Highly efficient dye-sensitized solar cells based on panchromatic ruthenium sensitizers with quinolinylbipyridine anchors.

Panchromatic Ru(II) sensitizers TF-30-TF-33 bearing a new class of 6-quinolin-8-yl-2,2'-bipyridine anchor were synthesized and tested under AM1.5 G simulated solar irradiation. Their increased π conjugation relative to that of the traditional 2,2':6',2''-terpyridine-based anchor led to a remarkable improvement in absorptivity across the whole UV-Vis-NIR spectral regime. Furthermore, the introduction of a bulky tert-butyl substituent on the quinolinyl fragment not only led to an increase in the JSC  value owing to the suppression of dye aggregation, but remarkably also resulted in no loss in VOC in comparison with the reference sensitizer containing a tricarboxyterpyridine anchor. The champion sensitizer in DSC devices was found to be TF-32 with a performance of JSC =19.2 mA cm(-2) , VOC =740 mV, FF=0.72, and η=10.19 %. This 6-quinolin-8-yl-2,2'-bipyridine anchor thus serves as a prototype for the next generation of Ru(II) sensitizers with any tridentate ancillary.

N-heterocyclic carbene Pt(II) complexes from caffeine: synthesis, structures and photoluminescent properties.

The caffeine-derived N-heterocyclic carbene (NHC) complex [Pt(II)(C^N)(NHC)Cl] (C^N = 2-phenylpyridine), 4 has the opposite stereochemistry and a shorter Pt-C(carbene) bond compared to that of an analogous benzimidazole-derived N,N-heterocyclic carbene (NNHC) Pt complex 2. These suggest a lower trans influence of pyridyl N compared to cyclometallated carbon and an increased Pt-NHC π-backbonding because of decreased π-donation resulting from conjugation to the electron deficient pyrimidine of caffeine. Complex 4 has a lower emission quantum yield (Φ) and is blue-shifted into the green region of the visible spectrum relative to non-carbene Pt(II) cyclometalated complex 5.

Mesomorphism and luminescence properties of platinum(II) complexes with tris(alkoxy)phenyl-functionalized pyridyl pyrazolate chelates.

A series of new mesomorphic platinum(II) complexes 1-4 bearing pyridyl pyrazolate chelates are reported herein. In this approach, pyridyl azolate ligands have been strategically functionalized with tris(alkoxy)phenyl groups with various alkyl chain lengths. As a result, they are ascribed to a class of luminescent metallomesogens that possess distinctive morphological properties, such as their intermolecular packing arrangement and their associated photophysical behavior. In CH(2) Cl(2), independent of the applied concentration in the range 10(-6)-10(-3) M, all Pt(II) complexes exhibit bright phosphorescence centered at around 520 nm, which is characteristic for monomeric Pt(II) complexes. In stark contrast, the single-crystal X-ray structure determination of [Pt(C4pz)(2)] (1) shows the formation of a dimeric aggregate with a notable Pt⋅⋅⋅Pt contact of 3.258 Å. Upon heating, all Pt(II) complexes 1-4 melted to form columnar suprastructures, for which similar intracolumnar Pt⋅⋅⋅Pt distances of approx. 3.4-3.5 Šare observed within an exceptionally wide temperature range (>250 °C), according to the powder XRD data. Upon casting into a neat thin film at RT, the luminescence of 1-4 is dominated by a red emission that spans 630-660 nm, which originates from the one-dimensional, chainlike structure with Pt-Pt interaction in the ground state. Taking complex 4 as a representative, the emission intensity and wavelength were significantly decreased and blueshifted, respectively, on heating from RT to 250 °C. Further heating to liquefy the sample alters the red emission back to the green phosphorescence of the monomer. The results highlight the pivotal role of tris(alkoxy)phenyl groups in the structural versus luminescence behavior of these Pt(II) complexes.