Tetranuclear and dinuclear phenoxido bridged copper complexes based on unsymmetrical thiosemicarbazone ligandsElectronic supplementary information (ESI) available: 1H NMR for HLMeH and HLMe2 (S1), packing details for 1t and 2d (S2-S5), χMvs. T for 1t and 2d (S6), magnetic orbitals for the broken-symmetry state of complex 1t and 2d (S7). UV-Vis spectra (S8), ESI-MS and isotopic patterns (S9-S11) for 1t and 2d, CV for 1t (S12), spin density plot for 2d and mono-oxidized form (S13), COSY spectra (S

We report on the synthesis of new dinucleating phenol-based "end-off" compartmental ligands HL MeH and HL Me2 bearing two different binding sites, one bis(2-methylpyridyl)aminomethyl (BPA) and one thiosemicarbazone (TSC) site, and their corresponding copper( ii ) complexes 1t and 2d . With the ligand HL MeH , a tetranuclear entity ( 1t ) has been isolated in the solid state, whereas with HL Me2 , which differs from HL MeH by a methyl substituent on the N-terminal amino group of the TSC arm, a dinuclear form ( 2d ) is obtained. X-ray crystallography analysis shows that the nuclearity di vs. tetra is modulated by interactions between copper atoms and hydroxido bridges along with the sulphur atoms of TSC arms. From a magnetic point of view, 1t can be considered as an association of two dinuclear forms leading for both complexes to overall antiferromagnetic coupling. Analysis in acetonitrile solution of structure-property relationships has been carried out by comparing their UV/Vis, electrochemistry, ESI-MS, and NMR (variable temperature and DOSY = diffusion ordered spectroscopy) properties with trends from computational calculations (DFT). HRMAS-DOSY (High Resolution Magic Angle Spinning) NMR spectroscopy has been performed to evaluate the presence of different species in solution at room temperature. Dinuclear and tetranuclear copper( ii ) complexes based on N,S ligand systems in the solid state and in solution are described.