A series
of three-dimensional geometry 9,10-dihydro-9,10-ethanoanthracene-11,12-diimines
(L1–L4) and their nickel(II) dibromide complexes (C1–C4)
were synthesized and characterized. The nickel complexes C1–C4,
with three-dimensional geometry, exhibited very high activities for
norbornene (NB) homopolymerization with only B(C6F5)3 as cocatalyst,: for C2 even up to 5.53 ×
107 g of polymer/((mol of Ni) h). To investigate the activation
of polar monomer, complexes C2 and C3 were selected for copolymerization
of NB and 5-norbornene-2-yl acetate (NB-OCOMe) in relatively high
activities (1.6–5.8 × 105g of polymer/((mol
of Ni) h)) and high molecular weights ((0.2–2.8) × 105 g/mol) as well as narrow molecular weight distributions (MWD
< 2 for all polymers) depending on the variation of feed ratios.
The reactivity ratios of the NB and NB-OCOMe monomers for C2/B(C6F5)3 system by the Kelen–Tüdös
method were determined to be r
NB‑OCOMe = 0.05 and r
NB = 6.72, respectively.
Moreover, the mechanism of polymerization catalyzed by the novel three-dimensional
geometry nickel(II) complexes was presented and supported by an end
group analysis of the polymer and density functional theory (DFT)
calculations of the reaction. The substituent effect of the catalysts
and the interaction between Ni2+ and NB were discussed,
and the results showed that α-diimine nickel complexes with
greater steric hindrance and smaller HOMO–LUMO gaps could achieve
higher reactivity.
Photoluminescent fullerene nanoparticles/nanofibers have potential applications in bioimaging. A novel fluorescent nanofibrous material, consisting of fullerene nanoparticles and poly(L-lactide) (PLLA), was fabricated via a simple electrospinning method, and the composite nanofibers were characterized by various techniques such as scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), and transmission electron microscopy (TEM). The nanofibers were uniform, and their surfaces were reasonably smooth, with the average diameters of fibers ranging from 300 to 600 nm. The fullerene nanoparticles were encapsulated within the composite nanofibers, forming a core-shell structure. The nanofiber scaffolds showed excellent hydrophilic surface due to the addition of water-soluble fullerene nanoparticles. The composite nanofibers used as substrates for bioimaging in vitro were evaluated with human liver carcinoma HepG2 cells, the fullerene nanoparticles signal almost displayed in every cell, implying the potential of fluorescent fullerene nanoparticles/PLLA nanofibers to be used as scaffolds for bioimaging application.
A series of three-dimensional geometry 9,10-dihydro-9,10-ethanoanthracene-11,12-diimine methyl palladium chloride complexes were synthesized and characterized. These three-dimensional geometry a-diimine palladium complexes exhibited high activities toward the homopolymerization of norbornene and copolymerization of norbornene with 5-norbornene-2-carboxylic acid methyl ester in the presence of B(C 6 F 5 ) 3 . It was observed that the palladium-halogen bond of the complexes could be effectively activated by B(C 6 F 5 ) 3 . The activation mechanism was clarified by the end group analysis of the polymer, which provided a new pathway for the activation of palladium complexes. Meanwhile, the palladium catalysts with a three-dimensional geometry on the backbone were found to show a good thermal stability and afford a high incorporation of the polar monomer in norbornene polymerization. Moreover, the a-diimine palladium complexes with a large steric hindrance or strongly electron-donating group on the aryl ring of ligands could achieve a higher reactivity.
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