Synthesis, Self-assembly Properties And Chiral Information Transfer At The Molecular Level Of Optically Active Phthalocyaninato Complexes

Chirality is one of the most fascinating and complicated features commonly found in nature. Inspired by the elegance of biological supramolecular structures, numerous artificial helical supramolecular structures with controlled helicity have been developed depending on various non-covalent interactions. Owing to the unique optical, electrical, and properties, associated with the intriguing intramolecularπ～πinteractions, porphyrins, phthalocyanines, as well as sandwich type rare complexes, as a novel functional materials, have been expected to be widely potential application in materials science, such as in molecular electronics, molecular information storage, and nonlinear optics, etc. Recently, it is significantly interested in ordered supramolecular aggregate and nanoscale assembly fields. However, it must be pointed out that self-assembly of chiral functional molecules into a prerequisite nanostructure with desirable dimension and morphology via controlling and optimizing inter-molecular interaction still remains a great challenge for chemists and material scientists. In order to extensively investigate supramolecular aggregation behaviors and supramolecular assembly methodology of chiral phthalocyninato complexes, in this thesis a series of chiral phthalocyanine derivatives are selected, and some modern measuring techniques were performed to examine their aggregate structures, morphologies and nanostructures. Our research work has been focused on the following respects:1. Synthesis and Novel Hollow Sphere Nanostructures of Optically Active Metal-free PhthalocyanineNovel optically active metal-free phthalocyanine (1) decorated with four octyl chains linked via binaphthyl units to the phthalocyanine ring was designed and prepared. This new compound was characterized by a wide range of spectroscopic methods in addition to elemental analysis. By employing a solution injection method, both (R)-and (S)-enantiomers self-assemble into nano-particles. Surprisingly, with the addition of small amount of cetyltrimethylammonium bromide (CTAB), nanostructures with hollow sphere morphology were formed. The hollow spherical structure was determined by transmission electronic microscopy (TEM) and scanning electronic microscopy (SEM). X-ray photoelectron spectroscopy (XPS) together with FT-IR spectra indicates the supramolecular structures formed from the metal-free phthalocyanine molecules. Low-angle X-ray diffraction (XRD) reveals the stacked phthalocyanine molecules with a face-to-face configuration in the nanoscale hollow spheres formed with the help of CTAB surfactant. The formation of H-aggregates in the nanoscale hollow spheres is further confirmed by electronic absorption spectroscopic result. This work, representing the first example of controllable organic nanostructures with hollow sphere morphology fabricated from phthalocyanine compound, provides an effective method towards phthalocyanine nano-hollow spheres.2. Helical Fibrous Nano-structures Self-assembled from Metal Free Phthalocyanine Bearing Four Peripheral Chiral Menthol Moieties(D)-and (L)-enantiomers of a novel metal free 2(3),9(10),16(17),23(24)-tetrakis(2-isopropyl-5-methylcyclohexoxyl)phthalocyanine (1) with four chiral menthol units attached at the peripheral positions of phthalocyanine ligand have been designed, synthesized, and characterized. Neither (D)-1 nor (L)-1 enantiomer displays CD signal in the Soret and Q absorption region of phthalocyanine ligand, indicating the lack of effective chiral information transfer from the chiral menthol tails to phthalocyanine chromophore at the molecular level. Their self-assembly properties were systematically studied by circular dichroism (CD) spectra, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atom force microscopy (AFM) technique. Despite the composition of four constitutional stereoisomers of each enantiomer due to the random location of four chiral menthol substituents at the peripheral positions of phthalocyanine ring, cooperation of inter-molecularπ-πinteraction between phthalocyanine rings with chiral discrimination of chiral side chains of (D)-1 and (L)-1 enantiomer induces the formation of one-dimensional helices with left-handed and right-handed helical molecular arrangement, respectively, according to the CD spectroscopic result. This reveals the effective chiral information