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Self-assembling architectures by the metal complexes
Materials Science and Engineering C 10 Ž1999. 59–65 www.elsevier.comrlocatermsec
Short communication
Self-assembling architectures by the metal complexes Xiao-zeng You
)
Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing UniÕersity, Nanjing 210093, China Accepted 21 May 1999
Abstract With the concepts of supramolecular chemistry, the metal complexes as potential building blocks for materials undergoing self-assembly are reviewed briefly by some recent results of 1-3D architectures in our group. q 1999 Elsevier Science S.A. All rights reserved. Keywords: Self-assembly; Complexes; Materials
1. Introduction
2. One dimensional arrays
In recent years molecular assembly has received increasing attention at the frontier of both organic and inorganic chemistry w1,2x. The specific weak intermolecular interaction in these systems is attributed to electrostatic, hydrogen bonding and Van der Waals force. Coordination chemistry in the light of the concepts of supramolecular chemistry, may provide a powerful method in the design of new materials, which is quite attractive since polymerization by the usual synthetic methods is a tedious and low-yield process. The level of conscious structural design represents an attractive means of forming different dimensional extended solids. Functionalized metal complexes, for their special bonding and structures, lend themselves as potential building blocks of molecular-based materials. The topological connectivities and structures are controlled by various conditions, such as metal, ligand, solvent, reaction sequence, PH, temperature and reaction time. With the intention to employ molecular engineering design by the idea of supramolecules and the application of its optical and magnetic properties, some self-assembling architectures by metal complexes are reviewed briefly here with some recent results in our group.
2.1. An unusual helical chain in (C16 H19 N2 )2` 1[ Cu 5 I 7 ]4
)
Tel.: q86-025-3592969; fax: q86-025-3317761
Low-dimensional organic–inorganic hybrid compounds have attracted increasing interest w3x, related to their transport w3x, optical w4x, magnetic w5x, and even lead to new solid-state structures. There has been renewed interest in iodine-rich polyhalides in the supramolecular inorganic architectures and template assemblies at complexed cations w6x. For example, the iodocuprateŽI. structures in the organic–inorganic hybrid compounds demonstrated a wide range of possibilities because of influence of the size, shape and charge distribution of the associated organic components. We have synthesized an interesting compound of 2-w p-ŽDimethylamino.styrylx-1-methylpyridinium HeptaiodopentacopperŽI., ŽC 16 H 19 N2 . 2` 1wCu 5 I 7 x 4 , which exhibits a 1-D helical structure of anion with a self-supporting axis ŽFig. 1.. To the best of our knowledge, so far there was no reported example of CuŽI. in both pseudo trigonal pyramidal and tetrahedral geometry w7x. The individual `1 wCu 5 I 7 x chain is included by one-dimensional herring-bone stacking of wC 16 H 19 N2 xq cations, which was formed through alternative stacking. The 1-D chains are weakly held together by Van der Waals interaction forming the extended solid state structures. In contrary, the anion in the compound of wŽC 3 H 7 .4 Nx 2` 1 wCu 5 I 7 x is an isolated cluster w8x. The change of structures might be attributed to counterion effect. In general, a certain cation with strong delocalization of p-electron may have the
0928-4931r99r$ - see front matter q 1999 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 8 - 4 9 3 1 Ž 9 9 . 0 0 1 1 2 - 5
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X.-z. You r Materials Science and Engineering C 10 (1999) 59–65
Fig. 1. Crystal packing of ŽC 16 H 19 N2 . 2` 1 wCu 5 I 7 x 4 in perspective view along the c-axis.
