New developments as well as a historic overview on synthetic strategies for preparation of the rare-earth complexes with porphyrins, phthalocyanines, naphthalocyanines, tetraazaporphyrins, and related systems are discussed in detail with emphasis on selective synthetic pathways for preparation of single-, double, and triple-decker architectures. 6 IntroductionAfter their discovery almost 100 years ago, phthalocyanines (Pcs) were predominantly investigated because of their industrial applications as dyes, pigments, and catalysts [1][2][3].Similarly, historically, porphyrins (Pors) were intensively studied because of their importance in mimicking biologically relevant atom-and electron-transfer processes as well as light-harvesting mechanisms associated with living cells [4][5][6]. In addition, porphyrins, phthalocyanines, and their analogues were found to be useful in applications such as redox-driven fluorescence markers and biomarkers, light-harvesting antennas for organic photovoltaics and dye sensitized solar cells, charge carriers for copiers and printers, materials for molecular electronics, as well as redoxactive components in environmental, biological, and industrial sensors as well as active components in photodynamic therapy (PDT) and boron neutron therapy (BNT) of cancer [7][8][9][10][11][12][13][14][15][16][17][18][19].In their initial attempts, researchers focused on rich coordination, redox, and magnetic properties of the metal-free, main-group, and especially transition-metal porphyrinoids. It was soon realized, however, that the rare-earth ions can form unusual systems when coupled with the phthalocyanine ligand.The first rare-earth Pcs were reported by Russian scientists Kirin and Moskalev in 1965 [20]. Kirin and Moskalev also pointed out that because of the large ionic radii and high coordination numbers of the rare-earth ions, the formation of the double-decker rare-earth phthalocyanine compounds could be achieved under specific reaction conditions [20,21]. During the next 50 years, it was confirmed that rare-earth ions are capable of the formation of phthalocyanine single-, double, and triple-decker complexes and their analogues [22][23][24][25][26][27][28][29][30][31][32][33]. One of the interesting recent discoveries was the preparation and characterization of heteronuclear (rareearth / cadmium) multiple-decker complexes, which contain up to six Pc ligands [34][35][36][37][38][39][40][41][42].

Phthalocyanine compounds of novel type based on a bridged bis-ligand, denoted "intracavity" complexes, have been prepared. Complexation of clamshell ligand 1,1'-[benzene-1,2-diylbis(methanediyloxy)]bis[9(10),16(17),23(24)-tri-tert-butylphthalocyanine] ((clam,tBu)Pc(2)H(4), 1) with lanthanide(III) salts [Ln(acac)(3)]⋅n H(2)O (Ln = Eu, Dy, Lu; acetylacetonate) led to formation of double-deckers (clam,tBu)Pc(2)Ln (2 a-c). Formation of high molecular weight oligophthalocyanine complexes was demonstrated as well. The presence of an intramolecular covalent bridge affecting the relative arrangement of macrocycles was shown to result in specific physicochemical properties. A combination of UV/Vis/NIR and NMR spectroscopy, MALDI-TOF mass-spectrometry, cyclic voltammetry, and spectroelectrochemistry provided unambiguous characterization of the freshly prepared bis-phthalocyanines, and also revealed intrinsic peculiarities in the structure-property relationship, which were supported by theoretical calculations. Unexpected NMR activity of the paramagnetic dysprosium complex 2 b in the neutral π-radical form was observed and examined as well.

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