transfer from the chiral menthol tails to phthalocyanine chromophore at the supermolecular level. The formed one-dimensional helices twist around each other to maximize the van der Waals interaction, leading to the formation of highly ordered fibrous nano-structures with both right-handed and left-handed helicity according to the staggering angles between the neighboring phthalocyanine molecules, indicating the hierarchical formation of these fibrous nano-structures. Careful inspection over these nano-fibers indicates the majority of nano-fibers with right-handed and left-handed helicity formed from (D)-1 and (L)-1 enantiomer, respectively, with the ratio of ca.1.3-1.4:1 among all the fibrous nano-structures obtained. Electronic absorption spectroscopic and X-ray diffraction (XRD) results reveal the H-aggregate nature of these nano-fibers. The present result, representing part of our continuous effort towards preparation of self-assembled nano-structures with helical morphology through molecular design and synthesis, will be helpful on providing new insight into chiral information transfer and expression for synthetic conjugated systems at supermolecular level.3. Tuning the Morphology of Self-Assembled Nano-structures of Phthalocyaninato Zinc Complex Bearing Two Non-peripheral binaphthyl Units Self-assembly of functional organic molecules into well-defined organized nano-structures has recently attracted considerable research interest due to their versatile applications in nanoscience and nanotechnology. On the basis of different non-covalent interactions, a wide variety of nano-structures such as wires, belts, vesicles, and tubes have been fabricated from various functional molecules. For example, hollow spheres represent an appealing class of nano-structures due to their many potential applications in drug delivery, chemical storage, light filters, chemical catalysis, and as template for preparing functional architectural composite materials. Due to their unique planar and rigid molecular geometry and aromatic electronic feature delocalized over the molecular frame, phthalocyanines exhibit intriguing, peculiar, and tunable spectroscopic, photophysical, photochemical, and assembly properties. By virtue of these excellent features, phthalocyanines have received extensive research interests as ideal building blocks for the construction of non-covalent linked supramolecular assemblies with motivation for preparation of molecular-based electronic and optical devices such as electronic wires, switches, electroluminescence devices, field-effect transistors, and photovoltaic devices. Despite of the accessibility to a rich toolbox of noncovalent interactions, it still remains a great challenge for chemists and material scientists to understand the effect of synergistic interplay of different non-covalent interactions on controlling and tuning the desirable dimension and morphology of organic self-assembled nano-structures. In the present paper, we comparatively studied the self-assembly properties of phthalocyaninato zinc complex Zn{Pc(OBNP)2} with or without equal amount of DABCO. Comparative investigation results reveal that besides theπ-πinteraction, cooperation of metal-ligand coordination bonding lead to different molecular packing information and in turn different nano-structure morphology in the self-assembly process. Intermolecularπ-πinteraction of phthalocyaninato zinc complex Zn{Pc(OBNP)2} leads to the formation of nano-scale hollow spheres. Additional dominant Zn-NDABCO coordination bond between the nitrogen atom of DABCO molecule and the zinc center of the phthalocyaninato zinc molecule, together withπ-πinteraction leads to the formation of nano-belts for this complex, indicating the effect of synergistic interplay among non-covalent interactions such asπ-πinteraction and metal-ligand coordination bonding in controlling and tuning the morphology of self-assembled nano-structures of phthalocyanine compounds. The present study represents part of our continuous efforts towards understanding the synergistic interplay between non-covalent interactions on controlling and tuning the morphology of self-assembled nano-structures of phthalocyanine derivatives, and provides information helpful on preparing self-assembled nano-structures with controlled molecular packing conformation and morphology through molecular modification. Owing to the rich optical, electrical, and chemical properties of phthalocyanine derivatives, they are