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A new heterometallic hybrid based on polymeric iodoplumbate and lanthanide metal-carboxylic coordination polycation
Journal of Molecular Structure 1035 (2013) 109–113
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A new heterometallic hybrid based on polymeric iodoplumbate and lanthanide metal-carboxylic coordination polycation An-Weng Gong a, Hong-Yan Wu a, Zhao-Xun Lian c, Hai-Jun Dong a, Hao-Hong Li a,b,⇑, Zhi-Rong Chen a,b,⇑ a
College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou, Fujian 350108, PR China State Key Laboratory Breeding Base of Photocatalysis, Fuzhou University, Fuzhou 350002, PR China c School of Chemistry and Chemical Engineering, Henan Institute of Science and Technology, Xinxiang 453003, PR China b
h i g h l i g h t s " Incorporating lanthanide metal-carboxylic coordination polycation into polymeric iodoplumbate to get heterometallic. 6n
" ðPb6 I18 Þn
anion chains and lanthanide metal-carboxylic ½LaðEPCÞ3 ðH2 OÞ3 3nþ polycations are in criss-cross configuration. n
" semiconductor nature with optical gap of 2.46 eV.
a r t i c l e
i n f o
Article history: Received 29 March 2012 Received in revised form 17 September 2012 Accepted 17 September 2012 Available online 27 September 2012 Keywords: Hybrid framework Polymeric iodoplumbate Optical adsorption
a b s t r a c t A 3-D supramolecular hybrid {[La(EPC)3(H2O)3]2(Pb6I18)}n (EPC+ = N-ethyl-pyridium-4-carboxylate) (1) has been structurally determined, which assume significance for its incorporating lanthanide metalcarboxylic coordination polycation into polymeric iodoplumbate to get heterometallics. 1 consists of zigzag-like anion chains with lanthanide metalcarboxylic ½LaðEPCÞ3 ðH2 OÞ3 3nþ polycations, 1-D ðPb6 I18 Þ6nn n which arrange in a criss-cross configuration. C–H I and C–H O hydrogen bonds among inorganic anions and polycations contribute to the formation of a 3-D supramolecular framework. Moreover, the framework displays an absorption edge at 2.46 eV which is comparable to PbI2’s absorption edge. Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction Organic–inorganic hybrid systems have attracted much attention due to their high potential of producing novel materials [1–3], for example, the newly emerged photochromic materials [4], switchable NLO devices [5] and visible-light sensitizers for photovoltaic cells [6]. In the wide field of hybrids, iodometalate salts of lead(II) and Bi(III) are attractive for device applications owing to their versatile topological structures and enthralling properties such as electroluminescence [7], photoluminescence [4,8,9], nonlinear optical effects [10]. In addition, they have been shown to be good candidates for room temperature X-ray or c-ray detectors [11] and thin film transistors [12]. In lead iodide hybrid systems, two kinds of hybrids have been reported: lead halide polymers with discrete countercations (including organic
⇑ Corresponding authors. Addresses: College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou, Fujian 350108, PR China and State Key Laboratory Breeding Base of Photocatalysis, Fuzhou University, Fuzhou 350002, PR China. E-mail addresses: [email protected] (H.-H. Li), [email protected] (Z.-R. Chen). 0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2012.09.042
cationic templates, bifunctional organic cations [13–15], transition-metal (tm) complexes [16–19]) and lead halide-organic frameworks with organic ligands linked to inorganic skeletons via covalent bonds. In these two cases, the modification of iodoplumbate polymers using organic ligands has been wellestablished, but the introduction of second metal complexes into iodoplumbate polymers is still in its infancy. Lanthanide metalcontaining coordination polymers have attracted much attention for their potential applications in catalysis, non-linear optics, and porous materials, which stem from their unique 5d and 4f electron configurations [20–23]. Recently a lanthanide metal complex was introduced into a