Structures and Reactions of Diplatinum Complexes

Author: Darnton, Tania Victoria

Year: 2017

Degree: Dissertation (Ph.D.)

Advisor: Gray, Harry B.

Committee Members: Okumura, Mitchio; Rees, Douglas C.; Gray, Harry B.; Lewis, Nathan Saul

Option: Chemistry

DOI: 10.7907/Z9NK3C2J

Abstract

A d8−d8 complex [Pt2(μ-P2O5(BF2)4]4− (abbreviated Pt(pop-BF2)4−) undergoes two 1e− reductions at E1/2 = −1.68 and Ep = −2.46 V (vs Fc+/Fc) producing reduced Pt(pop-B2)5− and superreduced Pt(pop-BF2)6− species, respectively. The EPR spectrum of Pt(pop-BF2)5− and UV−vis spectra of both the reduced and the superreduced complexes, together with TD-DFT calculations, reveal successive filling of the 6pσ orbital accompanied by gradual strengthening of Pt−Pt bonding interactions and, because of 6pσ delocalization, of Pt−P bonds in the course of the two reductions. Both reduction steps proceed without changing either d8 Pt electronic configuration, making the superreduced Pt(pop-BF2)6− a very rare 6p2 σ-bonded binuclear complex. However, the Pt−Pt σ bonding interaction is limited by the relatively long bridging-ligand-imposed Pt−Pt distance accompanied by repulsive electronic congestion. Pt(pop-BF2)4− is predicted to be a very strong photooxidant (potentials of +1.57 and +0.86 V are estimated for the singlet and triplet dσ*pσ excited states, respectively).

Further study of the electronic excited states of Pt(pop-BF2)4- in the presence of luminescence quenchers revealed Stern-Volmer type dynamic quenching of the triplet state by trialkyl and triaryl amines. Quenching of the singlet as well as the triplet was observed in the presence of CoII trisbipyridine complexes, but sample decomposition and the observed presence of simultaneous static and dynamic quenching behaviors hampered quantitative analysis.

Files