What is C9H7BF2N2

BODIPY - BO Microscopii

Chemical parent compound of BODYPY fluorescent dyes
Samples of halogenated BODIPY dyes in ambient lighting and fluorescence under UV

BODIPY is the technical common name of a chemical compound with the formula C.
9H
7BN
2F.
2whose molecule is from a boron difluoride group BF
2consists, which is attached to a dipyrromethene group C

The compound itself was not isolated until 2009, but many derivatives - formally obtained by replacing one or more hydrogen atoms with other functional groups - have been known since 1968 and comprise the important class of BODIPY dyes . These organoboron compounds have attracted great interest as fluorescent dyes and markers in biological research.

structure

In its crystalline solid form, the core BODIPY is almost, but not entirely, planar and symmetrical; with the exception of the two fluorine atoms, which lie on the vertical bisecting plane. Its bond can be explained by the assumption of a formal negative charge on the boron atom and a formal positive charge on one of the nitrogen atoms.

synthesis

BODIPY and its derivatives can be obtained by reacting the corresponding 2,2'-dipyrromethene derivatives with boron trifluoride - diethyl ether complex (BF183 · (CO) in the presence of triethylamine or 1,8-diazabicyclo [5.4.0] undec-7- en (DBU) The difficulty of the synthesis was due to the instability of the common dipyrromethene precursor instead of BODIPY itself.

The dipyrromethene precursors are accessed from a suitable pyrrole derivative by several methods. Usually one of the alpha positions in the pyrroles used is substituted and the other is free. The condensation of such a pyrrole, which is often available from the Knorr pyrrole synthesis, with an aromatic aldehyde in the presence of TFA gives dipyrromethane. which using a quinone oxidizer such as DDQ or p-chloranil.

is oxidized to dipyrromethene. Alternatively, dipyrromethenes are prepared by treating a pyrrole with an activated carboxylic acid, the derivative, usually an acyl chloride. Unsymmetrical dipyrromethenes can be obtained by condensing pyrroles with 2-acyl pyrroles. Intermediate dipyrromethanes can be isolated and purified, but the isolation of dipyrromethenes is usually compromised by their instability.

Derivatives

IUPAC atom numbering for substitutions on the BODIPY core. Positions 3 and 5 are usually also referred to as "α". 1,2,6,7 are called "β"; and 8 means "meso". Note that the numbering does not match the numbering on the parent 2,2'-dipyrromethene molecule.
Molecular structure of 1,3,5,7-tetramethyl-8-phenyl-substituted BODIPY.

The BODIPY core has a rich derivative chemistry due to the high tolerance of substitution in the starting materials for pyrrole and aldehyde (or acyl chloride).

Hydrogen atoms at positions 2 and 6 of the cyclic nucleus can be replaced with halogen atoms using succinimide Reagents such as NCS, NBS and NIS - allows further post-functionalization through palladium coupling reactions with boronate esters, tin reagents, etc.

The two fluorine atoms on the boron atom can be replaced during or after the synthesis by other strong nucleophilic reagents such as lithiated alkyne or aryl species, chlorine, methoxy or a divalent "belt". The reaction is supported by BBr 3 or SnCl 4.

fluorescence

BODIPY catalyzes, and many of its derivatives have recently received attention because they are fluorescent dyes with unique properties. They absorb UV radiation strongly and emit it in very narrow frequency ranges with high quantum yields, mostly at wavelengths below 600 nm. They are relatively insensitive to the polarity and pH of their environment and relatively stable to physiological conditions. Small modifications of their structures enable their fluorescence properties to be adjusted. BODIPY dyes are relatively chemically inert. The fluorescence is quenched in a solution, which limits the application. This problem was solved by synthesizing asymmetric boron complexes and replacing the fluorine groups with phenyl groups.

The unsubstituted BODIPY has a broad absorption band from around 420 to 520 nm (peak at 503 nm) and a broad emission band from around 480 to 580 nm (peak at 512 nm). with a fluorescence lifetime of 7.2 98 ns 112. Its fluorescence quantum yield is close to 1, greater than that of substituted BODIPY dyes and comparable to that of rhodamine and, but the fluorescence is lost above 50 ° C.

BODIPY dyes are notable for their uniquely small Stokes shift, high, environmentally independent fluorescence quantum yields that often approach 100% even in water, sharp excitation and emission peaks that contribute to the overall brightness, and high solubility in many organic solvents. The combination of these properties makes BODIPY fluorophores very promising for imaging applications. The position of the absorption and emission bands remains almost unchanged in solvents of different polarity as a dipole moment and is orthogonal to one another.

Possible applications

BODIPY conjugates are often investigated as potential sensors and for labeling using their highly adjustable optoelectronic properties.

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