supramolecular

Question 1

chelate effect

Answer 1

ligands with more donors form more stable complexes than ligands with fewer donors

Question 2

macrocyclic effect

Answer 2

cyclic ligands have higher binding constants than acyclic analogues

Question 3

chelate effect reasoning

Answer 3

• entropy: displaces more ligands when added increasing entropy
• kinetic: donor more likely to coordinate/recoordinate when other donor already coordinated, i.e. proximity
• enthalpy: doesn’t need to overcome repulsion of positioning lewis basic donors together

Question 4

macrocylic effect reasoning

Answer 4

• Entropy: smaller loss in entropy on coordination due to less flexibility
• Enthalpy: less solvation and so less bonds need to be broken to coordinate

Question 5

podand

Answer 5

acyclic analogue of crown ether

Question 6

lariat crown ether

Answer 6

crown ether with pendant donor group

• stronger binding
• still labile

Question 7

complementarity

Answer 7

the size, shape, position, bonding, electrostatics of the binding site is ideal for the specific guest

Question 8

hydrophobic effect

Answer 8

• driving force for association of non-polar binding partners.
• The displacement of the water molecules increases entropy
• the increased hydrogen bonds increase enthalpy
  E.g. cyclodextrins, cyclophanes

Question 9

Job Plot / Method of Continuous Variation

Answer 9

[host]+[guest] = constant. The [complex] is then measured while varying the ratio [host]/[host]+[guest] and where it peaks in the Job plot is the host:guest stoichiometry

Question 10

Coalescence

Answer 10

• The transition between kinetically slow and fast binding. Occurs at some temperature.
• As the temperature is approached the individual peaks merge into a single time averaged peak.

Question 11

dielectric constant

Answer 11

• bulk polarity of solvent related to the dipole moment of the molecules
• high dielectric constant decreases electrostatic interactions

Question 12

hydrogen bond acceptor

Answer 12

good electron pair donor e.g. nucleophile, anion

Question 13

hydrogen bond donor

Answer 13

good electron pair acceptor e.g. OH/NH/FH

Question 14

thermodynamic template effect

Answer 14

coordination to a template stabilises the complex favouring its formation over other products (i.e. an equilibrium)

Question 15

kinetic template effect

Answer 15

coordination to the template arranges the components to favours cyclisation (rather than polymerisation)

Question 16

de-metallation methods

Answer 16

1. protonation (e.g. amines)
2. oxidation/reduction (increase lability)
3. solvation (with strong solvent)
4. ligation (with stronger ligand)

Question 17

optimal spatial fit

Answer 17

• strongest binding occurs when size of cavity and size of ion are complimentary.
• Smaller ions cause the macrocycle to strain.
• Larger ions cannot fit in the cavity and so have inefficient interations.
• Complexes of different stoichiometry may form though

Question 18

principle of preorganisation

Answer 18

The more highly hosts and guests are organised for binding and low solvation the more stable the resulting complex.

Question 19

calixarenes

Answer 19

• macrocycle of n phenols.
• Contain a pi bonding aromatic cavity as well as oxygen donor cavity
• Formed by base catalysed condensation of phenol and formaldehyde.
• May adopt cone, partial cone, 1,2 alternate, or 1,3 alternate.

Question 20

sepulchrates/sarcophagines

Answer 20

cryptand-like cages synthesised by ion templation e.g. octaazacryptands

Question 21

hydrogen bonding secondary interactions

Answer 21

• diagonal like hydrogen bond groups repel each other (due to electrostatics) weakening binding e.g. DAD or ADA.
• Adjacent donor acceptor groups stabilise complex and increase binding e.g. AAA or DDD

Question 22

solvent effects on binding

Answer 22

• if the sovlent interacts strongly with itself, favours binding.
• If solvent has high polarisability then will interact with host/guest inhibiting binding.
  e. g H20 is strongly cohesive and low polarisability i.e. hydrophobic effect

Question 23

self-assembly

Answer 23

• the aggregation of sub-components through intermolecular bonds to form larger structures under thermodynamic control
• reversible, error-correcting

Question 24

topological/mechanical bond

Answer 24

• a non-covalent bond that physically holds the components together.
• A chemical bond would need to be broken to separate the components.

Question 25

benefits of metal directed assembly

Answer 25

• strong, stable bonds
• controllable kinetics
• predictable geometry

Question 26

catenane synthesis

Answer 26

templated ring closing reaction

Question 27

catenate

Answer 27

• cantenane templated by coordinating a metal ion.

- Demetallation forms the catenand ligand

Question 28

atropisomers

Answer 28

stereoisomers arising due to hindered rotation around a single bond

Question 29

axial chirality

Answer 29

chirality due to rotation of molecule around an axis (clockwise or anti-clockwise)
no stereocentre

Question 30

amphoteric

Answer 30

capable of acting as a base or acid

Question 31

dynamic combinatorial chemistry

Answer 31

• method to generate of new molecules formed by reversible reaction of simple building blocks under thermodynamic control.
• products are determined by their thermodynamic stability.

Question 32

Rotaxane synthesis

Answer 32

• threading: stopper a psuedo rotaxane

- clipping: ring closing reaction around axle

Question 33

cryptand pros cons

Answer 33

• higher binding constant (less flexible, less solvation)

- less labile

Question 34

spherand pros cons

Answer 34

• very high binding constant
• no conformational rearrangement for binding (entropic/enthalpic)
• reduced solvation
• highly selective (cannot flex to fit other guests)
• slow complexation/decomplexation