Synthesis, Crystal Structure, Fluorescence, Thermal Stability and Magnetic Properties of the Dinuclear Manganese(II) Complex [Mn2(L)2(2,2?-bipy)2(H2O)5]2·3H2O①

LI WeiLI Chang-HongLI Yu-LinLI Heng-Feng(Shool of Materials Siene and Engineering, Central South University, Changsha 410083, China)(Department of Chemistry and Materials Siene, Hengyang Normal University, Hengyang 421008, China)(Department of Chemial Engineering, Hunan Institute of Tehnology, Hengyang 421002, China)

Synthesis, Crystal Structure, Fluorescence, Thermal Stability and Magnetic Properties of the Dinuclear Manganese(II) Complex [Mn2(L)2(2,2?-bipy)2(H2O)5]2·3H2O①

LI Weia,b②LI Chang-HongcLI Yu-LinbLI Heng-Fenga②a(School of Materials Science and Engineering, Central South University, Changsha 410083, China)b(Department of Chemistry and Materials Science, Hengyang Normal University, Hengyang 421008, China)c(Department of Chemical Engineering, Hunan Institute of Technology, Hengyang 421002, China)

A new dinuclear manganese complex [Mn2(L)2(2,2?-bipy)2(H2O)5]2·3H2O has been synthesized with MnSO4·H2O, 2,2?-bibenzoic acid (H2L) and 2,2?-bipyridine(2,2?-bipy) in the mixed solvent ethanol and water.It crystallizes in monoclinic, space group P1 with a = 9.9944(10), b = 21.939(2), c = 25.628(3) ?, α = 108.429(3), β = 100.613(4), γ = 102.821(3)o, V = 4997.9(9) ?3, Dc= 1.355 g/cm3, Z = 2, F(000) = 2108, GOOF = 1.074, the R = 0.0626 and wR = 0.1531.The structure of the complex contains two [Mn2(L)2(2,2?-bipy)2] units, ten coordinated H2O molecules and three uncoordinated H2O molecules.The fluorescence, thermal stability and magnetic properties of the complex were investigated.

dinuclear manganese complex, fluorescence, thermal stability and magnetic properties;

1 INTRODUCTION

Recently, increasing attention has been paid to the use of dicarboxylic acid bridging units in the construction of supramolecular architectures[1], and this approach is attractive because the variety and conformational freedoms of such ligands offer the possibility for the construction of unprecedented frameworks[2].However, due to less predictability of the coordination architectures self-assembled by such ligands and metal centers[3], there is still a very long way to develop new metal-organic coordination architectures using dicarboxylic acid ligands to rationalize the design of compounds with welldefined structures and useful functions[4].Up to now, in this field, much attention has been focused on pyridine dicarboxylic acid system with multiconnecting ability ligand, for example, 2,3-, 2,5-, 3,4- and 3,5-pyridine dicarboxylic acids have been found to act as excellent building blocks in theconstruction of functional complexes[5].2,2?-Bipyridine acid (H2L), a carboxylic acid ligand with the advantages of multiple coordinating atoms and bridging, can lead to a variety of connectivity for transition metal centers and provide various structural motifs[6].In order to further investigate the influence of dicarboxyl acid ligand H2L and different metal ions on the coordination architectures and properties, we report here the crystal structure, fluorescence, thermal stability and magnetic properties of a new tetranuclear manganese(II) complex [Mn2(L)2(2,2?-bipy)2(H2O)5]2·3H2O (1) with H2L as the ligand.

2 EXPERIMENTAL

2.1 Materials and instruments

All reagents were of analytical grade and used as obtained from commercial sources and used without further purification.Elemental analyses were performed on a Perkin-Elmer 2400 elemental analyzer.IR spectra were recorded on a Bruker Vector22 FT-IR spectrophotometer using KBr discs.The fluorescent spectra for the powdered solid samples were measured on an RF-5301PC spectrofluorometer with a xenon arc lamp as the light source.Thermogravimetric analyses were performed on a simultaneous SPRT-2 pyris1 thermal analyzer at a heating rate of 10 ℃·min-1.Magnetic measurements in the range of 2.8 ~ 300 K were performed on a MPMS-SQUID magnetometer at a field of 2 kOe on a crystalline sample in the temperature settle mode.

