RESUMEN
Coupling two magnetic anisotropic lanthanide ions via a direct covalent bond is an effective way to realize high magnetization blocking temperature of single-molecule magnets (SMMs) by suppressing quantum tunneling of magnetization (QTM), whereas so far only single-electron lanthanide-lanthanide bonds with relatively large bond distances are stabilized in which coupling between lanthanide and the single electron dominates over weak direct 4f-4f coupling. Herein, we report for the first time synthesis of short Dy(II)-Dy(II) single bond (3.61 Å) confined inside a carbon cage in the form of an endohedral metallofullerene Dy2@C82. Such a direct Dy(II)-Dy(II) covalent bond renders a strong Dy-Dy antiferromagnetic coupling that effectively quenches QTM at zero magnetic field, thus opening up magnetic hysteresis up to 25 K using a field sweep rate of 25 Oe/s, concomitant with a high 100 s magnetization blocking temperature (TB,100s) of 27.2 K.
RESUMEN
Metal complexes bearing single-electron metal-metal bonds (SEMBs) exhibit unusual electronic structures evoking strong magnetic coupling, and such bonds can be stabilized in the form of dimetallofullerenes (di-EMFs) in which two metals are confined in a carbon cage. Up to now, only a few di-EMFs containing SEMBs are reported, which are all based on a high-symmetry icosahedral (Ih) C80 cage embedding homonuclear rare-earth bimetals, and a chemical modification of the Ih-C80 cage is required to stabilize the SEMB. Herein, by introducing 3d-block transition metal titanium (Ti) along with 4f-block lanthanum (La) into the carbon cage, we synthesized the first crystallographically characterized SEMB-containing 3d-4f heteronuclear di-EMFs based on pristine fullerene cages. Four novel La-Ti heteronuclear di-EMFs were isolated, namely, LaTi@D3h(5)-C78, LaTi@Ih(7)-C80, LaTi@D5h(6)-C80, and LaTi@C2v(9)-C82, and their molecular structures were unambiguously determined by single-crystal X-ray diffraction. Upon increasing the cage size from C78 to C82, the La-Ti distance decreases from 4.31 to 3.97 Å, affording fine-tuning of the metal-metal bonding and hyperfine coupling, as evidenced by an electron spin resonance (ESR) spectroscopic study. Density functional theory (DFT) calculations confirm the existence of SEMB in all four LaTi@C2n di-EMFs, and the accumulation of electron density between La and Ti atoms shifts gradually from the proximity of the Ti atom inside C78 to the center of the LaTi bimetal inside C82 due to the decrease of the La-Ti distance. The electronic properties of LaTi@C2n heteronuclear dimetallofullerenes differ apparently from their homonuclear La2@C2n counterparts, revealing the peculiarity of heteronuclear dimetallofullerenes with the involvement of 3d-block transition metal Ti.
RESUMEN
Encapsulating photoluminescent lanthanide ions like erbium (Er) into fullerene cages affords photoluminescent endohedral metallofullerenes (EMFs). Few reported photoluminescent Er-EMFs are all based on encapsulation of multiple (two to three) metal atoms, whereas mono-Er-EMFs exemplified by Er@C82 are not photoluminescent due to its narrow optical bandgap. Herein, by entrapping an Er-cyanide cluster into various C82 cages to form novel Er-monometallic cyanide clusterfullerenes (CYCFs), ErCN@C82 (C2 (5), Cs (6), and C2 v (9)), the photoluminescent properties of CYCFs are investigated, and obvious near-infrared (NIR) photoluminescence only is observed for ErCN@C2 (5)-C82 . Combined with a comparative photoluminescence study of three medium-bandgap di-Er-EMFs, including Er2 @Cs (6)-C82 , Er2 O@Cs (6)-C82 , and Er2 C2 @Cs (6)-C82 , this study proposes that the optical bandgap can be used as a simple criterion for switching the photoluminescence of Er-EMFs, and the bandgap threshold is determined to be between 0.83 and 0.74 eV. Furthermore, the photoluminescent patterns of these three di-Er-EMFs differ dramatically. It is found that the location of the Er atom within the same Cs (6)-C82 cage is almost fixed and independent on the endo-unit; thus the previous statement on the key role of metal position in photoluminescence of di-Er-EMFs seems erroneous, and the geometric configuration of the endo-unit, especially the bridging mode of two Er ions, is decisive instead.
RESUMEN
A novel paradigm in tumor biology suggests that non-small cell lung cancer (NSCLC) growth is driven by lung cancer stem cell-like cells (LCSCs), but molecular mechanisms regulating tumorigenic and self-renewal potential of LCSCs are still unclear. Here, we aim to investigate biological function of SLC34A2 in regulating tumorigenicity of LCSCs and its underlying mechanisms. Our findings testified that CD166(+) cells which were derived from fresh primary NSCLC samples displayed stem cell-like features. Fluorescence-activated cell sorting (FACS) analysis showed the presence of a variable fraction of CD166 cells in 15 out of 15 NSCLC samples. Significantly, CD166(+) LCSCs from primary NSCLC tumors expressed high level of SLC34A2 which was required for CD166(+) LCSCs tumorigenic and self-renewal potential. In NSCLC patient cohort, increased SLC34A2 expression correlated with histology, which suggests a potential role of SLC34A2 in CD166(+) LCSCs. Furthermore, Wnt/ß-catenin pathway and Bmi1 were found necessary for tumorigenicity and self-renewal capacity of CD166(+) LCSCs by a series in vitro and in vivo experiments. Then, our study indicated that SLC34A2 regulated Bmi1 to promote tumorigenic and self-renewal potential of CD166(+) LCSCs through Wnt/ß-catenin pathway. In this study, the characterization of molecular basis of SLC34A2 in CD166(+) LCSCs not only allows for better understanding of the mechanisms regulating tumorigenicity of this specific population of NSCLC cells but also provides insight into the gradual improvement of more effective cancer therapies against this disease.
