- Sergii V. Radio added an answer:How can I find the crystallographic information file (CIF) for a polyoxometalate?For a computational study, I need to have the CIF format of the molecule that I will use for simulation.I think that this cif-file will be more preferable for you because in this structure the hydrogen atoms were determined in a difference synthesis and refined in an isotropic approximation with geometrical limitations
(Journal of Structural Chemistry. Vol. 50, No. 2, pp. 296-305, 2009)Following
- Esmail Mousavi asked a question:How can I make a polyoxometalate molecule in Gauss view?I'm going to use polyoxometalate in a theorical study and need a software that can help make and display POM and it is possible for me to use Gaussian09 for calculations.Following
- Do you know examples of positive (cationic) polyoxometalates (POMs) (non Al-based or metal-organic)? ..POM, usually an anion, that consists of three or more transition (!) metal oxyanions...Following
- Dhrubajyoti Gupta added an answer:Does anyone have experience on P interference on W X-ray fluorescence and its dependence on W-P bonding and distance?We have observed that P can only interferes on W X-ray emission if they are part of the same compound. We believe there´s a non-radiative energy transfer process ocurring in our system and would like to discuss about these phenomena.Any standard reference: " Handbook of X-ray spectrometry" by Van Grieken & Markowicz..etc. You can look up the NIST web-site too for X-ray fundamental parameters...or X-ray "Fundamental parameters" library in google.Following
- Ian A Cade added an answer:What is the difference between a kinetic and thermodynamic product?I synthesized organic-inorganic hybrid material under mild hydrothermal condition with 15 lattice water molecules. Can I claim its thermodynamic product?The kinetic product is the product associated with the lowest energy barrier to its formation. The thermodynamic product is the most stable product with the lowest energy, irrespective of any intervening barrier (If the barrier to its formation is the lowest, the thermodynamic product may be the kinetic product as well). I have attached a sketch of an idealised reaction pathway highlighting these points.
Running your reaction at the lowest temperature possible (where it still proceeds) will tend to favour the kinetic product, as the starting materials will only just have enough energy to cross the lowest barrier to the corresponding kinetic product.
Conversely, running your reaction at a high temperature will tend to favour the thermodynamic product (provided that you don't simply decompose your starting materials, though strictly speaking this 'decomposition' would just be a particularly low energy thermodynamic product). This is because at 'high temperatures' the starting materials will all have enough energy to overcome any barrier en route to their lowest energy configuration.
These ideas can be applied to the previous answer: The use of a sterically demanding base (LDA) corresponds to raising the barrier to formation of the tetrasubstituted enol making it more difficult to form, despite being the most stable
The use of less than one equivalent of LDA, and allowing the reaction to equilibriate, corresponds to providing a different route to the thermodynamic product (via a lower barrier).Following
- Atharva Sahasrabudhe added an answer:How to grow good quality crystalsHello everyone, I am new to this group as well as to Polyoxometalate chemistry. So kindly bare with my naive questions. I am a sophomore student (2nd year) and have just started out my research in POMs. I want to develop some organic-inorganic hybrids with molybdates and take it further from there. Can the experts kindly give some tips to grow some good quality diffraction crystals as I am finding it difficult to do so.Dear H.N Miras,
Thanks a ton for your reply, was definitely helpful. My system is a POM-Ligand compound where the ligand binds to the metal centre through covalent intearctions. Will ask for your help/suggestions as and when I come across any blocks in my project.
- Chris R. Melville added an answer:POM Drawing SoftwareDear Group Members,
Could you recommend a drawing program to make POM structure representations, for instance like the one on this topic page? Ideally one that can integrate organic structures, and if it was cheap that would be icing on the cake.
Best wishes, ChrisDear Harry,
Thank you for your response; it is quite useful to me.
Best wishes, ChrisFollowing
- vanadium ions and vanadium oligomer vanadium ions or oxy-ions (with oxidation state 2, 3, 4 and 5 respectively) which are stable in aqueous solution. What about the formation of oxyanionic oligomers which are known to form in aqueous solution specially for V(V)?Following
- Hello, I am interested in the supramolecular chemistry of Vanadium(V)-oxoanions I am working on the synthesis and analysis of a photoswichable organic oxoanion-receptor, whose photoisomers bind different oligomers of vanadate. By fast repeated photoisomerisation one of the oligomers shall be enriched in an aqueous solution. Developing such a system I am applying Simulink-simulations to figure out the kinetic conditions and constraints. I try to analyse the complexes present in the system as well as their stability constants. Therefore I apply 51V-NMR titrations as well as potentiometric titrations, to whose results I am fitting the complex formation models to verify them as well as to determine the model parameters as the complex stoechiometries and the stability constants. To get an idea of the ligand exchange rates I apply 51V-EXSY-NMR.
At the moment I am also thinking about using ESI-MS to verfiy the stoechiometry of the complexes present in the equilibrium. But I worry that in the ESI-droplet there are totally different conditions compared to the solution making it impossible to draw conclusions from ESI-results to the complexes present in solution. Although some people in literature have done this. What do you think?
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