13C, 14N and 29Si Nuclear magnetic resonance and photoelectron spectra of azo compounds
Abstract
13 C, 14N and 29Si-n.m.r. data of azo compounds R1—N [graphic omitted] N—R2 with substituents R1= R2= N(CH3)2, NC5H10, N[Si(CH3)3]2, OSi(CH3)3, Si(CH3)3 and R1/R2= CH3/Si(CH3)3, C(CH3)3/Si(CH3)3, C(CH3)3/Si(OCH3)3, C(CH3)3/Ge(CH3)3, C(CH3)3/P(CH3)2 and C6H5/Si(CH3)3 are reported and compared with corresponding values of other compounds known from the literature. The chemical shifts δ14N show an almost linear correlation with n→π* transition energies while no dependence on calculated charge densities is observed. This demonstrates that the low energy transitions n→π* are mainly responsible for nitrogen shielding of azo compounds. δ14N of bis(trimethylsilyl)di-imine appears to be at the lowest field of all diamagnetic nitrogen compounds so far studied. The orbital sequence in azo compounds is checked by means of photo-electron (p.e.) spectroscopy. The hitherto unknown p.e. spectra of some azo compounds are discussed qualitatively and by means of CNDO/S calculations. It is shown that n.m.r., u.v. and p.e. spectroscopy are sensitive to substituent effects in azo compounds.
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