The synthesis and characterization of a new type of chromophore, namely PePc consisting of a central phthalocyanine core and four fused perylene-bisimide (PBI) units is described for the first time. The entire architecture represents a highly extended conjugated heterocyclic pi-system with C-4h symmetry. In order to guarantee pronounced solubility in organic solvents the corresponding PBI units were bay-functionalized with tert-butylphenoxy substituents. Next to the metal-free macrocycle, PePcH(2), also metallated macrocycles PePcM (M=Zn, Ni, Pb, Ru, Fe) were synthesized. The extensive fusion of the corresponding aromatic building blocks to the very large extended p-system leads to a very narrow HOMO-LUMO gap and as a consequence to transparency in the visible but light absorption in the NIR region. Significantly, the azomethine N-atoms N1-N4 of PePcM and PePcH(2) are highly basic. The corresponding tetraprotonated systems can only be deprotonated with very strong non-nucleophilic bases such as phosphazene bases. In the protonated forms PePcMH(4)(4+) and PePcMH(6)(4+) the absorption maximum is shifted back to the visible region due to the loss of conjugation. The experimental findings were corroborated with quantum mechanical calculations.
展开▼
