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Gossypium hirsutum (upland cotton) is one of the most economically important crops worldwide, which has experienced the long terms of evolution and domestication process from wild species to cultivated accessions. However, nucleotide evolution, domestication selection, and the genetic relationship of cotton species remain largely to be studied. In this study, we used chloroplast genome sequences to determine the evolutionary rate, domestication selection, and genetic relationships of 72 cotton genotypes (36 cultivated cotton accessions, seven semi-wild races of G. hirsutum , and 29 wild species). Evolutionary analysis showed that the cultivated tetraploid cotton genotypes clustered into a single clade, which also formed a larger lineage with the semi-wild races. Substitution rate analysis demonstrated that the rates of nucleotide substitution and indel variation were higher for the wild species than the semi-wild and cultivated tetraploid lineages. Selection pressure analysis showed that the wild species might have experienced greater selection pressure, whereas the cultivated cotton genotypes underwent artificial and domestication selection. Population clustering analysis indicated that the cultivated cotton accessions and semi-wild races have existed the obviously genetic differentiation. The nucleotide diversity was higher in the semi-wild races compared with the cultivated genotypes. In addition, genetic introgression and gene flow occurred between the cultivated tetraploid cotton and semi-wild genotypes, but mainly via historical rather than contemporary gene flow. These results provide novel molecular mechanisms insights into the evolution and domestication of economically important crop cotton species. [ABSTRACT FROM AUTHOR]

Pinus L. is the largest genus of conifers and provides a classical model for studying species divergence and phylogenetic evolution by gymnosperms. However, our poor understanding of sequence divergence in the whole plastid genomes of Pinus species severely hinders studies of their evolution and phylogeny. Thus, we analyzed the sequences of 97 Pinus plastid genomes, including four newly sequenced genomes and 93 previously published plastomes, to explore the evolution and phylogenetic relationships in the genus Pinus. The complete chloroplast genomes of Pinus species ranged in size from 109 640 bp (P. cembra L.) to 121 976 bp (P. glabra Walter), and these genomes comprised circular DNA molecules in a similar manner to those of most gymnosperms. We identified 9108 repeats where most of the repeats comprised the dispersed type with 3983 (44%), followed by tandem repeats with 2999 (33%), and then palindromic repeats with 2126 (23%). Sixteen divergence hotspot regions were identified in Pinus plastid genomes, which could be useful molecular markers for future population genetics studies. Phylogenetic analysis showed that Pinus species could be divided into two diverged clades comprising the subgenera Strobus (single needle section) and Pinus (double needles section). Molecular dating suggested that the genus Pinus originated approximately 130.38 Mya during the late Cretaceous. The two subgenera subsequently split 85.86 Mya, which was largely consistent with the other molecular results based on partial DNA markers. These findings provide important insights into the sequence variations and phylogenetic evolution of Pinus plastid genomes. [ABSTRACT FROM AUTHOR]

We obtained a binuclear Gd(III) complex [Gd2(L1)2(NO3)4] (1, HL1 = (E)-2-(2-(pyridin-2-ylmethyleneamino)ethoxy)ethanol) by reacting N2O2-tetradentate chelating ligand HL1 with Gd(NO3)3·6H2O at solvothermal temperature of 100 °C. Time-dependent high-resolution electrospray ionization mass spectrometry (HRESI-MS) followed the formation of 1 and revealed it's the assembly mechanism: HL1 → Gd(L1) → Gd2(L1)2. When we used the NO2-tridentate chelating ligand HL2 (HL2 = 2-(2-aminoethoxy)ethanol) under the same reaction conditions, we obtained an "hourglass-like" nonanuclear Gd(III) cluster [Gd9(L2)8(μ3-OH)8(μ4-O)2(NO3)8]·2CH3OH·H2O (2). Their assembly mechanism was proposed: HL2 → Gd(L2) → Gd2(L2)2 → Gd3(L2)3 → Gd4(L2)4 → Gd5(L2)4 → Gd9(L2)8. Most notably, when we used the NO-bidentate chelate ligand HL3 (HL3 = picolinic acid), we obtained a dodecanuclear Gd(III) cluster [Gd12(L3)8(OH)16(NO3)8(OH)4(H2O)4]·22CH3OH·25CH3CN (3) under the same reaction conditions. We found that the formation process of cluster 3 involved two different and mutually interfering self-assembly processes, namely, multitemplate-induced assembly (HL3 → Gd(L3) → Gd2(L3)2 → Gd12(L3)8) and stepwise assembly (HL3 → Gd(L3) → Gd2(L3)2 → Gd3(L3)2 → Gd4(L3)2 → Gd5(L3)2 → Gd6(L3)2 → Gd12(L3)8). [ABSTRACT FROM AUTHOR]

