Self-assembly of D-penicillaminato M6M8′ (M = NiII, PdII, PtII; M′ = CuI, AgI) clusters and their organization into extended LaIIIM6M8′ supramolecular structures

A series of chiral M6M8' cluster compounds having twelve free carboxylate groups, [M6M8'(D-pen-N, S)(12)X](5-) (M/M'/X = Pd-II/Ag-I/Cl- ([1](5-)), Pd-II/Ag-I/Br- ([2](5-)), Pd-II/Ag-I/I- ([3](5-)), Ni-II/Ag-I/Cl- ([4](5-)), Pt-II/Ag-I/Cl- ([5](5-)), Pd-II/Cu-I/Cl- ([6](5-)); D-H(2)pen = D-penicillamine), in which six cis-[M(D-pen-N, S)(2)](2-) square-planar units are bound to a [M-8'X](7+) cubic core through sulfur-bridges, was synthesized by the reactions of cis-[M(D-pen-N, S)(2)](2-) with M' in water in the presence of halide ions. These M6M8' clusters readily reacted with La3+ in aqueous buffer to form (La2M6M8)-M-III' heterotrimetallic compounds, La-2[1](CH3COO), La-2[2](CH3COO), La-2[3](CH3COO), La-2[4](CH3COO), La-2[5](CH3COO) and La-2[6]Cl, in which the M6M8' cluster units are linked by La3+ ions through carboxylate groups in a 1 : 2 ratio. While the (La2M6Ag8I)-M-III compounds derived from [1](5-), [2](5-), [3](5-), [4](5-) and [5](5-) have a 1D helix supramolecular structure with a right-handedness, the (La2Pd6Cu8I)-Pd-III-Cu-II compound derived from [6](5-) has a 2D sheet-like structure with a triangular grid of the (Pd6Cu8I)-Cu-II cluster units. When aqueous HCl was added to the reaction solution of [6](5-) and La3+, another (La2Pd6Cu8I)-Pd-III-Cu-II heterotrimetallic compound, La-2[6]Cl center dot HCl, in which the (Pd6Cu8I)-Cu-II cluster units are linked by La3+ ions to form a 2D structure with a rectangular grid, was produced. The solid-state structures of these (La2M6M8)-M-III' compounds, determined by single-crystal X-ray crystallography, along with the spectroscopic properties of the M6M8' cluster compounds in solution, are described.