A Stable Aluminum Tris(dithiolene) Triradical

A stable aluminum tris(dithiolene) triradical (3) was experimentally realized through a low-temperature reaction of the sterically demanding lithium dithiolene radical (2) with aluminum iodide. Compound 3was characterized by single-crystal X-ray diffraction, UV–vis and EPR spectroscopy, SQUID magnetometry, and theoretical computations. The quartet ground state of triradical 3has been unambiguously confirmed by variable-temperature continuous wave EPR experiments and SQUID magnetometry. Both SQUID magnetometry and broken-symmetry DFT computations reveal a small doublet–quartet energy gap [ΔEDQ= 0.18 kcal mol–1(SQUID); ΔEDQ= 0.14 kcal mol–1(DFT)]. The pulsed EPR experiment (electron spin echo envelop modulation) provides further evidence for the interaction of these dithiolene-based radicals with the central aluminum nucleus of 3.