A new Mannich base, 2-(4-(2-hydroxy-3-methoxy-5-methylbenzyl)-piperazin-1-yl)methyl)-6-methoxy-4-ethylphenol (H2L) and its tetranuclear NiII complex, [Ni4L2(μ1,1-Cl)2(H2O)4]Cl2 (compound 1) are characterised by single crystal X-ray diffraction measurements. The compound 1 contains four different NiII centres...