Group 8 metal alkynyl complexes for nonlinear optics

TLDR: In this article, the nonlinear optical properties of Group 8 metal alkynyl complexes have been studied, with particular focus on results since 2003; structure-NLO property relationships have been developed, optical nonlinearities of multipolar AL complexes are described, and switching of the NLO response of molecules and molecular materials derived from Group 8 AL complexes is discussed.

About: This article is published in Journal of Organometallic Chemistry.The article was published on 2014-02-01 and is currently open access. It has received 73 citations till now.

Figures

Figure 17. Successive generations of dendritic complexes 30, 65 and 66. The wavy lines denote the two other identical branches of the dendrimers. [Ru] = [Ru(κ2-dppe)2].

Figure 1. Selected 4-nitrophenylalkynyl complexes (see Table 1 for specific composition). 5

Figure 29. Complexes 83a-c and 84 and photochemical grafting of 83a-c onto Si-H.

Figure 6. Complexes 35 - 39 ([Fe] = Fe(κ2-dppe)(η5-C5Me5); [Ru] = trans-[Ru(κ2-dppe)2])).

Table 5. Second-order NLO responses (± 15 %) by HRS at 1907 nm. β0 values

Figure 26. Complexes involved in SHG-active molecule-based materials.

Frequently asked questions

Q1. What are the contributions in "Group 8 metal alkynyl complexes for nonlinear optics †" ?

In this paper, the nonlinear optical properties of Group 8 metal alkynyl ( G8 ) complexes have been investigated. 

Q2. What is the effect of light on the electron density distribution of a 10molecule?

When a light beam, via its associated electric field E, interacts with the polarizable electrons of a 10molecule, it generates a distortion in the electron density distribution ρ(r), resulting in an induced dipolemoment μ. 

Q3. What is the effect of increasing the bridge length of the alkynyl ligand?

Earlier studies with alkynyl complexes had revealed that increasing the π-bridge length of the alkynyl ligand results in an enhancement in both the β and γ values [1,18,23-27]. 

Q4. What is the effect of bridge length on the ruthenium alkyny?

It was observed in earlier studies with organic molecules that nonlinearities saturate as the π-bridge length is increased, and this saturation length has now been assessed for ruthenium alkynyl complexes. 

Q5. What are the main uses of NLO materials?

When light interacts with materials possessing nonlinear optical (NLO) properties, the incident light can be modified (e.g. the phase, frequency, amplitude, polarization, path, etc..., of the incident light can all be changed); as a consequence, NLO materials have many possible applications (e.g. optical signal 5processing, switching, frequency generation, optical data storage, optical communication, and image processing). 

Q6. How many SHGs were measured at 1907 nm?

SHG values of ca. 3 pm/V at 1907 nm were measured with the samples containing 67a, which also corresponds to the most active complex. 

Q7. What is the common approach to tune the NLO activity using oxidized states?

The replacement of dppe by a redox-active ligand such as 1,1’-bis(diphenylphosphino)ferrocene (dppf) 10is another potential approach to tune the NLO activity using oxidized states. 

Q8. What is the significance of the presence of the metal in the quadratic NLO merit?

The presence of the metal is crucial to the quadratic NLO merit (there is an appreciable increase in βHRS proceeding from the organic acetylenes 22 and 28 to the corresponding organometallic complexes 23 10and 29). 

Q9. how many ethoxy groups were introduced on the ligand?

The introduction of the ethoxy groups on the ligand results in a reduction of 30 % of the magnitude of the second-order NLO response, but with four ethoxy groups (n’ ≥ 2), no further change was noted (within the error margins). 

Q10. How is the redox-switchable surface supported NLO-phores?

To access redox-switchable surface-supported NLO-phores, which are desirable but still challenging targets, an approach similar to that pursued with 80 has been explored, i.e. by grafting NLO-active alkynyl complexes with a pendant terminal alkyne unit onto p-doped SiH surfaces. 

Q11. What is the common method of tuning the NLO properties of metal alkynyl?

Modulation of the ligated metal donor strength 15One possibility for tuning the quadratic NLO properties of organometallics that was explored in the 1990s was the modification of the donor strength of the metal [1], usually via ligand replacement at the metal center, and this is an approach to varying β that continues to attract interest. 

Q12. How many redox-active dipolar compounds have been made?

Very fewattempts have been made, the first of which (to the best of their knowledge) being to deposit redox-active ferrocene-based dipolar compounds such as 80 (Figure 26) on a conducting (gold) surface and to then use it as a working electrode to switch the redox state of the donor group in the monolayer by electrochemical means [73]. 

Q13. What is the spectral dependence of the dipole moment on the electric field?

This dependence of the dipole moment on the electric field can be represented as a power series (equation 1):μ = μ0 + α E + β E E + γ E E E + … (1)where μ0 is the static dipole moment, α is the linear polarizability, β is the molecular first hyperpolarizability and γ is the molecular second hyperpolarizability. 

Q14. What is the effect of the substitution of carbonyl ligands on the donor strength?

Replacement of electron-withdrawing carbonyl ligands with phosphine ligands or cyclopentadienyl ligands by 20pentaphenylcyclopentadienyl ligands (Figure 1) increases the donor strength of the ligated ruthenium in 4-nitrophenylalkynyl complexes, with a concomitant increase in β value (Table 1) [14].