Stepwise Guest Exchange in a Cluster-Supported Three-Dimensional Host Wen-Hua Zhang, † Jian-Ping Lang,* ,†,‡ Yong Zhang, † and Brendan F. Abrahams § School of Chemistry and Chemical Engineering, Suzhou UniVersity, Suzhou 215123, Jiangsu, P. R. China, State Key Laboratory of Coordination Chemistry, Nanjing UniVersity, Nanjing 210093, Jiangsu, P. R. China, and School of Chemistry, UniVersity of Melbourne, ParkVille, Victoria 3010, Australia ReceiVed NoVember 16, 2007; Accepted January 2, 2008 ABSTRACT: Reactions of [Et 4 N] 2 [MoS 4 (CuCN) 2 ] · H 2 O with bis-(4-pyridyl)propane (bpp) and [Cu(MeCN) 4 ][ClO 4 ] in aniline produced [MoS 4 Cu 4 (bpp) 2 (CN) 2 ] · 1.5(aniline) (1a). 1a consists of a new three-dimensional [MoS 4 Cu 4 ]-supported open coordination polymer which has a relatively large channel with a volume of ca. 618 Å 3 per unit cell. 1a underwent a two-step host–guest process in which the aniline molecules residing in its channels could be partly exchanged with MeCN molecules in 3d and then completely with dimethylformamide molecules in a month, forming {[MoS 4 Cu 4 (bpp) 2 (CN) 2 ] · (aniline) · (MeCN)} n (1b) and {[MoS 4 Cu 4 (bpp) 2 (CN) 2 ] · (DMF) · (MeCN)} n (1c), respectively. Interest in open coordination polymers has arisen because of their potential applications in areas such as storage and separation processes, 1 catalysis, 2 drug delivery, 3 and sensor technology. 4 The wide variety of chemical building blocks that may be employed in the generation of open coordination networks offers great scope for tailoring materials to perform specific tasks in regard to host–guest chemistry. The successful generation of stable and robust crystalline networks has allowed investigations of kinetic and thermodynamic factors affecting guest exchange processes. In such processes, it has been shown that secondary bonding interactions such as hydrogen bonding or π-π stacking 5 between host and guest can play a key role. Such interactions often have little effect on the structure of the host but sometimes can cause distortion or rupture of the host framework. 6 Regardless of the extent of host deformation, it is the interaction between host and guest that generally dictates the sorption and desorption processes. Herein we report a stepwise exchange process in which the identity of the resident guest affects the ability of the host to incorporate other guest species. Addition of an aniline solution containing [Et 4 N] 2 [MoS 4 - (CuCN) 2 ] · H 2 O 7 and bis-(4-pyridyl)propane (bpp) to an aniline solution of [Cu(MeCN) 4 ][ClO 4 ] produced a large amount of a powdery red precipitate within a dark-red homogeneous solution. The red solid was filtered off, and the filtrate was left to stand in darkness. After a few days, the solution yielded black prisms of [MoS 4 Cu 4 (bpp) 2 (CN) 2 ] · 1.5(aniline) (1a). 8a Elemental analysis re- vealed that the red powder had the same composition as 1a; however, X-ray powder diffraction (XRPD) (see Supporting Information) indicated that the initial precipitate was amorphous. An X-ray analysis 9 of 1a revealed the formation of a pentanuclear saddle-like [MoS 4 Cu 4 ] core. The asymmetric unit of 1a contains two independent Cu atoms with similar coordination environments. Each Cu center is tetrahedrally coordinated by two µ 3 -S atoms from the tetrahedral [MoS 4 ] 2- moiety, one N atom from a bpp ligand and one C or N atom from a disordered bridging cyanide unit (Figure 1a). Each [MoS 4 Cu 4 ] cluster core is coordinated by four bridging cyanide ions and four bridging bpp ligands. These eight ligands extend to eight crystallographic equivalent clusters, six of which lie at the corners of a trigonal antiprism, while the other two are situated along the midpoints of two opposing triangular edges as indicated in Figure 1b. From a topological perspective, each cluster may be considered as an 8-connecting node in a three-dimensional (3D) network. The connectivity of the network may be understood in terms of two types of intersecting sheets each involving only one type of bridging ligand. If only the cyanide bridges between the clusters are considered then a 2D (4,4) square grid extending in the ac plane is apparent (Figure 2a). Adjacent cyanide sheets are linked by bridging bpp ligands. If only the bpp bridges between clusters are considered then two interwoven two-dimensional (2D) (4,4) networks that extend in the ab plane are formed (Figure 2b). If both types of bridging ligand are taken into account, the result is a single 3D (4 22 6 6 ) network (Figure 3a), which to the best of our knowledge has not been identified before. 10 * To whom correspondence should be addressed. Fax & Tel: Int. code +86 512 65880089. E-mail: jplang@suda.edu.cn. † Suzhou University. ‡ Nanjing University. § University of Melbourne. Figure 1. (a) Part of the polymeric structure of 1a with only one set of atoms for the disordered cyanides shown. (b) The connection of the 8-connecting [MoS 4 Cu 4 ] node to equivalent nodes in 1a. Hydrogen atoms have been omitted for clarity. Figure 2. Perspective view of the repeating units of 1a, showing (a) the [MoS 4 Cu 4 ] clusters are linked by CN ions in the ac plane to form a (4, 4) net; (b) the [MoS 4 Cu 4 ] clusters are linked by bpp ligand in the ab plane to form two interwoven (4, 4) net. CRYSTAL GROWTH & DESIGN 2008 VOL. 8, NO. 2 399–401 10.1021/cg701131t CCC: $40.75  2008 American Chemical Society Published on Web 01/11/2008