 Hello everyone and welcome back to the series of lecture on actinide chemistry. In the last lecture we have discussed about the term symbols and we have also tried to see that how we measure this UV visible spectra of any and give it to lanthanide or actinide and we have seen that the three type of transitions are possible in lanthanides and actinides that is intra-configuration transitions that we also known as FF transition, intra-configuration transition that is known as FD transition and the charge transition transitions. When we are having electrons in the F orbital then the two transition that is intra-configuration transition and intra-configuration transitions are possible. But in cases when we are having no electrons in the F orbital then whatever transition we see or whatever color we see in the compound that mainly come from the charge transfer transitions and one of the very good example of actinide that gives this charge transition is urinal ion because you will see urinal ion it has a X-ray system. So if you compare the electronic spectra of lanthanide and actinide the lanthanides have bit more sharper spectra but with a lower epsilon whereas actinides they are having a bit broader spectra and because of more diffusion nature of the FF orbital compared to the four orbitals they have more intensity and they are more participative in the reactions compared to the lanthanides. So let us see some of the spectra but yeah this is the term symbol that we have already calculated and if you remember then we have calculated the term symbol for European 3 plus which is an F6 system and we have seen that if you just calculate the term symbol for this you are getting 7 F is the term and if you just use the coupling we are getting a value from 0 to 6 and out of this 0 to 6 we have used the Hunch rule to get the established configuration of the ground shear configuration and there we have seen the ground state is nothing but 7 F 0 because it is less than half field and if you see this spectra the ground state is 7 F C. So here in this particular figure the ground state of all the trivalent lanthanides are given from where the transition will start up to almost 40,000 centimetre inverse and you can see for European it is 1 2 3 4 5 6 and again you start from the 7 F now you reach to the 5 D and then again 5 H and so on. Similarly if you just try to get it for neodymium that is and D3 plus which is an F3 system you will get a state that is 4 I9 by 2. I hope you can derive the state and you can at least say that out of different states that you drive using this term symbol that which one is the ground state because that is the state from where the transition will start because we are talking about the FF transitions and from there the transition will start and depending on the different selections rule that can apply for a given transitions we can get different transitions like this or this or this. We will just see some of the spectra that how they exactly look like when you record this spectra in the aqueous medium. So this is the particulate salt spectra and it is all to the water medium so you can say that starting from pseudonym then neodymium and then samarium. So you can see the both are having some FELopron so they are mainly having either FF transition or FF transition. As you have seen that the FD transition is merely prominent in serium, prosodinium and terbium. These are mainly dominated by the FF transition. If you just look carefully the spectra the first thing you can always see is the epsilon value is very low it's less than maybe 10 in many cases whether you choose any of the length and you see it in the tribal industry this is very low. This is because these are mainly FF transitions with the del L is equal to 0 so they are parity forbidden they are not allowed but because of some admixture of the different parity into the FF orbit we see this transition but again they are not allowed so they are having very weak intensities. Now one thing if you see very carefully that these are very sharp transitions and again the sharpness comes from the deep buried orbitals because we are in the transition is between the FNF orbitals so they are deep buried and not having much influence from the external environment. The other selection rule that we know that the spin change or you can say the spin change should be 0 and here you can again see that your initial transition or your round state is having spin multiplicity of 2s plus 1 is equal to 3 and if you see that a transition in which suppose this is not followed and again as I said that this is not allowed so if you are having this and this both possibilities that it is a laboratory forbidden and your spin is plus minus 1 but not 0 then it is called doubly forbidden transition and their intensity is again decreased to a large extent. I will just repeat it again clarity what I mean to say that this spin multiplicity should be same when you are having a transition if your spin multiplicity is changing in a transition their intensity was drastically because this is forbidden transition so ideally your delet should be 0 for a transition to be allowed and here again you can see your spin multiplicity is 3 and here it is 1 here here you can say there is a change so this is not allowed because of that the intensity is very weak but if you compare this with this these transitions are comparatively more allowed