title: Phenanthridine-Containing Pincer-like Amido Complexes of Nickel, Palladium, and Platinum.
abstract: Proligands based on bis(8-quinolinyl)amine (L1) were prepared containing one (L2) and two (L3) benzo-fused N-heterocyclic phenanthridinyl (3,4-benzoquinolinyl) units. Taken as a series, L1-L3 provides a ligand template for exploring systematic π-extension in the context of tridentate pincer-like amido complexes of group 10 metals (1-M, 2-M, and 3-M; M = Ni, Pd, Pt). Inclusion of phenanthridinyl units was enabled by development of a cross-coupling/condensation route to 6-unsubstituted, 4-substituted phenanthridines (4-Br, 4-NO2, 4-NH2) suitable for elaboration into the target ligand frameworks. Complexes 1-M, 2-M, and 3-M are redox-active; electrochemistry and UV-vis absorption spectroscopy were used to investigate the impact of π-extension on the electronic properties of the metal complexes. Unlike what is typically observed for benzannulated ligand-metal complexes, extending the π-system in metal complexes 1-M to 2-M to 3-M led to only a moderate red shift in the relative highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap as estimated by electrochemistry and similarly subtle changes to the onset of the lowest-energy absorption observed by UV-vis spectroscopy. Time-dependent density functional theory calculations revealed that benzannulation significantly impacts the atomic contributions to the LUMO and LUMO+1 orbitals, altering the orbital contributions to the lowest-energy transition but leaving the energy of this transition essentially unchanged.
authors.affiliation: Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba , 144 Dysart Rd, Winnipeg, MB R3T 2N2, Canada.
authors.forename: Pavan
authors.initials: P
authors.lastname: Mandapati
authors.affiliation: Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba , 144 Dysart Rd, Winnipeg, MB R3T 2N2, Canada.
authors.forename: Patrick K
authors.initials: PK
authors.lastname: Giesbrecht
authors.affiliation: Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba , 144 Dysart Rd, Winnipeg, MB R3T 2N2, Canada.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Davis
authors.affiliation: Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba , 144 Dysart Rd, Winnipeg, MB R3T 2N2, Canada.
authors.forename: David E
authors.identifier: http://orcid.org/0000-0001-8190-2468
authors.initials: DE
authors.lastname: Herbert