polymeric iodoplumbate system, giving the new hybrid compound [(Nd2DMF12IN2)(Pb8I20)]n [24]. The Lanthanide metal complex is covalently bonded to the 1D lead-iodide polymer via the HIN ligand. Previously published results [25–27] have shown that rare earth metal-aromatic polycarboxylic coordination polymers with higher order dimensions are readily formed. Herein we report a similar compound, however we have used lanthanum as the rare earth element, and chosen N-ethyl-pyridium-4carboxylate (EPC+) as the chelating ligand to obtain the new hybrid framework {[La(EPC)3(H2O)3]2(Pb6I18)}n. The chelating ligand EPC+ was chosen for the following reasons: the presence of only one
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carboxylic group will help to obtain a low dimensional structure, and the para-ethyl functional group will hinder coordination of the ligand to the Pb/I skeleton whilst providing a hydrogen bond donor as well as enlarging the coordination volume. Herein we report the structure and optical absorption of this new compound. 2. Experimental 2.1. Materials and methods All chemicals were of regent grade quality obtained from commercial sources and used without further purification. Elemental analysis for C, H and N were performed on a Vario MICRO elemental analyzer. IR spectrum was recorded on a Perkin–Elmer Spectrum-2000 FTIR spectrophotometer (4000–400 cm1) on a powdered sample spread on a KBr plate. UV–Vis spectrum was measured with a solid sample on a Perkin–Elmer lambda 900 UV/Vis spectrophotometer equipped with an integrating sphere at 293 K and BaSO4 plate used as a reference. X-ray powder diffraction (PXRD) was performed on a X-ray MiniFlexII diffractometer. 2.2. Synthesis of {[La(EPC)3(H2O)3]2(Pb6I18)}n(1) A mixture of La(ClO4)36H2O (0.136 g, 0. 25 mmol), 4-ethylbenzoic acid (0.113 g, 0.75 mmol), PbI2 (0.115 g, 0.25 mmol), KI (0.042 g, 0.25 mmol) and H2O (10.0 mL) in a mol ratio of ca. 1:3:1:1:2222 was sealed in a 25 mL stainless-steel reactor with Teflon liner and directly heated to 180 °C. This temperature was maintained for 3 days, them cooled to room temperature over a period of 24 h. Yellow prism-like crystals of 1 were obtained with 75% yield(0.149 g. based on Pb). Anal. Calc for C24H27I9LaN3O9Pb3 (2404.10): C 11.99, H 1.12,%; found C 12.03, H 1.25, N 1.64%. IR (KBr, cm1): 3459m, 3049w, 1697m, 1614s,1568s, 1452m, 1401s, 1326w, 1304w, 1236m, 1173m, 1144m, 1079w, 1047w, 970w, 873m, 782s, 758m, 690m, 661w, 613m, 550w, 491w. 2.3. X-ray single crystal diffraction The intensity data of 1 was collected on a Rigaku Weissenberg IP diffractometer using a graphite-monochromated MoKa radiation (k = 0.71069 Å) at 293(2) K. The correction of Lp factors and multi-scan absorption corrections were applied. The structure was solved by direct methods and refined on F2 by full-matrix least squares techniques using the SHELXTL-97 program [28]. All nonhydrogen atoms were refined anisotropically. Hydrogen atoms of C–H were generated geometrically. OW(2) of water is disorder, and OW(2A), OW(2B) have been refined with the refined free variable with occupancies of 50%. Only the position of OW(2A) is discussed in the structural description. Three coordinated waters are protonated as hydronium ions which were deduced from the charge balance. The hydrogen of protonated waters could not be found in the Fourier map. The final cycle of refinement gave rise to R1 = 0.0701, wR2 = 0.1451, (D/r)max = 0.000, (Dq)max = 1.583, (Dq)min = 2.141 e/Å3. Important bond lengths and angles are listed in Table 1, hydrogen bonds are shown in Table 2. Crystallographic data for 1 has been deposited at the Cambridge Crystallographic Data Center as supplementary publications. 3. Results and discussion 3.1. Description of crystal structure Single-crystal X-ray analysis reveals that 1 consists of 1-D ðPb6 I18 Þ6n zigzag-like chains and 1-D lanthanide metal-carboxylic n ½LaðEPCÞ3 ðH2 OÞ3 3nþ polymers with criss-cross a configuration, n
Table 1 Important bond lengths (Å) for 1. Bond
Dist.
Bond
Dist.
