Metal-centered phosphorescent

Nolte et al. have attached a CD to each pyridine ring of a [Ru(bpy)2+] core to generate the impressively large superstructures of 62 and 63 [396], The metal center is so insulated from the external environment by the CD periphery that oxygen is unable to quench MLCT phosphorescence. 63 was the focus of chemosensor investigations because its luminescence is very intense, exceeding that of the native Ru(bpy)2+ complex. Addition of the electron ac-... 

Therefore, this low-energy band is assigned to a metal-centered d->p transition instead of as arising from Au---Au interactions. The solid-state luminescence spectrum (Fig. 25) exhibits a phosphorescence emission band centered at 417 nm. This value compares favorably with those reported for solids K[Au(CN)2]58 and Au2(dmb)(CN)2.63... 

The optical and PL spectroscopies have been undertaken to understand the structure-property correlations of this important family of triplet-emitting polymers. The red shift in the absorption features upon coordination of the metal groups is consistent with there being an increase in conjugation length over the molecule through the metal center. The trade-olf relationship between the phosphorescence parameters (such as emission wavelength, quantum yield, rates of radiative and nonradiative decay) and the optical gap will be formulated. For systems with third-row transition metal chromophores in which the ISC efficiency is close to 100%,76-78 the phosphorescence radiative (kr)y, and nonradiative (/cm)p decay rates are related to the measured lifetime of triplet emission (tp) and the phosphorescence quantum yield ([Pg.300]

In this review, the synthesis, properties, and applications in optoelectronic fields of polyfluorenes with on-chain metal centers have been briefly summarized. Metal complexes involving iridium(III), platinum(II), europium(III), rhenium(I), and ruthenium(II) complex coupled with polyfluorene are surveyed. Efficient energy transfer from polymer main-chain to metal-centers can occur in these host-guest systems. These kinds of novel polymers are usually applied in the fields of phosphorescent OLEDs, memory devices, and sensors. In particular, the realization of efficient energy transfer and phosphorescence offers a huge potential for future optoelectronic devices based on these kinds of materials. 

The synthesis, optical, and structural properties of another Pt(II) polyyne-containing biphenyl moiety, P12, were reported recently.44 The system has also been extended to the Au(I) and Hg(II) congeners (see Sections IV and V). The influence of the metal center on the spatial extent of S and T excited states was characterized in detail. The ligand-based phosphorescence emissions can be harvested by the heavy-atom effect of these transition metals, which facilitates efficient intersystem crossing from the S] state to the T] state. 

In contrast, emission from [Rh(bipy)2X2] is from a metal-centered, d-d) state. The various low-lying excited states for [Rh(bipy)2Cl2] are represented in Figure 3, with initial excitation into the (ti-te ) ligand state followed by relaxation and eventual phosphorescence from the d-d) state. The rise times for phosphoresence were reported to be 350-630 ns in room temperature solution and at 77 but these values were later found to be artifacts of the detection system. " The emitting dr-d) states of [Rh(bipy)2X2] absorb at 580 (X = Cl) and 550 nm (X = Br), and the lifetimes of their transient absorptions (measured by time-resolved absorption spectroscopy in air-saturated ethanol-methanol (4 1) solution at room temperature) were found to be 84 ns (X = Cl) and 54 ns (X = Br). " (If the solutions are deoxygenated, the lifetimes increase by about a factor of five.) The presumed relaxation path is represented in equation (147), with the rate of internal conversion (IC) a 4 X 10 " s ", followed by intersystem crossing (ISC), localized within the rf-manifold, with the rate constant ca. 8 x 10. 

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