The most effective way to understand reaction mechanisms and kinetics is to identify the reaction intermediates and determine the possible reaction patterns. The influencing factors that must be considered in the self-assembly of clusters are the type of ligand, metal ion, coordination anion and the pH of the solution. However, changes in ligand substituents resulting in different self-assembly processes to obtain different types of structures are still very rare, especially with –H and –CH3 substituents, which do not exert significant steric hindrance effects. In this study, planar mononuclear Ni(L1)2 (L1 = 2-ethoxy-6-(iminomethyl)phenol) was dissolved in methanol and combined with Dy(NO3)3·6H2O for 48 h at room temperature to obtain a butterfly-like Ni2Dy2 cluster ([Dy2Ni2(L1)4(CH3O)2(NO3)4], 1). The Dy(III) ions in cluster 1 are in an O8N coordination environment, and the Ni(II) ions are in an O5N coordination environment. High-resolution electrospray ionization mass spectrometry (HRESI-MS) was used to track species changes during the formation of cluster 1. Six key intermediate fragments were screened, and the self-assembly mechanism was proposed as Ni(L1)2 → HL1 + NiL1 → DyL1/Ni(L1)2′ → DyNi(L1)2 → Dy2Ni2(L1)4. Through this assembly mechanism, we found that Ni(L1)2 was first cleaved into HL1 + NiL1 and then further assembled to obtain 1. Another butterfly-like tetranuclear heterometallic cluster ([Dy2Ni2(L2)4(CH3O)2(NO3)4], 2) was obtained using planar mononuclear Ni(L2)2 (L2 = (E)-2-ethoxy-6-((methylimino)methyl)phenol) with –CH3 substitution on the nitrogen atom under the same reaction conditions. The structural analysis of cluster 2 showed that the Dy(III) ions are in an O9 coordination environment, and the Ni(II) ions are in an O4N2 coordination environment. HRESI-MS was used to trace species changes during the formation of 2, and the assembly mechanism was proposed as Ni(L2)2 → DyNi(L2)2 → Dy2Ni(L2)2 → Dy2Ni2(L2)4. Analysis of the assembly mechanism of 2 showed that Ni(L2)2 was twisted during the reaction, and its coordination point was exposed to capture the Dy(III) ions. Finally, Dy(NO3)3·6H2O was replaced with NaN3 to obtain a [Ni2Na2(L2)4(N3)4] cluster (3) under the same reaction conditions and verify the above-mentioned torsion step. HRESI-MS was also used to trace the assembly process, and the assembly mechanism was proposed as Ni(L2)2 → NiNa(L2)2 → NiNa2(L2)2 → Ni2Na2(L2)4. Herein, the effect of interference from substitution and the regulation self-assembly process were discovered in the formation of 3d–4f heterometallic clusters, and different types of coordination clusters were obtained. [ABSTRACT FROM AUTHOR]

