Self-assembling organic nanotubes from enantiopure cyclo-N,N′-linked oligoureas: Design, synthesis, and crystal structure

Article abstract of DOI:10.1002/1521-3773(20020603)41:11<1895::AID-ANIE1895>3.0.CO;2-3

Square-shaped hydrogen-bonded polar nanotubes are formed when the C₄-symmetrical all-S cyclotetraurea bearing side chains of alanine self-assembles in the solid state (see picture). The four urea fragments in the macrocyle present an all-trans

Full text of DOI:10.1002/1521-3773(20020603)41:11<1895::AID-ANIE1895>3.0.CO;2-3

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other residues. However, qualitative examination of the COSY
spectrum reveals similar vicinal coupling patterns.
In conclusion, by determining the solution structure of 1, we
have demonstrated that N,N'-linked oligoureas of general
formula B belong to the growing family of non-natural non-
peptide oligomers with defined and predictable secondary
structures. Although heptaurea 1 forms a (P)2.5 helix of
approximately 5.1 ä pitch that is closely related to the
(P)2.614 helix of approximately 5 ä pitch of corresponding
g4-peptides,[4a] it is worth noting that both NH groups within
the same urea linkage may participate in intramolecular
[9] D. A. Case, D. A. Pearlman, J. W. Caldwell, D. E. Cheatham III, W. S.
Ross, C. L. Simmerling, T. A. Darden, K. M. Merz, R. V. Stanton,
A. L. Cheng, J. J. Vincent, M. Crowley, V. Tsui, R. J. Radmer, Y. Duan,
J. Pitera, I. Massova, G. L. Seibel, U. C. Singh, P. K. Weiner, P. A.
Kollman, AMBER6, University of California, San Francisco, 1999
ˆ
ˆ
[10] Further experimental evidence for C Oi ¥¥¥ HN'i‡2 and C Oi ¥¥¥ HNi‡3
hydrogen bonds is gained from the determination of temperature
coefficients. N'Hi‡2 for i ˆ 1 4 and NHi‡3 for i ˆ 1 4 have temper-
ature coefficients with absolute values <4 ppbKÀ1, which indicates
limited solvent accessibility. In addition, temperature coefficients of
N'Hi‡2 for i ˆ 2 4 (3.5 ppbK À1 <À Dd/DT< 3.8 ppbKÀ1) have higher
absolute values than those of NHi‡3 for i ˆ 2 4 (1.5 ppbK À1 <À Dd/
DT< 2.5 ppbKÀ1). This trend could suggest an increased solvent
ˆ
hydrogen bonding to the same C O group. The knowledge of
the three-dimensional structure of 1 is likely to be useful for
the de novo design of oligoureas with controlled shape and
defined biological activities.
accessibility for N'Hi‡2 compared to NHi‡3
.
Received: October 1, 2001 [Z17991]
[1] S. H. Gellman Acc. Chem. Res. 1998, 31, 173 180; K. Kirshenbaum,
R. N. Zuckermann, K. A. Dill, Curr. Opin. Struct. Biol. 1999, 9, 530
535.
Self-Assembling Organic Nanotubes from
Enantiopure Cyclo-N,N'-Linked Oligoureas:
Design, Synthesis, and Crystal Structure
[2] For representative examples of helical b-peptides, see D. Seebach, M.
Overhand, F. N. M. K¸hnle, B. Martinoni, L. Oberer, U. Hommel, H.
Widmer, Helv. Chim. Acta 1996, 79, 913 941; D. Seebach, S. Abele, K.
Gademann, G. Guichard, T. Hintermann, B. Jaun, J. L. Matthews, J. V.
Schreiber, L. Oberer, U. Hommel, H. Widmer, Helv. Chim. Acta 1998,
81, 932 982; S. Abele, G. Guichard, D. Seebach, Helv. Chim. Acta
1998, 81, 2141 2156; D. Seebach, T. Sifferlen, P. A. Mathieu, A. M.
