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ISSN 1998-9539

Low-Temperature Interaction of Dioxygen and Carbon Monoxide with Microporous Films of Co(II) Porphyrins Containing Bulky tert-Butyl Substituents

Tigran S. Kurtikyan,a@Astghik A. Hovhannisyan,aAlexey V. Lyubimtsev,b Tatiana A. Ageeva,b Vladimir S. Ugarov,b and Oscar I. Koifmanb
aMolecule Structure Research Center of Scientific and Technological Center of Organic and Pharmaceutical Chemistry NAS, 0014 Yerevan, Armenia
bResearch Institute of Macroheterocycles, Ivanovo State University of Chemical Technology, 153000 Ivanovo, Russia
@Corresponding author E-mail:
DOI: 10.6060/mhc160538k
Macroheterocycles 2016 9(2) 156-162
The low-temperature interaction of O2, CO and their mixtures with sublimed layers of Co(II) complexes of 5,10,15,20-tetrakis(3’,5’-di-tert-butylphenyl)porphyrin (I) and 5-(pyridin-4’-yl)-10,15,20-tris(3’,5’-di-tert-butylphenyl)porphyrin (II) has been studied by FTIR and optical spectroscopy. In contrast to the layers of [5,10,15,20-tetraphenylporphyrinato]cobalt(II) Co(TPP), that lose their porosity and ligand-binding ability upon standing at ambient conditions overnight, the films of I conserve these properties for a long time. Thus the bulky tert-butyl groups of I substantially slow down the close packing of molecules in the films making metal ions accessible to different ligands. It is shown that the films of II consist of coordination oligomers, the sixth coordination site of which is occupied by the pyridyl group of an adjacent molecule in the film. The reaction of O2 gas with these films leads to the formation of two types of complexes: six-coordinate dioxygen complexes, in which the fifth site is occupied by the pyridyl group of the neighboring molecule in the film and the five-coordinate dioxygen complexes that terminate the oligomers. Upon storage of the films, the concentration of six-coordinate complexes increases at the expense of the five-coordinate indicating increasing degree of oligomerization. In contrast, only the end group of oligomers is able to coordinate carbon monoxide CO. No six-coordinate complexes of CO with trans pyridyl group are formed in the films of II and the 6-coordination sites of oligomers remain free. When CO/O2 mixture is admitted into the cryostat with films of II these sites selectively bind O2. This phenomenon allows eliminating O2  from the CO/O2 mixture containing very low concentrations of O2 and can be used for CO purification of trace quantities of dioxygen. .



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