Room-temperature phosphorescence spectrum

Figure 2. (a) Room-temperature phosphorescence spectrum of benzo(e)pyrene on 80% a-cyclodextrin-NaCl in the presence of ben2o(a)pyrene. = 284 nm. (h) Room-temperature phosphorescence spectrum of benzo(e)pyrene on 80% a-cyclodextrin—NaCl. X - 284 nm. 

Room temperature phosphorescence (RTP) spectrum and lifetime of BrQBA in NaDC. BrQBA gave a weak fluorescence and no phosphorescence in aqueous solution because of the quenching by dissolved oxygen. However, a strong RTP signal was observed in a NaDC solution without any deoxygenation, with emission at 500 nm. 

Phosphorescence of 3 ( (CHjCN) = 687 nm, E. 42 kcal mol, lifetime 6.5 p.s) was observed using laser excitation. The absorption spectrum of the triplet exhibited maxima at 360 and 570 nm. It was also shown that photoexcited 3 sensitized the formation of singlet oxygen with a quantum yield of 0.65. Rigid binding of indanetrione in a phthahc anhydride matrix was invoked to account for the observation of room-temperature phosphorescence (X, = 713 nm) in a phthahc anhydride matrix no other cases of such room-temperature behavior could be detected in matrices or in solution. 

The synergetic interaction or effect exists widely in various scientific and technical fields. In terms of CD-induced room temperature phosphorescence it can be defined as the principal factor(s) and secondary factor(s) affecting the characteristic properties, e.g., spectrum, quantum yield, lifetime and anisotropy, of the system concerned match automatically with each other to reach an optimization state, and cause remarkable change in the properties. The third or both third and fourth components added to the system interested form ternary or higher inclusion complex together with the CD and phosphore, and they synergetically enhance the stability of triplet states of inclusion complex, leading to increase the phosphorescent intensity or lifetime. 

A wide variety of different mechanisms may participate in the PT process and influence the interpretadon of a spectrum. At room temperature, PL emission is thermally broadened. As the temperature is lowered, features tend to become sharper, and PL is often stronger due to fewer nonradiadve channels. Low temperatures are typically used to study phosphorescence in organic materials or to identify particular impurides in semiconductors. 

Excited-state lifetimes can be measured directly by monitoring the decay of luminescence, but impurities present affect both the lifetime and the luminescence spectrum. Also, because low temperatures are necessary for phosphorescence studies, the excited-state properties determined may differ from those at room temperature. 

Figure 3.2 shows the fluorescence and phosphorescence emission spectrum from tobacco mosaic virus coat protein. These spectra are fairly typical of the tryptophan emission spectra observed from proteins at room temperature. 

Differences between the spectra of fluorescence and phosphorescence are immediately obvious. For all tryptophans in proteins the phosphorescence spectrum, even at room temperature, is structured, while the fluorescence emission is not. (Even at low temperatures the fluorescence emission spectrum is usually not structured. The notable exceptions include a-amylase and aldolase, 26 protease, azurin 27,28 and ribonuclease 7, staphylococcal endonuclease, elastase, tobacco mosaic virus coat protein, and Drosophila alcohol dehydrogenase 12. )... 

Figure 7.28 Phosphorescence spectrum of benzophenone in acetonitrile at room temperature.

Inspection of the data in Table II reveals a bathochromic shift of the of the triplet-triplet absorption with increasing solvent polarity, with a further bathochromic shift when the compound is adsorbed on microcrystalline cellulose. No phosphorescence emission in solution is seen from this compound at room temperature, indicating that the radiative lifetime of this triplet state is long. This is consistent with the lowest energy excited triplet state having predominantly (n, n ) character. The shape of the triplet-triplet absorption spectrum also suggests that this is the case(20). 

The emission displayed in Fig. 12b has been assigned as a phosphorescence (triplet singlet emission) due to the relatively long decay time of 12 ps at 80 K in butyronitrile and of 5 ps at 293 K in acetonitrile. The quantum yield is reported to be as high as 30% at room temperature [53]. The structure in the emission spectrum is assigned to vibrational satellites as will be shown below (Sect. 4.2.4). 

The fluorescence polarization excitation spectrum has been measured for thymine in aqueous solution. " The depolarization at the red edge is attributed to the hidden n, ir transition. Ionization of the lowest excited singlet and triplet states have been determined by the effect of pH on the absorption, fluorescence, and phosphorescence spectra of purines and pyrimidines. " Spectral, polarization, and quantum yield studies of cytidylyl-(3, 5 )-adenosine have also been published. Intermediates in the room-temperature flash photolysis of adenine and some of its derivatives have been identified hydrated electron, radical cations and anions, and neutral radicals resulting from their reactions have been assigned. Photoionization occurs via the triplet state. FMN encapsulated in surfactant-entrapped water pools interacts with polar head groups, entrapped water molecules, and outer apolar solvent. ... 

Figure 8 is the phosphorescence spectrum taken from a glassy solution of poly(n-propyl methyl silylene) in methyl cyclopentane at 89°K. This emission is similar in width to the film emission, as are the solution spectra of the other polymers. Again delayed fluorescence is evident but the sharp vibrational fine structure is lost. The solution and film spectra are not expected to be comparable since they represent conformational equilibria (at room temperature for film and the Tg of 3-methylpentane for the solutions). 

Figure 14. Absorption spectrum (top) and fluorescence excitation spectrum (middle) of isoquinoline vapor at room temperature, and the excitation spectrum of biacetyl phosphorescence (bottom), sensitized by energy transfer from the triplet isoquinoline. The band positions (in cmT1) are relative to the starred 0+ band at 31,925cm-1. (From ref. [45] with permission.)...

Comparisons between these two metals have been carried out on complexes with donor-acceptor Schiff bases. The new species show efficient absorption in the orange-red part of the spectrum and room-temperature near-infrared (NIR) phosphorescence. Particularly, Pt(ii) complexes possess phosphorescence quantum yields (O) of 0.1, but the emission of the respective Pd(ii) complexes is less efficient (OaO.Ol). The Pd(ii) and Pt(ii) complexes are demonstrated to be efficient sensitizers in triplet-triplet annihilation-based upconversion systems. 

The photophysical properties of another trinuclear silver(I) complex [Ag3([i3-dppnt)3] (38a) have also been studied [115]. The complex shows absorption bands at 238 and 367 nm in CH2CI2. The emission spectrum of the complex in CH3CN shows an emission band at 550 nm (T6 = 5.0 ps) at room temperature. The phosphorescent state has been assigned to be ligand-centered in nature. The X-ray crystal structure of the dinuclear gold(I) counterpart shows that a potassium ion is encapsulated in the macrocyclic cavity, forming the complex [Au2K(p3-dppnt)j + (38b) [115]. 

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