Platinum(II) Schiff Base Complexes as Photocatalysts for Visible‐Light‐Induced Cross‐Dehydrogenative Coupling Reactions

Abstract

Four phosphorescent platinum(II) Schiff base complexes are screened for application in visible‐light‐induced cross‐dehydrogenative coupling (CDC) reactions. Preliminary studies show that, among the four platinum(II) complexes, Pt3 is an efficient catalyst for CDC reactions with oxygen as an oxidant. Light irradiation (λ>420 nm) on a mixture of the PtII complex, tertiary amine, and a variety of nucleophiles (nitroalkanes, ketones, or indoles) under aerobic conditions gives α‐functionalized tertiary amines in good to excellent yields. The photoluminescence quenching experiment reveals that the CDC reaction is initiated by photoinduced electron transfer from N‐phenyltetrahydroisoquinoline to the PtII complex. Further, electron spin resonance (ESR) measurements clearly indicate the formation of superoxide radical anions (O2.−) rather than singlet oxygen (1O2) during the photocatalytic reaction.

Tuning PtII‐Based Donor–Acceptor Systems through Ligand Design: Effects on Frontier Orbitals, Redox Potentials, UV/Vis/NIR Absorptions, Electrochromism, and Photocatalysis

“…This leads us to the conclusion that a similar catalytic cycle as already described in various literature reports is operating here (see Scheme ) . The platinum complex is photochemically excited and quenched by the isoquinonline, resulting in the monoanionic platinum complex and a cationic tertiary amine.…”

“…Cross‐dehydrogenative coupling (CDC) has gained considerable popularity among organic chemists as an atom‐efficient method for C−C bond formation . Inspired by previous works, which utilized platinum for this reaction, we wanted to test the synthesized complexes and investigate their photocatalytic potential . They were employed in the cross‐dehydrogenative coupling of N ‐phenyltetrahydroisoquinoline (ISQ) with acetone and nitromethane.…”

“… Tentative reaction mechanism for the CDC. Adapted from Chen, Fu, and co ‐ workers . (SET=single electron transfer).…”

Highly Efficient Triplet Photosensitizers: A Systematic Approach to the Application of IrIII Complexes containing Extended Phenanthrolines

“…Transitionm etal complexes as triplet-photosensitizingm aterials have potential applications in photovoltaics, [1][2][3][4] photocatalysis, [5][6][7][8] andu pconversion. [9][10][11][12][13][14][15][16] It is generally accepted that for triplet-sensitizing applications,t ransition metal complexes need to absorb stronglyi nt he visible region and to exhibit long-livedtriplet states.U nfortunately,d espite some exceptions, [14,16,17] transition-metal complexes with these properties are unusual.…”

“…Transition metal complexes as triplet‐photosensitizing materials have potential applications in photovoltaics, photocatalysis, and upconversion . It is generally accepted that for triplet‐sensitizing applications, transition metal complexes need to absorb strongly in the visible region and to exhibit long‐lived triplet states.…”