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Sublimed films of meso-tetraphenylporphyrinatocobalt(n) (CoTPP) undergo a series of chemical transformations in an atmosphere of NO 2. In the first stage, at low NO 2 pressures, the axial five-coordinate CoIIXTPP -NO 2 complex is formed. An increase in the NO 2 pressure and/or exposure results in subsequent oxidation with the formation of a 7t-radical cation CoTPP' +. In the latter, according to the IR spectral data, nitrogen dioxide is axially coordinated by the cobalt ion. Further increase in the NO2 pressure leads to both the formation of a dication and nitration of the porphyrin ring most likely at the meso-and 13-pyrrolic positions. Irreversible chemical transformations in the sublimed CoTPP films prevent their use as NO 2 sensors.Key words: meso-tetraphenylporphyrinatocobalt(tl), sublimed films, n-radical cations, IR and UV-VIS spectroscopy, nitrogen dioxide, nitration, isoporphyrin.Tetraarylporphyrins can form microporous "porphytin sponges," which allows incorporating guest molecules with different shapes and sizes. 1,2We have previously shown 3 that the structure of sublimed layers of meso-tetraphenylporphyrin (MTPP) metallocomplexes is also sponge-like. The microporosity of samples increases if the sublimed layers are formed during deposition on a low-temperature (T = 80 K) surface. In these layers, potential reagents can easily diffuse across the thickness, and the adducts that formed can be studied by spectral methods without interference by a solvent. Study of model Co II porphyrins with oxidation properties 4 have shown that depending on the oxidation conditions, an electron can be released from either the metal atom s or the porphyrin ring. 6 In sublimed layers of meso-tetraphenylporphyrinatocobalt(IO (CoTPP) under diminished pressure of NO 2, the metal is oxidized 7 in the first stage to form a five-coordinate extracomplex O2N 9 CoI[ITPP.This work is devoted to spectral studies of consecutive transformations in the sublimed CoTPP layer in the NO 2 atmosphere. ExperimentalSublimation was carried out in a vacuum cryostat with a KBr or CaF 2 support cooled with liquid nitrogen for recording IR and UV spectra, respectively. Then the sublimed layer was heated to 283 K under dynamic vacuum, and NO 2 was introduced in the cryostat. The pressure of NO 2 in the 4--40 Pa interval was monitored by a vacuum therrnocouple lamp. The CoTPP layer was exposed to the NO 2 atmosphere for a certain time, then the samples were exposed in high vacuum, and the IR or UV-VIS spectra were recorded. Taking into account potentialities of electron and IR-Fourier spectroscopy, we carried out some measurements in the NO 2 atmosphere, which made it possible to monitor the dynamics of the process.The synthesis and purification of NO 2 were described in Ref. 8.IR spectra in the 450--4000 cm -1 region were recorded on a Specord IR-75 spectrometer and a Perkin--Elmer I600 Fourier-spectrometer (the spectral width of the gap was 4 cm-t). UV-VIS spectra were recorded on Speeord M-40 and Beckman DU-640i spectrophotometers. Results and D...