Matrix Isolation of Aryl(trifluoromethyl)carbenes, Heteroaryl(trifluoromethyl)carbenes and Phenylbis(trifluoromethyl)carbenes.

摘要

We have isolated and studied 2-naphthyl(trifluoromethyl)carbene, 1-naphthyl(trifluoromethyl)carbene, 4-pyridyl (trifluoromethyl)carbene, 2-pyridyl (trifluoromethyl)carbene, 3-pyridyl (trifluoromethyl)carbene, 3-bromo-5-pyridyl (trifluoromethyl)carbene, meta-phenylbis(trifluoromethyl)carbene and para-phenylbis(trifluoromethyl)carbene in low temperature matrices for the first time. The naphthyl(trifluoromethyl)carbenes are photostable and have triplet ground states in matrices as most of the other studied ary(trifluoromethyl)carbenes. The 1- and 2-naphthyl(trifluoromethyl)diazirines, the precursors of 1- and 2-naphthyl(trifluoromethyl)carbenes, have dissimilar geometric structures leading to different UV/Vis absorptions. In the studied pyridyl(trifluoromethyl)carbenes, 4-pyridyl(trifluoromethyl)carbene was the most stable one in matrice: no photoproduct from 4-pyridyl(trifluoromethyl)carbene was observed. However, we obtained a small amount of photoproducts of 2-pyridyl(trifluoromethyl)carbene, even though the result was not repeatable. The most reactive isomer was 3-pyridyl(trifluoromethyl)carbene, which could decompose under prolonged irradiation. The derivative of 3-pyridyl(trifluoromethyl)carbene, 3-bromo-5-pyridyl(trifluoromethyl)carbene, was more photolabile and could be converted to other intermediates with comparatively short term irradiation. All the studied pyridylcarbenes have triplet ground states. Although they were photostable, phenyl(trifluoromethyl)biscarbenes attracted our attention due to their interesting electronic structures. meta-Phenyl(trifluoromethyl)carbene has a quintet ground state, while the overall multiplicity of para -phenyl(trifluoromethyl)carbene is a singlet with a diradical structure.