The 90K solid-state structures, room temperature absorption, and room temperature and 17 K emission spectra ofseven different salts of [Cu(I)(bfp)
2]
+ (bfp = 2,9-bis(trifluoromethyl)-1,10-phenanthroline) have been determined. Toquantify the distortion of the Cu coordination environment, a distortion parameter
![](/images/gifchars/zeta.gif)
is defined that is a combinedmeasure of the flattening, rocking, and wagging distortions of the complex cations. In general, the distortion in the(bfp) cations is less than found previously for Cu(I)(dmp)
2 (dmp = 2,9-dimethyl-1,10-phenanthroline) salts, in particularthe flattening is reduced because of the bulkier 2,9-substituents. The 17 K lifetimes range up to 1.8
![](/images/entities/mgr.gif)
s in theseries of solids examined and, with the marked exception of the BF
4- salt, correlate linearly with the distortionparameter
![](/images/gifchars/zeta.gif)
. The emission wavelength red-shifts with decreasing lifetime, which implies that an increased ground-state distortion is associated with a smaller energy gap.