FORMATION OF INTERMOLECULAR HYDROGEN-BONDS IN LIGHT-SENSITIVE CRYSTALS OF C-2'-(O-OXYPHENYL)VINYL-N-P-METHYLPHENYL NITRONE, 2'-(2''-OXY-5''-BROMOPHENYL)VINYL-N-P-METHYLPHENYL NITRONE, C-2'-(2''-OXY-5''-BROMOPHENYL)-VINYL-N-PHENYL NITRONE, AND C-2'-(O-OXYPHENYL)VINYL-N-METHYL NITRONE

This paper studies the crystal structure of new substituted light-sens itive azomethine N-oxides (nitrones): C-2'-(o-oxyphenyl)vinyl-N-p-meth ylphenyl nitrone (1), C-2'-(2 ''-oxy-5 ''-bromophenyl)vinyl-N-p-methyl phenyl nit one (2), C-2'-(2 ''-oxy-5 ''-bromophenyl)-vinyl-N-phenyl ni trone (3), and C-2'-(o-oxyphenyl)vinyl-N-methyl nitrone (4). In contra st to the compounds studied earlier [1, 2], 2'-(beta-oxy-alpha-naphthy l)vinyl-N-p-methylphenyl nitrone (5), C-2'-(beta-oxy-alpha-naphthyl)vi nyl-N-phenyl nitrone (6), C-2'-(o-oxyphenyl)vinyl-N-phenyl nitrone (7) , and C-2'-(o-oxyphenyl)vinyl-N-p-bromophenyl nitrone (8), the nitrone s studied in this work have anti- rather than syn-orientations of the nitrone and hydroxyl groups. Due to this spatial arrangement of the pr oton-donating hydroxyl and proton-accepting nitrone groups, molecules in crystals 1-4 are bonded by intermolecular hydrogen bonds (IHB) to f orm chains but not centrosymmetric dimeric associates (CDA). Two types of chain arrangements were revealed ''head-to-tail'' and ''head-to-ta il, tail-to-head.'' It is shown that the introduction of an alkyl subs tituent instead of an aryl one at the nitrogen atom of the nitrone gro up in 4 leads to a change in the geometry of the IHB in the I-I-associ ate. It is proven that the hydroxyl proton can undergo an intermolecul ar 0-->0 transfer in the chain of hydrogen bonds in crystals 1-4, whic h can give rise to photochemical transformations in these crystals.