- Email: [email protected]
Unusual hydrothermal synthesis of a heteroaromatic macrocyclic complex
Polyhedron 27 (2008) 3700–3702
Contents lists available at ScienceDirect
Polyhedron journal homepage: www.elsevier.com/locate/poly
Unusual hydrothermal synthesis of a heteroaromatic macrocyclic complex Eric Burkholder a, Fenton Heirtzler b,*,1, Laura Orian c, Wayne Ouellette a, Jon Zubieta a a b c
Department of Chemistry, Syracuse University 1-014 Center for Science and Technology, United States Chemical Laboratory, University of Kent, Canterbury, Kent CT2 7NH, UK Università degli Studi di Padova, Dip. Scienze Chimiche, Via Marzolo 1, 35129 Padova, Italy
a r t i c l e
i n f o
Article history: Received 18 June 2008 Accepted 13 September 2008 Available online 23 October 2008 Keywords: Macrocycle Structure Copper Hydrothermal Molybdenum
a b s t r a c t Hydrothermal treatment of 2,3-bis(20 ,600 -bipyridyl)quinoxaline, molybdenum trioxide, cupric acetate and water unexpectedly forms the Cu(II) complex of a planar, macrocyclic 2-acyl-6,20 -bipyridyl dimer, imbedded within a copper benzotrizolate-octamolybtate matrix. X-ray crystallographic characterization of this material, and scalar relativistic ZORA DFT modeling of the complex dication are presented. Ó 2008 Elsevier Ltd. All rights reserved.
This communication describes our initial results on the hydrothermal reaction of 2,3-bis(20 ,600 -bipyridyl)quinoxaline 1, available from our earlier work [1], in water. We document the formation of a planar heterocyclic macrocyclic complex, for which we are not aware of any precedent. The original goal of these studies was to extend our knowledge on the hydrothermal templating of molybdenum oxide cluster formation from simple oligopyridine derivatives [2,3] to more structurally elaborate N-heterocyclic ligands. This strategy is in line with the use of an organic ligand to structure a framework of metal oxide clusters in the lattice [4]. Conversely, with in situ ligand synthesis, templating of the ligand by the metal accounts for the observed product formation [5,6]. This furthermore requires an oxidant, such as cupric salts [7–11], V/Mo oxides [5,11,3] or even sulfur [12]. This approach has provided some unique and startling synthetic transformations, including the oxidative coupling [5,13,7], oxygenation [9,11] and fusion [3] of oligopyridine derivatives, as well as the formation of precisely oxidized cyclohexyl derivatives from smaller carbon fragments [8,12]. Specific uses for hydrothermally accessible ligands include exceptionally electrically conductive coordination complexes [14] and materials displaying high levels of second-order nonlinear optical activity [15]. Three characteristics of heteroaromatic macrocycles are ring geometry, p-conjugation and ease of synthesis. Coplanarity throughout either the ligand or its coordination complex ring sys-
* Corresponding author. Tel.: +1 301 312 5145. E-mail addresses: [email protected], [email protected] (F. Heirtzler). 1 Present address: Chemistry Department, University of Alberta, Edmonton, Alberta, Canada T6G 2G2. 0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2008.09.007
tem is important to applications depending on electronic delocalization through p-conjugation to modulate an optical or electronic response. Ring size has profound consequences on the facility of heteroaromatic ring synthesis. Template effects between bidentate precursor molecules and metal ions are especially efficacious for the synthesis of bis-2,60 -bipyridyl or -1,10-phenanthryl macrocycles that are symmetrically linked by one-atom methine, azene or mercapto bridges [16–18]. Such macrocycles are flat, and possess internal chelation cavities having diameters of 3.7 Å [19,20]. With several exceptions [21,22], this method does not apply to larger macrocycles. The aforementioned bis-bidentate ligands have potential functionality as colorimetric metal sensors [16,23], DNA recognition and cleavage agents [18,19], and electrochemical/optical gas sensors [24]. Agitating a suspension of 1, MoO3 and Cu(OAc)2 H2O in water (0.130 g: 0.112 g: 0.134 g: 10 mL), then heating for 48 h at 180 °C under autogenic pressure gave 14.4 mg (0.0139 mmol) of brown blocks in 4.7% yield based on 1 and a product formula of C33H20Cu5Mo8N10O27 [25]. Single crystal X-ray analysis of this material left open two different structural possibilities for the oligopyridyl copper(II) complex: either it exists as (a) an equimolar mixture of macrocyclic [2Cu]2+ and [bpy2Cu]2+, imbedded within a matrix of [{Cu2(benzotriazolate)}2(Mo8O26)2], or (b) the complex of the non-cyclic bis(2pyridyl)ketone 3, i.e. [3Cu][{Cu2(benzotriazolate)}2Mo8O26]. After collection of three different data sets, we conclude that the data and the model agree better with an interpretation based on equal populations of the two cupric complexes (Scheme 1) [26]. Hence, this material consists of [2Cu]2+, dicopper(II) benzotriazolate (Bt) and octamolybdate (Mo8O26) clusters in 1:1:1 ratio. The
E. Burkholder et al. / Polyhedron 27 (2008) 3700–3702
3701
Scheme 1.
