КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 3, с. 154-159
УДК 541.49
CRYSTAL STRUCTURES AND ELECTROCHEMICAL PROPERTIES OF TWO Mn(II) 2-SULFOTEREPHTHALATE COMPLEXES WITH N-DONOR LIGANDS © 2014 Y. Ren*, T. Hao, M. Zhang, D. Wang, H. Yu, and Y. Wang
College of Chemistry and Chemical Engineering, Shaanxi Key Laboratory of Chemical Reaction Engineering,
Yan'an University, Yan'an, 716000 P.R. China *E-mail: renyixia1@163.com Received November 27, 2012
Two Mn(II) sulfoterephthalate complexes, [Mn(HStp)(o-Phen)2] (I) and [Mn(HStp)(2,2'-Bipy)2] (II) (H3Stp = 2-sulfoterephthalic acid, o-Phen = 1,10-phenanthroline, 2,2'-Bipy = 2,2'-bipyridine), were synthesized under hydrothermal condition. Single crystal X-ray diffraction analyses reveal that complexes I and II possess similar structure, in which the center Mn2+ ions are hexa-coordinated with one Hstp- anion and two N-donor ligands. For both of them, the formation of 3D supramolecular structures are based on both H-bonds and n-'-n/C—H-n stacking interactions. Electrochemical properties of complexes I and II have been investigated by means of cyclic voltmetry, which shows that electron transfer between Mn(III) and Mn(II) in electrolysis is quasi-reversible process.
DOI: 10.7868/S0132344X14030074
INTRODUCTION
Transitional metal organic complexes have been investigated and developed increasingly in recent years for their diversified structures and potential applications [1—4]. The metal-carboxylate complexes become one of the most important series of metal organic complexes, because of the versatile coordination modes of carboxyl group and the multiform functional properties of these complexes [5—8]. Coordination fashions of the carboxyl group may be mon-dentate, bidentate, bridge, chelate, and multidentate, in result that 0D to 3D metal organic complexes exhibiting kinds of luminescent, electric and magnetic properties [9—11]. The selection of organic ligand could affect the formation and properties of metal organic complexes. 2-Sulfoterephthalate is a rigid and multidentate ligand with seven coordination sites benefited from its two carboxyl groups and one sulfonate group. Its three protons, not all dissociated, could form H-bonds with the adjacent ligands or solvent molecules, and its phenyl ring possibly assembles with some pyridine-containing ligands via n—n stacking, finally constructing high dimensional supramolecule. To our knowledge, the investigations on 2-sulfoterephthalic acid are mainly focused on the d- and /-block transitional metal complexes (Zn(II), Cd(II), Mn(II), Cu(II), Eu(III), Tb(III)) [12-16], in which only one example reported about manganese(II) complex [14]. A great opportunity to study the structural characterization about the Mn(II) complexes with the 2-HStp2-ligand inspires us to explore the supramolecular complexes from them. Moreover, we introduce three
N-donor ligands, 1,10-phenanthroline (o-Phen) and 2,2'-bipyridine (2,2'-Bipy) to form H-bonds or n—n stacking interactions and alter the dimension of the supramolecular structure. In this paper, we obtained four Mn(II) supramolecular complexes based on 2-sulfoterephthalate and three N-donor ligands.
EXPERIMENTAL
Materials and methods. All chemicals were commercially available and used as received without further purification. Elemental analyses (CHN) were performed using an Vario EL elemental analyzer. FT-IR spectra were recorded from KBr pellets in the range of 4000-400 cm-1 on a Nicolet Avatar 360 FT-IR spectrometer.
Synthesis of [Mn(HStp)(o-Phen)2] (I). A mixture of NaH2Stp (0.013 g, 0.05 mmol), o-Phen (0.019 g, 0.1 mmol) and Mn(OAc)2 • 4H2O (0.013 g, 0.05 mmol) in 5 mL H2O was stirred for 15 min, then placed in a 23-mL Teflon-lined autoclave and heated at 140°C for 96 h. The autoclave was cooled over a period of10 h by natural cooling. The yellow block crystals of I were collected by filtration, washed with ethanol, and dried in air (the yieldwas 12 mg, ~36% based on Mn).