The formation of high-nuclearity clusters of lanthanide usually involves many complicated self-assembly processes. Thus, tracking the formation process is extremely difficult and research on the assembly mechanism is very rare. In this study, a Dy-exclusive nanocluster containing vertex-sharing [Dy4(μ3-OH)4] cubanes, denoted as [Dy12(L)8(OH)16(CH3O)8(H2O)8]·(CH3O)4 (Dy12, L = quinoline-2-carboxylate), was designed and synthesized from L and DyCl3·6H2O. Eight quinoline-2-carboxylate ligands were encapsulated on the periphery of the Dy12 cluster, which served to stabilize the core. The high stability of the Dy12 cluster core was further confirmed by high-resolution electrospray-ionization mass spectrometry (HRESI-MS). With increased ion-source energy, only CH3O− and OH− bridging ligands were replaced inside the Dy12 cluster. Notably, eight intermediate fragments were successfully observed from the Dy12 cluster formation by time-dependent HRESI-MS. First, ligand L captured Dy3+ to give Dy1, which further formed Dy2 through μ2-O bridging. The Dy12 cluster was constructed in one step with four Dy2 and four Dy3+ as templates: L → Dy1→ Dy2→ Dy12. Moreover, a series of Dy3–Dy6 fragment peaks with relatively weak intensities were observed, and an alternative stepwise-assembly route was proposed: L → Dy1→ Dy2→ Dy3→ Dy4→ Dy5→ Dy6→ Dy12. On comparing the two different assembly methods, the multitemplate guided assembly formed Dy12 was found to be dominant. To the best of our knowledge, this study was the first to propose the involvement of two self-assembly mechanisms in the construction of lanthanide clusters, as further confirmed by HRESI-MS. Magnetic studies further showed that Dy12 clusters exhibited field-induced single-molecule magnet behavior. [ABSTRACT FROM AUTHOR]

Metal nanoclusters have a certain rigidity due to their specific coordination patterns and shapes; thus, they face extreme difficulty in folding into a specific direction to form a double‐helix structure and in further interconnecting to form metal–helix frameworks (MHFs). To date, no MHFs have been produced by the formation of heterometallic clusters. Selecting the appropriate "bonding molecules" to bond metal nanoclusters in a specific multiple direction is one of the most effective strategies for designing synthetic MHFs. In this study, we realized for the first time the control of different orientations of μ3‐NO3− to join heterometallic clusters (Cu10Dy2) and subsequently form a left‐handed double helix chain, which further joins to form MHFs. In the structure of the MHFs, four different directions of bridging μ3‐NO3− exist, three of which are involved in the linkage of the double‐helix chain. Each μ3‐NO3− is connected to three adjacent Cu10Dy2. Herein, we extend a new method for designing synthetic double‐helix structures and MHFs, thereby further laying the foundation for the development of similar DNA double‐helix structures and nucleic acid secondary structures in vitro. [ABSTRACT FROM AUTHOR]

The organic ligands 5,7-dibromo-2-methyl-8-quinolinol (L1), 1,10-phenanthroline (L2), and 5,7-dichloro-2-methyl-8-quinolinol (L3) were used to react with Dy(NO3)3·6H2O under solvothermal conditions at 80 °C to obtain the complexes [Dy(L1)3(H2O)] (1), [Dy(L2)2(NO3)3] (2), and [Dy(L3)3(H2O)] (3), respectively. The reaction of L1 and L2 with lanthanide(iii) nitrate salts in the presence of triethylamine as a base afforded four mononuclear complexes, namely, [Ln(L1)2(L2)(NO3)] [Ln = Dy (4), Ho (5), Er (6), and Tb (7)]. Complexes 1 and 2 emitted yellow-green and red light under excitation with light of a certain wavelength. Interestingly, 4–7 exhibited a superimposition of the luminescence of 1 and 2. To our knowledge, this is the first example of the use of different organic light-emitting ligands to adjust the fluorescence of Ln(iii) complexes. Moreover, the series of complexes [Ln(L3)2(L2)(NO3)] [Ln = Dy (8), Ho (9), Er (10), and Tb (11)] were also obtained under the same conditions by replacing L1 with L3. In the way that was expected, 8–11 exhibited a superimposition of the luminescence of 2 and 3. Density functional theory (DFT) calculations of electron cloud density showed that the electron cloud densities of complexes 4 and 8 are mainly concentrated in the quinoline rings. Furthermore, analysis of the molecular ion peaks of complexes 4–11 obtained by electrospray mass spectrometry (ESI-MS) showed that only the 1,10-phenanthroline ligand was discovered to dissociate in the solution state. Magnetic measurements of the Dy-containing complexes revealed features of field-induced single-ion magnet behavior. [ABSTRACT FROM AUTHOR]

