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Structural diversity and properties of four complexes with 4-acyl pyrazolone derivative
Polyhedron 55 (2013) 209–215
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Structural diversity and properties of four complexes with 4-acyl pyrazolone derivative He Li, Guan-Cheng Xu ⇑, Li Zhang, Ji-Xi Guo, Dian-Zeng Jia ⇑ Key Laboratory of Material and Technology for Clean Energy, Ministry of Education, Key Laboratory of Advanced Functional Materials, Autonomous Region, Institute of Applied Chemistry, Xinjiang University, Urumqi, 830046 Xinjiang, PR China
a r t i c l e
i n f o
Article history: Received 13 February 2013 Accepted 13 March 2013 Available online 21 March 2013 Keywords: Coordination polymer Pyrazolone derivative Crystal structure Fluorescent property Magnetism
a b s t r a c t Four new complexes {[Zn(HL)(H2O)(DMF)](NO3)}n (1), [Cd(HL)2]n (2), {[Mn(HL)2]CH3CN2H2O} (3) and {[Mn(L)(l2-EtOH)]}n (4) (H2L = N-(1-phenyl-3-methyl-4-benzal-pyrazolone-5)-nicotinic hydrazide) have been synthesized and characterized by elemental analyses, IR spectra, thermal analyses and single crystal X-ray diffraction. The structural analyses reveal that complexes 1, 2 and 3, formed by H2L with metal nitrate, have Zigzag chain, double-stranded chain and mononuclear structures, respectively, and the ligands adopt three different coordination modes in these complexes. While, complex 4, formed by H2L with manganese acetate, represents a 2D network structure with dinuclear units bridged by ethanol molecules. These result demonstrated that the metal atom and counteranion have certain influences on the structures of resulting complexes. In addition, the fluorescent properties of 1 and 2 and the magnetism of 4 were investigated. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction The rational design and assembly of metal–organic coordination polymers have received remarkable attention not only due to their fascinating structural diversities [1,2], but also for the potential discovery of novel functional materials, which may have applications in the areas including optical, electronic, magnetic fields, gas storage, ion-exchange and catalysis [3,4]. Up to now, though a great number of coordination polymers with various structures have been reported, it is still a long-term challenge to exactly predict and control the structures of resulting coordination polymers, because the structures of complexes are frequently influenced by various factors such as the metal atom, organic ligand, counteranion, the ratio of ligand to metal ion, reaction conditions, and so on [5,6]. Among them, the proper choice of organic ligand is the key factor governing the structure of coordination polymer. Thus, rational design and prepare of new multidentate ligand is one of the central tasks [7]. Pyrazolone-5, especially 4-acyl pyrazolone, form an important class of organic compounds and represent considerable scientific and applied interest in biological and analytical applications, metal extractants, dyes, etc [8,9]. On the other hand, the Schiff base derivatives of 4-acyl pyrazolone are less explored, even though these ligand are known to show appealing complexation properties [10]. In recent years, we have devoted our effort to the design and synthesis of 4-acyl pyrazolone Schiff base derivatives and the con⇑ Corresponding authors. Tel./fax: +86 991 8588883. E-mail address: [email protected] (D.-Z. Jia). 0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.poly.2013.03.024
struction and property of a series of transition and lanthanon metal complexes [11–13]. The results showed that 4-acyl pyrazolone derivatives have potential to form different types of complexes due to the multiple coordination sites and the tautomeric effect of enol form and keto form, and they can adopt different coordination modes to bond with metal atoms. Furthermore, some 4-acyl pyrazolone derivatives and their Cu(II) complexes possess interesting strong antibacterial activity [14]. In order to further investigate the coordination ability and complexation behavior of pyrazolonebased ligands, we extended our investigation to the syntheses of new 4-acyl pyrazolone derivatives and their metal complexes. This paper presents the syntheses, characterization and structural diversity of four new complexes, {[Zn(HL)(H2O)(DMF)](NO3)}n (1), [Cd(HL)2]n (2), {[Mn(HL)2]CH3CN2H2O} (3) and {[Mn(L)(l2EtOH)]}n (4). These complexes demonstrated Zigzag chain, double-stranded chain, mononuclear and 2D network structures. Meanwhile, the ligands adopt three kinds of coordination modes in these complexes. Furthermore, the influences of the metal atom and counteranion on the structures of the complexes were discussed. The fluorescent properties of 1 and 2 and the magnetism of 4 were investigated.
2. Experimental section 2.1. Materials and general physical measurements 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone, nicotinic hydrazide and other chemicals and solvents were analytical-grade
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C, 50.78; H, 4.43; N, 15.94. Found: C, 51.17; H, 4.22; N, 15.88%. IR(cm1, KBr): 3371(m), 3155(m), 2928(m), 1661(s), 1628(s), 1603(s), 1576(s), 1485(s), 1435(s), 1385(s), 1317(s), 1205(w), 1153(w), 1136(m), 1107(m), 1053(m), 1026(m), 920(m), 849(w), 766(m), 706(m), 705(m), 692(m), 660(m), 550(w).
commercial products and were directly used without further purification. The elemental analyses were made on FLASH EA 1112 Series NCHS-O analyzer. Melting point was measured with a TECH XT-6 melting point apparatus. IR spectra were recorded on a BRUKER VERTEX-70 spectrophotometer within 400–4000 cm1 with the samples prepared as pellets with KBr. TG curves of the complexes were recorded with a NETZSCH STA 449F3 thermal analyzer at the scanning rate of 10 K min1 in the flowing air atmosphere. The fluorescence spectra of ligand and complexes 1 and 2 were studied using Hitachi F-4500 fluorescence spectrophotometer with a Xe arc lamp as the light source at room temperature. Variable temperature magnetic data were obtained using a Quantum Design SQUID MPMS 7XL system. Background corrections for the sample holder assembly and diamagnetic components of the complexes were applied.
2.3.2. [Cd(HL)2]n (2) The procedure for preparation of complex 2 is similar to that of 1 except using Cd(NO3)24H2O (0.0925 g, 0.3 mmol) instead of Zn(NO3)26H2O. Yellow block crystals were obtained by slow evaporation of the resulting clear solution in 60% yield. Anal. Calcd. for C46H36N10O4Cd: C, 61.03; H, 4.01; N, 15.47. Found: C, 61.28; H, 4.15; N, 15.19%. IR(cm1, KBr): 3435(m), 3059(w), 2926(w), 1657(m), 1618(m), 1543(s), 1499(s), 1416(s), 1385(s), 1200(m), 1051(m), 1028(m), 1012(m), 839(m), 764(m), 731(m), 696(m), 630(w), 588(w).
2.2. Synthesis of the ligand H2L 2.3.3. {[Mn(HL)2]CH3CN2H2O} (3) A ethanol (6 mL) solution of Mn(NO3)24H2O (0.0753 g, 0.3 mmol) was added dropwise to a solution of ligand H2L (0.1192 g, 0.3 mmol) in acetonitrile (9 mL) and ethanol (3 mL) with stirring to give a clear solution. The reaction mixture was stirred for an hour and filtered. Yellow block crystals suitable for X-ray analysis were obtained by slow evaporation of the filtrate for two weeks in 57% yield. Anal. calc. for C48H43N11O6Mn: C, 62.34; H, 4.69; N, 16.66. Found: C, 62.43; H, 4.39; N, 16.52%. IR(cm1, KBr): 3365(m), 3269(m), 2968(m), 2848(m), 1668(m), 1603(s), 1566(s), 1523(m), 1473(s), 1435(s), 1396(m), 1369(s), 1333(m), 1151(m), 1049(m), 1028(m), 1012(m), 914(m), 845(w), 781(m), 760(m), 704(m), 658(w).
The 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (10 mmol) was dissolved in 40 mL of hot anhydrous ethanol, and a few drops of acetic acid were added as a catalyst. An ethanol solution of nicotinic hydrazide (10 mmol) was added dropwise with constant stirring. The yellow precipitate was then formed and the mixture was further refluxed for about 4 h. Upon cooling, the solid was collected by filtration, washed with ethanol and dried in air. The product was recrystallized from anhydrous ethanol as yellow block crystals in 84% yield. M.p.: 193–194 °C. Anal. calc. for C23H19N5O2: C, 69.50; H, 4.82; N, 17.63. Found: C, 69.26; H, 4.67; N, 17.83%. IR(cm1, KBr): 3437(m), 3130(w), 2980(m), 1649(s), 1593(s), 1537(s), 1518(s), 1499(s), 1418(m), 1385(s), 1146(m), 1055(m), 1026(w), 1011(m), 833(w), 773(m), 754(m), 706(m), 644(m), 576(m).
