Lanthanide sandwich

Double-decker complexes of the smaller elements (Tb-Lu) [237] are available by activated Por-precursors, namely Li2Por [238]. Lanthanide dialkylam-ides should provide an alternative route [239]. Triple-decker complexes are more readily formed compared to the Pc derivatives (Fig. 23). In an effort to force the localization of the unpaired electron on one ring, heteroleptic systems such as Por/Por and Pc/Por lanthanide sandwich complexes have been studied (Table 18 Fig. 23). 

In 2003 a new class of SMMs was reported which contain only a single paramagnetic metal ion. These were the feis-phthalocyanine (H2PC) lanthanide sandwich complexes (Bu4N)[L (Pc)2], where the ion has... 

Lanthanides form phthalocyanines PcMX, sandwich-like complexes of the type Pc2M, and triple-decker complexes of the type Pc3M2. 

In the case of lanthanide elements, other sandwich-like compounds such as the triple-decker phthalocyanincs have been reported. Yttrium(III) acetate hexahydratc when treated with phthalonitrile at 230 C for 8 hours forms a triple-decker phthalocyanine.202... 

Bocian, Lindsey and co-workers studied sandwich complex nanocapacitors comprised of porphyrin and phthalocyanine ligands separated by lanthanide metals [133]. A triple-decker sandwich of phthalocyanine-Eu-phthalocyanine-Eu-porphy-rin, with two phenylethynyl linker wires from the porphyrin, potentially has up to nine accessible oxidation states (—4 to +4). SAMs of monomers, dimers, trimers, and oligomers of this sandwich, anchored at one or both ends by thioacetyl groups, gave charge densities up to 10 10 mol cm-2, electron-transfer rates up to 105 electrons s-1, and charge-dissipation half-lives in the 10-50 s range. 

Porphyrazines with alkyl or aryl substituents are considerably more soluble than their unsubstituted counterparts (Section III. A). Consequently, various pz isomers with alkyl and aryl substituents, for example, symmetrical M[pz(A4)] and unsym-metrical M[pz(A3B)], have been reported. In particular, the symmetrical species M[pz( A4)] have been used both as vehicles to study the fundamental physical properties of metalated porphyrazines (52) as well as to make double decker or sandwich porphyrazines, cofacial dimers linked with lanthanide metal ions (34), while the unsymmetrical species M[pz(A3B)] have utilized the alkyl-aryl substituents as solubilizing groups and have been applied to all areas of pz chemistry. 

Octapropylporphyrazines, M[pz( -Pr)s], which can be prepared from 4-octyne by the same synthetic route used to prepare octaethylporphyrazines (Scheme 4), have been used to prepare pz sandwich complexes that are cofacial dimers of two porphyrazines linked by a lanthanide ion (34). 

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-... 

Sandwich complexes of porphyrazines are prepared by direct intercalation of lanthanides between two pz ligands, the route commonly utilized for the preparation of porphyrin sandwich complexes. Interestingly, the synthetic method used for the preparation of bis(phthalocyanines), starting from the dinitrile or the dilithium substituted monophthalocyanine, has never been successfully implemented for the synthesis of porphyrazines (77). 

The controlled synthesis of carbons adjacent nido- and arachno-carborane anions can be achieved by the reduction of C (cage)-C (cage)-linked o-carboranes with group 1 metals.234-237 Typical examples are illustrated in Scheme 22. These have been found to undergo metallation reactions similar to their carbons apart analogs, forming full- and half-sandwich complexes of lanthanide metals.238... 

Anwander R (1996) Routes to Monomeric Lanthanide Alkoxides. 179 149-246 Anwander R, Herrmann WA (1996) Features of Organolanthanide Complexes. 179 1-32 Artymiuk PJ, Poirette AR, Rice DW, Willett P (1995) The Use of Graph Theoretical Methods for the Comparison of the Structures of Biological Macromolecules. 174 73-104 Astruc D (1991) The Use of p-Organoiron Sandwiches in Aromatic Chemistry. 160 47-96 Baerends EJ, see van Leeuwen R (1996) 180 107-168 Balbds LC, see Alonso JA (1996) 182 119-171... 

In a potentiometric study in propylene carbonate, using Pb11 or Tl1 as auxiliary ions, stability constants have been determined for a variety of crown ethers. Some results464 are shown in Table 8. They show that the wrap-around ligand dibenzo-30-crown-10 is relatively quite effective, while the 2 1 complexes, presumably of the sandwich type, are favoured for larger lanthanides and smaller crowns. 

The bis phthalocyanine (Pc) complex, AmPc2, has been obtained by heating Aml3 with o-phthalodinitrile in 1-chloronaphthalene411 or from americium(III) acetate and o-phthalodinitrile it is probably a sandwich compound similar to those obtained with the tripositive lanthanides.412... 

---