Inorganic Chemistry
Article
through the reaction mixture for 1 h, causing a precipitate to form.
The precipitate was filtered and then washed with a minimum amount
of DMSO and, finally, with excess acetone. The final product was
a modest enhancement in the equilibrium constant (K*eq) of
Ru-deeb, while an order of magnitude decrease in K*eq was
observed for the amide complexes. The decrease in K*eq
resulted in the photorelease of associated halide ions. The
excited-state rate constants for halide dissociation (k21) were
largest for the complexes with the fewest hydrogen-bond
donors (Ru-da), while the presence of functional groups that
stabilized halides contributed to an energy barrier that
decreased the rate of photorelease. The results show that
excited-state supramolecular assembly can be controlled
through molecular design.
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obtained as a white powder (4.3 g, 42%). H NMR (d6-DMSO, 600
MHz): 8.86 (2H, dd), 8.80 (2H, dd), 8.42 (2H, s), 7.87 (2H, dd),
7.79 (2H, s). 13C NMR (d6-DMSO, 150 MHz): 166.30, 155.62,
150.04, 142.80, 122.00, 118.53.
Synthesis of deeb. 4,4′-Dicarboxy-2,2′-bipyridine (5g, 20.5 mmol)
and H2SO4 (5 mL) were refluxed in ethanol (100 mL) for 5 d. The
reaction mixture was added to CHCl3 (200 mL), and H2O (150 mL)
was added. The aqueous layer was extracted with CHCl3. The organic
fraction was dried with MgSO4, and the solvent was removed under
vacuum, yielding 5.28 g (85%) of deeb. 1H NMR (CDCl3, 500 MHz):
8.93 (2H, s), 8.85 (2H, d), 7.90 (2H, dd), 4.45 (4H, q), 1.43 (6H, t).
Synthesis of Ruthenium Complexes. General method for synthesis
of ruthenium complexes Ru-deaOH, Ru-dpaOH, Ru-dpa, Ru-
daeaOH, and Ru-deeb. To a 10 mL glass microwave vial was
added Ru(dtb)2Cl2·2H2O, 1 equiv of the appropriate ligand, and ∼5
mL of EtOH or a 1:1 mixture of H2O/EtOH. The mixture was heated
under microwave radiation by an Anton Paar Monowave 300 at 150
°C for 10 min. The red solution was filtered, and the solvent was
removed by rotary evaporation. The resulting solid was dissolved in
minimal H2O, and a few drops of saturated aqueous NH4PF6 were
added, causing a precipitate to form. The solid was collected with
vacuum filtration, washed with excess H2O, and dried under vacuum
at 100 °C overnight, yielding a red solid.
[Ru(dtb)2(deaOH)](PF6)2, (Ru-deaOH). Ru(dtb)2Cl2 (75 mg, 0.096
mmol), deaOH (32 mg, 0.097 mmol) and ∼5 mL of H2O/EtOH
(1:1) were heated at 150 °C for 10 min under microwave irradiation,
yielding 86 mg (71%) of Ru-deaOH. 1H NMR (CD2Cl2, 400 MHz):
8.95 (2H, s), 8.27 (4H, d), 7.83 (2H, dd), 7.77 (2H, d), 7.60 (2H, t),
7.57 (4H, q), 7.45 (4H, td), 3.78 (4H, m), 3.58 (4H, m), 2.86 (2H,
s), 1.42 (18H, s), 1.40 (18H, s).
[Ru(dtb)2(dpaOH)](PF6)2, (Ru-dpaOH). Ru(dtb)2Cl2 (75 mg, 0.096
mmol), dpaOH (34 mg, 0.095 mmol), and ∼5 mL of H2O/EtOH
were heated at 150 °C for 10 min under microwave irradiation,
yielding 110 mg (89%) of Ru-dpaOH. 1H NMR (CD2Cl2, 400
MHz): 8.84 (2H, d), 8.27 (4H, dd), 7.81 (2H, dd), 7.77 (2H, d), 7.72
(2H, t), 7.57 (2H, d), 7.53 (2H, d), 7.46 (2H, dd), 7.43 (2H, dd),
3.70 (4H, t), 3.61 (4H, q), 1.82 (4H, p), 1.43 (18 H, s) 1.41 (18 H).