2.3.4. {[Mn(L)(l2-EtOH)]}n (4) The ethanol solution (10 mL) of Mn(OAc)24H2O (0.2451 g, 1 mmol) was added slowly to the ligand (0.3974 g, 1 mmol) in acetonitrile (20 mL). The brown clear solution was stirred for an hour and filtered. Brown block single crystals were obtained by slow evaporation of the filtrate at room temperature. Yield: 45%. Anal. calc. for C25H23N5O3Mn: C, 60.36; H, 4.86; N, 14.08. Found: C, 60.87; H, 4.70; N, 14.15%. IR(cm1, KBr): 3030(w), 2972(m), 2962(m), 2916(m), 2897(m), 2862(m), 1591(s), 1566(s), 1525(s), 1485(s), 1439(s), 1381(m), 1338(m), 1144(m), 1084(m), 1041(s), 1028(m), 924(m), 891(m), 842(w), 782(w), 756(m), 710(m), 690(m), 658(m), 603(w).
2.3. Preparation of the complexes and basic analytical data 2.3.1. {[Zn(HL)(H2O)(DMF)](NO3)}n (1) The ligand H2L (0.1192 g, 0.3 mmol) was dissolved in a mixed solvent of 9 mL acetonitrile and 3 mL N,N-dimethylformamide (DMF). To this solution was added dropwise an acetonitrile (6 mL) solution of Zn(NO3)26H2O (0.0892 g, 0.3 mmol) with constant stirring at room temperature. The mixture was filtered after stirring for ca. 1 h and the filtrate was allowed to evaporate slowly at ambient temperature. The light-yellow block crystals were obtained in 63% yield after several days. Anal. Calc. for C26H27N7O7Zn:
Table 1 Crystal and structure refinement data for 1–4. Complex
1
2
3
4
Formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (g cm3) Rint Goodness-of-fit (GOF) on F2 R1 [I > 2r(I)] wR2 [I > 2r(I)] Residuals (e Å3)
C26H27N7O7Zn 614.92 monoclinic P21/c 10.284(2) 12.043(2) 23.178(5) 90.00 93.45(3) 90.00 2865.3(1) 4 1.425 0.0347 1. 064 0.0337 0.0855 0.434, 0.345
C46H36N10O4Cd 905.26 monoclinic C2/c 22.996(5) 19.443(4) 13.889(3) 90.00 124.06(3) 90.00 5144.6(2) 4 1.169 0.0760 1.146 0.0562 0.1421 1.110, 0.718
C48H43N11O6Mn 924.87 orthorhombic P bca 14.806(3) 19.507(4) 31.462(6) 90.00 90.00 90.00 9087(3) 8 1.352 0.0683 1.006 0.0613 0.1541 0.466, 0.344
C25H23N5O3Mn 496.42 monoclinic P 21/c 11.565(5) 18.363(8) 11.474(5) 90.00 102.846(7) 90.00 2375.8(17) 4 1.388 0.0625 1.086 0.0610 0.1208 0.623, 0.361
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2.4. X-ray crystallography The crystallographic data of the complexes 1–3 were collected at 293(2) K on a Rigaku R-axis Spider diffractometer with graphite monochromatic Mo Ka radiation (k = 0.71073 Å). The structures were solved by direct methods using SHELXS-97 and were refined by full matrix least-squares methods using SHELXL-97 [15]. Anisotropic displacement parameters were refined for all non-hydrogen atoms. The data collection for 4 was performed on a Bruker SMART 1000 CCD diffractometer at 293 K. Semi-empirical absorption correction was applied using the SADABS program [16]. The structure was solved by direct method and refined by full-matrix least square on F2 using the SHELXTL-97 program. The structure of 2 possesses large solvent accessible volume, but the difference Fourier revealed no meaningful electron density that could be reliably assigned to the solvent. Thus, the SQUEEZE routine of PLATON was
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applied to the collected data and the structure of 2 was refined again [17]. In 4, the C12-C17 atoms of the phenyl group were disordered into two positions with site occupancy factors of 0.45 and 0.55, respectively. The details of the crystal parameters, data collection and refinements for complexes 1–4 are summarized in Table 1. Selected bond lengths and angles with their estimated standard deviations are listed in Table S1. Summary for hydrogen bond data are listed in Table S2. 3. Results and discussion 3.1. Crystal structural description 3.1.1. Crystal structure of {[Zn(HL)(H2O)(DMF)](NO3)}n (1) The crystal structure of 1 is exhibited in Fig. 1a with an atom numbering scheme. Its asymmetric unit contains one Zn(II) center,
Fig. 1. (a) Crystal structure of 1 with atom numbering scheme. (b) The infinite zigzag chain structure along b axis of 1. The coordinated solvent molecules are omitted for clarity. (c) The chains are further linked by hydrogen bonds to generate a 3D framework. The hydrogen bonds are indicated by the dashed lines.
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one ligand anion HL, one water, one N,N-dimethylformamide (DMF) molecules and one nitrate anion for charge balance. Each Zn(II) atom is coordinated by O1, N3 and O2 atoms from one ligand anion HL, one N5A atom (A: x + 1, y + 1/2, z + 3/2) from another ligand anion, and two O atoms (O3 and O4) from the coordinated DMF and water molecules to forms an octahedron geometry. The O1, O2, N3, N5A atoms consist of the equatorial plane with the least square plane deviation of 0.0400 Å, and the Zn(II) atom strays from the equatorial plane 0.1659 Å. The Zn–O/N bond distances in equatorial plane are in the range of 2.007(2) to 2.098(2) Å. The axial positions are occupied by O3 and O4 from the DMF and water molecules with the bond lengths of 2.323(2) and 2.069(2) Å. The angels of O1–Zn–O2, N3–Zn–N5A and O3–Zn–O4 are 164.83(6)°, 165.24(7)° and 175.38(7)°, respectively, which are deviated from the theoretical value of 180°. Therefore, the local coordination geometry around the Zn(II) center can be described as a distorted octahedron. On the other hand, the ligand acts as negative monovalent tetradentate linker to bond with two Zn(II) atoms, in which the O1, N3 and O2 atoms coordinate with Zn1(II) atom in meridional fashion, and the pyridyl N5 atom of the lateral chain bonds with another Zn1A atom. Such connection mode gives rise to zigzag chain structure of complex 1 with the Zn Zn separation of 7.253 Å along the b axis as illustrated in Fig. 1b. In complex 1, the chains are further linked by hydrogen bonds to form a 3D framework. The coordinated water molecules and nitrate anions play a vital role in the formation of this architecture. First, the adjacent chains are linked by O4–H4WA N2 hydrogen bonds between the coordinated water molecules and the ligands to form a 2D network (Fig. S1 in ESI). The distance of O4 N2 is 2.786(3) Å with the angle O–H N being 165.00°. In addition, the O atoms of the nitrate anions act as acceptors to form O–H O, N–H O and C–H O hydrogen bonds with water molecules and the ligands. These hydrogen bonds further link the 2D networks to generate 3D framework structure as illustrated in Fig. 1c. 3.1.2. Crystal structure of [Cd(HL)2]n (2) To investigate the influence of metal atom on the structure of the complex, the reactions of ligand H2L with Cd(NO3)26H2O or Mn(NO3)24H2O were carried out, and complexes 2 and 3, respectively, were obtained and their structures were determined by Xray crystallographic analyses. It is interesting to find that 2 features double-stranded chain structure, rather than Zigzag chain structure of 1, and 3 is a mononuclear compound. Meanwhile, the ligands in complexes 1–3 adopt different coordination modes. The results provide a nice example that metal atoms with different coordination features play an important role in determining the structures of the complexes. The crystal structure of 2 with atom numbering scheme is shown in Fig. 2a. Each Cd(II) atom is coordinated by N3, O2, N3A and O2A atoms from two ligand anions and two pyridyl N atoms (N5B and N5C) from the other two ligand anions (A: x + 1, y, z + 1/2. B: x + 1, y + 1, z + 1. C: x, y + 1, z 1/2.). The bond lengths of Cd1–O2, Cd1–N3 and Cd1–N5 are 2.337(3), 2.382(3) and 2.419(3) Å, respectively, and the coordination angles around Cd1(II) atom are varying from 67.33(1)° to 154.28(2)° (Table S1). Therefore, the local coordination geometry of the Cd(II) atom can be described as a serious distorted octahedral with N4O2 donor set. On the other hand, the ligand acts as a mononegative tridentate bridging linker to bond with two different Cd(II) atoms. It is noteworthy that only azomethine N3, enolic O2 and pyridyl N5 atoms take part in the coordination with metal atoms. While the O1 atom of the pyrazolone ring is free of coordination in complex 2. The unexpected coordination performance of H2L is different from that in complex 1 and it is also very rare in the reported complexes of pyrazolone derivatives. By closer inspection of the structure, two antiparallel ligand anions HL bridge two adjacent Cd(II) atoms
Fig. 2. (a) Crystal structure of 2 with the coordination environment around the Cd(II) center. (b) The double-stranded chain structure of 2 along the c axis. The phenyl groups on 1,4-positions of the ligands are omitted for clarity.