ability to screen properly anionic species of a given size and shape. This associative interaction can lead to higher dimension in the anionic part of the structure even though the stoichiometry of atoms in the structure remains constant w7,9x. Moreover, the herring-bone packing of the cation built up a one-dimensional channel, thus stabilizing the unusual polymeric anionic ions. These results suggest that the mild conditions could provide an opportunity to obtain new solid state compounds in which unusual structure and coordination spheres could be achieved in organic–inorganic hybrid compounds. 2.2. p – p interaction in cis-palladium complex for NLO Tremendous efforts have been devoted to design new NLO material of metal complexes w10x. It has been postulated that the extensive electron delocalization in the organic ligands is quite helpful for metal complexes to show large nonlinear optical properties w11,12x. However, experimental studies have been always hampered by the inherent difficulty of designing a system with a space group of
asymmetric center. Various stacking interactions between suitable aromatic rings of two coordinated intramolecular ligands in ternary complexes have been investigated w13x. A cis-configuration palladium complex of 4,5-diazafluorene-9-one thiosemicarbazone, C 24 H 16 N10 PdS 2 P 2H 2 O, which exhibits approximately five times the SHG efficiency of urea, has been designed and synthesizedw13x. X-ray structure characterization and 1 H-NMR spectra show that the cis-positioning of the two ligands was stabilized by the p–p interaction between the two delocalized diazafluorene moieties. The intramolecular stacking is shown as Fig. 2. The crystal lattice with the 31 screw-axis in the P 31 space group is further stabilized by intermolecular H-bonding between O and N w14x. 2.3. A New neutral dithiolene complexes showing optical limiting effect Nickel-dithiolenes represents a class of compounds which show important and peculiar properties such as
X.-z. You r Materials Science and Engineering C 10 (1999) 59–65
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3. Layered and network packing
3.1. New layer phosphate intercalating compounds
Fig. 2. Molecular structure of cis-configuration Palladium complex.
electrical conductivity w15,16x, third-order optical nonlinearities w17x and the very intense electronic transition in the near-IR w18x. To our knowledge, only a few neutral nickel-dithiolenes containing SR donors have been studied. In the course of looking for more suitable Q-switch dyes, a nickel complex of 4,5-Ž cis-1,2-cyclohexylenedithio.-1,3-dithiole-2-thione, wNiŽC 8 S 4 H 10 . 2 x, containing a more suitable fixed SR donor is prepared and characterized ŽFig. 3.. The complex exhibiting an intense near-IR absorption at 1035 nm and showing good responses for pico-second optical limiting is studied for the first time. The shortest intermolecular S PPP S distance is 3.8052Ž9. ˚ The cyclohexyl ring adopts a chair conformation, preA. venting the formation of stacks with close intermolecular contacts, but promoting the herring bone stacking.
Organic phosphates have been widely used in biomolecular and material science. Very few compounds are intercalated only in the way of H-bonds between the phosphates w19x. A new organic phosphate of Ž8-HQ DH. P ŽH 2 PO4 . P H 2 O, Ž8-H DQ represents 8-hydroxy-quinoldine, C 10 H 9 NO., has been obtained by hydrothermal method. The structure is shown in Fig. 4. The intercalating compound formed a novel layered structure with two similar sheets zigzagging alternatively.
3.2. Square network inclusion compounds for separation Inclusion phenomena and molecular recognition as well as noncovalent interactions are essentially considered at the modern chemistry. A series of cadmium-containing 2D square grid network derived from 4,4X-bipyridine which included molecules was reported since 1992 w20–22x. It was surprisingly found that one dimensional infinite chain polymer wCdŽ4,4X-bpy. 3 ŽH 2 O. 2 x ŽClO4 . 2 P 1.25 H 2 O Ž1. is able to transfer into 2D square network structures after clathrating some suitable guest molecules. When guest
Fig. 3. Packing of the molecule in the unit cell of wNiŽC 8 H 10 S 4 . 2 x viewed down the a-axis.
