Inorganic Chemistry
Article
95 °C for 16 h under nitrogen atmosphere. After it cooled to room
temperature and was diluted with dichloromethane, it was washed with
water and brine. The organic phase was collected, dried over sodium
sulfate, filtered, and concentrated under reduced pressure by rotary
evaporator. The crude product thus obtained was purified by silica gel
column chromatography by eluting with chloroform−ethyl acetate
(9:1 v/v with 1% methanol) to yield the desired greenish-orange
product. Yield = 390 mg (0.96 mmol, 48%). Anal. Calcd for
C23H23BF2N4 (Mw: 404.19): C, 68.33; H, 5.73; N, 13.86. Found: C,
68.10; H, 5.87; N, 13.56%. Electrospray ionization mass spectrometry
cis-[Pt(NH3)2(L2)Cl](NO3) (2). Red solid. Yield: 76%. Anal. Calcd
for C23H27BClF2I2N7O3Pt (Mw: 981.96): C, 28.11; H, 2.77; N, 9.98.
Found: C, 28.10; H, 2.74; N, 9.99%. ESI-MS (m/z): Calcd [M-NO3]+,
1
919.98; Found, 919.98. H NMR (400 MHz, DMSO-d6): δ 7.80 (s, 1
H), 7.46−7.40 (m, 4 H), 7.11 (s, 2 H), 5.55 (s, 2 H), 4.14 (s, 3 H),
3.95 (s, 3 H), 2.40 (s, 6 H), 1.33 (s, 6 H). 13C NMR (100 MHz,
DMSO-d6): δ 163.76, 157.42, 145.77, 142.27, 139.96, 138.23, 135.03,
134.65, 131.66, 129.31, 129.14, 128.76, 120.74, 87.93, 50.28, 36.81,
32.45, 30.43, 17.61, 16.66. IR data (cm−1): 3300 (br), 3190 (br), 1610
(br), 1525 (sh), 1340 (s), 1300 (w), 1170 (sh), 1000 (sh). UV−visible
(1% DMSO/DMEM at pH 7.2): λmax, nm (ε, M−1 cm−1) = 540
(14 300), 510 (19 000).
1
(ESI-MS) (m/z) in MeOH: 405.20 [M + H]+. H NMR (400 MHz,
deuterated dimethyl sulfoxide (DMSO-d6)): 7.76 (s, 1 H), 7.42−7.35
(m, 4 H), 7.18 (s, 1 H), 6.94 (s, 1 H), 6.16 (s, 2 H), 5.31 (s, 2 H), 2.44
(s, 6 H), 1.31 (s, 6 H) (s, singlet; m, multiplet). 13C NMR (100 MHz,
DMSO-d6): 155.40, 143.14, 142.02, 139.18, 137.88, 133.88, 131.13,
128.90, 128.76, 121.69, 120.09, 49.69, 29.42 14.66, 14.45 ppm. IR data
(cm−1): 2920 (sh), 2850 (s), 1536 (sh), 1505 (sh), 1300 (sh), 1190
(w), 1150 (s), 960 (sh), 810 (s), 720 (sh) (w, weak; s, strong; sh,
shoulder). UV−visible (1% DMSO/Dulbecco’s Modified Eagle’s
Medium (DMEM) at pH 7.2) [λmax, nm (ε, M−1 cm−1)]: 500
(33 100). Emission data (1% DMSO/DMEM at pH 7.2): λem (λex, Φf)
= 505 nm (490 nm, 0.17).