to form a 12-membered Cd2(HL)2 irregular ring with a Cd Cd separation of 7.459 Å and the adjacent rings shared one Cd(II) atom to generate a double-stranded chain structure extended along the c axis as shown in Fig. 2b. There are N–H O and C–H O hydrogen bonds in the chains, which help in stabilizing the structure (Fig. S2 in ESI). 3.1.3. Crystal structure of {[Mn(HL)2]CH3CN2H2O} (3) Complex 3 has a mononuclear structure and the asymmetric unit of 3 contains one Mn(II) atom, two ligand anion HL, one lattice acetonitrile and two lattice water molecules. The structure of the [Mn(HL)2] motif is shown in Fig. 3a with an atom numbering scheme. Each Mn(II) atom with octahedral geometry is coordinated by O1, N3, O2 atoms from one ligand anion and O3, N8, O4 atoms from another ligand anion to form a MnN2O4 coordination environment. The O3, O4, N3 and N8 atoms comprise the equatorial plane with the least square plane deviation of 0.0345 Å, and the Mn(II) atom strays from the equatorial plane 0.0237 Å, which indicates that the Mn(II) atom almost lies in the plane. The Mn–O3, Mn– O4, Mn–N3 and Mn–N8 bond lengths are 2.084(2), 2.191(2), 2.233(3) and 2.210(3) Å, respectively. The axial positions are occupied by O1 and O2 atoms with bond distances of 2.107(2) and 2.212(2) Å. The bond angels of O3–Mn–O4, N3–Mn–N8 and O1– Mn–O2 are 157.53(9)°, 176.93(1)° and 151.59(9)°, respectively, which are deviated from the theoretical value of 180°. Therefore, the local coordination geometry around the Mn(II) center can be described as highly distorted octahedron. On the other hand, the ligand H2L is in the deprotonated form by losing one hydrogen atom and functions as negative monovalent tridentate chelating agent coordinated to one Mn(II) atom in meridional fashion and generate a mononuclear complex. The
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Fig. 3. (a) Crystal structure of 3 with the coordination environment around the Mn(II) center. The phenyl groups on 1-position of pyrazolone rings are omitted for clarity. (b) The mononuclear units are connected by the intermolecular hydrogen bonds to form chain structure. The hydrogen bonds are indicated by the dashed lines.
remarkable feature of 3 is that the pyridyl N5 atom in the lateral chain was not coordinate with the Mn(II) atom. The crystal packing diagram of 3 is shown in Fig. 3b, the mononuclear units are linked by the intermolecular hydrogen bonds C44–H44 N4 to form a chain structure. Complexes 1–3 were synthesized by the reactions of ligand H2L with M(NO3)2nH2O (M = Zn, Cd, Mn) under the mixed solvent condition. But complexes 1–3 have different structures. Complex 1 has a Zigzag chain structure, while 2 and 3 feature double-stranded chain and mononuclear structure, respectively. In complexes 1–3, the ligands H2L act as mononegtive agent coordinated with the metal atoms. It is worth notice that ligands adopt three different coordination modes in 1–3. These results indicated that the metal atoms with different features have a significant effect on the formation and structures of the resulting complexes [18]. 3.1.4. Crystal structure of {[Mn(L)(l2-EtOH)]}n (4) In order to further investigate the influence of the anion on the structures of the complexes, reactions of the ligand H2L with M(OAc)2nH2O (M = Zn, Cd and Mn) were carried out. Although great effort was made, only complex {[Mn(L)(l2-EtOH)]}n (4) was obtained from H2L and Mn(OAc)24H2O. X-ray crystallographic analysis indicates that complex 4 has a 2D network structure, rather than a mononuclear structure as observed in 3. The results showed that the anions may have influence on the structures of the resulting complexes [19]. The crystal structure of 4 is shown in Fig. 4a with atom numbering scheme. The asymmetric unit contains one crystallographically independent Mn(II) center, one ligand anion L2 and one l2bridged ethanol molecule. It is interesting that two Mn(II) atoms (Mn1 and Mn1A) are bridged by two l2-O atoms of the ethanol molecules and form a dinuclear unit. Each Mn1(II) is hexa-coordi-
Fig. 4. (a) Crystal structure of 4 with atom numbering scheme. The C12–C17 atoms of the phenyl group at the 3-position were disordered into two positions with site occupancy factors of 0.45 and 0.55, respectively. (b) The 2D network structure of 4.
nated by O1, N3 and O2 atoms from one ligand anion L2, one N5B atom from another ligand anion, and two O atoms (O3 and O3A) from two bridging ethanol molecules to form an octahedron geometry with N4O2 donor sets (A: x + 1, y + 2, z. B: x, y + 3/2, z 1/2.). The O1, O2, N3 and O3A atoms consist of the equatorial plane with the least square plane deviation of 0.1094 Å, and the Mn1(II) ion strays from the equatorial plane 0.0251 Å, which indicates that the Mn1(II) atom nearly lies in the equatorial plane. The axial positions are occupied by O3 and N5B atoms with the bond distances of 2.208(2) and 2.398(3) Å. The bond distances of Mn1–O1, Mn1–O2, Mn1–N3 and Mn1–O3A in the equatorial plane are 1.916(3), 1.925(3), 1.990(3), 1.873(2) Å, respectively. It is obvious that the axial bond distances are longer than the bond distances of the equatorial plane, The bond angels of O1–Mn1–O2, N3–Mn1–O3A and O3–Mn1–N5B are 167.94(1)°, 171.77(1)° and 176.84(1)°, respectively, which are deviated from the theoretical value of 180°. All these observations implied that the geometry around the Mn1(II) atom in 4 should be an elongated distorted octahedron.