H‰ne, C. M. Krell, D. J. Bierbaum, S. Abele, Helv. Chim. Acta 2000,
83, 2849 2864; H. Appella, L. A. Christianson, I. L. Karle, D. R.
Powell, S. H. Gellman, J. Am. Chem. Soc. 1996, 118, 13071 13072;
D. H. Appella, L. A. Christianson, D. A. Klein, D. R. Powell, X.
Huang, J. J. Barchi, Jr, S. H. Gellman, Nature 1997, 387, 381 384;
D. H. Appella, J. J. Barchi, Jr, S. R. Durell, S. H. Gellman, J. Am.
Chem. Soc. 1999, 121, 2309 2310; X. Wang, J. F. Espinosa, S. H.
Gellman, J. Am. Chem. Soc. 2000, 122, 4821 4822.
[3] For representative examples of sheet and turn structures with b-
peptides, see a) D. Seebach, S. Abele, K. Gademann, B. Jaun, Angew.
Chem. 1999, 111, 1700 1703; Angew. Chem. Int. Ed. 1999, 38, 1595
1597; b) S. Krauth‰user, L. A. Christianson, D. R. Powell, S. H.
Gellman, J. Am. Chem. Soc. 1997, 119, 11719 11720; c) Y. J. Chung,
R. B. R. Huck, L. A. Christianson, H. E. Stanger, S. Krauth‰user,
D. R. Powell, S. H. Gellman, J. Am. Chem. Soc. 2000, 122, 3995 4004.
[4] For leading references on g-peptides, see a) T. Hintermann, K.
Gademann, B. Jaun, D. Seebach, Helv. Chim. Acta 1998, 81, 983
1002; b) D. Seebach, M. Brenner, M. Rueping, B. Schweizer, B. Jaun,
Chem. Commun. 2001, 207 208; c) S. Hanessian, X. Luo, R. Schaum,
S. Michnick, J. Am. Chem. Soc. 1998, 120, 8569 8570; d) S. Hanessian,
X. Luo, R. Schaum, Tetrahedron Lett. 1999, 40, 4925 4929.
Vincent Semetey, Claude Didierjean, Jean-Paul Briand,
¬
Andre Aubry, and Gilles Guichard*
Assembly of self-complementary cyclo-oligomeric subunits
through noncovalent processes (for example, hydrogen bond-
ing, aromatic stacking) has emerged as a powerful strategy to
generate artificial organic nanotubular structures.[1, 2] Highly
functionalized tubular assemblies based on peptides have
attracted much interest recently in this area. Ghadiri and co-
workers have compellingly demonstrated that 24- and 30-
membered-ring cyclo-a-peptides with an even number of
alternating d- and l-amino acids stack in an antiparallel b-
sheet-like arrangement to form hydrogen-bonded tubular
4]
structures, that is, ™peptide nanotubes∫.[2
Remarkably,
related cyclic peptides consisting exclusively of b-amino
acids[5, 6] (16- and 12-membered ring), of alternating a- and
b-amino acids[7] (14-membered ring), or of vinylogous d-
amino acids[8] (18-membered ring) also form tubular stacks.
We have shown previously[9] that linear N,N'-linked oli-
goureas A consisting of homochiral residues adopt a stable
2.5-helical secondary structure in solution. The helix is
characterized by the simultaneous presence of 12- and 14-
membered hydrogen-bonded rings resulting from the capacity
of the urea group to establish self-complementary bidirec-
[5] a) K. Burgess, D. S. Linthicum, H. Shin, Angew. Chem. 1995, 107, 975
977; Angew. Chem. Int. Ed. Engl. 1995, 34, 907 908; b) K. Burgess, J.
Ibarzo, D. S. Linthicum, D. H. Russell, H. Shin, A. Shitangkoon, R.
Totani, A. J. Zhang, J. Am. Chem. Soc. 1997, 119, 1556 1564.
[6] a) J. M. Kim, Y. Bi, S. Paikoff, P. G. Schultz, Tetrahedron Lett. 1996, 37,
5305 5308; b) A. Boeijen, R. M. J. Liskamp, Eur. J. Org. Chem. 1999,
2127 2135; c) G. Guichard, V. Semetey, C. Didierjean, A. Aubry, J. P.
