C-H...F hydrogen bonding: the origin of the self-assemblies of bis(2,2'-difluoro-1,3,2-dioxaborine).

The effect of the molecular structure on the self-assembly of specially designed two-core 1,3,2-dioxaborines has been studied with various techniques. It was found that the molecules spontaneously adsorbed on HOPG surfaces and self-organized into well-ordered two-dimensional (2D) monolayers. The structural details of the 2D assemblies were investigated by scanning tunneling microscopy (STM). From X-ray analysis of the corresponding three-dimensional (3D) crystal and from theoretical calculation, we were able to reveal the driving force behind the specific self-assembly. The C-H...F hydrogen bonding between the ortho carbon of the phenyl ring and the fluorine of the BF2 group plays an important role in the formation of the adlayers. The different electron affinities and geometries of the molecules affect the intermolecular interactions which further lead to different properties in the bulk materials.

Radical ions of alpha,alpha'-bis(diphenylamino)-capped oligothiophenes: a combined spectroelectrochemical and theoretical study.

A new homologous series of alpha,alpha'-bis(diphenylamino)-capped oligothiophenes, prepared by a palladium-catalyzed coupling reaction of stannylated 2-diphenylaminothiophenes with 2-mono- or 2,5-dibromothiophenes and their homologues, was studied by in situ ESR/UV-vis/NIR spectroelectrochemistry. In general, the oxidation potentials of these oligothiophenes were found to be proportional to the inverse number of thiophene units. However, the potential slope of the first oxidation is completely different from that of higher oxidation steps. Trication radicals were identified by electron spin resonance (ESR) for higher thiophene homologues in addition to monocation radicals (polarons). According to the ESR hyperfine structures, the unpaired electron is delocalized in the conjugated system. In contrast to the parent alpha,alpha'-bis(diphenylamino)-capped oligothiophenes, the UV-vis/NIR absorption maxima of the oxidized species strongly depend on the number of thiophene units. Spin-restricted and spin-unrestricted Kohn-Sham density functional calculations were used to explain and to understand these properties. Absorption wavelength and intensities were calculated by the time-dependent density functional response theory. Unrestricted density functional calculations of oligothiophene dications (bipolarons) with five or more thiophene rings result in spin-broken structures which may be considered as two-polaron biradicals (polaron pairs).

Thiophene-thiophene versus phenyl-phenyl coupling in 2-(Diphenylamino)-Thiophenes: an ESR-UV/Vis/NIR spectroelectrochemical study.

The oxidation of several 2-diphenylamino-substituted thiophenes and N,N'-bis(2-diphenylamino-5-thienyl)-substituted phenylene-1,4-diamines with different substitution patterns in the 5-position of their thiophene moieties was studied by cyclovoltammetric and spectroelectrochemical measurements (ESR, UV/Vis/NIR). These measurements revealed both the structure of the oxidation products obtained and that of their cationic intermediates, as well as the pathway of their formation and follow-up reactions. Thus, the formation of the radical cations in the first electrochemical oxidation step of the target molecules was demonstrated. Depending on the substitution pattern, these radical cations give rise to several consecutive processes to a different extent. Thus radical dimers, dehydrodimers with a 2,2-bithiophene, 3,3'-bithiophene, or benzidine structure, as well as radical monocationic and dicationic products can be formed. For N,N'-bis(2-diphenylamino-5-thienyl)-substituted phenylene-1,4-diamines rather stable radical cations and dications were primarily formed and unambiguously identified. These species were transformed into 2,2'-bithiophene dimers and oligomers when the 5-position of the thiophene moiety was unsubstituted. By in situ spectroelectrochemistry the influence of the substituents on the type of coupling reactions can be demonstrated and followed in detail.

Radiation exposure to patients undergoing percutaneous coronary interventions: are current reference values too high?

PURPOSE: To determine predictors of patient radiation exposure due to percutaneous coronary interventions (PCI) and to compare our results with the "preliminary reference levels", recently proposed by the European DIMOND research cardiology group: i. e., 75 Gy.cm(2) for dose area kerma product (DAP), 17 min for fluoroscopy time (T(F)), and 1,300 for cinegraphic frames (F). MATERIAL AND METHODS: For 642 PCI-exclusive of the fraction for diagnostic catheterization to avoid statistical confounder effects-we measured total DAP, cinegraphic (DAP(C)) and fluoroscopic (DAP(F)) fractions, the number of cinegraphic frames and runs, and T(F). DAP(C)/F and DAP(F)/s were calculated to indicate the quality of focusing to the region of interest. RESULTS: The mean total patient DAP for elective one-, two-, and three-vessel PCI amounted to 6.7, 11.6, and 19.4 Gy.cm(2), for PCI of focal in-stent restenoses to 4.2 Gy.cm(2), and for excimer laser angioplasty of diffuse in-stent restenoses to 19.4 Gy.cm(2), respectively. Recanalization of chronic occlusions and PCI in acute myocardial infarction occasioned mean levels of 16.0 and 17.3 Gy.cm(2). Implantation of one and > or = two stents during one-vessel PCI significantly increased total mean DAP from a baseline level of 5.7 up to 7.1 and to 13.8 Gy.cm(2). DAP significantly varied according to the various PCI target regions and amounted to 4.0, 4.5, and 5.5 Gy.cm(2) for intermedius, diagonal, and left anterior descending arteries, to 4.9, 5.0, and 7.0 Gy.cm(2) for obtuse marginal, left posterolateral, and circumflex arteries, to 8.3, 9.1, and 9.5 Gy.cm(2) for proximal/mid right coronary segments, posterior descending, and right posterolateral arteries, and to 11.6 Gy.cm(2) for saphenous vein grafts, respectively. CONCLUSION: This study, carried through by consistent use of radiation-reducing techniques, enables a reliable scoring of patient radiation exposure according to complexity and target vessel of the intended PCI. Our 95th percentiles for elective PCI, for recanalizations of chronic occlusions, and for emergency PCI advise reference levels of 22, 32, and 42 Gy.cm(2) for DAP, of 16, 25, and 24 min for T(F), and of 400, 600, and 700 cinegraphic frames, respectively.

Preparation and characterization of 2-amino-5-thienyl-substituted multicharged methinium compounds.

[reaction: see text] A series of new 2-amino-5-thienyl-substituted multicharged methinium compounds have been prepared and characterized spectroscopically and electrochemically by reaction of lithiated species of N,N-disubstituted 2-aminothiophenes with alkyl derivatives of di- and tricarbonic acids and subsequent addition of perchloric acid.

Preparation and characterization of alpha,alpha'-bisdiarylamino-capped oligothiophenes.

[reaction: see text] A series of alpha,alpha'-bisdiarylamino-capped oligothiophenes C(n) were prepared by the palladium-catalyzed reaction of the dibromo compounds A(i) with diarylamines, N,N-diarylamino-substituted thiophenes or 2,2'-bithiophenes BX(j). These easily oxidizable compounds exhibit a high tendency to form amorphous glasses and characteristic electrochemical and spectroscopic properties that depend significantly on the number of their thiophene moieties.