and having a better intensity obviously if you compare the same multiplicity then again the overlap between the orbitals and other admixtures come to the picture but generally if you are having a transition with the same multiplicity they are fairly more allowed compared to the transition which is changing both your there is no change in the effect or delet value and there is change in delet so this kind of transition is not allowed here again you can see we just see this spin multiplicity then it is 4 and whatever is with the 4 they are a bit more allowed compared to the one with the lower numbers here I mark a peak with the red color some of the transitions are very much affected by the environment although we say that these are the inner orbitals but still still they can have some influence on this kind of transitions and they are known as hypersensitive transitions this is one of the hypersensitive transition that is occurring in the Newtonian spectrum and people use this kind of transition to get information about the condition structure the metal legal complex the nature of metal legal complex around in any case you can see in solutions also I will again show you the spectrum of some area and in a very similar way you can see the spectra of other ion flight as in European and here you just remember this peak so very important peak when we talked about the Lewinson spectroscopy but just for that reason I just want to remember this that we have a transition from a 7F0 to 5F6 and that happens around 394 you see this is around 394 so this is one of the most prominent peak in the European 3 spectrum again you have different prominent peaks so but if they use one of those use of these transitions are and you can say the colors that you are getting you can see in all these we are having some transition in the visible region when I say visible region I'm talking about maybe 400 to 700 reason maybe in this reason and you can see there is certain peaks so always in this region there are some peaks and as I've told you in the previous life step when you are having some band it will give you something called spectral color when you have some spectral color the complementary color is visible to you and since all these are having some peaks in the visible region here again you can see in the list this again you see this is almost white if you see this I just remove this if you just draw this 700 and the 400 you can see there is almost no peak or maybe very small certain cases you can see so low so if you see most of the time if you have in European salt it is almost time colorless it is colorless similarly favorite a beam sword not very good color but if you take the oxide that is number two or three this is a very good blue color whereas most of them are colorless this you have some color because again you can see some transition to the visible region of the spectrum so whenever you see the transition in these region you can expect some color when you prepare solutions of this kind of lengthenite but if you are not able to see any peak in this region it should be colorless here I just try to compare the spectra of trivalent lengthenites with trivalent actinite here we have taken example of European and here it is American and we know that it is both as same as the system one thing you can directly see from the spectra is the epsilon value see the epsilon value it is less than four but here if you see the epsilon value sorry this is the optical density so we have to calculate the epsilon value using the relation is equal to PCL so absorbance you know from here you have to calculate and concentration is given so you can calculate this for the path length of one centimeter you can calculate and we found that the epsilon is very high so you can see that they are prevalent in nature European 3 plus and American 3 plus and since they are having environment of 4F and they are having environment of 5F and as we have said initially that the 5F is more diffusive and because of that the interaction or you can say that perturbation in 5F is more compared to the 4F so these transitions are more allowed or their epsilon is on the higher side compared to the transition in the length and height so this is one of the example I've given for the transition of trival and length and height where you can directly see that it's very difficult to tell about the broadness but in general the 5F should be more broad compared to the 4F but else in the scales are very different you may not be able to get it straight forward but their broadness should be on a higher side compared to the broadness that we observe into the length and heights so we have taken care of the trivaline let us see that how the tetragonal and tetragonal actinides look like because in length and height we are mainly talking about the trivalines because their group oxygen state is plus 3 but when you talk about the actinides you can have plus 2 to plus 7 let us see that how the other oxygen states will look like when you talk about the actinides and you see the actinides as I showed you that their oxygen state can be varied from plus 2 to plus 7 you see almost all the oxygen state have some color everybody is giving some beautiful colors and some of the real solutions that they put in the literature if you see those colors it is suppose you take the net union solution this is a net union in different state it is like