Active-site models of bacterial nitric oxide reductase (NOR) featuring a heme Fe and a trisimidazole- and glutaric acid-bound non-heme Fe (Fe-B) have been synthesized. These models closely replicate the proposed active site of native NORs. Examination of these models shows that the glutamic acid mimic is required for both FeB retention in the distal binding site and proper modulation of the redox potentials of both the heme and non-heme Fe's.