Synthesis And Properties Of Trifluoromethyl-substituted Cyclometalated Pt(?) Complexes

Visible light has been widely applied to the organic synthesis as a kind of renewable resources.Pt(?)complexes can be easily synthesized,which provides a feasible access to tuning the excited-state redox potentials and lifetimes of the complexes by modifying the ligands.What's more,Pt(?)complex is a kind of excellent photocatalysts with strong visible light absorption.Currently,taking advantage of these favourable properties,photoredox catalytic applications of Pt(?)complexes have been achieved in polymerization,hydrogen production and oxidation reactions.As reported in the literature,Pt(?)complexes used in the visible-light-induced oxidation reactions are most Pt(?)terpyridyl complexes.To the best of our knowledge,the oxidation reactions catalyzed by cyclometalated Pt(?)complexes have not been reported.In recent years,the oxidation hydroxylation of arylboronic acids and its derivatives has become a hotpoint in organic synthesis.A variety of reaction systems for hydroxylation of arylboronic acids have been reported.Among them,the use of green O2 as an oxidant in the visible-light-induced oxidation of arylboronic acids has caused extensive concerns.The oxidation potentials and excited state oxidation potentials of Pt(?)complexes can be improved by introducing a trifluoromethyl group(CF3)to the cyclometalating ligand.The main contents of this paper are as follows:1.Trifluoromethyl-substituted cyclometalated Pt(?)complexes C1-C6 were synthesized and characterized.The photophysical and electrochemical properties of C1-C3 and Pt(ppy)(acac)were tested in DMF to study the effect of substituents on the properties of the complexes.Meanwhile,the photophysical and electrochemical properties of C1,C4-C6 and Pt(ppy)(acac)were investigated in four solvents(toluene,THF,acetonitrile,and DMF)to explore the effects of solvent and the position of trifluoromethyl group on the properties of complexes.2.A novel and efficient visible-light-induced aerobic hydroxylation of arylboronic acids catalyzed by cyclometalated Pt(?)complexes was developed.The reaction was carried out under the irradiation of visible light,using oxygen in the air as oxidant.Using the aerobic oxidation hydroxylation of 4-methoxy phenylboronic acid as a model reaction,the effects of different parameters on the reaction were studied.Under optimal reaction conditions,a wide range of arylboronic acids can be converted to the corresponding phenols with the highest yield up to 96%.Notably,this catalytic system provides a simple and efficient approach to the preparation of complicated phenols.