Three Proton‐Conductors Based on Keggin‐Type Polyoxometalates Well‐Arranged in the Networks of Dinuclear‐Cu(II)‐Mixed‐Organic‐Ligand Clusters

Abstract Three proton‐conductors, [Cu(5‐H 2 L)(IN)(H 2 O)] 2 H 2 [SiW 12 O 40 ] ⋅ 2CH 3 CN ⋅ 2.5H 2 O ( 1 ), [Cu(4‐HL)(HIN)(H 2 O)] 2 H 2 [SiW 12 O 40 ] ⋅ 7H 2 O ( 2 ) and [Cu(4‐HL)(HIN)(CH 3 CN)] 2 [HIN] 2 H 4 [PMo 12 O 40 ] 2 ⋅ 2CH 3 CN ⋅ 12H 2 O ( 3 ) (where 5‐H 2 L/4‐H 2 L is 5,5’/4,4’‐bis(hydroxymethyl)‐2,2’‐bipyridine and HIN is isonicotinic acid), were synthesized at room temperature. Interestingly, three dinuclear‐Cu(II)‐mixed‐organic‐ligand clusters, [Cu(5‐H 2 L)(IN)(H 2 O)] 2 2+ cluster for 1 , [Cu(4‐HL)(HIN)(H 2 O)] 2 2+ for 2 and [Cu(4‐HL)(HIN)(CH 3 CN)] 2 2+ for 3 , are in situ synthesized under the coexistence of Keggin‐type polyoxometalates. More interestingly, in 1 – 3 , the global Keggin‐type anions are well‐arranged in the hydrogen‐bonding networks of double‐Cu(II)‐mixed‐organic‐ligand clusters to give different spatial arrangement patterns. The [SiW 12 O 40 ] 4− anions in 1 display two dimensional layer pattern. The [SiW 12 O 40 ] 4− anions in 2 act as single bidentate O,O bridge ligands. The [PMo 12 O 40 ] 3− anions in 3 form the pair pattern. The AC impedance measurement results reveal 3 gives a high conductivity value over 10 −3 ∼10 −2 S ⋅ cm −1 in a wide temperature range from 25 to 100 °C under a wide relative humidity range from 35 to 98 %, while 1 and 2 give a middle conductivity value over 10 −5 ∼10 −4 S ⋅ cm −1 under the same conditions.