The phosphorescence spectra and lifetimes of the cyanate salts of Na+, K+, Cd2+, Ag+, Hg2+, and Pb2+ have been measured. Similar measurements have been made on CH3NCO, CH3CH2NCO, C6H5NCO, and HNCO. The results of these studies indicate that the lowest‐energy excited state of the cyanate ion and the covalent isocyanates is of ··· (π)3(π*)1 MO excitation type: This state is Σ+3(C∞υ) in NCO, A′(Cs3) in HNCO and the alkyl isocyanates, and A13(C) in phenyl isocyanate. Fluorescence is observed only from the phenyl isocyanate and is assumed to initiate in an excited state which has dominant excitation amplitude on the phenyl moiety. Vibrational structure observed in the phosphorescence of NaOCN and C6H5NCO is analyzed, and similarities in the spectra are pointed out. A heavy‐atom spin–orbit coupling effect is observed in the cyanate salt series. Spin–orbit coupling calculations have been performed on NCO, linear and bent. A phosphorescence lifetime of ∼ 0.12 sec, in good agreement with experiment, is predicted for the Γππ3* → 1Γ1 transition.

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