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First- and second-generation dendritic porphyrins were synthesized by cascade polymer methodology. The second molecular hyperpolarizabilities (γ) of these dendritic porphyrins as well as 5,10,15,20-tetraphenylporphyrin were measured by the Z-scan technique at 800 nm using a mode-locked Ti:sapphire laser. The relationship between the various structures and their corresponding second molecular hyperpolarizabilities are explained on the basis of the oscillator strength of the Q band and the increasingly electron-rich microenvironment created by the dendritic branches around the porphyrin core.

In the aim to prepare thick porphyrin molecular wires, which is visible by atomic force microscopy (AFM), even on the rough surfaces of nanogap electrodes fabricated by electron beam lithography, dendrimer protected porphyrins whose two meso-positions are substituted with ethynyl groups. The porphyrin monomer was reacted with palladium catalyst to make oligomers. Analyses of them with time-of-flight mass spectroscopy (TOF-MS), gel-permeation-chromatography (GPC) revealed that the oligomers were distributed up to 16 mer, whose molecular weight was about 38 000 Daltons.

Static second hyperpolarizability (γ) of 1,4-phenylendiamine and 4,4'-diaminodiphenylamine in neutral and dicationic states are investigated as model systems of dendritic structure. Expansion of π-conjugation is found to significantly enhance the γ value of the neutral model system. Charged defect in the present system is found to have a remarkable influence on the magnitude and sign of static γ in the direction of π-conjugation.

We demonstrate that immobilization of a π-conjugated molecule containing a bipyridine moiety as a hydrogen bond acceptor on Au using a dendrimer-based template with 3,4-dihydroxybenzene moiety at the core as a hydrogen bond donor. The hydrogen bond interaction was used for the linkage between the conjugated molecule and the template to improve the method to fabricate single-molecule arrays we reported before.¹ Although the binding constant is small (K = 120 ± 20 M^-1) in CDCl₃, it was demonstrated that the dendrimer spacer serves as a template to isolate the π-conjugated molecule, and is removable simply with a CH₂Cl₂ rinsing by surface FTIR spectroscopy.

A newly designed fullerodendron was synthesized in good yield (84%) by the use of a Diels-Alder reaction of C₆₀ with an anthryl dendron. Interestingly, the fullerodendron acts as a new catalyst that uses oxygen and light to generate singlet oxygen (¹O₂). The dendron facilitates various types of singlet oxygenation reactions including ene reaction, Diels-Alder reaction, and oxidation of phenol and sulfide.

Carboxyl PAMAM dendrimer (3.5 generation) was covalently coupled onto amine modified glass surface to prepare a monolayer of high density functional linkers. Activation of the carboxyl PAMAM surface and the subsequent immobilization of antibodies resulted in a high density protein microarray as compared to linear carboxyl linker surface. In addition, fluorescent labeled cell lysate showed extremely low nonspecific adsorption to the PAMAM modified surface, comparable to inert PEG surface. Thus, the carboxyl PAMAM modified surface is ideal for the generation of high density protein arrays for the detection of dilute antigens with superior sensitivity.

Aggregation behaviors of phthalocyanine derivatives which have a dendritic structure were examined in an aqueous solution. We prepared the first- and second-generation dendrimers (WG1-PC and WG2-PC), having water-soluble substituents as a peripheral group, to be resolved in water. From spectroscopic measurement, WG2-PC acted in a monomeric manner, even in an aqueous solution, in contrast to WG1-PC, which exhibited spectra attributed to aggregation. This implies that a higher generation of water-soluble dendrimers can prevent a phthalocyanine core from forming an aggregation. The introduction of the second-generation dendrons to an aggregatable core may be effective to avoid self-aggregation and an undesirable deactivation process.

To mimic bacterial light-harvesting antenna complexes, a series of dendritic multiporphyrin arrays, nP_Zn-P_FB (n = 2, 4; cone-shaped dendrimers, n = 8, 16; star-shaped dendrimers), were synthesized and characterized by ¹H NMR and MALDI-TOF-MS spectroscopy. Photoinduced energy-transfer efficiency (Φ_ET) from peripheral Zn porphyrin (P_Zn) units to an inner core free-base porphyrin (P_FB) in the dendrimers was evaluated by fluorescence measurement. Both star- and cone-shaped multi-porphyrin arrays exhibited significantly high efficiency energy transfer from the photoexcited P_Zn units to the energy-accepting P_FB, where the star-shaped dendrimers, 8P_Zn-P_FB (94%) and 16P_Zn-P_FB (88%), had a slightly higher efficiency than those of the cone-shaped dendrimers, 2P_Zn-P_FB (92%) and 4P_Zn-P_FB (80%), respectively.

