Calix pyrrole conjugates

The first tetra-TTF calix[4] pyrrole conjugate 170 has been synthesized by the condensation of acetone and the corresponding monopyrrolo-TTF unit. This calix[4]pyrrole in its 1,3-altemate conformation acted as a host for neutral electron-deficient guests such as 1,3,5-trinitrobenzene, tetrafluoro-p-benzoquinone, tetrachloro-p-benzoquinone and p-benzo-quinone. The addition of chloride ions served to effect release of these guests and thus neutral substrate recognition process could be blocked by the addition of chloride anion (2004JA16296). 

In 2002 Sessler et al. designed two cytosine-substituted calix[4]pyrrole conjugates with a cytosine moiety attached either at a p- or meso-pyrrolic position (43 and 44, Fig. 24.18). These hetero-calix[4]arene nucleobase conjugates were tested as nucleotide-selective carriers and as active components of nucleotide-sensing ion-selective electrodes [52]. 

Fig. 24.18 Left cytosine calix[4]pyrrole conjugates with a connection either at the fi- or meso-pyrrolic position (43 and 44) and complex formation of 44 with guanosine monophosphate [52], Right drug delivery vehicle calix[4]pyrrole-/rani -Pt(II) complex (45) and schematic representation of the interaction with adenosine monophosphate as a model compound [53]...

Calix[4]pyrroles offer an alternative receptor site for the recognition of anions. Miyaji et al. [400] prepared a series of calixpyrrole-anthracene receptors that possess conjugated (73) and unconjugated bond pathways of different lengths (74 and 75). The stability constants (103—105 M-1 determined by NMR titration) for the anion complexes of each member of the series follows the trend... 

The calix[4] pyrroles functionalized with nitrobenzenes 5 and 6 [16] can act as F" sensors. These systems bear an appended chromophore directly linked to the calix[4] pyrrole skeleton through a conjugated C=C triple bond. Upon addition of tetrabutylammonium F", solutions of 5 and 6 in CH2C12 turned from pale yellow (Amax=391 nm) to intense yellow (Amax=433 nm) for 5 and from yellow (Amax=441 nm) to red (Amax=498 nm) for 6. In addition, the color changed from yellow (Amax=441 nm) to orange when Cl" (Amax=483 nm) and H2POj (Amax-478 nm) were added to a solution of 6. 

The strapped calix[4]pyrrole-metalloporphyrin conjugate 170 shows strong binding with fluoride ion in organic solvents but no appreciable binding with Gl , Br , or 1 <20040L671, 2005JOC3148>. 

In the conjugate 169, for coupling the anion-receptor ability of the calix[4]pyrrole system to the redox properties of TTF core, one TTF unit has been directly annulated to the upper rim of calix[4]pyrrole. This... 

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