Erbium porphyrin complexes

Besides the substances mentioned so far, functionalized fuUerenes like the simple Bingel adduct can be intercalated into nanotubes as well (Section 2.5.5.2). The formation of peapods has further been described for metallocenes (e.g., ferrocene), porphyrines (e.g., erbium phthalocyanine complex) and small fragments of nanotubes. The most important prerequisite for the feasibility of inclusion is always a suitable proportion of sizes of both the tube and the structure to be embedded. For example, this effect can be observed for the intercalation of different cobaltocene derivatives into SWNT. The endohedral functionalization only takes place at an internal diameter of 0.92nm or above (Figure 3.100). But there is also an upper limit to successful incorporation. When the diameter of the nanotube is too large, the embedded species can easily diffuse away again from the host. Only few molecules are consequently found inside such a wide tube. 

Porphyrin complexes of yttrium, lanthanum, cerium, praesodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and thorium can be synthesized using this method. 

Porphyrin molecules form stable complexes with lanthanide ions, these complexes have intensive absorption in a visible range of spectrum. Erbium, ytterbium and neodymium complexes are characterized by a 4f-luminescence in near IR-range of spectrum [1]. The most studied complexes with porphyrins are ytterbium complexes since Yb has smaller ionic radius in comparison with lanthanum (radius of Yb ion is 1.01 A), which determines higher stability of these metallocomplexes. Distinctive feature of Yb porphyrin complexes is a characteristic narrow and rather intensive luminescence band located in the IR-range at 975-985 nm, in so-called therapeutic window of tissue transparency. ... 

Similar crown-eflier-containing porphyrins have been described by Tsukube. In the porphyrins 55a-c, the metal was an erbium cation, serving as the binding site for the free carboxylate of amino acids. Good extraction efficiencies from water to dichloromethane were described with L-Trp, through the formation of a 1 1 complex. Notably, the conjugates with several L-amino acids and dipeptides gave... 

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