Two‐Dimensional Divalent Metal Coordination Polymers Containing 3,4′‐Dipyridylketone Tethers: Layer Topology Tuning by Anion Binding Preferences

Slow diffusion of aqueous cobalt thiocyanate or cadmium perchlorate and ethanolic solutions of 3,4′‐dipyridylketone (3,4′‐dpk) generated the coordination polymers {[Co(NCS) 2 (3,4′‐dpk) 2 ]·2H 2 O} n ( 1 ) and {[Cd(H 2 O) 2 (3,4′‐dpk) 2 ](ClO 4 ) 2 ·2H 2 O} n ( 2 ), which were structurally characterized by single‐crystal X‐ray diffraction. The structure of 1 consists of interdigitated neutral [Co(NCS) 2 (3,4′‐dpk) 2 ] n (4,4) rectangular grid coordination polymer layers. However, compound 2 manifests cationic [Cd(H 2 O) 2 (3,4′‐dpk) 2 ] n 2n + two‐dimensional (6,3) herringbone lattices connected through hydrogen bonding mediated by interlamellar unligated perchlorate anions. Upon excitation with ultraviolet radiation, 2 emits blue‐violet light, ascribed to π–π* transitions within the pyridyl rings of the 3,4′‐dpk ligands. Thermal decomposition behavior of 1 is also discussed.