Ferrocene-decorated (phthalocyaninato)(porphyrinato) double- and triple-decker rare earth complexes: synthesis, structure, and electrochemical properties

A series of four mixed (phthalocyaninato)(porphyrinato) rare earth double-decker complexes (Pc)M[Por(Fc)(2)] [Pc = phthalocyaninate; Por(Fc)(2) = 5,15-di(ferrocenyl)-porphyrinate; M = Eu (1), Y (2), Ho (3), Lu (4)] and their europium(III) triple-decker counterpart (Pc)Eu(Pc)Eu[Por(Fc)(2)] (5), each with two ferrocenyl units at the meso-positions of their porphyrin ligands, have been designed and prepared. The double- and triple-decker complexes 1-5 were characterized by elemental analysis and various spectroscopic methods. The molecular structures of two double-deckers 1 and 4 were also determined by single-crystal X-ray diffraction analysis. Electrochemical studies of these novel sandwich complexes revealed two consecutive ferrocene-based one-electron oxidation waves, suggesting the effective electronic coupling between the two ferrocenyl units. Nevertheless, the separation between the two consecutive ferrocene-based oxidation waves increases from 1 to 4, along with the decrease of rare earth ionic radius, indicating the effect of rare earth size on tuning the coupling between the two ferrocenyl units. Furthermore, the splitting between the two ferrocene-based one-electron oxidations for triple-decker 5 is even smaller than that for 1, showing that the electronic interaction between the two ferrocene centers can also be tuned through changing the linking sandwich framework from double-decker to triple-decker. For further understanding of the electronic coupling between ferrocenyl groups, DFT calculation is carried out to clarify the electronic delocalization and the molecular orbital distribution in these double-decker complexes.     

Porphyrin-appended europium(III) bis(phthalocyaninato) complexes: synthesis, characterization, and photophysical properties

Mixed cyclization of 3-mono-, 4-mono-, or 4,5-di(porphyrinated) phthalonitrile compounds 2, 3, or 6 and unsubstituted phthalonitrile with the half-sandwich complex [EuIII(acac)(Pc)] (Pc=phthalocyaninate, acac=acetylacetonate) as the template in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in n-pentanol afforded novel porphyrin-appended europium(III) bis(phthalocyaninato) complexes 7-9 in 30-40% yield. These mixed tetrapyrrole triads and tetrad were spectroscopically and electrochemically characterized and their photophysical properties were also investigated with steady-state and transient spectroscopic methods. It has been found that the fluorescence of the porphyrin moiety is quenched effectively by the double-decker unit through an intramolecular photoinduced electron-transfer process, which takes place in several hundred femtoseconds, while the recombination of the charge-separated state occurs in several picoseconds. By using different phthalocyanines containing different numbers of porphyrin substituents at the peripheral or nonperipheral position(s) of the ligand, while the other unsubstituted phthalocyanine remains unchanged in these double-deckers, the effects of the number and the position of the porphyrin substituents on these photophysical processes were also examined.     

Optically active mixed phthalocyaninato-porphyrinato rare-earth double-decker complexes: synthesis, spectroscopy, and solvent-dependent molecular conformations