For C32H20N4O7SMn
anal. calcd., %: Found, %:
C, 58.28; C, 58.47;
H, 3.06; H, 3.10;
N, 8.50. N, 8.65.
IR (KBr; v, cm-1): 3450 m, 3072 w, 1713 m, 1625 m, 1517 s, 1427 s, 1270 s, 1225 m, 1176 s, 1071 s, 1018 m, 797 s.
Synthesis of [Mn(HStp)(2,2'-Bipy)2] (II). A mixture of NaH2Stp (0.013 g, 0.05 mmol), 2,2'-Bipy (0.016 g, 0.1 mmol) and Mn(OAc)2 • 4H2O (0.013 g, 0.05 mmol) in 5 mL H2O was stirred for 15 min, then placed in a 23-mL Teflon-lined autoclave and heated at 140°C for 96 h. The autoclave was cooled over a period of 10 h by natural cooling. The yellow block crystals of II were collected by filtration, washed with ethanol, and dried in air (the yield was 19 mg, ~62% based on Mn).
For C28H20N4O7SMn
anal. calcd., %: C, 54.99; H, 3.30; N, 9.16. Found, %: C, 54.62; H, 3.49; N, 9.29.
IR (KBr; v, cm-1): 3450 m, 3071 w, 1712 m, 1597 m, 1520 s, 1408 s, 1267 s, 1240 s, 1171 s, 1068 m, 1016 s, 807 m.
X-ray structure determination. Single crystal X-ray diffraction analyses of the four complexes were carried out on a Bruker SMART APEX CCD diffractometer equipped with a graphite monochromated Mo^a radiation (X = 0.71073 A). Raw data were integrated with the SAINT program [17]. The structures were solved by direct methods with SHELXS-97 and refined by full-matrix least-squares on F2 using SHELXS-97 [18]. An empirical absorption correction was applied with the program SADABS [19]. All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were set in calculated positions and refined by a riding mode. The crystallographic details of complexes I, II are provided in Table 1, while the selected bond distances and angles of I, II are listed in Table 2, respectively. All the H-bonds parameters in I, II are listed in Table 3. Supplementary material for structures I, II has been deposited with the Cambridge Crystallo-graphic Data Centre (nos. 819170 (I), 819171 (II); deposit@ccdc.cam.ac.uk or http://www.ccdc.cam. ac.uk).
Table 1. Crystallographic data and structure refinement for complexes I and II
Parameter Value
I II
Mw 659.52 611.48
T, K 296(2) 296(2)
Crystal system Triclinic Triclinic
Space group P1 P1
a, A 9.5174(6) 9.1988(7)
b, A 9.7202(6) 9.7582(7)
c, A 16.8964(11) 16.3634(11)
a, deg 73.3010(10) 101.0390(10)
P, deg 97.6080(10) 98.7040(10)
Y, deg 70.1600(10) 90.9490(10)
V, A3 1402.63(15) 1423.49(18)
Z 2 2
Pcalcd g cm-1 1.562 1.427
p., mm-1 0.604 0.589
9 Range, deg 2.28-25.25 2.13-25.25
Reflection collected 7080 5091
Unique reflection 5018 5091
Rint 0.0181 0
GOOF 1.040 1.037
R1 (I > 2ct(T)) 0.0374 0.0401
wR2 (all data) 0.0913 0.1077
^max/APm^ e A-3 0.426 and -0.328 0.246 and -0.243
RESULTS AND DISCUSSION
Single-crystal X-ray diffraction analysis reveals that the asymmetric unit of I consists of one Mn2+ ion, one HStp2- anion and two o-Phen ligands. The central Mn2+ ion is hexa-coordinated with two O atom (O(1) and O(5)) from the carboxylate and the sulfonate groups of one HStp2- anion, four N atoms (N(1), N(2), N(3), and N(4)) from two o-Phen ligands, forming a distorted octahedron (Fig. 1a). The range of Mn-N bond lengths is from 2.255 to 2.336 A and the Mn-O bond lengths are 2.082 and 2.192 A, which are
in the normal scope of Mn—O and Mn—N bonds lengths in reported complexes [20—22].
