Bis(phthalocyaninato)gadolinium(III) Hexacyanobutadienide(1-), [GdPc 2 ] + [C 4 (CN) 6 ] - . An Electron Transfer Salt with Four Paramagnetic Sites Durrell K. Rittenberg, † Ken-ichi Sugiura, ‡ Yoshiteru Sakata, ‡ Atta M. Arif, † and Joel S. Miller* ,† Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, and Institute for Industrial and Scientific Research, Osaka University, Osaka 565, Japan ReceiVed February 13, 2001 Metallophthalocyanines, MPc (H 2 Pc ) phthalocyanine), con- tinue to be at the forefront of modern chemistry owing to their unique chemical 1,2 and physical properties 1,3 In particular, rare- earth phthalocyanines, i.e., LnPc 2 and Ln 2 Pc 3 (Ln ) lanthanide), have received considerable attention in the past few years due to their unique electrochromic, 1 spectral, 2 and conducting proper- ties. 3 Rare-earth phthalocyanines are attractive building blocks for molecule-based magnets due to the lanthanide, which may possess up to seven unpaired electrons (i.e., S ) 7 / 2 ). In their neutral form, LnPc 2 are characterized as having stable phthalocyaninate(2-) and radical phthalocyaninate(1-) ligands consisting of (Pc 2- )- Ln +3 (Pc •- ) in resonance with (Pc •- )Ln 3+ (Pc 2- ) 4 or as Ln 4+ (Pc 2- ) 2 for Ln ) Ce. 5 Upon facile reduction to the monoanion the complex may be described as [Ln 3+ (Pc 2- ) 2 ] - , which in the case of [LuPc 2 ] - was confirmed by NMR. 2a In contrast, oxidation to [LnPc 2 ] + leads to two possible electronic structures, i.e., [Pc 2- Ln 3+ Pc 0 ] + {in resonance with [Pc 0 Ln 3+ Pc 2- ] + } or [Pc •- Ln 3+ Pc •- ] + , as well as systems with tetravalent Ln (i.e., Pc 2- Ln 4+ Pc 2- ). Very few oxidized LnPc 2 species have been characterized; however, [LuPc 2 ] + [SbF 6 ] - is reported to be diamagnetic; 4c hence it must be described as [Pc 2- Lu 3+ Pc 0 ] + or [Lu 3+ (Pc •- ) 2 ] + with strong antiferromagnetic coupling between the S ) 1 / 2 Pc •- units. For spin-containing lanthanide, e.g., Gd 3+ , the S ) 7 / 2 Gd 3+ and S ) 1 / 2 Pc •- are strongly coupled for GdPc 2 leading to an S ) 3 ground state. 4d Furthermore, on the basis of the absence of an EPR signal assignable to Pc •- and the presence of an EPR signal assignable to Gd 3+ , the ground state was reported to have a [Pc 0 Gd 3+ Pc 2- ] + electronic structure, 4b,c which was modeled by MO calculations. 6 LnPc 2 with the added feature of possessing spin-bearing ligands has a structural relationship to S ) 1 / 2 [Fe III (C 5 Me 5 ) 2 ] + , a key component in the first organic magnet, [Fe III (C 5 Me 5 ) 2 ] + [TCNE] •- (TCNE ) tetracyanoethylene) (T c ) 4.8 K). 7 Hence, [GdPc 2 ] + [TCNE] •- due to the presence of g ) 2, L ) 0 Gd 3+ , was targeted for synthesis. Although TCNE was insufficient to oxidize GdPc 2 ,C 4 (CN) 6 8 was reacted with GdPc 2 forming [GdPc 2 ]- [C 4 (CN) 6 ], 1. In accord with previous work, GdPc 2 has several sites that can be oxidized, namely, Pc •- , and Pc 2- , and unlikely, but observed for other Ln 3+ ’s, Gd 3+ . Hence, [GdPc 2 ][C 4 (CN) 6 ] is valence ambiguous as it may be formulated in many ways, e.g., (i) [Gd 3+ Pc 2 ] 0 [C 4 (CN) 6 ] 0 , (ii) [Gd 3+ (Pc •- ) 2 ] + [C 4 (CN) 6 ] •- , (iii) [Gd 3+ (Pc 0 )(Pc 2- )] + [C 4 (CN) 6 ] •- , or their resonance structures. 4d Herein, we report the crystal and electronic structures of 1. GdPc 2 4c and C 4 (CN) 6 8 were prepared by literature methods. 