Organische Chemie I, Universität Siegen,
Adolf-Reichwein-Str. 2, D-57068 Siegen,
Tel: +49 271 740 4340
e-mail: kishore@chemie.uni-siegen.de
Multicomponent Supramolecular Self-Assembly in a Single Step
Michael Schmittel, Kishore Ravuri
Introduction
Nature displays a ubiquitous ability in assembling simple covalent molecules into tertiary supramolecular aggregates utilising diverse binding modes (hydrogen bonding, metal
-ordination, ππ-π
-π
metal coco
co-ordination,
interactions, salt bridges). An ideal mimic of natural self-assembly would involve a number of simple molecular components, each contributing specific molecular information as an input which,
self
which,
self-assembly
1
under equilibrium conditions would evolve one preferred, most stable
-assembly. Although a number of examples are known, 1 designing and accessing a multicomponent selfselfstable multicomponent selfself
self-assembly.
assembly still remains a difficult task. Herein we demonstrate a simple approach to one such assembly 5 via a single reaction step utilising orthogonal and non-interfering binding algorithms. As a
non
non-interfering
-DABCO binding motif.33
tool-kit we have used Cu++ directed heteroleptic bisphenanthroline complexation (HETPHEN)22 and the zinc porphyrinporphyrin
tool
porphyrin-DABCO
tool-kit
HETPHEN approach as a tool for supramolecular self assembly
Constituent molecular components
We have previously used the HETeroleptic bisPHENanthroline complexation approach to access a
variety of supramolecules in the nanometer regime.
R
N
Zn
N
N
OC12H25
N
[Cu (CH3CN)4]PF6
N
N
Cu
N
N
N
N
C12 H25 O
N
N
3
Br
2 nm
Zn
N
N
N
N
Zn N
N
N
N
4
NZn
N
N
Zn N
N
N
N
N
2
~6.0nm
N
N
N
N
Br
1
4.PF6-
Br
N
N
Cu
N
N
R
N
N
N
Cu
N N
N
N
N
2 : 1: 1 : 1 ( or 1.5) based on the principle of
maximum site occupancy.
Br
Br
R
N
Cu
N N
N
N N
N
N
Cu
N N
N
Br
N
N
Cu
N N
Fe
N
Br
N
Cu
N
N
Fe
N
Cu
N
N
Cu
N
N
Br
N
Br
Br
Fe
Michael Schmittel, Venkateshwarlu Kalsani, Kishore Ravuri,
Helmut Cölfen, Jan W. Bats, J. Am. Chem. Soc In Press
R
N
N
N Zn N
Fe
Fe
N
Cu
N
N
Br
N
N
Cu
N
N Br
N
N
R = C12H25
N
N Zn
N
Br
N
Fe
N
Cu
N
Fe
Fe
1,7 nm
Cu-Cu distance
M. Schmittel, R. S. K. Kishore, Org. Lett. 2004, 6, 1923-1926
M. Schmittel, V. Kalsani, D. Fenske, A. Wiegrefe,
Chem. Comm. 2004, 490-491.
5
2 nm
~3.5 nm
N
NN
Zn N
N
Br
N
N Zn N
N
N N
Zn N
N
N
Br
O
Br
N
N Br
N Zn
4+
.4PF6N N
N Cu
N
O
Br
Br
N N
UV investigations
~ 3.5 nm
N
Cu
N
N N
N
Cu
N
N N
Br
N
N Zn N
N
~ 1. 2 nm
O
N
N
N Zn
NN
Br
O
N
NCuN
N
~ 6.0 nm
0.35
0.25
ΔA
0.2
0,35
0.15
Abs
V. Kalsani, H. Ammon, F. Jäckel, J. P. Rabe,
M. Schmittel, Chem. Eur. J. 2004, 10, 5481-5492.
M. Schmittel, H. Ammon, V. Kalsani, A. Wiegrefe,
C. Michel, Chem. Commun. 2002, 2566 - 2567.
0,40
0.3
1.5
0.1
Absorbance
0.05
1.0
0
1
1
2
2
3
5
4
[ DABCO]/[ Porphyrin]
0,30
0,25
NMR investigations
0.5
0,20
0,8
PF6-
1,0
Por
UV titration of 6 against DABCO at μM
concentration.
N
N
Zn
N
N
Jobs plot analysis showing a 1:1.5
composition of 6 vs DABCO.
Mes-por
N
N
Zn
N
N
4
Br
N
N
Cu
N N
Br
R
7
N
N
Cu
N
N
Transoid
Pac-man
9.6
R
2',9'
5',6' a,a5,6,8
4'
7'
9.2
8.8
8.4
Phen
b,b
Mes
8'
8.0
7.6
(ppm)
7.2
1.0476
1.0376
0,6
Mole Fraction of DABCO
1.0947
0,4
nm
8.0468
640.0
2.2016
620.0
1.2812
600.0
2.3618
2.4385
1.4094
580.0
1.0443
0.9770
2.9709
7.5519
1.0341
2.1729
1.3604
560.0
1.0000
540.0
Integral
520.0
1.2826
1.2993
0,2
0.0
500.0
6.8
6.4
6.0
5.6
5.2
6
Constant
logβ
Supramolecular complex 6 was prepared and titrated against DABCO in order to investigate the nature of
the assembly 5.
