Magnetism and Jahn-Teller
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What are the magnetic spin values of electrons?
+1/2 -1/2
What do electrons behave like?
Tiny bar magnets
What is diamagnetic?
All electrons are spin paired
How do diamagnetic complexes react with a magnetic field?
They are repelled
What is paramagnetic?
Complexes have unpaired electrons
How do paramagnetic complexes react with a magnetic field?
They are attracted
What is the spin only formula to work out the effective magnetic moment?
µ = √n(n+2)
What are the unit for effective magnetic moment?
Bohr Magnetons
What is n in the equation for effective magnetic moment?
Number of unpaired electrons
What are the only values n can have in the effective magnetic moment equation?
0 to 5
Why is measuring effective magnetic moment useful?
It can distinguish between high-spin and low spin and help determine co-ordination geometries
If an equation gives you a value of BM and asks you which ligand it would be, what must you do?
Work out what the BM is for high and low spin Whichever is closer is the right one Then assign which ligand would be high spin or low spin
What is spin crossover?
The spin state of complexes can change due to externam stimulus
What can spin crossover be initiated by?
Pressure Temperature
What is paramagnetism?
The spins are randomly orientated in the material
What is ferromagnetism?
The spins are all aligned Above a certain temperature, the thermal energy is enough to overcome the alignment and normal paramagnetic behaviour prevails
What is antiferromagnetism?
The spins become aligned anti-parallel which leads to a diamagentic material They are spin paired
What is ferrimagnetism?
Some spins are aligned anti-parallel to others but overall there is a finite magnetic moment in one direction
What is the Jahn-Teller effect?
If a ground-state electronic configuration of a non-linear complex is orbitally degenerate, the complex will distort as to remove the degeneracy and achieve a lower energy
What is a tetragonal distortion?
2 long bonds 4 short bonds