L. A. Lapkina

Supramolecular systems constructed from Crownphthalocyaninates

A review of coordination compounds of several metals (Co2+, Ru2+, Zn2+, Al3+, Y3+, Ln3+ = La, Gd, Yb, Lu) with tetra-crown-substituted phthalocyanine H2R4Pc (R4Pc2− = [4,5,4′,5′,4′′,5′′,4′′′,5′′′-tetrakis(1,4,7,10,13-pentaoxotridecamethylen)phthalocyaninate-ion]) has been presented. The syntheses of compounds with a given tetra-azamacrocyclic ligand are described. The template method based on the crown-substituted phthalodinitrile is the optimum technique for preparation of Ru2+ monophthalocyaninate and sandwich complexes of Lu3+. For other rare earth metals the new synthetic approach based on the application of the H2R4Pc ligand has been suggested. Some aspects of supramolecular chemistry including cation-induced aggregation in solutions have been discussed for the compounds of this class.

Synthesis, spectral properties, cation-induced dimerization and photochemical stability of tetra-(15-crown-5)-phthalocyaninato indium(III)

The novel 2,3,9,10,16,17,23,24-tetra-(15-crown-5)phthalocyaninato indium(III) hydroxide [(15C5)4Pc]In(OH)(I) was obtained by direct interaction of tetra-(15-crown-5)-phthalocyanine with indium acetylacetonate with 90% yield. The set of UV-vis, 1H NMR and MALDI-TOF spectroscopy data allowed the unambiguous interpretation of complex structure. It was shown that the developed synthetic approach can be also used for synthesis of indium(III) 2,3,9,10,16,17,23,24-octabutoxyphthalocyanine [(BuO)8Pc]In(OH)(II). Photophysical characteristics (fluorescence and singlet oxygen quantum yields) of I were established. The photochemical stability of I was compared with tetra-(15-crown-5)-phthalocyanine H2[(15C5)4Pc] and aluminum(III) complex [(15C5)4Pc]Al(OH). It was found that cation-induced formation of cofacial dimers [2I × 4MX] (M = K+, Rb+, X = CO32-, OPic-, OPiv-, SO42-, ClO4-, Br-) resulted in significant enhancement of complex photostability.

Photoelectric, nonlinear optical, and photorefractive properties of composites based on poly(N-vinylcarbazole) and gallium phthalocyaninate

Poly(N-vinylcarbazole) layers containing tetra-5-crown-5-gallium phthalocyaninate (R4Pc)Ga(OH) are shown to possess photoelectric and photorefractive sensitivity at a wavelength of 1064 nm. This effect is associated with the formation of supramolecular ensembles of (R4Pc)Ga(OH) molecules with electronic optical absorption in the near-IR range and nonlinear optical properties. For the composite containing 5 wt % (R4Pc)Ga(OH) supramolecular ensembles, the dependence of the quantum efficiency of mobile-charge photogeneration on electric field E0 is well fit by the Onsager equation expanded to E03 at a quantum yield of electron-hole pairs of φ0 = 0.9 s with an initial separation radius of r0 = 9.8 A susceptibility χ(3) equal to 1.85 × 10−10 esu is measured via the well-known method of electric-field-induced second-harmonic generation. Two-beam-coupling gain coefficient Γ is found to be 80 cm−1 at E0 = 120 V/μm.

Erbium complexes with tetra-15-crown-5-phthalocyanine: Synthesis and spectroscopic study

Erbium mono-, bis-, and tris(phthalocyaninates) with tetra-15-crown-5-phthalocyanine (H2R4Pc) were synthesized and studied by spectroscopic methods. The complexes were obtained by reacting H2R4Pc with erbium salts in high-boiling solvents. To compare the efficiency of two approaches to the synthesis of double-decker lanthanide phthalocyaninates, bis(phthalocyaninate) [Er(R4Pc)2] was also obtained by a template procedure from dicyanobenzo-15-crown-5. A combination of physicochemical methods (UV and IR spectroscopy, MALDI-TOF mass spectrometry, 1H NMR) was used for identifying the compounds and proving their individuality and structure. The photoluminescence method demonstrated that solutions of erbium bis- and tris(phthalocyaninates) in CHCl3 are nonfluorescent in the visible range of light whereas solutions of mono(phthalocyaninate) in CHCl3 and DMSO exhibit fluorescence with maxima at 707 and 695 nm, respectively. The oxidation of erbium mono(phthalocyaninate) leads to fluorescence quenching.