O
N
N
N
N 3
dication contains two planar 2-acyl-6,20 -bipyridyl (Bpy) fragments that are interrelated by the inversion center passing through the Cu center (Fig. 1). The constituent atoms of each plane are separated from its congener by 0.588–0.689 Å. In this conformation, the diameter of the macrocyclic cavity, as measured between pairs of opposing N atoms, is 3.95–4.00 Å. All bond lengths in 2Cu2+ are within expected values, except for one of the two C–C lengths that are associated with the carbonyl groups (1.69(2) Å) and exhibit some disorder at the carbon sites [27,28]. The structure of 2Cu2+ invites comparison to the Cu(II) complexes of 3. This would be erroneous, since the latter do not simultaneously maintain molecular planarity and sp2 hybridization of the carbonyl group. Arguably, this is a result of bond angle strain induced by the geometry about the carbonyl group, and would be relieved by a highly twisted global molecular geometry [29,30]. Alternatively, carbonyl hydration permits coplanarity of the heteroaromatic groups, but disrupts interannular conjugation. In contrast, 2Cu2+ is largely coplanar and does not occur as a hydrate – in the crystal lattice and in spite of the reaction conditions. The observed widening of the angle around C@O, and of the opposite bite angle, would provide a means of strain relief. To understand its anticipated electronic structure, we calculated the molecular orbitals and geometry of 2Cu2+ using scalar relativistic ZORA DFT methods on ADF2005.01 [31]. Either full or D2hconstrained optimization, followed by vibrational analysis, converged to a D2h structure that was energetically preferred by 33.8 kcal mol1 over Ci and C2h symmetries. The resulting Cu–N distance, 1.989 Å, closely resembles commonly accepted values for d9 square planar Cu(II) porphyrins and Bpy complexes
Fig. 1. Structure of 2Cu2+ in the crystal. Selected bond angles: \C7–C17–C16: 130°; \N4–Cu1–N5: 97.9° (bite angle).
[27,28], with \N4—Cu1—N5 being 96.4° (bite angle) and \C7— C17—C16 narrowing to 125.3°. The HOMO is energetically disfavored by 1.02 eV, relative to the remaining filled orbitals, but stabilized by 1.29 eV relative to the B1u symmetrical orbital that corresponds to the closest empty level with the same spin. We take this latter value to approximate the anticipated band gap in 2Cu2+. The corresponding LUMO is ligand centered and has overall anti-bonding character. See Figs. S2 and S3 in Supplementary data for diagrams of initial and final orbitals, plus energy levels. In the lattice, 2Cu2+ has closest through-space contacts to two symmetry-related Bt equivalents, which are parallel to, and within typical stacking distances from, inversion symmetry-related 2acyl-6,20 -bipyridyl fragments (average separation of closest C5H3N to Bt mean plane: 3.425 Å; see Fig. 2). The Bt fragments occur in head-to-tail p-stacked pairs (average separation to plane: 3.522 Å) and dimerize by bridging of two symmetry-related Cu atoms to give N4Cu2-rings. Bt units that are related by either pstacking or a dicopper bridge are associated with different 2Cu2+ equivalents. Stacked and coordinating Bt pairs thus translate between the 2Cu2+ equivalents. The Cu atoms of the N4Cu2 rings and an additional Cu outside of the ring bond with tetrahedral ligand field to oxygen of Mo8O24. The Cu–N bond lengths, 1.898–1.960 Å, and the Cu–O distances, in the 1.916–2.263 Å range, are 0.1–0.2 Å greater than in known Bt–Cu(II) complexes with oxygen-donor ligands (loco cite [32]) but do not allow distinguishing the Cu oxidation state. Summarizing, we have uncovered a highly unusual synthesis of a electron-deficient, oligopyridyl-type macrocycle forming a planar Cu(II) complex. Future studies will focus on its mechanism of for-
Fig. 2. Crystal lattice of [2Cu][bpy2Cu][BtCu2Mo8O26]2, emphasizing stacking of 2Cu2+ and Bt; ligand fields: Cu: blue, Mo: green. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
3702
E. Burkholder et al. / Polyhedron 27 (2008) 3700–3702
mation, optimization and generalization, plus confirmation and prediction of its spectroscopic and electronic properties. Appendix A. Supplementary data CCDC 690429 contains the supplementary crystallographic data for this paper. 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 (crystallographic CIF file, depiction of asymmetric unit, computational details and Kohn-Sham MO diagrams) can be found, in the online version, at doi:10.1016/j.poly.2008.09.007. References [1] F.R. Heirtzler, M. Neuburger, M. Zehnder, E.C. Constable, Liebigs Ann.-Recl. (1997) 297. [2] W. Ouellette, V. Golub, C.J. O’Connor, J. Zubieta, Dalton Trans. (2005) 291. [3] E. Burkholder, J. Zubieta, Inorg. Chim. Acta 357 (2004) 1229. [4] P.J. Hagrman, D. Hagrman, J. Zubieta, Angew. Chem., Int. Ed. 38 (1999) 2639. [5] D.R. Xiao, Y. Hou, E.B. Wang, J. Lu, Y.G. Li, L. Xu, C.W. Hu, Inorg. Chem. Commun. 7 (2004) 437. [6] X.M. Zhang, Coord. Chem. Rev. 249 (2005) 1201. [7] C.M. Liu, H.Y. Gao, D.Q. Zhang, D.B. Zhu, Lett. Org. Chem. 2 (2005) 712. [8] S. Hu, J.C. Chen, M.L. Tong, B. Wang, Y.X. Yan, S.R. Batten, Angew. Chem., Int. Ed. 44 (2005) 5471. [9] X.M. Zhang, M.L. Tong, X.M. Chen, Angew. Chem., Int. Ed. 41 (2002) 1029. [10] J. Tao, Y. Zhang, M.L. Tong, X.M. Chen, T. Yuen, C.L. Lin, X.Y. Huang, J. Li, Chem. Commun. (2002) 1342. [11] Q.H. Zhao, X.F. Wang, Y.Q. Liu, R.B. Fang, Chem. Lett. 33 (2004) 138.
