(
DMSO, 300 MHz): δ = 8.92 (N3, 2H, d, J = 8.08 Hz), 8.86 (N6, 2H, d,
J = 4.78 Hz), 8.73 (N3Ј, 2H, s), 8.30 (N4, 2H, dt, J = 1.47, 7.72 Hz), 7.75
(
(
N5, 2H, dt, J = 1.10, 6.25 Hz), 6.84 (ph2, 2H, d, J = 2.20 Hz), 6.41
13
ph4, 1H, t, J = 1.83 Hz); C-NMR (DMSO, 400 MHz): δ = 147.4 (C6,
t), 140.1 (C4, t), 125.4 (C5, t), 122.2 (C3, t), 118.9 (C3Ј, t), 104.8 (ph2, t),
1
§
03.8 (ph4, t).
Full preparative details will be reported in a future manuscript.
2
ϩ
1
: ES MS m/z (calc.): 1279 (1279, [M Ϫ 2PF ] ), 804 (804.3,
6
3ϩ 4ϩ
[M Ϫ 3PF6] ), 567 (567, [M Ϫ 4PF6] ).
2
ϩ
2
: ES MS m/z (calc.): 1361 (1361, [M Ϫ 2PF ] ), 859 (859,
6
3
ϩ
4ϩ
[M Ϫ 3PF6] ), 608 (608, [M Ϫ 4PF6] ).
Ϫ5
¶
Absorption and luminescence spectra of dilute solutions (2 × 10
M—at this concentration, intermolecular energy transfer does not
take place) in air-equilibrated acetonitrile (room temperature) or
butyronitrile (77 K) were recorded with a Perkin-Elmer Lambda 5
spectrophotometer and with a Spex Fluorolog II spectrofluorimeter
(
(
λexc = 480 nm), respectively. Uncorrected luminescence band maxima
uncertainty was 2 nm) are used throughout the text. In order to
determine corrected band maxima and luminescence quantum effic-
iencies (uncertainty was 20%) we followed a procedure reported in ref.
7
b. Luminescence lifetimes (uncertainty was 8%) were obtained using
IBH single-photon counting equipment (N -based lamp, λ = 337 or
3
2
exc
58 nm) or with a picosecond fluorescence spectrometer based on a
Nd:YAG laser (Continuum PY62-10) operated at 532 nm, 10 Hz, 1 mJ
1
5
per pulse and a Hamamatsu C1587 streak camera.
1
2
V. Balzani, S. Campagna, G. Denti, A. Juris, S. Serroni and
M. Venturi, Acc. Chem. Res., 1998, 31, 26.
(a) E. C. Constable and C. E. Housecroft, Chimia, 1999, 53, 187;
(
b) E. C. Constable, O. Eich, C. E. Housecroft and D. C. Rees, Inorg.
Chim. Acta, 2000, 300, 158; (c) J. M. J. Frechet, Abstr. Pap. Am.
Chem. Soc., 2001, 222, 239; (d ) J. M. J. Frechet, Abstr. Pap. Am.
Chem. Soc., 2002, 223, 26; (e) T. Weil, E. Reuther and K. Mullen,
Angew. Chem., Int. Ed., 2002, 41, 1900.
3
(a) V. Balzani, P. Ceroni, A. Juris, M. Venturi, S. Campagna,
F. Puntoriero and S. Serroni, Coord. Chem. Rev., 2001, 219, 545;
Fig. 2 Time resolved properties observed for the trinuclear complexes
in butyronitrile at 77 K. Top: streak camera time profiles for the faster
portion of the decays of 1, τ was 1.8 ns (at 630 nm, decay of the Ru-
based luminescence) and 1.6 ns (at 750 nm, rise of the Os-based
luminescence). The laser profile (FWHM = 35 ps) is not shown.
Bottom: single-photon time profiles on a large time scale for the Os-
based spectral region of 2, rise (τ = 36 ns) and decay (τ = 1.96 µs)
(
b) S. Campagna, C. Di Pietro, F. Loiseau, B. Maubert,
N. McClenaghan, R. Passalacqua, F. Puntoriero, V. Ricevuto and
S. Serroni, Coord. Chem. Rev., 2002, 229, 67.
4
5
(a) N. Armaroli, C. Boudon, D. Felder, J. P. Gisselbrecht, M. Gross,
G. Marconi, J. F. Nicoud, J. F. Nierengarten and V. Vicinelli, Angew.
Chem., Int. Ed., 1999, 38, 3730; (b) A. K. Bilakhiya, B. Tyagi, P. Paul
and P. Natarajan, Inorg. Chem., 2002, 41, 3830.
