I have synthesised some copper(II) complexes with non conventional methods- mainly grinding method using pentadentate schiff base ligand. But I cant get a stable crystal and also the complexes dissolves in CHCl3, DMF other solvents like CH3CN, toluene, it is partially dissolving. I have tried diffusion method using DMF with diethylether but I cant get the crystal. Please any one help me to resolve the problem,
Hello, I don't think that DMF is a good solvent to try crystallization with, and usually there is no uniform way for crystallization, all by luck. But there is always a startegy to follow: with diffusion method you you can try a solution of your complex in CH2Cl2 or CHCl3 with pentane or ether, (usually for copper complexes CH2Cl2 / pentane works very welll) but you should prepare tubes with different concentrations and you can try at room and low temperatures. Good luck
Try changing the anion for your copper (II) salt, maybe a triflate?
The condition for crystallization can be very different for different complexes, which are largely depending on the peripheral ligands and charge type of the target complexes. Also, you need to consider the possible weak interactions (such as H-bond, pi-pi interaction, hydrophobic effect, etc) in different molecules or solvent molecules.
[i]For optimum growth, the compound should be moderately soluble under crystal conditions. If it is too soluble, the compound will tend to get crystals growing in clumps.If it is not soluble enough, then there is not enough solute around to supply the growing crystal surface and it tends to grow small crystals.
[ii] Since your complexes are polar,follow a sequence- low polaity solvent to high polaity solvent. Then try mixtuers of the polar solvents in different proportions.If it does not work- try a mixture of a polar and a nonpolar solvent in different proportions.
[iii]There are many factors which govern the growth of single crystals but there are no hard and fast rules for obtaining crystals One of the principal problems in preparing the single crystals of the complexes is the maintenance of conditions that produce homogeneous conditions of composition and properties throughout growing process .
[iv] Lastly, remember the golden advise of our old teacher-“Neither the scholar nor the crystals should be under stress” .So go slow and cool slowly in shallower petri dishes.
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