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X.-z. You r Materials Science and Engineering C 10 (1999) 59–65
Fig. 4. Intercalating structure of Ž8-HQDH. P ŽH 2 PO4 . P H 2 O.
molecules of o-nitroaniline or 2-methyl-5-nitroaniline were present, 2D square network inclusion coordination polymers wCdŽ4,4X-bpy. 2 ŽH 2 O. 2 x ŽClO4 . 2 P Ž4,4X-bpy. P ŽC 6H 6 N2O 2 . 2 P H 2 O Ž2. or wCdŽ4,4X-bpy. 2ŽH 2O. 2 xŽC 7H 8N2O 2 . 2 P Ž4,4X-bpy. P H 2 OŽClO4 . 2 Ž3. were formed. They possess the stoichiometry of 1:2:1:2 of metal: coordinated 4,4X-bpy: uncoordinated 4,4X-bpy: guest molecules; whereas in the presence of 4-chloro-2-nitrophenol molecules, 1:2:1.5:2 stoichiometry of compound wCd Ž4,4X-bpy. 2 ŽH 2 O. 2 x ŽClO4 . 2 P 1.5Ž4,4X-bpy. P ŽC 6 H 4 NO 3 Cl. P H 2 O Ž4. was obtained w22x. Because 4-chloro-2-nitrophenol guest molecules in 4 are incorporated by both hydrogen bonding and nonionic electrostatic attraction as indicated in Fig. 5, high shape specificity in the inclusion was observed during self-assembly process. This discrimination of the isomers in the clathration could be utilized to separate the mixtures of isomers as previously reported w23x. Thus, crystallization of 1 in the presence of a mixture of 4-chloro-2nitrophenol,5-chloro-2-nitrophenol and 4-chloro-3nitrophenolŽ1:1:1. yield only 4 as crystals, and the 4chloro-2-nitrophenol could be recovered by an acidic decomposition of 4.
4. Three dimensional framework 4.1. A new 12-membered ring windows in AlP molecular sieÕe A great deal of effort has been devoted to the synthesis of novel compounds with open-framework structures due to the potential applications in the fields of catalysis, ion exchange, optics and electronics w24x. Of these microporous aluminophosphate compounds w25x, the large channels are in one, two or three directions, and may not intersect each other or intersect each other only with smaller windows such as 6, 8 or 10-membered ring windows. To our knowledge, however, there are no reported examples of an open framework structure containing 12membered ring channels and intersecting each other with 12-membered ring windows in three dimensions. We found the first framework structure based on AlP molecular sieve of Mn 4 Al 5 ŽPO4 .12 ŽC 24 H 91 N18 . P 6H 2 O, in which Al, Mn are all 4-coordinated, and the 12-membered ring channels intersect each other in the football-like super cavities. The framework structure consists of three dimension of channels with windows containing twelve P and T-atoms
X.-z. You r Materials Science and Engineering C 10 (1999) 59–65
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X X Fig. 5. Projection down the b-axis of the wCdŽ4,4 -bpy. 2 ŽH 2 O. 2 x ŽClO4 . 2 P 1.5Ž4,4 bpy. P ŽC 6 H 4 NO 3 Cl. P H 2 O.
ŽT s Mn, Al. in the ²111: direction ŽFig. 6.. Three P5O groups in the window are hydrogen-bonded by molecular recognition to the organic cations which lie in the cages near the window. 4.2. Magnetism transition in 3D polymeric complex The versatile ligand azide ion has been used in more applications in the syntheses of new magnetic polymeric complexes due to its being a good superexchange pathway for two possible bridging modes: the end-to-end ŽEE. coordination gives rise to antiferro-magnetic and the end-on ŽEO. coordination to ferromagnetic interactions between the metal ions w26x. Of particular potential interest are 2D and 3D network complex polymers as it is believed that increasing dimension enhances the bulk magnetic properties w27x. We have synthesized the three-dimensional compound of wMnŽ4,4X-bipy.ŽN3 . 2 x n , in which the coordination mode of the azido ligand is EE. Azide ligands act as bridges to asymmetrically link together adjacent manganese atoms in
the EE coordination mode, forming 2D network, and the bridging 4,4X-bipyridine molecules further extend the structure into a 3D network. The xT plotting from molar magnetic susceptibility indicates that the behavior may be divided into three parts as their temperature dependence. At room temperature, the value of effective moment equals to ca. 5.5 B.M., which is already higher than expected for spin only MnŽII., suggesting the existence of spin-orbit coupling effect. The effective moment decreases continuously upon cooling until 50 K, then increases suddenly, reaches more than 8 B.M. at ca. 25 K in maximum, and goes down to 6.5 B.M. Since the Mn 2 N2 ferromagnetic unit is in high spin center canted w28x, such an interesting behavior indicates a transition from antiferro-magnetism to canted ferromagnetism at ca. 50 K. The ferromagnetism below 25 K was observed and verified in a small hysteresis loop at 5 K by magnetization measurement with various magnetic field ŽFig. 7.. The weak transition from antiferro-magnetism to ferromagnetism around 50 K was suggested to be attributed to a spin canting phenomenon. Until now, only EO bridges may be the pathway of ferromagnetism in such systems.