2.2 Preparation of 1

Complex 1 was prepared by H2L (48.4 mg, 0.2 mmol), 2,2?-bipy (31.2 mg, 0.2 mmol) and manganese sulfate (33.8 mg, 0.2 mmol) and dissolved in 20 mL mixed solvent ethanol and water (V1:V2 = 3:1).The pH value of the resultant mixture was adjusted to about 6.0 by adding sodium hydroxide solution.The reaction was kept under water-bath condition and stirred at 75 ℃ for nearly 18 h.Afterwards, the resultant solution was filtrated, untouched and evaporated slowly at room temperature.Weak yellow block-shaped single crystals suitable for X-ray diffraction analysis were obtained about two weeks later.Yield: 48% (based on L).m.p.: 268.5 ~ 270.0 ℃.Anal.Calcd.for (C48H42Mn2N4O13)2·3(H2O) (%): C, 49.47; H, 4.16; N, 5.48.Found: C, 49.32; H, 4.17; N, 5.49.Main IR (KBr, cm-1): 3422(s), 3051(s), 1691(vs), 1597(vs), 1506(vs), 1372(vs), 1311(m), 1283(m), 1161(m), 1032(m), 762(vs), 702(m), 666(w), 665(w), 546(w), 426(w).

2.3 X-ray structure analysis

A single crystal with dimensions of 0.26 mm × 0.20 mm × 0.18 mm was put on a Bruker SMART APEX CCD diffractometer equipped with a graphite-monochromatic MoKα radiation (l = 0.71073 ?) using a φ-ω scan mode at 173(2) K.A total of 74590 reflections were collected in the range of 1.35≤θ≤25.01°, of which 22939 were independent (Rint= 0.0305) and 13442 were observed (I > 2s(I)).All data were corrected by Lp factors and empirical absorption.The crystal structure was solved directly by program SHELXS-97[7], and refined by program SHELXL-97[8].The hydrogen and non-hydrogen atoms were corrected by isotropic and anisotropic temperature factors respectively through full-matrix least-squares method.The final R = 0.0626, wR == 0.514 and (?ρ)min= –0.621 e·?-3.

3 RESULTS AND DISCUSSION

3.1 Structure description

The molecular structure of 1 is shown in Fig.1.Hydrogen bond linking of the neighboring molecules is shown in Fig.2.The selected bond lengths and bond angles are shown in Table 1, and hydrogen bonds of 1 are shown in Table 2.

As shown in Fig.1, the asymmetric unit in 1 contains two [Mn2(L)2(2,2?-bipy)2] units, ten coordinated H2O molecules and three uncoordinated H2O molecules.In the independent unit, two manganese(II) ions are linked by H2L groups to form adinuclear structure and five coordinated water molecules, where the end positions are coordinated with two 2,2?-bipy molecules.The coordination geometry of the Mn1 atom is a distorted octahedron with two nitrogen atoms from 2,2?-bipy, two oxygen atoms from two L2-ligands and two oxygen atoms from two H2O molecules, but the Mn2 atom is coordinated by two nitrogen atoms from 2,2?-bipyridine, one oxygen atom from one L2-ligand and three oxygen atoms from H2O molecules.In complex 1, the carboxyl group is coordinated with manganese in the form of dentate modes after dissociating H.The Mn××Mn distance through the H2L bridge is 6.717 ~ 6.721 ?.The bond angle O/N–Mn–N/O is 71.29 ~ 170.53o.The Mn–N bond lengths range from 2.196 to 2.279 ?, and the Mn–O bond lengths vary from 1.149 to 2.223 ?.Fig.2 and Table 2 show the strong hydrogen bonding interactions, which exist between water molecules and H2L oxygen atoms: O(8W)–H(8X)××O(16) (2.6359 ?, 139o), O(11W)–H(11Y)××O(1) (2.8080 ?, 123o).There exists hydrogen bonding between oxygen atoms from water molecules and nitrogen atoms from 2,2?-bipy, such as O(8W)–H(8Y)··N(10) (3.5184 ?, 158o) and O(9W)–H(9X)··N(9) (3.2997 ?, 147o).There are a large number of hydrogen bonds between the oxygen atoms with coordinated H2O and free water molecules: O(11W)–H(12X)··O(12w) (2.6603 ?, 111o), O(12W)–H(12X)··O(4w) (2.7846 ?, 143o).

