Lutetium porphyrin complexes

To date, the only organometallic lanthanide porphyrin complexes to be reported contain yttrium and lutetium, and they will be considered in the section on scandium. Representative structural types of porphyrin complexes containing groups 3 and 4 metals are shown in Fig. 3 and selected data for all the structurally characterized complexes are given in Table 11. 

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. 

Most of the lanthanide porphyrin complexes are paramagnetic, except those of lanthanum and lutetium which are diamagnetic. They all show paramagnetic behaviors in the NMR spectra similar to those of the lanthanide 0-diketonate complexes, except that the shift capabilities are less.4 Some of these paramagnetic lanthanide complexes (i.e., that of ytterbium) show Curie behavior at low temperature. Diamagnetic lutetium shows some ring current phenomena.4... 

The first molecular structure of half-sandwich lanthanide porphyrins was reported by Schaverien and Orpen (1991). The lutetium alkyl complex Lu(OEP)[CH(SiMc3)2] has a structure resembling that of the scandium analog (Arnold et al. 1993), exhibiting a square pyramidal geometry. The five-coordinated lutetiiun atom lies 0.918 A above the N4 plane, and the porphyrin ring also displays a saucer shape. 

Coordination compounds composed of tetrapyrrole macrocyclic ligands encompassing a large metal ion in a sandwich-like fashion have been known since 1936 when Linstead and co-workers (67) reported the first synthesis of Sn(IV) bis(phthalocyanine). Numerous homoleptic and heteroleptic sandwich-type or double-decker metal complexes with phthalocyanines (68-70) and porphyrins (71-75) have been studied and structurally characterized. The electrochromic properties of the lanthanide pc sandwich complexes (76) have been investigated and the stable radical bis(phthalocyaninato)lutetium has been found to be the first example of an intrinsic molecular semiconductor (77). In contrast to the wealth of literature describing porphyrin and pc sandwich complexes, re-... 

As shown in Fig. 7.6, texaphyrins have a larger cavity than porphyrins so they can form complexes with lanthanide metals such as gadolinium (XCYTRIN ), that enhances the efficacy of treatment for certain brain tumours, and lutetium (LUTRIN ), used as a sensitizer for photodynamic therapy of recurrent breast cancer [17], Crucial to their success is the increased number of donor atoms available as the more lanthanide binding sites that a ligand can satisfy, the more stable the complex. 

The first monomeric porphyrinato rare earth complex was reported in 1974 [49]. However, only a few reports on these systems have appeared in the literature since then. In 1991, Schaverien and Orpent reported the synthesis of the monomeric porphyrinato lutetium complex Lu(OEP)[CH(Si(CH3)2] from the reaction between Lu CH[Si(CH3)3]2 3 and H2OEP in toluene [50]. Eigure 4.33 displays its molecular structure. The complex belongs to the monoclinic system and crystallizes in a space group P2 lc with a = 1.4879(6) nm, 7 = 2.0644(10) nm, c= 1.4161(5) nm, P= 96.38(3)°, V = 4.323(3) nm, andZ = 4. The coordination geometry can be described as square-pyramidal. In the crystal, the porphyrin... 

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