Briand, M. Rodriguez, J. Org. Chem. 1999, 64, 8702 8705; d) G.
Guichard, V. Semetey, M. Rodriguez, J. P. Briand, Tetrahedron Lett.
2000, 41, 1553 1557.
[*] Dr. G. Guichard, V. Semetey, Dr. J.-P. Briand
¬
Immunologie et Chimie Therapeutiques, UPR CNRS 9021
¬
Institut de Biologie Moleculaire et Cellulaire
[7] Similarly, Seebach and co-workers have shown in the case of a b-
heptapeptide that J(NH,bCH) values decrease only slowly upon an
increase of the temperature from 298 to 353 K. A decrease of about
0.4 Hz was observed for the central residues (3 6) and about 0.7 Hz
for the flanking residues 2and 7: K. Gademann, B. Jaun, D. Seebach,
R. Perozzo, L. Scapozza, G. Folkers, Helv. Chim. Acta 1999, 82, 1 11.
15, rue Descartes, 67084 Strasbourg (France)
Fax : (‡33)3-88-61-06-80
E-mail: G.Guichard@ibmc.u-strasbg.fr
Dr. C. Didierjean, Dr. A. Aubry
LCM3B, UMR-CNRS 7036, Groupe Biocristallographie
¬
¬
3
[8] In the case of residue 3, J(aCH2,N'H) values were extracted directly
Universite Henri Poincare
BP 239, 54506 Vand˙uvre, France
from the 1D NMR spectrum, but decoupling experiments were
required to access precise 3J(bCH,aCH2)values. Severe overlaps in the
aCH region precluded measurement of the 3J(bCH,aCH2) values for
Supporting information for this article is available on the WWW under
http://www.angewandte.com or from the author.
Angew. Chem. Int. Ed. 2002, 41, No. 11
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1433-7851/02/4111-1895 $ 20.00+.50/0
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tion of the succinimidyl carbamate derivative 2[10] with the
monoprotected benzylated diamine 3 yielded the trisubsti-
tuted urea 4. Removal of the Boc group followed by urea
formation with 2 gave the bisurea 5. Repetition of this two-
step sequence gave the fully protected triurea 6 in an overall
yield of 45% from 3. Following quantitative removal of the
Alloc group, the resulting amine 7 was converted into the key
activated linear precursor 8 by treatment with di(N-succini-
midyl carbonate). At this stage, the temporary protection of
the urea with a benzyl group was mandatory. Initial attempts
to convert the linear oligotriurea precursor 11 under the same
conditions were not successful and led exclusively to the
formation of the cyclic biuret derivative 12.
O
H
N
H
N
Ri
H
N
H
H
N
N
N
N
N
H
O
O
O
H
n
H
A
N
H
N
H
O
1
tional intermolecular hydrogen bonds. We envisioned that the
corresponding macrocyclic derivatives might lead to flat ring
structures with a high degree of self-complementarity that
would allow self-assembling processes to occur. Herein we
report the design and the synthesis of the C4-symmetric (all-S)
cyclotetraurea 1 bearing side chains of alanine, and demon-
strate by single-crystal X-ray analysis that 1 forms square-
shaped nanotubes.
H
N
H
N
O
H
N
H
N
Boc
N
N
H
N
H
NH2
H
O
O
11
H
N
O
H
N
H
N
O
H
N
Boc
N
N
N
N
H
The general stepwise strategy used to synthesize the 20-
membered-ring macrocycle 1 is outlined in Scheme 1. Reac-
H
O
H
O
12
The Boc protecting group was selectively removed upon
treatment of crude 8 with CF3COOH to give the trifluoro-
acetate salt 9. Slow addition of a solution of 9 in MeCN to a
dilute solution of H¸nig×s base in MeCN resulted in the
formation of the expected monobenzylated cylic oligotetraur-
ea 10 in a yield of 62% from 7 after HPLC purification
(C18 column, reversed phase). Cyclotetraurea 1 was obtained
in 92% yield from 10 following deprotection of the urea
group by hydrogenation in EtOH. Single crystals of 1 suitable
for X-ray studies were grown by slow evaporation of the
EtOH solution.
