Base-mediated alkynyl-cubane to Cu 8 -alkynide cluster transformation

] through deprotonation of the triisopropylacetylene ligands. The former displays exclusively side-on coordination of the terminal acetylene, while the latter exhibits both side-on and end-on coordination of the deprotonated acetylide moiety. The octanuclear complex shows solid-state emission around 640 nm, while the cubane displays a thermochromic emission shifting from 563 nm at r.t. to 608 nm upon cooling to 77 K.