Formation of columnar liquid crystals on the basis of unconventional triazine-based dendrimers by the C3-symmetric approach.

Two series of unconventional triazine-based dendrimers with C(2) symmetry and C(3) symmetry were prepared. The newly prepared C(3)-symmetrical dendrimers were characterized by (1)H and (13)C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD showed that the C(3)-symmetrical dendrimers display columnar liquid-crystalline phases during thermal treatment, but the C(2)-symmetrical dendrimers were not observed to behave correspondingly. The molecular conformations of C(3)- and C(2)-symmetrical dendrimers were obtained by computer simulation with the MM2 model of the CaChe program in the gas phase. The simulation results reasonably explain the different mesogenicities of C(3)- and C(2)-symmetric dendrimers. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks for displaying columnar liquid-crystalline behavior.

Development of thiocyanate-free, charge-neutral Ru(II) sensitizers for dye-sensitized solar cells.

A new series of neutral, thiocyanate-free Ru(II) sensitizers (TFRS-1-3), which are assembled using both 4,4'-carboxy-2,2'-bypyridine and 2-pyridyl pyrazolate ancillaries, exhibit a light-harvesting capability up to 700 nm and superior DSSC performance in conversion efficiency (eta = 9.54% for TFRS-2).

Organic dyes with remarkably high absorptivity; all solid-state dye sensitized solar cell and role of fluorine substitution.

A series of new organic D-pi-A dyes, A1, A2-H and A2-F, possessing a remarkably high absorption extinction coefficient of epsilon > 5.0 x 10(4) M(-1) cm(-1) at peak wavelength were synthesized, among which, A2-F having a key fluorine substitution attains excellent all solid-state DSSC performance, with optimized parameters of eta = 4.86%, J(SC) = 7.52 mA cm(-2), V(OC) = 0.91 V, and FF = 0.71.