Synthesis and spectral properties of new planar binuclear phthalocyanines sharing the benzene ring

New planar binuclear phthalocyanines sharing the benzene ring were synthesized and their spectral properties were studied. Intense absorption in the near-IR region (∼850 nm) was observed for the first time. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1112–1115, July, 2006.     

Synthesis and properties of new binuclear nickel(ii) phthalocyanines

New binuclear nickel(ii) phthalonitrile complexes, viz., Ni^II 2,2",9(10),9"(10"),17(18),17"(18"),24(25),24"(25")-tetra(phenylene-1,2-dioxy)bisphthalocyanine and Ni^II 2,2",9(10),9"(10"),17(18),17"(18"),24(25),24"(25")-tetra(4-tert-butylphenylene-1,2-dioxy)bisphthalocyanine, were synthesized. The complexes were characterized by electronic spectroscopy and MALDI—TOF mass spectrometry and studied as active components for membranes of ion-selective electrodes in solutions of dicarboxylic acids.     

Study on catalytic oxidation of planar binuclear copper phthalocyanine on 2-mercaptoethanol

Mononuclear copper phthalocyanine (CuPc) and binuclear copper phthalocyanine (Cu2Pc2) were synthesized by the phenylanhydride-urea route, and their catalytic oxidation activity on 2-mercaptoethanol was studied. Based on the experimental results, a catalytic mechanism of Cu2Pc2 on 2-mercaptoethanol has been proposed. Furthermore, the effects of pH, Cu2Pc2 concentration, and temperature on the catalytic oxidation activity were evaluated. The results showed that CuPc has no catalytic activity, while Cu2Pc2 has high catalytic oxidation activity towards 2-mercaptoethanol with the optimal activity at pH 11. The reaction can further be enhanced by increasing Cu2Pc2 concentration and temperature, due to its endothermic characteristics.     

Neutral structures with a planar tetracoordinated carbon based on spiropentadiene analogues

Neutral hydrocarbon structures containing a planar tetracoordinated carbon atom are proposed on the basis of quantum chemical calculations. The planarity at the central carbon atom is achieved by using aromaticity for stabilizing a positively charged core moiety that contains the planar atom. This charge is compensated by negatively charged cyclopentadienyl rings fused on the structure, leading to neutral structures. These are found to be stable from a dynamic point of view and are potentially synthesizable through carbene chemistry. These structures can lead to new breakthroughs in the chemical structure theory. A family of species derived from this model is also presented.     

Preparation and properties of a new composite photocatalyst based on nanosized titanium dioxide

The use of photocatalysts supported on adsorbents is receiving substantial attention. Supporting TiO₂ with zeolites is found to be one of the best solutions to increase the efficiency of TiO₂-based photocatalysts. This work was focused on simple preparation of a TiO₂/Na-ZSM-5 composite catalyst by the solid state dispersion (SSD) method and its modification with an organic photosensitizer — polythiophene (PT). Using the XRD diffractometry, structure of the new composite catalyst was proved. Beside this composite catalyst, mechanical mixtures of TiO₂-based catalysts with Na-ZSM-5 zeolite were prepared. The efficiency of all five available photocatalysts (TiO₂, TiO₂-PT, mechanical mixture of TiO₂ + Na-ZSM-5, mechanical mixture of TiO₂-PT + Na-ZSM-5, and the modified SSD-PT composite) on photodegradation of 4-chlorophenol was compared. By measuring the formation of chloride ions and decreasing the 4-chlorophenol concentration at two different initial concentrations of 4-chlorophenol in the basic aqueous solution, the photoefficiency and adsorption properties of our photocatalysts were determined. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

基于氮氧自由基配体的锰和钴双核配合物的分子结构和磁性

合成了2个基于氮氧自由基配体且结构类似的双核配位化合物,其分子式分别为[Mn₂(hfac)₄(NIT-mo-pmy)₂](1)和[CO₂(hfac)₄(NIT-mo-pmy)₂](2),其中hfac=六氟乙酰丙酮,NIT-mo-pmy=2-(2-甲氧基-5′-嘧啶基)-4,4,5,5-四甲基咪唑啉基-3-氧-1-氧自由基。2个配合物均属于三斜晶系P1空间群,其双核配位单元进一步构筑为中心对称的平行四边形分子阵列。变温磁化率的测试表明,在2个配合物中,中心离子和氮氧自由基单元之间存在反铁磁交换作用。借助构效关系研究,分析了磁作用强度的差异。通过适当近似的磁化学模型,对Mn(Ⅱ)配合物的磁性行为进行了定量拟合,并与相关化合物磁作用强度进行了比对、分析。     