High-resolution mass spectrometry (HRMS) electrospray ionization
mass spectrometry (ESI-MS). Calcd for C54H70F12N8O4P2Ru1Na1
([M + Na]+): m/z 1309.37. Found: m/z 1309.37.
EXPERIMENTAL SECTION
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Materials. Sulfuric acid (H2SO4, Fisher, 98%, certified ACS Plus),
methanol (Fisher, certified ACS), chloroform (Fisher, certified ACS),
ethanolamine (Sigma-Aldrich, ≥98%), acetone (Sigma-Aldrich,
certified ACS), acetonitrile (CH3CN, Burdick and Jackson,
99.98%), and dichloromethane (CH2Cl2, Burdick and Jackson,
99.98%) were used as received. Argon gas (Airgas, 99.998%) was
passed through a Drierite drying tube before use. Ammonium
hexafluorophosphate (NH4PF6, Sigma-Aldrich, ≥98%), tetrabutylam-
monium chloride (TBACl, Sigma-Aldrich, purum ≥97%), tetrabuty-
lammonium bromide (TBABr, Acros Organics, 99+%), tetrabuty-
lammonium perchlorate (TBAClO4, Sigma-Aldrich, for electro-
chemical analysis, ≥99%), and ruthenium trichloride hydrate
(Oakwood Chemicals, 97%) were used as received. NMR solvents
were purchased from Cambridge Isotope Laboratories, Inc. Ru-
(dtb)2Cl2·2H2O,70 4,4′-dicarboxy-2,2′-bipyridine,71 4,4′-dimethyles-
ter-2,2′-bipyridine,15 4,4′-diethylester-2,2′-bipyridine (deeb),72 [Ru-
(dtb)2(dea)](PF6)2, (Ru-deaOH),15 and [Ru(dtb)2(daea)](PF6)2
(Ru-daeaOH)17 were synthesized according to previous procedures.
All solutions were sparged with argon for at least 30 min before all
titration and transient PL experiments.
Synthesis of Ligands. General method for synthesis of amide-
functionalized ligands. To 4,4′-dimethylester- or 4,4′-diethylester-
2,2′-bipyridine in methanol was added an excess of the appropriate
amine. The mixture was refluxed for 4 h. When cooled, acetone was
added to the mixture, and the solid was collected by vacuum filtration
on a sintered glass frit. The precipitate was washed with excess
acetone and dried under vacuum at 100 °C, yielding a white powder.
deaOH. Refluxing 4,4′-diethylester-2,2′-bipyridine (2.0 g, 6.7
mmol) and ethanolamine (10 mL, 166 mmol) in methanol (40
mL) yielded 1.7 g (77%) of deaOH. 1H NMR ( d6-DMSO, 500
MHz): 8.91 (2H, t), 8.85 (2H, d), 8.78 (2H, s), 7.85 (2H, dd), 4.83
(2H, t), 3.55 (4H, m), 3.38 (4H, m).
[Ru(dtb)2(dpa)](PF6)2, (Ru-dpa). Ru(dtb)2Cl2 (75 mg, 0.096
mmol), dpa (31 mg, 0.095 mmol), and ∼5 mL of H2O/EtOH were
heated at 150 °C for 10 min under microwave irradiation, yielding 80
1
mg (66%) of Ru-dpa. H NMR (CD3CN, 500 MHz): 8.91 (2H, d),
8.48 (4H, dd), 7.84 (2H, d), 7.70 (2H, dd), 7.54 (4H, dd), 7.51 (2H,
t), 7.42 (2H, dd), 7.35 (2H, dd), 3.37 (m, 4H), 1.63 (4H, h), 1.41
(18h, s), 1.39 (18h, s), 0.96 (6H, t). HRMS (ESI-MS). Calcd for
C54H70F6N8O2P1Ru1 ([M]2+): m/z 482.24. Found: m/z 482.23.