from 3 to 7 so like 3 this is 3 this is 4 5 6 and 7 if you see there is a drastic change in the color when we are moving from 3 to 7 suppose you take the plutonium solution again there is a beautiful color that changes from the 3 to 7 and the more interesting thing you can see this diagram everybody is plutonium whole what we are changing is the media we are starting with an acyl media then perchloric acid then nitric acid and finally we are making some collides which is again in aqueous media of little higher ph so you can say although everybody is plutonium full still their color is different why because when we are having different kind of complexing anion into the media even they can very well interact in a very different way with the effect of orbiters of these plutonium ions and because of the splitting of those orbital in the presence of different kind of complexing anion they gave very distinct uv spectra and some of the lines are getting maybe allowed and some of the lines are getting forbidden and that causes change in the color because now we are having a different spectra different perturbations different experimental splitting in the presence of different kind of anion so you can see that just by changing the anion you can change the colors here and that shows that how strongly this f orbital the 5 f orbital has influence or how strongly it can interact with the external environment compared to the length and heights if you see the spectra nepunium 3 will look like this one nepunium 4 is again looks very different than nepunium 3 nepunium 5 then nepunium 6 one thing i just want to mention here if you see the spectra everybody looks a bit different from other suppose you see nepunium 4 it has two peaks but if you see nepunium 5 it is having only one peak and if you see nepunium 6 it is having a peak but in the anion region the peak position is around 125 in this case it is around nepunium 4 so it is around 964 it is around some 715 or so it is around 980 so you can see that every oxygen state has some different peak or you can say they have some distinct spectra so we'll try to use this information when we study the applications of this UV spectroscopy into the lanthanolytine chemistry do remember this that they have very different spectras again we have seen the spectras of nepunium with different colors and with different wavelength and here again just if you call it again with the color you can see this reason maybe up to 750 reason you are getting some peaks here here also you are getting some peaks so here you see although this intensity is very very low but still it is enough to give you very good color so whenever you have some peaks in this region then definitely you are bound to get some color into the solution and this intensity of the color will depend obviously depending on the epsilon or depending on the strength of these peaks that how strong these peaks are absorbing or strongly they absorb the light so depending on that you will get the corresponding complementary colors we'll see the UV spectra of the plutonium again I've shown you that from 3 to 6 when you go you are getting different color if you see the spectra then 3, 4 and 6 I have not shown you the spectrum of plutonium 5 and I hope by the time you are able to understand that all these 5 whether you are talking about plutonium 5 or unium 5 they are very unstable with respect to the disproportionation and because of that the getting spectra of plutonium 5 is not that straightforward it will get disproportionate and in the acidic solutions and if you are using too much of basics chances of hydrolysis is there so because of the disproportionation we are not giving the spectra of plutonium 5 and all these spectra were plutonium 3, 4 and 6 they are not that easy to form as I told you in the very beginning that one of the most stable oxygen state of plutonium that exists in water is generally plus 4 in the acidic media but since their eruptions are very close to each other so in solution you will get ideally all these 3, 4, 5, 6 everything should be there in the solution and 5 will again will be there but it will be disproportionate to 4 and 6 so we are mainly getting 3, 4 and 6 and then you have to stabilize them to get a spectra because you cannot have a mixture of all these things and you cannot record the spectra so you have to stabilize them before recording the spectra and these are some of the reagents that are commonly used for the stabilization for plutonium 3 we generally use hydroxylamine hydrochloride plutonium 4 it is the sodium nitrate and for preparing plutonium 6 solution we generally use an oxidant that is scl4 itself is acting as an oxidant we use this powder plutonium oxide or plutonium oxide solution in the solution form we add prakolic acid we do 2-3 time dry and then we again dry it and we again add scl4 we again dry it by the time we are not getting a spectra that is the characteristic of the plutonium 6 here I have given you the different peaks and their molar absorptivity for the plutonium solution here I just want to emphasize that if you see you are changing the medium and there is some change in the peak position and molar absorptivity that is because you are changing the ligand and that we have seen also when you are moving from scl2 a general 3 you can see there is some changes both in molar absorptivity as well as in wavelength and we will try