Structures and photocatalytic properties of two Mn(II)-based coordination polymers

Two isostructural Mn(II)-based coordination polymers, namely, [Mn(L)(biPY)](n) (1) and [Mn-2(L)(2)(phen)(2)](n) (2)1,4-bis (3-carboxylbenzyl)piperazine acid (H2L) have been synthesized by a new flexible ditopic carboxylate and two different ancillary ligands viz. 1,10-phenanthroline (phen) and 2,2'-bipyridine (bipy). The single crystal X-ray diffraction results revealed that compounds 1 and 2 exhibit two-dimensional layered structures containing 36-membered rings based on 8-membered dinuclear Mn(II) units with (3(2).4(4))(3(4).4(6).6(4).6) topology. The phen/bipy groups behave like blades on the two sides of the 2D layers. Both coordination polymers have been used as photocatalyst for the degradation of organic dye methyl violet (MV) under UV light and the plausible photocatalytic mechanism have been addressed using band gap calculations based on density of states (DOS) and partial density of states (pDOS) plot. Additionally, the photodegradation mechanism was further investigated by performing photocatalytic degradation of dye in presence of scavengers such as tertiary butyl alcohol (TBA), benzoquinone (BQ) and ammonium oxalate (AO).