A series of my compounds based on triazoles seem to like to crystallise from hot MeCN but they do in very thin needles forming kind of pompoms.
Anyone have any tips? Tried vapor diffusion, layering and so on with several solvents but the best still seems to be crystallisation from MeCN.
Cheers
Dear Sir;
I don't if you have tried dynamic crystallization (by shaking or agitation) and low temperature crystallization, these two tips sometimes gives bigger crystals. Also there is a process named biomineralisation in which the crystals formation is induced and oriented by a matrix such as a polymer, but again I am not sure this works under the environment and conditions you are working in. Regards
If your material melts congruently, then you can try to grow bigger size crystals by melt growth methods like Bridgman and micro tube Czochralski (Using these methods we can grow bulk crystals without the seed crystals). All the best!
I think you will need to change your solvent system from CH3CN, it is hopeful that it is trying to crystallize but it is not giving you decent shape or size crystals. You could try a mixture of solvents, what about BuCN or maybe THF? It looks like if its only going into CH3CN hot then its not too soluble in that so its coming out rather qickly on cooling, you could try and slow down the cooling rate maybe suspend flask in a water bath and slowly reduce the temperature of the bath, sometimes I leave it on a warm hot plate stirrer and switch off the stirrer. The other thing you could try is varying the shape of the flask, NMR tubes are particularly good at affording crystals. There is no simple answer to your question but good luck with it.
Plz mention size of crystal;As there are various methods for crystal growth or you can try to grow bigger size crystals by melt growth methods like Bridgman and Czochralski Method.
Dear Jordi,
If your compound is also somewhat soluble in MeCN at room temperature, I would recommend to you vapour diffusion against tetrahydropyran (THP). More information, especially, how to proceed, if this hint is not helping you, you will find in our publication, a tutorial about the growth of single crystals: https://www.researchgate.net/publication/230751079_Some_thoughts_about_the_single_crystal_growth_of_small_molecules
Good luck!
Bernhard
Article Some thoughts about the single crystal growth of small molecules
As Melanie and Dariush suggested, slow cooling (low supersaturation) helps the growth of crystals. Seeding with few washed crystals can also reduce the supersaturation.
Melt crystallization can be used if the material do not suffer thermal degradation before its melt point.
Grow the crystals slowly and don't disturb the system. You also can try for seeding crystallization.
smaller crystals means that your solution is forming more crystallization nuclei. In order to prevent it, try to prolong the crystallization time by crystallizing in freezing conditions or you may also try to add some other solvent which is less volatile than your primary solvent and doesn't dissolves your compound.
Good luck.!
From my experience, vapor diffusion allows to obtain nice single crystal and is very convenient.
Some efficient solvent/ vapor counter solvent systems are : THF/pentane, THF/ether, CHCl3/pentane, CHCl3/ether, CH2Cl2/ether, DMF/ether, DMF/pentane, dioxane/pentane (and you can replace pentane by hexane in every cases). The best way to proceed is to filter your solution on cotton before starting the vapor diffusion to prevent the presence of insoluble particles in your media.
Good luck !
Dear Jordi,
I think most of the crystallization methods are reported in aforementioned comments, but you can try Hydrothermal method of crystallization method. In this method, using any solvent (mostly used water, as name suggests) you can heat your sample in Teflon lined autoclave at higher temperature (above 373 K) and then let it allow to cool at room temperature. You can use this method if your compound is sparingly soluble in organic solvents.
Just try it, you will be lucky to get required crystals..
Good Luck..
I think the earlier comments must have helped you to grow better crystals. As mentioned by you as your compound is soluble only in hot MeCN the best method is probably very slow cooling without disturbing your crystallization flask as any agitation may lead to crashing out your product. Even your crystals are needle like and may look small but might be good enough for modern day diffractometer.
Dear Sir,
The answers made by these experts already included many effective methods.
I am not very clear about what your target is. Is it about getting some conformation of a certain triazole compound? If so, triazoles crystalize well with many metal ions, such as Cu(II), by forming complexes or even MOFs. You can also try that to see if you get luckier. Hopefully, by changing the compound being crystalized would get you another lattice group, maybe it would crystalize as block crystals finally.
Good luck.
