3,6M11-1, (b) Underlying net with 3,3,6M11-1 topology (left) in the structure with the sodium atom removed, where ZA=C6H11O3; ZG=O; ZI=Mn. If the ligand center of gravity ZA and the oxygen atom ZG contract to the manganese atom ZI, then the 5M6-1 topology will be obtained (right), (c) Underlying net with (4,4)(0,2) topology of 2. Fig. 19. The χMT vs T plots for 1 (a) and 2 (b) at an applied field of 0.1 T (Tesla). Fig. 10. The ac susceptibility of 1 in a 5.0 G field oscillating at the indicated frequencies: (a) in-phase (χMʹ) signal plotted as χMʹT versus T and (b) out-of-phase signal χMʹʹ versus T. Inset: Arrhenius lnτ vs 1/T plot for 1; see text for the fit parameters. Fig. 11. Plot of ln(χMT) vs. 1/T for 1. Solid red line denotes the best fitting to a linear regime. Fig. 12. Out-of-phase AC magnetic susceptibility of 2 as the χMʹʹ versus T plot, with the 5.0 G AC field oscillating at the indicated frequencies. Fig. 13. Magnetization versus field hysteresis loops measured for 1 (a); Inset: hysteresis loop showing coercivity at 2.0 K and 2 (b) at different temperatures.


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Fig. 1. Central metallic core of the polymeric unit of 1. H-atoms have been omitted for the clarity. Color code: Mn, magenta; Na, gold; O, red; N, green; and C, blue.

Fig. 2 View of the azido-bridged 1D polymeric chain unit of 1.



Fig. 3. The packing arrangement of the 1.


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Fig. 4. (a) NaMn6O15N12C20H40 cluster (b) Coordination polyhedra are shown for Mn atoms; (c) Chains of 2,2,3C6 topological type of clusters run in [001] direction in 1.



Fig. 5. Fragment of the crystal structure (left) and corresponding rod-packing net of hxl topological type (right) of 1. Triethylammonium cations are omitted for clarity.

Fig. 6. Central metallic core of the polymeric unit of 2. H-atoms have been omitted for the clarity. Color code: Mn, magenta; Na, gold; O, red and C, green.


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Fig. 7. View of the water and acetate-bridged polymeric chain of hexameric cyclic rings of Mn6 metallic core in 2.



Fig. 8. (a) The topology of the complex (C34H59O24Mn6) is 3,3,6M11-1, (b) Underlying net with 3,3,6M11-1 topology (left) in the structure with the sodium atom removed, where ZA=C6H11O3; ZG=O; ZI=Mn. If the ligand center of gravity ZA and the oxygen atom ZG contract to the manganese atom ZI, then the 5M6-1 topology will be obtained (right), (c) Underlying net with (4,4)(0,2) topology of 2.


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Fig. 9. The χMT vs T plots for 1 (a) and 2 (b) at an applied field of 0.1 T (Tesla).



Fig. 10. The ac susceptibility of 1 in a 5.0 G field oscillating at the indicated frequencies: (a) in-phase (χMʹ) signal plotted as χMʹT versus T and (b) out-of-phase signal χMʹʹ versus T. Inset: Arrhenius lnτ vs 1/T plot for 1; see text for the fit parameters.


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Fig. 11. Plot of ln(χMT) vs. 1/T for 1. Solid red line denotes the best fitting to a linear regime.

Fig. 12. Out-of-phase AC magnetic susceptibility of 2 as the χMʹʹ versus T plot, with the 5.0 G AC field oscillating at the indicated frequencies.



Fig. 13. Magnetization versus field hysteresis loops measured for 1 (a); Inset: hysteresis loop showing coercivity at 2.0 K and 2 (b) at different temperatures.

Scheme. 1. The structure of tripodal ligands, 1,1,1- tris(hydroxymethyl)ethane (H3thme) and 1,1,1tris(hydroxymethyl)propane (H3thmp).


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Scheme. 2. Bridging modes displayed by the azides and acetates in 1 and 2. Colour scheme: metal, Magenta; carbon, green; oxygen, red; nitrogen, light blue and hydrogen, light grey.