基于氮氧自由基配体的锰和钴双核配合物的分子结构和磁性

合成了2个基于氮氧自由基配体且结构类似的双核配位化合物,其分子式分别为[Mn₂(hfac)₄(NIT-mo-pmy)₂](1)和[Co₂(hfac)₄(NIT-mo-pmy)₂](2),其中hfac=六氟乙酰丙酮,NIT-mo-pmy=2-(2-甲氧基-5′-嘧啶基)-4,4,5,5-四甲基咪唑啉基-3-氧-1-氧自由基。2个配合物均属于三斜晶系P1空间群,其双核配位单元进一步构筑为中心对称的平行四边形分子阵列。变温磁化率的测试表明,在2个配合物中,中心离子和氮氧自由基单元之间存在反铁磁交换作用。借助构效关系研究,分析了磁作用强度的差异。通过适当近似的磁化学模型,对Mn (Ⅱ)配合物的磁性行为进行了定量拟合,并与相关化合物磁作用强度进行了比对、分析。     

A comparative DFT study of oxygen reduction reaction on mononuclear and binuclear cobalt and iron phthalocyanines

The oxygen reduction reaction (ORR) catalyzed by mononuclear and planar binuclear cobalt (CoPc) and iron phthalocyanine (FePc) catalysts is investigated in detail by density functional theory (DFT) methods. The calculation results indicate that the ORR activity of Fe-based Pcs is much higher than that of Co-based Pcs, which is due to the fact that the former could catalyze 4e^- ORRs, while the latter could catalyze only 2e^- ORRs from O₂ to H₂O₂. The original high activities of Fe-based Pcs could be attributed to their high energy level of the highest occupied molecular orbital (HOMO), which could lead to the stronger adsorption energy between catalysts and ORR species. Nevertheless, the HOMO of Co-based Pcs is the ring orbital, not the 3d Co orbital, thereby inhibiting the electron transfer from metal to adsorbates. Furthermore, compared with mononuclear FePc, the planar binuclear FePc has more stable structure in acidic medium and more suitable adsorption energy of ORR species, making it a promising non-precious electrocatalyst for ORR.     

Weak epitaxy growth and phase behavior of planar phthalocyanines on p-sexiphenyl monolayer film

We systematically investigated the weak epitaxy growth (WEG) behavior of a series of planar phthalocyanine compounds (MPc), i.e., metal-free phthalocyanine (H2Pc), nickel phthalocyanine (NiPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), iron phthalocyanine (FePc), cobalt phthalocyanine (CoPc), grown on a p-sexiphenyl ( p-6P) monolayer film by selected area electron diffraction (SAED) and atomic force microscopy (AFM). Two types of epitaxial relations, named as incommensurate epitaxy and commensurate epitaxy, were identified between phthalocyanine compounds and the substrate of the p-6P film. The tiny variation of the lattice constant of phthalocyanine compounds can result in different crystal orientations. The change rule of incommensurate and commensurate epitaxy was extracted. The tendency of commensurate epitaxy becomes weaker as the lattice constant b increases, while it gets stronger as the substrate temperature is elevated. Large size and continuous H2Pc films can be obtained by controlling the growth conditions. The WEG method is generally applicable in the whole family of planar phthalocyanine compounds and may be used to fabricate other high-quality organic films.     

