Dears,
I have system with Ln-Fe where Ln is (Ho or Dy) cluster caged by organic moieties.
We have carried out solid state PL-measurements as well as luminescence studies in different solvents.
The used solvents are
H2O, MeOH, MeCN, EtOH, CH2Cl2, DMSO, Acetone, DMF, THF, EtOAc, Et2O, Toluene, C6H12.
In case of dysprosium both cases (solid state and solution) lead to emission peaks. However, Holmium has not emitted in solid and emitted with solvents.
The crystal structure and TGA shows that there is 30H2O crystallized in the lattice of both. I think that there is a relationship between solvent type and the coordinated water.
In addition, we have seen different behaviour (solvents misscible in water, and solvents with low solubility in water). some peaks are splitted and new peaks have been shown. i.e. in Dy, 400-500 nm (sometimes broad or three peaks), in 500-600 nm ( a peak is shown in some cases).
How can I understand these experiments, article, suggestion, doing new experiments.
Now we are trying to heat the sample with doing luminescence at each stage to see the relationship.
any help is appreciated
There are effectively solvent effects.
Firstly, you have to be aware that complexes always dissociate in solvents, particularly in protic and polar solvents. For instance I have shown long time ago that DMSO is a stronger donor than water with respect to lanthanide ions. The different peaks/splitting you observe in solution may well come from the fact that you have different species in solution, since all has to be considered as being equilibria. And even if the interaction with the solvent is relatively weak, the mass action law has to be considered: the concentration of DMSO for instance is about 14 M in the pure solvent; that is very large compared with solutions, say, 0.01 M or of lower concentration!
Therefore before concluding on the spectroscopy, you would have to establish the speciation in solution, quite an involved task with your systems.
Also, the two Ln ions chosen are not that luminescent, particularly when water is involved either in the first or second coordination sphere (they are more OK for magnetic studies); a better ion could be Tb (avoid Eu because Fe quenches Eu easily).
Dear Bünzli
Thank you very much for your answer, the problem is that only Ho / Dy have been obtained. I now understand that the splitting is a result of many species in the solution which means a reaction between the solvent/complex which may be an a addition or decomposition.
For magnetism, all ac/dc have been carried out.
Now I suggest to dissolve the complex in the solvents then evaporate the solvents and dry it, and repeat the PL-solid state and see whether there is a luminescence in case of Ho which was absence. In case of no emission, then there is an interaction between solvent-complex without decomposition. In case of yes, then the complex is decomposing in the solvent, is this correct and make sense?
Well not necessarily. The solvent may simply replace lattice water molecules or coordinated water molecules, without decomplexing the ligand; but of course it can also do that.
Besides, Ho has very low luminescence (typically 100-1000 less luminescent compared with Dy), so that the experiment may not be very conclusive.
If you wish to see Ho luminescence, you may try to work with deuterated solvents.
Dear,
Let me focus on Ho only and leave Dy,
Ho has no luminescence in solid state - PL. However, as it can seen in the attachement, it has luminescent in various solvents.
Now I want to check that the same Ho complex is in both cases. Is this Turn-off, Turn-on behavior. ?
In addition, it will be nice if you send me a paper to follow the suitable experiment in such a case.
Ah, I thought you were discussing f-f transitions, but the spectra you show correspond to ligand emission (probably singlet state emission, at room temperature, but some systems also display triplet emission at rt in presence of heavy ions). Can you measure the lifetimes? Or enforce a short time-delay ( a few microseconds) to see if the emissions remains or disappear? In solid state the absence of luminescence may arise from intermolecular interactions.
P.S. AN important point: did you run blank spectra of the solvents alone, in the same experimental conditions as for the complex?
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