Transition metal complex directed lead bromides with tunable structures and visible light driven photocatalytic properties

Dalton Trans. 2016 Dec 6;45(48):19389-19398. doi: 10.1039/c6dt03601e.

Abstract

With similar transition metal (TM) complex cations as structural directing agents (SDAs), six new hybrid lead bromides were synthesized and structurally characterized as [Co(2,2-bipy)3]2{[Co(2,2-bipy)]3Pb7Br24} (1), [Co(2,2-bipy)2Br]PbBr3 (2), [TM(phen)3]Pb2Br6 (TM = Co (3) and Ni (4)), [Co(2,2-bipy)3]Pb3Br9 (5) and [Co(2,2-bipy)3]Pb5Br13·CH3CN (6) with distinct structural types from zero-dimensional (0D) unit, one-dimensional (1D) chain to two-dimensional (2D) layer. Compound 1 contains the 0D {[Co(bipy)]3Pb7Br24}4- units built from the [Pb7Br24] ring attached by three unsaturated [Co(2,2-bipy)]2+ complexes via Co-Br bonds. Under the direction actions of different SDAs, compounds 2 and 3-4 contain two different types of [Pb2Br6]4- chains based on the same octahedral [PbBr6] units but with distinct connecting manners, respectively. Using the same [Co(2,2-bipy)3]3+ as SDA, compound 5 reveals a 1D [Pb3Br9]3- double chain, whereas compound 6 features a 2D complex [Pb5Br13]3- layer. The UV/vis diffuse-reflectance measurements reveal that the title compounds feature tunable band gaps of 1.70-2.29 eV. Under the visible light irradiation, sample 6 exhibits efficient and stable photocatalytic degradation activities over organic pollutants, which mainly originates from the multi-electronic effects of the TM complex cations. A possible photocatalytic mechanism is also proposed based on the radical trapping experiments and electronic band structural calculations.