New members of a class of dinitrosyliron complexes (DNICs): The characteristic EPR signal of the six-coordinate and five-coordinate {Fe(NO)2}9 DNICs

► A new class of dinitrosyliron complexes has been synthesized. ► The electron-donating strength of the ligands regulates electronic structure of the {Fe(NO)x} core. ► The five- and six-coordinate {Fe(NO)2}9 DNICs can be differentiated from their tetrahedral analogues by the EPR characteristics.