ABSTRACT
In the present work, new rhenium(i) polypyridyl compounds, fac-[Re(L)(CO)3(cbz2phen)](+/0) where cbz2phen = 4,7-di(9H-carbazol-9-yl)-1,10-phenanthroline and L = Cl(-), pyridine (py) or 2-aminomethylpyridine (ampy) were synthesized and characterized by (1)H NMR, UV-Vis and IR spectroscopy combined with theoretical calculations using time-dependent density functional theory (TD-DFT). Their photophysical properties were investigated by steady state and time-resolved emission spectroscopy. These compounds show a strong and broad absorption band around 350-500 nm that, also by TD-DFT, corresponds to the carbazol â phenanthroline intraligand charge transfer transition, (1)ILCTcbz2phen, with some contribution of the Re(i) â phenanthroline metal-to-ligand charge transfer transition, (1)MLCTReâcbz2phen. In contrast to typical Re(i) polypyridyl complexes, cbz2phen-based Re(i) compounds exhibit two emission maxima in CH3CN solution and relatively low emission quantum yields, 10(-3)-10(-2). Solution phase time-resolved photoluminescence and excited state quenching experiments provided meaningful information on the presence of multiple emitter states after light excitation, which were identified as an (1)ILCTcbz2phen excited state deactivation at higher energies and a long-lived phosphorescence attributed to the (3)MLCTReâcbz2phen excited state. When embedded into a PMMA matrix, the radiative decay from the singlet state is inhibited and the contribution of both (3)MLCT and (3)ILCTcbz2phen to the luminescence is observed. The photophysics of these Re(i) compounds reported herein provide new insights into the understanding of substitutional groups on the polypyridyl ligands that are relevant to practical and fundamental development of photo-induced molecular devices.
ABSTRACT
10-(Octyloxy) decyl-2-(trimethylammonium) ethyl phosphate (ODPC) is an alkylphospholipid that can interact with cell membranes because of its amphiphilic character. We describe here the interaction of ODPC with liposomes and its toxicity to leukemic cells with an ED-50 of 5.4, 5.6 and 2.9 microM for 72 h of treatment for inhibition of proliferation of NB4, U937 and K562 cell lines, respectively, and lack of toxicity to normal hematopoietic progenitor cells at concentrations up to 25 microM. The ED-50 for the non-malignant HEK-293 and primary human umbilical vein endothelial cells (HUVEC) was 63.4 and 60.7 microM, respectively. The critical micellar concentration (CMC) of ODPC was 200 microM. Dynamic light scattering indicated that dipalmitoylphosphatidylcholine (DPPC) liposome size was affected only above the CMC of ODPC. Differential calorimetric scanning (DCS) of liposomes indicated a critical transition temperature (T(c)) of 41.5 degrees C and an enthalpy (H) variation of 7.3 kcal mol(-1). The presence of 25 microM ODPC decreased T(c) and H to 39.3 degrees C and 4.7 kcal mol(-1), respectively. ODPC at 250 microM destabilized the liposomes (36.3 degrees C, 0.46 kcal mol(-1)). Kinetics of 5(6)-carboxyfluorescein (CF) leakage from different liposome systems indicated that the rate and extent of CF release depended on liposome composition and ODPC concentration and that above the CMC it was instantaneous. Overall, the data indicate that ODPC acts on in vitro membrane systems and leukemia cell lines at concentrations below its CMC, suggesting that it does not act as a detergent and that this effect is dependent on membrane composition.