Table 1.Selected Bond Lengths (?) and Bond Angles (°) for the Title Complex

Table 2.Hydrogen Bond Lengths (?) and Bond Angles (°) for the Title Complex

Fig.1.Molecular structure of the title complex

Fig.2.Hydrogen bond linking of the neighboring molecule

3.2 Fluorescent properties

The fluorescent properties of 1 were studied in the solid state at room temperature (Fig.3).As illustrated in Fig.3, complex 1 shows strong blue fluorescence, with an emission maximum at 436 nm upon excitation at 355 nm.According to Mn(II) clusters with L ligands and simple Mn(II) complexes of mixed-ligand systems[9], the emission is tentatively assigned to the ligand-to-metal charge transfer (LMCT) (L→Mn).

3.3 Thermogravimetric analyses

and magnetic properties

Fig.3.Emission and excitation spectra of 1: A: excitation spectrum (λmax= 318 nm); B: emission spectrum (λmax= 430 nm)

Thermal stability property (TG) of complex 1 in air was executed on a PRT-2 pyris1 instrument, as shown in Fig.4.There are four weight loss stages from room temperature to 600 ℃.The first stage takes place from 164.7 to 255.7 ℃with the weight loss of 2.70%, corresponding to the release of three free water molecules (calcd.2.65%).The second stage occurs at 255.7～305.7 ℃with the weight loss of 30.61%, resulting from the loss of four 2,2?-bipy molecules (calcd.30.63%).There is a strong endothermic peak near 269.0 ℃ attributed to melting point of the complex, which conforms to that of the compound.The third stage is observed from 305.7 to 315.7 ℃ with the weight loss of 8.789% due to the departure of ten coordinated water molecules (calcd.8.83%).The fourth stage occurs from 315.7 to 417.5℃with the weight loss of 43.90%, corresponding to the release of four L molecules (calcd.43.96%), in agreement with the crystal structure.In air, the final product is manganese oxide with the residual weight being about 13.99% (calcd.13.91%).

Fig.4.TG and DTG curves of 1

The temperature dependence of magnetic susceptibility of 1 was investigated from 300 to 2.8 K with an applied magnetic field of 2 kOe.The XMT vs.T and 1/XMvs.T curves are shown in Fig.5, where XMT decreases gradually from 1.822 cm3·K·mol-1at 300 K to 1.660 cm3·K·mol-1at 2.8 K.In addition, according to the Curie-Weiss law, XM= C/(T – θ), the Curie constant (C = 1.8168 cm3K·mol-1) and Weiss constant (θ = –1.8607 K) are obtained from a linear fit of the 1/χmdata between 2.8 ~ 300 K.Such magnetic behavior indicates that 1 is a paramagnetic system, and shows weak antiferromagnetic properties[10].

Fig.5.Temperature dependence of the magnetic susceptibility of 1 in the form of XmT vs.T and 1/Xmvs.T

REFERENCES

(1) (a) Ayhan, O.; Malaestean, L.L.; Ellern, A.; Leusen, J.V.; Baca, S.G.; Kogerler, P.K.Assembly of cerium(III) 2,2?-bipyridine-5,5?-dicarboxylate-based metal-organic frameworks by solvent tuning.Cryst.Growth Des.2014, 14, 3541–3548.(b) Zhu, Y.G.; Zhang, Q.B.; Li, S.M.; Lin, Q.H.; Fu, P.; Zhang, G.T.; Zhang, H.B.; Shi, R.; Zhu, W.M.; Zhang, C.S.Insights into caerulomycin a biosynthesis: a two-component monooxygenase crmH-catalyzed oxime formation.J.Am.Chem.Soc.2013, 135, 18750–18753.(c) He, H.Y.; Yuan, D.Q.; Ma, H.Q.; Sun, D.F.; Zhang, G.Q.; Zhou, H.C.Control over interpenetration in lanthanide-organic frameworks: synthetic strategy and gas-adsorption properties.Inorg.Chem.2010, 49, 7605-7607.(d) Khullar, S.; Mandal, S.K.Supramolecular assemblies of dimanganese subunits and water clusters organized by strong hydrogen bonding interactions: single crystal to single crystal transformation by thermal de-rehydration processes.Cryst.Growth Des.2012, 12, 5329-5337.

