A new anhydrous solid form of Co(NH3)5NO2(NO3)2 coordination compound is obtained. Crystal structure solved and refined. Packing of complex cations in the title compound is compared to that of hydrated form Co(NH3)5NO2(NO3)2·0.25H2O reported earlier. It is demonstrated that the packing arrangements of complex cations of these compounds are completely different. Single crystals of Co(NH3)5NO2(NO3)2 are found to exhibit photoactive behaviour: upon irradiation with visible light (λ = 403 nm) it undergoes linkage isomerisation Co(NH3)5NO22+ → Co(NH3)5ONO2+, the transformation is incomplete through the crystal. Crystal structure destruction on irradiation by light emitting diode is observed and explained in comparison with laser beam irradiation. The latter allowed single crystal to single crystal transformation.
Kalinina et al. (Sun,) studied this question.