SHELXL also finds a niche for the refinement of macromolecules against high-resolution or twinned data SHELXPRO acts as an interface for macromolecular applications. SHELXL is the most widely used program for small-molecule refinement and SHELXS and SHELXD are often employed for structure solution despite the availability of objectively superior programs. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. Intermolecular quenching was studied with external quenchers TEMPO and oxygen and the data were compared with the intramolecular quenching using 1'-oxo-2',2',6',6'-tetramethyl-4'-piperidinyl-2-(1-pyrenyl)acrylate (PAP-NO.).Īn account is given of the development of the SHELX system of computer programs from SHELX-76 to the present day. Fluorescence of all probes depends on the polarity of solvents and the presence of oxygen. The ester analogues did not show any changes in various pH conditions. This is due to the presence of protolytic equilibria, either in the ground state or in the singlet excited state, leading to the formation of molecular form -COOH and the cationic form -COOH(2) (+). Changes of acidity or basicity of methanol solution resulted in the changes of shape, position as well as the intensity of fluorescence band. The spectrum in neutral methanol indicates that it originates from the anionic form -COO(-). The fluorescence spectrum of PAA strongly depends on the acidity of the solution. Photophysics of these probes were compared with their precursor as 2-(1-pyrenyl)acrylic acid (PAA) and its methyl ester (PAM). HAS was in the form of parent amine (PAP) as well as stable nitroxyl radical form (PAP-NO.). Novel probes represented connection of pyrene as chromophore and sterically hindered amine stabilizers (HAS) in the form of esters of 2-(1-pyrenyl)acrylic acid were synthesized. Electron transfer has been maximized by the compound with a spacer coplanar with the pyrene moiety due to the reduced separation between P3HT and SWCNTs. Photoinduced electron transfer to SWCNTs has been demonstrated and the effect of different alkyl spacers, between the pyrene unit and the thiophene moiety, has revealed to play a key role. In particular, new pyrenyl derivatives of thiophene have been synthesized and used to improve the solubility of SWCNTs for electron transfer in thin film heterojunction with poly(3-hexylthiophene) (P3HT) as donor system. In this contest, we report on a supramolecular approach with the aim of increasing the dispersion of SWCNTs in solution and in organic semiconductor matrices by ensuring the optoelectronic properties. Chemical modification inevitably introduces defects in the nanotube lattice, resulting in a loss of electronic properties. A major problem for the use of single-wall carbon nanotubes (SWCNTs) in electronic devices relates to their poor processability.
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