Reaction between the optically active metal-free phthalocyanine with a pi system with noncentrosymmetrical C(2) [corrected] symmetry ((S)- and (R)-H(2){Pc(OBNP)(2)}; OBNP=binaphthylphthalocyanine) and half-sandwich complexes [M(III)(acac)(TClPP)] (M=Y, Eu; TClPP=meso-tetrakis(4-chlorophenyl)porphyrinate; acac=acetylacetonate), which were generated in situ from [M(acac)(3)].n H(2)O and H(2)(TClPP) in n-octanol at reflux, provided the first optically active protonated mixed phthalocyaninato-porphyrinato rare-earth double-decker complexes [M(III)H{Pc(OBNP)(2)}(TClPP)] (M=Y, Eu) in good yield. In addition to electronic absorption spectroscopy and magnetic circular dichroism results, circular dichroism shows different spectroscopic features of these mixed-ring rare-earth double-decker compounds in different solvents, such as DMF and CHCl(3), which was well-reproduced on the basis of time-dependent density functional theory calculation results for the yttrium species (S)-[Y(III){Pc(OBNP)(2)}(Por)](-) (Por=porphyrinate, which is obtained by removing the four chlorophenyl groups from the TClPP ligand) in terms of the change in the rotation angle between the two macrocyclic ligands in the double-decker molecules. These results revealed the solvent-dependent nature of the molecular conformation of mixed-ring rare-earth double-decker complexes, which suggests a new way of tuning the optical and the electrochemical properties of sandwich-type bis(tetrapyrrole)-metal double-decker complexes in solution by changing the solvent.     

Heteroleptic bis(phthalocyaninato) europium(III) complexes fused with different numbers of 15-crown-5 moieties. Synthesis, spectroscopy, electrochemistry, and supramolecular structure

A series of heteroleptic bis(phthalocyaninato) europium(III) complexes, namely, Eu(Pc)[Pc(15C5)] (2), Eu(Pc)[Pc(opp-15C5)2] (3), Eu(Pc)[Pc(adj-15C5)2] (4), Eu(Pc)[Pc(15C5)3] (5), and Eu(Pc)[Pc(15C5)4] (6) [Pc = unsubstituted phthalocyaninate; Pc(15C5) = 2,3-(15-crown-5)phthalocyaninate; Pc(opp-15C5)2 = 2,3,16,17-bis(15-crown-5)phthalocyaninate; Pc(adj-15C5)2 = 2,3,9,10-bis(15-crown-5)phthalocyaninate; Pc(15C5)3 = 2,3,9,10,16,17-tris(15-crown-5)phthalocyaninate, Pc(15C5)4 = 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninate], with one, two, three, and four 15-crown-5 voids attached at different positions of one of the two phthalocyaninato ligands in the double-decker molecules, have been devised and prepared by Eu(Pc)(acac)-induced (Hacac = acetylacetone) mixed cyclization of the two corresponding phthalonitriles in the presence of organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in n-pentanol. For the purpose of comparative studies, homoleptic counterparts Eu(Pc)2 (1) and Eu[Pc(15C5)4]2 (7) have also been prepared. These sandwich double-decker complexes have been characterized by a wide range of spectroscopic methods in addition to elemental analysis. Their electrochemistry has also been studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The molecular structure of Eu(Pc)[Pc(15C5)4] (6) has been determined by X-ray diffraction analysis. Their supramolecular structure-formation properties, in particular for compounds 5 and 6 in the presence of potassium ions, have also been comparatively studied for the purpose of future functional investigation.     

Conformational effects, molecular orbitals, and reaction activities of bis(phthalocyaninato) lanthanum double-deckers: density functional theory calculations

The conformational effects on the frontier molecular orbital energy and stability for reduced, neutral, and oxidized bis(phthalocyaninato) lanthanum double-deckers have been revealed on the basis of density functional theory calculations. Calculation results indicate that the frontier orbital coupling degree changes along with the molecular conformation of the double-decker compound, first decreasing along with the increase of rotation angle β from 0 to 20° and then increasing along with the increase of rotation angle β from 20 to 45°. In addition, the stability for the three forms of double-decker changes in the same order, but first increasing and then decreasing along with the change of the rotation angle β in the range of 0 to 45° with a rotation energy barrier of (31.3 ± 3.1) kJ mol(-1) at 20°. This reveals that the rotation of the two phthalocyanine rings for the reduced, neutral, and oxidized bis(phthalocyaninato) lanthanum double-deckers are able to occur at room temperature. Nevertheless, the superior coordination reaction activity of the neutral bis(phthalocyaninato) lanthanum double-decker complex over their reduced form in forming sandwich-type tris(phthalocyaninato) lanthanum triple-decker compounds has also been clearly clarified on the basis of comparative calculations on the Fukui function of [La(Pc)(2)] and [La(Pc)(2)](-) using the DFT method. Fukui function analysis reveals the reaction center of the 18-electron-π-conjugated core in the bis(phthalocyaninato) lanthanum double-decker molecule against both electrophilic and radical attack. Nevertheless, the larger global chemical softness (S) for the neutral [La(Pc)(2)] than the reduced form [La(Pc)(2)](-) indicates the higher reaction activity of the former form over the latter one. This explains well the experimental findings that only the neutral instead of the reduced form of bis(tetrapyrrole) rare earth double-decker complexes, containing at least one phthalocyanine ligand, could be employed as starting materials towards the preparation of tris(tetrapyrrole) rare earth triple-decker complexes by a solution process.     

