Six combinations of oxidn. states are conceivable for the paramagnetic Ruk(NOm)(Qn)(terpy)2+ complex. Single-crystal X-ray diffraction, spectroscopic anal. (IR, EPR at conventional and high frequency), and DFT calcns. establish that it is the iminosemiquinone radical structure that is formed: Ruk(NOm)(Qn)(terpy)2+ (k=2+, m=1+, n=1-). on SciFinder(R)