Indeed, your 13C NMR spectra show a small extent of downfield shift for the alfa and beta C-Hs. This is usual by the coordination of NH2 as the shortage of electrons at the N is partially compensated from the neighboring atoms (in other words these will be less electron-rich.) The coordination of NH2 is also indicated by the strong down-field shift of your carboxyl signal on the 13C appering in the range of free acids. Based on your sent 1H NMR spectra I wouldn't dear to conclude a remarkable shift difference. The line broadening of the complexed and non-complexed aminoacids are different. Furthermore, it is not clear from your info what else could influence the chemical shifts of the protons of the complex.

We observed the opposite chemical shifts of 1H and 13C signals of thiourea and its derivatives as well as 1,2-diaminocyclohexane upon their complexation to Pt(II). These results were recently published in Inorg. Chim. Acta [Fang, J.; Wei, X.; Sapp, J.B.; Deng, Y.J.  “Novel platinum(II) complexes containing diaminocyclohexane and thiourea derivative ligands: Synthesis and X-ray crystal structure of (trans-1,2-diaminocyclohexane)dithioureaplatinum(II) nitrate monohydrate”, Inorg. Chim. Acta, 2014, 411, 5-10.]. You may wish to read the discussion about the opposite shifts.  

Dear Rituparna en Yuanjian,

I think these coordination-shifts are very much dependent on the (transition) metal itself and its valency (and the total outside electron number of its complex). Regards, Imre

Thank you Imre sir. Actualy sir, till now whatever inorganic synthesis i have done, i have always observed such differences in the NMR analysis. The 13C nmr spectra shows that, on complexation, all the signals for the carbon atoms, appear with a significant downfield chemical shift, along with significant downfield shifting of carboxylate carbon on coordination, if the ligands bind through carboxylate carbon in the complex. And, the 1H nmr shows all the resonances shift to higher field relative to the free zwitterionic form of the ligand. Sir, i wanted to know whether such opposite differences  in coordination shift for 1H nmr and 13C nmr occur for all complexes irrespective of the metal and the ligand used or are dependent on certain factors.

Thank you Yuanjian Deng. Yes, i have gone through those publications. Also, i have observed such differences in the nmr analysis of peroxo complexes in many research papers. so, i want to know if tahts the way with all complexes, if yes , then why? what always causes this downfield shift on complexation in 13nmr, but, upfield shift on complex formation in the 1H nmr.

The opposite NMR signal shifts seem common in coordination compounds because of the electron density shifts from one atom to another upon complexation. Let's take platinum-dach-tu complex as an example where dach = 1,2-diaminocyclohexan and tu =  thiourea [(NH2)2-C=S]. After the formation of the Pt-S coordinate covalent bond, there will be an electron density shift from sulfur to platinum, so the bond strength of the sulfur-carbon double bond (S=C) is weakened. Concomitantly, the electron density shifts from nitrogen to carbon. Therefore, the electron density on the nitrogen atom decreases while the electron density on the carbon atom increases. The 1H signals shift downfield from free tu's 7.12 & 6.91 ppm to 8.30 & 7.90 ppm while the 13C signal shifts upfield from 184 ppm to 176 ppm. For the dach ligand, due to the formation of platinum-sulfur (Pt-S) bond, the stronger trans-labilizing effect of the S atom weakens the platinum-nitrogen (Pt-N) bond. That is, the electron density now shifts from the platinum-nitrogen (Pt-N) bond to the amino nitrogen, leading to an increase in electron density on this nitrogen. Therefore, protons’ signals on this nitrogen are shifted upfield from 7.12 & 6.91 ppm to 5.84 & 4.89 ppm. I do not know the details of your complexes. However, if you consider the electron density shift in the bond(s), you should be able to explain the opposite NMR signal shifts.

Thank you Yuanjian Deng for your suggestion.

I'm not sure if there is need for any more explanation on this issue as most important points seem to have been covered by the above answers. In addition, I'm not quite sure I follow all the arguments here, because I haven't looked at the publications you've mentioned, and the NMR spectra look very blurry; worse still, the structures of the complexes under discussion are not visible to me. Still, I venture the following brief points:

- If by "zwitterionic" form of the ligand you mean the fact that the acidic proton is on the amine moiety, which would be natural, then right there is your explanation for why the proton in question (i.e., NH3+ vs. NH2) would appear upfield when the ligand is metal-bound, because in this case you no longer have an ammonium moiety but rather an amine moiety. If the latter is also coordinated to the metal (i.e., a chelating scenario), then the chemical shift of NH2 would be downfield of "free" NH2, but likely still upfield of NH3+.  

- The explanations given above are fine for the downfield shift of the carbon atom of the carboxyl moiety: electron density is transferred from this moiety to the metal and hence the carbon nucleus is less shielded.

Please feel free to correct me if I've misinterpreted the problem.

All the best with your projects.