Behavior of aluminum(III)-tetra-15-crown-5-phthalocyaninates in organic media by fluorescence and UV-visible spectroscopy

The results of a UV-vis and fluorescent spectral investigation of a tetra-15-crown-5-substituted aluminum phthalocyanine [(R4Pc)Al(OH)] (1), where (R4Pc)2- = 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninate-dianion, in different solvents (CHCl3, DMSO, MeOH) are reported. It was shown that compound exhibits a very strong tendency to aggregation with the formation of μ-fluoro dimer [((R4Pc)Al)2F]+ in the presence of F- in the low-donor solvent CHCl3. This complex is not emissive. The formation of two different emissive species [(R4Pc)AlF2]- and [(R4Pc)Al(OH)2]- during the reaction of 1 with anions (F- and OH- correspondently) in high-donor DMSO was established.

Physicochemical properties of solutions and ultrathin films of triple-decker gadolinium tetra-15-crown-5-phthalocyaninate

The ability of the triple-decker gadolinium complex with tetra-15-crown-5-phthalocyanine Gd2(R4Pc)3, (R = 15-crown-5) (1) to form monolayers and Langmuir-Blodgett films (LBFs) was studied for the first time. The charge characteristics of molecules of a triple-decker phthalocyaninate in monolayer, as well as their orientation and adhesion to the water subphase, were controlled by changing the surface pressure, pH, and subphase composition (aqueous solutions containing triethylenetetramine (TETA) and metal cations). It was shown that the presence of Na+ and protonated TETA aminogroups in resulted in an increasing limiting monolayer area and significant decreasing of the monolayer liquid state region. It is proven that the observed effects are caused by the conformational and charge transitions of peripheral crown ethers induced by their interaction with cations. A comparison of the differential reflectance spectra of the complex monolayer on the deionized water surface with UV-Vis absorption spectra of three-layer Gd2(R4Pc)3 LBF and complex solution in chloroform shows that partial complex oxidation and intensive stacking formation occurs already at the stage of monolayer formation on the subphase surface. Electrochemical studies of three-layer LBFs performed at the indium-tin-oxide electrodes (ITO-electrodes) using cyclic voltammetry (CV) showed three reversible redox waves in the potential range −200 to +1100 mV (vs. Ag+/AgCl). All registered peaks remain the same position and intensity upon multiple cycling. plasmon resonance (SPR) measurements allow to register three stable redox states of studied LBF upon applying the external potential. Such behavior shows the possibility to use multistep redox transformations of studied complex LBF for developing of stable and reproducible switchable optoelectronic systems.

Electrochemical and spectral properties of tris[tetra(15-crown-5)phthalocyaninato]dilutetium(III)

Tris[tetra(15-crown-5)phthalocyaninato]dilutetium(III) (R4Pc)3Lu2, whose structure had been confirmed earlier by X-ray analysis, was further examined by physicochemical studies. The redox properties of this complex were investigated by cyclic voltammetry. The spectroelectrochemical study of this compound has been performed for the first time. Based on the results obtained and analysis of literature data, an electrochemical criterion related to double- and triple-decker structure of lanthanide phthalocyanines has been proposed. IR and 1H NMR data are also reported.

Photorefractive and nonlinear optical properties of indium(III) tetra(15-crown-5)phthalocyaninate-based composites

