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Boron Complexes (boron + complex)
Selected AbstractsPhotocycloaddition of Some Difluoro(aminoenonato)boron Complexes with ArylalkenesHELVETICA CHIMICA ACTA, Issue 2 2004Kuniaki Itoh The photocycloaddition of some difluoro[(methylamino- ,N)alkenonato- ,O]boron complexes 1 with arylalkenes 2 is discussed. The resulting [2+2] photoaddition gave the cyclobutane and azetidine derivatives (Schemes,1, 3, and 5). Rearrangements of the cyclobutane gave 1,5-diketones derivatives (Schemes,2, 4, and 5). The yields of the photoadducts were governed by the reduction and oxidation potentials. Furthermore, the configurations of the products established high regio- and stereoselectivity, suggesting the presence of a singlet exciplex. The reactivity and the stereochemistry were rationalized by means of FMO (frontier molecular orbital) calculations. [source] Theoretical investigation on multinuclear NMR chemical shifts of some tris(trifluoromethyl)boron complexesMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2009Jun Zhang Abstract Tris(trifluoromethyl)boron complexes have unusual properties and may find applications in many fields of chemistry, biology, and physics. To gain insight into their NMR properties, the isotropic 11B, 13C, and 19F NMR chemical shifts of a series of tris(trifluoromethyl)boron complexes were systematically studied using the gauge-included atomic orbitals (GIAO) method at the levels of B3LYP/6-31 + G(d,p)//B3LYP/6-31G* and B3LYP/6-311 + G(d,p)//B3LYP/6-311 + G(d,p). Solvent effects were taken into account by polarizable continuum models (PCM). The calculated results were compared with the experimental values. The reason that the structurally inequivalent fluorine atoms in a specific species give a same chemical shift in experimental measurements is attributed to the fast rotation of CF3 group around the BC(F3) bond because of the low energy barrier. The calculated 11B, 13C(F3), and 19F chemical shifts are in good agreement with the experimental measurements, while the deviations of calculated 13C(X, X = O, N) chemical shifts are slightly large. For the latter, the average absolute deviations of the results from B3LYP/6-311 + G(d,p)//B3LYP/6-311 + G(d,p) are smaller than those from B3LYP/6-31 + G(d,p)//B3LYP/6-31G*, and the inclusion of PCM reduces the deviation values. The calculated 19F and 11B chemical shieldings of (CF3)3BCO are greatly dependent on the optimized structures, while the influence of structural parameters on the calculated 13C chemical shieldings is minor. Copyright © 2009 John Wiley & Sons, Ltd. [source] Isothiocyanato Boron Dipyrromethenes,The First BODIPY Analogues of Fluorescein IsothiocyanatePHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2006Nela Malatesti ABSTRACT Two boron complexes of 5-phenyldipyrromethenes bearing isothiocyanate groups on the phenyl ring have been synthesized for the first time. The utility of these new fluorescence probes for labeling biologically relevant proteins is demonstrated on two monoclonal antibodies that bind to antigens overexpressed on cancer cells. Spectral comparison of the two structures reveals significant photophysical differences, including bathochromically shifted excitation and emission bands, increased molar absorptivity and a large increase in fluorescence quantum yield of approximately 10 times. Differences in photophysical parameters are linked to hindered rotation of the phenyl ring in one of the probes. [source] | ||||||||||