Have you tried dissolving the compound in  a small quantity of DMF  and  adding some methanol. Then you can slowly evaporate the methanol  and see if you can get suitable crystals for Xray. 

thank you, Okpareke, I did try that already but the problem is that the crystals seem to turn to powder when cooled. I got some crystals at some point by using DMF as the solvent for the synthesis but the crystals quickly turn to powder on cooling. I tried washing with both hot and cold methanol but after that, the once shinny crystal became blurred or turn to powder on cooling. the crystals seem to be stable and good in hot DMF after synthesis but once I filter the whole thing goes to either powder or crystals that i cant use for X-Ray analysis. I tried washing with DMF when it looks like its the methanol that is causing the blurring but the crystals quickly dissolve.

DEAR, I AM NOT A CHEMIST BUT CHECK UJAM  FOR BMORE REFLECTION.

Have you tried diffusion method of diethyl ether into DMF? Sure it has worked for me in the past.

Small crystals can still be good from single crystal XRD. Seal immediately in glass capillary tubes with a small amount of the mother liquour and keep in fridge until measurement

sine you already got the crystals directly from the synthesis and on cooling turns opaque. I would recommend you to cool the reaction vessel very slowly (5 °C /hour). slow cooling may preserve the crystallinity.  you dont have to filter all the crystal, just keep them  in mother liqour and send few crystal in mother liquor to your crystallographer.

hope it may help you

Hi

try methylene chloride CH2Cl2 solution for your compound and use temperature decrease method of crystallization, as possible decrease the rate of cooling

Good luck 

Dear Timothy, I have also tried the dichloromethane diffusion with DMF but I didn’t try the refrigerating aspect. So, I will try that. Thanks

@Ahmad, thanks for that ideal of cooling at the rate of 5 oC/hr. I will also try that. However, I have tried measuring crystal from the mother liquor by using pipette to extract some crystals. The good thing is that I do the X-ray measurement myself and so I already tried getting the crystals from the mother liquor immediately after the reaction when the liquor was still hot because it looks like the crystal is stable in solution at temperature above the room temperature but after measurement, it seems what I had was poly crystal and in some case, twin crystals which made it difficult to solve the structure. So, I will try the cooling technique.  Thank you for your time.

@Kamal, do you mean using CH2Cl2 as the solvent for the synthesis or combining with the DMF? Thanks for your reply.

Dear David,

Try both methods

1- to use CH2Cl2 as the solvent for synthesis

2- combine CH2Cl2 with DMF and use it in different percentage 

compare which method give good crystal however in both cases try to decrease the rate of cooling as possible, I strongly recommend you not to getting the crystals out from the mother liquor immediately after the reaction while the liquor was still hot because it will make thermal cracks in the crystal due to the temperature difference.

preparing good single crystal may take days, don't disturb the solution, try to be patient

 avoid thermal cracking by change the temperature of the crystal suddenly

Good luck

Dear David

Here is a good link - As I said my preferred route was always the 'vapor diffusion ' method. As others have said   be patient it will take days

http://web.mit.edu/x-ray/cystallize.html

 Thanks Dr. Timothy, 

     The link was cool. I appreciate.