Luminescence quantum yields

The absorption and luminescence spectra of imidazo[ 1,2,4]triazines and related compounds were recorded. The phenyl groups on both the 6-and the 7-positions quenched the luminescence. An acceptor substituent such as CHO in position-7 sharply reduced the luminescence quantum yield (82MI4). A detailed study of the infrared spectra of imidazotriazines was carried out (75T433). 

The higher branched derivatives of the spiro compounds, 43 and 44 also exhibit spectral narrowing under pulsed excitation, with emission lines at 428 and 443 nm, and line widths of 3.2 and 3.9 nm, respectively (Fig. 3.24). For the same film thickness, the threshold is lower for 4-Spiro2 than for spiro-sexiphenyl despite the lower absorption, which is attributed to the higher luminescence quantum yield. 

High-wavelength independent luminescence quantum yields that can exceed 0.5, although 0.04 to 0.2 is more typical/5-7 However, even these modest values are adequate for a variety of sensor applications. 

Figure 4.1. Relative luminescence quantum yield (a) and absorption spectrum of Ru(bpyh2+ in methanol at room temperature (b, c) (7), The decline in luminescence yields at the extremes are experimental artifacts. (Reprinted from Ref. 10 with permission, Copyright 1971 American Chemical Society.)...

All of the ruthenium polymers show emission when excited at (absorption). A large Stokes shift and a small quantiun yield characterize the emission behavior the luminescence quantum yield of the polymers is 1%. Thermo-gravimetric analyses in air indicate high thermal stabihty of the polymers, with thermal decomposition starting at approximately 290 °C. The polymers have no glass transition temperature. 

X -Ray powder pattern studies of the complexes [M(phen)2X2]" and [M(bipy)2YZ]"+ [M = Co, Rh, Ir, or Os X = Cl, H2O, or ox YZ = CI2 or (0H)(H20)] show that each metal in each series is isomorphous. A cis configuration is therefore assigned to all complexes. Luminescence quantum yields have been measured for a series of [IrCl2(N—N)2C1 complexes (N—N = phen or bipy, or diphenyl derivatives), permitting a quantitative estimate of the effect of ligand phenyl substituents.A normal-co-ordinate analysis (i.r. has been carried out for [Ir(NH3)5Cl]Cl2. ... 

Figure 2. Schematic representation of some relevant ground and excited-state properties of Ru(bpy)j. MLCT and MLCT are the spin-allowed and spin-forbidden metal-to-ligand charge transfer excited states, responsible for the high intensity absorption band with = 450 nm and the luminescence band with = 615 nm, respectively. The other quantities shown are intersystem crossing efficiency energy (E°°) and lifetime (x) of the MLCT state luminescence quantum yield ( ) quantum yield for ligand detachment (O,). The reduction potentials of couples involving the ground and the MLCT excited states are also indicated.

Latva, M. Takalo, H. Mukkala, V.- . Matachescu, C. Rodrfguez-Ubis, J.-C. Kankare, J. Correlation between the lowest triplet state energy level of the ligand and lanthanide(III) luminescence quantum yield. J. Luminesc. 1997, 75, 149-169. 

Brunet, E. Juanes, 0. Sedano, R. Rodriguez-Ubis, J.-C. Lanthanide complexes of polycarboxylate-bearing dipyrazolylpyridine ligands with near-unity luminescence quantum yields the effect of pyridine substitution. Photochem. Photobiol. Sci. 2002, 1, 613-618. 

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