The current interest in the crystal engineering of coordination polymer frameworks not only stems from their potential applications in microelectronics, nonlinear optics, porous materials, and catalysis, but also from their intriguing variety of architectures and topologies. [1,2] Up to now, a variety of appealing interpenetrated nets, in which only internal connections are broken to separate individual nets, have been reported and reviewed by Batten and Robson. [3] In contrast, other types of entangled architectures that have recently been described-such as infinite multiple helices, [4] two-dimensional clothlike warp-and-weft sheet structures, [5] interdigitated structures in a gearlike (or tongue-and-groove) fashion, [6] and polythreaded structures with poly-pseudo-rotaxanes [7] -can, in principle, be disentangled without breaking links. Moreover, these entangled nets can lead to synthetic supramolecular arrays with potential applications in asymmetric catalysis, drug-delivery vehicles, and sensor devices.Unfortunately, these species are still rare, as evidenced in a recent review by Ciani and co-workers, [8] and therefore the exploration of new synthetic routes to this class of supramolecular architectures is one of the most challenging issues in current synthetic chemistry. On the other hand, it is wellknown that product topology can often be controlled and modulated by selecting the coordination geometry of the metal ions and the chemical nature of the organic ligands. Usually, long ligands will lead to larger voids that may result in interpenetrated structures, [3] the most outstanding example of which is 1,2-bis(4-pyridyl)ethane (bpe). With this ligand, many beautiful interpenetrated networks of ingenious design have been constructed, ranging from interpenetrating 1D ladders to 3D nets. [9] However, these results do not mean that other types of entangled structures cannot be formed in the presence of long flexible ligands. If another configurational ligand is introduced, it may be possible to gain noninterpenetrating nets by combining different precursors. In this regard, for our synthetic strategy we choose an analogy of bpe, biphenylethene-4,4'-dicarboxylic acid (bpea), whose coordination chemistry, to the best of our knowledge, has not been previously investigated. Due to the replacement of two pyridyl groups by aromatic carboxy groups, bpea will be more flexible than bpe. Therefore, to avoid interpenetration the heterocyclic aromatic ligand 1,10-phenanthroline (phen) was introduced based on the following considerations: 1) The steric hindrance at the metal center will be increased when the bulky aromatic ligand binds to the metal ion; this reduces the dimension of the net formed. Lower dimensional nets are usually less likely to interpenetrate because there are more possible ways to maximize the packing efficiency.[10] 2) Chelating bipyridyl-like ligands may provide recognition sites for p-p stacking interactions to form interesting supramolecular structures.3) The conjugated p systems containing (...