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In the dinuclear unit, two Mn(II) atoms are bridged by two l2-O atoms (O3 and O3A) from ethanol molecules to define a planar centrosymmetric parallelogram, in which the side lengths are 2.208(2) and 1.873(2) Å. The bond angles of Mn1–O3–Mn1A and O3A– Mn1–O3 are 98.12° and 81.88°. The Mn Mn intermetallic distance is 3.091 Å. In addition, the ligand H2L is in the deprotonated form by losing two hydrogen atoms and functions as negative bivalent tetradentate coordination unit to bridge two dinuclear units and give rise to a 2D network structure as indicated in Fig. 4b. In comparison, the structure of 4 is different from 3. Firstly, the solvent ethanol molecule acts as bridging co-ligand and connects two Mn(II) atoms to form dinuclear unit in 4. While in 3, the solvent ethanol molecule did not take part in the coordination. Furthermore, in 4, the ligand functions as negative bivalent tetradentate unit to bond with two octahedral Mn(II) atoms. But in 3, the ligand acts as negative monovalent tridentate unit coordinated with one Mn(II) atom. These results indicated that the anions have a certain effect on coordination mode of the ligands and structures of the resulting complexes. 3.2. Thermal analyses To estimate the stability of the complexes, thermogravimetric measurements for complexes 1–4 were carried out and the results were shown in Fig. S3 in ESI. The TG curve of 1 shows a weight loss of 15.96% from 84 to 156 °C, corresponding to the removal of coordinated water and DMF molecules of each formula unit (Calc.: 14.82%). Then the decomposition of the ligand and nitrate anion was followed. Weight constancy is attained at around 490 °C. The end product, estimated as ZnO, has an observed mass of 14.52% compared with the calculated value of 13.24%. Complex 2 exhibits a continuous weight loss in the temperature range of 115–640 °C. For complex 3, the first weight loss (8.38%) in the range of 63– 150 °C corresponds to the departure of one lattice acetonitrile and two water molecules. The weight loss is consistent with the calculated value (8.33%). Then, no marked weight loss is observed until 260 °C. After that temperature, the decomposition of the ligand anions was followed in the temperature range of 260– 460 °C. The observed mass loss (82.21%) coincides with the calculated value (82.70%). The final residue is qualitatively proved to be Mn2O3, the observed mass of 9.14% as against the calculated value of 8.53%. Compared with 1–3, complex 4 shows more better thermal stability. No weight loss is observed from room temperature to 240 °C. After that temperature, the compound begins to decompose following a process of continuous weight loss of the coordinated ethanol molecule and ligand anion. The observed mass loss is 84.27%, which is consistent with the theoretical value of 84.10%. The decomposition completes at 455 °C and the end product, estimated as Mn2O3, has the observed mass of 15.73% as against the calculated value of 15.90%. 3.3. Fluorescent properties Metal–organic coordination polymers with d10 metal atom and organic ligand are promising candidates for photoactive materials with potential applications [20]. Therefore, the solid-state fluorescent spectra of the free ligand H2L, complexes 1 and 2 were recorded at room temperature, as shown in Fig. S4. The emission spectra of the free ligand H2L and 2 both display broad band at ca. 404 nm upon excitation at 251 nm, which may due to the p⁄– p or p⁄–n electronic transitions, since the ligand cation of 2 has the similar structure with that of the free ligand (Fig. S5). While 1 exhibits intense fluorescence emission band at ca. 506 nm upon excitation at 434 nm. The emission of 1 is neither metal-to-ligand charge transfer (MLCT) nor ligand-to-metal transfer (LMCT) since
the Zn(II) ion is difficult to oxidize or reduce due to its d10 configuration [21]. Thus, it can be ascribed to the intraligand transitions. Furthermore, Compared with the luminescence of ligand, 1 results in much higher emission energy and a large red shift of 102 nm, which may be attributed to the coordination of Zn(II) atom to the ligand. The incorporation of Zn(II) effectively increases the conformational rigidity of the ligand and reduces the nonradiative decay of the intraligand excited state [22]. The good fluorescence efficiency indicated that 1 may be a good candidate for fluorescent materials. 3.4. Magnetic property The temperature variable magnetic susceptibility of complex 4 was measured in the range of 2–300 K under 2 kOe applied field as shown in Fig. S6. At 300 K, vMT is 8.84 cm3 mol1 K, which is close to the expected spin-only value of 8.75 cm3 mol1 K for two Mn(II) ions with S = 5/2. The magnetic susceptibility data in the range of 20–300 K obey the Curie–Weiss law, vM = C/(T h), with Curie constant C = 9.17 cm3 mol1 K and negative Weiss constants h of 9.04 K, which indicates the antiferromagnetic interaction between Mn(II) ions. The magnetic susceptibility vM increases as the temperature decreases and reaches a maximum of 0.296 cm3 mol1 at 14.0 K and then sharply goes down, suggesting the presence of possible antiferromagnetic ordering in this compound (Fig. S7). The Neel temperature, TN, was determined from the peak of d(vMT)/dT at 9.0 K (inset of Fig. S7) [23]. The ratios of TN/T(vM,max) = 0.643 do show the low-dimensional antiferromagnetic ordering character [24]. Taking into account the two-dimensional character of the complex 4, the 2-D square lattice can be treated as alternating uniform [MnIIMnII] dimmers with the exchange constant J and interdimmer interactions zJ0 . And the magnetic susceptibility data was fitted by means of the analytical expression derived by Curély for an infinite 2D square lattice composed of the dimmer Mn2 (S = 5/2) isotropically coupled [25]. The molar magnetic susceptibility of the dimmer [26] can be expressed as given in Eq. (1), and the molar magnetic susceptibility of the dimmer is written as in Eq. (2). Then the magnetic susceptibility of the 2D compound is as shown in Eq. (3), in which u = coth(JdSd(Sd + 1)/kT) kT/JdSd(Sd + 1). The best fitting in the temperature range of 50–300 K gives J = 1.67 cm1, P zJ0 = 0.03 cm1, g = 2.02 with R = 9.96 104 {R = [(vMT)obs 2 P 2 (vMT)calc] / (vMT)obs }. The negative value of exchange coupling through the oxygen bridges further suggests antiferromagnetic interaction in the Mn(II) dimmer.
vdimer ¼
Ng 2 b2 3kT 6 e2J=kT þ 5e6J=kT þ 14e12J=kT þ 30e20J=kT þ 55e30J=kT 1 þ 3e2J=kT þ 5e6J=kT þ 7e12J=kT þ 9e20J=kT þ 11e30J=kT
ð1Þ
Ng 2 b2 Sd ðSd þ 1Þ 3kT 6 e2J=kT þ 5e6J=kT þ 14e12J=kT þ 30e20J=kT þ 55e30J=kT ð2Þ Sd ðSd þ 1Þ ¼ 1 þ 3e2J=kT þ 5e6J=kT þ 7e12J=kT þ 9e20J=kT þ 11e30J=kT
vd ¼
v¼
Ng 2 b2 ð1 þ uÞ2 Sd ðSd þ 1Þ 3kT ð1 uÞ2
ð3Þ
4. Conclusions In summary, four complexes with multidentate 4-acyl pyrazolone Schiff-base derivative have been prepared and structurally characterized. The different structures of these complexes
H. Li et al. / Polyhedron 55 (2013) 209–215
demonstrated that the metal atoms and counter anions have certain influences on the formation and structures of the complexes. And the multidentate ligand can adopt three different kinds of coordination modes to bond with the metal atoms. Furthermore, the fluorescent properties of 1 and 2 and the magnetism of 4 are investigated. Acknowledgments This work was supported by the National Science Foundation of China (No. 21161019), the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China (No. 2011211B01), and Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (IRT1081). Appendix A. Supplementary data CCDC reference numbers 917283–917286 contain the supplementary crystallographic data for complexes 1–4, respectively. These data can be obtained free of charge via http://www.ccdc. cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.poly.2013.03.024. References [1] (a) W.L. Leong, J.J. Vittal, Chem. Rev. 111 (2011) 688; (b) M. Fujita, M. Tominaga, A. Hori, B. Therrien, Acc. Chem. Res. 38 (2005) 369; (c) N. Stock, S. Biswas, Chem. Rev. 112 (2012) 933; (d) Q.R. Fang, G.S. Zhu, Z. Jin, Y.Y. Ji, J.W. Ye, M. Xue, H. Yang, Y. Wang, S.L. Qiu, Angew. Chem., Int. Ed. 46 (2007) 6638. [2] (a) V.N. Vukotic, S.J. Loeb, Chem. Soc. Rev. 41 (2012) 5896; (b) A.Y. Robin, K.M. Fromm, Coord. Chem. Rev. 250 (2006) 2127; (c) D.J. Tranchemontagne, J.L. Mendoza-Cortés, M. O’Keeffe, O.M. Yaghi, Chem. Soc. Rev. 38 (2009) 1257. [3] (a) Y.J. Cui, Y.F. Yue, G.D. Qian, B.L. Chen, Chem. Rev. 112 (2012) 1126; (b) O.K. Farha, J.T. Hupp, Acc. Chem. Res. 43 (2010) 1166; (c) D.F. Weng, Z.M. Wang, S. Gao, Chem. Soc. Rev. 40 (2011) 3157; (d) J.R. Li, R.J. Kuppler, H.C. Zhou, Chem. Soc. Rev. 38 (2009) 1477. [4] (a) J. Liu, P.K. Thallapally, B.P. McGrail, D.R. Brown, J. Liu, Chem. Soc. Rev. 41 (2012) 2308; (b) M.P. Suh, J.J. Park, T.K. Prasad, D.W. Lim, Chem. Rev. 112 (2012) 782; (c) Z.B. Ma, B. Moulton, Coord. Chem. Rev. 255 (2011) 1623; (d) C. Wang, Z.G. Xie, K.E. deKrafft, W.B. Lin, J. Am. Chem. Soc. 133 (2011) 13445. [5] (a) Y.B. Dong, Y.Y. Jiang, J. Li, J.P. Ma, F.L. Liu, B. Tang, R.Q. Huang, S.R. Batten, J. Am. Chem. Soc. 129 (2007) 4520; (b) P.M. Forster, A.R. Burbank, C. Livage, G. Ferey, A.K. Cheethan, Chem. Commun. (2004) 368; (c) G.Q. Zhang, G.Q. Yang, J.S. Ma, Cryst. Growth Des. 6 (2006) 1897; (d) S.T. Wu, L.S. Long, R.B. Huang, L.S. Zheng, Cryst. Growth Des. 7 (2007) 1746. [6] (a) L. Lisnard, L. Chamoreau, Y.L. Li, Y. Journaux, Cryst. Growth Des. 12 (2012) 4955; (b) G.C. Xu, Q. Hua, T. Okamura, Z.S. Bai, Y.J. Ding, Y.Q. Huang, G.X. Liu, W.Y. Sun, N. Ueyama, CrystEngComm 11 (2009) 261; (c) J. Liu, Y.X. Tan, J. Zhang, Cryst. Growth Des. 12 (2012) 5164; (d) C.P. Li, M. Du, Chem. Commun. 47 (2011) 5958.