1 was prepared from the reaction of GdPc 2 (24.7.0 mg, 0.0208 mmol) and C 4 (CN) 6 (25.0 mg, 0.122 mmol) each dissolved in 20 mL of PhCl and stirred under nitrogen at room temperature for 4 h. The resulting dark green microcrystalline precipitate was then collected by vacuum filtration. Single crystals were grown in a 20 mL “H-tube” crystallization cell loaded with 7.1 mg of C 4 - (CN) 6 in 0.5 mL of CH 2 Cl 2 and 10 mg of GdPc 2 mixed in 0.5 mL of CH 2 Cl 2 in different ends of the tube. Chlorobenzene was added to the cell very slowly so as not to mix with the starting materials. The diffusion was completed in 3 weeks, and small crystals were observed on the wall of the flask: IR (Nujol, cm -1 ) ν CN 2185 (m), 2155 (m), 2071 (w). The presence of isolated [C 4 (CN) 6 ] •- was confirmed by characteristic shifts in the ν CN absorptions 2185, 2155, and 2071 cm -1 , 9 while [Gd 3+ Pc 2 ] + was confirmed by IR spectroscopy with a characteristic absorptions band at 1319 cm -1 . The latter absorption is lower than that of other cationic phthalocyanine radicals, e.g., [Co II Pc •- ] + (1358 cm -1 ), [Ni II Pc •- ] + (1356 cm -1 ), and [H 2 Pc • ] + (1365 cm -1 ), but consistent with the neutral Ln III (Pc 2- )(Pc •- ) radicals that range from 1315 to 1320 cm -1 , 10 suggesting the presence of both Pc 2- and Pc •- . The structure of [GdPc 2 ][C 4 (CN) 6 ]‚2PhCl 11 consists of isolated [GdPc 2 ] + , [C 4 (CN) 6 ] •- , and two PhCl solvates, Figure 1. The Gd-N bond distances average 2.424 Å, and all the bond distances * Author to whom correspondence should be addressed. † University of Utah. ‡ Osaka University. (1) Phthalocyanine Research and Applications; Thomas, A. L., Ed.; CRC Press: Boca Raton, FL, 1990. The Phthalocyanines; Moser, F. H., Thomas, A. L., Eds.; CRC Press: Boca Raton, FL, 1983; Vols. 1 and 2. Phthalocyanines: Properties and Application. Phthalocyanine-Based molecular Electronic DeVices; Lever, A. P. B., Leznoff, C. C., Eds.; VCH Publishers: New York, 1989 (Vol. 1), 1993 (Vols. 2 and 3), 1996 (Vol. 4). (2) (a) Iwase, A.; Harnoode, C.; Kameda, Y. J. Alloys Compd. 1993, 192, 280. (b) Riou, M. T.; Auregan, M.; Clarisse, C. J. Electroanal. Chem. 1985, 187, 349. (c) Kirin, I.; Moskalev, P.; Makashev, Y. Russ. J. Inorg. Chem. 1965, 10, 1065. (d) Kasuga, K.; Ando, M.; Morimoto, H.; Isa, M. Chem. Lett. 1986, 1095. (3) (a) Hanack, M.; Lang, M. AdV. Mater. 1994, 6, 819. (b) Hanack, M. Macromol. Symp. 1994, 80, 83. (c) Simon, J.; Bassoul, P. Phthalocya- nines: Properties and Application. Phthalocyanine-Based Molecular Electronic DeVices; Lever, A. P. B., Leznoff, C. C., Eds.; VCH Publishers: New York, 1993; Vol. 3, p 119. (4) (a) Andre, J.-J.; Holczer, K.; Petit, P.; Riou, M.-T.; Clarisse, C.; Even, R.; Fourmigue, M.; Simon, J. Chem. Phys. Lett. 1985, 115, 463. (b) Tomilova, L. G.; Chernykh, E. V.; Ioffe, N. T.; Luk’yanets, E. A. Zh. Obshch. Khim. 1983, 53, 2594. (c) Chang, A. T.; Marchon, J.-C. Inorg. Chim. Acta 1981, 53, L241. (d) Trojan, K.; Kendall, T.; Kepler, L.; Hatfield, W. E. Inorg. Chim. Acta 1992, 198-200, 795. (5) (a) Haghighi, H. S.; Teske, C. L.; Homborg, H. Z. Anorg. Allg. Chem. 1992, 602, 73. (b) Ostendorp, G.; Rotter, H. W.; Homborg, H. Z. Naturforsch., B 1996, 51, 567. (6) Rosseau, R.; Aroca, R.; Rodriguez-Mendez, M. L. J. Mol. Struct. 1995, 356, 49. (7) (a) Miller, J. S.; Calabrese, J. C.; Dixon, D. A.; Epstein, A. J.; Bigelow, R. W.; Zhang, J. H.; Reiff, W. M. J. Am. Chem. Soc. 1987, 109, 769. (b) Miller, J. S.; Calabrese, J. C.; Dixon, D. A.; Epstein, A. J.; Bigelow, R. W.; Zhang, J. H.; Reiff, W. M. J. Chem. Soc., Chem. Commun. 1986, 1026. (c) Chittipeddi, S.; Cromack, K. R.; Miller, J. S.; Epstein, A. J. Phys. ReV. Lett. 1987, 22, 2695. (8) (a) Webster, O. W. J. Am. Chem. Soc. 1962, 84, 3370. (b) Ward, M. D. Electroanal. Chem. 1989, 16, 182. (9) Miller, J. S.; Calabrese, J.; Dixon, D. J. Phys. Chem. 1991, 95, 3139. (10) Yakushi, K.; Ida, T.; Ugawa, A. J. Phys. Chem. 1991, 95, 7636. 3654 Inorg. Chem. 2001, 40, 3654-3655 10.1021/ic010187a CCC: $20.00 © 2001 American Chemical Society Published on Web 06/16/2001