Organometallics
Article
aug-cc-pVQZ63 with the gradient-corrected exchange-correlation
functional BP8664 or the hybrid functional B3LYP65−68 were used.
For UV−vis calculations, the molecular structures were first optimized
using a conductor-like screening model (COSMO)69,70 implemented
in TURBOMOLE/ORCA using the respective dielectric constant of
the desired solvent.70
Vibrationally Resolved Emission Spectra. The quantum-
chemical calculations of vibrational Franck−Condon spectra and
optimized geometries were carried out with the quantum chemistry
package Gaussian 09 Rev. D.01.71 The CAM-B3LYP functional72 was
used in the density functional theory (DFT) calculations with the
SDD basis set, which applies an effective core potential for the Pt
atoms,73 and the D95 basis set for H, C, N, and O atoms.74
Vibrational Franck−Condon spectra were calculated according the
method of Barone et al.75,76 with Kohn−Sham DFT-based geometry
optimizations in the S0 and T1 states followed by frequency analysis
calculations.
The energies were corrected by zero-point vibrational energies and
thermal free energy contributions. In order to calculate the overlap
integrals for the vibronic spectra, the transitions are divided into
classes Cn, where n is the number of the excited normal modes in the
final electronic state. The maximum number of quanta per mode was
set to 100 and the maximum number of quanta for combinations of
two modes to 65. The number of integrals calculated was limited to
1.5 × 108. A maximum of 20 classes was computed. The line spectrum
was broadened by Gaussian functions with a half-width at half-
maximum of 500 cm−1. The solvent dichloromethane (DCM) was
taken into account by the polarizable continuum model (PCM) in an
integral equation formalism framework77 with atomic radii from the
universal force field model (UFF).78
more detail, aiming to develop them as bifunctional targeting
inhibitors or agents for photodynamic therapy, diagnostics, or
bioimaging.
EXPERIMENTAL SECTION
■
Instrumentation. 1H, 13C, and19F NMR spectra were recorded on
a Bruker Avance II 300 MHz (1H, 300.13 MHz; 13C, 75.47 MHz)
double-resonance (BBFO) 5 mm probe head with z-gradient coil, a
Bruker Avance 400 MHz (1H, 400.13 MHz; 13C, 100.61 MHz; 19F,
376.50 MHz) using a triple-resonance 1H, 19F, BB inverse probe head,
or Bruker Avance II 600 MHz spectrometer (1H, 600.13 MHz; 13C,
150.93 MHz) with a triple-resonance (TBI) 5 mm inverse probe head
with z-gradient coil. The unambiguous assignment of the 1H
resonances was obtained from 1H NOESY and 1H COSY experi-
ments. All 2D NMR experiments were performed using standard
pulse sequences from the Bruker pulse program library. Chemical
shifts are relative to TMS respectively. UV−vis absorption spectra
were recorded with Varian Cary 05E and Cary 50 scan
spectrophotometers. Photoluminescence spectra at room temperature
were recorded with a Spex FluoroMax-3 spectrometer. A PicoQuant
Fluo-Time 300 spectrometer was used for lifetime measurements.
Lifetime analysis was performed using the commercial FluoFit
software. The quality of the fit was assessed by minimizing the
reduced χ2ς function. Luminescence quantum yields were determined
with a Hamamatsu Photonics absolute PL quantum yield measure-
ment system (C9920-02), equipped with a L9799-01 CW xenon light
source, monochromator, photonic multichannel analyzer, and
integrating sphere (a maximum error of 5% for Φ is estimated).
All solvents were of spectroscopic grade and were degassed prior to
use. Elemental analyses were obtained using a HEKAtech CHNS
EuroEA 3000 analyzer. EI-MS spectra were measured with a Finnigan
MAT 95 instrument, and HR-ESI-MS spectra were measured using a
THERMO Scientific LTQ Orbitrap XL instrument. MS Simulations
were performed using ISOPRO 3.0. IR spectra were measured in ATR
mode using a PerkinElmer 400 FT-IR spectrometer. Electrochemical
measurements were carried out in 0.1 M nBu4NPF6/THF solution
using a three-electrode configuration (glassy-carbon working elec-
trode, Pt counter electrode, Ag/AgCl reference electrode) and a
Metrohm Autolab PGSTAT30 potentiostat and function generator.
The ferrocene/ferrocenium couple served as aninternal reference.
