Document Type

Paper- Restricted to Campus Access

Publication Date


Faculty Mentor

Brian Pfennig


To investigate photo-sensitive intramolecular electron transfers and spatially large charge-separated states in a supramolecular coordination compound, a covalently linked donor bridge acceptor complex was synthesized with the general formula: [dmbRe(CO)₃-μ-L-Pt(NH₃)₂-μ-L-Re(CO)₃deb]4+, where L=4,4-bpy. The donor substituent is a rhenium dimethyl polypyridyl linked through a square planar Pt(II) moiety to an acceptor rhenium diester polypyridyl. Emission of a photon is observed at 612 nm on the acceptor polypyridyl when the compound is irradiated at 338 nm, the wavelength of excitation from the Re(I) metal to the donor 4,4’-dmbpy ligand. It is hypothesized that this excitation of the metal-to-ligand charge transfer (MLCT) band from the donor Re leads to a Re(II) excited state with the electron in a π* molecular orbital of the donor 4,4’dmbpy ligand. Through a Förster resonance type mechanism due to the length of the molecule, the electron then undergoes a series of energetically downhill intramolecular electron transfers to lead to a spatially large charge-separated state with the electron lying on the diester polypyridyl ligand, the acceptor complex. We theorize that communication occurs from the conjugation in the 4,4’-bpy bridging ligands on either side of the Pt(II) moiety, which allows electrons to transfer from the donor complex to the acceptor complex. To tune these photo-sensitive intramolecular electron transfers, we are adapting the bridging ligand to have 3,3’-dimethyl-4,4’-bipyridine ligands on either side of the Pt(II) moiety. Since the dihedral angle between the two pyridine rings is 81.1°, this non coplanar conformation should slow the electron transfer or inhibit the transfer all together. We are currently working on a proper synthesis for this ligand, which will then allow us to analyze the absorption and fluorescence properties of the molecule.


Presented as part of the Ursinus College Celebration of Student Achievement (CoSA) held April 23 – April 30, 2020.

The main file is a narrated PowerPoint poster about our research for the spring 2020 semester.

Audio run time is approximately 9 minutes.


Available to Ursinus community only.