Spacers-directed structural diversity of Co(II)/Zn(II) complexes based on S-/O-bridged dipyridylamides: electrochemical, fluorescent recognition behavior and photocatalytic properties

<p>To investigate the effect of the spacers of S-/O-bridged dipyridylamides on the structures of Co(II)/Zn(II) complexes, [Co(L¹)(chda)]·1.5H₂O (<b>CP1</b>), [Co(L²)(chda)] (<b>CP2</b>), [Zn(L¹)(hip)]·DMA·2H₂O (<b>CP3</b>), and [Zn(L²)(hip)]·2.8H₂O (<b>CP4</b>) [L¹ = <i>N,N′</i>-bis(pyridine-3-yl)thiophene-2,5-dicarboxamide, H₂chda = <i>trans</i>-1,4-cyclohexanedicarboxylic acid, L² = <i>N,N′</i>-bis(pyridine-3-yl)-4,4′-oxybis(benzoic) dicarboxamide, H₂hi<i>p</i> = 5-hydroxyisophthalic acid, DMA = <i>N,N</i>-dimethylacetamide], have been solvothermally synthesized. X-ray single-crystal diffraction shows that <b>CP1</b> is a 2-D 3,5-connected network based on Co-L¹ linear chains and (Co-chda)₂ double chains. <b>CP2</b> features a 1-D structure derived from 1-D wave-like (Co-chda)₂ double chains decorated by terminal L² ligands. <b>CP3</b> and <b>CP4</b> show wave-like (4,4) networks constructed by 1-D Zn-L¹ zigzag and Zn-hip zigzag (for <b>CP3</b>)/linear (for <b>CP4</b>) chains. The effect of the spacers of S-/O-bridged dipyridylamides on the structures of the title complexes was discussed. Electrochemical behaviors of <b>CP1</b>–<b>CP2</b> and solid-state luminescent properties of <b>CP3</b>–<b>CP4</b> were studied. The luminescence investigations show that <b>CP3</b> and <b>CP4</b> are recycled fluorescent probes for environmentally relevant Fe³⁺ ions. The photocatalytic properties for the degradation of methylene blue (MB) under ultraviolet light irradiation of <b>CP3</b>–<b>CP4</b> and the recyclable materials after fluorescent sensing Fe³⁺ ions (named <b>CP3</b>@Fe³⁺ and <b>CP4</b>@Fe³⁺) have also been investigated.</p