Vibrational spectra of mixed (phthalocyaninato)(porphyrinato) yttrium(III) double-decker complexes: Density functional theory calculations

The vibrational (IR and Raman) spectra of neutral and reduced mixed (phthalocyaninato)(porphyrinato) yttrium(III) double-decker complexes Y(Pc)(Por) and [Y(Pc)(Por)]⁻ [the simplified models of mixed (phthalocyaninato)(porphyrinato) rare earth(III) complexes] are studied using density functional theory (DFT) calculations. The simulated IR and Raman spectra of Y(Pc)(Por) are compared with the experimental IR spectrum of Tb(Pc)(TClPP) and Raman spectrum of Y(Pc)(TClPP), respectively, and many bands can acceptably fit in spite of the different species. On the basis of comparison with the simulated spectra of PbPc and PbPor together with the assistance of normal coordinate analysis, the calculated frequencies in their IR and Raman spectra are identified in terms of the vibrational mode of different ligand for the first time. The calculated frequency at 1048 cm⁻¹ in the IR spectrum of [Y(Pc)(Por)]⁻ with contribution from both Pc and Por vibrational modes is the characteristic IR vibrational mode of the reduced double-decker, while the characteristic IR vibrational mode of Y(Pc)(Por) attributed from the vibration of phthalocyanine monoanion radical Pc⁻ appears at 1257 cm⁻¹. In line with our previous experimental findings that the Raman spectra of M(Pc)(TPP) and M(Pc)(TClPP) are dominated by the Pc vibrational modes, theoretical calculations indicate that most of the Raman vibrational modes contributed from Por ring are covered up by those of Pc ring and thus are hard to be recognized in the Raman spectra of [Y(Pc)(Por)]⁻ and Y(Pc)(Por) due to their much weaker intensity in comparison with that of Pc ligand. Comparison in the IR and Raman spectra between [Y(Pc)(Por)]⁻ and Y(Pc)(Por) also suggests the localization of hole on the Pc ring in the neutral double-decker Y(Pc)(Por). The present work, representing the first detailed DFT study on the vibrational spectra of mixed (phthalocyaninato)(porphyrinato) rare earth(III) double-decker complexes, is useful in helping to understand the vibrational spectroscopic properties of this series of mixed tetrapyrrole ring complexes.     

Two-dimensional crystal growth and stacking of bis(phthalocyaninato) rare earth sandwich complexes at the 1-phenyloctane/graphite interface

Initial stages of two-dimensional crystal growth of the double-decker sandwich complex Lu(Pc*)2 [Pc* = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] have been studied by scanning tunneling microscopy at the liquid/solid interface between 1-phenyloctane and highly oriented pyrolytic graphite. High-resolution images strongly suggest alignment of the double-decker molecules into monolayers with the phthalocyanine rings parallel to the surface. Domains were observed with either hexagonal or quadrate packing motifs, and the growing interface of the layer was imaged. Molecular resolution was achieved, and the face of the phthalocyanine rings appeared as somewhat diffuse circular features. The alkyl chains are proposed to be interdigitating to maintain planar side-by-side packing.     