believed to be helpful in opening new possibilities for construction of molecular-based nano-electronics and nano-optoelectronics.4. Optically Active Homoleptic Bis(phthalocyaninato) Rare Earth Double-Decker Complexes Bearing Peripheral Chiral Menthol Moieties:Effect ofπ-πInteraction on the Chiral Information Transfer and Expression at the Molecular Level(D)-and (L)-enantiomers of a series of optically active homoleptic bis(phthalocyaninato) rare earth double-deckers with four chiral menthol moieties at the peripheral positions of phthalocyanine ligand, M(Pc*)2 [Pc*= 2(3),9(10),16(17),23(24)-tetrakis(2-isopropyl-5-methylcyclohexoxyl)phthalocyanine; M= Eu (1), Y (2), Lu (3)] have been designed and prepared by treating (D)-or (L)-4-(2-isopropyl-5-methylcyclohexoxyl)-1,2-dicyanobenzene with the corresponding M(acac)3·nH2O (acac=acetylacetonate) in the presence of organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in refluxing n-pentanol. For the purpose of comparative study, heteroleptic bis(phthalocyaninato) europium analogues (D)-and (L)-Eu(Pc)(Pc*) (4) as well as the unsubstituted homoleptic bis(phthalocyaninato) europium counterpart Eu(Pc)2 (5) were also prepared. The novel synthesized bis(phthalocyaninato) rare earth double-deckers have been characterized by a wide range of spectroscopic methods including MS,1H NMR, IR, and electronic absorption spectroscopic measurements in addition to elemental analysis. In contrast to the findings that no CD signal was detected in the absorption region for the monomeric metal free (D)-and (L)-2(3),9(10),16(17),23(24)-tetrakis(2-isopropyl-5-methylcyclohexoxyl)phthalocyanine, observation of the CD signal in the menthol absorption region of 4 reveals the significant effect of intense intra-molecularπ-πinteraction on intensifying the asymmetrical perturbation of the chiral menthol units and resulting in the chiral information expression by menthol moieties of 4 at molecular level despite the lack of CD signal in the Soret and Q absorption region of phthalocyanine ligand. This is further supported by the optical activity for homoleptic bis(phthalocyaninato) rare earth double-deckers M(Pc*)2 (1-3) revealed even in the Soret and Q absorption region of phthalocyanine ligand according to the CD spectroscopic result. Along with the increase in the chiral menthol substituent number, the further intensified asymmetrical perturbation induces the effective chiral information transfer from the peripheral chiral menthol side chains even to the phthalocyanine chromophore of 1-3, indicating the effect of chiral substituent number on the chiral information transfer and expression at the molecular level. In addition, their electrochemical properties have also been comparatively investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV).We also report the preparation and characterization of the first optically active mixed (phthalocyaninato)(porphrinato) rare earth complexes [HMⅢ{Pc(OBNP)2}(TClPP)] (M=Y, Eu) (1,2), Scheme 1. To enhance the asymmetric perturbation to the tetrapyrrole chromophores in the sandwich-type mixed (phthalocyaninato)(porphyrinato) rare earth double-decker molecules through dipole-dipole interaction, aromatic chiral binaphthayl units were introduced onto the non-peripheral positions of phthalocyanine ring. In addition to electronic absorption and MCD spectroscopic results, CD technique reveals obvious different spectroscopic feature of these mixed ring rare earth double-decker compounds in different solvent. On the basis of time-dependent density functional theory (TDDFT) calculation results on the yttrium species (S)-[YⅢ{Pc(OBNP)2}(Por)]- in terms of different rotation angle between the two macrocyclic ligands in the double-decker molecules, different electronic absorption and CD spectroscopic feature of (S)-[HYⅢ{Pc(OBNP)2}(TClPP)] in DMF and CHCl3 was well reproduced, revealing the solvent-dependent nature on the molecular conformation of mixed ring rare earth double-decker complexes. The present work reveals the change in optical spectroscopic spectra of mixed (phthalocyaninato)(porphyrinato) rare earth complexes along with solvent change from DMF to CHCl3 due to the change in the double-decker molecular conformation associated with different interaction between double-decker and solvent molecules. This, to the best of our knowledge, represents the first effort on understanding the nature of optical spectroscopic change of bis(tetrapyrrole) metal complexes depending on solvent.