(2) (a) Li, Z.; Fowler, F.W.; Lauher, J.W.Weak Interactions dominating the supramolecular self-assembly in a salt: a designed single-crystal-to-single-crystal topochemical polymerization of a terminal aryldiacetylene.J.Am.Chem.Soc.2009, 131, 634–643.(b) Wang, Y.; Liu, G.X.Synthesis, crystal structure and photoluminescent properties of a novel N,O-bifunctional Schiff-base ligand anditscadmium(Ⅱ) complex.Chin.J.Inorg.Chem.2009, 25, 713-719.(c) Sarcevica, I.; Orola, L.; Veidis, M.V.; Podjava, A.; Belyakov, S.Crystal and molecular structure and stability of isoniazid cocrystals with selected carboxylic acids.Cryst.Growth Des.2013, 13, 1082–1090.(d) Okutani, K.; Nozaki, K.; Iwamura, M.Specific chiral sensing of amino acids using induced circularly polarized luminescence of bis(diimine)dicarboxylic acid europium(III) complexes.Inorg.Chem.2014, 53, 5527–5537.

(3) (a) Nihei, M.; Sekine, Y.; Suganami, N.; Nakazawa, K.; Nakao, A.; Nakao, H.; Murakami, Y.; Oshio, H.Controlled intramolecular electron transfers in cyanide-bridged molecular squares by chemical modifications and external stimuli.J.Am.Chem.Soc.2011, 133, 3592–3600.(b) Goher, M.A.S.; Youssef, A.A.; Mautner, F.A.A new photoluminescent and antibacterial polymeric silver(I) complex generated from pyridine-2,3-dicarboxylic acid.Polyhedron 2006, 25, 1531-1536.(c) Imai, O.; Murata, K.; Kamon, K.; Kinuta, T.; Sato, T.; Kuroda, R.; Matsubara, Y.Formation and crystal structure of two-component host system having helical chirality and comprising 9,10-dihydro-9,10-ethanoanthracene-11,12-diamine and 1,1?-binaphthyl-2,2?-dicarboxylic acid.Cryst.Growth Des.2009, 9, 602–605.

(4) (a) Wang, Q.W.; Guan, Y.; Li, X.M.; Gao, G.G.; Liu, B.; Li, F.Y.Hydrothermal synthesis, crystal structure and magnetic properties of a novel zero-dimensional manganese(Ⅱ) complex with 2,2?-diphenic acid and 1,10-phenanthroline ligands.Chin.J.Struct.Chem.2007, 26, 1066-1070.(b) Tian, D.; Pang, Y.; Guo, S.Q.; Zhu, X.F.; Zhang, H.Syntheses, crystal structures, and magnetic properties of two new manganese(II) complexesbased on biphenyl-2,5,2?,5?-tetracarboxylic acid.J.Coord.Chem.2011, 64, 1006-1010.(c) Du, L.; Fang, R.B.; Zhao, Q.H.Pentaaqua-1K2O2K3O-bis(2,2?-bipyridine)-1K2N,N?;2K2N,N?-biphenyl-2,2?- dicarboxylato-1:2 K2O:O?-biphenyl-2,2?-dicarboxylato-K-dimanganese(II) tetrahydrate.Acta Crystallogr Sect.E 2007, 63, 1439-1441.(d) Xu, X.X.; Liu, X.X.; Zhang, X.; Sun, T.Synthesis, characterization and magnetic properties of coordination polymers of manganese with 1,1?-biphenyl-2,2?-dicarboxylic acid ligands.Transition Met.Chem.2009, 34, 827-833.(e) Koo, B.K.Synthesis and crystal structures of Mn(II)- and Ni(II)-dicarboxylate complexes with 1,10-phenanthroline.Bulletin of the Korean Chem.Soc.2012, 33, 2299-2304.

