Lanthanide Coordination Networks Based on Diamantane‐4,9‐Diphosphonic Acid

Four new Ln‐based (Ln = Eu, Gd, Er) coordination networks, {[EuL 1.5 (H 2 O) 4 ]·H 2 O} n and {[LnL 1.5 (H 2 O)]·H 2 O} n (Ln = Eu, Gd, Er), were synthesized using the precursor diamantane‐4,9‐bis(dichlorophosphoryl) (Diam(POCl 2 ) 2 ) to form in situ the linker diamantane‐4,9‐bis(hydrogenphosphonate) (L = Diam(PO 3 H) 2 2– ) with singly deprotonated phosphonate groups. These coordination networks represent the first reported examples of diamantane‐phosphonate networks. The combination of Ln 3+ ions and Diam(PO 3 H) 2 2– resulted in the formation of doubly ‐PO 3 H – bridged Ln chains. These chains are interconnected by the diamantane moiety of the diamantane‐4,9‐bis(hydrogenphosphonate) linker, forming 2D (Eu) or 3D (Eu, Gd, Er) networks. In the 3D networks, Eu 3+ , Gd 3+ , and Er 3+ exhibit an uncommon coordination number of 6, from five phosphonate groups and one aqua ligand. This may be due to the constraints of the 3D network but at the same time shows the adaptability of Ln 3+ ions to coordination constraints crucial for the formation of the 3D phosphonate frameworks.