New 3,5-bis(3,4-dicarboxyphenoxy)benzoic acid-appended Mn(ii) coordination polymers: synthesis, characterization and antibiotic photodegradation properties

Abstract

Coordination polymers are a sub-class of coordination complexes that possess unique opto-electronic properties and hence can be utilized for a wide range of applications such as sensing and photocatalysis. Herein, four new coordination polymers (CPs) with formula [Mn₂(HL)(NMP)(H₂O)₂]_n (1), [Mn₂(HL)(DMA)₂(H₂O)·2DMA]_n (2), [Mn(H₃L)(H₂O)₂]_n (3) and [Mn(H₃L)(H₂O)(4,4′-bipy)]_n (4) (H₅L = 3,5-bis(3,4-dicarboxyphenoxy) benzoic acid and NMP = N-methyl pyrrolidone) were synthesized under hydrothermal conditions and characterized. The single-crystal X-ray analysis revealed a distorted octahedral geometry around Mn(II) in these CPs and that they form an extended hydrogen bonding and π⋯π stacking interaction-assisted network. Thermogravimetric studies revealed that the CPs, 1, 2, 3 and 4, have variable thermal stability in the range of 82–194 °C. All four complexes exhibited optical semiconducting behavior and hence were used as photocatalysts for the photodecomposition of antibiotics, including chloramphenicol (CAP), nitrofurazone (NFZ), ornidazole (ODZ), oxytetracycline (OXY) and sulfamethoxazole (SMT). Among the CPs, CP 2 exhibited an impressive 91.93% degradation of NFZ within 60 min. The plausible photocatalytic mechanism was explained with the assistance of Hirshfeld surface analysis.