(5) (a) Staehle, R.; Tong, L.P.; Wang, L.; Duan, L.L.; Fischer, A.; Ahlquist, M.S.G.; Sun, L.C.; Rau, S.Water oxidation catalyzed by mononuclear ruthenium complexes with a 2,2?-bipyridine-6,6?-dicarboxylate (bda) ligand: how ligand environment influences the catalytic behavior.Inorg.Chem.2014, 53, 1307–1319.(b) Gustafsson, M.; Su, J.; Yue, H.J.; Yao, Q.X.; Zou, X.D.A family of flexible lanthanide bipyridinedicarboxylate metal-organic frameworks showing reversible single-crystal to single-crystal transformations.Cryst.Growth Des.2012, 12, 3243–3249.(c) Liu, Y.; Kravtsov, V.C.; Beauchamp, D.A.; Eubank, J.F.; Eddaoudi, M.Metal-organic polyhedron based on a Cu(II) paddle-wheel secondary building unit at the truncated octahedron corners.J.Am.Chem.Soc.2005, 127, 7266-7267.

(6) (a) Zhang, S.H.; Li, C.H.; Li, W.; Tan, X.W.; Zhou, S.Q.Synthesis, crystal structure and thermal stability of complex [Cu(C14H10O4)(C12H8N2)2]·2H2O.Chin.J.Struct.Chem.2011, 30, 1493-1496.(b) Zhang, F.W.; Li, Z.F.; Ge, T.Z.; Yao, H.C.; Li, G.; Lu, H.J.; Zhu, Y.Y.Four novel frameworks built by imidazole-based dicarboxylate ligands: hydro(solvo)thermal synthesis, crystal structures, and properties.Inorg.Chem.2010, 49, 3776–3788.(c) Zhou, J.Z.; Shi, W.; Xu, N.; Cheng, P.A new family of 4f-3d heterometallic metal-organic frameworks with 2,2?-bipyridine-3,3?-dicarboxylic acid: syntheses, structures and magnetic properties.Cryst.Growth Des.2013, 13, 1218–1225.

(7) Sheldrick, G.M.SADABS, Program for Bruker Area Detector Absorption Correction.University of G?ttingen: G?ttingen, Germany 1997.

(8) Sheldrick.G.M.SHELXS-97, Program for Crystal Structure Solution.University of G ? ttingen: G?ttingen, Germany 1997.

(9) (a) Cuttell, D.G.; Kuang, S.; Fanwick, P.E.; Mcmilin, D.R.; Walton, R.A.Simple Cu(I) complexes with unprecedented excited-state lifetimes.J.Am.Chem.Soc.2002, 124, 6-10.(b) Wang, J.W.; Zhang, Y.H.; Li, H.X.; Lin, Z.J.; Tong, L.M.Construction of pyridinethiolates bridged 2D and 3D coordination networks of d10metal halides via solvothermal in-situ disulfide cleavage reactions.Cryst.Growth Des.2007, 7, 2352-2360.(c) Tang, Y.Z.; Wang, G.X.; Ye, Q.; Xiong, R.G.; Yuan, R.X.Heterometallic tetrazole coordination polymer formed through 2 + 3 cycloaddition reaction between inorganic complexes in the presence of Lewis acid.Cryst.Growth Des.2007, 7, 2382-2386.(d) Zhang, Y.; Wu, T.; Liu, R.; Dou, T.; Bu, X.H.; Feng, P.Y.Three-dimensional photoluminescent frameworks constructed from size-tunable CuI clusters.Cryst.Growth Des.2010, 10, 2047–2049.

(10) (a) Ma, Y.; Li, X.B.; Yi, X.C.; Jia, Q.X.; Gao, E.Q.; Liu, C.M.Novel three-dimensional metal-azide network induced by a bipyridine-based zwitterionic monocarboxylate ligand: structures and magnetism.Inorg.Chem.2010, 49, 8092-8098.(b) Wang, Y.Q.; Jia, Q.X.; Wang, K.; Cheng, A.L.; Gao, E.Q.Diverse manganese(II) coordination polymers with mixed azide and zwitterionic dicarboxylate ligands: structure and magnetic properties.Inorg.Chem.2010, 49, 1551-1560.

26 March 2015; accepted 12 May 2015 (CCDC 814427)

① Supported by the Key Project of Science and Technology Plan of Hunan Province (2012FJ2002), Science and Technology Committee of Hengyang (2013KG77), and the Construct Program of the Key Discipline in Hunan Province

② Corresponding author.E-mail: lihengfeng@gmail.com

10.14102/j.cnki.0254-5861.2011-0776