In any mass spectra or mass interpretation in positive ionization Mass+one proton addition (M+1)and in negative ionization Mass-one proton (M-1) removal from the structure. M is the molecular weight of the complex/compound.

I am not exactly sure what you are asking. The ionization processed in a mass spectrometer is very different from those in solution, so you really cannot hope to recreate MS in NMR. You mention titrating, but the pKa of your material in solution (and whatever proton you hope to examine) will be very different from gas phase.

You should purify the synthesized complex and after that run a HNMR . you can used both the result ( Mass and HNMR ) for explanation of complex formation.

Saravanan: you will never get "protonated" 1HNMR signals for exchangeable protons of alcohols, amines, carboxylic acids, amides, etc. in D2O, d-MeOD. In d-DMSO you can also find some exchanges of mobile protons - slow, but noticeable. The water impurity and protons from the mentioned groups increases the HDO signals instead of the signal appearance of "protonated" form.

The protonation/deprotonation process is somehow different in ESI-MS and sometimes the less labile protons can be removed in ESI-MS while in NMR not.

In NMR you can try different temperatures, because the higher temperature accelerates the H->D exchanges of protons which are less mobile. Of course, you need to know that your structure - despite the covalent bond - is suitable for the exchange or not.

You may play with pH also in NMR.

You can get information also from this post:

https://www.researchgate.net/post/How_could_one_differentiate_between_a_covalent_bond_hydrogen_bond_and_coordinate_covalent_bond_in_13C_and_1H_NMR