Pb(1)–I(1) Pb(1)–I(2) Pb(1)–I(3) Pb(2)–I(1) Pb(2)–I(3) Pb(2)–I(5) Pb(3)–I(4) Pb(3)–I(6) Pb(3)–I(8) Pb(4)–I(6) Pb(4)–I(8) Pb(4)–I(9) La(1)–O(1) La(1)–O(3) La(1)–O(5) La(1)–OW1 La(1)–OW3
3.2669(15) 3.2432(14) 3.2083(15) 3.3129(15) 3.2954(16) 3.2181(16) 3.2078(17) 3.575(31) 3.3343(17) 3.2103(16) 3.2412(16) 3.2518(17) 2.491(12) 2.436(11) 2.541(13) 2.606(18) 2.74(2)
Pb(1)–I(1)#1 Pb(1)–I(2)#1 Pb(1)–I(3)#1 Pb(2)–I(2) Pb(2)–I(4) Pb(2)–I(6) Pb(3)–I(5) Pb(3)–I(7) Pb(3)–I(9) Pb(4)–I(6)#2 Pb(4)–I(8)#2 Pb(4)–I(9)#2 La(1)–O(2)#3 La(1)–O(4) La(1)–O(6) La(1)–OW2A
3.2669(15) 3.2432(14) 3.2083(15) 3.1827(16) 3.1341(16) 3.2752(15) 3.1702(17) 2.9870(16) 3.2696(17) 3.2103(16) 3.2412(16) 3.2518(17) 2.372(15) 2.508(13) 2.422(12) 2.60(3)
Symmetry codes: #1 x + 1/2, y + 3/2, z; #2 x + 1, y, z + 1/2; #3 x + 1/2, y + 1/2, z + 1/2.
Table 2 Hydrogen bridging details of 1. D–H A
D–H (Å)
H A (Å)
D A (Å)
<(D–H A) (°)
C(7)–H(7B) I(1) C(23)–H(23A) I(4) C(23)–H(23B) I(5) C(13)–H(13) I(6) C(21)–H(21A) I(7) C(12)–H(12) OW(2B)
0.974 0.969 0.969 0.933 0.931 0.931
3.084 3.060 3.087 3.109 3.166 2.545
3.779 3.892 4.018 3.827 3.893 3.301
129.59 144.87 161.60 135.11 136.25 138.65
among which C–H I and C–H O hydrogen bonds contribute to the formation of a 3-D coordination framework. In all, the highly interesting feature of 1 lies in its 1-D polymeric iodoplumbate chain and templated polymeric lanthanide metal-carboxylic polymer. The ðPb6 I18 Þ6n chain can be discussed in terms of the Pb5I18 unit n (Fig. 1a), whose five lead centers adopt octahedral geometries. The Pb5I18 unit is defined by five face-sharing PbI6 octahedra and can be treated as a fragment of commonly observed ðPbI3 Þn chains n [29]. Three independent lead atoms in the Pb5I18 unit can be divided into two types: Pb(1)I6 and Pb(2)I6 octahedra which are normal coordinated environments with Pb–I lengths ranging 3.2083(15)–3.2669(15) Å (for Pb(1)) and 3.1341(16–3.2954(16) Å (for Pb(2)), these values are similar to those lengths found in the related Pb(II) complexes [13], but Pb(3) is in highly distorted octahedral geometry with Pb–I distances of 2.9870(15)–3.576(31) Å. The longest Pb-I distance (Pb(3)–I(6), 3.575(31) Å) can be observed for the triply bridging ligands I(6) due to its higher connectivity and the trans influence of the terminal ligand I(7) (Pb(3)–I(7) 2.9870(16) Å) in trans position to I(6) [30] and can be treated as highly distorted Pb–I bond. It has been proved that in group (IV) metal iodide hybrids, the geometries of metal iodides can be subtly influenced by variation in the structural requirements of the organic cation, and consequently, its metal centers will exhibit high softness or polarizability [31]. It can weakly bind the outer s electrons, which essentially allows a great degree of distortion and aggregation of the PbIx polyhedron. In all, the highly distorted Pb(3)I6 octahedron in this work again illustrates that the PbIx octahedron has a great tendency to form structures with distortion, vacancy and aggregation, through which various novel iodometalate structures can be built. Adajacent Pb5I18 units are connected via Pb(4) atoms to complete a zigzag-like chain along the (1 0 1) direction (Fig. 1). In other words, each Pb5I18 unit provides its two
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Pb5I18 unit
Fig. 1. Zigzag-like ðPb6 I18 Þ6n chain and Pb5I18 unit. n