Cotton is one of the most economically important fiber crop plants worldwide. The genus Gossypium contains a single allotetraploid group (AD) and eight diploid genome groups (A-G and K). However, the evolution of repeat sequences in the chloroplast genomes and the phylogenetic relationships of Gossypium species are unclear. Thus, we determined the variations in the repeat sequences and the evolutionary relationships of 40 cotton chloroplast genomes, which represented the most diverse in the genus, including five newly sequenced diploid species, i.e., G. nandewarense (C1-n), G. armourianum (D2-1), G. lobatum (D7), G. trilobum (D8), and G. schwendimanii (D11), and an important semi-wild race of upland cotton, G. hirsutum race latifolium (AD1). The genome structure, gene order, and GC content of cotton species were similar to those of other higher plant plastid genomes. In total, 2860 long sequence repeats (>10 bp in length) were identified, where the F-genome species had the largest number of repeats (G. longicalyx F1: 108) and E-genome species had the lowest (G. stocksii E1: 53). Large-scale repeat sequences possibly enrich the genetic information and maintain genome stability in cotton species. We also identified 10 divergence hotspot regions, i.e., rpl33-rps18, psbZ-trnG (GCC), rps4-trnT (UGU), trnL (UAG)-rpl32, trnE (UUC)-trnT (GGU), atpE, ndhI, rps2, ycf1, and ndhF, which could be useful molecular genetic markers for future population genetics and phylogenetic studies. Site-specific selection analysis showed that some of the coding sites of 10 chloroplast genes (atpB, atpE, rps2, rps3, petB, petD, ccsA, cemA, ycf1, and rbcL) were under protein sequence evolution. Phylogenetic analysis based on the whole plastomes suggested that the Gossypium species grouped into six previously identified genetic clades. Interestingly, all 13 D-genome species clustered into a strong monophyletic clade. Unexpectedly, the cotton species with C, G, and K-genomes were admixed and nested in a large clade, which could have been due to their recent radiation, incomplete lineage sorting, and introgression hybridization among different cotton lineages. In conclusion, the results of this study provide new insights into the evolution of repeat sequences in chloroplast genomes and interspecific relationships in the genus Gossypium. [ABSTRACT FROM AUTHOR]

Two polymorphs of supramolecular isomers, a discrete dimer and a zig-zag chain, having the same chemical composition, [Mn(Hbit)Cl2] (Hbit=1-methyl-2-(1H-1,2,3-triazol-4-yl)-1H-benzo[d]imidazole), were obtained solvothermally in a one-pot synthesis. The isomers differ in a number of ways: orange blocks versus pale-yellow needles, triclinic P1 versus orthorhombic Pbcn, double µ2-Cl versus alternate single and triple µ2-Cl, coordination number 5 versus 6, and antiparallel versus parallel near-neighbor orientation of Hbit. The packing in each case is driven by the supramolecular interactions, H-bonds (N--H…Cl, C--H…Cl) and π…π overlaps, calculated to be in the range 20-36 kcalmol-1. Calculations gave a difference of only 2 kcalmol-1 in favor of the dimer, which confirms with the observation of principally the dimer at short reaction time. ESI-MS spectra of the dissolved crystals reveal the same fragments with similar distributions. The presence of two fragments at m/z 286.96 [MnIV(Hbit)Cl-2H]+ and 323.94 [MnIII (Hbit)Cl2]+ indicates that [Mn(Hbit)Cl2] is the building unit in both cases; thus, the different orientations of the ligands lead to the two polymorphs stabilized by the respective supramolecular interactions. Importantly, the chain form represents the first example with alternate single and triple µ2-Cl bridges. The magnetic interactions are weakly antiferromagnetic in both cases, with J in the range 0.07-0.34 cm-1; however, high-field EPR analysis reveals moderate magneto-anisotropy with D=0.26(1) cm-1, E=0.06(1) cm-1 and D=0.17(1) cm-1, E=0.03(1) cm-1, respectively. [ABSTRACT FROM AUTHOR]