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Structural diversity and properties of four complexes with 4-acyl pyrazolone derivative He Li, Guan-Cheng Xu ⇑, Li Zhang, Ji-Xi Guo, Dian-Zeng Jia ⇑ Key Laboratory of Material and Technology for Clean Energy, Ministry of Education, Key Laboratory of Advanced Functional Materials, Autonomous Region, Institute of Applied Chemistry, Xinjiang University, Urumqi, 830046 Xinjiang, PR China
a r t i c l e
i n f o
Article history: Received 13 February 2013 Accepted 13 March 2013 Available online 21 March 2013 Keywords: Coordination polymer Pyrazolone derivative Crystal structure Fluorescent property Magnetism
a b s t r a c t Four new complexes {[Zn(HL)(H2O)(DMF)](NO3)}n (1), [Cd(HL)2]n (2), {[Mn(HL)2]CH3CN2H2O} (3) and {[Mn(L)(l2-EtOH)]}n (4) (H2L = N-(1-phenyl-3-methyl-4-benzal-pyrazolone-5)-nicotinic hydrazide) have been synthesized and characterized by elemental analyses, IR spectra, thermal analyses and single crystal X-ray diffraction. The structural analyses reveal that complexes 1, 2 and 3, formed by H2L with metal nitrate, have Zigzag chain, double-stranded chain and mononuclear structures, respectively, and the ligands adopt three different coordination modes in these complexes. While, complex 4, formed by H2L with manganese acetate, represents a 2D network structure with dinuclear units bridged by ethanol molecules. These result demonstrated that the metal atom and counteranion have certain influences on the structures of resulting complexes. In addition, the fluorescent properties of 1 and 2 and the magnetism of 4 were investigated. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction The rational design and assembly of metal–organic coordination polymers have received remarkable attention not only due to their fascinating structural diversities [1,2], but also for the potential discovery of novel functional materials, which may have applications in the areas including optical, electronic, magnetic fields, gas storage, ion-exchange and catalysis [3,4]. Up to now, though a great number of coordination polymers with various structures have been reported, it is still a long-term challenge to exactly predict and control the structures of resulting coordination polymers, because the structures of complexes are frequently influenced by various factors such as the metal atom, organic ligand, counteranion, the ratio of ligand to metal ion, reaction conditions, and so on [5,6]. Among them, the proper choice of organic ligand is the key factor governing the structure of coordination polymer. Thus, rational design and prepare of new multidentate ligand is one of the central tasks [7]. Pyrazolone-5, especially 4-acyl pyrazolone, form an important class of organic compounds and represent considerable scientific and applied interest in biological and analytical applications, metal extractants, dyes, etc [8,9]. On the other hand, the Schiff base derivatives of 4-acyl pyrazolone are less explored, even though these ligand are known to show appealing complexation properties [10]. In recent years, we have devoted our effort to the design and synthesis of 4-acyl pyrazolone Schiff base derivatives and the con⇑ Corresponding authors. Tel./fax: +86 991 8588883. E-mail address: [email protected] (D.-Z. Jia). 0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.poly.2013.03.024
struction and property of a series of transition and lanthanon metal complexes [11–13]. The results showed that 4-acyl pyrazolone derivatives have potential to form different types of complexes due to the multiple coordination sites and the tautomeric effect of enol form and keto form, and they can adopt different coordination modes to bond with metal atoms. Furthermore, some 4-acyl pyrazolone derivatives and their Cu(II) complexes possess interesting strong antibacterial activity [14]. In order to further investigate the coordination ability and complexation behavior of pyrazolonebased ligands, we extended our investigation to the syntheses of new 4-acyl pyrazolone derivatives and their metal complexes. This paper presents the syntheses, characterization and structural diversity of four new complexes, {[Zn(HL)(H2O)(DMF)](NO3)}n (1), [Cd(HL)2]n (2), {[Mn(HL)2]CH3CN2H2O} (3) and {[Mn(L)(l2EtOH)]}n (4). These complexes demonstrated Zigzag chain, double-stranded chain, mononuclear and 2D network structures. Meanwhile, the ligands adopt three kinds of coordination modes in these complexes. Furthermore, the influences of the metal atom and counteranion on the structures of the complexes were discussed. The fluorescent properties of 1 and 2 and the magnetism of 4 were investigated.
2. Experimental section 2.1. Materials and general physical measurements 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone, nicotinic hydrazide and other chemicals and solvents were analytical-grade
210
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C, 50.78; H, 4.43; N, 15.94. Found: C, 51.17; H, 4.22; N, 15.88%. IR(cm1, KBr): 3371(m), 3155(m), 2928(m), 1661(s), 1628(s), 1603(s), 1576(s), 1485(s), 1435(s), 1385(s), 1317(s), 1205(w), 1153(w), 1136(m), 1107(m), 1053(m), 1026(m), 920(m), 849(w), 766(m), 706(m), 705(m), 692(m), 660(m), 550(w).
commercial products and were directly used without further purification. The elemental analyses were made on FLASH EA 1112 Series NCHS-O analyzer. Melting point was measured with a TECH XT-6 melting point apparatus. IR spectra were recorded on a BRUKER VERTEX-70 spectrophotometer within 400–4000 cm1 with the samples prepared as pellets with KBr. TG curves of the complexes were recorded with a NETZSCH STA 449F3 thermal analyzer at the scanning rate of 10 K min1 in the flowing air atmosphere. The fluorescence spectra of ligand and complexes 1 and 2 were studied using Hitachi F-4500 fluorescence spectrophotometer with a Xe arc lamp as the light source at room temperature. Variable temperature magnetic data were obtained using a Quantum Design SQUID MPMS 7XL system. Background corrections for the sample holder assembly and diamagnetic components of the complexes were applied.
2.3.2. [Cd(HL)2]n (2) The procedure for preparation of complex 2 is similar to that of 1 except using Cd(NO3)24H2O (0.0925 g, 0.3 mmol) instead of Zn(NO3)26H2O. Yellow block crystals were obtained by slow evaporation of the resulting clear solution in 60% yield. Anal. Calcd. for C46H36N10O4Cd: C, 61.03; H, 4.01; N, 15.47. Found: C, 61.28; H, 4.15; N, 15.19%. IR(cm1, KBr): 3435(m), 3059(w), 2926(w), 1657(m), 1618(m), 1543(s), 1499(s), 1416(s), 1385(s), 1200(m), 1051(m), 1028(m), 1012(m), 839(m), 764(m), 731(m), 696(m), 630(w), 588(w).
2.2. Synthesis of the ligand H2L 2.3.3. {[Mn(HL)2]CH3CN2H2O} (3) A ethanol (6 mL) solution of Mn(NO3)24H2O (0.0753 g, 0.3 mmol) was added dropwise to a solution of ligand H2L (0.1192 g, 0.3 mmol) in acetonitrile (9 mL) and ethanol (3 mL) with stirring to give a clear solution. The reaction mixture was stirred for an hour and filtered. Yellow block crystals suitable for X-ray analysis were obtained by slow evaporation of the filtrate for two weeks in 57% yield. Anal. calc. for C48H43N11O6Mn: C, 62.34; H, 4.69; N, 16.66. Found: C, 62.43; H, 4.39; N, 16.52%. IR(cm1, KBr): 3365(m), 3269(m), 2968(m), 2848(m), 1668(m), 1603(s), 1566(s), 1523(m), 1473(s), 1435(s), 1396(m), 1369(s), 1333(m), 1151(m), 1049(m), 1028(m), 1012(m), 914(m), 845(w), 781(m), 760(m), 704(m), 658(w).
The 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (10 mmol) was dissolved in 40 mL of hot anhydrous ethanol, and a few drops of acetic acid were added as a catalyst. An ethanol solution of nicotinic hydrazide (10 mmol) was added dropwise with constant stirring. The yellow precipitate was then formed and the mixture was further refluxed for about 4 h. Upon cooling, the solid was collected by filtration, washed with ethanol and dried in air. The product was recrystallized from anhydrous ethanol as yellow block crystals in 84% yield. M.p.: 193–194 °C. Anal. calc. for C23H19N5O2: C, 69.50; H, 4.82; N, 17.63. Found: C, 69.26; H, 4.67; N, 17.83%. IR(cm1, KBr): 3437(m), 3130(w), 2980(m), 1649(s), 1593(s), 1537(s), 1518(s), 1499(s), 1418(m), 1385(s), 1146(m), 1055(m), 1026(w), 1011(m), 833(w), 773(m), 754(m), 706(m), 644(m), 576(m).
