P. Servin et al. / Inorganica Chimica Acta xxx (2017) xxx–xxx
3
JHP = 8 Hz, 12H, C7Ha), 3.85 (dd, JHH = 14 Hz, JHP = 12 Hz, 12H, C7Hb),
4.22 (br s, 24H, C5H2, C6H2), 4.36 (d, JHH = 13.5 Hz, 6H, C9Ha), 4.51
(d, JHH = 13.5 Hz, 6H, C9Hb), 4.82 (d, JHH = 10.6 Hz, 12H, C8Ha),
5.04 (d, JHH = 10.6 Hz, 12H, C8Hb), 7.01 (d, JHH = 7.5 Hz, 12H, C2H),
7.49 (d, JHH = 7.5 Hz, 12H, C3H). 31P{1H} NMR (101.25 MHz,
DMSO-d6) d (ppm): -83.7 (s, PPTA), 8.3 (s, Pcore). 13C{1H} NMR
(62.9 MHz, DMSO-d6) d (ppm): 45.78 (d, JHP = 20.5 Hz, C7H2),
52.26 (d, JHP = 20.5 Hz, C6H2), 64.09 (s, C5H2), 69.69 (s, C9H2),
79.20 (s, C8H2), 121.49 (s, C2H), 123.54 (s, C4), 135.12 (s, C3H),
151.39 (s, C1).
solved in phosphate buffer. G3-Ru48 was insoluble and was
discarded at this step. G1-Ru12 and G2-Ru24 have a low solubility
in these conditions, but they were used, as well as M-Ru and G0-
Ru6 (which are fairly soluble) for interaction with supercoiled
DNA. One microgram of the pBluescript KSII plasmid (3Kbp; Strata-
geneTM) was added to 20
lL of 10 mM phosphate buffer solution at
pH 7.0 and diluted with the appropriate amount of a freshly pre-
pared solution of the ruthenium complexes in the same phosphate
buffer to achieve the desired stoichiometry between the nucle-
obase and the ruthenium complex. The reaction mixtures were
then incubated for 14 h at 37 °C in the dark, and 10 lL sample-ali-
2.5. Synthesis and characterization of G0-Ru6
quots were withdrawn and analyzed by electrophoresis in 1% agar-
ose-TAE gels. DNA bands were visualized by staining with
ethidium bromide and photographed under UV light. The Ri value
(metal to base molar ratio at the onset of the incubation) at which
complete transformation of the supercoiled to relaxed form of the
plasmid was registered for each active compound.
The result of the interactions was determined by DNA mobility
shift assays, and compared with the results of cisplatin (cis-[PtCl2(-
NH3)2]). Analogous experiments were carried out by dissolving
first the complexes in a small quantity of DMSO, then adding these
solutions to phosphate buffer. All the compounds were soluble in
these conditions, but the results of the interaction with supercoiled
DNA were analogous than in the previous cases.
A solution of dichloro(p-cymene)ruthenium dimer ([RuCl2(p-
cymene)]2, 304 mg, 0.496 mmol) in a solvent mixture of THF:
MeOH 1:4 (5 mL, degassed) (some drops of CH2Cl2 and heating)
was added to a solution of dendrimer G0 (334 mg, 0.174 mmol)
in a solvent mixture of THF:MeOH (degassed) 1:4 (20 mL) and
the mixture was left stirring 2 h at room temperature. The solvents
were removed in vacuum and the residue was washed several
times with THF and CH2Cl2 to afford G0-Ru6 (448 mg, 0.111 mmol,
64% yield) as an orange powder. 1H NMR (300 MHz, DMSO-d6) d
(ppm): 1.09 (d, JHH = 6.6 Hz, 36H, C16H3), 1.9 (s, 18H, C10H3), 2.70
(m, 6H, C15H), 4.0–4.2 (m, 12H, C5H2), 4.2–4.8 (br m, 48H, C6H2,
C7H2, C9H2), 5.06 (br s, 12H, C8Ha), 5.36 (br s, 12H, C8Hb), 5.9 (m,
24H, C12H, C13H), 6.96 (br d, JHH = 7.8 Hz, 12H, C2H), 7.44 (br s,
12H, C3H). 31P{1H} NMR (121. 5 MHz, DMSO-d6) d (ppm): -18.1
(s, PPTA), 8.6 (s, Pcore). 13C{1H} NMR (75.5 MHz, DMSO-d6) d
(ppm): 18.34 (s, C10H3), 22.12 (s, C16H3), 30.50 (s, C15H), 45.57
(br d, JHP = 20.0 Hz, C7H2), 52.14 (m, C6H2), 63.21 (br s, C5H2),
69.13 (br s, C9H2), 79.10 (br s, C8H2), 86.20 (br s, C12H), 89.30 (br
s, C13H), 97.41 (s, C11), 106.23 (s, C14), 121.63 (s, C2H), 123.60 (s,
C4), 135.20 (s, C3H), 151.30 (s, C1).
