Title
HOMO–LUMO energy gap control in platinum(ii) biphenyl complexes containing 2,2′-bipyridine ligands
Abstract
A series of platinum(II) biphenyl 2,2’-bipyridine complexes containing electron-donating and electron-withdrawing moieties on the 4 and 4’ positions of the bipyridine ligand exhibit emission from excited states in the 600 nm region of the spectrum upon excitation in the metal-to-ligand charge transfer transition located near 450 nm. These complexes are distorted from planarity based on both single crystal structure determinations and density functional theory (DFT) calculations of isolated molecules in acetonitrile. The DFT also reveals the geometry of the lowest-lying triplet state (LLTS) of each complex that is important for emission behavior. The LLTS are assigned based on the electron spin density distributions and correlated with the singlet excited states to understand the mechanism of electronic excitation and relaxation. Timedependent DFT calculations are performed to compute the singlet excited state energies of these complexes so as to help interpret their UV-Vis absorption spectra. Computational and experimental results, including absorption and emission energy maxima, electrochemical reduction potentials, LLTS, singlet excited states, and LUMO and HOMO energies, exhibit linear correlations with the Hammett constants for para-substituents σp. These correlations are employed to screen complexes that have not yet been synthesized. The correlation analysis indicates that electronic structure and the HOMO-LUMO energy gap in Pt(II) complexes can be effectively controlled using electron-donating and electron-withdrawing moieties covalently bonded to the ligands. The information presented in this paper provides analysis and better understanding of the fundamental electronic and thermodynamic behavior of these complexes and could be used to design systems with specific applications.
Document Type
Article
Source Publication
Dalton Transactions
Version
Pre-print
Publication Date
8-27-2015
Volume
44
Issue
39
First Page
17075
Last Page
17090
Rights
© The Royal Society of Chemistry
Recommended Citation
Rillema, D. P., Stoyanov, S. R., Cruz, A. J., Nguyen, H., Moore, C., Huang, W., Siam, K., Jehan, A., & KomReddy, V. (2015). HOMO–LUMO energy gap control in platinum( ii ) biphenyl complexes containing 2,2′-bipyridine ligands. Dalton Transactions, 44(39), 17075–17090. https://doi.org/10.1039/C5DT01891A
Comments
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