Phenanthrene geometry

Rigid diphosphines have been used to enforce n-ans-geometries thus with the phenanthrene-derived diphosphine (Figure 3.49, R = Et) the complexes PdLCb and PtLCl2 have closely similar geometries (Pd-P 2.307 A, Pd-Cl 2.306 A, P-Pd-P 177.4° Pt-P 2.293 A, Pt-Cl 2.304 A, P-Pt-P 177.1°)... 

The second example concerns heptahehcene. Figure 4.17 shows the structure of left-handed M-heptahelicene, where M stands for minus. On Cu(lll) surfaces the M-heptahelicene molecules are found to adsorb in a geometry with their terminal phenanthrene group (the first three carbon rings) oriented parallel to the (111) faces and to successively spiral away from the surface from the fourth ring on, as determined by X-ray photoelectron diffraction experiments (Fasel et al, 2001). 

Phosphorescence studies in isobutylene-methyl methacrylate-1-naphthyl-methyl methacrylate co-polymer provided evidence to show that in very dilute solution the chain collapses into more compact structures, and intramolecular excimer formation in poly-(2-vinylnaphthalene) has been shown to exhibit non-Stokes-Einstein behaviour. Laser photolysis of polymers containing phenanthryl groups, such as poly-(9-vinylphenanthrene), indicates the presence of plural dimer sites having different geometries owing to the stacking effect of phenanthrene chromophores. In poly-(2-naphthyl methacrylate). 

Figure 6 Schematic representation of the displacement vectors corresponding to the nontotally symmetric postdiagonalization nuclear distortions that show the most marked anti-GMPP character of phenanthrene and pentacene obtained at the HF/6-31G level. The depicted displacement vectors of the non-hydrogen atoms have been multiplied by two in the representation for seek of clarity. The numbers inside the molecular rings are the NICS values of these rings calculated at the HF/6-31+G(d) level with the HF/6-31G optimized geometry...

Fluorescence quenchinfi. 277-78. 283 benzene, 265 diazabicyclooctene. 292 lO-methyiacridinium ion. 300-1 Flaorescencc speclrum. anthracene. 263 anthracene + dimclhylaniltne. 282 azulene, 273-74 perylene, 261-62 phenanthrene. 273-75 porphine. 268-69 pyrene, 280-81 Iriphenylene. 274. 276 Formaldehyde, excited stale geometry, 45. 120. 186... 

Figure I. EN (E), GEO (G) and HOMA (H) values for benzene, naphthalene, phenanthrene, and triphenylene ealeulated from experimental geometry, aecording to Ref 17.

Two different values of REC for particular rings of benzene and phenanthrene result from different measurements of their molecular geometry. The different REC values for symmetrically equivalent rings in other benzenoid hydrocarbons result from the method of X-ray structure determination. If the symmetrical molecule does not lie at the symmetry element in the crystal lattice, each of the rings is measured independently and its geometry (and in turn its REC value) is biased by the another error of measurement. The differences in REC values for symmetrically equivalent... 

The molecule of 15,23 16,22-dimethenobenzo[l,2-iZ 4,5-fl ]dipentha-phene (C48H24, Figure 2), also known as kekulene or superbenzene, was studied at both the HF/STO-3G and HF/6-31G levels. The optimized geometry was found to be planar and have D f, symmetry, with the six inner hydrogen atoms separated by only 1.851 A. In addition, structures of five other ben-zenoid hydrocarbons (anthracene, phenanthrene, tetracene, benzanthracene, and chrysene) were optimized. The corresponding total energies were found to... 

In the phenanthrene-antimony trichloride complex, the Sb atom can be considered to have trigonal-bipyramidal geometry if the lone pairs are included. One lone pair appears to be interacting with the ir-systen on one phenyl ring of the phenanthrene molecule and the other forms an association with a chlorine atom of a neighbouring SbCla molecule (Figure 13). 

Chapter 5 treats extension of the method to alkenes, alkynes and aromatic compounds by generalizing the force constant matrix. The relationship between bond orders and molecular geometry in conjugated systems is discussed along with VESCF inclusion in MM4. The valence bond description of molecular structure is discussed with special regard to MM4 results for phenanthrene, corranulene, and the C 60 fullerenes along with a general review of aromaticity and electronic spectra. 

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