terminal faces (defined by I(6), I(8), I(9)) to saturate the octahedral coordination geometry around Pb(4). Pb(4)I6 octahedron which acts as a linkage and is also normal with Pb–I lengths ranging from 3.2103(16) to 3.2518(17) Å. As a consequence of the connectivity of PbI6 octahedra, I atoms are acting as l3-I(6) and l2-(I(1)–I(5), I(8), I(9)) and as terminal ligands (I(7)). Pb(2) and Pb(4) occupy positions on twofold rotation axes, Pb(3) and Pb(1) are on a general position. The 1-D ½LaðEPCÞ3 ðH2 OÞ3 3nþ polymeric cations can be discussed n with the La2O18 cluster. In the La2O18 cluster, La(1) is in a ninecoordinated dicapped triangular prism environment, where six oxygen atoms are provided by carboxyl groups and three oxygen atoms (O(5), O(6) and O(8)), which stem from water molecules. LaO9 dicapped triangular prism is highly distorted with La–O distances ranging from 2.332(15)–2.74(2) Å. Adjacent La2O18 clusters are linked into a 1-D chain via the bis-monodentate bridge mode of carboxyl group of EPC ligands along the (0 1 0) direction (Fig. 2). The La–La distance is 5.432(7) Å. All the C–O bond lengths of deprotonated carboxyl groups are in normal range (1.21(2)– 1.24(2) Å) [32]. In the IR spectrum, the absorption peak at 1614 cm1 indicates the presence of deprotonated carboxylic groups of –COO. Structural analysis also shows there is only one kind of deprotonated carboxylate ligand, where carboxylic groups
act as l2-bridge with bis-monodentate bridge mode to link two La atoms, in other words, each deprotonated carboxylic group coordinates to two La atoms (Scheme 1). C–H I and C–H O hydrogen bonds (Table 2) can be observed between ðPb6 I18 Þ6n and ½LaðEPCÞ3 ðH2 OÞ3 3nþ chains, which give rise n n to a 3-D supramolecular framework. It is worth noting that the 1-D ðPb6 I18 Þ6n and ½LaðEPCÞ3 ðH2 OÞ3 3nþ chains are in a criss-cross conn n figuration (Fig. 3). In all, compared with the neutral Ln–M heterometallic framework [24] and other Ln–M coordination polymers built from discrete heterometallic clusters [23], compound 1 is based on the combination of lead–iodine chains with the La– carboxylic coordination polymer. 3.2. Absorption spectrum and linear absorption optical properties The purity of compound has been proved by PXRD (Fig. 4), in which the experimental value is visually in good agreement with the theoretical simulation. The room-temperature UV–Vis absorption spectrum (Fig. 5a) of 1 exhibits absorption peaks at 258, 313, 382 and 468 nm. The absorption peak at around 258, 313 nm can be attributed to the p–p⁄ transfer of EBA ligands and L–M charge transfer [32], and two peaks at 382 and 468 nm stem from exciton states associated with the inorganic iodoplumbate moiety [33].
La2O18 cluster
Fig. 2. Structure of 1-D ½LaðEBAÞ3nþ polymeric chain and La2O18 cluster. n
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A.-W. Gong et al. / Journal of Molecular Structure 1035 (2013) 109–113 382nm
(a)
6
468nm
FR
313nm
4
258nm
2
0 150
Scheme 1. Coordination modes of EPC ligand.
300
450
600
750
900
/ nm 40 35
(b)
30
FR2
25 20 15 10 5 0 2 2.46ev
4
6
Eg/ev Fig. 5. UV–Vis absorption spectrum (a) and optical adsorption spectrum (b) of 1.
straightforward extrapolation method [34,35]), which is very close to the measured value of 2.47–2.49 eV for bulk PbI2 [36]. 4. Conclusions In conclusion, a 3-D supramolecular hybrid framework has been synthesized and structurally described, the highly interesting feature of which lies in its combination of 1-D polymeric iodoplumbate chain with polymeric lanthanide metal–carboxylic polymer. It exhibits a semi-conducting nature judging from the optical adsorption spectrum.
Fig. 3. The 3-D framewrok of 1 based on H-bonds.
4000 Experimental value 3000
Acknowledgements 2000
Theoretical simulation
1000
0 0
10
20
30
40
We acknowledge support of this research by national natural science foundation of China (No. 20901017), specialized research fund for the doctoral program of higher education of China (20093514120003) and scientific research foundation of distinguished young scholars of Fujian higher education institutions (JA10007).
50
Appendix A. Supplementary material Fig. 4. X-ray powder diffraction (PXRD) patterns of 1.
