Hi Ramin,

The main problem is that one can hardly suggest you a solvent for a compound, having no idea about its structure.

As far as I remember you were going to synthesize a metal complex of tetraphenylporphyrin (TPP), although you didn't specify what is the metal ion.

If this is the case, then the problem with the solubility of the product and by-product could be expected from the very beginning.

In fact, you may not find a "good" solvent for this compound. Try benzonitrile under heating. But the best solution is to use a porphyrin with higher solubility, then TPP, e.g. the one containg alkyl groups in the aryl.

By the way it is not clear, why you think the crystalline material is a by-product. It could be a portion of your product, which crystallizes from the reaction mixture.

Hello Dr. Filatov ,

Thank for your answer. Yes this the product of my metal-porphyrin reaction.

I think I should try benzonitrile as you said. I'm not sure if the byproduct is crystals of the main product, because if they were the same, they should be soluble in the same solvent.

Ramin, it happens sometimes with these porphyrins, that the metal complex formed in the reaction spontaneously crystallizes from the reaction mixture. Such crystalline product can indeed be very poorly soluble and can by mistake be assigned as a by-product or starting material.

Try to submit these crystalls for X-ray. May be they are of suitable quality. Or try to grow better crystalls from the reaction mixture, e.g. by slow cooling or leaving for few days at  r.t.

Try DMF or acetonitrile (if benzonitrile is not fitted).

On the other hand (I totally agree with Mikhail Filatov) as by products you can only have (bis-metalo-porphyrins) because the excess of metal (???) salts can be washed with water.

These you may put into evidence in tautomeric equilibrium with your metalloporphyrin in UV-vis.

Firstly, you have to make purification by column chromatography (read about eluents and mixtures of eluting systems for different kind of silica or alumina columns). The red/violet or in case of Zr, MnIII (green) ring on column is your product.

I find it surprising that it is soluble in methanol and dichloromethane, but discomposes in other solvents.  I could see that happening with reactive solvents such as water, but if it doesn't decompose in methanol then why would it decompose in ethanol, isopropanol, or ether?  If it is stable in dichloromethane, then why wouldn't it be stable in dichloroethane, or chlorobenzene?

Dear Dr. Fagadar-Cosma,

Thanks for your answer, DMSO not worked well, shall I try DMF too? I agree with you and Dr. Filatov and I think I should sent both of them for XRD to make sure of their structures. Do you think the main product might form a rod-like nanostructure which leads to amorphous structure that justify our problem with crystal growing?

Dear Dr.Heirtzler,

Thanks, about your questions, I use porphyrin as ligand for the proposed metal in "M3+  2:3  TPP" ratio, the reaction happend in a 4h refluxing procedure in the present of normal organic base for dehydrogenation of TPP and make it suitable site for the metal to react. I can't draw a nice structure of what I meant to synthesize, but I think the attached photos might help a little (sandwich complex: TPP-M-TPP-M-TPP).

Dear Dr. George,

Thank you, you are right I should mention that the complex is insoluble in some solvents like H2O. Ethanol has not been tested so far. Instead solvents like aceton, toluene, n-hexan, etc which seems to be able to solve the product, actually decomposed it completely as checked by UV-Vis and Spectrofluorometry, which proves decomposition to the TPP. The best solvent for the main product was metanol so far, but growing the crystals of the main product still remains a big challenge here.

Yes you may try DMF, but the best choice for porphyrins is always CHCl3 and CH2Cl2.

Did you try them.

For me it is not clear the decomposition problem. Porphyrins and metalloporphyrins are stable in solvents. They might induce different type of H and J aggregation (CHCl3-rings) (THF-triangular platelets), and increased acid medium (pH

The question cannot be answered without any idea about the nature of your crystals. Anyway, the first problem could be solved as: 1) dissolving the mixture of products and reagents in DCM or methanol and then filtering off the byproduct. Therefore, you will get rid of it; 2) rotavaporing the solution to get the sample. 

As for the second problem, it is impossible to give you any advice without additional information. Sorry.

I'm still surprised that it decomposes in a non-reactive solvent such as toluene and hexane.  One thing you can try, rather than solvent diffusion or evaporation, is to cool a room-temperature solution in a freezer.

Dear Dr. Fagadar-Cosma,

I really appreciate your time and answers. Yes I tried CHCl3 and CH2Cl2 neither of them was able to solve the unknown product. Unfortunately DMF not worked too, and it still remained insoluble. do you think changing the pH might help?

Dear Dr. Adonin,

I know it's hard to answer, mixture of the products did not solve in the mentioned reagents, thats the key that we can separate them and that's some how the main problem here! I don't test rotary evaporator, I think it need some heating and that might decompose the product again.

Dear Dr. George, 

Thank you. About the decomposition, I attached the UV-Vis spectra of the synthesized product (RED), TPP as ligand (GREEN) and decomposed complex* (BLACK). Solvent was dichloromethane for all of them.

(*complex solved in other solvents and recrystallized, then solved in dichlorometane again for UV-Vis analyzing.)

For single crystal prep. - vapor diffusion of petrol ether into DCM solution of comp. 2 in NMR tube at RT.

Is the application of conc. H2SO4 or CF3COOh or CF3SO3H as solvent for 3 very crazy? (acid-base equilibria may be possible.

Or micro suspenzion in nujol for UV-VIS?

Dear Dr. Pazdera

Thank you for your answer. I'm afraid using high acidic solutions remove the metal from the nitrogens of the TPP. I have no idea about using micro suspension in nujol, would you mind explain more, how can I try that?

Dear Ramin,

see https://www.google.cz/search?q=nujol+suspenzion&ie=utf-8&oe=utf-8&gws_rd=cr&ei=IXx-VenTEIijU_DKgKgC#q=nujol+suspension and links herein. Nujol is standard medium for IR spectra. Microsuspension of your compound(s) should be suitable for measuring the absorption and emission spectra in the UV-Vis region where nujol does not absorb as paraffin.

If you were going to synthesize a metal complex of tetraphenylporphyrin (TPP), the methylbenzene or C6H5Cl with n-Heptane maybe your good choice...

Ramin: "I'm afraid using high acidic solutions remove the metal from the nitrogens of the TPP". - May or may not, TPP-Fe complexes are relatively very stable. Try both trifluorinated acid above, their anions are not good ligands as well.