Scheme. 3. Bridging modes displayed by the tripodal alcohols (tripodal = thme and thmp) in 1 and 2. Colour scheme: metal, magenta; carbon, green and oxygen, red.



Table 1. Crystallographic data and refinement parameters for 1 and 2. Compound 1 2 Empirical formula C58H128Mn12Na2N34O33 C71H119Mn12Na7O60 MnII2535.20 MnIII 2752.86 MnIV FormulaAtom weight Temperature/K 293(2) 1 296(2) Crystal system Mn1 3.338monoclinic 3.078 triclinic 3.020 Space group P21/n P-1 Mn2 3.12111.0917(2) 2.878 14.1285(7) 2.824 a/Å Mn3 2.37340.8349(8) 2.188 19.3507(10) 2.147 b/Å Mn4 3.34321.2471(4) 3.082 22.1076(11) 3.024 c/Å α/° Mn5 3.21390 2.962 82.537(2) 2.907 β/° 91.0790(10) 81.440(3) Mn6 2.925 2.697 2.647 γ/° 90 84.769(2) Mn7 3.3299621.7(3) 3.069 5910.3(5) 3.012 3 Volume/Å Mn8 3.1844 2.936 2 2.881 Z 3 Mn9 3.2191.750 2.968 1.547 2.913 ρcalc (g/cm ) -1 Absorption coeffient (μ) (mm 3.361 ) 1.620 Mn10 3.099 1.350 3.041 F(000) Mn11 5200.0 2804.0 2.096 1.933 1.897 Radiation MoKα (λ = 0.71073) MoKα (λ = 0.71073) Mn12 3.035 1.876 to 50.5042.978 2Θ range for data collection/° 3.2914.23 to 50.5 Reflections collected 119025 20822 Data/restraints/parameters 17412/0/1273 20822/4008/1425 Goodness-of-fit on F2 1.045 1.028 R1 = 0.0415, wR2 = Final Ra, b indexes [I>=2σ (I)] R1 = 0.0837, wR2 = 0.2275 0.0964 R1 = 0.0608, wR2 = Final R indexes [all data] R1 = 0.1660, wR2 = 0.3072 0.1090 Largest diff. peak/hole /e Å-3 1.52/-0.90 1.12/-0.54 aR

1

=  Fo – Fc/Fo with Fo2>2(Fo2). bwR2 = [w(Fo2–Fc2)2/Fo22]1/2


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2 Mn1A 2.462 2.288 2.246 Mn2A 3.127 2.884 2.830 Mn3A 2.479 2.355 2.311 Mn4A 3.127 2.883 2.829 Mn5A 3.028 2.792 2.740 Mn6A 2.965 2.734 2.682 Mn1B 2.933 2.704 2.654 Mn2B 3.040 2.803 2.751 Mn3B 3.101 2.859 2.806 Mn4B 3.114 2.871 2.818 Mn5B 2.472 2.323 2.279 Mn6B 3.044 2.807 2.754 Table 2. Bond valence sum calculation of manganese (Mn) oxidation state in the crystal structure of 1 and 2 [a] [a] The Values in bold italicised underlined are the closest to the charge for which it was calculated; the nearest whole number can be taken as the oxidation state of that atom.

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Crystal engineering and magnetostructural properties of newly designed azide/acetate-bridged Mn12 coordination polymers Mo Ashafaq, Mohd Khalid*, Mukul Raizada, Anzar Ali, Mohd Faizan, M. Shahid, Musheer Ahmad, Ray J. Butcher

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Synopsis Two rare μ6-oxo centered azide and acetate bridged heterometallic coordination polymers, [{MnII2MnIII10Na2(μ6-O)2(N3)10(NO3)(H2O)4(thme)8}·3(Et3NH)]n (1) and [{MnII3MnIII9Na7(μ2O)2(μ6-O)2(O)5(CH3O)(CH3CO2)11(thmp)8}·4(O)]n (2) are synthesised and characterized crystallographically and magnetically. The magnetic investigations for 1 indicate its single molecule magnet (SMM) behavior.


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Crystal engineering and magnetostructural properties of newly

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