[Ru(dtb)2(daeaOH)](PF6)2, (Ru-daeaOH). Ru(dtb)2Cl2 (75 mg,
0.096 mmol), daeaOH (40 mg, 0.096 mmol), and ∼5 mL of H2O/
EtOH (1:1) were heated at 150 °C for 10 min under microwave
irradiation, yielding 96 mg (74%) of Ru-daeaOH. 1H NMR (CD3CN,
500 MHz): 9.02 (s, 2H), 8.48 (dd, 4H), 7.84 (d, 2H), 7.73 (d, 2H),
7.55 (d, 4H), 7.42 (dd, 2H), 7.35 (dd, 2H), 3.56 (t, 4H), 3.51 (m,
4H), 2.85 (t, 4H), 2.73 (t, 4H), 1.41 (s, 18H), 1.39 (s, 18H).
[Ru(dtb)2(deeb)](PF6)2, (Ru-deeb). Ru(dtb)2Cl2 (100 mg, 0.141
mmol), deeb (42 mg, 0.140 mmol), and ∼5 mL of EtOH were heated
at 150 °C for 10 min under microwave irradiation, yielding 144 mg
(83%) of Ru-deeb. 1H NMR (CD3CN, 500 MHz): 9.02 (2H, d), 8.48
(4H, dd), 7.90 (2H, d), 7.83 (2H, dd), 7.52 (4H, dd), 7.42 (2H, dd),
7.34 (2H, dd), 4.45 (4H, q), 1.41 (24 H, m), 1.39 (18H, s). HRMS
(ESI-MS). Calcd for C52H64N6O4Ru1 ([M]2+): m/z 469.2. Found:
m/z 469.2.
dpaOH. Refluxing 4,4′-dimethylester-2,2′-bipyridine (1.0 g, 3.7
mmol) and 3-amino-1-propanol (5 mL, 83 mmol) in methanol (20
mL) yielded 1.1 g (92%) of dpaOH. 1H NMR (d6-DMSO, 600
MHz): 8.95 (2H, t), 8.87 (2H, d), 8.78 (2H, s), 7.85 (2H, dd), 4.52
(2H, t), 3.48 (4H, m), 3.36 (4H, m), 1.71 (4H, p). 13C NMR (d6-
DMSO, 150 MHz): 164.57, 155.52, 150.07, 143.03, 121.95, 118.22,
58.56, 36.81, 32.24.
dpa. Refluxing diethylester-2,2′-bipyridine (0.5 g, 1.6 mmol) and
propylamine (3 mL) in methanol (10 mL) yielded 0.292 g (54%) of
1
dpa. H NMR (d6-DMSO, 500 MHz): 8.96 (2H, t), 8.87 (2H, d),
8.79 (2H, s), 7.85 (2H, dd), 3.26 (4H, m), 1.57 (4H, m), 0.91 (6H,
t). 13C NMR (d6-DMSO, 150 MHz): 164.53, 155.53, 150.07, 143.09,
121.97, 118.22, 41.18, 22.26, 11.53.
daeaOH. Refluxing dimethylester-2,2′-bipyridine (1.0 g, 3.7 mmol)
and 2-[(2-aminoethyl)amino]ethanolamine (5 mL, 49 mmol) in
1
methanol (20 mL) yielded 1.1 g (72%) of daeaOH. H NMR (d6-
DMSO, 500 MHz): 8.93 (2H, t), 8.86 (2H, d), 8.79 (2H, d), 7.85
(2H, dd), 4.48 (2H, t), 3.44 (4H, q), 3.38 (4H, q), 2.72 (4H, t), 2.60
(4H, t).
Synthesis of da. 4,4′-Dicarboxy-2,2′-bipyridine (10g, 41.0 mmol)
was refluxed under argon overnight in thionyl chloride (100 mL). The
solvent was then removed from the mixture under reduced pressure,
and the residue was dissolved in toluene. NH3(g) was bubbled
[Ru(dtb)2(da)](PF6)2, (Ru-da). [Ru(dtb)2Cl2] (500 mg, 0.071
mmol) and da (188 mg, 0.078 mmol) were dissolved in 12 mL of
a 1:1 H2O/EtOH mixture and refluxed overnight under argon. After
reaction, the mixture was brought to room temperature and
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Inorg. Chem. XXXX, XXX, XXX−XXX