Slow Long-Term Exhumation of the West Central Andean Plate Boundary, Chile.

We present a regional analysis of new low-temperature thermochronometer ages from the Central Andean fore arc to provide insights into the exhumation history of the western Andean margin. To derive exhumation rates over 10 million-year timescales, 38 new apatite and zircon (U-Th)/He ages were analyzed along six ~500-km long near-equal-elevation, coast parallel, transects in the Coastal Cordillera (CC) and higher-elevation Precordillera (PC) of the northern Chilean Andes between latitudes 18.5°S and 22.5°S. These transects were augmented with age-elevation profiles where possible. Results are synthesized with previously published thermochronometric data, corroborating a previously observed trenchward increase in cooling ages in Peru and northern Chile. One-dimensional thermal-kinematic modeling of all available multichronometer equal-elevation samples reveals mean exhumation rates of <0.2 km/Myr since ~50 Ma in the PC and ~100 Ma in the CC. Regression of pseudovertical age-elevation transects in the CC yields comparable rates of ~0.05 to ~0.12 km/Myr between ~40 and 80 Ma. Differences between the long-term mean 1-D rates and shorter-term age-elevation-derived rates indicate low variability in the exhumation history. Modeling results suggest similar background exhumation rates in the CC and PC; younger ages in the PC are largely a function of increased heat flow and consequently an elevated geothermal gradient near the arc. Slow exhumation rates are suggestive of semiarid conditions across the region since at least the Eocene and deformation and development of the Andean fore arc around this time.

Fluorescent benzene-centered mono-, bis- and tris-triazapentadiene-boron complexes.

A series of novel benzene centered mono-, bis- and tris-1,3,5-triazapentadiene ligands was synthesized and investigated with respect to their reactivity towards triphenylborane. The resulting blue-fluorescent boron complexes with a six-membered ring chelate structure show excellent thermal and chemical stability. All title compounds were completely characterized including X-ray diffraction studies for and . Whereas the absorption spectra of all three classes of compounds are similar, the fluorescence spectra show distinct differences. Thus, the emission spectra of show Stokes shifts of 4100-6700 cm(-1) with low quantum yields both in solution and in the solid state. However, the more bulky compounds show markedly larger molar extinction coefficients and smaller bathochromic shifts compared to . For all compounds, we observe significantly more intense red-shifted fluorescence in the solid state compared to that in dichloromethane solutions. For the interpretation of the absorption properties TD-DFT studies were performed based on DFT geometry optimizations.

Fluorescent modular boron systems based on NNN- and ONO-tridentate ligands: self-assembly and cell imaging.

We have synthesized a series of new fluorescent boron systems 1a-c and 2a-d based on nitrogen (NNN) or nitrogen and oxygen (ONO)-containing tridentate ligands. These novel dyes are characterized by high thermal and chemical stability. They show large Stokes shifts (mostly above 3200 cm(-1)) and quantum yields in solution and in the solid state up to 40%. The easy, modular synthesis facilitates the convenient variation of the axial substituent on the central boron atom, allowing the functionalization of this dye for biochemical use. Introducing a long alkyl chain with a phenyl spacer at this axial position enables the self-assembly of the boron compound 2d to form a fluorescent vesicle, which is able to encapsulate small molecules such as sulforhodamine. Additionally, boron compound 2d was found to serve as a dye for cell imaging since it has the capability of binding to the nuclear membranes of HeLa cells. With phospholipids such as DOPC, giant unilamelar vesicles (GUV) are formed. These results demonstrate the wide applicability of this new boron system in supramolecular and medicinal chemistry.

Ag(I) and Au(I) complexes of sterically crowded cyclic phosphinimine ligands.

Cyclic phosphinimines are strong bases with structural similarities to carbene ligands. The cyclic phosphinimines R(2)PNCPh(2)(CH(2)CH(CO(2)Me)) (R = Ph 4, i-Pr 5, Me 6), R(2)PNCPh(2)(CCOMe)(2) (R = Ph 7, i-Pr 8) and Ph(2)PNCPh(2)(CH(2)CH(CN)) 9 are readily prepared via cycloaddition of the compounds R(2)PNCPh(2) (R = Ph 1, i-Pr 2, Me 3) and olefins or alkynes. In the case of 4 this phosphinimine proved to be moisture sensitive, converting to Ph(2)C(NH(2))CH(CO(2)Me)CH(2)P(O)Ph(2)10 upon hydrolysis. Nonetheless, the Ag(i) and Au(i) complexes [{Ph(2)PNCPh(2)(CH(2)CH(CO(2)Me)}(2)Ag][NO(3)] 11 (Ph(2)PNCPh(2)(CH(2)CH(CO(2)Me)AuCl 12 and (Ph(2)PNCPh(2)(C(CO(2)Me)(2))AuCl 13 were prepared and characterized. Compounds 1, 2 and 7-13 have been characterized crystallographically.