Cotton is one of the most important fiber and oil crops in the world. Chloroplast genomes harbor their own genetic materials and are considered to be highly conserved. Transfer RNAs (tRNAs) act as "bridges" in protein synthesis by carrying amino acids. Currently, the variation and evolutionary characteristics of tRNAs in the cotton chloroplast genome are poorly understood. Here, we analyzed the structural variation and evolution of chloroplast tRNA (cp tRNA) based on eight diploid and two allotetraploid cotton species. We also investigated the nucleotide evolution of chloroplast genomes in cotton species. We found that cp tRNAs in cotton encoded 36 or 37 tRNAs, and 28 or 29 anti-codon types with lengths ranging from 60 to 93 nucleotides. Cotton chloroplast tRNA sequences possessed specific conservation and, in particular, the Ψ-loop contained the conserved U-U-C-X3-U. The cp tRNAs of Gossypium L. contained introns, and cp tRNAIle contained the anti-codon (C-A-U), which was generally the anti-codon of tRNAMet. The transition and transversion analyses showed that cp tRNAs in cotton species were iso-acceptor specific and had undergone unequal rates of evolution. The intergenic region was more variable than coding regions, and non-synonymous mutations have been fixed in cotton cp genomes. On the other hand, phylogeny analyses indicated that cp tRNAs of cotton were derived from several inferred ancestors with greater gene duplications. This study provides new insights into the structural variation and evolution of chloroplast tRNAs in cotton plants. Our findings could contribute to understanding the detailed characteristics and evolutionary variation of the tRNA family. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium spp.) is a vital global source of renewable fiber and ranks among the world's most important cash crops. While extensive nuclear genomic data of Gossypium has been explored, the organellar genomic resources of allotetraploid cotton, remain largely untapped at the population level. The plastid genome (plastome) is well suited for studying plant species relationships and diversity due to its nonrecombinant uniparental inheritance. Here, we conducted de novo assembly of 336 Gossypium plastomes, mainly from domesticated cultivars, and generated a pan‐plastome level resource for population structure and genetic diversity analyses. The assembled plastomes exhibited a typical quadripartite structure and varied in length from 160 103 to 160 597 bp. At the species level, seven allotetraploid species were resolved into three clades, where Gossypium tomentosum and Gossypium mustelinum formed an early diverging clade rooted by diploids, followed by splitting two sister clades of Gossypium darwinii–Gossypium barbadense and Gossypium hirsutum–Gossypium ekmanianum–Gossypium stephensii. Within the G. hirsutum clade the resolution of cultivated accessions was less polyphyletic with landrace and wild accessions than in G. barbadense suggesting some selection on plastome in the domestication of this adaptable species of cotton. The nucleotide diversity of G. hirsutum was higher than that of G. barbadense. We specifically compared the plastomes of G. hirsutum and G. barbadense to find mutational hotspots within each species as potential molecular markers. These findings contribute a valuable resource for exploring cotton evolution as well as in the breeding of new cotton cultivars and the preservation of wild and cultivated germplasm. [ABSTRACT FROM AUTHOR]

