Conversion of NiNd and NiTb compartment compounds into one-dimensional coordination polymers or tetranuclear dimers

This paper describes the conversion of NiNd and NiTb compartment compounds into 1D coordination polymers or discrete tetranuclear 3d–4f compounds under microwave-heating conditions. Stirring a water–ethanol solution containing Ni(CH3COO)2·4H2O, o-vanillin, 1,3-diaminopropane and LiOH·H2O at 30 °C produced [Ni(L1)2](H2O) (1), which possesses two imine–amine type ligands (HL1 = ((3-methoxysalicylidene)amino)-3-aminopropane). Compound 1 reacted with Nd(NO3)3·6H2O to give a dinuclear NiNd complex [NiNd(HL1)2(NO3)3](NO3)2 (2). When compound 2 was microwave-heated (700 W) in water in the presence of a bispyridine (bipy = 4,4′-bipyridine; bipp = 1,3-bis(4-pyridyl)propane), a tetranuclear dimer bridged by two nitrato (NO3−) ligands was obtained: [NiNd(L2)(NO3)(μ3-NO3)(bipy)]2(OH)2(H2O)2(bipy) or [NiNd(L2)(NO3)(μ3-NO3)(bipp)]2(OH)2(H2O)4 (H2L2 = 1,3-bis((3-methoxysalicylidene)amino)propane). By contrast, compound 2 was converted into a 1D coordination polymer, [Ni2Nd2(L2)2(H2O)2(μ-NO3)3](OH−)3(H2O)6, when microwave-heated in the absence of the bispyridine. Compound 1 reacted with Tb(NO3)3·5H2O to give a dinuclear complex [NiTb(HL1)2(NO3)3]·(NO3)2, a NiTb analogue of compound 2. Microwave-heating this NiTb compound in water and in acetonitrile produced a 1D coordination polymer, [Ni2Tb2(L2)2(μ-NO3)3(H2O)2]·(OH−)3·4H2O, and a tetranuclear NiTb dimer, [NiTb(L2)(μ3-NO3)(NO3)(H2O)]2·(OH)2·(H2O)4, respectively. The NiTb compounds exhibited emission quenching of the Tb3+ ion, probably due to a Tb3+ → Ni2+ energy transfer. In addition, the intensities of the emission spectra of these compounds did not increase when the lattice water molecules were removed.

We observed that microwave heating induced the transformation of two imine–amine type ligands into a bis(imine) type compartmental ligand, as well as the conversion of a molecular species into a one-dimensional coordination polymer.Figure optionsDownload as PowerPoint slide