Location of the hole and acid proton in neutral nonprotonated and protonated mixed (phthalocyaninato)(porphyrinato) yttrium double-decker complexes: density functional theory calculations

The location of the hole and acid proton in neutral nonprotonated and protonated mixed (phthalocyaninato)(porphyrinato) yttrium double-decker complexes, respectively, is studied on the basis of density functional theory (DFT) calculations on the molecular structures, molecular orbitals, atomic charges, and electronic absorption and infrared spectra of the neutral, reduced, and two possible protonated species of a mixed (phthalocyaninato)(porphyrinato) yttrium compound: [(Pc)Y(Por)], [(Pc)Y(Por)]-, [(HPc)Y(Por)], and [(Pc)Y(HPor)], respectively. When the neutral [(Pc)Y(Por)] is reduced to [(Pc)Y(Por)]-, the calculated results on the molecular structure, atomic charge, and electronic absorption and infrared spectra show that the added electron has more influence on the Pc ring than on its Por counterpart, suggesting that the location of the hole is on the Pc ring in neutral [(Pc)Y(Por)]. Nevertheless, comparison of the calculation results on the structure, orbital composition, charge distribution, and electronic absorption and infrared spectra between [(HPc)Y(Por)] and [(Pc)Y(HPor)] leads to the conclusion that the acid proton in the protonated mixed (phthalocyaninato)(porphyrinato) yttrium compound should be localized on the Por ring rather than the Pc ring, despite the localization of the hole on the Pc ring in [(Pc)Y(Por)]. This result is in line with the trend revealed by comparative studies of the X-ray single-crystal molecular structures between [MIII{Pc(alpha-OC5H11)4}(TClPP)] and [M(III)H{Pc(alpha-OC5H11)4}(TClPP)] (H2TClPP=5,10,15,20-tetrakis(4-chlorophenyl)porphyrin; M=Sm, Eu). The present work not only represents the first systemic DFT study on the structures and properties of mixed (phthalocyaninato)(porphyrinato) yttrium double-decker complexes, but more importantly sheds further light on the nature of protonated bis(tetrapyrrole) rare-earth complexes.     

Controlling the nature of mixed (phthalocyaninato)(porphyrinato) rare-earth(III) double-decker complexes: the effects of nonperipheral alkoxy substitution of the phthalocyanine ligand

The half-sandwich rare-earth complexes [M(III)(acac)(TClPP)] (M = Sm, Eu, Y; TClPP = meso-tetrakis(4-chlorophenyl)porphyrinate; acac = acetylacetonate), generated in situ from [M(acac)3] x n H2O and H2(TClPP), were treated with 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine [H2{Pc(alpha-OC5H11)4}] (Pc = phthalocyaninate) under reflux in n-octanol to yield both the neutral nonprotonated and protonated (phthalocyaninato)(porphyrinato) rare-earth double-decker complexes, [M(III){Pc(alpha-OC5H11)4}(TClPP)] (1-3) and [M(III)H{Pc(alpha-OC5H11)4}(TClPP)] (4-6), respectively. In contrast, reaction of [Y(III)(acac)(TClPP)] with 1,4,8,11,15,18,22,25-octakis(1-butyloxy)phthalocyanine [H2Pc(alpha-OC4H9)8] gave only the protonated double-decker complex [Y(III)H{Pc(alpha-OC4H9)8}(TClPP)] (7). These observations clearly show the importance of the number and positions of substituents on the phthalocyanine ligand in controlling the nature of the (phthalocyaninato)(porphyrinato) rare-earth double-deckers obtained. In particular, alpha-alkoxylation of the phthalocyanine ligand is found to stabilize the protonated form, a fact supported by molecular-orbital calculations. A combination of mass spectrometry, NMR, UV-visible, near-IR, MCD, and IR spectroscopy, and X-ray diffraction analyses, facilitated the differentiation of the newly prepared neutral nonprotonated and protonated double-decker complexes. The crystal structure of the protonated form has been determined for the first time.     

