Lecture 8

Question 1

What is a single molecule magnet?

Answer 1

• A molecule that can be magnetized in a magnetic field and will remain magnetized even after switching the field off.
• Magnetism is a property of the molecule itself. No interactions between molecules are necessary for this phenomenon.
• Slow relaxation of the magnetization is purely of a molecular origin.
• Can be dissolved in a solvent or a matrix and it will still show this property

Question 2

How are single molecule magnets explained?

Answer 2

• by considering the positive and negative overall spin as two potential wells that overlap
• can lose magnetism through thermal activation or tunnelling

Question 3

What are Ueff and Tb?

Answer 3

• activation barrier

- the temperature at which magnetic relaxation takes 100s

Question 4

Why are single molecule magnets useful?

Answer 4

• molecular switch

- demonstrating both quantum and classical behaviour so being useful in physics

Question 5

Which molecules form metallic Ln(II) complexes and what are their properties?

Answer 5

i) Ln = La, Ce, Pr and Gd
- Metallic lustre and high conductivity
- Very good reducing agents
- Ln3+(X-)2(e-) with the odd electron in the conduction band
- Conduction band is 5d and not 4f due to more effective orbital overlap and the stable [Xe]4fn5d1

Question 6

Insulating and salt like Ln(II)

Answer 6

i) Eu, Sm and Yb
- [Xe]4fn+1 configuration is more stable
- consistent with Ln2+(X-)2 structure

Question 7

Which Ln 2+ states can be accessed

Answer 7

• there is appreciable chemistry of Sm2+, Yb2+ and Eu2+
• low valent compounds of a number of lanthanides such as La2+, Ce2+ and Lu2+ are inaccessible.
• these assumptions have been overturned and by reducing organometallic complexes, - the entire Ln2+ series except Pm 2+ can be accessed

(with the exception of Pm2+) can be accessed.

Question 8

Which An 2+ compounds can be accessed?

Answer 8

U and Th