Design, Synthesis, Self-assembled Nanostructures And Organic Semiconductor Properties Of Porphyrinato/Phthalocyaninato Complexes

Organic semiconductors have attracted significant research interest for several decades due to these materials can potentially be fabricated very low cost, flexible and large-area organic electronic devices. Recently, owing to the unique electrical, optical and magnetic properties, associated with the intriguing intramolecularπ-πinteractions, porphyrin, phthalocyanine and their derivatives have been the focus of the most intensively studied small molecule organic semiconductor. Our research work is focused on design and synthesis of novel molecules, physical and chemisty properties, the Self-assembly of the materials, the applications of electronics functionality.1. Helical nano-structures self-assembled from dimethylaminoethyloxy-containing unsymmetrical octakis-substituted phthalocyanine derivativesThe self-assembling properties of metal free unsymmetrical 2,3,9,10,16,17,23-heptakis(butyloxy)-24-mono(dimethylaminoethyloxy)phthalocyanine H2{Pc(OC4H9)7[OC2H4N(CH3)2]} (1) and its zinc complex counterpart Zn{Pc(OC4H9)7[OC2H4N(CH3)2]} (2) in MeOH have been comparatively investigated by scanning electronic microscopy (SEM), X-ray diffraction (XRD) technique, and IR and UV-vis spectroscopy. Cooperation of the intermolecular hydrogen bonding/Zn-N coordination bonding withπ-πinteraction between neighboring phthalocyanine molecules due to the presence of one peripheral dimethylaminoethyloxy side chain for 1 and 2 results in nanostructures with different morphology including left- and right-handed helical ribbons as well as hollow nanotubes for 1 and nanowire bundles for 2. Electronic absorption spectroscopic results reveal the H-aggregate nature in all the nanostructures formed from both compounds 1 and 2, indicating the dominantπ-πinter-molecular interaction between phthalocyanine molecules. The IR and X-ray diffraction (XRD) results reveal a dimeric supramolecular structure formed through the intermolecular hydrogen bonding or Zn-N coordination bonding interaction between two molecules, which as the building block further packs into the target nanostructures depending onπ-πinteraction with the help of hydrogen bonding/Zn-N coordination bonding interaction between the dimeric supramolecular building blocks for 1 and 2. In particular, the morphological evolution of the nanostructures from helical ribbons to nanotubes has been clearly revealed during the self-assembly process of unsymmetrical phthalocyanine compound 1. In addition, the nanostructures self-assembled from both 1 and 2 were revealed to show good semiconducting properties with the conductivity in the range from 2.04 x 10-5 to 1.28 x 10-4 S m-1 in air due to the ordered one-dimensionalπ-πstacking enhanced by hydrogen bonding/metal-ligand coordination bonding interaction, which increases to 2.41×10-2-2.74×10-2 S m-1 after chemical doping with iodine.2. Morphology Controlled Surface-assisted Self-assembled Micro-tube Junctions and Dendrites of Metal Free Porphyrin-Based SemiconductorSolution-vapor annealing of drop-casting thin films of meso-5,10,15,20-tetra-n-decylporphyrin H2T(C10H21)4P deposited on SiO2 substrate and quartz lead to formation of well-defined self-assemblies. Their self-assembling properties in n-hexane vapor and chloroform vapor were comparatively investigated by scanning electronic microscopy (SEM), X-ray diffraction (XRD) technique, and IR and UV-vis spectroscopy. Inter-molecularπ-πinteraction in cooperation with the van der Waals interaction of metal free porphyrin and solvent-solute interaction lead to the formation of micro-leaves and micro-tube dendrites in n-hexane vapor and chloroform vapor, respectively. Electronic absorption spectroscopic data on the self-assembled microstructures reveal the J-aggregate nature in both the micro-leaves and micro-tube dendrites. However, the difference in the shift of the Soret and Q bands for the two kinds of aggregates relative to corresponding solution absorption bands indicates the dependence of the solvent-porphyrin molecular interaction during the annealing self-assembly process, which counterbalances the intermolecular interactions particularly the hydrophobic interaction between side chains. IR and XRD results clearly reveal the higher molecular ordering nature of micro-tube dendrites than micro-leaves, further confirming the effect of the solvent on tuning the inter-molecular interaction and in turn the molecular packing mode in aggregates of porphryin compound. The present result appears to represent the first example of orderly micrometer-sized tube junctions and dendrites of porphyrin prepared through a self-assembly process, providing an effective and new method towards the synthesis of complicated nano-tubular structures. In addition, micrometer-sized leaves and tube dendrites were revealed to show good semiconductor feature.3. Synthesis, Characterization, and OFET Properties of Amphiphilic Mixed (Phthalocyaninato)(Porphyrinato) Europium(Ⅲ) ComplexesAmphiphilic mixed (phthalocyaninato)(porphyrinato) europium(III) triple-decker complexes Eu2[Pc(15C5)4]2[T(C10H21)4P] (1) and Eu2[Pc(15C5)4]2[TPOPP] (2) [H2Pc(15C5)4=2,3,9,10,16,17,23,24-tetrakis(15-crown-5)phthalocyanine; H2T(C10H21)4P=/meso-5,10,15,20-tetra-n-decylporphyrin, H2TPOPP= mes0-5,10,15,20-tetrakis(4-pentyloxyphenyl)porphyrin] were designed and synthesized by the raise-by-one-story method. These novel sandwich triple-decker complexes have been characterized by a wide range of spectroscopic methods and electrochemically studied. Highly ordered films were fabricated by the Langmuir-Blodgett technique into organic field effect transistors (OFETs). The devices display good OFET performance with the carrier mobility in the range of 0.03-0.78 cm2 V-1 s-1. As expected, the devices show a low threshold voltage range from-1.19 to-4.34 V. The mobility of compound 1 reaches 0.78 cm2 V-1 s-1, which amounts the highest one achieved so far for LB film-based OFETs due to the narrow energy gap (1.04 eV) of this compound.4. Organic Field Effect Transistors Based on 5,10,15,20-Tetrakis (4-pentyloxyphenyl)porphyrin Single CrystalDiffusion of methanol into the chloroform solution of metal free 5,10,15,20-tetrakis (4-pentyloxyphenyl)porphyrin H2TPOPP yields large single crystals with length as long as 1.5 mm, which allow the fabrication of single crystal-based organic field effect transistors (OFET). These single crystal-based devices were revealed to exhibit relatively good OFET performance with the carrier mobility for hole of 0.0018 cm2 V-1 s-1 and current modulation of 104. In addition to confirming the tetrappyrole nature, single crystal X-ray diffraction analysis also reveals the planar two-dimensional supramolecular structures formed via porphyrin molecules in the head-to-tail manner through C-H…O interaction between oxygen atom and pyrrole hydrogen atom as well as p(O)-π(phenyl) interaction between the meso-attached phenyloxy groups of neighboring porphyrin molecules in the single crystal. This results in effective intermolecular interaction due to the significant participation of phenyloxy groups to the HOMO of the central porphyrin core as revealed by density functional theory (DFT) analysis and in turn is responsible for the relatively good OFET performance in terms of carrier mobility for hole in the direction parallel to the aromatic porphyrin ring. Density functional theory (DFT) calculation also reproduces the experimentally revealed carrier mobility for hole in the single crystal of H2TPOPP. The present work, representing our continuous efforts in understanding the relationship between molecular structure, crystal packing, and OFET performance of tetrapyrrole organic semiconductors, will be helpful for attracting further research interest over the semiconducting properties of tetra(aryl)porphyrin compounds for OFET applications.