Inclusion of metal-organic complexes into cucurbit[8]uril Novosibirsk 2005 Tatiana V. Mitkina Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Av. 3, , Novosibirsk/Russia;

cucurbit[8]uril (CB[8]) C 48 H 48 N 32 O 16 cucurbit[n]uril С 6n H 6n N 4n O 2n n = 5  10 symmetry D nh The family of cucurbit[n]urils (CB[n]) 17.5 Å 8.8 Å 6.9 Å 9.1 Å dimensions of CB[8] molecule 2 2 Guests:

Possible approaches to synthesis of inclusion compounds of metal-organic complexes into CB[8] 1)“metal aqua-complex + scheme 2)direct reaction “host + guest” 3)“guest substitution” approach 3 3

+ Ni fold excess of NiCl 2 ·6H 2 O yellow crystals, yield = 89%, hot water soluble Synthesis of 2 ·16H 2 O 4HCl  18H 2 O 1)The approach “metal aqua-complex + Aqueous solution, reflux, 100°C, 2 h. 4 4

The structure of 2 ·16H 2 O 5 5  X-ray: square-planar environment of Ni II ; the angle between NiN 4 plane and equatorial plane of CB[8]  ~ 70°  ESI-MS: m/z = {[Ni(cyclam)] + CB[8]} 2+ Absorption spectra comparison: side view  IR: CB[8] vibrations

Ni II /Ni III oxidation within the CB[8] cavity. Synthesis of {[Ni III 4 ) 1.5 ·14⅔H 2 O {[Ni II 2+ + Ce 4+  {[Ni III 3+ + Ce 3+  X-ray cryst.: square-planar environment of Ni III ; the angle between NiN 4 plane and equatorial plane of CB[8]  ~ 70°  IR: CB[8] vibrations, (SO 4 2- ) = 1121, 619 cm -1  Solid-state ESR: low spin (S = ½) d 7 square-planar Ni III N 4 (!), А = 286 G, g x = 2.142, g y = 2.277, g z =  greenish-yellow crystals, water- insoluble, yield 88% 6 6 hyperfine structure ESR

cucurbit[8]uril 2) Direct approach “host + guest”

Synthesis of {trans-[M(en) 2 X 2 n ·mH 2 O (M = Cu II, Ni II, Co III ; X = Cl -, H 2 O) cucurbit[8]uril ) Direct approach “host + guest” 8 8

+ + Aqueous solution, reflux, 100°C, 2 h. CB[8]  20H 2 O dark-green crystals, yield = 97%, hot water soluble Synthesis of {trans-[Co(en) 2 Cl 2 2 O Selective inclusion of trans-isomer ! 2) Direct approach “host + guest” cis trans

Orientations of the ethylenediamine complexes inside the cavity of CB[8] NiCu Co 10 {[Co(en) 2 Cl 2 + {[Ni(en) 2 (H 2 O) 2 2+ {[Cu(en) 2 (H 2 O) 2 2+ Cl aq  = 16°, Ni–N 2.10 Å, Ni–O 2.13 Å  = 0°, Cu–N 2.00 Å, Cu–O 2.55 Å  = 90°, Co–N 1.92 Å, Co–Cl 2.24 Å

trans-{[Ni(en) 2 (H 2 O) 2 2+  = 2.92 Å (Ni–N = 2.10 Å) trans-{[Cu(en) 2 (H 2 O) 2 2+  = 0.42 Å (Cu–N = 2.00 Å) Å Å Å Å Ni Cu Distortion of CB[8] molecule upon encapsulation of guests

 X-ray cryst., elemental analysis  ESI-MS: m/z = 756 {CB[8] + Cu(en) 2 } 2+  ESR: g || = 2.212, g  =  IR: CB[8] vibrations  Dissociation upon dissolution in water: {[Cu(en) 2 (H 2 O) 2 2+  [Cu(en) 2 (H 2 O) 2 ] 2+ + СB[8] Cu Ni Co Cu Ni Co Solution and solid state studies of {trans- [M(en) 2 X 2 n ·mH 2 O (M = Cu II, Ni II, Co III ; X = Cl -, H 2 O)