Axial functionalization of sterically hindered titanium phthalocyanines

Several axially functionalized, weakly aggregating titanium phthalocyanines (Pc) have been synthesized and characterized. Soluble titanium dichlorido tetrakis-(1,1,4,4-tetramethyl-6,7-tetralino)-porphyrazine [Pc(#)TiCl(2)] (5) has been prepared by reductive cyclotetramerization of the respective dinitrile precursor in the presence of TiCl(4). 5 and the analogous oxido compound [Pc(#)TiO] (1) are versatile starting materials for the formation of other axially functionalized titanium phthalocyanines such as organoimido (6, 7), alkoxido and aryloxido (8, 9), peroxido (10), sulfido (12), disulfido (11), selenido (14) or diselenido (13) species. Furthermore the deprotonated ligand salts [Pc(#)M(2)] (M = Li (2), Na (3), K (4) are described. The reactivity of the titanium compounds was studied in atom group transfer reactions and ethene polymerization. The crystal structures of 5 and the free ligand Pc(#)H(2) are reported. 5 crystallizes from dichloromethane in the cubic space group Im3. The two chlorido ligands exhibit a cis arrangement. The free ligand Pc(#)H(2) crystallizes in the trigonal space group R3.     

Annulated dinuclear metal-free and Zn(II) phthalocyanines: photophysical studies and quantum mechanical calculations

The results of steady-state and time-resolved absorption and fluorescence experiments as well as quantum mechanical density functional theory (DFT) calculations of metal-free and Zn(II) mononuclear and dinuclear (sharing a common benzene ring) phthalocyanines are presented. A detailed comparison between measured and calculated absorption spectra of all compounds is done, showing a good agreement between theory and experiment. The NH tautomerization for phthalocyanines with an extended pi-electron system was shown for the first time at room temperature. The photophysical properties of all possible NH tautomers of metal-free dinuclear Pc have been fully characterized. In the first tautomer, Pc(parallel), both pairs of hydrogen atoms are parallel to the connection line of two Pc units. The maximum of the lowest-energy Q absorption band, lambda abs, in Pc(parallel) is located at 832 nm, whereas the spectral position of the fluorescence maximum lies at lambdafl=837 nm. The second NH tautomer, Pc(perpendicular) (lambdaabs=853 nm, lambdafl=860 nm), presents the two pairs of hydrogen atoms perpendicularly orientated to the covalent axis, and the third one, Pc(mix) (lambdaabs=864 nm, lambdafl=872 nm), contributing in a minor extend to the absorption and fluorescence spectra of the metal-free dinuclear phthalocyanine, has one perpendicular and one parallel pair of hydrogen atoms. Obviously, only one configuration exists in the case of the Zn(II)-containing dinuclear phthalocyanine (lambdaabs=845 nm, lambdafl=852 nm).     

Synthesis and electrochemical properties of copper(II), manganese(III) phthalocyanines bearing chalcone groups at peripheral or nonperipheral positions

In this study, new chalcone compound 1 , new phthalonitrile derivatives 2 and 3, new copper(II), manganese(III) phthalocyanines bearing chalcone groups at peripheral or nonperipheral positions were synthesized. Electrochemistry of tetra-(4-{(2 E )-3-[2-fluoro-4-(trifluoromethyl)phenyl]prop-2-enoyl}phenoxy) substituted Co(II)Pc and Mn(III)Pcs were studied with cyclic voltammetry (CV) to determine the redox properties of the phthalocyanines. According to the results, while the CuPcs 2a and 3a showed two Pc based reduction reactions and one Pc based oxidation reaction, MnPcs 2b and 3b gave two metal-based reduction reactions. All the redox processes are shifted toward positive potentials as a result of the increased electron-withdrawing ability of the trifluoromethyl substituents.     