O
H
N
H
Hünig's base
Boc
O
Bn
N
N
N
N
H
Alloc
H
O
O
2
3
O
1) HCl, dioxane
H
H
N
N
Boc
N
N
Alloc
2) 2, Hünig's base
H
Bn
4
O
1) HCl, dioxane
H
H
N
H
Boc
N
N
N
N
N
Alloc
2) 2, Hünig's base
X-ray crystallographic analysis[11] revealed that cyclourea 1
adopts a C4-symmetric conformation in the solid state and
stacks to form a hollow tubular structure (Figure 1). The four
H
H
O
Bn
5
O
O
H
N
H
N
H
N
R
N
Boc
N
H
N
N
H
H
O
Bn
[Pd(Ph3)4]
Et2NH
6
7
R = AllocNH
R = H3+N
CO(OSu)2,
Hünig's base
O
O
O
H
H
H
R'
N
N
N
O
N
N
N
N
N
H
H
H
O
Bn
O
O
8
9
R' = BocNH
R' = H3+N
CF3COOH
H
N
H
N
Bn
N
O
O
NH
H2, Pd/C
Hünig's base
O
O
1
HN
NH
N
N
H
H
10
Figure 1. Ball and stick representation of 1 showing the numbering
scheme. The torsion angles [8] of the main chain are : N1A-C1A-C2A-
N2A 57.9(2), C1A-C2A-N2A-C4A À156.7(2), C2A-N2A-C4A-N1B
177.4(2), N2A-C4A-N1B-C1B 172.6(2), C4A-N1B-C1B-C2B 78.0(3).
Scheme 1. Synthesis of 1. Alloc ˆ allyloxycarbonyl, Boc ˆ tert-butoxycar-
bonyl, Bn ˆ benzyl, H¸nig×s base ˆ diisopropylethylamine, Su ˆ succini-
midyl.
1896
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urea fragments in the macrocyle present an all-trans, planar
conformation with all the urea carbonyl groups pointing down
and all the NH groups pointing up (Figure 1). The macrocyle
exhibits a square shape with a cross-section of 6.052(7) ä
(distance between C1A and C1B).
A difference map analysis revealed the presence of two
peaks located on the fourfold symmetry axis. The distance
between the two peaks was 1.42ä. NMR experiments gave no
evidence for the presence of any organic solvent molecules in
the crystal, thus the two peaks were treated as disordered
water molecules W1 and W2. The internal van der Waals
diameter (approximately 3.5 ä) of the tubular structure is
actually large enough to accommodate such molecules. The
distance between the two water molecules is too short to have
both sites occupied at the same time. There is no short atomic
contact favoring hydrogen bonding between the water
molecules W1 and W2and the macrocyle.
c axis gives rise to an infinite nanotube. The crystal obtained
exhibits a body-centered Bravais lattice, and thus the X-ray
structure consists of an array of nanotubes in which each
tubular stack is surrounded by four close neighbors at a
p
distance of a 2/2 ä (a ˆ 15.333(3) ä is one of the unit cell
parameters). Neighboring tubes are all arranged in the same
direction.[13]
The nanotubes are held together in the crystal by loose
van der Waals contacts. The intermolecular distances between
equivalent C1A atoms and equivalent C3A atoms are 4.097(7)
and 4.218(10) ä, respectively.
In summary, we have reported a versatile approach to the
synthesis of 20-membered cyclic oligoureas bearing proteino-
genic side chains. The cyclic units consisting of homochiral
residues self-assemble in the crystal state to form hydrogen-
bonded polar nanotubes. The structure of the tubular stack
with all the carbonyl and NH groups pointing, respectively, in
the same direction is reminiscent of the nanotubes formed by
cyclotetra-b-peptides with homochiral residues.[5a] Particular-
ly noteworthy is the presence of electronic density inside the
tubular cavity which was modeled as disordered water
molecules at overlapping sites. Further work to explore other
tubular arrangements made from cycloureas with different
side-chain functionalities and different stereochemistry is on
going.