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Fig. 6. The 12-membered ring window in Mn 4 Al 5 ŽPO4 .12 ŽC 24 H 91 N18 . P 6H 2 O.
The development of molecular-based functional materials based on supramolecular chemistry and coordination chemistry presents a principle goal of crystal engineering. The research related to optoelectronic materials by con-
trolled sizes, shapes and chemical environments is currently undertaken in our group.
Acknowledgements This work was supported by grants from the State Science and Technology Commission of China.
References
Fig. 7. Magnetization at 5 K vs. applied field for polycrystalline comX pound of wMnŽ4,4 bpy.ŽN3 . 2 x n . The smaller scheme is the enlarged illustration in the field range of y0.5 KG to 0.5 KG.
w1x J.-M. Lehn, Supermolecular Chemistry, VCH, Weinheim, Germany, 1995. w2x J.L. Atwood, J.E.D. Davies, D.D. Macnicol ŽEds.., Inclusion compounds, Vol. 5, Oxford Univ. Press, Oxford, U.K., 1991. w3x D.B. Mitzi, K. Liang, S. Wang, Inorg. Chem. 37 Ž1998. 321. w4x X. Zhang, B. Shan, C. Duan, X. You, J. Chem. Soc., Chem. Commun., 1997, 1131. w5x P.G. Lacroix, R. Clement, K. Nakatani, J. Zyss, I. Ledoux, Science 263 Ž1994. 658. w6x A.J. Blake, R.D. Gould, W.S. Li, V. Lippolis, S. Parsons, C. Radek, M. Schroder, Angew. Chem., Int. Ed. Engl. 37 Ž1998. 293. ¨
X.-z. You r Materials Science and Engineering C 10 (1999) 59–65 w7x D.M. Young, U. Geiser, A.J. Schultz, H.H. Wang, J. Am. Chem. Soc. 120 Ž1998. 1331. w8x H. Hartl, F. Mahdjour-Hassan-Abadi, Angew. Chem., Int. Ed. Engl. 23 Ž1984. 378. w9x H. Hartl, F. Mahdjour-Hassan-Abadi, Angew. Chem., Int. Ed. Engl. 33 Ž1994. 1841. w10x J.L. Bredas, C. Adant, P. Tackx, A. Persoons, Chem. Rev. 94 Ž1994. 243. w11x J. Niu, X. You, C. Duan, H.K. Fun, Z. Zhou, Inorg. Chem. 35 Ž1996. 4211. w12x X. You, J. Photochem. Photobiol. 106 Ž1997. 85. w13x C.F. Nauman, H. Sigel, J. Am. Chem. Soc. 96 Ž1974. 2750. w14x Z.H. Liu, C.Y. Duan, J. Hu, X.Z. You, Inorg. Chem., in press. w15x X. You, Y. Zhang, Conducting Metallic Complexes, in: C.-M. Che ŽEd.., Advances in Transition Metal Coordination Chemistry, Vol., 1 JAI Press, 1996, 239. w16x Cassoux, L. Valade, H. Kobayashi, R.A. Clack, A.E. Underbill, Coord. Chem. Rev. 110 Ž1991. 115. w17x Zuo, X. You, T. Yao, H. Fun, B. Yip, J. Mater. Chem. 6 Ž10. Ž1996. 1633. w18x Bigoli, P. Deplano, F.A. Devillanova, J.R. Frraro, V. Lippolis, P.J. Lukes, M.L. Mercuri, M.A. Pellinghelli, E.F. Trogu, J.M. Willians, Inorg. Chem. 37 Ž1997. 1218.