1
2
components of a dual exponential decay are shown (see text; the same
value for τ was observed in the case of 1). The flash profile of the N
2
2
A. Börje, O. Köthe and A. Juris, J. Chem. Soc., Dalton Trans., 2002,
lamp (FWHM = 3 ns) is also shown.
8
43.
7
6 E. C. Constable, O. Eich, D. Fenske, C. E. Housecroft and
ations on thtpy and related complexes and correspond
unexpectedly well with simple molecular mechanics calcu-
lations on the compounds (MM2ϩ, metal coordination geom-
etry constrained to crystallographic values, otherwise let free)
which give average Os–Ru distances of 10.5 Å and average
metal–centroid of thienyl ring distances of 16.0 Å.
L. A. Johnston, Chem. Eur. J., 2000, 6, 4364.
7
(a) W. Spahni and G. Calzaferri, Helv. Chim. Acta, 1984, 67, 450;
(
b) S. Encinas, L. Flamigni, F. Barigelletti, E. C. Constable,
C. E. Housecroft, E. R. Schofield, E. Figgemeier, D. Fenske,
M. Neuburger, J. G. Vos and M. Zehnder, Chem. Eur. J., 2002, 8,
1
37.
8
(a) C. O. Dietrich-Buchecker, J.-P. Sauvage, J. P. Kintzinger,
P. Maltese, C. Pascard and J. Guilheim, New J. Chem., 1992, 16, 931;
In conclusion, the structurally similar trinuclear complexes 1
and 2 exhibit different Ru
Os intramolecular energy transfer
(
1
b) C. O. Dietrich-Buchecker and J.-P. Sauvage, New J. Chem., 1990,
4, 603; (c) E. C. Constable, D. J. Morris and S. Carr, New J. Chem,
1998, 22, 287.
rate constants; this rate is 20-fold lower in 2 than 1. We have
shown that intramolecular energy transfer rates in polynuclear
metallostars may be fine-tuned by the interplay of structural
and electronic effects of substituents at the periphery.
A. F. M. thanks TMR Research Network Programme
ERBFMRX-CT98–0226 ‘Nanometer Size Metal Complexes’
for support. E. C. C. and C. E. H. thank the University of
Basel, the University of Birmingham and the Schweizerischer
Nationalfonds zur Förderung der wissenschaftlichen Fors-
chung for support.
9 N. Armaroli, F. Barigelletti, E. C. Constable, S. Encinas,
E. Figgemeier, L. Flamigni, C. E. Housecroft, E. R. Schofield and
J. G. Vos, Chem. Commun., 1999, 869.
1
0 E. C. Constable, A. M. W. Cargill Thompson, P. Harverson,
L. Macko and M. Zehnder, Chem. Eur. J., 1995, 1, 360.
1 J. P. Sauvage, J. P. Collin, J. C. Chambron, S. Guillerez, C. Coudret,
V. Balzani, F. Barigelletti, L. De Cola and L. Flamigni, Chem. Rev.,
1994, 94, 993.
2 L. Hammarström, F. Barigelletti, L. Flamigni, N. Armaroli,
A. Sour, J. P. Collin and J. P. Sauvage, J. Am. Chem. Soc., 1996, 118,
1
1
1
1972.
1
1
3 T. Förster, Discuss. Faraday Soc., 1959, 27, 7.
4 N. R. M. Simpson, M. D. Ward, A. F. Morales, B. Ventura and F.
Barigelletti, J. Chem. Soc., Dalton Trans., 2002, 2455.
Notes and references
ϩ
ϩ
ϩ ϩ
‡
ES MS m/z (calc.): 364 (364, [M ϩ Na ] ), 342 (342, [M ϩ H ] ); HR
ϩ
1
MS: (calc.) C H N O [M ϩ H ] 342.124, found: 342.123; H-NMR
15 L. Flamigni, J. Phys. Chem., 1993, 97, 9566.
21
16
3
2
1
222
D a l t o n T r a n s . , 2 0 0 3 , 1 2 2 0 – 1 2 2 2