SUPPORTING INFORMATION (revised)

Transcription

1 S 1 SUPPORTING INFORMATION (revised) A 60-Metal Sodalite Cage Constructed by 24 Vertex-sharing [Er 4 (µ 3 -OH) 4 ] Cubanes Xiang-Jian Kong, a,b Yinglan Wu, a La-Sheng Long, b, * Lan-Sun Zheng, b and Zhiping Zheng a, * a Department of Chemistry, University of Arizona, Tucson, Arizona 85721, b College of Chemistry and Chemical Engineering, Xiamen University, Xiamen , China General Considerations. All reagents were of commercial origin and were used as received. Aqueous solutions of lanthanide perchlorates were prepared by digesting lanthanide oxides in concentrated perchloric. A suitable concentration was achieved by dilution of the concentrated solution with deionized water. Compound 1. L-Threonine (0.238 g, 2.0 mmol) and NaBr (0.103 g, 1 mmol) were added to an 8 ml aqueous solution of Er(ClO 4 ) 3 (1.0 M). The resulting pinkish solution mixture was stirred at about 80 o C while a fershly prepared aqueous solution of NaOH (1.0 M) was added slowly to the point of incipient but permanent precipitation (ph = 6). The mixture was filtered while hot, and the supernatant was covered with Parafilm and allowed to stand on a gradually cooling heating plate. Pink crystals appeared in two days. The crystals were collected by filtration and dried under dynamic vacuum at room temperature for 24 hrs. Yield: 45.0% (based on L-Threonine). Anal. [Er 60 (L-Thre) 34 (CO 3 ) 8 (µ 3 -OH) 96 (µ 2 -O) 2 (H 2 O) 18 ]Br 12 (ClO 4 ) 18 (H 2 O) 40 (Er 60 C 144 N 34 O 354 H 484 Br 12 Cl 18, FW = based on 40 water molecules of hydration): C, 8.65%; H, 2.44%; N, 2.38%; Cl, 3.19%; Br, 4.80%. Found: C, 8.73%; H, 2.37%; N, 2.39%, Cl, 3.20; Br, 4.70%. Crystal data for 1: Pink, block-shaped crystal, orthorhombic, space group C222(1) with a = (3) Ǻ, b = (5) Ǻ, c = (5) Ǻ, V = 58891(11) Ǻ 3, Z = 4, reflections collected on a Bruke SMART CCD with monochromatic Mo Kα radiation (λ = Ǻ), R 1 = (I>2σ(I)), wr 2 = (all data). Compound 2 was prepared by adopting otherwise identical procedures as compound 1 using D- threonine as the hydrolysis-limiting ligands. Anal. [Er 60 (D-Thre) 34 (CO 3 ) 8 (µ 3 -OH) 96 (µ 2 - O) 2 (H 2 O) 18 ]Br 12 (ClO 4 ) 18 (H 2 O) 40 (Er 60 C 144 N 34 O 354 H 484 Br 12 Cl 18, FW = based on 40 water molecules of hydration): C, 8.65%; H, 2.44%; N, 2.38%. Found: C, 8.70%; H, 2.35%; N,

