Details of the crystal structure and quantum chemistry calculations of the title mol­ecule, C13H9BrO, illustrate the effects of intermolecular interactions and the substitution of one of the two aromatic rings on the molecular conformation. The asymmetry of the mol­ecule is documented by the two Caryl—Caryl—C=O torsion angles of −68.3 (5) and −17.6 (6)°. A C—H·O hydrogen bond [H·O = 2.5 Å, C·O = 3.412 (5) Å and C—H·O = 174°] and a C—H·π contact involving the H atom at position 4 of the substituted ring and the π‐system of the unsubstituted ring of an adjacent mol­ecule [H·Cg = 2.96 Å, C·Cg = 3.806 (5) Å and C—H·Cg = 153°; where Cg is the centroid of the unsubstituted ring] are observed in the crystal structure.

This work describes the gas-sensitive properties of a one-dimensional organic conductor before and after exposure to carbon monoxide and human breath. A sensitive material, an anion-radical salt of tetracyanoquinodimethane, has been investigated by infrared spectroscopy and electrical resistivity measurements. Drastic spectral and electrical changes are found after gas exposure showing that the compound interacts strongly with human breath, carbon monoxide, and ammonia. Under breath action the resistance changes by more than three orders of magnitude while the adsorption of CO, one of the components of breath, results in a decrease in both IR absorption and electrical conductivity. The intensity of the IR absorption spectrum of the material in the CO medium decreases down to 30% in the 2180-2500 cm(-1) range. This absorption varies by about 10% between 750 and 2500 cm(-1) after breath action. Direct electrical measurements show that actions of donor or acceptor gas result in opposite changes of electric resistance. The electrical resistance of the sample can drop down to 0.4 MΩ due to the pulse action of ammonia at 4 ppm concentration, while it increases upon exposure to carbon monoxide media at concentrations of 6-25 ppm. The response signal of the investigated samples changes proportionally to the concentration of the acting gas. The results substantiate prominent gas sensitivity of the investigated material, which might find applications for breath analysis, in particular, for the development of noninvasive diagnosis of gastric diseases.

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