The square-shaped cycloureas stack along the crystallo-
graphic fourfold axis of the crystal through backbone back-
bone hydrogen-bonding interactions so that the two NH
hydrogen atoms of each urea fragment interact with a urea
oxygen atom of a neighboring macrocycle (Figure 2).
Received: December 18, 2001 [Z18407]
[1] B. Kˆnig, Angew. Chem. 1997, 109, 1919 1921; Angew. Chem. Int. Ed.
1997, 36, 1808 1832.
[2] D. T. Bong, T. D. Clark, J. R. Granja, M. R. Ghadiri, Angew. Chem.
2001, 113, 1016 1041; Angew. Chem. Int. Ed. 2001, 40, 988 1011, and
references therein.
[3] a) M. R. Ghadiri, J. R. Granja, R. A. Milligan, D. E. McRee, N.
Khazanovich, Nature 1993, 366, 324 327; b) J. R. Granja, R. M.
Ghahiri, J. Am. Chem. Soc. 1994, 116, 10785 10786; c) M. R.
Ghadiri, K. Kobayashi, J. R. Granja, R. K. Chadha, Angew. Chem.
1995, 107, 76 78; Angew. Chem. Int. Ed. 1995, 34, 93 95.
[4] Cyclo-a-peptides are stable to proteases and hold great promise as
antibacterial agents: S. Fernandez-Lopez, S. H. Kim, E. C. Choi, M.
Delgado, J. R. Granja, A. Khasanov, K. Kraehenbuehl, G. Long, D. A.
Weinberger, K. M. Wilcoxen, M. R. Ghadiri, Nature 2001, 412, 392
393.
[5] a) The structure and tubular stacking of three stereoisomers of
cyclo(b3-HAla)4 have been determined from powder diffraction data:
D. Seebach, J. L. Matthews, A. Meden, T. Wessels, C. Baerlocher, L. B.
McCusker, Helv. Chim. Acta 1997, 80, 173 182; b) the structure of the
12-membered-ring cyclo(b3-HGlu)3 with S,S,S configuration investi-
gated by NMR spectroscopy in D2O reveals a C3-symmetric arrange-
ment with all the carbonyl groups pointing upwards. Modeling
experiments suggest that cyclo-b-tripeptides can adopt stacked
tubular structures: K. Gademann, D. Seebach, Helv. Chim. Acta.
1999, 82, 957 962.
[6] T. D. Clarck, L. K. Buehler, M. R. Gadhiri, J. Am. Chem. Soc. 1998,
120, 651 656.
[7] I. Karle, B. K. Handa, C. H. Hassall, Acta Crystallogr. B 1975, B31,
555 560.
[8] D. Gauthier, P. Baillargeon, M. Drouin, Y. L. Dory, Angew. Chem.
2001, 113, 4765 4768; Angew. Chem. Int. Ed. 2001, 40, 4635 4638.
[9] V. Semetey, D. Rognan, C. Hemmerlin, R. Graff, J.-P. Briand, M.
Marraud, G. Guichard, Angew. Chem. 2002, 114, 1973 1975; Angew.
Chem. Int. Ed. 2002, 41, 1893 1895.
Figure 2. View of the nanotubular organization of 1 along the channel axis.
The intermolecular hydrogen bonds are marked as dashed lines. The
solvent molecules and H atoms, except those of the NH groups, are omitted
for clarity. The edges of the unit cells are represented in gray.
One of the intermolecular N ¥¥¥ O distances has standard
dimensions (2.798(2) ä), while the other (3.281(2) ä) is just
above the limit generally considered for hydrogen-bonding
interactions (Figure 2). This stacking of the macrocyles differs
from that observed in the crystal structure of cystine-based
macrocyclic bisureas that also exhibits a backbone backbone
urea-type hydrogen-bonding interaction.[12] As a consequence
of the absence of a local symmetry for the motif C1A C1B
À
ˆ
(Figure 1), the urea N H and C O bonds in 1 are not parallel
to the channel axis and generate two different N ¥¥¥ O contacts.
