Ultraviolet-visible spectroscopy (UV-Vis), which is also known as ultraviolet-visible molecular absorption spectroscopy, uses a continuous spectrum of electromagnetic waves in the ultraviolet-visible region as a light source to illuminate samples. The UV-Vis spectrum is produced by the transition of valence electrons and has been widely applied to study the relative intensity of light absorption by substance molecules. Qualitative analysis can be carried out using UV-Vis spectrum, and quantitative analysis is also able to be completed according to Lambert-Beer law.
Figure 1. Experimental UV-vis spectrum of [Pt2Ag23Cl7(PPh3)10] (black) compared with the excitation energies and oscillator strengths calculated by TD-DFT for [Pt2Ag23Cl7(PPh3)10] (red). (Bootharaju, M. S.; et al. 2017)
Application of UV-Vis Spectrum
- Compound identification
It is possible to determine whether the molecular framework of organic compounds contains conjugated structural systems, such as C=C-C=C, C=C-C=O, benzene ring, etc.
- Purity determination
If the organic compound has no obvious absorption peak in the ultraviolet-visible region, but the impurity has a strong absorption in the ultraviolet region, the purity of the compound can be determined by UV-Vis spectrum.
• Determination of isomers
• Determination of steric hindrance
• Determination of hydrogen bond strength
It has a greater impact on the UV-Vis spectrum of the solute molecule when the solvent molecule associates with the solute molecule to form a hydrogen bond.
- Quantitative analysis
Our UV-Vis Spectrum Prediction Workflow
Alfa Chemistry has established a validated process for UV-Vis spectrum prediction:
- Optimization of the ground state structure and frequency analysis.
- Time-dependent density functional theory (TD-DFT) calculation on the ground state structure to confirm the excited state.
- Geometric structure optimization and frequency calculation for excited states.
- Frank-Condon analysis using the frequency analysis results of the ground state and excited state.
- In order to obtain an accurate prediction of the excitation energy, we consider the inclusion of solvent.
- We apply an implicit solvent included via a polarizable continuum approach to reproduce the excitation energies accurately.
- Our experts are capable of using both SMD solvent model and conductor-like polarizable continuum model (CPCM) to provide reliable results for our systems.
- At Alfa Chemistry, several solvation models (PCM, I-PCM, SCI-PCM and IEF-PCM) and functionals (CAM-B3LYP, LC-BLYP, BH, HLYP and PBE0) are available for our clients to select the optimal calculation condition for each project.
- Moreover, double and triple zeta basis sets with and without polarization and diffuse functions are also used.
Our UV-Vis spectrum prediction services remarkably reduce the cost, promote further experiments, and enhance the understanding of chemical process for customers worldwide. Our personalized and all-around services will satisfy your innovative study demands. If you are interested in our services, please don't hesitate to contact us. We are glad to cooperate with you and witness your success!
- Bootharaju, M. S.; et al. Doping-Induced Anisotropic Self-Assembly of Silver Icosahedra in [Pt2Ag23Cl7(PPh3)10] Nanoclusters. Journal of the American Chemical Society. 2017, 139(3): 1053-1056.