BODIPY dyes transfer

The optical properties of organic dyes (Fig. ld-f, Table 1) are controlled by the nature of the electronic transition(s) involved [4], The emission occurs either from an electronic state delocalized over the whole chromophore (the corresponding fluorophores are termed here as resonant or mesomeric dyes) or from a charge transfer (CT) state formed via intramolecular charge transfer (ICT) from the initially excited electronic state (the corresponding fluorophores are referred to as CT dyes) [4], Bioanalytically relevant fluorophores like fluoresceins, rhodamines, most 4,4 -difluoro-4-bora-3a,4a-diaza-s-indacenes (BODIPY dyes), and cyanines (symmetric... 

BODIPY dyes were subjected to modifications in their meso position as the previous fluorescein dyes. Aromatic moieties at this position are perpendicular to the molecular plane but, nevertheless, affect the fluorescence properties of the core [99]. Subtle manipulation of the redox potential can be also read out by changes of the fluorescence lifetime as exemplified in a substrate for phosphoester cleavage [100]. Depending on of the redox properties of the substituents, fluorescence can be turned on and off [101]. When the electrochemical potential of the substituent is altered during a reaction, a fluorogenic probe for this particular reaction is tailored. This was exploited for studying interfacial electron transfer [61]. More applications appear feasible. 

An epoch-making discovery in heterofulvene chemistry was the metallic conductivity in the charge-transfer complex formed from tetrathiafulvalene (TTF) 24 and tetracyanoquinodimethane (TCNQ) 25 in 1973 [12]. Upon this discovery, various functional dyes have been designed and constructed on the basis of electronic character of TTF however, this chapter only describes the functional dyes involving a fulvene moiety, because TTF chemistry is considerably larger (see Chapter 8) and many good books and reviews have already been published to date [13]. For the same reason, this chapter does not refer to the chemistry of porphyrins 26 and boron dipyrromethenes (BODIPY) 27, although they formally possess azafulvene moieties in their n-systems [14, 15]. 

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