[12] N.F. Zheng, X.H. Bu, P.Y. Feng, J. Am. Chem. Soc. 124 (2002) 9688. [13] C.M. Liu, S. Gao, H.Z. Kou, Chem. Commun. (2001) 1670. [14] S.L. Zheng, J.P. Zhang, W.T. Wong, X.M. Chen, J. Am. Chem. Soc. 125 (2003) 6882. [15] Q. Ye, Y.-H. Li, Y.-M. Song, X.-F. Huang, R.-G. Xiong, Z. Xue, Inorg. Chem. 44 (2005) 3618. [16] S. Ogawa, R. Narushima, Y. Arai, J. Am. Chem. Soc. 106 (1984) 5760. [17] S. Ogawa, T. Uchida, T. Uchiya, T. Hirano, M. Saburi, Y. Uchida, J. Chem. Soc., Perkin Trans. 1 (1990) 1649. [18] M. Hirai, K. Shinozuka, S. Ogawa, H. Sawai, Chem. Lett. (1996) 1113. [19] C.C. Cheng, Y.N. Kuo, K.S. Chuang, C.F. Luo, W.J. Wang, Angew. Chem., Int. Ed. 38 (1999) 1255. [20] W.J. Wang, K.S. Chuang, C.F. Luo, H.Y. Liu, Tetrahedron Lett. 41 (2000) 8565. [21] A.J. Gallant, J.K.H. Hui, F.E. Zahariev, Y.A. Wang, M.J. MacLachlan, J. Org. Chem. 70 (2005) 7936. [22] J.R. Nitschke, T.D. Tilley, Angew. Chem., Int. Ed. 40 (2001) 2142. [23] R. Ibrahim, S. Tsuchiya, S. Ogawa, J. Am. Chem. Soc. 122 (2000) 12174. [24] J. Costamagna, J. Canales, J. Vargas, G. Ferraudi, Pure Appl. Chem. 67 (1995) 1045. [25] Anal. Calcd for C33H20Cu5Mo8N10O27: C, 19.1; H, 1.0; N, 6.8. Found: C, 19.7; H, 1.3; N, 6.6%. [26] Crystal data for [2Cu][bpy2Cu]{[{Cu2(benzotriazolate)Mo8O26]}2: triclinic space group, P 1, FW = 2073.86, a = 9.9538(7) Å, b = 11.4051(8) Å, a = 64.535(10)°, b = 74.892(10)°, c = 89.805(10)°, c = 12.5150(9) Å, V = 1228.7(2) A3, Z = 1, Dcalc = 2.803 g cm3, l(Mo Ka) = 4.180 mm1, R1 = 0.0508, wR2 = 0.0843. [27] J. March, Advanced Organic Chemistry, 4th ed., John Wiley and Sons, New York, 1992. [28] A.G. Orpen, L. Brammer, F.H. Allen, O. Kennard, D.G. Watson, R. Taylor, J. Chem. Soc., Dalton Trans. (1989) S1. [29] A.C. Deveson, S.L. Heath, C.J. Harding, A.K. Powell, J. Chem. Soc., Dalton Trans. (1996) 3173. [30] X.-D. Chen, T.C.W. Mak, Inorg. Chim. Acta 358 (2005) 1107. [31] G. te Velde, F.M. Bickelhaupt, E.J. Baerends, C.F. Guerra, S.J.A. Van Gisbergen, J.G. Snijders, T. Ziegler, J. Comput. Chem. 22 (2001) 931. [32] C. Richardson, P.J. Steel, Dalton Trans. (2003) 992.
Contents lists available at ScienceDirect
Polyhedron journal homepage: www.elsevier.com/locate/poly
Unusual hydrothermal synthesis of a heteroaromatic macrocyclic complex Eric Burkholder a, Fenton Heirtzler b,*,1, Laura Orian c, Wayne Ouellette a, Jon Zubieta a a b c
Department of Chemistry, Syracuse University 1-014 Center for Science and Technology, United States Chemical Laboratory, University of Kent, Canterbury, Kent CT2 7NH, UK Università degli Studi di Padova, Dip. Scienze Chimiche, Via Marzolo 1, 35129 Padova, Italy
a r t i c l e
i n f o
Article history: Received 18 June 2008 Accepted 13 September 2008 Available online 23 October 2008 Keywords: Macrocycle Structure Copper Hydrothermal Molybdenum
a b s t r a c t Hydrothermal treatment of 2,3-bis(20 ,600 -bipyridyl)quinoxaline, molybdenum trioxide, cupric acetate and water unexpectedly forms the Cu(II) complex of a planar, macrocyclic 2-acyl-6,20 -bipyridyl dimer, imbedded within a copper benzotrizolate-octamolybtate matrix. X-ray crystallographic characterization of this material, and scalar relativistic ZORA DFT modeling of the complex dication are presented. Ó 2008 Elsevier Ltd. All rights reserved.