2.3.4. {[Mn(L)(l2-EtOH)]}n (4) The ethanol solution (10 mL) of Mn(OAc)24H2O (0.2451 g, 1 mmol) was added slowly to the ligand (0.3974 g, 1 mmol) in acetonitrile (20 mL). The brown clear solution was stirred for an hour and filtered. Brown block single crystals were obtained by slow evaporation of the filtrate at room temperature. Yield: 45%. Anal. calc. for C25H23N5O3Mn: C, 60.36; H, 4.86; N, 14.08. Found: C, 60.87; H, 4.70; N, 14.15%. IR(cm1, KBr): 3030(w), 2972(m), 2962(m), 2916(m), 2897(m), 2862(m), 1591(s), 1566(s), 1525(s), 1485(s), 1439(s), 1381(m), 1338(m), 1144(m), 1084(m), 1041(s), 1028(m), 924(m), 891(m), 842(w), 782(w), 756(m), 710(m), 690(m), 658(m), 603(w).
2.3. Preparation of the complexes and basic analytical data 2.3.1. {[Zn(HL)(H2O)(DMF)](NO3)}n (1) The ligand H2L (0.1192 g, 0.3 mmol) was dissolved in a mixed solvent of 9 mL acetonitrile and 3 mL N,N-dimethylformamide (DMF). To this solution was added dropwise an acetonitrile (6 mL) solution of Zn(NO3)26H2O (0.0892 g, 0.3 mmol) with constant stirring at room temperature. The mixture was filtered after stirring for ca. 1 h and the filtrate was allowed to evaporate slowly at ambient temperature. The light-yellow block crystals were obtained in 63% yield after several days. Anal. Calc. for C26H27N7O7Zn:
Table 1 Crystal and structure refinement data for 1–4. Complex
1
2
3
4
Formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (g cm3) Rint Goodness-of-fit (GOF) on F2 R1 [I > 2r(I)] wR2 [I > 2r(I)] Residuals (e Å3)
C26H27N7O7Zn 614.92 monoclinic P21/c 10.284(2) 12.043(2) 23.178(5) 90.00 93.45(3) 90.00 2865.3(1) 4 1.425 0.0347 1. 064 0.0337 0.0855 0.434, 0.345
C46H36N10O4Cd 905.26 monoclinic C2/c 22.996(5) 19.443(4) 13.889(3) 90.00 124.06(3) 90.00 5144.6(2) 4 1.169 0.0760 1.146 0.0562 0.1421 1.110, 0.718
C48H43N11O6Mn 924.87 orthorhombic P bca 14.806(3) 19.507(4) 31.462(6) 90.00 90.00 90.00 9087(3) 8 1.352 0.0683 1.006 0.0613 0.1541 0.466, 0.344
C25H23N5O3Mn 496.42 monoclinic P 21/c 11.565(5) 18.363(8) 11.474(5) 90.00 102.846(7) 90.00 2375.8(17) 4 1.388 0.0625 1.086 0.0610 0.1208 0.623, 0.361
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2.4. X-ray crystallography The crystallographic data of the complexes 1–3 were collected at 293(2) K on a Rigaku R-axis Spider diffractometer with graphite monochromatic Mo Ka radiation (k = 0.71073 Å). The structures were solved by direct methods using SHELXS-97 and were refined by full matrix least-squares methods using SHELXL-97 [15]. Anisotropic displacement parameters were refined for all non-hydrogen atoms. The data collection for 4 was performed on a Bruker SMART 1000 CCD diffractometer at 293 K. Semi-empirical absorption correction was applied using the SADABS program [16]. The structure was solved by direct method and refined by full-matrix least square on F2 using the SHELXTL-97 program. The structure of 2 possesses large solvent accessible volume, but the difference Fourier revealed no meaningful electron density that could be reliably assigned to the solvent. Thus, the SQUEEZE routine of PLATON was
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applied to the collected data and the structure of 2 was refined again [17]. In 4, the C12-C17 atoms of the phenyl group were disordered into two positions with site occupancy factors of 0.45 and 0.55, respectively. The details of the crystal parameters, data collection and refinements for complexes 1–4 are summarized in Table 1. Selected bond lengths and angles with their estimated standard deviations are listed in Table S1. Summary for hydrogen bond data are listed in Table S2. 3. Results and discussion 3.1. Crystal structural description 3.1.1. Crystal structure of {[Zn(HL)(H2O)(DMF)](NO3)}n (1) The crystal structure of 1 is exhibited in Fig. 1a with an atom numbering scheme. Its asymmetric unit contains one Zn(II) center,
Fig. 1. (a) Crystal structure of 1 with atom numbering scheme. (b) The infinite zigzag chain structure along b axis of 1. The coordinated solvent molecules are omitted for clarity. (c) The chains are further linked by hydrogen bonds to generate a 3D framework. The hydrogen bonds are indicated by the dashed lines.
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one ligand anion HL, one water, one N,N-dimethylformamide (DMF) molecules and one nitrate anion for charge balance. Each Zn(II) atom is coordinated by O1, N3 and O2 atoms from one ligand anion HL, one N5A atom (A: x + 1, y + 1/2, z + 3/2) from another ligand anion, and two O atoms (O3 and O4) from the coordinated DMF and water molecules to forms an octahedron geometry. The O1, O2, N3, N5A atoms consist of the equatorial plane with the least square plane deviation of 0.0400 Å, and the Zn(II) atom strays from the equatorial plane 0.1659 Å. The Zn–O/N bond distances in equatorial plane are in the range of 2.007(2) to 2.098(2) Å. The axial positions are occupied by O3 and O4 from the DMF and water molecules with the bond lengths of 2.323(2) and 2.069(2) Å. The angels of O1–Zn–O2, N3–Zn–N5A and O3–Zn–O4 are 164.83(6)°, 165.24(7)° and 175.38(7)°, respectively, which are deviated from the theoretical value of 180°. Therefore, the local coordination geometry around the Zn(II) center can be described as a distorted octahedron. On the other hand, the ligand acts as negative monovalent tetradentate linker to bond with two Zn(II) atoms, in which the O1, N3 and O2 atoms coordinate with Zn1(II) atom in meridional fashion, and the pyridyl N5 atom of the lateral chain bonds with another Zn1A atom. Such connection mode gives rise to zigzag chain structure of complex 1 with the Zn Zn separation of 7.253 Å along the b axis as illustrated in Fig. 1b. In complex 1, the chains are further linked by hydrogen bonds to form a 3D framework. The coordinated water molecules and nitrate anions play a vital role in the formation of this architecture. First, the adjacent chains are linked by O4–H4WA N2 hydrogen bonds between the coordinated water molecules and the ligands to form a 2D network (Fig. S1 in ESI). The distance of O4 N2 is 2.786(3) Å with the angle O–H N being 165.00°. In addition, the O atoms of the nitrate anions act as acceptors to form O–H O, N–H O and C–H O hydrogen bonds with water molecules and the ligands. These hydrogen bonds further link the 2D networks to generate 3D framework structure as illustrated in Fig. 1c. 3.1.2. Crystal structure of [Cd(HL)2]n (2) To investigate the influence of metal atom on the structure of the complex, the reactions of ligand H2L with Cd(NO3)26H2O or Mn(NO3)24H2O were carried out, and complexes 2 and 3, respectively, were obtained and their structures were determined by Xray crystallographic analyses. It is interesting to find that 2 features double-stranded chain structure, rather than Zigzag chain structure of 1, and 3 is a mononuclear compound. Meanwhile, the ligands in complexes 1–3 adopt different coordination modes. The results provide a nice example that metal atoms with different coordination features play an important role in determining the structures of the complexes. The crystal structure of 2 with atom numbering scheme is shown in Fig. 2a. Each Cd(II) atom is coordinated by N3, O2, N3A and O2A atoms from two ligand anions and two pyridyl N atoms (N5B and N5C) from the other two ligand anions (A: x + 1, y, z + 1/2. B: x + 1, y + 1, z + 1. C: x, y + 1, z 1/2.). The bond lengths of Cd1–O2, Cd1–N3 and Cd1–N5 are 2.337(3), 2.382(3) and 2.419(3) Å, respectively, and the coordination angles around Cd1(II) atom are varying from 67.33(1)° to 154.28(2)° (Table S1). Therefore, the local coordination geometry of the Cd(II) atom can be described as a serious distorted octahedral with N4O2 donor set. On the other hand, the ligand acts as a mononegative tridentate bridging linker to bond with two different Cd(II) atoms. It is noteworthy that only azomethine N3, enolic O2 and pyridyl N5 atoms take part in the coordination with metal atoms. While the O1 atom of the pyrazolone ring is free of coordination in complex 2. The unexpected coordination performance of H2L is different from that in complex 1 and it is also very rare in the reported complexes of pyrazolone derivatives. By closer inspection of the structure, two antiparallel ligand anions HL bridge two adjacent Cd(II) atoms
Fig. 2. (a) Crystal structure of 2 with the coordination environment around the Cd(II) center. (b) The double-stranded chain structure of 2 along the c axis. The phenyl groups on 1,4-positions of the ligands are omitted for clarity.