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w19x M. Ogawa, K. Kuroda, Chem. Rev. 95 Ž1995. 399. w20x B. Robson, B.F. Abrahams, S.R. Batten, R.W. Gable, B.F. Hoskins, J. Liu, in: T. Bein ŽEd.., Supermolecular Architecture, ACS Smposium Series 499, American Chemical Society, Washington, DC, 1992, Chapter 19. w21x M. Fujita, Y.J. Kwon, S. Washizu, K. Ogura, J. Am. Chem. Soc. 116 Ž1994. 1151. w22x C.M. Liu, R.G. Xiong, X.Z. You, W. Chen, Acta Chem. Scand. 52 Ž1998. 88. w23x W.D. Schaeffer, W.S. Dorsey, D.A. Skinner, C.G. Christlan, J. Chem. Soc. 79 Ž1957. 5870. w24x D.E. De Vos, T. Frederic, P.A. Jacobs, Angew. Chem., Int. Ed. Engl. 33 Ž4. Ž1994. 431. w25x W.T.A. Harrison, L. Hannooman, Angew. Chem., Int. Ed. Engl. 36 Ž6. Ž1997. 640. w26x M.F. Charlot, O. Kahn, M. Chaillet, C. Larrieu, J. Am. Chem. Soc. 108 Ž1986. 2574. w27x F.A. Mautner, R. Cortes, L. Lezama, T. Rojo, Angew. Chem., Int. Ed. Engl. 35 Ž1996. 78. w28x M. Fujita, Y.J. Kwon, S. Washizu, K. Ogura, J. Am. Chem. Soc. 116 Ž1994. 1151, and references therein.
Short communication
Self-assembling architectures by the metal complexes Xiao-zeng You
)
Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing UniÕersity, Nanjing 210093, China Accepted 21 May 1999
Abstract With the concepts of supramolecular chemistry, the metal complexes as potential building blocks for materials undergoing self-assembly are reviewed briefly by some recent results of 1-3D architectures in our group. q 1999 Elsevier Science S.A. All rights reserved. Keywords: Self-assembly; Complexes; Materials
1. Introduction
2. One dimensional arrays
In recent years molecular assembly has received increasing attention at the frontier of both organic and inorganic chemistry w1,2x. The specific weak intermolecular interaction in these systems is attributed to electrostatic, hydrogen bonding and Van der Waals force. Coordination chemistry in the light of the concepts of supramolecular chemistry, may provide a powerful method in the design of new materials, which is quite attractive since polymerization by the usual synthetic methods is a tedious and low-yield process. The level of conscious structural design represents an attractive means of forming different dimensional extended solids. Functionalized metal complexes, for their special bonding and structures, lend themselves as potential building blocks of molecular-based materials. The topological connectivities and structures are controlled by various conditions, such as metal, ligand, solvent, reaction sequence, PH, temperature and reaction time. With the intention to employ molecular engineering design by the idea of supramolecules and the application of its optical and magnetic properties, some self-assembling architectures by metal complexes are reviewed briefly here with some recent results in our group.