The optical absorption spectrum of 1 has been measured by diffuse-reflectance experiments. The absorption edge for 1 is about 2.46 eV, suggesting that the present compound belongs to semiconductor (Fig. 5b, the value of Eg was obtained with use of a
The experimental details, PXRD and UV–Vis spectra can be found in supporting material section. Crystallographic data for the structure reported in this paper has been deposited with the Cambridge Crystallographic Data Center as supplementary publication No. CCDC-761950. Copies of the data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Center (CCDC), 12 Union
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Road, Cambridge CB2 1EZ, UK; fax: +44 (0)1223 336033; email: [email protected]). Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.molstruc.2012. 09.042. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]
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A new heterometallic hybrid based on polymeric iodoplumbate and lanthanide metal-carboxylic coordination polycation An-Weng Gong a, Hong-Yan Wu a, Zhao-Xun Lian c, Hai-Jun Dong a, Hao-Hong Li a,b,⇑, Zhi-Rong Chen a,b,⇑ a
College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou, Fujian 350108, PR China State Key Laboratory Breeding Base of Photocatalysis, Fuzhou University, Fuzhou 350002, PR China c School of Chemistry and Chemical Engineering, Henan Institute of Science and Technology, Xinxiang 453003, PR China b
h i g h l i g h t s " Incorporating lanthanide metal-carboxylic coordination polycation into polymeric iodoplumbate to get heterometallic. 6n
" ðPb6 I18 Þn
anion chains and lanthanide metal-carboxylic ½LaðEPCÞ3 ðH2 OÞ3 3nþ polycations are in criss-cross configuration. n
" semiconductor nature with optical gap of 2.46 eV.
a r t i c l e
i n f o
Article history: Received 29 March 2012 Received in revised form 17 September 2012 Accepted 17 September 2012 Available online 27 September 2012 Keywords: Hybrid framework Polymeric iodoplumbate Optical adsorption
a b s t r a c t A 3-D supramolecular hybrid {[La(EPC)3(H2O)3]2(Pb6I18)}n (EPC+ = N-ethyl-pyridium-4-carboxylate) (1) has been structurally determined, which assume significance for its incorporating lanthanide metalcarboxylic coordination polycation into polymeric iodoplumbate to get heterometallics. 1 consists of zigzag-like anion chains with lanthanide metalcarboxylic ½LaðEPCÞ3 ðH2 OÞ3 3nþ polycations, 1-D ðPb6 I18 Þ6nn n which arrange in a criss-cross configuration. C–H I and C–H O hydrogen bonds among inorganic anions and polycations contribute to the formation of a 3-D supramolecular framework. Moreover, the framework displays an absorption edge at 2.46 eV which is comparable to PbI2’s absorption edge. Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction Organic–inorganic hybrid systems have attracted much attention due to their high potential of producing novel materials [1–3], for example, the newly emerged photochromic materials [4], switchable NLO devices [5] and visible-light sensitizers for photovoltaic cells [6]. In the wide field of hybrids, iodometalate salts of lead(II) and Bi(III) are attractive for device applications owing to their versatile topological structures and enthralling properties such as electroluminescence [7], photoluminescence [4,8,9], nonlinear optical effects [10]. In addition, they have been shown to be good candidates for room temperature X-ray or c-ray detectors [11] and thin film transistors [12]. In lead iodide hybrid systems, two kinds of hybrids have been reported: lead halide polymers with discrete countercations (including organic
⇑ Corresponding authors. Addresses: College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou, Fujian 350108, PR China and State Key Laboratory Breeding Base of Photocatalysis, Fuzhou University, Fuzhou 350002, PR China. E-mail addresses: [email protected] (H.-H. Li), [email protected] (Z.-R. Chen). 0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2012.09.042
