Why you are adding mercury to it. Do not use unnecessarily toxic substances such as mercury. Instead try to understand why your ligand is soluble only in DMSO. Dissolve in small quantity of hot DMSO and add dichloromethane or methanol and see whether you get ppt. If yes, stop before it turns turbid and add a few more drops of DMSO to get clear solution and leave it at room temperature, closed, in a longer tube, where there is scope for equilibration of solvents due to the difference in volatility which can generate an ideal condition for condensation/crystallization.

If crystals are not coming, take a pointed spatula and scratch inner wall of the container or add a seed crystal of your ligand.

General comments about crystallization of metal complexes:

Here everything matters. Nature of the ligand, its structure, geometry, nature of the metal and its geometry, oxidation state, solubility of the complex, its nature: neutral, cationic or anionic. Based on these factors one should choose a right combination of solvents. A combination of polar and non-polar, most soluble and least soluble, and so on. In ionic complexes, size of the cation and the anion is also very important. if the anions are very small, try to replace them with bigger ones such as perchlorate, triflate, PF6-, BF4-, BPh4- etc., depending on the nature of the metal ion chosen.

Another important method is diffusion method.

Good luck with crystallization

Yes, it does.

Yes, nature of ligand affects crystallization process. Try to dissolve maximum amount of compound in very little amt of DMSO solvent (try to make the solution clear) and pour some volatile solvents above it just like layering. I hope you will get good crystal.

Good solution to forming solid.    In the attached article, we addressed why was stearic acid so soluble in such structurally diverse solvent as methanol and hexane, but not in acetonitrile.   Clear from this study that in any saturated solution,  the solvent is mostly inert.   Also clear that the reason different solid polymorphs of the same solid molecule exist is BECAUSE solvent ligands [can] favor some conformations versus others.   Aligned with Archisman  proposal, adding some volatile solvent just above the layering equals 1) decreasing the solubility of the solute in the saturated solution [solubility in mixture of  solvents lower than in pure DMSO] and  2) structure of solvent can be the nucleation site that has molecules of solute order at the molecular level which starts the pattern of nano to micro to macroscopic solid structures. .     . 

thank you Bojidarka B. Ivanova.

Archisman Dutta, thank you for valuable suggestion. I will definitely try it.

Dr. Schmidt,

thank you very much sir for the useful information.

Hi.

Try to incubate the favorable crystallization set up in different temperature?

Why you are adding mercury to it. Do not use unnecessarily toxic substances such as mercury. Instead try to understand why your ligand is soluble only in DMSO. Dissolve in small quantity of hot DMSO and add dichloromethane or methanol and see whether you get ppt. If yes, stop before it turns turbid and add a few more drops of DMSO to get clear solution and leave it at room temperature, closed, in a longer tube, where there is scope for equilibration of solvents due to the difference in volatility which can generate an ideal condition for condensation/crystallization.

If crystals are not coming, take a pointed spatula and scratch inner wall of the container or add a seed crystal of your ligand.

General comments about crystallization of metal complexes:

Here everything matters. Nature of the ligand, its structure, geometry, nature of the metal and its geometry, oxidation state, solubility of the complex, its nature: neutral, cationic or anionic. Based on these factors one should choose a right combination of solvents. A combination of polar and non-polar, most soluble and least soluble, and so on. In ionic complexes, size of the cation and the anion is also very important. if the anions are very small, try to replace them with bigger ones such as perchlorate, triflate, PF6-, BF4-, BPh4- etc., depending on the nature of the metal ion chosen.

Another important method is diffusion method.

Good luck with crystallization

The beauty of coordination complexes is that here everything matters. Nature of the ligand, its structure, geometry, nature of the metal and its geometry, oxidation state, solubility of the complex, its nature: neutral, cationic or anionic. Based on these factors it becomes very tricky to choose a right combination of solvents. A combination of polar and non-polar, most soluble and least soluble, and so on. Respected Prof Balakrishna Sir has given a comprehensive treatise to your problem

i got lucky most of the time by making the suspension of the compound to be crystallized in a solvent where it was sparingly soluble followed by adding a solvent in which the compound was fairly soluble to just clear the suspension to a clear solution followed by very slow room temperature evaporation over few days to weeks in some cases besides once i saw the tiny crystal hanging in solution i further slowed down the rate of evaporation by closing some pores for a good crystal may be it works in your system too.

keep trying and enjoying the thrill of the artistic work of crystallization.

Indeed, everything matters in crystallization. Please go through the above suggestions.

Dear Shreya Bhatt,

Independently of the solvent polarity mixture, the preferred polymorph speciation will be a function of energy. Each solvent-system will impose better or worth conditions for some special arrangements of the fully or partial soluble solid already present. That means, some conformations may be preferred only because you got lower final energy in the new arrange configuration.

That is the reason why you change, let say the polarity of your solvent system, and you may end up in a different polymorph, one specific co-crystal and so on.

Allowing your complex ligands to interact with your solvent system, will obviously pay some role in the final system energy configuration.

Crystal's engineering uses this principle to choose, or at least try to predict crystal properties using specific and unspecific solvent-system interactions with the solid in the system, previously crystallisation of the desired crystal.

Best regards,

WNM

Respected sir Dr.Balakrishna ,

thank you very much sir for the wonderful advice. I am adding mercury because i want the crystal of only ligand and ligand-mercury complex as well . Now the problem is same in both the cases. my ligand as well as the ligand-mercury complex have very low solubility in other organic solvents. In case of only ligand i tried so many times but i could not obtain the crystals by slow evaporation method. however i thought the presence of metal would facilitate the crystallization process and I could get good crystals in case of ligand-mercury complex, or am I wrong ???? but i will surely try the method u have said for only ligand crytallization.

one more question I have is that " in case of ligand-metal complex crystallization, which one could be more appropriate method. 1) to form the complex first, take the powder form and then proceed for crystallization or 2) take the ligand solution seperately and and adding the metal solution slowly to it and try the crystal formation with the metal in vivo itself.

Respected Dr. Ahmed,

perhaps you are right slowing down the rate would do more good. thank you.

In making a metal-ligand complex, stoichiometry can be critical.  Once in while, one can get by with just having one component in excess.  Other times,  the need is for precisely the right mole ration to be present, not just because much of what happens in chemistry is stoichiometry, but because an excess of any one component could preclude a clean single component solid forming i.e. at a particular mole ratio.