平面双核酞菁钴中心离子价态及其性质研究

采用XPS方法确定了平面双核酞菁钴分子中两个Co离子的价态．讨论了平面双核酞菁钴分子中Co离子的价态与分子构形、配位性质、分子识别和分子整流特性等之间的联系．在平面双核酞菁钴分子中，两个Co离子具有不同的价态，Co(I)Pc—PcCo(Ⅲ)这种分子构形使得该分子表现出一些独特的性质．在配位化学上表现出一个Co(I)Pc—PcCo(Ⅲ)分子与三个配体形成配合物，在形成单分子膜时表现出分子的识别能力，Co(I)Pc—PcCo(Ⅲ)表现出分子整流特性。     

Sensors based on double-decker rare earth phthalocyanines

Phthalocyanines are interesting materials for sensing applications because their physicochemical properties are susceptible to be modified by the presence of certain molecules. Among the large family of the phthalocyanines, the sensing properties of double-decker phthalocyanines (which are sandwich-type complexes where a lanthanide metal is co-ordinated with two phthalocyanine rings) are of special interest due to their unique physicochemical properties. Their high intrinsic semiconductivity and their rich electrochemical and electrochromic behaviour, facilitate enormously the measurement of the changes in the physicochemical properties caused by the environment. In spite of their remarkable sensing behaviour, bisphthalocyanines have not been so extensively studied as sensitive materials as the parent monophthalocyanine compounds. This is due to the difficulty of the synthesis and purification processes, and to the fact that these compounds are not commercially available. In this paper, the sensing devices constructed using rare earth bisphthalocyanines are revised (including sensors foe electronic noses and electronic tongues) and their advantages discussed.     

Preparation and properties of nanosized fluorescent solid films based on a polyelectrolyte-surfactant complex with organic dyes

A procedure for preparing an organosoluble stoichiometric complex based on a cationic polyelectrolyte and an anionic surfactant is described. A method is proposed for forming monolayers at the water-air interface, along with conditions for preparing fluorescent nanosized solid films based on polyelectrolyte complex and organic dyes using the Langmuir-Blodgett (LB) method. The spectral and luminescent properties of the obtained films are investigated. It is established from the absorption and fluorescence spectra of LB films that electrostatic interaction between the molecules of polyelectrolyte complex and oxazine dyes results in dimer formation.     

Investigation on the photophysical processes in nanosized photocatalytic thin films using planar solid-state devices

The photophysical processes for three nanosized photocatalytic oxides, titanium dioxide (TiO₂) thin film, tin dioxide (SnO₂) thin film, and layered TiO₂/SnO₂ thin film, have been examined in planar solid-state devices. It is found that, for SnO₂ thin film, the dissociation of the photogenerated excitons can take place both on the film surface and inside the film, while for TiO₂ thin film, almost all excitons dissociate on the film surface. Such a difference is proposed to account for the higher photocatalytic activity of TiO₂ over SnO₂, since it is experimentally shown that the excitons dissociate in SnO₂ thin film as efficiently as they do in TiO₂ thin film. For layered TiO₂/SnO₂ thin film, when it is illuminated by a beam of UV light, it is suggested that there exists a local electrostatic field at the SnO₂ side of the interface, mainly formed by those holes efficiently photogenerated and then localized in SnO₂ thin film. The photo-induced local electrostatic field is believed to facilitate hole–electron separation on TiO₂ thin film and therefore increase the photocatalytic activity of the layered thin film over single TiO₂ thin film.     

Assembly models for nanosized growth nuclei of crystal structures

Different growth models of crystal structures are briefly considered. A metric model of layer-by-layer sectoral growth proposed in [1] is described along with its application for computer modeling of the assembly of nanosized crystal growth nuclei by clusterizing the unit cell content.     

Self-assembly of a cyclobutane beta-tetrapeptide to form nanosized structures

A beta-tetrapeptide made up of homochiral cyclobutane residues displays conformational bias in solution prompted by the formation of intramolecular hydrogen bonds. Moreover, this compound self-assembles to produce nanosized fibrils and, in some media, it also forms a gel. The combination of NMR, TEM, AFM, and theoretical calculations has proven to be very useful in obtaining insight into the details of these new structures.     

Preparation of planar chiral amino phenols based on the [2.2]paracyclophane backbone

The synthesis of various planar and central chiral secondary and tertiary amino phenols based on the [2.2]paracyclophane backbone is described. Planar chiral tertiary amino phenols are prepared by reductive amination of 5-formyl-4-hydroxy[2.2]paracyclophane (FHPC) with secondary amines. The reduction of imine and ketimine precursors, as well as the 1,2-addition to these compounds is also described.