Copper(II) (Cu 2+ ) is essential for plant growth and development. However, high concentrations are extremely toxic to plants. We investigated the tolerance mechanism of cotton under Cu 2+ stress in a hybrid cotton variety (Zhongmian 63) and two parent lines with different Cu 2+ concentrations (0, 0.2, 50, and 100 μM). The stem height, root length, and leaf area of cotton seedlings had decreased growth rates in response to increasing Cu 2+ concentrations. Increasing Cu 2+ concentration promoted Cu 2+ accumulation in all three cotton genotypes' roots, stems, and leaves. However, compared with the parent lines, the roots of Zhongmian 63 were richer in Cu 2+ and had the least amount of Cu 2+ transported to the shoots. Moreover, excess Cu 2+ also induced changes in cellular redox homeostasis, causing accumulation of hydrogen peroxide (H 2 O 2 ) and malondialdehyde (MDA). Conversely, antioxidant enzyme activity increased, while photosynthetic pigment content decreased. Our findings indicated that the hybrid cotton variety fared well under Cu 2+ stress. This creates a theoretical foundation for the further analysis of the molecular mechanism of cotton resistance to copper and suggests the potential of the large-scale planting of Zhongmian 63 in copper-contaminated soils.

Gene flow patterns and the genetic structure of domesticated crops like cotton are not well understood. Furthermore, marker-assisted breeding of cotton has lagged far behind that of other major crops because the loci associated with cotton traits such as fiber yield and quality have scarcely been identified. In this study, we used 19 microsatellites to first determine the population genetic structure and patterns of gene flow of superior germplasm resources in upland cotton. We then used association analysis to identify which markers were associated with 15 agronomic traits (including ten yield and five fiber quality traits). The results showed that the upland cotton accessions have low levels of genetic diversity (polymorphism information content = 0.427), although extensive gene flow occurred among different ecological and geographic regions. Bayesian clustering analysis indicated that the cotton resources used in this study did not belong to obvious geographic populations, which may be the consequence of a single source of domestication followed by frequent genetic introgression mediated by human transference. A total of 82 maker-trait associations were examined in association analysis and the related ratios for phenotypic variations ranged from 3.04% to 47.14%. Interestingly, nine SSR markers were detected in more than one environmental condition. In addition, 14 SSR markers were co-associated with two or more different traits. It was noteworthy that NAU4860 and NAU5077 markers detected at least in two environments were simultaneously associated with three fiber quality traits (uniformity index, specific breaking strength and micronaire value). In conclusion, these findings provide new insights into the population structure and genetic exchange pattern of cultivated cotton accessions. The quantitative trait loci of domesticated cotton identified will also be very useful for improvement of yield and fiber quality of cotton in molecular breeding programs., Competing Interests: The authors declare that they have no conflict of interests., (© 2020 Kunming Institute of Botany, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.)

A series of mononuclear lanthanide complexes [Ln( L1 )(NO 3 ) 3 ], (Ln = Dy(III), 1 ; Tb(III), 3 ; and Eu(III), 4 ; L1 = ( N 1 E , N 2 E )- N 1 , N 2 -bis((1-methyl-1 H -benzo[ d ]imidazol-2-yl)methylene)cyclohexane-1,2-diamine) is obtained by reacting N -methylbenzimidazole-2-carbaldehyde ( L2 ) and 1,2-cyclohexanediamine ( L3 ) with Ln(NO 3 ) 3 ·6H 2 O under solvothermal conditions. L1 ligand is produced via an in situ Schiff base reaction of two molecules of L2 and one molecule of L3 . The metal center Ln(III) is in a N 4 O 6 environment formed by L1 and NO 3 - . NaSCN is added on the basis of 1 synthesis. One SCN - replaces one of the three coordinated NO 3 - anions in the 1 structure, and the complex [Dy( L1 )(NO 3 ) 2 (SCN)]·CH 3 CN ( 2 ) is synthesized. The complex 1 shows excellent luminescence response to petroleum ether (PET), an organic solvent. To the best of our knowledge, this study is the first to use a complex for sensing responses to PET. When the metal center is changed, the obtained mononuclear complexes 3 and 4 show an excellent luminescence response to tetrahydrofuran (THF). Lastly, 2 obtained by changing the coordinating anion shows an excellent luminescence response to dichloromethane. Herein, for the first time, we regulate the metal center and coordinating anion of lanthanide complexes to adjust the recognition and response of these complexes to different organic solvents.

