Ruthenium Alkynyl Complexes in Non-Linear Optics

Abstract

Non-linear optical (NLO) materials are able to modify the propagation characteristics of light. Such materials have a range of potential applications in advanced technologies and are therefore of considerable interest. This account summarizes the development of one class of organometallics as potential NLO materials, namely ruthenium alkynyl complexes. These are available in high yields by straightforward synthetic procedures and have good thermal and environmental stability. In studies ranging from small molecules (molecular weights ~1000) to second-generation dendrimers (with molecular weights of more than 20000), the author’s group and collaborators have assayed the NLO effects in complexes with a variety of ‘multipolar’ charge distributions (dipolar, quadrupolar, octupolar), revealing that ruthenium alkynyl complexes can be engineered to display record and near-record values of the parameters responsible for various interesting NLO effects. In particular, recent studies driven by the current focus on optimizing molecular multiphoton absorption cross-sections have afforded several examples with world-record values of these key coefficients. The author’s group has also shown that the fully reversible redox processes undergone by many ruthenium alkynyl complexes are a distinctive feature that can be exploited to afford molecular NLO switches, because the different and reversibly accessible redox forms of the complexes exhibit measurably different NLO responses. This unique type of switching has been extended in two ways to afford molecular switches with multiple accessible NLO states. First, ruthenium alkynyl complexes have been subjected to various ‘orthogonal’ (independent) switching stimuli (specifically oxidation–reduction, protonation–deprotonation, and photoisomerization), affording complexes that function as NLO switches with up to six distinct NLO states. Second, heterobimetallic complexes coupling ruthenium alkynyl and iron alkynyl centres have been prepared that exhibit multiple redox-accessible NLO states.

Transition metals induce control of enhanced NLO properties of functionalized organometallic complexes under laser modulations

“…All commercially available reagents were used without further purification. The starting materials, ferrocenylacetylene 32 , cis-[Ru(dppm) 2 Cl 2 ] 33 , cis-[RuCl 2 (PPh 3 ) 2 (4,4′-dimethyl-2,2′-bipyridine)] 34 and RuCl(dppe) η 5 -Cp 35 , (E)-N,N-dibutyl-4-((4-bromophenyl)diazenyl)aniline 5 36 and (E)-N,N-dibutyl-4-((4-ethynylphenyl) diazenyl)aniline 21,37 , 6 were prepared by literature methods.…”

NLOphoric Anthraquinone Dyes – A Review

“…The search for new and efficient NLO materials started nearly half a century ago and continues [4,39,43–51] . NLO materials are generally divided into three main categories, i. e., inorganic, organic, and organometallic [28] .…”

“…Numerous measurement methods exist, including Z‐Scan, [90] Kurtz powder techniques, [90] hyper‐Rayleigh scattering (HRS), [91] and electric field‐induced second harmonic generation (EFISH) [43] . The projection of the vector part of β on the dipole (μβ) dot product when an electric field is applied to a solution of an NLO‐active species can be determined using the EFISH technique, [43] which is the first approach used to detect the second‐order NLO properties of molecules. As an alternative, the HRS technique [91] measures the incoherently distributed second harmonic produced by an isotropic solution, enabling calculating the β×β tensor product mean value.…”

Solid-State Nonlinear Optical Properties of Mononuclear Copper(II) Complexes with Chiral Tridentate and Tetradentate Schiff Base Ligands

“…Among other organometallic [11,12,13,14,15] and coordination compounds [14,15,16,17,18], salen-type [19] metal complexes have been actively studied for their NLO properties, mostly for the last two decades [17,18,20,21,22,23]. The best functionalization of these derivatives has been achieved by inserting donor (D) groups on the salicylaldehyde (sal) moieties and acceptor (A) groups on the diamine bridge, such as substituted 1,2-diaminobenzene (phen) and diaminomaleonitrile (damn).…”