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Published November 15, 2010 | public
Journal Article

Two-Dimensional, Pyrazine-Based Nonlinear Optical Chromophores with Ruthenium(II) Ammine Electron Donors

Abstract

Six new nonlinear optical (NLO) chromophores with pyrazinyl-pyridinium electron acceptors have been synthesized by complexing a known pro-ligand with electron donating {Ru^(II)(NH_3)_5}^(2+) or trans-{Ru^(II)(NH_3)_4(py)}^(2+) (py = pyridine) centers. These cationic complexes have been characterized as their PF_6^− salts by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. The visible d → π* metal-to-ligand charge-transfer (MLCT) absorptions gain intensity on increasing the number of Ru^(II) centers from one to two, but remain at constant energy. One or two Ru^(III/II) redox processes are observed which are reversible, quasi-reversible, or irreversible, while all of the ligand-based reductions are irreversible. Molecular first hyperpolarizabilities β have been determined by using hyper-Rayleigh scattering (HRS) at 1064 nm, and depolarization studies show that the NLO responses of the symmetric species are strongly two-dimensional (2D) in character, with dominant "off-diagonal" β_(zyy) components. Stark (electroabsorption) spectroscopic measurements on the MLCT bands also allow the indirect determination of estimated static first hyperpolarizabilities β_0. Both the HRS and the Stark-derived β_0 values increase on moving from mono- to bimetallic complexes, and substantial enhancements in NLO response are achieved when compared with one-dimensional (1D) and 2D monometallic Ru^(II) ammine complexes reported previously.

Additional Information

© 2010 American Chemical Society. Received September 20, 2010. Publication Date (Web): October 20, 2010. We thank the EPSRC for support (Grants EP/E000738 and EP/D070732) and also the Fund for ScientificResearch-Flanders (FWO-V, G.0312.08), the University of Leuven (GOA/2006/3), and the NSF (Grant CHE-0802907, "Powering the Planet: an NSF Center for Chemical Innovation"). I.A. is a postdoctoral fellow of the FWO-V.

Additional details

Created:
August 19, 2023
Modified:
October 21, 2023