Infrared hole burning of crown ether 18-c-6 ammonium ion complexes.

Crystals of the complexes of 18-crown-6 with a number of ammonium salts (bromide, chloride, two forms of iodide, nitrate) and with amminetrifluoroboron have been prepared, analyzed with X-ray diffraction, and then investigated by infrared hole burning. The complexes all have similar hydrogen-bonding arrangements between the crown ether ring and the ammonium nitrogen. Hole burning of the infrared bands at low temperature identifies the N-D hydrogen bonds of the compounds that have been doped with a small amount of deuterium. The patterns of N-D bands from different complexes are often quite overlapped, with a few notable exceptions. The hole burning reveals a wide variety of phenomena, including monotonic decay and kinetic interchange among the holes and antiholes, a variety similar to that observed in previous hole-burning experiments.