This communication describes our initial results on the hydrothermal reaction of 2,3-bis(20 ,600 -bipyridyl)quinoxaline 1, available from our earlier work [1], in water. We document the formation of a planar heterocyclic macrocyclic complex, for which we are not aware of any precedent. The original goal of these studies was to extend our knowledge on the hydrothermal templating of molybdenum oxide cluster formation from simple oligopyridine derivatives [2,3] to more structurally elaborate N-heterocyclic ligands. This strategy is in line with the use of an organic ligand to structure a framework of metal oxide clusters in the lattice [4]. Conversely, with in situ ligand synthesis, templating of the ligand by the metal accounts for the observed product formation [5,6]. This furthermore requires an oxidant, such as cupric salts [7–11], V/Mo oxides [5,11,3] or even sulfur [12]. This approach has provided some unique and startling synthetic transformations, including the oxidative coupling [5,13,7], oxygenation [9,11] and fusion [3] of oligopyridine derivatives, as well as the formation of precisely oxidized cyclohexyl derivatives from smaller carbon fragments [8,12]. Specific uses for hydrothermally accessible ligands include exceptionally electrically conductive coordination complexes [14] and materials displaying high levels of second-order nonlinear optical activity [15]. Three characteristics of heteroaromatic macrocycles are ring geometry, p-conjugation and ease of synthesis. Coplanarity throughout either the ligand or its coordination complex ring sys-
* Corresponding author. Tel.: +1 301 312 5145. E-mail addresses: [email protected], [email protected] (F. Heirtzler). 1 Present address: Chemistry Department, University of Alberta, Edmonton, Alberta, Canada T6G 2G2. 0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2008.09.007
tem is important to applications depending on electronic delocalization through p-conjugation to modulate an optical or electronic response. Ring size has profound consequences on the facility of heteroaromatic ring synthesis. Template effects between bidentate precursor molecules and metal ions are especially efficacious for the synthesis of bis-2,60 -bipyridyl or -1,10-phenanthryl macrocycles that are symmetrically linked by one-atom methine, azene or mercapto bridges [16–18]. Such macrocycles are flat, and possess internal chelation cavities having diameters of 3.7 Å [19,20]. With several exceptions [21,22], this method does not apply to larger macrocycles. The aforementioned bis-bidentate ligands have potential functionality as colorimetric metal sensors [16,23], DNA recognition and cleavage agents [18,19], and electrochemical/optical gas sensors [24]. Agitating a suspension of 1, MoO3 and Cu(OAc)2 H2O in water (0.130 g: 0.112 g: 0.134 g: 10 mL), then heating for 48 h at 180 °C under autogenic pressure gave 14.4 mg (0.0139 mmol) of brown blocks in 4.7% yield based on 1 and a product formula of C33H20Cu5Mo8N10O27 [25]. Single crystal X-ray analysis of this material left open two different structural possibilities for the oligopyridyl copper(II) complex: either it exists as (a) an equimolar mixture of macrocyclic [2Cu]2+ and [bpy2Cu]2+, imbedded within a matrix of [{Cu2(benzotriazolate)}2(Mo8O26)2], or (b) the complex of the non-cyclic bis(2pyridyl)ketone 3, i.e. [3Cu][{Cu2(benzotriazolate)}2Mo8O26]. After collection of three different data sets, we conclude that the data and the model agree better with an interpretation based on equal populations of the two cupric complexes (Scheme 1) [26]. Hence, this material consists of [2Cu]2+, dicopper(II) benzotriazolate (Bt) and octamolybdate (Mo8O26) clusters in 1:1:1 ratio. The
E. Burkholder et al. / Polyhedron 27 (2008) 3700–3702
3701
Scheme 1.
O
N
N
N
N 3
dication contains two planar 2-acyl-6,20 -bipyridyl (Bpy) fragments that are interrelated by the inversion center passing through the Cu center (Fig. 1). The constituent atoms of each plane are separated from its congener by 0.588–0.689 Å. In this conformation, the diameter of the macrocyclic cavity, as measured between pairs of opposing N atoms, is 3.95–4.00 Å. All bond lengths in 2Cu2+ are within expected values, except for one of the two C–C lengths that are associated with the carbonyl groups (1.69(2) Å) and exhibit some disorder at the carbon sites [27,28]. The structure of 2Cu2+ invites comparison to the Cu(II) complexes of 3. This would be erroneous, since the latter do not simultaneously maintain molecular planarity and sp2 hybridization of the carbonyl group. Arguably, this is a result of bond angle strain induced by the geometry about the carbonyl group, and would be relieved by a highly twisted global molecular geometry [29,30]. Alternatively, carbonyl hydration permits coplanarity of the heteroaromatic groups, but disrupts interannular conjugation. In contrast, 2Cu2+ is largely coplanar and does not occur as a hydrate – in the crystal lattice and in spite of the reaction conditions. The observed widening of the angle around C@O, and of the opposite bite angle, would provide a means of strain relief. To understand its anticipated electronic structure, we calculated the molecular orbitals and geometry of 2Cu2+ using scalar relativistic ZORA DFT methods on ADF2005.01 [31]. Either full or D2hconstrained optimization, followed by vibrational analysis, converged to a D2h structure that was energetically preferred by 33.8 kcal mol1 over Ci and C2h symmetries. The resulting Cu–N distance, 1.989 Å, closely resembles commonly accepted values for d9 square planar Cu(II) porphyrins and Bpy complexes
Fig. 1. Structure of 2Cu2+ in the crystal. Selected bond angles: \C7–C17–C16: 130°; \N4–Cu1–N5: 97.9° (bite angle).
