From isostructural to hetero-structural one-dimensional coordination polymers adjusted by changing the ligand substituent group from pyrazine to furan

Abstract

A new ligand, 4-(4-carboxyphenyl)-6-(pyrazin-2-yl)picolinic acid (H₂L1), was used to construct four isostructural one-dimensional (1 D) zig-zag chain coordination polymers ([M(L1)(H₂O)₂]·3H₂O, M = Mn (1), Co (2), Cd (3) and Zn (4)). Moreover, when changing the ligand substituent group from pyrazine ring to furan ring, another new ligand, 4-(4-carboxyphenyl)-6-(furan-2-yl)picolinic acid (H₂L2), was synthesized. Based on H₂L2, different structural 1 D coordination polymers, ([Mn(L2)(H₂O)₂] (5) and [Ni(L2)(H₂O)₂]·H₂O (6)), have been obtained under the same solvothermal conditions as for the syntheses of isostructural 1–4. Interestingly, only through changing the ligand substituent group, the 1 D isostructural zig-zag chain (1–4) was adjusted to a 1 D molecular box chain (5) and 1 D linear chain (6), which should be ascribed to ligand substituent group effects. The various 1 D chain structures originate from the types of ligand substituent group: the substituent group with a pyrazine ring only yields isostructural coordination polymers 1–4, whereas the substituent group with a furan ring can construct different structural coordination polymers, such as a 1 D molecular box chain (5) or a 1 D linear chain (6). The photoluminescent properties of all coordination polymers were also examined.

Keywords:

• Picolinic acid derivatives
• coordination polymers
• ligand substituent group effects
• pyrazine ring
• furan ring
• photoluminescence

Acknowledgements

The authors are grateful to Dr. S.M. Zhou (HFNL, USTC) for the determination of the crystal structure.

Disclosure statement

No potential conflict of interest was reported by the authors.