The uncoordinated O atom of 1-site carboxylate group of one HStp2- anion links the protonated O atoms of 4-site carboxylate group of adjacent Hstp2- anion via its hydrogen atom forming H-bond (O(4)-H(4)-"O(24); O-O 2.521 Â). As shown in Fig. 2, the H-bonds connect mononuclear Mn molecules into 1D supramolecular chain structure along x axis.
For each Mn2+ ion, a dihedral angle of 82.6° separates two o-Phen ligands, which benefits the formation
KOOP^HH^HOHHAtf XHMHfl TOM 40 № 3 2014
Table 2. Selected bond lengths (A) and angles (deg) for complexes I and II
Bond d, A Bond d, A
I II
Mn(1)—O(1) 2.0816(16) Mn(1)-O(1) 2.0753(17)
Mn(1)—O(5) 2.1921(16) Mn(1)-O(5) 2.1871(18)
Mn(1)-N(1) 2.255(2) Mn(1)-N(1) 2.247(2)
Mn(1)-N(2) 2.260(2) Mn(1)-N(4) 2.249(2)
Mn(1)-N(4) 2.290(2) Mn(1)-N(3) 2.259(2)
Mn(1)-N(3) 2.3356(19) Mn(1)-N(2) 2.280(2)
Angle ю, deg Angle ю, deg
I II
O(1)Mn(1)O(5) 87.56(6) O(1)Mn(1)O(5) 91.34(7)
O(1)Mn(1)N(1) 159.28(7) O(1)Mn(1)N(1) 93.33(7)
O(5)Mn(1)N(1) 83.24(7) O(5)Mn(1)N(1) 93.33(7)
N(2)Mn(1)N(3) 85.27(7) O(1)Mn(1)N(4) 93.07(7)
O(1)Mn(1)N(2) 94.34(7) O(5)Mn(1)N(4) 101.52(8)
O(5)Mn(1)N(2) 117.12(7) N(1)Mn(1)N(4) 163.68(8)
N(1)Mn(1)N(2) 73.71(7) O(1)Mn(1)N(3) 164.88(7)
O(1)Mn(1)N(4) 95.01(7) O(5)Mn(1)N(3) 86.62(7)
N(4)Mn(1)N(3) 71.89(7) N(1)Mn(1)N(3) 101.74(8)
O(5)Mn(1)N(4) 84.71(7) N(4)Mn(1)N(3) 72.73(8)
N(1)Mn(1)N(4) 102.54(7) O(1)Mn(1)N(2) 94.61(7)
N(2)Mn(1)N(4) 156.59(7) O(5)Mn(1)N(2) 164.93(8)
O(1)Mn(1)N(3) 101.15(7) N(1)Mn(1)N(2) 72.54(7)
O(5)Mn(1)N(3) 155.54(7) N(4)Mn(1)N(2) 91.99(7)
N(1)Mn(1)N(3) 94.77(7) N(3)Mn(1)N(2) 91.11(8)
of Я---Я stacking interactions in different directions. Actually, the 1D supramolecular chains extend along x and z axis into 2D supramolecular layer though the face-to-face я---я stacking interactions between o-Phen ligands standing out from two angles (Fig. 3). For the face-to-face я—я stacking interactions along x axis based on Phen(1) (C(13)-C(24) and N(3)—N(4)), the perpendicular distance is 3.484 A (Cg—Cg 3.722 A) (Fig. 4a), while those along z axis based on Phen(2) (C(1)-C(12) and N(1)-N(2)) have the perpendicular distance of 3.649 A (Cg—Cg 4.075 A) (Fig. 4b). Obviously, the interaction of the former is stronger than that of the later. Furthermore, the 2D supramolecular layers extend along y axis into 3D supramolecular structure via the edge-to-face C-H-я stacking interactions between C(27)—H(27) of one HStp2- anion and the Phen(1) ligand (H(27)-Cg(1) 2.856 A) (Fig. 4c).
Table 3. Geometric parametes of hydrogen bonds in I and II*
D-H-A Distance, A Angle DHA, deg
D-H H-A D -A
O(4)- H(4) ■ O(2^)a I 0.82 1.72 2.5213(3) 164
II
O(4)- H(4) ■ O(2^)b 0.82 1.81 2.6110(2) 166
* Symmetry codes: a —1 + x, y, z;
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