Porous lanthanide-copper coordination frameworks exhibiting reversible single-crystal-to-single-crystal transformation based on variable coordination number and geometry

Two serial heterometallic Ln-Cu coordination polymers [Ln(2)Cu(NIPH) (4)(H2O) 4]center dot 6H(2)O (Ln =Gd (1a), Nd ( 2a), Sm ( 3a), Eu ( 4a), Tb ( 5a), Dy ( 6a), Ho ( 7a) and Er ( 8a)) and [ Ln2Cu( NIPH) 4( H2O) 2] ( Ln = Gd (1b), Nd (2b), Sm (3b), Eu (4b), Tb(5b), Dy (6b), Ho (7b) and Er (8b) ( NIPH = 5- nitroisophthalate) have been successfully synthesized and exhibit reversible single-crystal-to- single-crystal transformation behavior based on a dehydration and rehydration process involving coordinated and uncoordinated water molecules. The coordination polymers 1a-8a and 1b-8b belong to two sets of isomorphous coordination frameworks respectively; their 3D frameworks are constructed by different heterometallic polynuclear chains. For the serial crystals 1a-8a, the Ln(3+) and Cu2+ ions are 8-coordinate and 4-coordinate respectively. While for the other serial crystals, 1b-8b, the Ln(3+) and Cu2+ ions are 9-coordinate and 6-coordinate respectively. La3+, Ce3+ and Pr3+ were also employed to construct Ln-Cu coordination frameworks [LaCu( NIPH)(2)( HNIPH)( H2O)(2)]center dot 2H(2)O (La- 1), [La2Cu(NIPH)(4)(H2O)(2)] (La-2), [Ce2Cu( NIPH)(4)(H2O)(6)] (Ce-1) and [Pr2Cu(NIPH)(4)( H2O)(4)]center dot 6H(2)O ( Pr- a), which do not display the crystal-to- crystal transformation characteristic.