to form a 12-membered Cd2(HL)2 irregular ring with a Cd Cd separation of 7.459 Å and the adjacent rings shared one Cd(II) atom to generate a double-stranded chain structure extended along the c axis as shown in Fig. 2b. There are N–H O and C–H O hydrogen bonds in the chains, which help in stabilizing the structure (Fig. S2 in ESI). 3.1.3. Crystal structure of {[Mn(HL)2]CH3CN2H2O} (3) Complex 3 has a mononuclear structure and the asymmetric unit of 3 contains one Mn(II) atom, two ligand anion HL, one lattice acetonitrile and two lattice water molecules. The structure of the [Mn(HL)2] motif is shown in Fig. 3a with an atom numbering scheme. Each Mn(II) atom with octahedral geometry is coordinated by O1, N3, O2 atoms from one ligand anion and O3, N8, O4 atoms from another ligand anion to form a MnN2O4 coordination environment. The O3, O4, N3 and N8 atoms comprise the equatorial plane with the least square plane deviation of 0.0345 Å, and the Mn(II) atom strays from the equatorial plane 0.0237 Å, which indicates that the Mn(II) atom almost lies in the plane. The Mn–O3, Mn– O4, Mn–N3 and Mn–N8 bond lengths are 2.084(2), 2.191(2), 2.233(3) and 2.210(3) Å, respectively. The axial positions are occupied by O1 and O2 atoms with bond distances of 2.107(2) and 2.212(2) Å. The bond angels of O3–Mn–O4, N3–Mn–N8 and O1– Mn–O2 are 157.53(9)°, 176.93(1)° and 151.59(9)°, respectively, which are deviated from the theoretical value of 180°. Therefore, the local coordination geometry around the Mn(II) center can be described as highly distorted octahedron. On the other hand, the ligand H2L is in the deprotonated form by losing one hydrogen atom and functions as negative monovalent tridentate chelating agent coordinated to one Mn(II) atom in meridional fashion and generate a mononuclear complex. The
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Fig. 3. (a) Crystal structure of 3 with the coordination environment around the Mn(II) center. The phenyl groups on 1-position of pyrazolone rings are omitted for clarity. (b) The mononuclear units are connected by the intermolecular hydrogen bonds to form chain structure. The hydrogen bonds are indicated by the dashed lines.
remarkable feature of 3 is that the pyridyl N5 atom in the lateral chain was not coordinate with the Mn(II) atom. The crystal packing diagram of 3 is shown in Fig. 3b, the mononuclear units are linked by the intermolecular hydrogen bonds C44–H44 N4 to form a chain structure. Complexes 1–3 were synthesized by the reactions of ligand H2L with M(NO3)2nH2O (M = Zn, Cd, Mn) under the mixed solvent condition. But complexes 1–3 have different structures. Complex 1 has a Zigzag chain structure, while 2 and 3 feature double-stranded chain and mononuclear structure, respectively. In complexes 1–3, the ligands H2L act as mononegtive agent coordinated with the metal atoms. It is worth notice that ligands adopt three different coordination modes in 1–3. These results indicated that the metal atoms with different features have a significant effect on the formation and structures of the resulting complexes [18]. 3.1.4. Crystal structure of {[Mn(L)(l2-EtOH)]}n (4) In order to further investigate the influence of the anion on the structures of the complexes, reactions of the ligand H2L with M(OAc)2nH2O (M = Zn, Cd and Mn) were carried out. Although great effort was made, only complex {[Mn(L)(l2-EtOH)]}n (4) was obtained from H2L and Mn(OAc)24H2O. X-ray crystallographic analysis indicates that complex 4 has a 2D network structure, rather than a mononuclear structure as observed in 3. The results showed that the anions may have influence on the structures of the resulting complexes [19]. The crystal structure of 4 is shown in Fig. 4a with atom numbering scheme. The asymmetric unit contains one crystallographically independent Mn(II) center, one ligand anion L2 and one l2bridged ethanol molecule. It is interesting that two Mn(II) atoms (Mn1 and Mn1A) are bridged by two l2-O atoms of the ethanol molecules and form a dinuclear unit. Each Mn1(II) is hexa-coordi-
Fig. 4. (a) Crystal structure of 4 with atom numbering scheme. The C12–C17 atoms of the phenyl group at the 3-position were disordered into two positions with site occupancy factors of 0.45 and 0.55, respectively. (b) The 2D network structure of 4.
nated by O1, N3 and O2 atoms from one ligand anion L2, one N5B atom from another ligand anion, and two O atoms (O3 and O3A) from two bridging ethanol molecules to form an octahedron geometry with N4O2 donor sets (A: x + 1, y + 2, z. B: x, y + 3/2, z 1/2.). The O1, O2, N3 and O3A atoms consist of the equatorial plane with the least square plane deviation of 0.1094 Å, and the Mn1(II) ion strays from the equatorial plane 0.0251 Å, which indicates that the Mn1(II) atom nearly lies in the equatorial plane. The axial positions are occupied by O3 and N5B atoms with the bond distances of 2.208(2) and 2.398(3) Å. The bond distances of Mn1–O1, Mn1–O2, Mn1–N3 and Mn1–O3A in the equatorial plane are 1.916(3), 1.925(3), 1.990(3), 1.873(2) Å, respectively. It is obvious that the axial bond distances are longer than the bond distances of the equatorial plane, The bond angels of O1–Mn1–O2, N3–Mn1–O3A and O3–Mn1–N5B are 167.94(1)°, 171.77(1)° and 176.84(1)°, respectively, which are deviated from the theoretical value of 180°. All these observations implied that the geometry around the Mn1(II) atom in 4 should be an elongated distorted octahedron.