The solvent-induced topological and structural diversities of two Co(II) complexes, namely, [Co(L) 2 (SCN) 2 ] ( Co1 ) and [Co 2 (L) 2 (SCN)(OAc) 3 ] ( Co2 ) (L = 8-methoxyquinoline), were comparatively analyzed. Certain proportions of L, Co(OAc) 2 ·4H 2 O, and NaSCN were mixed and dissolved in CH 3 OH at 60 °C to obtain complex Co1 . Complex Co2 , an asymmetric dinuclear compound, was obtained by simply replacing CH 3 OH with CH 3 CN as the solvent. The Co(II) ion in complex Co1 was coordinated by the N 4 O 2 mode provided by two L ligands and two SCN - anions. The two Co(II) ions in Co2 were in the N 2 O 4 and NO 5 coordination environment and were linked by two μ 2 -OAc - bridges and one rare μ 3 -OAc - bridge. Weak interaction analysis revealed that complexes Co1 and Co2 exhibited 6-connected shp and 14-connected fcu nets, respectively. Magnetic studies showed that Co1 demonstrated single-ion magnet behavior under 2000 Oe. These behaviors are indicative of clearly field-induced single-ion magnetic behavior with U eff = 34.7(2) K and τ 0 = 2.7(2) × 10 -7 s under 2000 Oe dc field, respectively. By contrast, Co2 lacked frequency dependence under zero-field conditions. Electrospray ionization mass spectrometry indicated that two complexes were stable in N , N -dimethylformamide., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)

The most effective way to understand reaction mechanisms and kinetics is to identify the reaction intermediates and determine the possible reaction patterns. The influencing factors that must be considered in the self-assembly of clusters are the type of ligand, metal ion, coordination anion and the pH of the solution. However, changes in ligand substituents resulting in different self-assembly processes to obtain different types of structures are still very rare, especially with -H and -CH 3 substituents, which do not exert significant steric hindrance effects. In this study, planar mononuclear Ni(L 1 ) 2 (L 1 = 2-ethoxy-6-(iminomethyl)phenol) was dissolved in methanol and combined with Dy(NO 3 ) 3 ·6H 2 O for 48 h at room temperature to obtain a butterfly-like Ni 2 Dy 2 cluster ([Dy 2 Ni 2 (L 1 ) 4 (CH 3 O) 2 (NO 3 ) 4 ], 1). The Dy(iii) ions in cluster 1 are in an O 8 N coordination environment, and the Ni(ii) ions are in an O 5 N coordination environment. High-resolution electrospray ionization mass spectrometry (HRESI-MS) was used to track species changes during the formation of cluster 1. Six key intermediate fragments were screened, and the self-assembly mechanism was proposed as Ni(L 1 ) 2 → HL 1 + NiL 1 → DyL 1 /Ni(L 1 ) 2 '→ DyNi(L 1 ) 2 → Dy 2 Ni 2 (L 1 ) 4 . Through this assembly mechanism, we found that Ni(L 1 ) 2 was first cleaved into HL 1 + NiL 1 and then further assembled to obtain 1. Another butterfly-like tetranuclear heterometallic cluster ([Dy 2 Ni 2 (L 2 ) 4 (CH 3 O) 2 (NO 3 ) 4 ], 2) was obtained using planar mononuclear Ni(L 2 ) 2 (L 2 = (E)-2-ethoxy-6-((methylimino)methyl)phenol) with -CH 3 substitution on the nitrogen atom under the same reaction conditions. The structural analysis of cluster 2 showed that the Dy(iii) ions are in an O 9 coordination environment, and the Ni(ii) ions are in an O 4 N 2 coordination environment. HRESI-MS was used to trace species changes during the formation of 2, and the assembly mechanism was proposed as Ni(L 2 ) 2 → DyNi(L 2 ) 2 → Dy 2 Ni(L 2 ) 2 → Dy 2 Ni 2 (L 2 ) 4 . Analysis of the assembly mechanism of 2 showed that Ni(L 2 ) 2 was twisted during the reaction, and its coordination point was exposed to capture the Dy(iii) ions. Finally, Dy(NO 3 ) 3 ·6H 2 O was replaced with NaN 3 to obtain a [Ni 2 Na 2 (L 2 ) 4 (N 3 ) 4 ] cluster (3) under the same reaction conditions and verify the above-mentioned torsion step. HRESI-MS was also used to trace the assembly process, and the assembly mechanism was proposed as Ni(L 2 ) 2 → NiNa(L 2 ) 2 → NiNa 2 (L 2 ) 2 → Ni 2 Na 2 (L 2 ) 4 . Herein, the effect of interference from substitution and the regulation self-assembly process were discovered in the formation of 3d-4f heterometallic clusters, and different types of coordination clusters were obtained.