to see that since I have shown you that when you are having a scl and this is scl and this is hn3 you can see almost one is you can say orange and one is green so you can see that just by changing from chloride to nitrate the color has been changed and first thing you just I want you to notice that if you are starting from plutonium 3 and going to plutonium 4 there is some spectral changes that I have already shown here when you are starting with plutonium 3 and plutonium 4 is having some spectral changes and when plutonium 4 and plutonium 6 there is again some spectral changes so if you are having plutonium 3 you can easily identify this yes this is plutonium 3 so if you add nitric acid to plutonium 3 or scl2 plutonium 3 there is change in these peaks with increasing acidity there are some changes and these changes directly correlate some interaction between plutonium 3 and nitric acid in plutonium 3 and chloride iron so to understand the kind of interaction and the nature of species that has been formed in different condition of different acidity frame we can use this kind of spectra here again the same thing is for the plutonium 4 like similarly we can see for the plutonium 6 also there is a constant decrease when you are adding scl because it will lead to formation of different species of plutonium in the hexavalent state so because of the change in the speciation there is a change in the spectral intensity nitric acid again there are certain changes and from these changes you are able to tell that yes the species are different the species that exist at one molar may be very different from the species that is existing at higher molarity maybe 9 molar acid in this case and 10 molar nitric acid in this case so in this table you can find that most of the actinides that we generally use in for our different kind of studies that they are like plutonium amyretium or neptonium and different conditions in which we generally prefer to store them or so the spectra that is in different conditions are given in the previous slide that is in nitric acid as well as acetyl medium but here we have just compiled the data in the perchloric acetyl medium why because the perchlorate that is acetylophore is having anion that is perchlorodion that is acetylophore minus and this is kind of a non-complexing anion and when we record spectra in this kind of anions what we assume there whatever spectra we are getting it is the spectra of the particular lanthanide or particular actinide having a very less perturbation into the their condition sphere because of the presence of perchlorodion so the levels are not very much get split it so we say that it is something not exactly free and but very close to the free end spectra and you can see that different ions have different lambda mix and different molar absorptivity constant for example if you say that neptonium 5 it is having major peak around 980 whereas if you see neptonium 6 it is having peak at major peak around 1225 again neptonium 4 is having peak at around 960 so just by recording the spectra you can see we are having information about the different lambda mix from the table you can get information about the different lambda mix and their e max and that is useful when you are trying to identify appropriate species or you can say a given species into a medium so these are the applications of the absorption spectra in general we use them for the we can use them basically for the qualitative analysis that you have a system suppose you want to understand that okay i have given you some system and you want to understand that what is the particular oxygen state suppose i give you some solution of protonium or any other actinide or lanthanide the first thing you want to understand that okay what is the oxygen state of the metal ion is there in the solution you can just record the spectrum and as i have shown you and you can see from the list and you can see from the previous spectra's that different oxygen states have different lines and just by looking the spectrum you have an idea that yes in my solution this is the most prominent oxygen state you can have a mixture also even in the case of mixture suppose i am having a mixture of neptonium 5 and neptonium 4 so if you are having a mixture of both suppose neptonium 5 and neptonium 4 then we know that neptonium 5 peak is coming around 980 and neptonium 4 peak is coming around 960 so even if you are having mixture of operation state just by looking at the spectrum you are able to tell yes this is the oxygen state that is present in my system so one of the very crucial information that you get is the qualitative analysis just by looking at the spectra you can get information yes this is the ion this is oxygen state that is present second thing is that can we make some quantitative analysis out of this answer is yes why because here in this table here in this table as you can see that we have given you the action and values for different metal ions you can see and we all know that from the lambert vietnolo e is equal to ecf suppose you measure you measure certain spectra again i am just taking example of neptonium suppose you measure neptonium spectra neptonium 5 you are getting a peak like this which is around 980 you get some absorbance and what you want to calculate what is the concentration of the neptonium ion in the solution and suppose you are getting a pure peak of neptonium 