КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 2, с. 92-98
УДК 541.49
TWO NEW CARBOXYLATE-BRIDGED ONE-DIMENSIONAL COORDINATION POLYMERS BASED ON MACROCYCLIC METALLIC TECTONS
© 2014 H. Xia*, X. Jiang, C. Jiang, and G. Liao*
Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan, 430074 P.R. China *E-mail: caihua223@gmail.com; 283451382@qq.com Received October 17, 2012
Two new one- dimensional coordination polymers: {[Cu(L1)(H4TTHA)] ■ H2O}n (I), {[Cu2(L2)2(H4TTHA)2] ■ ■ 10H2O}n (II) (L1 = 1,3,10,12,15,18-hexaazatetracyclodocosane; L2= 3,10-£is(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane), based on a flexible hexapodal ligand H6TTHA (1,3,5-triazine-2,4,6-triamine hexaacetic acid), have been synthesized and structure characterized. Single-crystal X-ray diffraction analyses indicated that the central metal atom displays distorted six-coordinate octahedral coordination geometry by coordination with four nitrogen atoms of L1 or L2, and two oxygen atoms of ^TTHA liagand. Both of the compounds show one-dimensional chain structures, which are constructed of [Cu(L)]2+ and [H4TTHA]2- anion with 1 : 1 ratio. Interestingly, the nature of the macrocycle influences the structure of the coordination polymer produced with H6TTHA for each of the two compounds. TG, IR, PXRD, and photoluminescent of the compounds are investigated.
DOI: 10.7868/S0132344X1402011X
INTRODUCTION
Supramolecular architectures based on various macrocyclic metallic tectons were attracted continued attentions because of their appealing topological structures and fascinating applications in chemistry, biology, and materials science [1—5]. Square planar macrocyclic metallic compounds with bridged aromatic polycarboxylate ligands have been proved to be an effective strategy in constructing of coordination polymers and multi-dimensional supramolecular networks [6—10]. Suh [11] utilized the tetrakis[4-(carboxy-phenyl)oxamethyl]-methane (TCM4-) anion as a tetra-hedral organic building block and [Ni(Cyclam)]2+ (Cyclam = 1,4,8,11-tetraazacyclotetradecane) complex as a linear linker to construct an eightfold interpenetrating diamondoid network for gas storage. Moon [12] also used TCM4- as a bridging ligand to construct a doubly catenated rhombic grids network, in which they introduced a nickel macrocyclic complex that contains two pyridyl pendant arms as the linker. Very recently, Jiang [13] employed a new ligand tri(4-carboxy-benzyl)amine (H3TCBA) to construct three novel supermolecular frameworks with high adsorption capacity of N2, H2, and CO2 molecules. To obtain more coordination polymers and understand how the structures and properties of coordination polymers can be tuned by the different azamacrocyclic ligands, a new hexapod carboxylic ligand H6TTHA (H6TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid) was utilized. Compared with the common aromatic polycarboxylate ligands: 1,4-benzenedicarbox-
ylic acid, 1,3,5-benzenetricarboxylic acid, and 1,2,4,5-benzenetetracarboxylic acid, H6TTHA ligand acts as a multiple ligand. H6TTHA ligand can construct more novel unpredictable and interesting su-pramolecular networks due to its following characteristics: (1) H6TTHA has six carboxyl groups for coordination, which exhibit diverse coordination fashions to construct various structures; (2) these carboxylate donor groups may be completely or partially deprotonat-ed to compensate for the charges [14]; (3) the flexible iminodiacetic acid ligands can adopt versatile conformations according to the geometric requirements of different metal ions. Therefore, a series of coordination polymers and supramolecular compounds with different structures interesting topologies and properties are to be expected when this ligand assembled with metal building block.
Inspired by above ideas and our previous works [11— 14], in this contribution, we report the syntheses, structures, and properties of two H6TTHA-bridged one-dimensional compounds: {[Cu(L1)(H4TTHA)] • H2O}B (I), {[Cu2(L2)2(H4TTHA)2] • 10H2O}„ (II) (L1 = = 1,3,10,12,15,18-hexaazatetracyclodocosane; L2 = = 3, 10- Ms(2-hydroxyethyl)-1,3,5,8,10,12-hexaaza-cyclotetradecane) by the self-assembly H6TTHA ligand with different copper macrocyclic metallic tec-tons. X-ray crystallographic analyses of compounds demonstrate that the coordination modes of H6TTHA ligand were dramatically dependent upon the introduction of substituent group on azamacrocyclic ligands. To the best of our knowledge, it is the first time
that H6TTHA has been systematic investigated as a bridged ligand linked with macrocyclic metallic tectons.
Material and methods. All reagents were purchased commercially and used without further purification. The ligand H6TTHA was prepared as described in literature [15]. Elemental analyses (C, H, and N) were performed using a Vario ELIII CHNS/O elemental analyzer. IR spectra were measured from KBr pellets on a Nicolet Avatar 370 Fourier Transform Infrared spectrometer. The powder X-ray diffraction measurements were performed on a Bruker D8 ADVANCE X-ray diffractome-ter. Thermogravimetric analysises were performed on a Diamond TG-DTA 6300 equipment in flowing N2 atmosphere with a heating rate of 10°C min-1.
