tanabe sugano graphs Flashcards
what do orgel diagrams show
they show spin allowed transitions
between d1–> d4 and d6–>d9 electron configurations
whats do the tanabe sugano graphs show
they show spin allowed and spin forbidden transitions that can occur between d orbitals
in a tanabe sugano graphh,,, where is the hrous state term
its at energy 0 ,,, its at the end of the x axis
in a tanabe sugano graph,, whats is the x axis and what does each thing mean
its delta/B
delta being the ligand field strength and B being the RACAH parameter
the energy of electronic states depends on what
the interelectron interactions
aka repulsions or attractions
they can be represented by 3 racahs : A B AND C
describe the different racahs
A B C
BC = deal directly with energy levels
B represents the approx metal and ligand bond strength
B for
B for metal ligand bond strength
what do we use the tanabe sugano graphs to do
predict delta.oct and B
aka predict ligand field strength and the bond strength between the ligand and metal in a complex
first thing we need to do to look at the tanabe sugano graphs
we find the free state thing
remmeber when we want to look if smt is spin allowed what do we need to do
we need to look at the top left bit
if the number doesnt change its spin allowed
the graps between different energies is proportional to what
the enrgy diff between energy levels is proportional to the enrgy of that transition.
larger gap meanisn the transition requires lager energy
17200cm-1 vs 25600cm-1 what is higher in energy
the 25600cm-1
so the gap between these enrgy levels is bigger
when we write the transitions what do we need to include
the L term theyre a part of,, therefore u need to make sur eu only have one of each,, if u have more then u need to add the L term.
steps to finding info off a tanabe sugano graph
- larger energy / small energy = ratio value
- then choose a random point in the x axis and look at the two energy levels u chose and follow these to the y axis,,
- divide the large y axis number by the small y axis number to get another ratio and keep doing this untilcthe ratios kinda match
- then find B using E/B = that y value
- then find delta.oct using delta.oct /B = the random x axis point u chose!!
value for the B of a free metal ion
1000cm-1
value for B of a complex
<1000cm-1
ratio of B of a complex and in a free metal ion gives what
the nephelauxetic parameter
remember that B is the bond strength between ligand and metal
what is the nephelauxetic parameter doing
shows how the shared electron density of a metal ion changes with different ligands
the nephalauxetic parameter symbol and equation
beta = B (complex) / B (gaseous free ion)
what does a low B value imply
a low B value implies there is less interelectron repulsion on the coordinated metal ion
bc the e- are spread out more
bc of the overlap of the metal and ligand orbitals forming molecular orbitals.
what does a small beta value for the nephlauxetic parameter mean
some delocalisation of e- occurs from the metal to the ligand
the smaller the beta value for the nephlauxetic parameter,, the what
the more covalent character of the bonding between ligand and metal.
larger delta.oct means what
larger ligand field strength
aka probs a stronger field ligand
small B tells us what
more covalent character
consistent with backbonding