2.1. An unusual helical chain in (C16 H19 N2 )2` 1[ Cu 5 I 7 ]4
)
Tel.: q86-025-3592969; fax: q86-025-3317761
Low-dimensional organic–inorganic hybrid compounds have attracted increasing interest w3x, related to their transport w3x, optical w4x, magnetic w5x, and even lead to new solid-state structures. There has been renewed interest in iodine-rich polyhalides in the supramolecular inorganic architectures and template assemblies at complexed cations w6x. For example, the iodocuprateŽI. structures in the organic–inorganic hybrid compounds demonstrated a wide range of possibilities because of influence of the size, shape and charge distribution of the associated organic components. We have synthesized an interesting compound of 2-w p-ŽDimethylamino.styrylx-1-methylpyridinium HeptaiodopentacopperŽI., ŽC 16 H 19 N2 . 2` 1wCu 5 I 7 x 4 , which exhibits a 1-D helical structure of anion with a self-supporting axis ŽFig. 1.. To the best of our knowledge, so far there was no reported example of CuŽI. in both pseudo trigonal pyramidal and tetrahedral geometry w7x. The individual `1 wCu 5 I 7 x chain is included by one-dimensional herring-bone stacking of wC 16 H 19 N2 xq cations, which was formed through alternative stacking. The 1-D chains are weakly held together by Van der Waals interaction forming the extended solid state structures. In contrary, the anion in the compound of wŽC 3 H 7 .4 Nx 2` 1 wCu 5 I 7 x is an isolated cluster w8x. The change of structures might be attributed to counterion effect. In general, a certain cation with strong delocalization of p-electron may have the
0928-4931r99r$ - see front matter q 1999 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 8 - 4 9 3 1 Ž 9 9 . 0 0 1 1 2 - 5
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X.-z. You r Materials Science and Engineering C 10 (1999) 59–65
Fig. 1. Crystal packing of ŽC 16 H 19 N2 . 2` 1 wCu 5 I 7 x 4 in perspective view along the c-axis.
ability to screen properly anionic species of a given size and shape. This associative interaction can lead to higher dimension in the anionic part of the structure even though the stoichiometry of atoms in the structure remains constant w7,9x. Moreover, the herring-bone packing of the cation built up a one-dimensional channel, thus stabilizing the unusual polymeric anionic ions. These results suggest that the mild conditions could provide an opportunity to obtain new solid state compounds in which unusual structure and coordination spheres could be achieved in organic–inorganic hybrid compounds. 2.2. p – p interaction in cis-palladium complex for NLO Tremendous efforts have been devoted to design new NLO material of metal complexes w10x. It has been postulated that the extensive electron delocalization in the organic ligands is quite helpful for metal complexes to show large nonlinear optical properties w11,12x. However, experimental studies have been always hampered by the inherent difficulty of designing a system with a space group of
asymmetric center. Various stacking interactions between suitable aromatic rings of two coordinated intramolecular ligands in ternary complexes have been investigated w13x. A cis-configuration palladium complex of 4,5-diazafluorene-9-one thiosemicarbazone, C 24 H 16 N10 PdS 2 P 2H 2 O, which exhibits approximately five times the SHG efficiency of urea, has been designed and synthesizedw13x. X-ray structure characterization and 1 H-NMR spectra show that the cis-positioning of the two ligands was stabilized by the p–p interaction between the two delocalized diazafluorene moieties. The intramolecular stacking is shown as Fig. 2. The crystal lattice with the 31 screw-axis in the P 31 space group is further stabilized by intermolecular H-bonding between O and N w14x. 2.3. A New neutral dithiolene complexes showing optical limiting effect Nickel-dithiolenes represents a class of compounds which show important and peculiar properties such as
X.-z. You r Materials Science and Engineering C 10 (1999) 59–65
61
3. Layered and network packing
3.1. New layer phosphate intercalating compounds
Fig. 2. Molecular structure of cis-configuration Palladium complex.
