Photophysics complex formation

Complex formation is important in photophysics. Two terms need to be described here first, an exciplex, which is an excited state complex formed between two different kinds of molecules, one that is excited and the other that is in its grown state second, an excimer, which is similar to exciplex except that the complex is formed between like molecules. Here, we will focus on excimer complexes that form between two like polymer chains or within the same polymer chain. Such complexes are often formed between two aromatic structures. Resonance interactions between aromatic structures, such as two phenyl rings in PS, give a weak intermolecular force formed from attractions between the pi-electrons of the two aromatic entities. Excimers involving such aromatic structures give strong fluorescence. 

Solute/solvent 1 1 complexes can be formed, of course, in the ground as well as in excited states. Since solutes that show photochemical internal twisting normally possess polar substituent groups, the probability of complex formation is rather high. Thus, studies of the photophysics of internal twisting must be carried out carefully enough to avoid errors due to complex formation. 

Prodi examined the photophysical properties of supramolecular assemblies containing polypyridine complexes and pyrene chromophores. Using the complex [(bpy)20s(bpy0bpy)]2+ (Scheme 5) and pyrene-1-carboxylic acid, the authors demonstrated that, upon addition of Zn2+, complex formation occurs in which the Zn2+ links together the free bpy of the Os complex and the carboxyl of the pyrene. Excitation of the Os(II) MLCT absorption results in exclusive emission from the 3MLCT state of the Os complex [84]. 

Complex formation is important in photophysics. Two terms need to be described here. First, an exciplex is an excited state complex formed between... 

Noncovalent interaction of dyes and related compormds with various biomacromolecules attracts considerable attention due to the possibility of proceeding of a variety of photochemical processes in vivo [1]. It makes possible to use dyes both in biomedical studies as DNA labels and in clinical practice [2], Complex formation of cyanine dyes with doublehelical DNA is of great interest due to rmique photophysical and photochemical properties of these dyes, which change dramatically in the presence of DNA [1, 3, 4], There are two main types of dye-DNA bonding complexes of dyes intercalated between DNA base pairs and complexes in which dye molecules are located in the minor groove of the double helix of the biopolymer (superficial bonding) [5],... 

The complex formation of bilirubin with human serum albumin was investigated by Sinclair et al. 72) using 347 nm ruby laser flash photolysis technique. A high bilirubin level is found in new bom babies who suffer from jaundice (neonatal hyperbilirubinemia)73). Phototherapy has been found to be suitable for lowering the bilirubin level. In order to understand the mechanism of the phototherapy, investigation into the photophysics of bilirubin is essential. It is strongly bound to human serum albumin, lipids and cell membranes. 

Intense recent research has been devoted to explore not only the local molecular motions but also microstructure in solids by photophysical phenomena, such as non-radiative energy transfer or excited-state complex formation between chromophores. The techniques require the availability of dyes and labels known as microstructural probes. I ,)... 

Functionalization of Ceo with a porphyrin on one side and with a pyridyl ligand on the other side leads to the supramoleciflar triad 39 formed by a covalent-CO ordination approach (Fig. 31a) [18,20,24]. The photophysical properties of this system were studied in detail and show that energy-transfer occurs from the singlet excited state of the free-base porphyrin to the zinc(ll) porphyrin. A charge separated state with formation of the Ceo radical anion and the zinc(II) porphyrin radical cation is produced at an increased efficiency upon complex formation of the array. 

The analysis of excimer and monomer emission in fluid systems is complex. A general kinetic scheme for excimer formation, including the inter- and intramolecular complex formation in terms of a singlet ground and excited states, and the various photophysical processes occurring in polymers, is given in Table 4.1. The three routes of energy... 

Y-P Sun, CE Bunker. Quantitative spectroscopic investigation of enhanced excited state complex formation in supercritical carbon dioxide under near-critical conditions inconsistency between experimental evidence and classical photophysical mechanism. J Phys Chem 99 13778, 1995. 

Luminescence data are summarized in table 12. They may be used to monitor the complex formation, to determine the symmetry of the complex species, the number of bonded water molecules, and the photophysical parameters of the energy transfer from the ligand. 

The discriminatory emission properties between two-coordinate d ° gold(I) complexes and their respective three-coordinate counterparts have been demonstrated in the literature [6, 10-13]. As discussed in the later sections, Che and coworkers have rationalized that the extraordinarily large Stokes shift of the visible emission of [Au2(diphosphine)2] from the [5da 6pa] transition is due to the exciplex formation ofthe excited state with solvent or counterions [6]. Fackler [14—16] reported the photophysical properties of monomeric [AUL3] complexes, which show visible luminescence with large Stokes shifts (typically lOOOOcm ), suggesting significant excited-state distortion. Gray et al. [10] examined the spectroscopic properties of... 

The photophysical properties of magnesium(II) tetra-(i-butyl)phthalocyanine (27) have been studied in solution, in micelles and in liposomes cation radical formation (CBr4 as electron acceptor) has been detected with UV excitation, or by a two-photon excitation using a pulsed laser in the therapeutic window at 670 nm.118 The Mg11 complex of octa(tri-z -propylsilylethy-nyl)tetra[6,7]quinoxalinoporphyrazine (28) has been prepared as a potential PDT sensitizer. The synthesis is shown in Figure 8. Compound (28) has Amax 770 nm (e = 512,000 M-1 cm-1), d>f = 0.46 and d>A = 0.19 (all in THF, under air).119... 

The zinc(II) complexes of meso-tetraphenyltetrabenzoporphyrin (38) and of meso-tetraphenyl-tetranaphthoporphyrin (39) have been prepared 173-175 some photophysical properties of this interesting series are given in Table 11176 Photooxidation of zinc(II) porphyrins causes cleavage of the macrocycle with formation of bilinone derivatives.122 206 207... 

CD-NA rather than by the formation of 1 1 inclusion complexes. It should be noted that addition of the anionic surfactant sodium dodecylsulfate does not induce any photophysical effect. 

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