Two-dimensional, pyrazine-based nonlinear optical chromophores with ruthenium(II) ammine electron donors.
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.
School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK. b.coe@manchester.ac.uk
Benjamin J
BJ
Coe
John
J
Fielden
Simon P
SP
Foxon
Inge
I
Asselberghs
Koen
K
Clays
Bruce S
BS
Brunschwig
D003124:Colorimetry; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D004583:Electrons; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011719:Pyrazines / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*
D056831:Coordination Complexes; D011719:Pyrazines; D012428:Ruthenium