Coordinative Networking of Thiacalix[4]-bis-monothiacrown-5 with Hard, Borderline, and Soft Metal Salts via Exo- and Endo/Exo-Coordination

Coordinative networks of thiacalix[4]-bis-monothiacrown-5 (L) whose infinite structures span from one (1D) to three dimensions (3D) with hard (K+), borderline (Cd2+), and soft (Cu+, Hg2+) metal salts are reported. First, mercury(II) salts afforded straight and zigzag 1D coordination polymers of type [(Hg2X4)(L)]n (1: X = Cl and 2: X = SCN), respectively, with an L-Hg2X4-L-Hg2X4 pattern. When cadmium(II) salts (CdX2) (3: X = Br and 4: X = I) were used, the bromo complex 3 exhibited an infinite 2D structure with square lattice (sql) topology, in which trilooped Cd4Br8 cluster acts as a four-connected node. In contrast, the iodo complex 4 showed a 1D polymeric chain similar to 1. A mixture of KI and CdI2 gave an exceptional discrete complex of type {[(K2L)CdI3]2[K2L](CdI4)2·2CH3CN} (5) with five separated parts involving two identical endo/exocyclic heteronuclear complex units. Interestingly, the CuI complexation yielded a mixture of two supramolecular isomers (6 and 7) of type [(Cu4I4)(L)2]n, each of which was separated with the naked eye under a UV lamp due to their drastically different photoluminescence properties; isomer 6 is emissive while isomer 7 is nonemissive. Isomer 6 features an infinite 3D network with threefold interpenetrated diamodoid (dia) topology in which Cu4I4 cubane tetramers act as 4-connected nodes, while isomer 7 is a non-interpenetrated 2D network with sql topology incorporating Cu4I4 stepped cubane tetramers as 4-connected nodes. Consequently, the borderline and soft metal ions bind to the S-donor on the O4S1-crown loop in an exocyclic mode to form low to high dimensional coordinative networks, with S-bridges in the thiacalix rim remaining uncoordinated mainly because of the weak basicity and rigid conformation. This work also demonstrates the supramolecular isomers incorporating two types of Cu4I4 tetramers which exhibit different photophysical properties as a good example not only for the crystal engineering of the exocoordinated networking but also for the structure–function relationship.