A series of near-IR emitting organic light-emitting diodes (OLEDs) have been prepared using poly(vinylcarbazole) (PVK) as the hole transport polymer, aluminum quinolate (Alq3) or a sulfonamide derivative (Al(qs)3) as the host dye (H), and phthalocyanine (Pc) or naphthalocyanine (NPc) dopants as guest dyes (G). The separation of the emission spectrum of the guest dye from that of the host dye allows for independent assessment of their relative efficiencies and correlation of these efficiencies with their tendencies toward charge capture and recombination reminiscent of solution electrogenerated chemiluminescent reactions. Although the absorbance spectra of the guest dyes are significantly separated from the emission spectra of the host dyes, the high molar absorptivities of the Pc and NPc dopants lead to Förster radii and relative energy-transfer (ET) efficiencies comparable to values previously obtained for quinacridone or rubrene dopants, which have been used to create intense green or yellow emission in Alq3-based OLEDs. We show that hole capture by the guest dye from oxidized PVK, PVK+•/G → PVK/G+•, followed by cross-reactions, Alq3 -•(Al(qs)3 -•)/G+• → Alq3(Al(qs)3)/G*, can be an important charge-trapping (CT), light-producing pathway at sufficiently high concentrations of the guest dye. Relative efficiencies of Pc* or NPc* emission in these single-layer devices increased exponentially with the electrochemically predicted excess free energy for the oxidation of G to form G+• by PVK+•.

We report here an investigation of absorbance anisotropy in highly ordered, single bilayer (ca. 5.6 nm) Langmuir-Blodgett (LB) thin films of discotic liquid-crystalline phthalocyanines, using a recently introduced broad-band attenuated total reflectance (ATR) spectroscopic technique, capable of measuring dichroism in such films in the UV--visible optical region down to absorbances of ca. 0.003 absorbance units. On the basis of the ATR measurements of LB-deposited films, a thorough treatment was established to determine the ensemble average of the Cartesian components and the associated optical anisotropy of transition dipoles in the molecular film. In an effort to recover order parameters of molecular orientation, those results were interpreted with a circular dipole model, which is the expected model for the isolated molecule based on symmetry properties. We measured a strong dipole component normal to the film plane that cannot be explained in terms of a truly circular model, indicating that the molecular transition dipoles were perturbed upon aggregation. The utility of the experimental approach was further demonstrated by (a) investigating the effect of substrate modifiers (methyl- and phenyl-terminated silanes) on the ordering within the phthalocyanine film and (b) the effect of water immersion and re-annealing of the thin film on molecular ordering and optical anisotropy.

The reaction between the previously reported site-differentiated cluster solvate [Re(6)(mu(3)-Se)(8)(PEt(3))(5)(MeCN)](SbF(6))(2) (1) with pyridyl-based ditopic ligands 4,4'-trimethylenedipyridine (2), 1,2-bis(4-pyridyl)ethane (3), and (E)-1,2-bis(4-pyridyl)ethene (4) afforded cluster complexes of the general formula [Re(6)(mu(3)-Se)(8)(PEt(3))(5)(L)](SbF(6))(2) (5-7), where L represents one of the pyridyl-based ligands. Reacting these cluster complex-based ligands with the fully solvated cluster complex [Re(6)(mu(3)-Se)(8)(MeCN)(6)](SbF(6))(2) (8) produced dendritic arrays of the general formula {Re(6)(mu(3)-Se)(8)[Re(6)(mu(3)-Se)(8)(PEt(3))(5)(L)](6)}(SbF(6))(14) (9-11), each featuring six circumjacent [Re(6)(mu(3)-Se)(8)(PEt(3))(5)](2+) units bridged to a [Re(6)(mu(3)-Se)(8)](2+) core cluster by the pyridyl-based ligands. Electrochemical studies using a thin-layer electrochemical cell revealed cluster-based redox events in these cluster arrays. For 9 (L = 2), one reversible oxidation event corresponding to the removal of 7 electrons was observed, indicating noninteraction or extremely weak interactions between the clusters. For 10 (L = 3), two poorly resolved oxidation waves were found. For 11 (L = 4), two reversible oxidation events, corresponding respectively to the removal of 1 and 6 electrons, were observed with the 1-electron oxidation event occurring at a potential 150 mV more positive than the 6-electron oxidation. These electrochemical studies suggest intercluster coupling in 11 via through-bond electronic delocalization, which is consistent with electronic spectroscopic studies of this same molecule.

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The first incorporation of quinacridone, a technologically important organic electroluminescent emitter, into dendrimers increases solubility, decreases aggregation, retards heterogeneous electron transfer, and enhances luminescence in condensed phases (powders and thin films).