electrical conductivity w15,16x, third-order optical nonlinearities w17x and the very intense electronic transition in the near-IR w18x. To our knowledge, only a few neutral nickel-dithiolenes containing SR donors have been studied. In the course of looking for more suitable Q-switch dyes, a nickel complex of 4,5-Ž cis-1,2-cyclohexylenedithio.-1,3-dithiole-2-thione, wNiŽC 8 S 4 H 10 . 2 x, containing a more suitable fixed SR donor is prepared and characterized ŽFig. 3.. The complex exhibiting an intense near-IR absorption at 1035 nm and showing good responses for pico-second optical limiting is studied for the first time. The shortest intermolecular S PPP S distance is 3.8052Ž9. ˚ The cyclohexyl ring adopts a chair conformation, preA. venting the formation of stacks with close intermolecular contacts, but promoting the herring bone stacking.
Organic phosphates have been widely used in biomolecular and material science. Very few compounds are intercalated only in the way of H-bonds between the phosphates w19x. A new organic phosphate of Ž8-HQ DH. P ŽH 2 PO4 . P H 2 O, Ž8-H DQ represents 8-hydroxy-quinoldine, C 10 H 9 NO., has been obtained by hydrothermal method. The structure is shown in Fig. 4. The intercalating compound formed a novel layered structure with two similar sheets zigzagging alternatively.
3.2. Square network inclusion compounds for separation Inclusion phenomena and molecular recognition as well as noncovalent interactions are essentially considered at the modern chemistry. A series of cadmium-containing 2D square grid network derived from 4,4X-bipyridine which included molecules was reported since 1992 w20–22x. It was surprisingly found that one dimensional infinite chain polymer wCdŽ4,4X-bpy. 3 ŽH 2 O. 2 x ŽClO4 . 2 P 1.25 H 2 O Ž1. is able to transfer into 2D square network structures after clathrating some suitable guest molecules. When guest
Fig. 3. Packing of the molecule in the unit cell of wNiŽC 8 H 10 S 4 . 2 x viewed down the a-axis.
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X.-z. You r Materials Science and Engineering C 10 (1999) 59–65
Fig. 4. Intercalating structure of Ž8-HQDH. P ŽH 2 PO4 . P H 2 O.
molecules of o-nitroaniline or 2-methyl-5-nitroaniline were present, 2D square network inclusion coordination polymers wCdŽ4,4X-bpy. 2 ŽH 2 O. 2 x ŽClO4 . 2 P Ž4,4X-bpy. P ŽC 6H 6 N2O 2 . 2 P H 2 O Ž2. or wCdŽ4,4X-bpy. 2ŽH 2O. 2 xŽC 7H 8N2O 2 . 2 P Ž4,4X-bpy. P H 2 OŽClO4 . 2 Ž3. were formed. They possess the stoichiometry of 1:2:1:2 of metal: coordinated 4,4X-bpy: uncoordinated 4,4X-bpy: guest molecules; whereas in the presence of 4-chloro-2-nitrophenol molecules, 1:2:1.5:2 stoichiometry of compound wCd Ž4,4X-bpy. 2 ŽH 2 O. 2 x ŽClO4 . 2 P 1.5Ž4,4X-bpy. P ŽC 6 H 4 NO 3 Cl. P H 2 O Ž4. was obtained w22x. Because 4-chloro-2-nitrophenol guest molecules in 4 are incorporated by both hydrogen bonding and nonionic electrostatic attraction as indicated in Fig. 5, high shape specificity in the inclusion was observed during self-assembly process. This discrimination of the isomers in the clathration could be utilized to separate the mixtures of isomers as previously reported w23x. Thus, crystallization of 1 in the presence of a mixture of 4-chloro-2nitrophenol,5-chloro-2-nitrophenol and 4-chloro-3nitrophenolŽ1:1:1. yield only 4 as crystals, and the 4chloro-2-nitrophenol could be recovered by an acidic decomposition of 4.
