Sandwich-type Metal Porphyrin, Phthalocyanine, Synthesis, Characterization And Electrochemical Properties

Since the first sandwich-type phthalocyaninato rare earth complex was synthesized in 1936, all kinds of sandwich-type rare earth complexes were synthesized and researched deeply. In all these complexes, two or three macrocyclic chromophores are held in close proximity by metal ions with +3 or +4 oxidation states, as become the base of abundant properties of this family of complex. This family of complex show extraordinary optic, electronic and magnetic properties. The huge potential as materials of novel molecular conductor, molecular semi-conductor, molecular magnet, gas-sensor, electrochemically generated multicolor response and electronic field directed luminescence etc, this arose people increasing fervor of research. Our research work in this field has been focused on the following respects:1. Comparative Electrochemical Study of Unsubstituted and Substituted Bis(phthalocyaninato) Rare Earth (HI) ComplexesThe electrochemistry of homoleptic substituted phthalocyaninato rare earth double-decker complexes M(TBPc)₂ and M(OOPc)₂ [M = Y, La...Lu except Pm; H₂TBPc = 3(4),12(13),21(22),30(31)-tetra(tert-butyl)phthalocyanine, H₂OOPc = 3,4,12,13,21,22,30,31-octakis(octyloxy)phthalocyanine] has been comparatively studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in CH₂Cl₂ containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). Two quasi-reversible one-electron oxidations and three or four quasi-reversible one-electron reductions have been revealed for these neutral double-deckers of two series of substituted complexes, respectively. For the purpose of comparison, unsubstituted bis(phthalocyaninato) rare earth analogues M(Pc)₂ (M = Y, La...Lu except Pm; H₂Pc = phthalocyanine) have also been electrochemically investigated. Two quasi-reversible one-electron oxidations and up to five quasi-reversible one-electron reductions have been revealed for these neutral double-decker compounds. The three bis(phthalocyaninato) cerium compounds display one cerium-centered redoxwave that lies between the first ligand-based oxidation and reduction. The half-wave potentials of the first and second oxidations and first reduction for double-deckers of the tervalent rare earths are dependent on the size of the metal center. The difference between the redox potentials of the second and third reductions for Min(Pc)2, which represents the potential difference between the first oxidation and first reduction of [Mm(Pc)2]^, lies in the range 1.08-1.37 V and also gradually diminishes along with the lanthanide contraction, indicating enhanced jc-ji interactions in the double-deckers with smaller lanthanides compared with those connected by larger lanthanides. This corresponds well with the red-shift of the lowest energy band observed in the electronic absorption spectra of reduced double-decker [Mm(Pc')2]" (Pc' = Pc, TBPc, OOPc).2. Electrochemistry of Heteroleptic Tris(phthalocyaninato) Rare Earth(III) ComplexesThe electrochemical characteristics for a series of heteroleptic tris(phthalocyaninato) complexes with identical rare earths or mixed rare earths (Pc)M(OOPc)M(OOPc) [M = Eu-Lu, Y; H2Pc = unsubstituted phthalocyanine, H2(OOPc) = 3,4,12,13,21,22,30,31-octa(octyloxy)phthalocyanine] and (Pc)Eu(OOPc)Er(OOPc) have been recorded and comparatively studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in CH2CI2 containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). Up to five quasi-reversible one-electron oxidations and four one-electron reductions have been revealed. The half-wave potentials of the first and second oxidations are dependent on the size of the metal center. This is also true for the half-wave potentials of the fifth oxidations but its direction of change is opposite to those of the first and second oxidation potentials. Moreover, the difference of the redox potentials of the first oxidation and first reduction for (Pc)M(OOPc)M(OOPc) lying between 0.85 and 0.98 V, also decreases linearly along with the decrease of rare earth radius, clearly showing the rare earth sizeeffect and indicating enhanced Jt-jt interactions in the triple-deckers with smaller lanthanides compared with those connected by larger lanthanides. This is in line with the observation that the lowest energy band of triple-decker , compounds shifts to the red in the same order. The electronic differences between the lanthanides and yttrium are more apparent for triple-decker sandwich complexes than for the analogous double-deckers. By comparing triple-decker, double-decker and mononuclear [Zn(II)] complexes containing the OOPc ligand, the HOMO-LUMO gap was shown to contract approximately linearly with the number of stacked phthalocyanine ligands.3. Electron-Donating Alkoxy Groups-Driven Synthesis of Heteroleptic Tris(phthalocyaninato) Lanthanide(III) Triple-Deckers with Symmetrical Molecular StructureReaction of heteroleptic bis(phthalocyaninato) lanthanide compounds (Pc)M[Pc(OC8H17)8] [H2Pc = unsubstituted phthalocyanine; H2Pc(OC8Hi7)8 = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyanine] with monomeric complexes (Pc)M(acac) (Hacac = acetylacetone), both of which generated in situ, led to the isolation of heteroleptic phthalocyaninato- [2,3,9,10,16,17,23,24 -octakis(octyloxy)phthalocyaninato] lanthainde(III) triple-decker complexes (Pc)M[Pc(OC8H17)8]M(Pc) (M = Gd-Lu) (1-8) as the sole product. Hetero-dinuclear analogues (Pc)Lu[Pc(OC8Hi7)8]M(Pc) (M = Gd-Yb) (9-15) were obtained in a similar manner from the reaction of (Pc)M[Pc(OCsHi7)8] (M = Gd-Yb) and (Pc)Lu(acac). The molecular structures of hertero-dinuclear compound (Pc)Lu[Pc(OC8Hi7)8]Er(Pc) (13) and its homo-dinuclear counterparts (Pc)M[Pc(OC8Hn)8]M(Pc) (M = Er, Lu) (5, 8) have been determined by X-ray diffraction analysis, which exhibits a symmetrical molecular structure with one inner planar Pc(OC8Hi7)8 ligand and two outer domed Pc ligands. In addition to various spectroscopic analyses, the electrochemistry of these compounds has also been studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, revealing the gradually enhanced jt-jt interactionsamong the phthalocyanine rings in the triple-deckers along with the lanthanide contraction.