Pyrene, complexes

Dabrowski, M.J., Schrag, M.L., Wienkers, L.C. and Atkins, W.M. (2002) Pyrene-pyrene complexes at the active site of cytochrome P450 3 A4 evidence for a multiple substrate binding site. Journal of the American Chemical Society, 124 (40), 11866-11867. 

From other planar structures which have been studied, specifically planar complexes such as the tetramethyluric acid-pyrene complex, it is known that the molecules tend to stack plane to plane at a distance of about 3.4 A. (6). One unit cell dimension in this case is 6.99 A. Thus, it would be reasonable to expect the caffeine and pyrogallol molecules to be stacked with their planes roughly perpendicular to this short axis, and it would be likely that a projection of the caffeine-pyrogallol complex down this axis to the x,y plane would result in a two-dimensional picture of the complex with a small amount of distortion owing to the tilt of the planes of the molecules with respect to the x,y plane. 

A Cu(II)-induced perturbation of pyrene fluorescence has been utilized to create a sensor for glutamate [388], A 2 2 1 Cu2+ 3-CD pyrene complex is formed by the noncovalent assembly of the constituents the site of Cu(II) binding is unknown. The pyrene emission resulting from complexation of the lu-mophore to 3-CD is effectively quenched by the addition of Cu(II). A 500-fold enhancement in pyrene intensity is observed upon the addition of 1.87 M glutamate, which is presumed to extract Cu(II) from the 2 2 1 complex. The precise nature of the quenching and restoration mechanisms is currently unknown. 

In a mixture containing a 2 1 molar ratio of 1 and II the NDI proton signal of 1 and all the protons of II are shifted upheld by 0.09 and 0.08 ppm, respectively, while in a similar mixture containing 1-ester and II the same protons are shifted upheld by only 0.04 ppm (Fig. 37). This behaviour is consistent with the formation of an inclusion complex between 1 and II, where the pyrene molecules are shielded by the naphthalene aromatic cores of the NDIs, which in turn are shielded by the pyrenes complexed inside the nanotube. Spectrum d in Fig. 37 shows that, although there is some... 

Table I shows the effect of various systems such as micelles, swollen micelles (achieved by adding hexanol to CTAB), microemulsion systems, vesicles formed from a double-chain CTAB surfactant, and reversed micelles with water cores formed with benzyl dimethylcetylammonium bromide in benzene. Hie active chromophore exists either as pyrene, pyrene sulfonic acid or pyrene tetrasulfonlc acid. Essentially the concept here is that the polar derivatives of pyrene will always locate pyrene at the surface of the micelle as these anionic species of pyrene complex with the positively charged surface. Dimethylaniline is used as an electron donor in each case, it can be seen that for pyrene, a continual decrease in the yield of the pyrene anion (ion yield of unity in the micelle) is observed on going from micelle to swollen micelle, to microemulsion, and no yield of ions is observed in a reversed micelle system. With pyrene tetrasulfonic acid the yield of ions over the different systems is fairly constant, even across to the reverse micellar system. However, the lifetime of the ions is extremely short in the reversed micellar system. An explanation for such behavior can be given as follows as we transverse across the...

The excimer-like fluorescence of the y-CD-pyrene complex with stoichiometry 1 2 shows an extremely intense circular polarization [104,105], 0em = 1-2 X 10 the same phenomenon was observed for 1-ethylpyrene (14). It was concluded that pyrene molecules in the y-CD cavity form the excimer with an asymmetrical twisted configuration the formation of the achiral, symmetric, sandwich-type pyrene excimer present in bulk solutions is probably hampered by the sterically restricted environment. The S-helicity of the two 13 molecules included in y-CD is in agreement with the induced circular dichroism spectra [106]. 

The fluorescence of naphthalene complexed with P-CD and of pyrene complexed with P- and y-CD was quenched by I". The quenching was greatly reduced by 1 % (v/v) benzyl alcohol added to the / -CD-naphthalene complex or by 1 % tert-butyl alcohol added to the complexes of P- or y-CD with pyrene [117]. 

T. Z. M. Denti, W. F. van Gunsteren, and F. Diederich,/. Am. Chem. Soc., 118,6044 (1996). Computer Simulations of the Solvent Dependence of Apolar Association Strength Gibbs Free Energy Calculations on a Cyclophane-Pyrene Complex in Water and Chloroform. 

Fig. 16. Polarographic data for complex formation as a function of donor concentration (in CHaCls at 25°). Hexamethylbenzene complexes of A, tetracyanoethylene B, tetra-cyanobenzene. Pyrene complexes of C, chloranil D, tetracyanobenzene E, tetracyano-quinondimethide. (Data from ref. 64)...

The phenanthrene-SbCl3 complex contains trinuclear aggregates with intermolecular distances Sb- -Cl 3.410 and 3.260 A [415]. In the pyrene complex the SbCls molecules (Sb-Cl 2.346 2.38.8 A) are coordinated on both sides of the arene and are further connected by secondary Sb- -Cl (3.515, 3.652, and 4.000 A) bonds to form inorganic layers with the organic molecules sandwiched between them. Structurally characterized complexes 2,2 -dithienyl-2SbCl3 (Sb-Cl 2.356-2.374 A, Sb- - -Cl 3.552-3.761 A) and benzo[i>]thiophene-2SbCl3 (Sb-Cl 2.352-2.367 A, Sb- - -Cl 3.546-3.847 A) show that aromatic heterocycles can behave similarly [419]. 

Anigbogu et al. [158] studied the effects of methanol, r-butyl alcohol (TBA), and cyclopentanol (CP) on anthracene and pyrene retention on a C)8 column (A = 255 nm) using 50% to 70% methanol in water containing 3 mM ) -cyclodextrin and 1% TBA or CP. On the basis of retention effects, the authors speculate that TBA and CP assist in the formation of a cyclodextrin/pyrene complex and conclude that TBA and CP may be effectively used as mobile phase modifiers in these fiised-ring systems. Schuette and Warner [159] conducted a similar study on the effects of N pentanol on or y-cyclodextrin/PAH complexes. A solution of 0.1 M 1-pentanol with 5mM y- or j -cyclodextrin increased the fluorescence emission intensity markedly in Ihe 430-490 nm range. Chromatographic selectivity and efficiency were enhanced and the detection limits were lowered by nearly an order of magnitude. 

C2SH22N11O3, 1, 3,7,9-Tetramethyluric acid-pyrene complex, SOB, 253 C25H23N3O7, 2,4,7-Trinitrofluorenone - hexamethylbenzene, 40B, 568 C25H29Ni OioPf Procatine - bis-p-nitrophenyl phosphate, 35B, 416... 

Figure 4. Schematic drawing of the highly favored geometry of the 7-pyrene complex in aqueous solution.

The 1 1 (guest CD) stoichiometry is the most common type of CD complexes. Complexes of other stoichiometries such as 1 2, 2 1, 2 2, 1 1 1, and 1 1 2 are also frequently observed. Even for a given guest-CD pair, complexes of different stoichiometries can be formed. Examples of this are naphthalene and pyrene complexes of CD, which were studied extensively by fluorescence techniques [10-12]. Schematic representation of various types of CD complexes is shown in Fig. 1. 

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