K22
15.6 ± 0.8
K23
21.3 ± 0.4
K12
9.7 ± 0.2
1.5
6
5
-4.54
-4.68
4
int Area
1
3
2
Binding constants were calculated
using SPECFIT
1
0.5
0
0,0
0,2
0,4
0,6
0,8
1,0
1,2
eq DABCO
-4.30
Binding constants were calculated from titration data obtained from the Soret band shifts. The data fitted
well to a four state binding model which could be explained through a model below.
a)
2,0
b)
420
425
430
1,8
[Mrj]
1,0
0,8
30
1,4
[Mri]
[Dj]
≤
≤
[Di]
[Mrj]
[Mri]
....(i)
Complex
Sphere
Rod
χ
Abs
-4.90
1,0
0,4
0,8
25
0,6
1-Cu-Phenanthroline
0,2
K23
0,2
c
-7
-6
-5
Log[DABCO]
e
d
-4
-3
0,0
0,000
0,002
0,004
0,006
0,008
0,010
0,012
0,014
[DABCO]
a) The experimental data fitted well to a four state binding
model, (the solid lines represents simulated data and the dots
represent the experimental data).
b) Fitting of the NMR titration data to the four state binding
model obtained from the UV titration data
D (e-10) m-2s
0,4
K12
Diffusion coefficient (e-10m-2/s)
0,6
1,2
a
-4.70
1H NMR titration revealed that two signals shifted upfield at -4.54 and -4.68 ppm. The development of
the NMR signals levels off by addition of 1.5 eq of DABCO providing an assignable set of signals.
3
1,6
K22
-4.50
(ppm)
20
15
10
9.2
5+DABCO 1:1
5.5
5+DABCO 1:1.5
7.3
5+DABCO excess
8.9
5+Bipyridyl 1:1
5+Bipyridyl excess
5
0
2000
4000
6000
8000
12.2
5
6.2
12.2
10000
Mw
Further proof for the formation of the multicomponent supramolecular assembly came from diffusion coefficient
obtained from DOSY experiments on NMR. The calibration curve was obtained using equation (i) which is an
inverse relationship between the molecular weight and diffusion coefficient. It was clear from the curve that the
diffusion coefficient of 5 corresponded to a molecular weight ≅ 8000 corresponding to the composition predicted
Conclusions
Acknowledgements
Based on the principles of non interfering and orthogonal binding algorithms and
maximum site occupancy, we have obtained a multicomponent self assembly which
exhibits unique binding behaviour with DABCO.
We are greatly indebted to the Deutsche Forschungsgemeinschaft for financial support.
We acknowledge Dr. Thomas Paululat for assistance with DOSY experiments.
References
1(a) M. Schmittel, V. Kalsani Top. Curr. Chem. 2005, 245, 1-53. (b) Lützen, A. Angew. Chem., Int. Ed. 2005, 44, 1000-1002. (c) Vriezema, D. M.; Aragonès, M. C.; Elemans, J. A. A.; Cornelissen, J. J. L. M.; Rowan, A. E.; Nolte, R. J. M. Chem.
Rev. 2005, 105, 1445-1456. (d) Yoshizawa, M.; Nakagawa, J.; Kumazawa, K.; Nagao, M.; Kawano, M.; Ozeki, T.; Fujita, M. Angew. Chem., Int. Ed. 2005, 44, 1810-1813.
2(a) M. Schmittel, A. Ganz and D. Fenske, Org. Lett. 2002, 4, 2289-2292. (b) M. Schmittel, H. Ammon, V.Kalsani, A.Wiegrefe and C. Michel Chem. Commun. 2002, 2566-2567. (c) M. Schmittel, V. Kalsani, A. Wiegrefe, Chem.Commun. 2004,
490-491.(d) M. Schmittel, R. S. K. Kishore Org. Lett. 2004, 4, 2289-2292; (e) V. Kalsani, H. Ammon, F. Jäckel, J. P. Rabe, M. Schmittel Chem. Eur. J. 2004, 10, 5481-5492. f) V. Kalsani, H. Bodenstedt, D. Fenske, M. Schmittel Eur. J. Inorg.
Chem. 2005, 1841-1849 (g) M. Schmittel, V. Kalsani, J. W. Bats Inorg. Chem. 2005, 44, 4115-4117. (h) Michael Schmittel, Venkateshwarlu Kalsani, Kishore Ravuri, Helmut Cölfen, Jan W. Bats, J. Am. Chem. Soc In Press.
3 (a) C. A. Hunter and R. Tregonning, Tetrahedron 2002, 58, 691-697. (b) L. Baldini, P. Ballester, A Casnati, R. M. Gomila, C. A. Hunter, F. Sansone and R. Ungaro, J. Am. Chem. Soc. 2003, 125, 14181-14189. (c) M. C. Lensen, S. J. T. van
Dingenen, J. A. A. W. Elemans, H. P. Dijkstra, G. P. M. van Klink, G. van Koten, J. W. Gerritsen, S. Speller, R. J. M. Nolte, A. E. Rowan, Chem. Commun. 2004, 762-763.