Isomeric phenylenediacetates as modular tectons for a series of ZnII/CdII coordination polymers incorporating flexible bis(imidazole) co-ligands

Abstract

This work presents a systematic investigation of the reactions of phenylenediacetate isomers with Zn^II/Cd^II salts in the presence of different flexible bis(imidazole) co-ligands. Seven new coordination polymers, namely, {Zn(o-pda)(biim-3)}_n (1), {[Cd(o-pda) (biim-5)]·H₂O}_n (2), {[Zn(m-pda) (biim-4)]·3H₂O}_n (3), {Cd(m-pda)(biim-6)_0.5(H₂O)}_n (4), {[Cd(p-pda) (biim-3)]·H₂O}_n (5), {Zn(p-pda) (biim-4)}_n (6), and {[Cd(p-pda)(biim-6)]·H₂O}_n (7) [o/m/p-pda = 1,2/1,3/1,4-phenylenediacetate acid, biim-3 = 1,1′-(1,3-propanedidyl)bis-(imidazole), biim-4 = 1,1′-(1,4- butanedidyl)bis-(imidazole), biim-5 = 1,1′-(1,5-pentanedidyl)bis-(imidazole), biim-6 = 1,1′-(1,6- hexanedidyl)bis-(imidazole)], have been synthesized and characterized by elemental analysis, IR, TG, single crystal X-ray structural determination and powder X-ray diffraction. Complex 1 shows an uncommon 1D achiral chain structure, which contains the right-handed and left-handed helical chains decorated with two zigzag arms. Complexes 2, 3, and 5 display the similar 2D undulating sql layer structures. Interestingly, in 3, the 1D water tape T4(2)6(2), which contains the hexameric water cluster (H₂O)₆ with a chair-like conformation, assembles these 2D layers to form a 3D framework. In 5, the 2D adjacent hetero-helical layers stack in an –ABĀ– pattern to generate a 3D mesomeric framework. Complex 4 manifests a 2D (3,4)-connected V₂O₅-type network. Differently from 1–5, complex 6 features a 3D 5-fold interpenetrated dia network, and complex 7 exhibits a 3D (3,5)-connected (4²·6)(4²·6⁵·8³)-fsc framework. A structural comparison of these polymers suggests that different dispositions of the carboxyl sites, diversiform configurations and binding fashions of phenylenediacetate isomers play important roles in the construction of resulting architectures for 1–7, which can also be well regulated by different flexible bis-(imidazole) co-ligands. Moreover, solid-state properties such as thermal stabilities and luminescent properties of 1–7 were also investigated.