Vapochromism of a pyrrolizinato-nickel(II) complex incorporated in polyvinylbutyral. An optochemical detecting system for alcohols in air

The bis(1,2,6,7-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinido)nickel(II) complex (NiL2, L = C11H2N7-) has been incorporated as dispersed monomer in polyvinylbutyral (PVB) at a fairly high concentration (0.021 M). NiL2/PVB s pin coated thin films (thickness, similar to 2 mu m) on glass and silicon a nd evaporated free standing thicker films (thickness, similar to 50 mu m) h ave been studied by means of absorption or reflectivity visible as well as infrared spectroscopy. The light-blue NiL2/PVB film fades slightly on heati ng (for 7 min at 90 degrees C) and remains as such after cooling to room te mperature. The optical spectrum of the thermally activated NiL2/PVB system, in contact with organic solvent vapors at room temperature, changes with t ime evolving towards the initial spectrum before the thermal treatment. The system is therefore amenable for sensing organic solvents in air. Several ordinary solvents have been tested. After 12 min exposure to air saturated with vapor a steady-state absorbance signal at the most sensitive wavelengt h (661 nm) is reached for any tested solvent. The system is most sensitive to alcohols. Response cycles are reported for methanol as solvent.