He received his Ph.D. in 2003 from East China University of Science and Technology in the research group of Professor Yanlong Qian. His research interests include synthetic organic chemistry, organometallic chemistry (group IVB), polymer chemistry, and catalysis.

A series of novel m-arene-bridged salicylaldimine-based binuclear neutral nickel(II) complexes (2,4,6-(R 2 ) 3 C 6 H-1,3-[NdCH-4-X-6-R 1 C 6 H 2 ONi(Ph)(PPh 3 )] 2 (3a-i: R 1 , R 2 , X ) Me, Me, H (3a), t Bu, Me, H (3b), Me, Et, H (3c), t Bu, Et, H (3d), H, i Pr, H (3e), Me, i Pr, H (3f), t Bu, i Pr, H (3g), Ph, i Pr, H (3h), NO 2 , i Pr, NO 2 (3i), H, i Pr, NO 2 (3j)) are synthesized. The structure of complex 3h is further confirmed by an X-ray diffraction study showing that the two Ni centers adopt an unsymmetrical, distorted square planar geometry. In the presence or absence of the phosphine scavenger Ni(COD) 2 , complexes 3a-j show high catalytic activities for ethylene polymerization. The effect of substituents on ethylene polymerization is significant. The introduction of an electron-withdrawing group to the ligand framework improves the catalytic activity significantly. The influence of polymerization temperature, polymerization time, and catalyst concentration on the activities of ethylene polymerization is also investigated. Highly branched polyethylenes (46-127 branches per 1000 carbon atoms) with moderate molecular weights (M η ) (1.0-169) × 10 4 ) and narrow molecular weight distributions (M w /M n ) 2.3-2.4) are obtained by using complexes 3a-j as catalysts with or without a phosphine scavenger. In the presence of a polar solvent such as THF or Et 2 O, complex 3h polymerizes ethylene as a single-component catalyst. In comparison to the corresponding mononuclear Ni catalysts, the binuclear Ni catalysts generally show higher thermal stability, and complexes 3a, 3c, 3e, and 3f, which feature small R 1 substituents, are capable of acting as single-component ethylene polymerization catalysts.

Background Maize ( Zea mays L.) is one of the main agricultural crops with the largest yield and acreage in the world. However, maize germplasm is very sensitive to low temperatures, mainly during germination, and low temperatures significantly affect plant growth and crop yield. Therefore, the identification of genes capable of increasing tolerance to low temperature has become necessary. Results In this study, fourteen phenotypic traits related to seed germination were used to assess the genetic diversity of maize through genome-wide association study (GWAS). A total of 30 single-nucleotide polymorphisms (SNPs) linked to low-temperature tolerance were detected (−log10( P ) > 4), fourteen candidate genes were found to be directly related to the SNPs, further additional 68 genes were identified when the screen was extended to include a linkage disequilibrium (LD) decay distance of r 2 ≥ 0.2 from the SNPs. RNA-sequencing (RNA-seq) analysis was then used to confirm the linkage between the candidate gene and low-temperature tolerance. A total of ten differentially expressed genes (DEGs) (|log 2 fold change (FC)| ≥ 0.585, P < 0.05) were found within the set distance of LD decay ( r 2 ≥ 0.2). Among these genes, the expression of six DEGs was verified using qRT-PCR. Zm00001d039219 and Zm00001d034319 were putatively involved in ‘mitogen activated protein kinase (MAPK) signal transduction’ and ‘fatty acid metabolic process’, respectively, based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Thus, these genes appeared to be related to low-temperature signal transduction and cell membrane fluidity. Conclusion Overall, by integrating the results of our GWAS and DEG analysis of low-temperature tolerance during germination in maize, we were able to identify a total of 30 SNPs and 82 related candidate genes, including 10 DEGs, two of which were involved in the response to tolerance to low temperature. Functional analysis will provide valuable information for understanding the genetic mechanism of low-temperature tolerance during germination in maize.

The syntheses of two kinds of titanium(IV) complexes with mono-Cp and Schiff base as the mixed ligands are reported. These complexes are synthesized by the reaction of CpTiCl3 with the Schiff base lithium salt, and they are characterized by 1 H NMR, EA, IR, and MS. When activated by excess methylaluminoxane (MAO), all complexes are active for ethylene polymerization and ethylene/1-hexene copolymerization. 1/MAO shows 3 times as active as complex 7 (Cp2TiCl2) to the ethylene/1-hexene copolymerization, and the molecular weight of the copolymer obtained by 1/MAO is almost 2 times that of complex 3 and 5 times that of complex 7. Complex 1 combines the advantages of non-metallocene (complex 3) and metallocene (complex 7) to the ethylene polymerization and ethylene/1-hexene copolymerization.

A series of nitrogen-functionalized cyclopentadienylchromium complexes (1-9) have been synthesized, characterized, and then tested as catalyst precursors for olefin polymerization. The structures of complexes 1 and 5 show the nitrogen atom coordinated to the chromium atom, which is confirmed by X-ray crystallography. In the presence of MAO, the complexes exhibited high catalytic activities for the homopolymerization of ethylene and its copolymerization with 1-hexene. It also turned out that both the activity of ethylene polymerization and the incorporation of 1-hexene into the copolymer were highly affected by the substituents on the cyclopentadienyl fragment and bridge group. The effects of temperature variation and Al/Cr ratio on catalytic activity were also studied.

Background Ethylene promotes fruit ripening whereas 1-methylcyclopropene (1-MCP), a non-toxic antagonist of ethylene, delays fruit ripening via the inhibition of ethylene receptor. However, unsuitable 1-MCP treatment can cause fruit ripening disorders. Results In this study, we show that short-term 1-MCP treatment (400 nL•L − 1 , 2 h) significantly delays papaya fruit ripening with normal ripening characteristics. However, long-term 1-MCP treatment (400 nL•L − 1 , 16 h) causes a “rubbery” texture of fruit. The comparative transcriptome analysis showed that a total of 5529 genes were differently expressed during fruit ripening compared to freshly harvested fruits. Comprehensive functional enrichment analysis showed that the metabolic pathways of carbon metabolism, plant hormone signal transduction, biosynthesis of amino acids, and starch and sucrose metabolism are involved in fruit ripening. 1-MCP treatment significantly affected fruit transcript levels. A total of 3595 and 5998 differently expressed genes (DEGs) were identified between short-term 1-MCP, long-term 1-MCP treatment and the control, respectively. DEGs are mostly enriched in the similar pathway involved in fruit ripening. A large number of DEGs were also identified between long-term and short-term 1-MCP treatment, with most of the DEGs being enriched in carbon metabolism, starch and sucrose metabolism, plant hormone signal transduction, and biosynthesis of amino acids. The 1-MCP treatments accelerated the lignin accumulation and delayed cellulose degradation during fruit ripening. Considering the rubbery phenotype, we inferred that the cell wall metabolism and hormone signal pathways are closely related to papaya fruit ripening disorder. The RNA-Seq output was confirmed using RT-qPCR by 28 selected genes that were involved in cell wall metabolism and hormone signal pathways. Conclusions These results showed that long-term 1-MCP treatment severely inhibited ethylene signaling and the cell wall metabolism pathways, which may result in the failure of cell wall degradation and fruit softening. Our results reveal multiple ripening-associated events during papaya fruit ripening and provide a foundation for understanding the molecular mechanisms underlying 1-MCP treatment on fruit ripening and the regulatory networks. Electronic supplementary material The online version of this article (10.1186/s12870-019-1904-x) contains supplementary material, which is available to authorized users.

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