title: Synthesis, structure, characterization, and photophysical studies of a new platinum terpyridyl-based triad with covalently linked donor and acceptor groups.
abstract: A new terpyridyl-containing Pt triad [Pt(pytpy)(p-CC-C6H4-NH-CO-C6H2(OMe)3)](PF6)2 (4), where pytpy = 4'-(4-pyridin-1-ylmethylphenyl)-[2,2';6',2' ']terpyridine and p-CC-C6H4-NH-CO-C6H2(OMe)3 = N-(4-ethynylphenyl)-3,4,5-trimethoxybenzamide, has been synthesized and structurally characterized. The related donor-chromophore dyad [Pt(ttpy)(p-CC-C6H4-NH-CO-C6H2(OMe)3)]PF6 2, where ttpy = 4'-p-tolyl-[2,2';6',2' ']terpyridine, and the chromophore-acceptor dyad [Pt(pytpy)(CCC6H5)](PF6)2 (3), where CCC6H5 = ethynylbenzene, have also been studied. The multistep syntheses culminate with a CuI-catalyzed coupling reaction of the respective acetylene with either [Pt(ttpy)Cl]PF6 or [Pt(pytpy)Cl](PF6)2. X-ray and spectroscopic studies support assignment of a distorted square planar environment around the Pt(II) ion with three of its coordination sites occupied by the terpyridyl N-donors and the fourth coordination site occupied by the acetylenic carbon. Although the parent compound [Pt(ttpy)(CCC6H5)]PF6 (1) is brightly luminescent in fluid solution at 298 K, dyad 2 as well as triad 4 exhibit complete quenching of the emission. The chromophore-acceptor (C-A) dyad 3 displays weak solution luminescence at room temperature with a phi(rel)(em) of 0.011 (using Ru(bpy)3(2+) as a standard with phi(rel)(em) = 0.062). Electrochemically, the donor-chromophore (D-C) dyad and the donor-chromophore-acceptor (D-C-A) triad exhibit both metal-based and donor ligand-based oxidations, whereas the triad and the C-A dyad show the expected pyridinium- and terpyridine-based reductions. Transient absorption studies of the dyad and triad systems indicate that although the trimethoxybenzene group acts as a reductive donor, in the present system, the pyridinium group fails to act as an acceptor.
authors.affiliation: Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
authors.forename: Soma
authors.initials: S
authors.lastname: Chakraborty
authors.forename: Thaddeus J
authors.initials: TJ
authors.lastname: Wadas
authors.forename: Heidi
authors.initials: H
authors.lastname: Hester
authors.forename: Christine
authors.initials: C
authors.lastname: Flaschenreim
authors.forename: Russell
authors.initials: R
authors.lastname: Schmehl
authors.forename: Richard
authors.initials: R
authors.lastname: Eisenberg
mesh_terms: D002244:Carbon / Q000737:chemistry; D004563:Electrochemistry; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D017671:Platinum Compounds / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D017671:Platinum Compounds; D002244:Carbon