A dendritic shell can create a distinct micro-environment within its core. It also has the advantage of possessing unique photochemical, photophysical, electrochemical, and catalytic properties. Polyphenylene dendrons, which are characterized by their shape-persistent structures and out-of-plane twisted phenyl components, have previously been successfully attached to various functional groups. We have recently developed a convenient method for synthesizing a new type of porphyrazine that contains both flexible (linear) and more rigid (dendritic) groups. The synthesis of this completely aromatic and dendronic structure is unique in that it is based on a [2+4] Diels-Alder cycloaddition of tetraphenylcyclopentadienone to an ethynyl compound, followed by the elimination of carbon monoxide. In this study, tetrapyrazinoporphyrazinato metal and metal-free complexes were prepared by mixing 2,3-dicyano-5-polyphenylpyrazines with magnesium in n-butanol. The synthesized tetrapyrazinoporphyrazines were characterized by UV-visible spectroscopy, MALDI-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass) spectrometry, elemental analysis and ¹H NMR spectroscopy.

Phthalocyanines having hydrophilic or lipophilic dendrons were synthesized to investigate the efficiencies of singlet molecular oxygen (¹Δ_g) formation. The introduction of higher generation of dendrons to the central metal (Si) of phthalocyanine in vertical direction to their ring plane has resulted in the successful improvement in avoiding aggregate formation that resulted in efficient generation of ¹Δ_g even in water.

Multiple photosynthetic reaction centers have successfully been constructed using a supramolecular complex of zinc porphyrin dendrimer [D(ZnP)₁₆] with pyridylnaphthalenediimide (PyNIm) in benzonitrile. The apparent formation constant determined from the fluorescence quenching of the singlet excited state of porphyrin moieties by PyNIm is significantly larger than that determined from the UV-vis spectral change. This indicates that efficient energy migration occurs between the porphyrin units of the dendrimer prior to the electron transfer from the singlet excited state of zinc porphyrin to PyNIm. The charge-separated (CS) state has been successfully detected as the transient absorption spectrum in the laser flash photolysis. The CS lifetime of in the supramolecular complex of D(ZnP)₁₆ with PyNIm was determined to be 0.83 ms at 298 K.

Photoluminescent carbon dots (CDs) are synthesized and derived from carboxyl-modified PAMAM dendrimer precursor by a one-pot solvothermal method. The obtained CDs exhibit highly bright Yellow-emitting fluorescence with quantum yield of 62.6%. In practice, using their excellent photoluminescence and good compatibility, the CDs are processed with polymers for various fluorescent nanocomposites (such as film, microfiber and bulk hydrogel) and applied as light conversion materials for white LEDs.

This chapter will briefly introduce the molecular design, synthesis, structure and properties, characterisation method and applications of adaptive polymers. There are many smart and functional materials, and adaptive polymers are one such example. This book mainly focuses on adaptive polymers and textiles. First, some concepts will be suggested and definitions of adaptive polymers and textiles are reviewed. Following that, the characteristics, structures and potential applications of adaptive polymers will be summarised. Developing novel smart adaptive polymers and textiles are challenging, and some future trends are suggested at the end.

Boron-conjugated polymers are the most promising of the polymeric systems studied, especially since some polymer–drug conjugate therapies like PEGylated Doxorubicin have previously been licensed. While more research and insights are required for the most part, some studies are quite encouraging, particularly in terms of clinical translatability. FDA has approved a variety of nanoparticle delivery routes, with an emphasis on the intravenous route, which has advantages in the treatment of metastasized tumors. Because of their biodegradable and biocompatible behavior inside the human body, polymeric nanoparticles are garnering increased interest for the treatment of malignant gliomas. Over the years, a wide range of drugs have been synthesized to improve boron administration for boron neutron capture therapy (BNCT). Numerous small molecules were synthesized from natural products that provided a better tumor-to-blood ratio of boron in the in vivo studies. In the same way, many macromolecules have been synthesized with various secondary functions. This chapter will describe some of the dendrimers and nanoparticles developed for BNCT.

In the aim to prepare thick porphyrin molecular wires, which is visible by atomic force microscopy (AFM), even on the rough surfaces of nanogap electrodes fabricated by electron beam lithography, dendrimer protected porphyrins whose two meso-positions are substituted with ethynyl groups. The porphyrin monomer was reacted with palladium catalyst to make oligomers. Analyses of them with time-of-flight mass spectroscopy (TOF-MS), gel-permeation-chromatography (GPC) revealed that the oligomers were distributed up to 16 mer, whose molecular weight was about 38 000 Daltons.

Static second hyperpolarizability (γ) of 1,4-phenylendiamine and 4,4'-diaminodiphenylamine in neutral and dicationic states are investigated as model systems of dendritic structure. Expansion of π-conjugation is found to significantly enhance the γ value of the neutral model system. Charged defect in the present system is found to have a remarkable influence on the magnitude and sign of static γ in the direction of π-conjugation.

Nucleic acid based gene therapy holds great promise in the treatment of various diseases. However, the success of both DNA- and siRNAbased gene therapies depends critically on safe and efficient nucleic acid delivery systems. Owing to their well-defined structure and multivalent cooperativity, dendrimers have attracted particular attention as ideal nanocarriers for nucleic acid delivery. The present chapter highlights the current status of dendrimers as non-viral nanovectors for both DNA and siRNA delivery, focusing on the different dendrimers investigated for their delivery efficiency with respect to structural alterations in the view to developing safe and efficient nanovectors for gene therapy application.