X-ray Crystallographic Procedure. The crystal structures of
complex 3 and ligand L1 were obtained by single-crystal X-ray
diffraction method. The colorless rectangular block crystals of complex
3 were obtained from aqueous methanol on slow evaporation, while L1
as red rectangular blocks were crystallized from dimethyl sulfoxide
solution on slow evaporation. Both the crystals were mounted on
loops with mineral oil. All intensity and geometric data were collected
by an automated Bruker SMART APEX CCD diffractometer equipped
with a fine focus 1.75 kW sealed-tube Mo Kα X-ray source (λ =
0.710 73 Å) with increasing ω (width of 0.3° per frame) at a scan
speed of 5 s frame−1. Intensity data were collected using the ω-2θ scan
mode and then corrected for Lorentz-polarization and absorption
effects.44 The structures were solved and refined using the WinGx suite
of programs (version 1.63.04a) by the SHELXL-2013 method.45 The
non-hydrogen atoms were refined with anisotropic displacement
coefficients, and their coordinates were permitted to ride on their
respective carbon atoms. Atomic positions for all the atoms,
anisotropic thermal parameters for all the non-hydrogen atoms, and
isotropic thermal parameters for all the hydrogen atoms were included
in the final refinement. The perspective views were obtained using
ORTEP.46 Selected crystallographic parameters, bond distances, and
angles data are given in Table 2 and Table S1 (see Supporting
Cellular and DNA Binding Experiments. The cytotoxicity
studies of the platinum complexes 1 and 2 and their ligands L1 and L2
were made by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide (MTT) assay using HaCaT (human keratinocyte) and
MCF-7 (human breast cancer) cells. Cells were incubated with various
concentrations of the complexes from 0.14 to 10 μM in 1% DMSO/
DMEM for 4 h in the dark. One set of the cells was exposed to visible
light for 1 h (λ = 400−700 nm, light dose = 10 J cm−2), while the
other set was kept in the dark for 1 h using standard protocols.47 The
samples were kept for another 19 h incubation in dark thus making the
total incubation period for the MTT assay as 24 h. Data were obtained
from three independent sets of experiments done in triplicate for each
concentration. The intracellular localization of complex 1 was
investigated by confocal microscopy. HaCaT cells were incubated
with the complex (10 mm in 1% DMSO/DMEM) in the dark for 4 h.
Cells were stained with 4′,6-diamidino-2-phenylindole (DAPI; 1 mg
mL−1) for 5 min. Live cells were stained with MTR (100 nM) and
ERTR (100 nM). Images were captured in a Leica microscope (TCS,
SP5) with an oil immersion lens and magnification of 63×. Multiple
images were recorded, and experiments were done in duplicate. The
photoinduced generation of reactive oxygen species (ROS) by the
complexes in 1% DMSO/DMEM in HaCaT was quantified by using
the 2,7-dichlorofluorescein diacetate (DCFDA) assay. Cells were
incubated with 1 (5 μM) and 2 (2.5 μM) for 4 h in dark. One of the
plates was irradiated (λ = 400−700 nm, light dose = 10 J cm−2) for 1 h
in PBS buffer, whereas the other was kept in the dark. Annexin-V/
FITC/PI assay was done for 1 (5 μM) and 2 (2.5 μM) in 1% DMSO/
DMEM. Approximately 3 × 105 HaCaT cells were seeded in six-well
plates and cultured for 24 h. The cells were incubated with the
