An ultra-stable Cu(I)12 cluster built from a Cu(I)6 precursor sandwiched by two Cu-3(I) -thiacalixarene units for efficient photothermal conversion

We report the synthesis, crystal structure, optical properties, and photothermal conversion properties of an ultra-stable cuprous Cu-12 cluster, namely {[Cu-3(I)(HTC4A)](2)[Cu-6(I) (2-PyS)(6)]}center dot H2O (Cu-12, H(4)TC4A = p-tertbutylthiacalix[4]arene, 2-PySH = 2-pyridinethiol), which was built from a pre-synthesized Cu-6(I)(2-PyS)(6)(Cu-6) precursor and two Cu-3(I) -HTC4A polynuclear secondary building units (PSBUs). The Cu-12 cluster features a sandwich-like framework in which the Cu-6 core is double surface capped by forming six Cu-S bonds with two Cu-3(I) -HTC4A PSBUs. The "cluster-cluster" assembly strategy enables all the metal centers in the Cu-12 cluster to be monovalent and efficient organic ligand protection makes the cuprous cluster stable in common solvents (alcohol, acetonitrile, acetone, CHCl3, N N-dimethylacetamide, etc.) as well as in strong acids ( pH = 1) or bases ( pH = 14). Band gap determination and photophysical analysis combined with density functional theory (DFT) calculations indicated that Cu-3(I)-HTC4A PSBUs can tune the electron and hole distribution of the Cu-6 core, which makes Cu-12 a stable and efficient photothermal conversion material both in the solid state and in water/N,N-dimethylformamide solvents.