Synthesis of I. The macrocyclic complex [Cu(L1)](ClO4)2 was prepared as described in literature [16]. An aqueous solution (5 mL) of [Cu(L1)](ClO4)2 (0.050 g, 0.10 mmol) was layered with a H2O-CH3OH (v/v = 1 : 1) solution (5 mL) of H6TTHA (0.050 g, 0.10 mmol) at room temperature. After about 2 days, purple crystals suitable for X-ray analysis formed. The yield was 20 mg.
For C31H48N12O13Cu
anal. calcd., %: C, 43.28; H, 5.62; N, 19.54. Found, %: C, 42.18; H, 5.88; N, 19.50.
IR (v, cm-1): 1718 (-COOH), 1488(-COO-), 1311(-COO).
Synthesis of II. The macrocyclic complex [Cu(L2)](ClO4)2 was prepared as described in literature [17]. A 10 mL aqueous solution solution of [Cu(L2)](ClO4)2 (150 mg, 0.3 mmol) added to 10 mL water of H6TTHA (150 mg, 0.3 mmol), the solution were mixed together with sitring, and then filtration and slow evaporation of the resulting solution gave red crystals in two weeks with a yield of 60 mg.
For C51H83N24O36Cu2
anal. calcd., %: C, 35.30; H, 4.82; N, 19.37. Found, %: C, 34.28; H, 5.82; N, 18.93.
IR (v, cm-1): 1724 (-COOH), 1491(-COO-), 1312(-COO-).
X-ray structure determination. Single crystal X-ray diffraction data for the compounds were collected on a Bruker Apex CCD diffractometer with graphite-monochromated Mo^a radiation (X = 0.71073 A) at 296 K. The structure was solved by direct methods and SHELXL-97 [18] and refined by full-matrix least-squares on F2 [19]. All the non-hydrogen atoms were refined anisotropically. The hydrogen atoms on the carbon and nitrogen atoms were located in a Fourier map and refined as riding on their C or N atoms. The detailed crystallographic data and structure refinement parameters for the complexes are summarized in
Table 1. Selected bond lengths and angles are listed in Table 2.
Supplementary material for structures I, II has been deposited with the Cambridge Crystallographic Data Centre (nos. 882005 (I) and 882006 (II); deposit@ccdc. cam.ac.uk or http://www.ccdc.cam.ac.uk).
RESULTS AND DISCUSSION
As shown in Fig. 1a, the X-ray single crystal structure analysis shows that compound I has an infinite one-dimensional structure. The asymmetric unit of compound I consists of one [Cu(L1)]2+ fragment, a TTHA ligand, and one uncoordinated water moleculars (as shown in Fig. 1b). The Cu(1) is six-coordinated by two carboxylate oxygen atoms (O(9), O(11)) from two TTHA ligands and four nitrogen atoms (N(1)-N(4)) from [Cu(L1)]2+. The center Cu(1) atom adopts a distorted octahedral coordinated environment. The distances between Cu(1) and coordinated nitrogen atoms are in the range from 2.006 to 2.035 A. Due to the Jahn-Teller effect, the axial Cu-O bond length (Cu(1)-O(9) 2.500, Cu(1)-O(11) 2.561 A) is longer than the Cu-N bond lengths, which are almost the same as that in the related complex [Cu(L)]3[BTC]2 ■ 9PhOH ■ 6H2O (L = 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane, BTC = = 1,3,5-benzenetricarboxylate) [20]. The axial Cu-O bonds are not perfectly perpendicular to CuN4 plane. In compound I, the hexapod H6TTHA ligand is not completely deprotonated, only two carboxylic acid groups deprotonated for balance the charges.
The X-ray single crystal structure reveals that compound II also crystallizes in an infinite one-dimensional structure. The asymmetric unit of compound II consists of two independent [Cu(L2)]2+ segment, two TTHA ligands, and ten uncoordinated water molecules (as shown in Fig. 1b). The Cu(1) atom in [Cu(L2)]2+ segment adopts a slightly distorted octahedral coordinate geometry with four nitrogen atoms of the macrocycle occupying the equatorial positions, and two oxygen atoms of TTHA located at the axial sites. Similarly, for the other [Cu(L2)]2+ structure, the Cu(2) is six-coordinated by two carboxylate oxygen atoms from two TTHA ligands and four nitrogen atoms of the L2 ligand. The Cu-O bond lengths in compound II are longer than the Cu-N bond lengths due to the Jahn-Teller effect (Cu(1)-O(3) 2.429, Cu(1)—O(21) 2.510, Cu(2)-O(10) 2.540, Cu(2)—O(29) 2.744 A).
As noted above, though similar synthetic strategies were employed for the crystallization of those crystals, polymorphs with different structural features were formed. In compound I, [H4TTHA]2- connected two copper atoms by one iminodiacetic acid, [H4TTHA]2-rank on both side of the chain to form a zigzag structure (Fig. 2a). For compound II, [H4TTHA]2- con-
Table 1. Crystallography data and refinement parameters for compounds I and II
Parameter Value
I II
Formula weight 860.35 1735.49
Crystal size, mm 0.22 x 0.21 x 0.20 0.25 x 0.24 x 0.21
Crystal system Monoclinic Triclinic
Space group P2j/c P1
a, A 19.267(3) 10.1279(19)
b, A 10.1429(16) 17.206(3)
c, A 19.918(3) 22.342(4)
a, deg 90 81.967(2)
P, deg 99.715(2) 81.701(2)
Y, deg 90 77.494(2)
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