In the HOMO and HOMO-2 molecular orbitals shown in Fig. , the contribution from the diazirine carbon is due nearly 100% to an atomic p-orbital. A Mulliken population analysis (see Table in the ESI) reveals essentially zero s-character from this carbon atom to either molecular orbital. This suggested that the diazirine group could be viewed as being 'conjugated' to the benzene ring. Of course, in order for conjugation to be established, the diazirine needs to be coplanar to the aromatic Fig. Changes in UV/Vis absorption spectra with varying substitution on the aromatic ring of a trifluoromethyl aryl diazirine. All data were acquired using 5 mM samples in n-hexane. Replotted from raw data published in reference 17.