Toward a dodecanuclear molecular Re(i) box: structural and spectroscopic properties.

Two tetrapyridyl ligands of 1,2,4,5-tetraethynyl(4-pyridyl)benzene (tpeb) and tetra(4-pyridyl)-tetrathiafulvalene (TTF(py)4) were used to react with trinuclear (Re(CO)4)3(C3N3S3) (C3N3S3 = cyanurate trianion) moieties to afford hexanuclear [(Re(CO)3)6(tpeb)2(C3N3S3)2]·4CH3CN·toluene (1) and dodecanuclear [(Re(CO)3)12(TTF(py)4)3(C3N3S3)4]·8CH3CN·12DMF (2) boxes, respectively, under solvothermal conditions. Surprisingly, similar tetrapyridyl ligands with different core units (i.e., benzene and tetrathiafulvalene moieties) led to dramatically different structural motifs (i.e., hexanuclear and dodecanuclear boxes). Complex 1 forms a slightly bent trigonal-prismatic structure, containing two μ3-tpeb ligands and two Re3C3N3S3 moieties as well as a ππ interaction distance of 3.86 Å. It is noted that complex 2 features a novel four-star structure, and three crossed tetrathiafulvalene moieties from three μ4-TTF(py)4 ligands to form a triple-decker arrangement with a ππ interaction distance of 3.70 Å. Moreover, 1 and 2 display luminescence properties in the solid state along with electrochemical properties for complex 2 arising from the electroactive TTF core.