Metal-cation-mediated nanocrystal arrays of sandwich-type (phthalocyaninato) [tetrakis(4-pyridyl)porphyrinato] cerium complex formed at the water-chloroform interface

Regular square, wirelike, quadrate, and rodlike nanocrystal arrays of Cd2+, Hg2+, or Ag+ metal-cation-mediated sandwich-type mixed (phthalocyaninato) [5,10,15,20-tetrakis(4-pyridyl)poprhyrinato] cerium(III) double-decker complex Ce(Pc)(TPyP) have been successfully prepared at the water-chloroform interface. The nanocrystal growth processes were monitored by transmission electron microscopy (TEM), which reveals that different morphologies of nanocrystals have been fabricated from double-decker molecules connected by different kinds of metal cations, forming coordination polymers. These nanoscaled coordination polymers were characterized by FT-IR spectra and energy-dispersive X-ray spectra (EDS). EDS results clearly revealed the elements of the nanocrystals and the FT-IR spectra give evidence for the coordination interaction between the double-decker molecules and metal cations. The UV-vis absorption spectrum indicates the formation of J-aggregates of the double-decker molecules in the nanocrystals formed.     

Double-decker phthalocyanine complex: Scanning tunneling microscopy study of film formation and spin properties

We review recent studies of double-decker and triple-decker phthalocyanine (Pc) molecules adsorbed on surfaces in terms of the bonding configuration, electronic structure and spin state.     

Preparation of a water-soluble fluorinated zinc phthalocyanine and its effect for photodynamic therapy

An amphiphilic fluorinated phthalocyanine, zinc tetracarboxyoctafluorophthalocyanine (ZnC4F8Pc) was synthesized and characterized. Its photodynamic efficiency for HeLa cells was compared with hydrophilic zinc octacarboxyphthalocyanine (ZnC8Pc) and hydrophobic zinc hexadecafluorophthalocyanine (ZnF16Pc). ZnC4F8Pc had a remarkable photodynamic effect among the phthalocyanines used. The effect is apparently caused by the fact that ZnC4F8Pc is mainly accumulated in the hydrophobic lipid membrane and is in the photoactive monomer form in HeLa cells.     

Sandwich-type mixed (phthalocyaninato)(porphyrinato) rare earth double-decker complexes with decreased molecular symmetry of Cs: single crystal structure and self-assembled nano-structure

Two novel sandwich-type mixed (phthalocyaninato)(porphyrinato) rare earth double-decker complexes with decreased molecular symmetry of Cs M(Pc)[D(NHC(8)H(17))(2)PP] [M = Eu, Lu; Pc = unsubstituted phthalocyaninate; D(NHC(8)H(17))(2)PP = 5,10-di(phenyl)-15,20-di(4-octylamino-phenyl)porphyrinate] (1, 2) have been designed, prepared, and characterized. The single crystal and molecular structure of the Eu analogue has been determined by X-ray diffraction analysis, revealing the head-to-tail supramolecular chains formed from closely bound double-decker molecules depending on the N-H-N hydrogen bonds between one octyl-substituted amidocyanogen group attached at the p-position of meso-attached phenyl group of the porphyrin ligand in the mixed ring double-decker molecule and one aza-nitrogen atom of the phthalocyanine ring in the neighboring double-decker molecule in a zigzag form. Their self-assembled nano-structures have been investigated by transmission electronic microscopy (TEM) and scanning electronic microscopy (SEM). Intermolecular H-N-H hydrogen bonding interaction leads to the formation of nano-structures with fusiform morphology with 220-250 nm average width and about 10 μm length for 1 and 300 nm width and 3-5 μm length for 2, respectively, revealing the effect of molecular size in the direction perpendicular to the tetrapyrrole ring on the dimensions of self-assembled nano-structures.     