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In the dinuclear unit, two Mn(II) atoms are bridged by two l2-O atoms (O3 and O3A) from ethanol molecules to define a planar centrosymmetric parallelogram, in which the side lengths are 2.208(2) and 1.873(2) Å. The bond angles of Mn1–O3–Mn1A and O3A– Mn1–O3 are 98.12° and 81.88°. The Mn Mn intermetallic distance is 3.091 Å. In addition, the ligand H2L is in the deprotonated form by losing two hydrogen atoms and functions as negative bivalent tetradentate coordination unit to bridge two dinuclear units and give rise to a 2D network structure as indicated in Fig. 4b. In comparison, the structure of 4 is different from 3. Firstly, the solvent ethanol molecule acts as bridging co-ligand and connects two Mn(II) atoms to form dinuclear unit in 4. While in 3, the solvent ethanol molecule did not take part in the coordination. Furthermore, in 4, the ligand functions as negative bivalent tetradentate unit to bond with two octahedral Mn(II) atoms. But in 3, the ligand acts as negative monovalent tridentate unit coordinated with one Mn(II) atom. These results indicated that the anions have a certain effect on coordination mode of the ligands and structures of the resulting complexes. 3.2. Thermal analyses To estimate the stability of the complexes, thermogravimetric measurements for complexes 1–4 were carried out and the results were shown in Fig. S3 in ESI. The TG curve of 1 shows a weight loss of 15.96% from 84 to 156 °C, corresponding to the removal of coordinated water and DMF molecules of each formula unit (Calc.: 14.82%). Then the decomposition of the ligand and nitrate anion was followed. Weight constancy is attained at around 490 °C. The end product, estimated as ZnO, has an observed mass of 14.52% compared with the calculated value of 13.24%. Complex 2 exhibits a continuous weight loss in the temperature range of 115–640 °C. For complex 3, the first weight loss (8.38%) in the range of 63– 150 °C corresponds to the departure of one lattice acetonitrile and two water molecules. The weight loss is consistent with the calculated value (8.33%). Then, no marked weight loss is observed until 260 °C. After that temperature, the decomposition of the ligand anions was followed in the temperature range of 260– 460 °C. The observed mass loss (82.21%) coincides with the calculated value (82.70%). The final residue is qualitatively proved to be Mn2O3, the observed mass of 9.14% as against the calculated value of 8.53%. Compared with 1–3, complex 4 shows more better thermal stability. No weight loss is observed from room temperature to 240 °C. After that temperature, the compound begins to decompose following a process of continuous weight loss of the coordinated ethanol molecule and ligand anion. The observed mass loss is 84.27%, which is consistent with the theoretical value of 84.10%. The decomposition completes at 455 °C and the end product, estimated as Mn2O3, has the observed mass of 15.73% as against the calculated value of 15.90%. 3.3. Fluorescent properties Metal–organic coordination polymers with d10 metal atom and organic ligand are promising candidates for photoactive materials with potential applications [20]. Therefore, the solid-state fluorescent spectra of the free ligand H2L, complexes 1 and 2 were recorded at room temperature, as shown in Fig. S4. The emission spectra of the free ligand H2L and 2 both display broad band at ca. 404 nm upon excitation at 251 nm, which may due to the p⁄– p or p⁄–n electronic transitions, since the ligand cation of 2 has the similar structure with that of the free ligand (Fig. S5). While 1 exhibits intense fluorescence emission band at ca. 506 nm upon excitation at 434 nm. The emission of 1 is neither metal-to-ligand charge transfer (MLCT) nor ligand-to-metal transfer (LMCT) since
the Zn(II) ion is difficult to oxidize or reduce due to its d10 configuration [21]. Thus, it can be ascribed to the intraligand transitions. Furthermore, Compared with the luminescence of ligand, 1 results in much higher emission energy and a large red shift of 102 nm, which may be attributed to the coordination of Zn(II) atom to the ligand. The incorporation of Zn(II) effectively increases the conformational rigidity of the ligand and reduces the nonradiative decay of the intraligand excited state [22]. The good fluorescence efficiency indicated that 1 may be a good candidate for fluorescent materials. 3.4. Magnetic property The temperature variable magnetic susceptibility of complex 4 was measured in the range of 2–300 K under 2 kOe applied field as shown in Fig. S6. At 300 K, vMT is 8.84 cm3 mol1 K, which is close to the expected spin-only value of 8.75 cm3 mol1 K for two Mn(II) ions with S = 5/2. The magnetic susceptibility data in the range of 20–300 K obey the Curie–Weiss law, vM = C/(T h), with Curie constant C = 9.17 cm3 mol1 K and negative Weiss constants h of 9.04 K, which indicates the antiferromagnetic interaction between Mn(II) ions. The magnetic susceptibility vM increases as the temperature decreases and reaches a maximum of 0.296 cm3 mol1 at 14.0 K and then sharply goes down, suggesting the presence of possible antiferromagnetic ordering in this compound (Fig. S7). The Neel temperature, TN, was determined from the peak of d(vMT)/dT at 9.0 K (inset of Fig. S7) [23]. The ratios of TN/T(vM,max) = 0.643 do show the low-dimensional antiferromagnetic ordering character [24]. Taking into account the two-dimensional character of the complex 4, the 2-D square lattice can be treated as alternating uniform [MnIIMnII] dimmers with the exchange constant J and interdimmer interactions zJ0 . And the magnetic susceptibility data was fitted by means of the analytical expression derived by Curély for an infinite 2D square lattice composed of the dimmer Mn2 (S = 5/2) isotropically coupled [25]. The molar magnetic susceptibility of the dimmer [26] can be expressed as given in Eq. (1), and the molar magnetic susceptibility of the dimmer is written as in Eq. (2). Then the magnetic susceptibility of the 2D compound is as shown in Eq. (3), in which u = coth(JdSd(Sd + 1)/kT) kT/JdSd(Sd + 1). The best fitting in the temperature range of 50–300 K gives J = 1.67 cm1, P zJ0 = 0.03 cm1, g = 2.02 with R = 9.96 104 {R = [(vMT)obs 2 P 2 (vMT)calc] / (vMT)obs }. The negative value of exchange coupling through the oxygen bridges further suggests antiferromagnetic interaction in the Mn(II) dimmer.
vdimer ¼
Ng 2 b2 3kT 6 e2J=kT þ 5e6J=kT þ 14e12J=kT þ 30e20J=kT þ 55e30J=kT 1 þ 3e2J=kT þ 5e6J=kT þ 7e12J=kT þ 9e20J=kT þ 11e30J=kT
ð1Þ
Ng 2 b2 Sd ðSd þ 1Þ 3kT 6 e2J=kT þ 5e6J=kT þ 14e12J=kT þ 30e20J=kT þ 55e30J=kT ð2Þ Sd ðSd þ 1Þ ¼ 1 þ 3e2J=kT þ 5e6J=kT þ 7e12J=kT þ 9e20J=kT þ 11e30J=kT
vd ¼
v¼
Ng 2 b2 ð1 þ uÞ2 Sd ðSd þ 1Þ 3kT ð1 uÞ2
ð3Þ
4. Conclusions In summary, four complexes with multidentate 4-acyl pyrazolone Schiff-base derivative have been prepared and structurally characterized. The different structures of these complexes
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demonstrated that the metal atoms and counter anions have certain influences on the formation and structures of the complexes. And the multidentate ligand can adopt three different kinds of coordination modes to bond with the metal atoms. Furthermore, the fluorescent properties of 1 and 2 and the magnetism of 4 are investigated. Acknowledgments This work was supported by the National Science Foundation of China (No. 21161019), the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China (No. 2011211B01), and Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (IRT1081). Appendix A. Supplementary data CCDC reference numbers 917283–917286 contain the supplementary crystallographic data for complexes 1–4, respectively. These data can be obtained free of charge via http://www.ccdc. cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.poly.2013.03.024. References [1] (a) W.L. Leong, J.J. Vittal, Chem. Rev. 111 (2011) 688; (b) M. Fujita, M. Tominaga, A. Hori, B. Therrien, Acc. Chem. Res. 38 (2005) 369; (c) N. Stock, S. Biswas, Chem. Rev. 112 (2012) 933; (d) Q.R. Fang, G.S. Zhu, Z. Jin, Y.Y. Ji, J.W. Ye, M. Xue, H. Yang, Y. Wang, S.L. Qiu, Angew. Chem., Int. Ed. 46 (2007) 6638. [2] (a) V.N. Vukotic, S.J. Loeb, Chem. Soc. Rev. 41 (2012) 5896; (b) A.Y. Robin, K.M. Fromm, Coord. Chem. Rev. 250 (2006) 2127; (c) D.J. Tranchemontagne, J.L. Mendoza-Cortés, M. O’Keeffe, O.M. Yaghi, Chem. Soc. Rev. 38 (2009) 1257. [3] (a) Y.J. Cui, Y.F. Yue, G.D. Qian, B.L. Chen, Chem. Rev. 112 (2012) 1126; (b) O.K. Farha, J.T. Hupp, Acc. Chem. Res. 43 (2010) 1166; (c) D.F. Weng, Z.M. Wang, S. Gao, Chem. Soc. Rev. 40 (2011) 3157; (d) J.R. Li, R.J. Kuppler, H.C. Zhou, Chem. Soc. Rev. 38 (2009) 1477. [4] (a) J. Liu, P.K. Thallapally, B.P. McGrail, D.R. Brown, J. Liu, Chem. Soc. Rev. 41 (2012) 2308; (b) M.P. Suh, J.J. Park, T.K. Prasad, D.W. Lim, Chem. Rev. 112 (2012) 782; (c) Z.B. Ma, B. Moulton, Coord. Chem. Rev. 255 (2011) 1623; (d) C. Wang, Z.G. Xie, K.E. deKrafft, W.B. Lin, J. Am. Chem. Soc. 133 (2011) 13445. [5] (a) Y.B. Dong, Y.Y. Jiang, J. Li, J.P. Ma, F.L. Liu, B. Tang, R.Q. Huang, S.R. Batten, J. Am. Chem. Soc. 129 (2007) 4520; (b) P.M. Forster, A.R. Burbank, C. Livage, G. Ferey, A.K. Cheethan, Chem. Commun. (2004) 368; (c) G.Q. Zhang, G.Q. Yang, J.S. Ma, Cryst. Growth Des. 6 (2006) 1897; (d) S.T. Wu, L.S. Long, R.B. Huang, L.S. Zheng, Cryst. Growth Des. 7 (2007) 1746. [6] (a) L. Lisnard, L. Chamoreau, Y.L. Li, Y. Journaux, Cryst. Growth Des. 12 (2012) 4955; (b) G.C. Xu, Q. Hua, T. Okamura, Z.S. Bai, Y.J. Ding, Y.Q. Huang, G.X. Liu, W.Y. Sun, N. Ueyama, CrystEngComm 11 (2009) 261; (c) J. Liu, Y.X. Tan, J. Zhang, Cryst. Growth Des. 12 (2012) 5164; (d) C.P. Li, M. Du, Chem. Commun. 47 (2011) 5958.
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