I have synthesized a ligand (HBH) whose Molecular weight is 281.26 and correspondingly cobalt metal complex have also been synthesized which is represented as [Co(HBH)2 ] Cl2. I need to calculate the M.W of above mentioned metal complex. My question is should I consider adding up the molar mass of chlorine atoms also which has not taken part in coordination process. I have seen in many papers , only the M.W of molecules within the coordination sphere is reported. If that is the case then should we exclude the molecules lying outside the coordination sphere during TGA analysis. shouldnt we consider their decomposition process . Plz help.
A coordination complex is not a fragment of something larger. It's a molecule, which consists of a central atom(s), ligands, counter ions, possibly water or solvent molecules. You should do the elemental analysis of your material to be sure that you have Co(HBH)2Cl2.
It will be better to go with the LCMS (Liquid Chromatography Molecular Spectroscopy) analysis, it will provide you with the exact molecular weight of the compound.
If possible try to grow the single crystals of the complex, because it will be devoid of any impurities and you can get the single crystal X-ray diffraction which will provide you the structure itself.
I have carried out GCMS and the M.W. obtained from the GCMS result doesn't includes any chlorine atoms.
Dear Lubna,
1. First to your initial question:
You can calculate the molecular mass and the mass spectrometry patterns best by using the freely available UMC (Universal Mass Calculator). You can download it here: https://www.uni-muenster.de/Chemie.oc/ms/downloads.html
2. LCMS stands for Liquid Chromatography + Mass Spectrometry (sorry Chethan)
3. For the MS you obtained so far:
Be aware that you have a dicationic complex [Co(HBH)2]2+ and two cloride anions in the structure in the solid. When you dissolve your neutral compound [Co(HBH)2]Cl2, you will have these ions in solution. In the MS experiment, you dissolve your sample (right?) and then submit it to the machine. MS detects cations. So you will detect the dication [Co(HBH)2]2+ and maybe the monocationic species [ClCo(HBH)2]+ if this is structurally an option (if Cl can additionally bind somehow to the Co center).
Definitely you will not detect the neutral salt-like compound [Co(HBH)2]Cl2 in MS.
I hope, I could help you.
Best
AXEL
Calculation of molecular weight of metal complexes is achieved by determining the elemental analysis which can be confirmed by Mass spectroscopy of the complex.
Molecular weight of the complex always include the counter ion. If you are employing ESI-MS / MALDI-TOF/FAB-MS you can calculate the molecular weight for both ionic and neutral complexes.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Powders