Constructing sandwich-type rare Earth double-decker complexes with N-confused porphyrinato and phthalocyaninato ligands

Reaction of the half-sandwich complexes M(III)(Pc)(acac) (M = La, Eu, Y, Lu; Pc = phthalocyaninate; acac = acetylacetonate) with the metal-free N-confused 5,10,15,20-tetrakis[(4-tert-butyl)phenyl]porphyrin (H(2)NTBPP) or its N2-position methylated analogue H(CH(3))NTBPP in refluxing 1,2,4-trichlorobenzene (TCB) led to the isolation of M(III)(Pc)(HNTBPP) (M = La, Eu, Y, Lu) or Y(III)(Pc)[(CH(3))NTBPP] in 8-15% yield. These represent the first examples of sandwich-type rare earth complexes with N-confused porphyrinato ligands. The complexes were characterized with various spectroscopic methods and elemental analysis. The molecular structures of four of these double-decker complexes were also determined by single-crystal X-ray diffraction analysis. In each of these complexes, the metal center is octa-coordinated by four isoindole nitrogen atoms of the Pc ligand, three pyrrole nitrogen atoms, and the inverted pyrrole carbon atom of the HNTBPP or (CH(3))NTBPP ligand, forming a distorted coordination square antiprism. For Eu(III)(Pc)(HNTBPP), the two macrocyclic rings are further bound to a CH(3)OH molecule through two hydrogen bonds formed between the hydroxyl group of CH(3)OH and an aza nitrogen atom of the Pc ring or the inverted pyrrole nitrogen atom of the HNTBPP ring, respectively. The location of the acidic proton at the inverted pyrrole nitrogen atom (N2) of the protonated double-deckers was revealed by (1)H NMR spectroscopy.     

Spectroscopic probing of the acid-base properties and photosensitization of a fluorinated phthalocyanine in organic solutions and liposomes

A perfluorinated derivative of phthalocyanine was synthesized as the free base, hexadeca-(2,2,2-trifluoroethoxy) phthalocyanine (H2F48Pc), and as a zinc complex, hexadeca-(2,2,2-trifluoroethoxy)-phthalocyaninatozinc (ZnF48Pc), and their spectroscopic and photochemical properties were studied. The absorption bands are shifted bathochromically relative to simple phthalocyanines, exhibiting the longest wavelength band near 735 nm (H2F48Pc) and 705 (ZnF48Pc). The solvatochromism of both compounds was modeled by Reichardt's ET(30) parameter and Kamlet, Abboud and Taft multiparameter approach. The former, simpler, model was found to be adequate. We found that H2F48Pc undergoes unique basic and acidic titrations in organic solvents. These titration processes are accompanied by spectral changes that are explained on the basis of the chromophore's symmetry. Singular value decomposition was employed to resolve the spectra into the contributions of the species at various stages of protonation and to obtain the equilibrium constants. Nuclear magnetic resonance spectra (1H, 19F and 13C) for the free base were obtained in a tetrahydrofurand8 solution. The carbon spectrum, taken as a function of temperature, provided evidence for the presence of a tautomerization process, which switches the two internal hydrogens between the four central nitrogen atoms. As far as we know, this is the first report of the measurement of the free energy of activation for such process (delta G = 10.6-11.4 kcal mol-1 between 217 and 330 K) for a phthalocyanine, in solution. Like most other phthalocyanines these two compounds also act as photosensitizers and as generators of singlet molecular oxygen. The absolute quantum yields (phi delta) for ZnF48Pc was 0.58 +/- 0.01 in benzene and 0.35 +/- 0.01 in lipid vesicles. H2F48Pc had lower yields, 0.16 and 0.005, respectively. Either protonation or deprotonation of the pyrrole nitrogens in H2F48Pc lowered the phi delta.     

