Treatment of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) with a group 1 metal (Li, Na, K, Rb, or Cs), resulted in the reduction of this important radical to the TEMPO- anion-the first examples of elemental-metal single electron reduction of the radical to its anionic form. The synthesis and characterization of seven alkali metal TEMPO-complexes are reported. A variety of structural motifs are encountered depending on the choice of metal and/or solvent. (THF)(2)center dot[Li+(TEMPO-)](4) 1 crystallized from THF as a cyclic (Li4O4) molecule. Two Li centers are stabilized by coordination to a THF molecule; the others by intramolecular coordination to N-TEMPO atoms. [(THF)center dot Na+(TEMPO-)](4) 2 exists as a distorted cubane where each Na center is coordinated to a THF molecule. No appreciable Na-N-TEMPO coordination is observed. [(THF)(2)center dot Na-3(+)(TEMPO-)(2)(OH)](2) 3 was serendipitously prepared and exists as a distorted bis (cubane). It is envisaged that 3 is formed from 2 by insertion of a (Na-OH)(2) double bridge into its framework. [Na-4(+)(mu(3)-TEMPO-)(2)(mu(2)-TEMPO-)(2)(TMEDA)(2)] 4, adopts a four-runged ladder structure, whereby the two outer Na centers are coordinated to TMEDA, in addition to two mu(2)-O and a N atom. The inner metal atoms are bound to three mu(3)-O atoms and a N atom. [(THF)center dot K+(TEMPO-)](4) 5 resembles the motif found for 2; however, presumably because of the larger size of the metal, K-N-TEMPO interactions are present in 5. The asymmetric unit of [(TMEDA)center dot Rb-2(+)(TEMPO-)(2)](2) 6 comprises a Rb4O4 cubane with half a molecule of TMEDA coordinated to each metal. From a supramolecular perspective, 6 exists as a polymeric array of cubane units connected by TMEDA bridges. Completing the series, [Cs+(TEMPO)](infinity) 7 crystallizes from hexane to form a donor-free polymeric complex. Complexes 1, 2, and 4-7 are soluble in D-8 center dot THF solution, and their NMR spectra are reported. The solution structures in donor solvent appear virtually identical.