Geometric Conformers of 2,2-Dinaphthylcarbene in Shpol'skii Matrices Revealed by Electron Spin Resonance and Hole Burning

The ESR spectra of 2,2-dinaphthylcarbene in n-heptane and n-hexane at 3.5 K were studied. The spectra indicated that a single carbene conformer was present in the former matrix but that at least three geometric conformers of this carbene with different zero-field splitting parameters were present in the latter matrix. This observation was in good agreement with high resolution fluorescence spectra. D0 parameters of 0.361 and 0.413 cm-1 were found for the pseudo-E/trans and Z/cis conformers of the carbene, respectively. The ESR results are in quantitative agreement with hole burning studies.