Solubility Properties

Transcription

1 Solubility Properties X-ray crystal structure of : dicyclohexyl[18]crown-6 and potassium complex of [18]crown-6. Structures are different: In the solid state In polar and apolar solvent As a complex 1

2 Solubility Properties Structure a is unrealistic, why? 2

3 Solution Applications 3

4 Solution Applications 4

5 Solution Applications X A K A Crown ether Reaction of potassium salts with benzyl chloride in acetonitrile (X= Cl, A= anion,e.g.acetate). Free, desolvated anions in organic solvents All anions have a similar nucleophilicity 5

6 Solution Applications 6

7 Selectivity of Cation Complexation 7

8 Selectivity of Cation Complexation 8

9 Selectivity of Cation Complexation 9

10 The template Effect 10

11 The template Effect 11

12 High-Dilution Synthesis Cyclization rate: r c = k c [X Y] Polymerization rate: r p = k p [X Y] 2 12

13 High-Dilution Synthesis Cl H 2 + C Cl High-dilution H 2 C H H C LiAlH 4 H H High-dilution synthesis of diaza(18)crown-6.ote the use of acid chloride groups to enhance reaction rate. 13

14 14 High-Dilution Synthesis H H 1+1 Fe Fe Cl Cl Fe Fe Fe Fe Fe (3.56) 3+3 Simultaneous(1+1),(2+2) and (3+3) cyclococondensation in bipyridyl-based cryptands 2+2 (3.54) (3.55) +

15 Kinetic and Dynamic Effects ne of the few kinetically stable complexes X-ray crystal structures of free spherand 3.30 and its Li + complex K = k 1 /k -1 k 1 = 8*10 4 (M -1 s -1 ) k -1 =<10-12 (s -1 ) total desolvation leads to a high transition state Cation receptor: slow kinetic, large stability constant Cation carriers: fast kinetic, lower stability 15

16 Soft Ligands for Soft Metal Ions 16

17 Soft Ligands for Soft Metal Ions 17

18 Soft Ligands for Soft Metal Ions 18

19 Soft Ligands for Soft Metal Ions 19

20 Soft Ligands for Soft Metal Ions 20

21 Soft Ligands for Soft Metal Ions X-Ray Crystal structures of the Ag + complexes of [18]crown-6 and its sulfur analogue 21

22 Soft Ligands for Soft Metal Ions Macrocycle Synthesis through Schiff s Bases Thermodynamic equilibrium Template effect H H H H i(cl 4 ) 2 i 2+ KC H H H 2 H 2 + H H H H + i(cn)

23 Soft Ligands for Soft Metal Ions + H 2 H 2 Mn 2+, Mg 2+ (a) Ba 2+, Pb 2+ (b) M + M + 23

24 Complexation of rganic Cations 24

25 Complexation of rganic Cations

26 Complexation of rganic Cations 26

27 Recognition of H 3+ (CH 2 ) n H

28 Calixarenes p-tert-butylcalix[4]arene Conformation Cone conformer is most effectively stabilised by intramolecular hydrogen bonds Interconversion is slow on the MR time scale at r.t. (ca 150 s -1 ), but readily observed at 60 C 28

29 Calixarenes n H H * CH 2 CH 2, H + * + * H CH 2 * CH 2 H n CH 2 Bakelite * CH 2 * H n R R R R R R R R HAc, HCl H C H 2 H C H 2 H C H 2 H C H 2 H H H H H calix[4]arene 29

30 Calixarenes 30

31 Calixarenes Conformational analysis by variable temperature MR (VT MR) Suitable for energies in range from 20 to 100 kj mol -1, typical error ±1 kj mol -1 Lower temperatures: separate peaks (process is kinetically slow on the MR time scale), broadening upon increase of temperature Coalescence temperature: peaks merge to single broad signal k c π ν = 2 k c = rate, ν = frequency separation between MR peaks (at lower temperature) k c k B T = e h k B = x J K -1 (Boltzmann constant), h = x J s (Planck s constant), T = absolute temperature (K), R = J mol -1 K -1 (molar gas constant) # ΛG R T Higher temperatures: single signal becomes sharper 31

32 Calixarenes X- ray structures of a a + complex and a Cs + complex of calix[4]arene Two binding pockets: an hydrophobic And a spherand like 32

33 Calixarenes Fast intramolecular Ag + tunneling is observable by 1 H MR (coalescence temperature about -70 C) 33

34 Calixarenes 34

35 Calixarenes Bu Bu Bu Bu Bu Bu Bu Bu BIS(CALIX)CRWS Conformational aspects of cation inclusion Extraction experiments with picrates salts 1.Fast intramolecular cation exchange 2 days required for formation of the a komplex 2.Slow intermolecular cation exchange Bu Bu Bu Bu Bu Bu Bu Bu 35 Alkali metal intra- and intermolecular exchange processes

36 Carbon Donor and π-acid ligands 36

37 Carbon Donor and π-acid ligands 37

38 Carbon Donor and π-acid ligands 38

39 Siderophores 39

40 Siderophores Bu 2 Sn(C 2 H 4 ) 40

41 Siderophores 41