5 and you can just use this epsilon around 395 1 centimeter absorbance whatever you get from here and you can calculate the c so this can be used for the quantitative estimation as well in cases even if you are having a mixture then depending on the peak positions but suppose you are a mixture of neptonium 4 and 5 the neptonium 4 is coming somewhere here and neptonium 5 is coming somewhere here the 4 is around 960 this is around 980 even for the mixtures if the peaks are well dissolved you can easily get the quantitative information that okay how much of the neptonium is present in neptonium 5 how much of the neptonium is present in neptonium 4 so this can also give you information about the quantity so you can do some quantitative analysis also similar in the case with plutonium also you can do the quantitative analysis of any actinates that you want provided you know the epsilon in that particular media because epsilon do change depending on the media so to get the knowledge of the quantitative analysis one thing should be always taken care the media in which you are you want basically to get the quantity you should have the epsilon for that particular media we can study the redox reactions what i mean by the redox reaction we all know that they are very redox sensitive both actinates are a little more redox sensitive because lanthanide do have a plus 3 oxygen state in most of the line but the actinates are rather very redox sensitive and suppose i want to study some reactions let us assume that i want to study some disproportionation reaction of let us say example of neptonium only so we will have a spectra like neptonium and i want to study i have chosen this because it contains all the oxygen state of neptonium if you see this reaction you are having neptonium 5 you are having neptonium 4 you are having neptonium 6 and all these three neptonium 5 980 neptonium 4 around 960 neptonium 6 around the 25 all these things are there apart from each other and suppose i want to study the redox conditions in which this reaction is complete or i want to understand that at what acidity what is the kinetics of the reaction and how the reaction is going on what we can do we can start with this at a very zero time in this you will get only 980p but as the time will go on suppose you have fixed the acidity you are starting this piece so we can follow the redox reaction we can follow their kinetics we can also follow many times the mechanism in different kind of redox reaction using these peak informations and since we have shown that the even vary the positions and the epsilon's they do vary not very much but they do vary depending on the ligands you add so here i have just given you an example of some titrations that how the ligands will affect the complexations where just for example suppose you have a solution in which neptonium is coming around 976 nanometer this is the solution which i have specifically prepared in some kind of anyx solvents so the peak is not at 980 but a little on the lower side where suppose you have some transitions that is coming at certain peaks and in that particular solvents i have added some ligand and you can see that peak is shifting from the 976 to 991 so by the shift you can get yes some of the neptonium has been complexed and if you keep on adding the titrant or you keep on adding the ligand you get a spectra like this and we can use different mathematical equations to get the exact complexation constant between this neptonium 5 and that particular ligand and we can also get information about the epsilon of both neptonium 5 and neptonium 5 and whatever area you are going to use so those information we can directly get from the absorption spectra and detection and estimation of length and end in the environmental sample this is one of the very important things that we can do with this as many time you can see the e max is very high more than 100 many times you see so what does it mean it means that when you use an equation and you have a spectrophotometer which is quite good enough that you can easily measure 10 to the power minus 2 order of absorbance in the range of 0.01 I should say absorbance if you are having a spectrophotometer of this kind that can easily measure 0.01 then if you put this value as 0.01 and suppose you are epsilon for such a species let us say this is more than 1000 so you can say it is 1000 c into 1 so what you can see easily the c is nothing but 10 to the power minus 5 now look so where you can say even just by simple measurement you can get an idea about the concentration and that too a very low concentration because when we talk about the environmental sample the concentrations are very very low in fact much lower than whatever epsilon between power minus 5 and many a cases we use some chromophoric ligands such as the arsenal job to get in very high epsilon for that particular complex and for that we just mix the external length that we want to get the information of the concentration with that particular chromophore then we record and there the beauty is that the epsilon goes to as high as 10 to the power 5 and if your epsilon is such a high you can easily go to very very low concentration of the length and the length right and you can really see the samples into the environmental media with this I would just like to end up today's lecture and we'll meet in the next lecture thank you thank you very much