cationic templates, bifunctional organic cations [13–15], transition-metal (tm) complexes [16–19]) and lead halide-organic frameworks with organic ligands linked to inorganic skeletons via covalent bonds. In these two cases, the modification of iodoplumbate polymers using organic ligands has been wellestablished, but the introduction of second metal complexes into iodoplumbate polymers is still in its infancy. Lanthanide metalcontaining coordination polymers have attracted much attention for their potential applications in catalysis, non-linear optics, and porous materials, which stem from their unique 5d and 4f electron configurations [20–23]. Recently a lanthanide metal complex was introduced into a polymeric iodoplumbate system, giving the new hybrid compound [(Nd2DMF12IN2)(Pb8I20)]n [24]. The Lanthanide metal complex is covalently bonded to the 1D lead-iodide polymer via the HIN ligand. Previously published results [25–27] have shown that rare earth metal-aromatic polycarboxylic coordination polymers with higher order dimensions are readily formed. Herein we report a similar compound, however we have used lanthanum as the rare earth element, and chosen N-ethyl-pyridium-4carboxylate (EPC+) as the chelating ligand to obtain the new hybrid framework {[La(EPC)3(H2O)3]2(Pb6I18)}n. The chelating ligand EPC+ was chosen for the following reasons: the presence of only one
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carboxylic group will help to obtain a low dimensional structure, and the para-ethyl functional group will hinder coordination of the ligand to the Pb/I skeleton whilst providing a hydrogen bond donor as well as enlarging the coordination volume. Herein we report the structure and optical absorption of this new compound. 2. Experimental 2.1. Materials and methods All chemicals were of regent grade quality obtained from commercial sources and used without further purification. Elemental analysis for C, H and N were performed on a Vario MICRO elemental analyzer. IR spectrum was recorded on a Perkin–Elmer Spectrum-2000 FTIR spectrophotometer (4000–400 cm1) on a powdered sample spread on a KBr plate. UV–Vis spectrum was measured with a solid sample on a Perkin–Elmer lambda 900 UV/Vis spectrophotometer equipped with an integrating sphere at 293 K and BaSO4 plate used as a reference. X-ray powder diffraction (PXRD) was performed on a X-ray MiniFlexII diffractometer. 2.2. Synthesis of {[La(EPC)3(H2O)3]2(Pb6I18)}n(1) A mixture of La(ClO4)36H2O (0.136 g, 0. 25 mmol), 4-ethylbenzoic acid (0.113 g, 0.75 mmol), PbI2 (0.115 g, 0.25 mmol), KI (0.042 g, 0.25 mmol) and H2O (10.0 mL) in a mol ratio of ca. 1:3:1:1:2222 was sealed in a 25 mL stainless-steel reactor with Teflon liner and directly heated to 180 °C. This temperature was maintained for 3 days, them cooled to room temperature over a period of 24 h. Yellow prism-like crystals of 1 were obtained with 75% yield(0.149 g. based on Pb). Anal. Calc for C24H27I9LaN3O9Pb3 (2404.10): C 11.99, H 1.12,%; found C 12.03, H 1.25, N 1.64%. IR (KBr, cm1): 3459m, 3049w, 1697m, 1614s,1568s, 1452m, 1401s, 1326w, 1304w, 1236m, 1173m, 1144m, 1079w, 1047w, 970w, 873m, 782s, 758m, 690m, 661w, 613m, 550w, 491w. 2.3. X-ray single crystal diffraction The intensity data of 1 was collected on a Rigaku Weissenberg IP diffractometer using a graphite-monochromated MoKa radiation (k = 0.71069 Å) at 293(2) K. The correction of Lp factors and multi-scan absorption corrections were applied. The structure was solved by direct methods and refined on F2 by full-matrix least squares techniques using the SHELXTL-97 program [28]. All nonhydrogen atoms were refined anisotropically. Hydrogen atoms of C–H were generated geometrically. OW(2) of water is disorder, and OW(2A), OW(2B) have been refined with the refined free variable with occupancies of 50%. Only the position of OW(2A) is discussed in the structural description. Three coordinated waters are protonated as hydronium ions which were deduced from the charge balance. The hydrogen of protonated waters could not be found in the Fourier map. The final cycle of refinement gave rise to R1 = 0.0701, wR2 = 0.1451, (D/r)max = 0.000, (Dq)max = 1.583, (Dq)min = 2.141 e/Å3. Important bond lengths and angles are listed in Table 1, hydrogen bonds are shown in Table 2. Crystallographic data for 1 has been deposited at the Cambridge Crystallographic Data Center as supplementary publications. 3. Results and discussion 3.1. Description of crystal structure Single-crystal X-ray analysis reveals that 1 consists of 1-D ðPb6 I18 Þ6n zigzag-like chains and 1-D lanthanide metal-carboxylic n ½LaðEPCÞ3 ðH2 OÞ3 3nþ polymers with criss-cross a configuration, n
Table 1 Important bond lengths (Å) for 1. Bond
Dist.
Bond
Dist.
