Interpenetrated networks from a novel nanometer-sized pseudopeptidic ligand, bridging water, and transition metal ions with cds topology{ George E. Kostakis, ab Luigi Casella, a Nick Hadjiliadis,* b Enrico Monzani, a Nikolaos Kourkoumelis c and John C. Plakatouras* b Received (in Cambridge, UK) 24th February 2005, Accepted 23rd May 2005 First published as an Advance Article on the web 21st June 2005 DOI: 10.1039/b502788h The combination of a new pseudopeptidic ligand, transition metal ions, and bridging water molecules results in the formation of [M(m-TBG)(m-H 2 O)(H 2 O) 2 ] ? 2H 2 O (M: Cu, Co and H 2 TBG: terephthaloylbisglycine); both compounds show rare two-fold interpenetrated three-dimensional cds-nets and reversible loss of coordinated and lattice water molecules. In recent years there has been extensive interest in metal–organic polymer chemistry due to the variety of the composition and topology of the produced compounds, and also to their interesting functional properties and potential applications. The development of rational synthetic routes by self-assembly has afforded an important number of coordination polymers with specific topologies. 1 Metal–ligand coordination has been well used in the directed assembly of extended porous metal–organic networks. The ability to control the design of coordination networks arises from the management of the coupling of the coordination properties of individual metal ions and ligand functionality. One of the key points for such studies is the design or choice of components that organize themselves into desired patterns with useful functions. Considerable use has been made of the rigid linear bridging ligand 1,4-benzenedicarboxylic (terephthalic) acid and also of related ligands in which various spacer groups connect carboxylic pairs. 2 Our synthetic strategy is to introduce flexibility on the aromatic rigid scaffold in addition to groups that would allow extra stabilizing interactions and eventually to build up a higher dimensional motif through metal–ligand interactions. Our first approach is terephthaloylbisglycine, 3a which is longer than terephthalate, the carboxylate groups are reasonably free to rotate and the amide bond can be the source of hydrogen bonds that would be able to stabilize a network. Furthermore, bearing in mind that aminoacids and peptides provide the glycine chelate ring for coordination to metal ions, we could expect a bis-chelating bridging behavior that could lead to an unprecedented polymer. The reaction between equivalent amounts of the corresponding metal nitrate and terephthaloylbisglycine (H 2 TBG) in water, at r.t., proceeds smoothly and produces crystalline solids formulated as [M(m-TBG)(m-H 2 O)(H 2 O) 2 ]?2H 2 O [M: Cu (1), Co (2)]. 3b Both compounds were characterized crystallographically and they were found to belong to the P2/a space group with one half molecule in the asymmetric unit.{ A water molecule is included, and it is connected to the network, eventually formed, with four hydrogen bonds. Each metal ion is coordinated, in a rather regular octahedron (with larger Jahn–Teller distortion in the case of Cu, in 1), to two oxygen atoms belonging to two monodentate carboxylates of two different TBG ligands, two bridging and two terminal water molecules, in trans positions (mean M–O distances, 1: 2.092, 2: 2.102 A ˚ ). The differences in M–O bonds are also reflecting the two different kinds of H 2 O molecules in the coordination sphere and can preclude the existence of hydroxide species. The system’s coordination is presented in Fig. 1. The structure of [M(m-TBG)(m-H 2 O)(H 2 O) 2 ] is constructed from one- dimensional chains interlinked through bridging water and TBG groups into an open framework, three-dimensional structure. As shown in Fig. 2, the chains consist of square planar nodes (the terminal water molecules are not counted) linked through TBG ligands. There are two different metal–metal distances: (a) a short one for the water bridge (1: 4.0878(8), 2: 3.986(2) A ˚ ) and (b) a long one for the TBG bridge (1: 17.207(4), 2: 17.438(9) A ˚ ). The structure propagates in one direction as {M(TBG)} chains through the bridging terephthaloylbisglycinate ligands. These linear chains are linked in turn through a {M(H 2 O)} 2+ undulating chain. Adjacent {M(TBG)} chains cross at an angle of y48u to produce the grid pattern seen in projection along c. The water bridges propagate along the a axis, while the TBG bridges propagate alternately parallel to the two diagonal directions of the bc face forming this way a cds network. 4 The rhombic channels shown in Fig. 3, exhibit a 68-atom connect to generate a cavity of y50 A ˚ 2 cross section area. (Fig. S1) a Dipartimento di Chimica Generale, Universita ´ di Pavia, Via Taramelli 12, 27100, Pavia, Italy b Department of Chemistry, University of Ioannina, 451 10, Ioannina, Greece. E-mail: iplakatu@cc.uoi.gr c Department of Physics, University of Ioannina, 451 10, Ioannina, Greece { Electronic supplementary information (ESI) available: Figures, H-bond Tables for the structures, vibrational, electronic and EPR spectra, thermal analyses, XRPD patterns for original, dehydrated and rehydrated samples and a vrml file with the topological presentation of the structures. See http://dx.doi.org/10.1039/b502788h Fig. 1 The coordination sphere of the Cu atoms and the ligand bonding in 1. 2 has a very similar structure. Selected bond lengths/A ˚ and angles/u, 1: Cu(1)–O(1) 1.987(2), Cu(1)–O(4) 2.291(2), Cu(1)–O(5) 1.998(2); O(1)– Cu(1)–O(4) 93.18(8), O(1)–Cu(1)–O(5) 88.80(10), O(4)–Cu(1)–O(5) 89.71(10); 2: Co(1)–O(1) 2.053(3), Co(1)–O(4) 2.182(2), Co(1)–O(5) 2.069(4); O(1)–Co(1)–O(4) 92.09(13), O(1)–Co(1)–O(5) 89.89(15), O(4)– Co(1)–O(5) 90.10(14). COMMUNICATION www.rsc.org/chemcomm | ChemComm This journal is ß The Royal Society of Chemistry 2005 Chem. Commun., 2005, 3859–3861 | 3859