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According to the (1)H, (13)C and (15)N NMR spectroscopic data and DFT calculations, the E-isomer of 1-vinylpyrrole-2-carbaldehyde adopts preferable conformation with the anti-orientation of the vinyl group relative to the carbaldehyde oxime group and with the syn-arrangement of the carbaldehyde oxime group with reference to the pyrrole ring. This conformation is stabilized by the C-H...N intramolecular hydrogen bond between the alpha-hydrogen of the vinyl group and the oxime group nitrogen, which causes a pronounced high-frequency shift of the alpha-hydrogen signal in (1)H NMR (approximately 0.5 ppm) and an increase in the corresponding one-bond (13)C-(1)H coupling constant (ca 4 Hz). In the Z-isomer, the carbaldehyde oxime group turns to the anti-position with respect to the pyrrole ring. The C-H...O intramolecular hydrogen bond between the H-3 hydrogen of the pyrrole ring and the oxime group oxygen is realized in this case. Due to such hydrogen bonding, the H-3 hydrogen resonance is shifted to a higher frequency by about 1 ppm and the one-bond (13)C-(1)H coupling constant for this proton increases by approximately 5 Hz.

A general efficient route to hitherto inaccessible symmetric and asymmetric meso-CF(3)-BODIPY dyes has been developed. The key stages include the reduction of available 2-trifluoroacetylpyrroles to the corresponding alcohols which are further condensed with pyrroles. The method allows the BODIPY with 3(5)aryl(hetaryl) and 3,5-diaryl(hetaryl) substituents to be readily assembled. The BODIPY dyes synthesized fluoresce (Φ(f) = 0.56-1.00) in the 560-680 nm region.