Self-assembly of amphiphiles with terthiophene and tripeptide segments into helical nanostructures

We previously reported a class of tripeptide amphiphiles known as peptide lipids that self-assemble into one-dimensional nanostructures with superhelical twisting. The pitch of this supramolecular twisting is controlled directly through sterics in the molecular structure of hydrophobic segments. In this work we study the supramolecular behavior of these nanoscale helices by substituting with a terthiophene conjugated segment of potential electronic interest and also through variations in the stereochemistry of the tripeptide. This terthiophene peptide lipid was shown to self-assemble into one-dimensional helical nanofibers with a regular diameter of 9±1 nm and helical pitch of 65±6 nm, and also found to form hierarchical double- and triple-stranded helices, which could be associated with terthiophene J-aggregate interactions among fibers. For stereochemical effects, we compared four diastereomers in the tripeptide sequence using l-glutamic acid and l- and d-alanine residues to probe their ability to control supramolecular organization. Interestingly, we found by atomic force microscopy that the LLD diastereomers formed cylindrical nanofibers without any twisting, whereas LDD diastereomeric segments self-assembled into helical nanofibers with a pitch of 40±6 nm. LDL diastereomeric segments formed, on the other hand, aggregates without any regular shape. We propose that these profound effects of chirality with amino acid sequence are related to changes in the β-sheet sub-structure within the nanofibers.     

Synthesis and photovoltaic performances of 2,5-dioctyloxy-1,4-phenylenevinylene and terthiophene copolymers with di(p-tolyl)phenylamine and oxadiazole side groups

Three novel conjugated polymers (P1, P2, and P3), comprised of 2,5-dioctyloxy-1,4-phenylenevinylene and terthiophene derivatives with/without di(p-tolyl)phenylamine (TPAV) and oxadiazole (OXD) side groups, have been synthesized via the Witting-Horner reaction. The effect of TPAV and OXD side groups on the optical, electrochemical and photovoltaic properties has been investigated. It is found that the introduction of TPAV and OXD side groups to the backbone of P2 and P3 exhibits broader and stronger absorption than that of P1 without TPAV and OXD side groups. Photovoltaic cells have been fabricated with the as-synthesized polymers as the donors and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as the acceptor in a 1:4 weight ratio. The device based on P2 shows a maximum power conversion efficiency of 1.75% under simulated AM 1.5 G solar irradiation (100 mW/cm²).     

Cyanide bridged tetranuclear complex with a novel terthiophene based ligand

A new terthiophene based ligand (L = 3-(2-pryridyl)-5-(2,2′:5′,2″-terthien-3′-yl) pyrazole was synthesized. The reaction of Ni(BF₄)₂·6H₂O, L and nBu₄N[Fe(CN)₃tp^∗] (tp^∗ = tris(3,5-dimethylpyrazol-1-yl)borohyrdide) with NaBPh₄ in MeOH/acetone yielded a cyanide bridged tetranuclear complex [Fe₂Ni₂(CN)₆(tp^∗)₂(L)₄](BPh₄)₂ (1). The electrochemical properties of both 1 and L were investigated, and magnetic susceptibility measurements of 1 were conducted, revealing that ferromagnetic interactions were operative within the tetranuclear core.     

新型低聚噻吩衍生物的合成及其凝胶化性能研究

设计合成了一系列新型低聚噻吩衍生物N,N'-双十八烷基-5,5"-(2,2:5,2"-三噻吩)二酰胺[N,N'-distearyl-5,5"-(2,2:5,2"-terthiophene) dicarboxamide (DNC₁₈₃T)]、N,N'-双烷烃基-5,5"-(3,3"-双辛烷基-2,2:5,2"-三噻吩)二酰胺[N,N'-dialkyl-5,5"-(3,3"-dioctyl-2,2:5,2"-terthiophene)dicarbox-amide(DNC_nDOc3T,n=5,8,16,18)]及N,N'-双十八烷基-5,5-(3,3-双辛烷基-2,2:5,2":5",2-四噻吩)二酰胺[N,N'-distearyl-5,5-(3,3-dioctyl-2,2:5,2":5",2-tetrathiophene)-dicarboxamide(DNC₁₈DOc4T)].研究结果表明,DNC₁₈₃T和DNC₅DOc3T同有机溶剂不形成凝胶.DNC_nDOc3T(n=8,16,18)和DNC₁₈DOc4T能同几种有机溶剂形成透明、半透明或不透明的凝胶.通过测定凝胶随温度变化的红外光谱(IR)、核磁共振氢谱(¹HNMR)、紫外光谱(UV),揭示出形成有机低分子凝胶的驱动力不仅有分子间氢键,而且π-π相互作用也是一个非常重要的因素.偏光光学显微镜、扫描电子显微镜(SEM)显示出有机低分子凝胶呈三维网络结构.另外,DNC₁₈Doc3T/盐/氰基苯凝胶体系在电场作用下发生可逆的颜色.