Crown Cation Complex Effects. 21. Spectral Evidence Bearing on the Interaction between Arenediazonium Cations and 21-Crown-7 in Nonpolar Solutions

Article abstract of DOI:10.1021/jo00156a019

15-Crown-5 does not complex arenediazonium tetrafluoroborates, but 21-crown-7 is known to complex them more strongly than does 18-crown-6.Despite this, the infrared and ultraviolet band shifts for complex vs. noncomplexed forms are far smaller for the former than for the latter.It is suggested that instaed of the crown completely and tightly surrounding the diazonio function, the crown collars (nearly encircling) the diazonio group and then uses the remaining donor atom(s) either to solvate the terminal nitrogen atom or interact as a base with the ?-acidic aromatic ring, providing additional stability.Since the mode by which 18-crown-6 and 21-crown-7 solvate the diazonium ion in each case differs, the spectral manifestations of this interaction differ.