[27,28], with \N4—Cu1—N5 being 96.4° (bite angle) and \C7— C17—C16 narrowing to 125.3°. The HOMO is energetically disfavored by 1.02 eV, relative to the remaining filled orbitals, but stabilized by 1.29 eV relative to the B1u symmetrical orbital that corresponds to the closest empty level with the same spin. We take this latter value to approximate the anticipated band gap in 2Cu2+. The corresponding LUMO is ligand centered and has overall anti-bonding character. See Figs. S2 and S3 in Supplementary data for diagrams of initial and final orbitals, plus energy levels. In the lattice, 2Cu2+ has closest through-space contacts to two symmetry-related Bt equivalents, which are parallel to, and within typical stacking distances from, inversion symmetry-related 2acyl-6,20 -bipyridyl fragments (average separation of closest C5H3N to Bt mean plane: 3.425 Å; see Fig. 2). The Bt fragments occur in head-to-tail p-stacked pairs (average separation to plane: 3.522 Å) and dimerize by bridging of two symmetry-related Cu atoms to give N4Cu2-rings. Bt units that are related by either pstacking or a dicopper bridge are associated with different 2Cu2+ equivalents. Stacked and coordinating Bt pairs thus translate between the 2Cu2+ equivalents. The Cu atoms of the N4Cu2 rings and an additional Cu outside of the ring bond with tetrahedral ligand field to oxygen of Mo8O24. The Cu–N bond lengths, 1.898–1.960 Å, and the Cu–O distances, in the 1.916–2.263 Å range, are 0.1–0.2 Å greater than in known Bt–Cu(II) complexes with oxygen-donor ligands (loco cite [32]) but do not allow distinguishing the Cu oxidation state. Summarizing, we have uncovered a highly unusual synthesis of a electron-deficient, oligopyridyl-type macrocycle forming a planar Cu(II) complex. Future studies will focus on its mechanism of for-
Fig. 2. Crystal lattice of [2Cu][bpy2Cu][BtCu2Mo8O26]2, emphasizing stacking of 2Cu2+ and Bt; ligand fields: Cu: blue, Mo: green. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
3702
E. Burkholder et al. / Polyhedron 27 (2008) 3700–3702
mation, optimization and generalization, plus confirmation and prediction of its spectroscopic and electronic properties. Appendix A. Supplementary data CCDC 690429 contains the supplementary crystallographic data for this paper. 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 (crystallographic CIF file, depiction of asymmetric unit, computational details and Kohn-Sham MO diagrams) can be found, in the online version, at doi:10.1016/j.poly.2008.09.007. References [1] F.R. Heirtzler, M. Neuburger, M. Zehnder, E.C. Constable, Liebigs Ann.-Recl. (1997) 297. [2] W. Ouellette, V. Golub, C.J. O’Connor, J. Zubieta, Dalton Trans. (2005) 291. [3] E. Burkholder, J. Zubieta, Inorg. Chim. Acta 357 (2004) 1229. [4] P.J. Hagrman, D. Hagrman, J. Zubieta, Angew. Chem., Int. Ed. 38 (1999) 2639. [5] D.R. Xiao, Y. Hou, E.B. Wang, J. Lu, Y.G. Li, L. Xu, C.W. Hu, Inorg. Chem. Commun. 7 (2004) 437. [6] X.M. Zhang, Coord. Chem. Rev. 249 (2005) 1201. [7] C.M. Liu, H.Y. Gao, D.Q. Zhang, D.B. Zhu, Lett. Org. Chem. 2 (2005) 712. [8] S. Hu, J.C. Chen, M.L. Tong, B. Wang, Y.X. Yan, S.R. Batten, Angew. Chem., Int. Ed. 44 (2005) 5471. [9] X.M. Zhang, M.L. Tong, X.M. Chen, Angew. Chem., Int. Ed. 41 (2002) 1029. [10] J. Tao, Y. Zhang, M.L. Tong, X.M. Chen, T. Yuen, C.L. Lin, X.Y. Huang, J. Li, Chem. Commun. (2002) 1342. [11] Q.H. Zhao, X.F. Wang, Y.Q. Liu, R.B. Fang, Chem. Lett. 33 (2004) 138.