Each cyclourea is perpendicular to and centered on the
crystallographic quaternary axis in the crystal of 1. The
stacking of the cyclourea units along the crystallographic
[10] G. Guichard, V. Semetey, C. Didierjean, A. Aubry, J. P. Briand, M.
Rodriguez, J. Org. Chem. 1999, 64, 8702 8705.
Angew. Chem. Int. Ed. 2002, 41, No. 11
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1433-7851/02/4111-1897 $ 20.00+.50/0
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[11] Crystal data: C16H32N8O4, Mr ˆ 400.48 gmolÀ1, colorless prism, crystal
processes.[2, 7] Switching between pyrene monomer and ex-
cimer emission has also been used to obtain a sensor response,
whereby the ability of pyrene moieties to interact with one
another is influenced by the binding of analyte to the
receptor.[2, 8]
size 0.3  0.1  0.1 mm3, a ˆ b ˆ 15.333(3), c ˆ 4.724(1) ä, Vˆ
1110.6(4) ä3, Tˆ 293 K, tetragonal, space group I4, Z ˆ 2, 1calcd
ˆ
1.226 Mg mÀ3
,
m ˆ 0.763 mmÀ1
Nonius Mach3 diffractometer, l ˆ
.
1.54178 ä. 4293 measured reflections, 1052 unique (Rint ˆ 0.017), 953
with I > 2s(I), the structure was solved by direct methods and refined
by full-matrix least squares on F 2 for all data to R1 ˆ 0.0411 [I > 2s(I)]
and wR2 ˆ 0.1036 [I > 2s(I)], 93 parameters. CCDC 175843 contains
the supplementary crystallographic data for this paper. These data can
be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrie-
ving.html (or from the Cambridge Crystallographic Data Centre, 12,
Union Road, Cambridge CB21EZ, UK; fax: (‡44)1223-336-033; or
deposit@ccdc.cam.ac.uk).
We used a [RuCl2(POR-P,O)2] complex (where POR is an
ether-substituted phosphane) as the basis for a modular
molecular sensor. This type of complex reacts rapidly and
reversibly with numerous Lewis-basic small molecules, in-
11]
cluding CO,[9 a small-molecule analyte for which effective
new sensor materials may be useful, by displacement of the
labile ether moiety. Incorporation of a pyrene group in the
hemilabile ligand leads to metal-based reactivity towards
small molecules and pyrene-based luminescence. Here a RuII
complex containing the hemilabile phosphane ether ligand
4-{2-(diphenylphosphanyl)phenoxy}butylpyrene (POC4Pyr)
is described. The complex [RuCl2(POC4Pyr-P,O)2] (1, see
Scheme 1) reacts with carbon monoxide to produce a
significant luminescence response in which monomer-to-
excimer emission switching is observed. This is the first
example of the use of the hemilabile-ligand approach to
obtain a molecular sensor with a room-temperature lumines-
cence response, although we have previously reported a Ru
bipyridyl complex containing a hemilabile ligand that exhibits
small-molecule-dependent luminescence at low tempera-
ture.[12]
[12] Nonsymmetrical macrocyclic bisureas consisting of one cystine unit
and one hexamethylenediamine unit bridged together form tubelike
hydrogen-bonded aggregates in the solid state. In this case, the
carbonyl groups of the two urea units within the same ring point in
opposite directions: D. Ranganathan, C. Lakshmi, I. L. Karle, J. Am.
Chem. Soc. 1999, 121, 6103 6107.
[13] A different packing is observed in the structure of the b-peptide
cyclo(b3-HAla)4 with S,S,S,S configuration. Although all C O and
ˆ
À
N H bonds point, respectively, in the same direction in each tubular
stack, neighboring tubes are arranged in opposite directions. See
reference [5a].
