We report a highly efficient charge separation system, D-Pt-A, where D (triphenylamine) and A (naphthalenediimide) are bonded to the Pt moiety through highly twisted phenylene ethynylene linkages. The quantum yields for the formation of the charge-separated state were determined to be nearly unity. The lifetimes of D(+)-Pt-A(-) were approximately 1 micros at room temperature and much longer at low temperature. The spin-correlated radical ion pair was directly observed by means of time-resolved EPR spectroscopy.

A series of novel emissive Ir(III) complexes having the coordination environments of [Ir(N--N--N)2]3+, [Ir(N--N--N)(N--N)Cl]2+, and [Ir(N--N--N)(N--C--N)]2+ with 2,6-bis(1-methyl-benzimidazol-2-yl)pyridine (L1, N--N--N), 1,3-bis(1-methyl-benzimidazol-2-yl)benzene (L2H, N--C--N), 4'-(4-methylphenyl)-2,2':6',2' '-terpyridine (ttpy, N--N--N), and 2,2'-bipyridine (bpy, N--N) have been synthesized and their photophysical and electrochemical properties studied. The Ir(III) complexes exhibited phosphorescent emissions in the 500-600 nm region, with lifetimes ranging from approximately 1-10 micros at 295 K. Analysis of the 0-0 energies and the redox potentials indicated that the lowest excited state of [Ir(L1)(L2)]2+ possessed the highest contribution of 3MLCT (MLCT = metal-to-ligand charge transfer) among the Ir(III) complexes, reflecting the sigma-donating ability of the tridentate ligand, ttpy < L1 < L2. The emission quantum yields (phi) of the Ir(III) complexes ranged from 0.037 to 0.19, and the highest phi value (0.19) was obtained for [Ir(L1)(bpy)Cl]2+. Radiative rate constants (k(r)) were 1.2 x 10(4) s(-1) for [Ir(ttpy)2]3+, 3.7 x 10(4) s(-1) for [Ir(L1)(bpy)Cl]2+, 3.8 x 10(4) s(-1) for [Ir(ttpy)(bpy)Cl]2+, 3.9 x 10(4) s(-1) for [Ir(L1)2]3+, and 6.6 x 10(4) s(-1) for [Ir(L1)(L2)]2+. The highest radiative rate for [Ir(L1)(L2)]2+ with the highest contribution of 3MLCT could be explained in terms of the singlet-triplet mixing induced by spin-orbit coupling of 5d electrons in the MLCT electronic configurations.

The mechanochemical behavior of Pt(5dpb)Cl (5dpbH = 1,3-di(5-methyl-2-pyridyl)benzene) was investigated in terms of solid-state luminescence. The yellow luminescence of the crystalline complex changed to orange when grinding into fine powder on a glass substrate with a spatula. A broad emission band, which was not detected for the crystal, was observed at around 670 nm for the powder. The powder X-ray diffraction (XRD) pattern was the same as that calculated from X-ray crystallographic data of the single crystal. A broad band appeared within 100 ns after laser excitation accompanied by quenching of the s(pi,pi*) emission of Pt(5dpb)Cl, which was then weakened with decreasing temperature and disappeared below 120 K. The phenomenon was very similar to the excimer formation observed in solution. A related complex, Pt(dpb)Cl (dpbH = 1,3-di(2-pyridyl)benzene), also exhibited luminescent mechanochromism. However, the broad emission that appeared upon grinding still remained at 77 K, and XRD showed that the ground sample of Pt(dpb)Cl was amorphous.

Different types of ordered solid films of oxotitanium(IV) phthalocyanine (OTiPc) were grown in 50−500 nm thickness by vacuum deposition onto such conventional substrates as metal- and ITO-coated glass and neat glass at a rate of ∼0.05 nm s-1. Under 10-3−10-4 Pa isotropic films with short-range molecular organization and preferential molecular orientation were grown on the substrates kept at ∼25 °C but ordered α (phase II) or β (phase I) crystal films on the substrates heated at 150 °C. The deposition onto surface-oxidized Al, Ti, and Cu/glass, ITO/glass, and neat glass at ∼25 or 150 °C selectively gave ordered isotropic or α-crystal films which have preferential molecular alignments with “standing” orientations of the molecular plane with respect to the substrate surface. On the other hand, another type of ordered isotropic or β-crystal films with preferential “lying” molecular orientations was formed by the deposition onto Au, Ag, and unoxidized Cu on glass at ∼25 or 150 °C. In the case of 150 °C-heated Pt/glass, the α-crystal film with “standing” molecular orientations was grown under 10-3−10-4 Pa, but another type of α-crystal film with “lying” orientations under 2.7 × 10-5 Pa. Scanning electron microscopic observations of the ordered crystalline films indicated that single-crystal-like domains are grown from the bottom to the top of the film and are densely packed to give monolithic morphologies with little grain boundary. Visible−near-IR absorption and fluorescence spectra of the ordered solid films were recorded, showing unique dependences on the molecular alignments involving anisotropic behavior in the polarized absorption spectra of the α-crystal films with different molecular alignments.

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