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 3 was characterized by single-crystal X-ray diffraction, UV-vis and EPR spectroscopy, SQUID magnetometry, and theoretical computations. The quartet ground state of triradical 3 has 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 [Δ E DQ = 0.18 kcal mol -1 (SQUID); Δ E DQ = 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 .