Complex 1 was prepared by reaction of POC4Pyr with
RuCl3 ¥ xH2O in boiling deaerated ethanol/toluene. The
burgundy-pink complex is mildly sensitive to oxidation by
air, both in solution and as a solid. The 13C{1H} and 31P{1H}
NMR data of 1 (Tables 1 and 2) are analogous to those of
[RuCl2(POMe-P,O)2] (POMe ˆ (2-methoxyphenyl)diphenyl-
phosphane), which has been crystallographically character-
ized[9] and found to contain two P,O-coordinated phosphane
ether ligands with the phosphane moieties cis to each other.
The absorption spectrum of complex 1 is essentially a
combination of those of [RuCl2(POMe-P,O)2] and the pyrenyl
ligand POC4Pyr. The color of the complex is caused by a weak
Drastic Luminescence Response to Carbon
Monoxide from a RuII Complex Containing a
Hemilabile Phosphane Pyrene Ether**
Cerrie W. Rogers and Michael O. Wolf*
The rapid, reversible nature of the coordinative bonding
between metals and Lewis-basic small molecules makes
molecular chemosensors based on this phenomenon quite
promising. Indeed, recent reviews contain numerous reports
3]
of sensors based on metal ligand interactions.[1 Of partic-
ular potential are metal complexes designed such that the
analyte-binding event changes the luminescence properties of
an intramolecular lumophore. One approach is to use a
modular design in which a metal-based analyte receptor is
covalently linked to a separate lumophore. The emission of
the lumophore is influenced by the binding of the analyte,
usually through On Off switching of energy- or electron-
transfer quenching mechanisms.[1, 2, 4] Pyrene, which emits
intense indigo-blue fluorescence in dilute solution[5] and blue-
green excimer emission in concentrated solution,[5, 6] is a
popular lumophore for such molecule-based sensors, partic-
ularly those based on photoinduced electron transfer (PET)
Table 1. Summary of 13C{1H} NMR spectroscopic data[a] for 1 3.
Com-
plex
d/ppm (multiplicity) [J/Hz]
ortho[b]
ipso
CO
ipso'
1
2
3
161.7 (t) [5.2] 134.1 (d) [25.3] ND[c]
197.6 (t) [13.5] 160.5 (t) [2.3] 132.8 (t) [24.4] 118.8 (t) [23.9]
193.7 (t) [10.9] 159.0 (t) [2.3] 131.8 (t) [24] 119.3 (t) [23.5]
[a] In CD2Cl2. [b] Phenyl C atom bound to oxygen. [c] ND ˆ not deter-
mined.
Table 2. Comparison of 1 3 with analogous POMe complexes.[a]
[*] Prof. M. O. Wolf, C. W. Rogers
À1
ˆ
Complex
Color
d(31P{1H})/ppm nÄ(C O)/cm
Department of Chemistry, The University of British Columbia
2036 Main Mall, Vancouver, V6T1Z1 (Canada)
Fax : (‡1)604-822-2847
tcc-1
ttt-2
cct-3
red
63.7[b]
greenish yellow 27.1[b]
greenish yellow 13.9[b]
2005[c]
2005, 2058[c]
E-mail: mwolf@chem.ubc.ca
tcc-[RuCl2(POMe-P,O)2]
ttt-[RuCl2(CO)2(POMe-P)2] yellow
cct-[RuCl2(CO)2(POMe-P)2] white
red
62.7[d]
26.7
10.6
[**] This work was supported by the Natural Sciences and Engineering
Research Council (NSERC) of Canada. C.W.R. thanks NSERC and
UBC for graduate fellowships.
1962
2000, 2060
Supporting information for this article is available on the WWW under
http://www.angewandte.com or from the author.
[a] From ref. [9]; 31P{1H} NMR spectra measured in CDCl3 solution; IR spectra
measured in mineral-oil mulls. [b] In CD2Cl2. [c] In CHCl3. [d] In CDCl3.
1898
¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1433-7851/02/4111-1898 $ 20.00+.50/0
Angew. Chem. Int. Ed. 2002, 41, No. 11