Charge transfer complexes luminescent spectra

Phosphorescence Spectra.—Luminescence from a low-lying triplet state of water368 has been reported. It has been shown that two long-lived emission systems in the biacetyl crystal described previously by Sidman and McClure (see ref. 368) are in fact due to impurities, and a complete analysis is presented of the true 3AU xAg phosphorescence. The zero-zero band in emission is found at 20 327 cm-1.135 A satisfactory account of the six characteristic bands in the phosphorescence spectrum of benzene has been given on the basis of pseudo-Jahn-Teller vibronic interactions between the lower 3Blu and 3Elu states in which two active vibrations in the pseudo-cylindrical approximation are considered.369 The phosphorescence spectra of anthracene,3700 coronene,8706 benzophenone in aqueous solution,371 pyrimidine derivatives,372 porphyrins,298 873 and crystalline charge-transfer complexes 374 have been reported. 

Morana et al. investigated the effect of ODT on the formation of the charge transfer complex (CTC) for C-PCPDTBT and Si-PCPDTBT [91]. Despite the pristine C-PCPDTBT, no changes were observed in the absorption spectrum of the Si-PCPDTBT films prepared with ODT. Enhanced phase segregation in the C-PCPDTBT films upon addition of ODT caused increase in the molecular luminescence to CT luminescence ratio. This is due to the reduced concentration of CT complexes by a decrease in the contact area between the polymer and the fullerene because of phase separation. 

As regards the optical properties of this complex, the absorption spectrum in chloroform solution revealed absorption maxima at 290 (e = 2.5 x 103) and 204 nm (e = 7.7 x 103). These values were similar to those found in [Au3(CH3N=COCH3)3] and were likely due to metal-to-ligand charge transfer. It was luminescent at room temperature in the solid state showing an intense band at 404 nm and shoulders at 525 and 793 nm, the third with a very low intensity. The complexity of this pattern was... 

Electronic transitions in the absorption spectra of Pt(II) complexes include ligand-field (LF) and charge-transfer (CT) bands and perhaps 5d-6p transitions e.g., the absorption spectrum of aq [PtCl ] displays well-separated LF and CT transitions with a maximum at 480 nm (molar absorbtivity, e = 15 M cm ) assigned to a triplet LF absorption, two maxima at 394 nm (e = 57) and 337 nm (e = 62) assigned to singlet LF absorption, and intense bands 200-250 nm (e > 10 ) to LMCT transitions ". The luminescence of K lPtCl ] in ice occurs from the lowest LF-triplet state, and the molecular geometry of this excited state (ES) may be (distorted T j) rather than D41, (square planar), which is particularly relevant to the photochemistry of Pt(II) complexes. 

Luminescent coordination compounds continue to attract considerable attention. Zink recently reported a new mixed-ligand copper(I) polymer that shows interesting photoluminescence (232). The complex [CuCl(L44)Ph3P] consists of a one-dimensional chain lattice of metal ions bridged by both Cl" ions and pyrazine molecules. The compound shows conductivity of less than 10-8 S cm 1. The absorption spectrum of the complex shows a band at 495 nm, which could be interpreted as the promotion of an electron from the valence band to the conduction band. On the basis of resonance Raman spectra, the lowest excited state in the polymer is assigned to the Cu(I)-to-pyrazine metal-to-ligand charge-transfer excited state. 

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