N-heterocyclic amine-directed structures and properties of two Cu(ii) diphosphonates

摘要

By introducing the second organic N-heterocyclic ligands 4′-(4-pyridyl)-4,2′:6′,4′′-terpyridine (pyterpy) and 4,4′-bipyridyl (4,4′-bipy), two examples of Cu(ii)- diphosphonates, [Cu_3(HL)_2(Hpyterpy)_2] ·2H_2O 1 and [Cu_4(HL)_2(4,4′-bipy) (H_2O)_5] 2 based on 1-hydroxyethylidenediphosphonic acid (H_5L = CH_3C(OH)(PO_3H_2)_2), have been hydrothermally obtained and characterized by powder X-ray diffraction, elemental analysis, IR, TG-DSC. The single-crystal X-ray diffractions reveal that compound 1 has a one-dimensional fishbone-like chain constructed by anions [Cu_3(HL)_2~(2-)]_n while simultaneously organic cations [Hpyterpy~+]_n suspending both sides, and compound 2 exhibits two-dimensional inorganic-organic alternate arrangement layer built from 1-D ladder-like inorganic chain with tetranuclear cluster [Cu_4O_(10)] via 4,4′-bipy linkage. The results of electrochemical measurements indicate half-wave potential of 1 (E_(1/2)~1 = 1.01 V) is less than that of 2 (E _(1/2)~2 = 1.20 V), indicating a good D-A system in ICT for 1. Moreover fluorescent measurements reveal that emission intensity of 1 centered at 422 nm is larger than that of 2 emitted at 420 nm, caused by intraligand π*-π emission state of organic N-heterocyclic amine (λ_(ex) = 233 nm). Magnetism data indicate that compound 1 exhibits ferrimagnetic interactions between metal centers, while compound 2 has antiferromagnetic property.