o-Phenylene halocarbenonitrenes and o-phenylene chlorocarbenocarbene: a combined experimental and computational approach.

[reaction: see text] Computations find that o-phenylene(halo)carbenonitrenes 2-XN, X = F, Cl, Br, have quinoidal singlet biradical ground states such as the parent o-phenylenecarbenonitrene (2-HN). Compared to the parent 2-HN, halogen substitution stabilizes the A'' states relative to the A' ones. Halogen substitution also affects the barrier and exothermicity of the ring-opening reaction (to form unsaturated nitriles 4-XN, X = F, Cl, Br), but it has a smaller effect on the ring-closing reaction (to form benzo(aza)cyclobutadiene 3-XN, X = F, Cl, Br).

Photolysis of 3-(2-Formylphenyl)-3-chlorodiazirine in an Ar matrix at low temperature.

Photolysis of 3-(2-formylphenyl)-3-chlorodiazirine in an Ar matrix at 13 K was monitored by IR and UV-vis spectroscopies. Characterization of the products was carried out by comparing the spectra with the theoretical IR spectra obtained by using DFT, which suggested that anti,anti-2-formylphenyl(chloro)carbenes (a,a-2), ketenes (syn- and anti-3), chlorobenzocyclobutenone (4), and chloroisobenzofurane (5) were formed. This indicates that carbene 2 interacts with both hydrogen and oxygen in the formyl group.

Halogen derivatives of m-phenylene(carbeno)nitrene: a switch in ground-state multiplicity.

m-Phenylene-coupled carbenonitrenes [(3-nitrenophenyl)methylene (2-H), (3-nitrenophenyl)fluoromethylene (2-F), (3-nitrenophenyl)chloromethylene (2-Cl), (3-nitrenophenyl)bromomethylene (2-Br)] have been investigated computationally (with B3LYP, MCSCF, CASPT2, ROMP2, and QCISD(T) methods) and experimentally (with IR, UV, and ESR spectroscopy). For each species, five electronic states were considered. At the highest level of theory explored, the parent compound (2-H) has a quintet ground state, but its halogen derivatives (2-X, X = F, Cl, and Br) have triplet ground states.