advanced coordination chemistry

Question 1

how to name crown ethers and explain the arrangement of [12]crown-4

Answer 1

first number = number of atoms in the ring
second number = number of oxygen donors

[12]crown-4
8 carbon atoms + 4 oxygen donors

Question 2

explain the solubility of crowns

Answer 2

they are soluble in all common solvents
if there was a mixture of water and ethanol the crown will dissolve into each equally due to change in conformation thus being hydrophilic and lipophilic to the solvent

Question 3

what are coronand complexes

Answer 3

coronand complex is a crown ether coordinated with an alkali metal

Question 4

why do the first five crowns have a binding preference to K+

Answer 4

because the number of donor groups increases with ring size, therefore there is an increase in enthalpy due to more coordination interactions

the larger cavity can accommodate K+ better as its a bigger ion and has more coordination sites

Question 5

what’s the difference between crowns and podands

Answer 5

podands are acyclic polyether analogues of a crown (the cycle is open)
podands have much lower binding affinity to metal ions due to Macrocylic effects

Question 6

what are cryptands

Answer 6

Cryptands are crowns with a bridge across the middle. naming is just the number of donor groups

Question 7

whats preorganisation

Answer 7

it enhances binding by minimizing the organisation cost for optimal conformation needed to bind to the guest.

Question 8

difference between cryptands and crowns

Answer 8

cryptands have higher binding affinity due to their increased affinities and they have a large preorganisation component

Question 9

why do cryptands selectively bind to specific metal ions?

Answer 9

cryptands cannot flex around ions that are too small for their cavity and they cannot expand for larger ions

Question 10

what are spherands

Answer 10

the most rigid macrocycle where there is a binding pocket where donor groups were held closely in the correct geometry for metal binding
the most preorganised hosts

Question 11

what is magnetic susceptibility and the equation for it

Answer 11

is a quantitative measure of the intensity of the magnetic dipole

fancy X = M/H
where M=magnetization and H=magnetic field

Question 12

what is the equation for molar susceptibility

Answer 12

fancy Xmol = k x Mr/10^3

where k is mass susceptibility (fancy X/density)

Question 13

what is the equation for the effective magnetic moment

Answer 13

µeff = sqr(n(n +1))
n= number of unpaired electrons

Question 14

what is diamagnetism and paramagnetism

Answer 14

Diamagnetism - material that generates a weak magnetic field in the opposite direction when exposed to an external magnetic field. M is less than H. fancy X is negative and the material is repelled by a magnet.
material with paired electrons are diamagnetic

paramagnetism - materials that are weakly attracted to an external magnetic field. M is more than H, then fancy X is positive.
only materials with unpaired electrons are para

Question 15

how are susceptibilities measured

Answer 15

the Gouy balance
consists of an accurate balance and a powerful magnet.
1. sample is measured in the magnetic field and outside it
2. difference in weight is the force the field exerts on the sample
3. the F is compared to known Xmol
4. so Xmol can be obtained for unknown sample

Question 16

how does temperature affect paramagnetic dipoles

Answer 16

magnetic dipoles tend to align and order themselves in a preferred direction, leading to a stronger overall magnetic effect. As the temperature increases, thermal energy disrupts this alignment, causing the magnetic dipoles to become more randomized and less ordered

Question 17

what is Curie law

Answer 17

magnetic susceptibility (χ) of a paramagnetic material is directly proportional to the reciprocal of the absolute temperature (T).

Question 18

what is Antiferromagnetism

Answer 18

In an antiferromagnetic material, neighboring magnetic moments align in opposite directions, resulting in a net magnetization of zero. This occurs due to strong exchange interactions between adjacent magnetic atoms or ions.

Question 19

how does temperature affect antiferromagnetism

Answer 19

When the temperature rises to the Neel temp the magnetic ordering becomes randomized

Question 20

explain what ferromagnetism is

Answer 20

exhibit a permanent magnetic moment, magnetic moments align spontaneously in the same direction, creating a strong net magnetization

Question 21

what is coercivity and hysteresis

Answer 21

coercivity - the ability to resist changes induced by the magnetic field
hysteresis - exhibiting a delay in magnetization changes and a memory of its previous magnetic state.

Question 22

how do charge transfer salt magnets work

Answer 22

anions and cations are small so they can stack close together in the solid state. close enough for spin interactions.

Question 23

what are lanthanides

Answer 23

are rare earth metals and in the bottom of the periodic table

Question 24

why are some lanthanide alloys have very strong magnetic properties

Answer 24

1. large number of unpaired f-electrons
2. very high coercivity

Question 25

what is the most stable oxidation state for lanthanides

Answer 25

3+ oxidation state

Question 26

explain the relationship between lanthanides and ligand orbitals

Answer 26

1. there is no overlap between 4f orbital and ligand orbital
   this means ligands pack around metal cations to minimise steric interactions.

Question 27

what does the decreasing radius across the group cause for Ln3+

Answer 27

1. increases bond strength due to higher charge density
2. reduce coordination number with smaller/heavier ion

Question 28

what are J values

Answer 28

a combination of L (angular momentum) and S (spin angular momentum)

Question 29

explain the energy term symbol 3^H6

Answer 29

S = 1 due to 2S+1
L = 5
J = 6

Question 30

explain the difference between f-f and d-d absorption spectra

Answer 30

f-f transition is narrow due to having no interaction with the ligand so its fixed.
d-d transition are broad because of ligand vibration.

Question 31

how does luminescence occur in lanthanides

Answer 31

emission of photons is the only way.
big energy gap = strong luminescence

Question 32

how to photoexcite Ln3+

Answer 32

1. absorption to give singlet excited state of ligand
2. intersystem to give ligand-ligand triplet excited state
3. energy transfer from ligand to f-f excited state
4. emission from lanthanide excited state to various components of the ground state

Question 33

what is the Nernst equation

Answer 33

E(bound) - E(free) = RT/nF x ln(K(red)/K(Ox))
E = cell potentials
R = Gas constant
T = Temperature
n = number of moles of electrons transferred
F = faradays constant (96485 C/mol)
K =

Question 34

what are the best metals to bind to the corresponding macrocycles in general
spherand
cryptand
corand
podand

Answer 34

1. spherand binds best with Li+
2. cryptand binds best with Na+ (selectively binds)
3. corand binds best with K+
4. podand is shite