An O2 smart plastic film for packaging.

The preparation and characterisation of a novel, water-proof, irreversible, reusable, UV-activated, O(2) sensitive, smart plastic film is described. A pigment, consisting of a redox dye, methylene blue (MB), and a sacrificial electron donor, DL-threitol, coated onto an inorganic support with semiconductor functionality, TiO(2), has been extruded in low-density polyethylene (LDPE). The blue-coloured indicator is readily photobleached in <90 s using UVA light (4 mW cm(-2)), whereby MB is converted to its colourless, leuco form, leuco-methylene blue (LMB). This form persists in the absence of oxygen, but is re-oxidised to MB in ~2.5 days in air under ambient conditions (∼21 °C, ~65% RH) within the O(2) smart plastic film. The rate of recovery is linearly dependent upon the ambient level of O(2). At the lower temperature of 5 °C, the kinetics of the photobleaching activation step is largely unchanged, whereas that of recovery is markedly reduced to t(1/2) = 36 h at 5 °C (cf. 9 h at 21 °C); the activation energy for the recovery step was calculated as 28 kJ mol(-1). The O(2)-sensitive recovery step was found to be moderately dependent upon humidity at 21 °C, but not significantly dependent upon humidity at 5 °C. The possible application of this type of indicator in food packaging is illustrated and discussed briefly.

3-Amino-carbonyl-pyridinium difluoro-acetate at 123†K.

In the crystal of the title compound, C(6)H(7)N(2)O(+)·C(2)HF(2)O(2) (-), the cation adopts a catemeric N-H⋯O hydrogen-bonded chain motif involving the carboxamide group, with two further N-H⋯O hydrogen bonds connecting the cations to adjacent difluoro-acetate anions via the carboxamide and pyridinium N atoms. The carboxamide group of the nicotinamidium ion is twisted by 32.3 (6)° from the pyridine ring plane. A number of C-H⋯O and C-H⋯F interactions consolidate the packing.

Nicotinamide-2,2,2-trifluoro-ethanol (2/1).

The nicotinamide (NA) mol-ecules of the title compound, 2C(6)H(6)N(2)O·C(2)H(3)F(3)O, form centrosymmetric R(2) (2)(8) hydrogen-bonded dimers via N-H⋯O contacts. The asymmetric unit contains two mol-ecules of NA and one trifluoroethanol molecule disordered over two sites of equal occupancy. The packing consists of alternating layers of nicotinamide dimers and disordered 2,2,2-trifluoro-ethanol mol-ecules stacking in the c-axis direction. Intra-molecular C-H⋯O and inter-molecular N-H⋯N, O-H⋯N, C-H⋯N, C-H⋯O and C-H⋯F inter-actions are present.

Cytenamide trifluoro-acetic acid solvate.

Cytenamide forms a 1:1 solvate with trifluoro-acetic acid (systematic name: 5H-dibenzo[a,d]cyclo-hepta-triene-5-carboxamide trifluoro-acetic acid solvate), C(16)H(13)NO·C(2)HF(3)O(2). The compound crystallizes with one mol-ecule of cytenamide and one of trifluoro-acetic acid in the asymmetric unit; these are linked by O-H⋯O and N-H⋯O hydrogen bonds to form an R(2) (2)(8) motif. The trifluoro-methyl group of the solvent mol-ecule displays rotational disorder over two sites, with site-occupancy factors of 0.964 (4) and 0.036 (4).