XRD single-crystal structure analysis was carried out for [Pt(ph-
Character of T1 State. The character of the emissive T1 state was
determined by TDDFT calculations, including 20 excited singlet and
triplet states at the T1 geometry optimized with Kohn−Sham DFT
with multiplicity 3.
Absorption Spectra. To obtain the UV−vis absorption spectrum
of the complexes J−L, TDDFT calculations of the 40 lowest excited
singlet states were performed with the PBE0 functional79 and the
SDD basis set. A Lorentzian broadening with a half-width at half-
maximum (HWHM) of 15 nm was used for each transition.
Antiproliferative Activity. For the screening of the antiprolifer-
ative effects of the compounds, we followed an established
procedure.80 In short, cells were suspended in cell culture medium
(HT-29, 2850 cells/mL; MDA-MB-231, 10000 cells/mL), and 100
μL aliquots thereof were plated in 96-well plates and incubated at 37
°C with 5% CO2 for 72 h for HT-29 or 96 h for MDA-MB-231,
respectively. Stock solutions of the compounds in dimethylformamide
(DMF) were freshly prepared and diluted with cell culture medium to
the desired concentrations (final DMF concentration: 0.1% v/v). The
medium in the plates was replaced with medium containing the
compounds in graded concentrations (six replicates). After further
incubation for 72 h (HT-29) or 96 h (MDA-MB-231) the cell
biomass was determined by crystal violet staining and the IC50 values
were determined as those concentrations causing 50% inhibition of
cell proliferation. Results and uncertainties were calculated from three
independent experiments.
For the determination of the effect of a mitochondria-targeting cell-
penetrating peptide on the cellular viability and antiproliferative
effects of [Pt(ph(py)ph)(DMSO)] and [Pt(ph(py)ph)(MeCN)],
HT-29 and MCF-7 cells were seeded in 96-well plates and grown to a
subconfluency of ∼20−30%. On the next day, cells were added to the
cells after short preincubation of the peptide ALD5-sC18 and the Pt
complexes in serum-free media. After 24 h the cells were washed using
PBS and incubated for further 48 h at 37 °C using fresh serum-
containing media. Cell viability was confirmed using a rasazurin/
resofurin-based test (Sigma-Aldrich). The cells were washed twice
using PBS, while positive controls were treated with 70% EtOH for 10
min. The cells were incubated in 1/10 dilution (v/v in serum-free
medium) for 1−2 h at 37 °C. Emission of resofurin was detected at
595 nm (λex = 550 nm) on a Tecan infinite M200 plate reader.
̅
(Fppy)ph)(DMSO)]·CH2Cl2 (P1, No. 2) and [Pt(Brph(ppy)Brph)-
(DMSO)] (Pca21, No. 29; contains two independent molecules).
Crystals were obtained from concentrated solutions in dry CH2Cl2
layered carefully with dry n-hexane. Measurements of the complexes
were performed at 293(2) K using an IPDS II (STOE and Cie) or an
Gemini CCD S Ultra diffractometer (Oxford Diffraction), both with
Mo Kα radiation (λ = 0.71073 Å) employing a ω−ϕ−2θ scan
technique. The structures were solved by direct methods using SIR
9253 or SIR2014,54 and refinement was carried out with SHELXL
2
201655 employing full-matrix least-squares methods on Fo ≥ 2σ(Fo ).
2
The numerical absorption corrections (X-RED V1.22; Stoe & Cie,
2001) were performed after optimizing the crystal shapes using X-
SHAPE V1.06 (Stoe & Cie, 1999). The non-hydrogen atoms were
refined with anisotropic displacement parameters without any
constraints. The hydrogen atoms were included by using appropriate
riding models. Data of the structure solutions and refinements
(CCDC number 1969432 for [Pt(Brph(ppy)Brph)(DMSO)] and
1969434 for [Pt(ph(Fppy)ph)(DMSO)]·CH2Cl2) can be obtained
the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge, CB2 1EZ U.K. (fax, + 44-1223 336033; e-mail,
Computational Details. Ground-state electronic structure
calculations on the complexes have been done in the framework of
density functional theory (DFT) using the resolution of the identity
Coulomb approximation56,57 employing the ORCA58 and the
TURBOMOLE59 program packages with the TMoleX 4.260 user
interface. The basis sets def-SV(P),61 def2-TZVP, def2-TZVPP,62 and
G
Organometallics XXXX, XXX, XXX−XXX