The polarization emission spectrum and the angular dependence of polarization ratio of the blue emission from KCl:Eu2+ were investigated at 78.8 K. The polarized emission at 420 nm consisted of several components. The angular dependence of polarization ratio of each component is proportional to sin(2 ) or -cos(2 ), when the exciting light is polarized at with respect to the z -axis for the [100]-[010] optical arrangement. The relaxed excited states (RESs) of Eu2+ responsible for the 420 nm emission are presented in terms of the adiabatic potential energy surface (APES), taking into account the Jahn-Teller effect (JTE) coupling to the Eg mode and the spin-orbit (SO) interaction. The charge-compensating cation vacancy (CCV, Vc - ) also causes an additive perturbation.

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2,6-Didodecyl-4,8-diphenyl-benzo[1,2-d;4,5-d']bisthiazole (3) and 2,6-didodecyl-4,8-dipyrrole-2-yl-benzo[1,2-d;4,5-d']bisthiazole (5) were synthesized, and their optical properties were investigated in solution and in the solid state. Compounds 3 and 5 were excited with the 325 nm He-Cd laser line to produce blue and green luminescence, respectively. The luminescence of 5 (Phi = 14%) was more efficient than that of 3 (Phi = 5%). Structural and optical properties were further determined with DFT and ZINDO calculations. The planar structure of 5 results in pi --> pi* electronic transitions from the pyrrole moiety to the benzobisthiazole frame, while the twisted geometry of 3 results in luminescence strongly associated with the pi --> pi* transitions within the benzothiazole frame. The effect of solvent on the luminescence properties of 5 is summarized as competition between intra- and intermolecular NH...N hydrogen bonds.

A series of stable and inert complexes with ErIII cores and dendritic PtII‐porphyrin ligands exhibit strong near‐IR (NIR) emission bands via highly efficient energy transfer from the excited triplet state of the PtII‐porphyrin ligand to Er3+ ions. The NIR emission intensity of thin films of ErIII complexes at 1530 nm, originating from 4f–4f electronic transitions from the first excited state (4I13/2) to the ground state (4I15/2) of the Er3+ ion, is dramatically enhanced upon increasing the generation number (n) of the aryl ether dendrons because of site‐isolation and light‐harvesting (LH) effects. Attempts are made to distinguish the site‐isolation effect from the LH effect in these complexes. Surprisingly, the site‐isolation effect is dominant over the LH effect in the Er3+‐[Gn‐PtP]3(terpy) (terpy: 2,2′:6′,2″‐terpyridine) series of complexes, even though the present dendrimer systems with ErIII cores have a proper cascade‐type energy gradient. This might be due to the low quantum yield of the aryl ether dendrons. Thus, the NIR emission intensity of Er3+‐[G3‐PtP]3(terpy) is 30 times stronger than that of Er3+‐[G1‐PtP]3(terpy). The energy transfer efficiency between the PtII‐porphyrin moiety in the dendritic PtII‐porphyrin ligands and the Ln3+ ion increases with increasing generation number of the dendrons from 12–43 %. The time‐resolved luminescence spectra in the NIR region show monoexponential decays with a luminescence lifetime of 0.98 μs for Er3+‐[G1‐PtP]3(terpy), 1.64 μs for Er3+‐[G2‐PtP]3(terpy), and 6.85 μs for Er3+‐[G3‐PtP]3(terpy) in thin films of these complexes. All the ErIII‐cored dendrimer complexes exhibit excellent thermal stability and photostability, and possess good solubility in common organic solvents.