Quantum-chemical methods poly

Recent publications calculate the basicity of aromatic compounds and the electronic structure of the respective arenium ions by quantum chemical methods in different approximations — by semi-empirical methods MO LCAO (methylbenzenes " ), CNDO, CNDO/2 and CNDO/2FK (benzene " , toluene and other monoalkylbenzenes " , anisole , a series of monosubstituted benzoles , poly-methylbenzenes , monomethylnaphthalenes and polycyclic aromatic hydrocarbons ) INDO (benzene , cresols ) MINDO-2 and MINDO-3 (benzene , toluene ) by nonempirical (ab initio) methods using the basis... 

NMR chemical shift prediction by quantum chemical calculation and the 7-gauche effect method has become a useful approach for stereochemical assignment of vinyl polymers. Recently C NMR assignments based on 7-effect and the rotational isomeric model were demonstrated successfully for a series of polyolefins, poly(l-pentene) to poly(l-octene).188... 

Poly(/7-phenylenevinylene) may be considered a regular copolymer of acetylene and benzene [128]. Electron structures of PA, poly(p-phenylene), and poly(p-phenylenevinylene) were studied by using UV photoelectron spectroscopy and quantum chemical calculations based on the valence effective Hamiltonian method. Excellent agreement between the theory and experiment allows a detailed description of the evolution of the electron structure in this polymer series. 

Moreover, the configurational splitting in solution may be simulated as well. Quantum chemical calculations can thus provide a justification for the empirical y-gawc/ze method which uses a simple increment system to predict the chemical shift. In some systems (e.g. poly (methyl methacrylate)), where a breakdown of the empirical method is experienced, quantum chemistry may successfully predict the splitting as it does not rely on special assumptions. For routine analysis, the higher resolution and the much lower computation time favor the traditional phenomenological approach. In these cases, quantum-chemistry based simulations should be regarded as a complement rather than a replacement. 

Methods. Absorption spectra were measured on Specord UV/VIS spectrophotometer (Zeiss, Jena). Circular dichroism (CD) spectra were recorded on Mark III Dichrographe (ISA Jobin Yvon). Quantum chemical calculations were performed with the programme POLY (Skala (1981)), using the porphyrine atom coordinates from Maggiora et al.(1978). 

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