 X-ray cryst., elemental analysis  ESI-MS: m/z = 510 {CB[8] + Ni(en) 2 + Na} 3+  1 H NMR: CB[8] resonanses became broadened and en signals disappeared upon inclusion  IR: CB[8] vibrations  Stable in solution  May undergo reactions of guest substitution 2X +   Y + {(X) X = Cu Ni Co Cu Ni Co

Cu Ni Co Cu Ni Co Solution and solid state studies of {trans- [M(en) 2 X 2 n ·mH 2 O (M = Cu II, Ni II, Co III ; X = Cl -, H 2 O)  X-ray cryst., elemental analysis  ESI-MS: m/z = 754 {CB[8] + Co(en) 2 } 2+  IR: CB[8] vibrations  trans  cis isomerization (120 ° С, 45 hours) Absorption spectra comparison: hypsochromic schift upon inclusion

CB[8] CH 2 (en) NH 2 (en) original complex inclusion compound H NMR-spectra comparison of D 2 O solutions of [trans-Co(en) 2 Cl 2 ]Cl and {[trans-Co(en) 2 Cl 2 2 O  = ppm  = ppm en resonanses are strongly upfield-shifted upon inclusion

Thermogravimetric data for {[trans-Co(en) 2 Cl 2 2 O, trans-[Co(en) 2 Cl 2 ]Cl and CB[8]  17H 2 O samples + 225° | medium: argon + T(decomposition of trans-[Co(en) 2 Cl 2 ]Cl) increased by 135°С upon inclusion into CB[8] + | 360° | 225° + + T(decomposition of trans-[Co(en) 2 Cl 2 ]Cl) increased by 135°С upon inclusion into CB[8] | 360° | | 225°

Violet crystalline powder, yield 60% ++ 2 Synthesis of {[Cu(dien)(4,4’-bipy)(H 2 O)] 4 ) 4 ·11H 2 O CB[8]}Cl 2 ·16H 2 O 10-fold excess of [Cu(dien)(4,4’-bipy) (H 2 O)](ClO 4 ) ) “Guest substitution” approach Water solution, reflux, 100°C, 3 h.

The X-ray crystal structure of {[Cu(dien)(4,4’-bipy)(H 2 O)] 4 ) 4 ·11H 2 O  X-ray cryst. structure, elemental analysis  Absorption spectra: (  ): 600 (185), 270 (sh), 240 (46200) ( =,   of free guest)  ESI-MS: m/z = {CB[8] + Cu(dien)(4,4´-dipy)} 2+  Solid-state ESR: g z = 2.312, g x = g y = (g || = 2.24, g  = 2.06 for free guest) – Cu-OH 2 become longer  IR: vibrations of CB[8], (С=С) and (С=N) 4,4´-dipy,  (R 2 N-H) dien, (ClO 4 - )

Conclusion Inclusion into the cavity of cucurbit[8]uril may be helpful for: 1) isolation of metal complexes with unusual oxidation states and coordination environments 2) stabilization of guest complexes in solid state and in solution towards thermolysis, isomerization etc.

Acknowledgements:  Prof., Dr. Fedin V. P.; Prof., Dr. Sokolov M. N. (supervisors)  Dr. Naumov D. Yu., Dr. Virovets A. V., Dr. Dolgushin F. M., Ph. D. student Kuratieva N. V. (X-ray crystallography)  Dr. Sheludyakova L. A. (IR)  Dr. Nadolinniy V. A. (ESR)  Dr. С. Vicent (ESI-MS)  Dr. Golovin A. V. ( 1 H NMR)  The laboratory of “Chemistry of cluster and supramolecular compounds”, IIC SB RAS