Photoelectric, nonlinear optical, and photorefractive properties of hybrid composite materials based on polyvinylcarbazole (PVK) and indium(III) 2,3,9,10,16,17,23,24-tetra(15-crown-5)phthalocyaninate [(15C5)4Pc]In(OH) are studied in detail. Field dependence of the quantum efficiency in a 7.8 μm-thick layer containing 5 at % [(15C5)4Pc]In(OH) is measured. The best approximation of the quantum efficiency with Onsager’s equation corresponds to a quantum yield of thermalized electron-hole pairs φ0 = 0.01 at initial separation r0 = 9.8 Å. Z-scan measurements in a nanosecond range showed that the electric susceptibility of [(15C5)4Pc]In(OH) solution in tetrachloroethane (TCE) with a concentration of 7 × 10−4 mol/L is χ(3) = 1.34 × 10−9 esu. The maximum coupling gain coefficient found for the material composed of PVK and 5 wt % [(15C5)4Pc]In(OH) at an electric-field intensity of 200 V/μm is Γ = 80 cm−1, and the difference between the coupling gain and absorption coefficients is Γ − α = 70 cm−1. The dependence of the coupling gain coefficient on the intensity ratio of interfering beams 1 and 2 (β = I1(0)/I2(0)) in a composite containing 3 wt % [(15C5)4Pc]In(OH) is measured. An increase in β was attained by decreasing intensity of the signal beam I2(0) at constant intensity of the pump beam I1(0) = 0.15 W/cm2 and E0 = 214 V/μm. Within the initial segment of the curve, the coupling gain coefficient increases from 30 to 60 cm−1; then, the coefficient drops almost to the initial value. The data obtained show that the composite materials studied can be used in practice for correcting faded images. The combined analysis of the results obtained and similar data for gallium and ruthenium tetra-15-crown-5-phthalocyaninate complexes revealed the regularities in the change of the quantum yield of thermalized electron-hole pairs and the photorefractive coupling gain coefficient in a series of complexing metals: gallium(III), ruthenium(II), and indium(III). An increase in the molecular weight of the central metal atom is found to result in a substantial decrease in Γ and φ0 due to the increase in the spin-orbit coupling constant.

Nonlinear optical properties of systems based on (tetra-15-crown-5-phthalocyaninato)indium(III)

The nonlinear optical properties of solutions of (2,3,9,10,16,17,23,24-tetra-15-crown-5-phthalocyaninato)indium(III) [(15C5)4Pc]In(OH) in tetrachloroethane (TCE) have been studied by the z-scan method. It has been found that a nonlinear optical response is due to supramolecular associates formed in a tetrachloroethane solution by heating to 90°C/slow cooling to room temperature cycling. The formation of the supramolecular associates has been studied by atomic force microscopy (AFM) and electronic absorption spectroscopy (EAS). It has been shown that a single thermal treatment of [(15C5)4Pc]In(OH) solutions in TCE results in the predominant formation of dimers, as evidenced by both a short-wavelength shift of the Q-absorption band of the monomeric complex (λmax = 692 nm) to the band of λmax = 653 nm and height doubling of molecular entities as measured by AFM. The dimers are responsible for the two-photon absorption measured in the femtosecond range, which has a relatively high cross section of σ2 = 1.38 × 10−46 cm4 s/(molecule, photon) or 1.38 × 104 GM. According to the AFM data, three cycles of heat treatment of the solution leads to the formation of supramolecular assemblies of about 200 nm length. The optical spectrum exhibits long-wavelength absorption at λmax = 841 nm and the long-wavelength edge near 1300 nm. In the case of nanosecond 1064-nm laser irradiation, the linear absorption S0 → S1 is primary, having the cross section of σ0 = α0/N = 2.3 × 10−20 cm2. The known high quantum yield (close to unity) of triplet states of indium phthalocyanines suggests that the main nonlinear optical effect is determined by intersystem crossing S1 → T1 and triplet-triplet absorption T1 → T2. The absorption cross section is σT-T = 1.14 × 10−19 cm2.

Crown-substituted Sc(III) phthalocyaninates: Synthesis and spectral properties

The scandium(III) complexes with tetra(15-crown-5)phthalocyanine [Sc(R4Pc)2]·0 (I) and Sc(R4Pc) · OAc (II) have been synthesized by condensation of Sc3+ with phthalocyanine H2R4Pc (4,5,4′,5′,4″,5″,4‴,5‴-tetrakis(1,4,7,10,13-pentaoxatridecamethylene)phthalocyanine). Compounds I and II have been characterized by spectral methods: electronic absorption spectroscopy, MALDI-TOF MS, IR spectroscopy, and 1H NMR. The redox properties of I and the photoluminescent properties of II have been studied.