Functional group induced structural diversities and photocatalytic, magnetic and luminescence sensing properties of four cobalt(ii) coordination polymers based on 1,3,5-tris(2-methylimidazol-1-yl)benzene

Abstract

Based on the designed tripodal linker 1,3,5-tris(2-methylimidazol-1-yl)benzene (timb), four cobalt(II) coordination polymers, {[Co₄(timb)₂(Br–IPA)₄]·5H₂O}_n (1), {[Co(timb)_0.5(NH₂–IPA)]·4H₂O}_n (2), {[Co₅(timb)₄(OH–IPA)₄]·2NO₃·2DMA·2H₂O}_n (3), and {[Co₃(timb)₂(SO₃–IPA)₂(H₂O)₂]·8H₂O}_n (4), have been obtained by adjusting the meta-functional groups of isophthalic acid (H₂IPA). CP 1 displays an unprecedented 3D 3-nodal (3,4,8)-connected net with the point (Schlafli) symbol {4²·6⁴}{4²·6}₂{4⁶·6¹⁴·7⁴·8³·9} based on trinuclear {Co₃(COO)₆} SBUs. CP 2 shows an interesting 2D (3,4)-connected {6³}{6⁶} bilayer with ABAB packing. CP 3 is a 2D 6-nodal (3,3,3,4,4,4)-connected sheet with the point (Schlafli) symbol {4·5²}{4·5³·7²}₂{4²·5²·6·7}₃{4³}{5³}₂. CP 4 exhibits a 2D + 2D → 3D interpenetrating net based on the 2D (3,4)-connected {6³}{6⁶} bilayer structure. CPs 1–4 possess excellent luminescence sensing properties for Fe³⁺ and Cr₂O₇²⁻ ions in aqueous solution with high sensitivity and selectivity. Besides, the magnetic properties as well as the photocatalytic activities for the degradation of methylene blue (MB) of CPs 1–4 under visible light have been investigated.