Alkaline‐Earth (Mg–Ba) Coordination Networks Built Around the Tris(dipicolinato)cerate(3 – ) Ion: Highly Hydrated Networks That Survive Dehydration

Alkaline‐earth (AE)/cerium(III)‐based heterometallic coordination compounds of the biologically important ligand dipicolinic acid (dipicH 2 ), namely [Mg(H 2 O) 6 ] 2 [Ce(dipic) 3 ][Ce(dipic) 2 (H 2 O) 3 ] · 2H 2 O ( 1 ), [Ca 3 (H 2 O) 12 Ce 2 (dipic) 6 ] · 6H 2 O ( 2 ), [Sr 3 (H 2 O) 16 Ce 2 (dipic) 6 ] · 4H 2 O ( 3 ) and [Ba 2 (H 2 O) 7 Ce(dipic) 3 NO 3 ] · H 2 O ( 4 ), have been obtained by the reduction of an aqueous solution of (NH 4 ) 2 Ce(NO 3 ) 6 · 6H 2 O in the presence of dipicH 2 and alkaline‐earth oxides or carbonates. This series demonstrates the role of AE ions in controlling the topology of coordination networks based on the [Ce(dipic) 3 ] 3– anion. Compound 1 is a zero‐dimensional ionic compound, the crystal structure of compound 2 is based on a mixed four‐connected 3D network, compound 3 presents ladder‐shaped chains running along a crystallographic axis, and layers of squeezed CeBa 6 pentagonal pyramids interconnected by nitrates generate a mixed five‐ and six‐connected network in 4 . A thermal analysis showed that all four compounds exhibit reversible water‐uptake capacity and the basic nature of the frameworks could be intact up to at least 120 °C.