4c Flashcards
what do orgel diagrams tell us
they predict the number of dd transitions for d1-4 and d6-9 e- configurations
in both octahedral and tetrahedral ligand fields
what e- configuration doesnt have a spin allowed transition
the high spin d5 transition is a spin forbidden transition
why is the d5 high spin a spin forbidden transition
bc all the t2g and eg orbitals have 1 e- in them
meaning when a transition occurs from t2g to eg,, u need to flip the spin of the e-.
this changes the S value and therefore disobeys the 🔺S = 0 rule.
its also a dd trnasition which disobeys the 🔺L = +-1
its also not changing the symmetry of the orbital as its going from g to g in terms of gerade. so all the rules are disobeyed so the transition has tiny molar absorption coefficient of less than 0.2 M-1 cm-1
what does the orgel diagram show us
it shows us the number of transitions u can have when u apply a ligand field + split the ground state term to give u the resultant electronic states.
steps in an orgel diagram
find the ground state symbol
look at the orgel diagram and u can see the number of transitions u get when u apply a ligand field + split the ground state term.
it gives u a bunch of electronic states and transitions occur between these.
the larger the gap between the electronic states,, the larger the transition energy.
what do we need to do when we are finding the ground state term symbol
we need to max out S and L.
make sure u have as many spins parallel to eachother
make ure u put the e- in the larger ml values so wen u add them up u get a larger L value.
what e- configurations can be put on one orgel diagram
the ones that have the same L value for the ground state term.
aka d1 d4 d6 and d9 are all connected bc they have a D term for their ground state term.
what does the orgel diagram care about and what does it not care about
it cares about the L term of the term symbol!! e- configurations that give the same L value can be grouped together onto one orgel diagram.
the diagram doesnt care about the S value or the multiplicity value.
things just need the same L value.
same L value but different S values still go on one orgel fiagram
d2 d3 d7 and d8 have what L value
they have the F term for their L value
how many transitions should the F term have based on group theory
there should be 3 electronic terms when u apply an octahedral field
and therefore 2 different transitions
the orgel diagram for the F term also usually has what term with it
the F term normally has the P term with it aswell.
at a higher energy.
bc the ground state wil be F.. but when u dont do the ground state and put electrons in lower ml values so u dont max out the L value,, u get a P term!!!
this is obvs higher in energy bc ur not makxing out L,, meaning ur not draeing the ground state. and if ur not drawing a ground state ur obvs draeing an excited state.
what does ‘T’ mean for electronic terms
it means triply degenerate
aka there are 3 ways for arranging the parallel e- spins in the d orbitals.
the highest energy electronic term is what
the one thats least stable + normally ish singly degenerate ‘A’ term not ‘T’
the electronic levels are split based on their stabilities, explain pls
higher energy = least stable
e- probs put in the same orbital
e- put in the same plane are higher in energy
e- put in perpendicular planes are lower in energy
the energies of the electronic levels are due to what
they depend on what orbital the e- are put into.
in the same orbital = higher in energy due to interelectron repulsion leading to a loss in stability.
what do we mean when we say e- in the same plane experience more interelectron repulsion + therefore have their electronic level at a higher energy
it means that they both have xy character etc.
they arent in perpendicular planes.
RHS of the orgel diagram for D term has how many electronic levels and therefore how many transitions
there are 3 different energy levels and therefore 2 different transitions that can occur.
2 different vertical electronic transitions
when we are writing the transitions,, what do we need to make sure we include
the term symbol that level refers to.
bc there could be an F T1g term and a P T1g term.
so we need to make sure were labelling them so we can differentiate between the two.
okay so lets say the orgel diagram predicted 4 energy levels and therefore 3 different transitions,,, but the uvvis // abs spec only has 2 absorption bands,, why could this be true
the higher energy transition may absorb energy from a higehr energy wave.
aka a wave higher in energy than the uvvis region,, like xray or gamma ray.
the transition requires energy that is higher than the uvvis range.
what does E,, molar abs coefficient depend on
its the probability of a transition occuring.
aka if more selection rules are obeyed,, the transition is more likely to occur,, meaning the E value will be higher.
the E value for spin allowed ones is single digits,, from like 0-10 perhaps but like near the 5-6 area.
in an orgel,, whats the main difference between the LHS and the RHs
RHS = larger 🔺 value??
LHS = smaller 🔺 value
the order of the energy levels will be inverted.
aka the highest energy one on the RHS will now be the lowest energy pne on the LHS etc. theyre invertedddd.
how do we find S
and 1/2 or take away 1/2 dpending on the way e- are facing
how do we find L
we put the e- in the 5 dorbitals and label them with ml values.
we then add the m values,, make sure if u have 2 in a box u add the number twice
how do we find J
if less than 1/2 the orbitals are filled we do L-S
if more than 1.2 the orbitals are filled we do L+S!!!
when we promote e- what happens to them
we promote them to different configurations
if we want to see if a transition is spin allowed based on the energy levels the transition occured between,, what should we look at
the spin multiplicity,, aka the top left.
there will be a number and if the numbers match,, it means their spins stayed the same. meaning the transition is spin allowed.
🔺S=0 rule is obeyed.
quartet excited states are called quartet excited states due to what
their multiplicity being 4.
bc their spins are 1.5
how can u change the molar absorption coefficient
u can change the concentration of the solution.