complex for 4 h in the dark and then exposed to light (1 h, λ = 400−
700 nm, light dose = 10 J cm−2) in phenol red free media or kept in
dark. Cells were then kept for another 14 h in DMEM/10% fetal
bovine serum (FBS) buffer in the dark, after which the medium was
discarded, and the cells were trypsinized and resuspended in the
Ligand L2. Ligand L1 (202 mg, 0.5 mmol) was dissolved in dry
dichloromethane (30 mL), excess of N-iodo succinimide (675 mg, 3
mmol, 6 equiv) was added, and the mixture was stirred for 14 h under
nitrogen atmosphere. The red solution was diluted with dichloro-
methane and washed with water. The organic phase was dried over
sodium sulfate, filtered, and concentrated under reduced pressure by
rotary evaporator. The crude product was purified by silica gel column
chromatography using chloroform/ethyl acetate (9:1 v/v with 1%
methanol) as eluent to isolate the product as pink-red solid. Yield =
210 mg (0.32 mmol, 64%). Anal. Calcd for C23H21BF2I2N4 (Mw:
655.99): C, 42.11; H, 3.23; N, 8.54. Found: C, 42.07; H, 3.21; N,
1
8.43%. ESI-MS m/z in MeOH: 656.98 [M + H]+. H NMR (DMSO-
d6, 400 MHz): 8. 44 (s, 1 H), 7.95 (s, 2 H), 7.45−7.39 (m, 4 H), 7.24
(s, 1 H), 7.01 (s, 1 H), 5.35 (s, 2 H), 2.56 (s, 6 H), 1.31 (s, 6 H). 13C
NMR (100 MHz, DMSO-d6): 163.22, 157.03, 145.77, 142.27, 139.23,
138.22, 135.19, 134.70, 131.70, 129.50 129.14, 128.76, 120.74, 87.87,
50.28, 36.69, 31.68, 30.43, 17.51, 16.66 ppm. IR data (cm−1): 2920
(sh), 2855 (s), 1695 (sh), 1525 (sh), 1340 (s), 1175 (s), 990 (s), 800
(br) (br, broad). UV−visible (1% DMSO/DMEM at pH 7.2) [λmax
,
nm (ε, M−1 cm−1)]: 540 (15 700), 515 (13 500).
cis-[Pt(NH3)2(L)Cl](NO3) (1, 2). The monofunctional platinum(II)
complexes were prepared by modifying the literature procedure.14,40
To a solution of cisplatin (0.15 g, 5 mmol) in 5 mL of N,N-
dimethylformamide (DMF) was added AgNO3 (0.89 g, 1 equiv), and
the reaction mixture was stirred under protection from light at room
temperature for 24 h. AgCl precipitate formed was removed by
filtration. To the solution was added the ligand (L1 and L2, 0.9 equiv),
and the reaction mixture was stirred for 24 h at 28 °C. The solvent was
evaporated under reduced pressure, and the residue was dissolved in
30 mL of MeOH. Unreacted yellow cisplatin was removed by
filtration. The filtrate was stirred vigorously, and diethyl ether (60 mL)
was added to precipitate the desired compound as solid. The product
was isolated, washed twice with 50 mL of diethyl ether, vacuum-dried,
and kept in dark.
cis-[Pt(NH3)2(L1)Cl](NO3) (1). Greenish-black solid. Yield: 72%.
Anal. Calcd for C23H29BClF2N7O3Pt (Mw: 730.17): C, 37.80; H, 4.00;
N, 13.42. Found: C, 37.61; H, 3.83; N, 13.36%. ESI-MS (m/z): Calcd
1
[M-NO3]+, 668.19; Found: 668.18. H NMR (400 MHz, DMSO-d6):
δ 8.76 (s, 1 H), 7.86 (s, 1 H), 7.47−7.40 (m, 4 H), 7.09 (s, 1 H), 6.17
(s, 2 H), 5.59 (s, 2 H), 4.18 (s, 3 H), 3.94 (s, 3 H), 2.44 (s, 6 H), 1.32
(s, 6 H). 13C NMR (100 MHz, DMSO-d6): δ 155.03, 143.77, 142.27,
139.96, 137.23, 133.03, 131.19, 128.70, 128.50, 128.17, 121.76, 120.74,
80.42, 49.66, 29.42, 14.69, 14.45. IR data (cm−1): 3300 (br), 3130
(br), 1540 (s), 1500 (s), 1300 (br), 1190 (s), 1150 (s), 975 (br). UV−
visible (1% DMSO/DMEM at pH 7.2): λmax, nm (ε, M−1 cm−1) = 530
(18 000), 500 (27 000). Emission (1% DMSO/DMEM at pH 7.2):
λem (λex, Φf) = 510 nm (490 nm, 0.09).
C
Inorg. Chem. XXXX, XXX, XXX−XXX