2 S %. Crystal data for 2: Pink, block-shaped crystal, orthorhombic, space group C222(1) with a = (3)Ǻ, b = (6) Ǻ, c = (5) Ǻ, V = (12) Ǻ 3, Z = 4, reflections, R 1 = (I>2σ(I)), wr 2 = (all data). Compound 3 was prepared by adopting otherwise identical procedures as compound 1 using Ho(ClO 4 ) 3 in place of Er(ClO 4 ) 3. Anal. [Ho 60 (L-Thre) 34 (CO 3 ) 8 (µ 3 -OH) 96 (µ 2 - O) 2 (H 2 O) 18 ]Br 12 (ClO 4 ) 18 (H 2 O) 60 (Ho 60 C 144 N 34 O 374 H 524 Br 12 Cl 18, FW = based on 60 water molecules of hydration): C, 8.56%; H, 2.61%; N, 2.36%. Found: C, 8.27%; H, 2.29%; N, 2.31%. Crystal data for 3: Pink, block-shaped crystal, orthorhombic, space group C222(1) with a = (6)Ǻ, b = (9) Ǻ, c = (10) Ǻ, V = 59301(21) Ǻ 3, Z = 4, reflections, R 1 = (I>2σ(I)), wr 2 = (all data). Compound 4 was prepared by adopting otherwise identical procedures as compound 1 using Y(ClO 4 ) 3 in place of Er(ClO 4 ) 3. Anal. [Y 60 (L-Thre) 34 (CO 3 ) 8 (µ 3 -OH) 96 (µ 2 - O) 2 (H 2 O) 18 ]Br 12 (ClO 4 ) 18 (H 2 O) 60 (Y 60 C 144 N 34 O 354 H 484 Br 12 Cl 18, FW = based on 40 water molecules of hydration): C, 11.31%; H,3.19%; N, 3.11%. Found: C, 11.18%; H, 3.00%; N, 3.13%. Crystal data for 4: Colorless, block-shaped crystal, orthorhombic, space group C222(1) with a = (10)Ǻ, b = (15) Ǻ, c = (16) Ǻ, V = 58010(3) Ǻ 3, Z = 4, reflections, R 1 = (I>2σ(I)), wr 2 = (all data). Detailed structural description of cluster complex 1. The cationic cluster complex of 1 is structurally shown in Figure S1. Overall it is a cluster core of 60 Er atoms (Figure S1, b) being encapsulated by a coordination sphere formed by 34 threonine ligands (Figure S1, a). A better way of appreciating the regular core structure is to divide the 60 Er atoms into 24 cubane-like [Er 4 (µ 3 -OH) 4 ] 8+ units. Three metal atoms of the cubane are each shared by a different cubane units. This accounts for the total of 60 metal atoms [24 cubanes x 4 Er atoms each = 96 Er atoms, of which, 36 are shared (3 shared Er atoms/cubane x 24 cubanes x ½ = 36 Er atoms)]. The 60 (96-36) Er atoms are connected by triply bridging hydroxo groups in each cubane. In addition, the 8 hexagons of the cubanes each feature a templating carbonate ion (Figure S1, b).

3 S 3 Figure S1. (a) Crystal structure of the cationic cluster complex [Er60(L-thre)34(µ6-CO3)8(µ3OH)96(µ2-O)2(H2O)18]30+; (b) the structure of the cluster core showing only the metal atoms and their coordinating atom in the sodalite-like cage. The yellow-colored sphere is meant for the illustration of the space inside the cage. Figure S2. From left to right: The [Er4(µ3-OH)4] cubane units by sharing vertices are assembled into hexagons and squares, which in turn, are organized into a sodalite cage structure. The hexagons and squares are shown schematically shown in purple in the cluster core structure. A sodalite cage in Zeolite A is highlighted (red circle).

4 S 4 The threonine ligands display three different coordination modes, as shown schematically in Figure S3 (a-c). These chelating/bridging interactions help stabilize the vertex-sharing cubanes. Figure S3. Three different coordination modes of the threonine ligand in compound 1 and the local structure of the ligand coordination to the [Er 4 (µ 3 -OH) 4 ] cubane units. Figure S4. Metal atoms of the 60-metal cluster core can be divided into two distinct polyhedral shells with an outer, truncated octahedron shell of 24 metal atoms encapsulating an inner, doubly truncated octahedral shell of 36 metal atoms. The latter is interestingly a nonstandard convex polyhedron composed of 24 triangles, 6 squares, and 8 hexagons, not belonging to any one of the Platonic, Archimedean, or Johnson solids.

5 S 5 Alternatively, this 60-metal core can be viewed as a fascinating double-shell structure with an outer shell of 24 unshared Er atoms encapsulating an inner 36-metal shell (Figure S4). The coordination spheres of these metal atoms are shown in Figure S5. The 24 outer-shell Er atoms form a 1.8-nm (diameter) cage (Figure S5, a). The metal atoms are connected by the carboxylate and amino groups of the threonine ligands as well as aqua ligands. The separations between neighboring Er atoms range from (4) to (5) Ǻ. The coordination geometry of the nonacoordinate metal atoms can be best described as a tri-capped trigonal prism. Each of the inner-shell Er atoms is octacoordinate, with contributions by six µ 3 -OH groups and two CO 2-3 or one CO 2-3 and one threonine carboxylate O atom (Figure S5, b). The coordination geometry can be described as a bicapped trigonal prism. The cage possesses a nanoscopic interior with an Er Er separation of 1.2 nm, large enough to accommodate six Br - ions; there are also 6 Br - as counter anions. Figure S5. Coordination spheres of the metal atoms in (a) the outer and (b) inner shell of the double-shell core structure.