Two new 3-D cadmium bromoplumbates: the only example of heterometallic bromoplumbate based on crown [Cd(Pb4O4)Br2] clusters

Abstract

Two new cadmium bromoplumbates [CdPb₂Br₂L₂]_n (1, L = ethylene glycol) and [CdPb₆Br₆L₄]_n (2) have been solvothermally synthesized and structurally characterized. 1 contains 1-D neutral heterometallic chains [CdPb₂Br₂L₂]_n, which are further connected via weak Pb–Br bonds, resulting in a 3-D network structure. The 3-D framework of 2 is constructed by the interconnection of a 2-D neutral layer [CdPb₆Br₆L₄]_nvia weak Pb–Br bonds. The [CdPb₆Br₆L₄]_n layer is based on the linkages of dimeric [Pb₂Br₄] units and heterometallic crown [Cd(Pb₄O₄)Br₂] clusters containing a rare eight-membered [Pb₄O₄] ring. Although a few heterometallic bromoplumbate clusters have been reported, they usually exhibit molecular moieties. 2 represents the only example of 3-D heterometallic bromoplumbate based on the combination of heterometallic crown [Cd(Pb₄O₄)Br₂] clusters and dimeric [Pb₂Br₄] units. Their optical properties are studied and density functional theory calculations for 1 and 2 have also been performed.