At present I am working on low valent metal complexes. I am intended to determine their structures by X- ray crystallography. Therefore it would be helpful for me if you answer me the most appropriate methods of crystallization of low valent metal complexes to grow single crystals suitable for XRD.
Dear Shafikul, many thanks for asking this very interesting and important technical question. Growing single-crystals suitable for X-ray diffraction is often a more difficult task than preparing the respective compounds. I assume that you are equipped to handle air-sensitive compounds. The most common crystallization method is cooling of saturated solutions in organic solvents in the refrigerator or carefully layering such solutions with a non-polar solvent. Vapor diffusion techniques can also be tried within a glovebox. You can find a number of very useful crystallization guides in the internet. For example, please have a look at the attached articles.
Good luck with your work and best wishes!
Prof. Edelmann has provided vital information. There is no tailor made method for crystallizing a particular type of complexes. All available methods of crystallization are suitable for all types of complexes. Several factors influence the crystallization: (i) solubility, (ii) stability, (III) coordination number, (iv) type of ligands in the coordination sphere etc.
If the compound is sparingly soluble, diffusion or layering methods are ideal. If the compound is thermally stable, one can try for sublimation which gives fine quality crystals. Ideal method is after testing the solubility, use two solvents: i) solvent in which complex dissolves and ii) the solvent in which it is insoluble.
Take the compound in a small quantity of solvent dissolve it completely and if there are any suspended particle, filtered it through activated celite and add a few drops of pentane or hexane until you see turbidity. At this stage add a few drops of first solvent to make it clear and close the vial or flask in which the solution is made and keep it in refrigerator for a day to get crystals.
If the details are known many solutions can be provided.
Good luck
Balakrishna
I would only add that a convenient way to handle and mount air-sensitive crystals is to cover them with dry mineral oil. We used to sometimes use some of the oil sodium metal is packed in and put the crystals under oil in a Petri dish for viewing and mounting under a microscope, they will be ok for a few hours out in the room air that way. For mounting you can draw a crystal into a thin glass capillary, seal the end with epoxy or wax, and mount the capillary for XRD measurement.
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