Yes, of course. You can grow large single crystals by gel growth method. In gel growth method either you can grow by reduction of solubility or chemical reaction method. For further details and doubts regarding crystal growth in gel, go through the book "Crystal growth in gels" by Heinz K.Henisch.

Try other solvents and mixtures of solvents.

Yeah i am trying that.... thanks for your valuable suggestion.... anyhow one f the compound was found to be brownish green in solution after dissolving in solvent. I am scared to put activated charcoal to decolorize it, as any damage to the compound may happen and also less yield. Please tell me whether slow evaporation at reduced temperature or boiling the solution and keeping for slow evaporation at room temperature would give any good crystal?

you can also try slow cooling, from room temperature to 4 degrees for example.

for the brownish compound, maybe it was oxidized in air?

Then cooling in a sealed vial could be helpful.

Thank you Dr. Jelsch.

I have now kept for crystallization at 21 degrees with new solvent. If this fails then i ll then go down to 4 degrees.

and the brownish compound was not oxidized in air. During elution itself it was in that color. I heard that mostly, the compounds eluted from plants may hav little amount of pigments in that and it can be removed by putting a piece of activated charcoal in the solution. But i am not sure whether the compound itself a pigment or anyother pigment is mixed with this compound.

Try by gel growth method using Silica gel as a medium or agar agar gel.

Gel growth method...? I am not familiar to that method. I wanna grow single crystal and do single crystal XRD as i am in crystallography department. Will this method be ok for growing single crystal?

Yes, of course. You can grow large single crystals by gel growth method. In gel growth method either you can grow by reduction of solubility or chemical reaction method. For further details and doubts regarding crystal growth in gel, go through the book "Crystal growth in gels" by Heinz K.Henisch.

The gel growth technique is a one kind of modified alternative version of solution growth technique. In which the growth occurs due to reaction between two suitable reactants (solutions) in a gel medium or achieving super-saturation by diffusion in gel medium. It is the simplest technique under ambient conditions. This technique is well suited for the crystal growth of compounds, which are sparingly soluble and decompose at fairly low temperatures. Crystals with dimensions of several mm can be grown in a period of 3 to 4 weeks.

With modern instrumentation, even very thin needles may yield decent X-ray diffraction data. If you have access to, or can find a potential collaborator who has access to a CCD diffractometer with a copper micro-source generator, or even a copper sealed tube system, your crystals may be big enough to give adequate data. Bigger, better crystals are always to be desired, and there are a number of crystal growing techniques which may prove useful, such as vapor diffusion with different solvents, but you may already have useable crystals.

Millimeter size crystals of organic compounds are perfectly suited for having excellent singla crystals X-ray diffraction with lab. equipments. Bigger crystals not only are not needed, but will absorb X-rays to a great extent.

@ Dr. Chetan Chauhan, Charles Barnes and Paolo Ghigna. thanks for all your suggestions.

How thick (or thin) are your needles? You must look at them under the microscope. Only by doing this, you might also detect, whether your needles are single. Single needles of organic compounds thicker than about 30 micrometers should be measurable by a copper CCD machine, as mentioned before. If you want to improve your crystals, you might want to have a look at our paper, a tutorial about single crystal growth:

https://www.researchgate.net/publication/230751079_Some_thoughts_about_the_single_crystal_growth_of_small_molecules

Article Some thoughts about the single crystal growth of small molecules

Thanks Bernhard. The crystals are flat and lengthy. I observed it under light microscope. Thanks for sending the link of your paper.... I ll try...

We have collect full data sets on crystals as small as 20 x 30 x 60 microns using our rotating anode and a CCD detector. For this to work the crystal MUST be single.

Another possibility is to use additives in crystal growth that can change crystal habit. An example of this is the use of triphenylphosphine oxide (see: Maxime A. Siegler et al., Acta Cryst., B63, 912–925 (2007)).

Thank you Dr. Deschamps. Ya we do have Bruker's single crystal XRD machine. The problem is to grow crystal from the compounds isolated from plants as the yield will be to low. Anyhow the use of additives to grow crystals is a good idea. Thank you.