Pb(1)–I(1) Pb(1)–I(2) Pb(1)–I(3) Pb(2)–I(1) Pb(2)–I(3) Pb(2)–I(5) Pb(3)–I(4) Pb(3)–I(6) Pb(3)–I(8) Pb(4)–I(6) Pb(4)–I(8) Pb(4)–I(9) La(1)–O(1) La(1)–O(3) La(1)–O(5) La(1)–OW1 La(1)–OW3
3.2669(15) 3.2432(14) 3.2083(15) 3.3129(15) 3.2954(16) 3.2181(16) 3.2078(17) 3.575(31) 3.3343(17) 3.2103(16) 3.2412(16) 3.2518(17) 2.491(12) 2.436(11) 2.541(13) 2.606(18) 2.74(2)
Pb(1)–I(1)#1 Pb(1)–I(2)#1 Pb(1)–I(3)#1 Pb(2)–I(2) Pb(2)–I(4) Pb(2)–I(6) Pb(3)–I(5) Pb(3)–I(7) Pb(3)–I(9) Pb(4)–I(6)#2 Pb(4)–I(8)#2 Pb(4)–I(9)#2 La(1)–O(2)#3 La(1)–O(4) La(1)–O(6) La(1)–OW2A
3.2669(15) 3.2432(14) 3.2083(15) 3.1827(16) 3.1341(16) 3.2752(15) 3.1702(17) 2.9870(16) 3.2696(17) 3.2103(16) 3.2412(16) 3.2518(17) 2.372(15) 2.508(13) 2.422(12) 2.60(3)
Symmetry codes: #1 x + 1/2, y + 3/2, z; #2 x + 1, y, z + 1/2; #3 x + 1/2, y + 1/2, z + 1/2.
Table 2 Hydrogen bridging details of 1. D–H A
D–H (Å)
H A (Å)
D A (Å)
<(D–H A) (°)
C(7)–H(7B) I(1) C(23)–H(23A) I(4) C(23)–H(23B) I(5) C(13)–H(13) I(6) C(21)–H(21A) I(7) C(12)–H(12) OW(2B)
0.974 0.969 0.969 0.933 0.931 0.931
3.084 3.060 3.087 3.109 3.166 2.545
3.779 3.892 4.018 3.827 3.893 3.301
129.59 144.87 161.60 135.11 136.25 138.65
among which C–H I and C–H O hydrogen bonds contribute to the formation of a 3-D coordination framework. In all, the highly interesting feature of 1 lies in its 1-D polymeric iodoplumbate chain and templated polymeric lanthanide metal-carboxylic polymer. The ðPb6 I18 Þ6n chain can be discussed in terms of the Pb5I18 unit n (Fig. 1a), whose five lead centers adopt octahedral geometries. The Pb5I18 unit is defined by five face-sharing PbI6 octahedra and can be treated as a fragment of commonly observed ðPbI3 Þn chains n [29]. Three independent lead atoms in the Pb5I18 unit can be divided into two types: Pb(1)I6 and Pb(2)I6 octahedra which are normal coordinated environments with Pb–I lengths ranging 3.2083(15)–3.2669(15) Å (for Pb(1)) and 3.1341(16–3.2954(16) Å (for Pb(2)), these values are similar to those lengths found in the related Pb(II) complexes [13], but Pb(3) is in highly distorted octahedral geometry with Pb–I distances of 2.9870(15)–3.576(31) Å. The longest Pb-I distance (Pb(3)–I(6), 3.575(31) Å) can be observed for the triply bridging ligands I(6) due to its higher connectivity and the trans influence of the terminal ligand I(7) (Pb(3)–I(7) 2.9870(16) Å) in trans position to I(6) [30] and can be treated as highly distorted Pb–I bond. It has been proved that in group (IV) metal iodide hybrids, the geometries of metal iodides can be subtly influenced by variation in the structural requirements of the organic cation, and consequently, its metal centers will exhibit high softness or polarizability [31]. It can weakly bind the outer s electrons, which essentially allows a great degree of distortion and aggregation of the PbIx polyhedron. In all, the highly distorted Pb(3)I6 octahedron in this work again illustrates that the PbIx octahedron has a great tendency to form structures with distortion, vacancy and aggregation, through which various novel iodometalate structures can be built. Adajacent Pb5I18 units are connected via Pb(4) atoms to complete a zigzag-like chain along the (1 0 1) direction (Fig. 1). In other words, each Pb5I18 unit provides its two
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Pb5I18 unit
Fig. 1. Zigzag-like ðPb6 I18 Þ6n chain and Pb5I18 unit. n
terminal faces (defined by I(6), I(8), I(9)) to saturate the octahedral coordination geometry around Pb(4). Pb(4)I6 octahedron which acts as a linkage and is also normal with Pb–I lengths ranging from 3.2103(16) to 3.2518(17) Å. As a consequence of the connectivity of PbI6 octahedra, I atoms are acting as l3-I(6) and l2-(I(1)–I(5), I(8), I(9)) and as terminal ligands (I(7)). Pb(2) and Pb(4) occupy positions on twofold rotation axes, Pb(3) and Pb(1) are on a general position. The 1-D ½LaðEPCÞ3 ðH2 OÞ3 3nþ polymeric cations can be discussed n with the La2O18 cluster. In the La2O18 cluster, La(1) is in a ninecoordinated dicapped triangular prism environment, where six oxygen atoms are provided by carboxyl groups and three oxygen atoms (O(5), O(6) and O(8)), which stem from water molecules. LaO9 dicapped triangular prism is highly distorted with La–O distances ranging from 2.332(15)–2.74(2) Å. Adjacent La2O18 clusters are linked into a 1-D chain via the bis-monodentate bridge mode of carboxyl group of EPC ligands along the (0 1 0) direction (Fig. 2). The La–La distance is 5.432(7) Å. All the C–O bond lengths of deprotonated carboxyl groups are in normal range (1.21(2)– 1.24(2) Å) [32]. In the IR spectrum, the absorption peak at 1614 cm1 indicates the presence of deprotonated carboxylic groups of –COO. Structural analysis also shows there is only one kind of deprotonated carboxylate ligand, where carboxylic groups