4. Three dimensional framework 4.1. A new 12-membered ring windows in AlP molecular sieÕe A great deal of effort has been devoted to the synthesis of novel compounds with open-framework structures due to the potential applications in the fields of catalysis, ion exchange, optics and electronics w24x. Of these microporous aluminophosphate compounds w25x, the large channels are in one, two or three directions, and may not intersect each other or intersect each other only with smaller windows such as 6, 8 or 10-membered ring windows. To our knowledge, however, there are no reported examples of an open framework structure containing 12membered ring channels and intersecting each other with 12-membered ring windows in three dimensions. We found the first framework structure based on AlP molecular sieve of Mn 4 Al 5 ŽPO4 .12 ŽC 24 H 91 N18 . P 6H 2 O, in which Al, Mn are all 4-coordinated, and the 12-membered ring channels intersect each other in the football-like super cavities. The framework structure consists of three dimension of channels with windows containing twelve P and T-atoms
X.-z. You r Materials Science and Engineering C 10 (1999) 59–65
63
X X Fig. 5. Projection down the b-axis of the wCdŽ4,4 -bpy. 2 ŽH 2 O. 2 x ŽClO4 . 2 P 1.5Ž4,4 bpy. P ŽC 6 H 4 NO 3 Cl. P H 2 O.
ŽT s Mn, Al. in the ²111: direction ŽFig. 6.. Three P5O groups in the window are hydrogen-bonded by molecular recognition to the organic cations which lie in the cages near the window. 4.2. Magnetism transition in 3D polymeric complex The versatile ligand azide ion has been used in more applications in the syntheses of new magnetic polymeric complexes due to its being a good superexchange pathway for two possible bridging modes: the end-to-end ŽEE. coordination gives rise to antiferro-magnetic and the end-on ŽEO. coordination to ferromagnetic interactions between the metal ions w26x. Of particular potential interest are 2D and 3D network complex polymers as it is believed that increasing dimension enhances the bulk magnetic properties w27x. We have synthesized the three-dimensional compound of wMnŽ4,4X-bipy.ŽN3 . 2 x n , in which the coordination mode of the azido ligand is EE. Azide ligands act as bridges to asymmetrically link together adjacent manganese atoms in
the EE coordination mode, forming 2D network, and the bridging 4,4X-bipyridine molecules further extend the structure into a 3D network. The xT plotting from molar magnetic susceptibility indicates that the behavior may be divided into three parts as their temperature dependence. At room temperature, the value of effective moment equals to ca. 5.5 B.M., which is already higher than expected for spin only MnŽII., suggesting the existence of spin-orbit coupling effect. The effective moment decreases continuously upon cooling until 50 K, then increases suddenly, reaches more than 8 B.M. at ca. 25 K in maximum, and goes down to 6.5 B.M. Since the Mn 2 N2 ferromagnetic unit is in high spin center canted w28x, such an interesting behavior indicates a transition from antiferro-magnetism to canted ferromagnetism at ca. 50 K. The ferromagnetism below 25 K was observed and verified in a small hysteresis loop at 5 K by magnetization measurement with various magnetic field ŽFig. 7.. The weak transition from antiferro-magnetism to ferromagnetism around 50 K was suggested to be attributed to a spin canting phenomenon. Until now, only EO bridges may be the pathway of ferromagnetism in such systems.
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X.-z. You r Materials Science and Engineering C 10 (1999) 59–65
Fig. 6. The 12-membered ring window in Mn 4 Al 5 ŽPO4 .12 ŽC 24 H 91 N18 . P 6H 2 O.
The development of molecular-based functional materials based on supramolecular chemistry and coordination chemistry presents a principle goal of crystal engineering. The research related to optoelectronic materials by con-
trolled sizes, shapes and chemical environments is currently undertaken in our group.
Acknowledgements This work was supported by grants from the State Science and Technology Commission of China.
References
Fig. 7. Magnetization at 5 K vs. applied field for polycrystalline comX pound of wMnŽ4,4 bpy.ŽN3 . 2 x n . The smaller scheme is the enlarged illustration in the field range of y0.5 KG to 0.5 KG.
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