Related Experiment Video
Updated: Feb 24, 2026
05:47
Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts
Published on: August 7, 2018
8.2K
Organoimido-Polyoxometalate Nonlinear Optical Chromophores: A Structural, Spectroscopic, and Computational Study
Ahmed Al-Yasari1,2, Nick Van Steerteghem3, Hayleigh Kearns4
1School of Chemistry, University of East Anglia , Norwich, NR4 7TJ, United Kingdom.
Inorganic Chemistry
|August 16, 2017
Summary
Organoimido polyoxometalate (POM)-based chromophores show significant nonlinear optical (NLO) activity, outperforming organic analogues with short π-bridges. However, extended π-conjugation diminishes their advantage over traditional nitro-based acceptors.
Area of Science:
- Materials Science
- Inorganic Chemistry
- Nonlinear Optics (NLO)
Background:
- Polyoxometalates (POMs) are versatile inorganic clusters with tunable electronic properties.
- Organoimido-POMs combine organic functionalities with POM cores, offering potential for novel materials.
- Second-order nonlinear optical (NLO) properties are crucial for optoelectronic applications.
Purpose of the Study:
- To synthesize and characterize organoimido-POM-based chromophores for NLO applications.
- To investigate the structure-property relationships governing their NLO response.
- To compare their performance against established organic NLO materials.
Main Methods:
- Synthesis of ten organoimido-POM chromophores.
- Hyper-Rayleigh scattering (HRS) for measuring NLO properties (β₀ values).
- Stark and Resonance Raman spectroscopies to probe electronic transitions.
- Density functional theory (DFT) calculations for theoretical insights.
Main Results:
- Significant HRS β₀ values (up to 139 × 10⁻³⁰ esu) were observed for chromophores with resonance electron donors, exceeding those of DAS⁺.
- Chromophores with short phenyl π-bridges outperformed the organic analogue N,N-dimethyl-4-nitroaniline (DMPNA).
- Extended π-systems (diphenylacetylene) showed comparable or lower β₀ values than the nitro analogue DMNPEA.
- Resonance Raman confirmed POM involvement in electronic transitions; Stark spectroscopy indicated dipolar character is essential for NLO activity.
- DFT calculations supported enhanced β in short systems due to charge transfer onto the POM.
Conclusions:
- The organoimido-POM unit acts as an efficient NLO acceptor but not a donor.
- Electronic transitions are strongly influenced by aryl group substituents.
- Organoimido-POMs offer advantages over organic acceptors with short π-bridges but not with extended conjugation.
Related Concept Videos
01:23Properties of Organometallic Compounds
1.8K
Organometallic compounds are compounds that contain a carbon–metal bond. Carbon belongs to an organyl group like alkyl, aryl, allyl, or benzyl groups. The metal can be from Group I or Group II of the periodic table, a transition metal, or a semimetal.
1.8K
03:02Colors and Magnetism
14.3K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
14.3K
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
3.1K
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
3.1K
02:52Stereoisomerism
14.2K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
14.2K
01:32UV–Vis Spectroscopy of Conjugated Systems
8.6K
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in...
One of the factors influencing λmax is the extent of conjugation in...
8.6K
02:34Structural Isomerism
21.8K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
21.8K