[12] N.F. Zheng, X.H. Bu, P.Y. Feng, J. Am. Chem. Soc. 124 (2002) 9688. [13] C.M. Liu, S. Gao, H.Z. Kou, Chem. Commun. (2001) 1670. [14] S.L. Zheng, J.P. Zhang, W.T. Wong, X.M. Chen, J. Am. Chem. Soc. 125 (2003) 6882. [15] Q. Ye, Y.-H. Li, Y.-M. Song, X.-F. Huang, R.-G. Xiong, Z. Xue, Inorg. Chem. 44 (2005) 3618. [16] S. Ogawa, R. Narushima, Y. Arai, J. Am. Chem. Soc. 106 (1984) 5760. [17] S. Ogawa, T. Uchida, T. Uchiya, T. Hirano, M. Saburi, Y. Uchida, J. Chem. Soc., Perkin Trans. 1 (1990) 1649. [18] M. Hirai, K. Shinozuka, S. Ogawa, H. Sawai, Chem. Lett. (1996) 1113. [19] C.C. Cheng, Y.N. Kuo, K.S. Chuang, C.F. Luo, W.J. Wang, Angew. Chem., Int. Ed. 38 (1999) 1255. [20] W.J. Wang, K.S. Chuang, C.F. Luo, H.Y. Liu, Tetrahedron Lett. 41 (2000) 8565. [21] A.J. Gallant, J.K.H. Hui, F.E. Zahariev, Y.A. Wang, M.J. MacLachlan, J. Org. Chem. 70 (2005) 7936. [22] J.R. Nitschke, T.D. Tilley, Angew. Chem., Int. Ed. 40 (2001) 2142. [23] R. Ibrahim, S. Tsuchiya, S. Ogawa, J. Am. Chem. Soc. 122 (2000) 12174. [24] J. Costamagna, J. Canales, J. Vargas, G. Ferraudi, Pure Appl. Chem. 67 (1995) 1045. [25] Anal. Calcd for C33H20Cu5Mo8N10O27: C, 19.1; H, 1.0; N, 6.8. Found: C, 19.7; H, 1.3; N, 6.6%. [26] Crystal data for [2Cu][bpy2Cu]{[{Cu2(benzotriazolate)Mo8O26]}2: triclinic space group, P 1, FW = 2073.86, a = 9.9538(7) Å, b = 11.4051(8) Å, a = 64.535(10)°, b = 74.892(10)°, c = 89.805(10)°, c = 12.5150(9) Å, V = 1228.7(2) A3, Z = 1, Dcalc = 2.803 g cm3, l(Mo Ka) = 4.180 mm1, R1 = 0.0508, wR2 = 0.0843. [27] J. March, Advanced Organic Chemistry, 4th ed., John Wiley and Sons, New York, 1992. [28] A.G. Orpen, L. Brammer, F.H. Allen, O. Kennard, D.G. Watson, R. Taylor, J. Chem. Soc., Dalton Trans. (1989) S1. [29] A.C. Deveson, S.L. Heath, C.J. Harding, A.K. Powell, J. Chem. Soc., Dalton Trans. (1996) 3173. [30] X.-D. Chen, T.C.W. Mak, Inorg. Chim. Acta 358 (2005) 1107. [31] G. te Velde, F.M. Bickelhaupt, E.J. Baerends, C.F. Guerra, S.J.A. Van Gisbergen, J.G. Snijders, T. Ziegler, J. Comput. Chem. 22 (2001) 931. [32] C. Richardson, P.J. Steel, Dalton Trans. (2003) 992.