Investigation of rational syntheses of heteroleptic porphyrinic lanthanide (europium, cerium) triple-decker sandwich complexes

The use of lanthanide triple-decker sandwich molecules containing porphyrins and phthalocyanines in molecular information storage applications requires the ability to attach monomeric triple deckers or arrays of triple deckers to electroactive surfaces. Such applications are limited by existing methods for preparing triple deckers. The reaction of a lanthanide porphyrin half-sandwich complex ((Por)M(acac)) with a dilithium phthalocyanine (PcLi2) in refluxing 1,2,4-trichlorobenzene (bp 214 degrees C) affords a mixture of triple deckers of composition (Pc)M(Pc)M(Por), (Por)M(Pc)M(Por), and (Pc)M(Por)M(Pc). We have investigated more directed methods for preparing triple deckers of a given type with distinct metals in each layer. Application of the method of Weiss, which employs reaction of a (Por)M(acac) species with a lanthanide double decker in refluxing 1,2,4-trichlorobenzene, afforded the desired triple decker in some cases but a mixture of triple deckers in others. The approach we developed employs in situ formation of the lanthanide reagent EuCl[N(SiMe3)2]2 or CeI[N(SiMe3)2]2, which upon reaction with a porphyrin affords the half-sandwich complex (Por)EuX or (Por)CeX' (X = Cl, N(SiMe3)2; X' = I, N(SiMe3)2). Subsequent reaction with PcLi2 gives the double decker (Por)M(Pc). The (Por(1))EuX half-sandwich complex gave the desired triple decker upon reaction with (Pc)Eu(Pc) but little of the desired product upon reaction with (Por(2))Eu(Pc). The (Por(1))CeX' half-sandwich complex reacted with europium double deckers (e.g., (tBPc)Eu(Por(2)), (tBPc)2Eu) to give the triple deckers (Por(1))Ce(tBPc)Eu(Por(2)) and (Por(1))Ce(tBPc)Eu(tBPc) in a rational manner (tB = tetra-tert-butyl). The reactions yielding the half-sandwich, double-decker, and triple-decker complexes were performed in refluxing bis(2-methoxyethyl) ether (bp 162 degrees C). The porphyrins incorporated in the various triple deckers include meso-tetrapentylporphyrin, meso-tetra-p-tolylporphyrin, octaethylporphyrin, and meso-tetraarylporphyrins bearing iodo, ethynyl, or iodo and ethynyl substituents. The triple deckers bearing iodo and/or ethynyl substituents constitute useful building blocks for information storage applications.     

Studies of "pinwheel-like" bis[1,8,15,22-tetrakis(3-pentyloxy)phthalocyaninato] rare earth(III) double-decker complexes

Homoleptic bis(phthalocyaninato) rare-earth double-deckers complexes [M(III)[Pc(alpha-OC5H11)4]2] (M = Eu, Y, Lu; Pc(alpha-OC5H11)4 = 1,8,15,22-tetrakis(3-pentyloxy)phthalocyaninate) have been prepared by treating the metal-free phthalocyanine H2Pc(alpha-OC5H11)4 with the corresponding M(acac)3.nH2O (acac = acetylacetonate) in refluxing n-octanol. Due to the C4h symmetry of the Pc(alpha-OC5H11)4 ligand and the double-decker structure, all the reactions give a mixture of two stereoisomers with C4h and D4 symmetry. The former isomer, which is a major product, can be partially separated by recrystallization due to its higher crystallinity. The molecular structure of the major isomer of the Y analogue has been determined by single-crystal X-ray diffraction analysis. The metal center is eight-coordinate bound to the isoindole nitrogen atoms of the two phthalocyaninato ligands, forming a distorted square antiprism. Such an arrangement leads to an interesting pinwheel structure when viewed along the C4 axis, which assumes a very unusual S8 symmetry. The major isomers of all these double-deckers have also been characterized with a wide range of spectroscopic methods. A systematic investigation of their electronic absorption and electrochemical data reveals that the pi-pi interaction between the two Pc(alpha-OC5H11)4 rings is weaker than that for the corresponding unsubstituted or beta-substituted bis(phthalocyaninato) analogues.