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There is great interest in the investigation of heterodimers formed by metalloporphyrins and metallophthalocyanines grafted with oppositely charged substituents, since these systems are models of the photosynthetic special pair and promising unidirectional electron transfer molecular devices. In the present study new cationic metalloporphyrin derivatives were synthesized and their association with anionic metallophthalocyanines forming heteroaggregates, investigated. These new cationic porphyrins derivatives show benzylic groups bound to the pyridyl nitrogen atoms of tetra-(pyridyl)porphyrin (TPyP), resulting in additional p systems and more hydrophobic compounds if compared with tetra-(methylpiridinium)porphyrin (H2TMPyP) and tetra-(trimethylaminophenyl)porphyrin (H2TAPP) ligands. It could be observed that both stoichiometry and association constants between cationic porphyrins and anionic phthalocyanines depend on the metal complexed to the macrocycles. Zn(II)porphyrins form preferentially aggregates of 1:1 stoichiometry (porphyrin:phthalocyanine), but when the porphyrin is coordinated to Pd(II) 1:1 and 1:2 (porphyrin:phthalocyanine) aggregates are present in solution. The K PI values are always higher for the heterodimers ZnPorphyrin/CuPhthalocyanine; this behavior is related to the less pronounced out-of-plane distortion of Cu-N compared to Ni-N binding, as a result of axial ligation of a DMSO molecule to the metal ion inserted into the macrocycle core. The K PI values are lower for the heterodimers containing the porphyrins that present the larger benzylic meso-substituent, due to the steric hindrance caused by these groups. These results show that many structural features can control the association between tetrapyrrolic macrocycles. Not only the association can be modulated by these structural factors, but also different photophysical properties should be displayed by these aggregates, and studies in this direction are under way.

Six new dendrimers constructed around a (Ru(bpy)3)2+-type core (bpy = 2,2'-bipyridine) and having up to 24 4'-tert-butylphenyloxy or 48 benzyl units in the periphery were synthesized. The metallodendrimers were produced by complexation of ruthenium trichloride with bipyridine ligands with dendritic wedges in the 4,4'-positions. All of them exhibited the characteristic luminescence of the (Ru(bpy)3)2+-type core unit. The dendritic branches protect the luminescent excited state of the core by dioxygen quenching.

The quantum chemical calculations and resonance Raman spectroscopy are used for examining the chromophore delocalization in 4-hydroxy-4'-nitroazobenzene as well as in its deprotonated species. The results have shown considerable charge redistribution in the parent molecule after deprotonation, as shown by the red shift of the electronic transition and the change in the extension of the chromophore delocalization.