The low-temperature interaction of NO(15NO ) with sublimed layers of meso-mono-4-pyridyl-tri-phenyl- and meso-mono-3-pyridyl-tri-phenyl-porphyrinatocobalt(II) ( CoM4PyTPP (I) and CoM3PyTPP (II), respectively) has been investigated by means of FTIR and UV-visible spectroscopy. In addition to the stable five-coordinate nitrosyl complexes that are similar to the closely-related meso-tetraphenylporphyrinatocobalt(II)-nitrosyl Co(TPP)(NO) complex, a new type of complex with coordinated NO (15 NO ) has been found for the layers that were maintained at room temperature overnight before addition of nitric oxide at low temperature. The ν{ NO (15 NO )} in this species are more than 20 cm−1 lower than in five-coordinate compounds. These adducts are assigned to six-coordinate nitrosyl complexes, in which the fifth coordination site is occupied by the pyridyl group of the adjacent I (II) molecules. Warming the layers containing six-coordinate nitrosyl complexes of I almost completely transforms them to stable five-coordinate nitrosyl species indicating oligomers' disruption rather than loss of nitric oxide. In the case of II, however, a noticeable fraction of the six-coordinate species is left upon warming. Introducing new portions of NO to these layers at low temperature leads to formation of additional quantities of the six-coordinate species. Hence, part of six-coordinate complexes in II decomposed upon warming by releasing NO instead of by breaking Co -pyridyl bonds, therefore leaving free the sixth coordination sites in these layers. This result suggests a good possibility for creating solid state NO storage devices in which nitrogen monoxide can be kept and easily released by warming of the system.
Interaction of dioxygen with nitrosyl complexes of meso-mono-4(3)-pyridyl-triphenylporphyrinato cobalt in sublimed layers