3. Results and discussion
3.1. Catalysis
As a test reaction, we have chosen the catalytic hydration of
alkynes. This reaction is frequently encountered in the literature,
and different types of catalysts have been used, in particular mer-
cury, but also less toxic metals such as gold, platinum and palla-
dium, and mainly ruthenium [29]. We have previously reported
the use of the preformed Ru complexes shown in Fig. 1 for catalyz-
ing the hydration of phenyl acetylene, and the isomerization of 1-
octan-3-ol to 3-octanone. The latter experiment displayed a nice
positive dendritic effect, i.e. an increase of the efficiency of the
catalysis when the generation (size) of the dendrimer increased.
This effect was not due to a larger number of catalytic entities, as
the number of Ru-PTA entities was kept constant, by comparing
the efficiency of 1 equiv. of G3-Ru48 to that of 2 equiv. of G2-
Ru24, or 4 equiv. of G1-Ru12, or 48 equiv. of M-Ru. However, the
hydration of phenyl acetylene was more difficult, necessitated a
prolonged heating (48 h at 90 °C), and a negative dendritic effect
in the percentage of conversion was observed on going from G1-
Ru12 to G3-Ru48, albeit a slight improvement in the selectivity
was observed [27]. Thus we decided to modify the conditions of
the catalyzed hydration of acetylene, to try to get better results
(Scheme 1).
2.6. Catalytic tests
All catalytic reactions were performed in Schlenk tubes, with
strong magnetic stirring, and warm oil bath. The percentage of con-
version and the selectivity were measured by relative integration
of 1H NMR signals. Experiments have been done in duplicate, and
the values given are the mean values (generally 2).
Catalyzes with the Ru complexes M-Ru, G1-Ru12, G2-Ru24, and G3-
Ru48: in the Schlenk tube were mixed 1 mL of water, 3 mL of iso-
propanol, 0.11 mL (1.0 mmol) of phenylacetylene, 5.0 10À2 mmol
of preformed Ru complex (31.0 mg of M-Ru, 36.0 mg of G1-Ru12
,
38.5 mg of G2-Ru24, and 39.6 mg of G3-Ru48). These mixtures
afforded a single phase in all cases. They were stirred for 24 or
48 h at 90 °C.
Catalyzes with the complexes formed in situ: in the Schlenk tube
were mixed 1 mL of water, 3 mL of isopropanol, compounds M,
G1, G2, or G3, and [RuCl2(p-cymene)]2, using 1.1 equiv. of PTA for
1 equiv. of Ru. The mixture was left to react for 15 min at room
temperature, then phenylacetylene (100 equiv.), and H2SO4 (co-
catalyst, 10 equiv.) were added, then the heating was started.
Recycling experiment: the first run was carried out in the condi-
tions used for the complexes formed in situ (with M and G1), fol-
lowed by heating for 17 h at 90 °C. At the end of the first run, an
extraction was made with diethylether. A new portion of iso-
propanol and of phenylacetylene was added, and the catalysis
was again carried out at 90 °C for 17 h (second run).
It is known that metal-catalyzed hydration of alkynes provides
an important route to carbonyl compounds [30], with complete
atom economy. In general, addition of water to terminal alkynes
follows Markovnikov’s rule, leading mainly to ketones. In the case
of ruthenium derivatives used as catalysts for such reactions, the
ketones are generally obtained, but the anti-Markovnikov product
(the aldehyde) was obtained using a Ru catalyst in the presence of
2.7. Interactions with DNA
The complexes M-Ru, G0-Ru6, G1-Ru12, G2-Ru24, and G3-Ru48
were first evaporated under vacuum for a long time (48 h) to elim-
inate traces of organic solvents, then they were tentatively dis-
Scheme 1. Catalyzed hydration of phenylacetylene. The type of Ru catalysts, their
quantities, the temperature, the time, and the selectivity (value of
the next Figures.
e) will be given in