Double-decker lanthanide complexes

As a result of their low redox potentials [173], bis(phthalocyaninato) lanthanide complexes are often inadvertently reduced or oxidized, and they are also very sensitive to acids and bases. In order to solve these problems, Veciana et al. achieved certain success on designing a series of novel compounds with characteristics that would give them improved redox stability. Electroactive ligands based on phthalo-cyaninato tetra dicarboximide [175] or perfluorinated phthalocyanine [176] were used to assemble the double-decker lanthanide complexes, with the effect of stabilizing the negative charge of the anionic state of the compounds, which resulted in a strong shift of 0.7 V of their first oxidation potentials. 

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-... 

Recently, the use of pthalocyanines and porphyrins by Ishikawa and coworkers enabled tiie synthesis of several so-called double-decker or triple-decker lanthanide complexes, described as stacked Ji-conjugate molecules. The photophysical properties of lantiianide ious depeud markedly on their coordination environments. Since a multidecker framework can effectively keep solvent molecules away from Ln centers, it is assumed that enhanced luminescent properties can be achieved witii these types of architectures. We discovered that the use of two conjugated Schiff-base ligands H2Lh can stabihze novel multidecker framewoiks (Scheme 1). 

Pushkarev VE, Tolbin AY, Zhurkin EE, Borisova NE, Trashin SA, Tomilova LG et al (2012) Sandwich double-decker lanthanide(III) Intracavity Complexes based on clamshell-type phthalocyanine ligands synthesis, spectral, electrochemical, and spectroelectrochemical investigations. Chem Eur J 18(29) 9046-9055... 

After our report, many other examples of SIMs based on mononuclear lanthanide complexes have appeared. As relevant examples, we should mention the erbium-organometallic double-decker complexes [11] and the dysprosium-acetylacetonate complexes [12], and the dysprosium-DOTA (H4DOTA, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) complexes reported by Sessoli etal. [13]. 

Ishikawa, N., Sugita, M., Ishikawa, T., Koshihara, S.Y. and Kaizu, Y. (2003) Lanthanide double-decker complexes functioning as magnets at the single-molecular level. J. Am. Chem. Soc., 125, 8694-8695. 

Determination of Ligand-field parameters and f-electronic structures of Double-Decker Bis(phthalocyaninato)lanthanide complexes. Inorg. Chem., 42, 2440 - 2446. 

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). 

The temperature ranges in which the magnetization relaxations are observed in [Pc2Tb] TBA+ and [Pc2Dy] TBA+, are significantly higher than any of the 3d metal-cluster SMMs. The SMM behavior was not observed for the Pc double-decker complexes with other heavy-lanthanide (Ho, Er, Tm and Yb). 

Synthetic, spectroscopic, and theoretical study of novel supramolecular structures composed of lanthanide phthalocyanine double-decker complexes 02CCR (226)93. 

Buchler, Weiss and coworkers have recently described the structures of lanthanide porphyrins. The structures of cerium(IV) doubledecker and biscerium(III) tripledecker molecules have been described [Ce(OEP)2] and [Ce2(OEP)3] have cerium ions with approximate square-antiprismatic geometry in both complexes. In the double-decker complex, the Ce-Np bond length is 2.475(1) A. The two porphyrin rings are rotated by about 43° with respect to each other. A quite similar structure is seen for [Eu(OEP)2] . In this structure, Eu-Np is slightly longer at 2.510(2) A. The two rings... 

Due to their large size, the inclusion of rare-earth metals into phthalocyanines leads to neutral, double-decker, bis(phthalocyaninato)lanthanide(III) complexes.In these compounds, the triva-lent lanthanide(III) ion is sandwiched between the two macrocyclic ligands, with the rings being rotated with respect to each other by 45°. The coordination polyhedron corresponds to a distorted square antiprism due to the non-equivalent bending deformations of both macrocyles... 

Double-decker phthalocyanine lanthanide complexes have a high stability [1], intense absorption and can be used in various technological [2] and biomedical applications [3]. Therefore, it is necessary to study the nature of the bands in the electronic absorption spectra, as well as the possibility of changing the spectral properties depending on the composition of multicomponent systems. 

A double-decker complex of bis-phthalocyanines of lanthanides is aniuterestiug model of H-aggregates of phthalocyanines. Therefore, it is important to study their properties. 

The objects of study were double-decker phthalocyanine lanthanide complexes with the lutetium (Lu), ytteibium (Yb), holmium (Ho) and erbium (Er) as metal-... 

Double-decker phthalocyanines are soluble in a narrow range of solvents and are insoluble in water, however, we have developed methods for preparing aqueous multicomponent systems based on lanthanide complexes phthalocyanines double-decker. Macromolecular stmctures (proteins, polymers), supiamolecular stmctures (micelles) and nanosized silica were used as solubilizers. 

Study of the spectral properties of double-decker phthalocyanine based on lanthanide complexes is one of the most promising area of research due to their attractiveness for applications primarily in the biomedical field [13] as a prototype sensitive model. 

The nature of central atom has little effect on the differences in spectral properties of double-decker bis-phthalocyanine. Double-decker bis-phthalocyanine complexes of lanthanides LuPc, YbPc, ErPc, HoPc ate in monoradical neutral form in chloroform and anion form in dimethylformainide. In both cases the position of the bands at 660-668 nm and 462-466 nm (for the neutral form monotadical), 616-622 nm and 674-696 nm (for the anionic form) is linearly correlated with the value of the ionic radius of lanthanide. A broad band of low intensity in the region of 920 nm corresponds to the radical part of bis-phthalocyanine complex. 

Pushkarev VE, Tolbin AY, Borisova NE, Trashin SA, Tomilova LG (2010) A3B-type phthalocyanine-based homoleptic lanthanide (III) double-decker 7i-radical complexes bearing functional hydroxy groups synthetic approach, spectral properties and electrochemical study. Eur J Inorg Chem 2010(33) 5254-5262... 

---