act as l2-bridge with bis-monodentate bridge mode to link two La atoms, in other words, each deprotonated carboxylic group coordinates to two La atoms (Scheme 1). C–H I and C–H O hydrogen bonds (Table 2) can be observed between ðPb6 I18 Þ6n and ½LaðEPCÞ3 ðH2 OÞ3 3nþ chains, which give rise n n to a 3-D supramolecular framework. It is worth noting that the 1-D ðPb6 I18 Þ6n and ½LaðEPCÞ3 ðH2 OÞ3 3nþ chains are in a criss-cross conn n figuration (Fig. 3). In all, compared with the neutral Ln–M heterometallic framework [24] and other Ln–M coordination polymers built from discrete heterometallic clusters [23], compound 1 is based on the combination of lead–iodine chains with the La– carboxylic coordination polymer. 3.2. Absorption spectrum and linear absorption optical properties The purity of compound has been proved by PXRD (Fig. 4), in which the experimental value is visually in good agreement with the theoretical simulation. The room-temperature UV–Vis absorption spectrum (Fig. 5a) of 1 exhibits absorption peaks at 258, 313, 382 and 468 nm. The absorption peak at around 258, 313 nm can be attributed to the p–p⁄ transfer of EBA ligands and L–M charge transfer [32], and two peaks at 382 and 468 nm stem from exciton states associated with the inorganic iodoplumbate moiety [33].
La2O18 cluster
Fig. 2. Structure of 1-D ½LaðEBAÞ3nþ polymeric chain and La2O18 cluster. n
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(a)
6
468nm
FR
313nm
4
258nm
2
0 150
Scheme 1. Coordination modes of EPC ligand.
300
450
600
750
900
/ nm 40 35
(b)
30
FR2
25 20 15 10 5 0 2 2.46ev
4
6
Eg/ev Fig. 5. UV–Vis absorption spectrum (a) and optical adsorption spectrum (b) of 1.
straightforward extrapolation method [34,35]), which is very close to the measured value of 2.47–2.49 eV for bulk PbI2 [36]. 4. Conclusions In conclusion, a 3-D supramolecular hybrid framework has been synthesized and structurally described, the highly interesting feature of which lies in its combination of 1-D polymeric iodoplumbate chain with polymeric lanthanide metal–carboxylic polymer. It exhibits a semi-conducting nature judging from the optical adsorption spectrum.
Fig. 3. The 3-D framewrok of 1 based on H-bonds.
4000 Experimental value 3000
Acknowledgements 2000
Theoretical simulation
1000
0 0
10
20
30
40
We acknowledge support of this research by national natural science foundation of China (No. 20901017), specialized research fund for the doctoral program of higher education of China (20093514120003) and scientific research foundation of distinguished young scholars of Fujian higher education institutions (JA10007).
50
Appendix A. Supplementary material Fig. 4. X-ray powder diffraction (PXRD) patterns of 1.
The optical absorption spectrum of 1 has been measured by diffuse-reflectance experiments. The absorption edge for 1 is about 2.46 eV, suggesting that the present compound belongs to semiconductor (Fig. 5b, the value of Eg was obtained with use of a
The experimental details, PXRD and UV–Vis spectra can be found in supporting material section. Crystallographic data for the structure reported in this paper has been deposited with the Cambridge Crystallographic Data Center as supplementary publication No. CCDC-761950. Copies of the data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Center (CCDC), 12 Union
A.-W. Gong et al. / Journal of Molecular Structure 1035 (2013) 109–113
Road, Cambridge CB2 1EZ, UK; fax: +44 (0)1223 336033; email: [email protected]). Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.molstruc.2012. 09.042. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]
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