Metal nanoclusters have a certain rigidity due to their specific coordination patterns and shapes; thus, they face extreme difficulty in folding into a specific direction to form a double-helix structure and in further interconnecting to form metal-helix frameworks (MHFs). To date, no MHFs have been produced by the formation of heterometallic clusters. Selecting the appropriate "bonding molecules" to bond metal nanoclusters in a specific multiple direction is one of the most effective strategies for designing synthetic MHFs. In this study, we realized for the first time the control of different orientations of μ 3 -NO 3 - to join heterometallic clusters (Cu 10 Dy 2 ) and subsequently form a left-handed double helix chain, which further joins to form MHFs. In the structure of the MHFs, four different directions of bridging μ 3 -NO 3 - exist, three of which are involved in the linkage of the double-helix chain. Each μ 3 -NO 3 - is connected to three adjacent Cu 10 Dy 2 . Herein, we extend a new method for designing synthetic double-helix structures and MHFs, thereby further laying the foundation for the development of similar DNA double-helix structures and nucleic acid secondary structures in vitro., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The formation of high-nuclearity clusters of lanthanide usually involves many complicated self-assembly processes. Thus, tracking the formation process is extremely difficult and research on the assembly mechanism is very rare. In this study, a Dy-exclusive nanocluster containing vertex-sharing [Dy 4 (μ 3 -OH) 4 ] cubanes, denoted as [Dy 12 (L) 8 (OH) 16 (CH 3 O) 8 (H 2 O) 8 ]·(CH 3 O) 4 (Dy 12 , L = quinoline-2-carboxylate), was designed and synthesized from L and DyCl 3 ·6H 2 O. Eight quinoline-2-carboxylate ligands were encapsulated on the periphery of the Dy 12 cluster, which served to stabilize the core. The high stability of the Dy 12 cluster core was further confirmed by high-resolution electrospray-ionization mass spectrometry (HRESI-MS). With increased ion-source energy, only CH 3 O - and OH - bridging ligands were replaced inside the Dy 12 cluster. Notably, eight intermediate fragments were successfully observed from the Dy 12 cluster formation by time-dependent HRESI-MS. First, ligand L captured Dy 3+ to give Dy 1 , which further formed Dy 2 through μ 2 -O bridging. The Dy 12 cluster was constructed in one step with four Dy 2 and four Dy 3+ as templates: L → Dy 1 → Dy 2 → Dy 12 . Moreover, a series of Dy 3 -Dy 6 fragment peaks with relatively weak intensities were observed, and an alternative stepwise-assembly route was proposed: L → Dy 1 → Dy 2 → Dy 3 → Dy 4 → Dy 5 → Dy 6 → Dy 12 . On comparing the two different assembly methods, the multitemplate guided assembly formed Dy 12 was found to be dominant. To the best of our knowledge, this study was the first to propose the involvement of two self-assembly mechanisms in the construction of lanthanide clusters, as further confirmed by HRESI-MS. Magnetic studies further showed that Dy 12 clusters exhibited field-induced single-molecule magnet behavior.

A clear dependence on the ligand has been observed for the magnetic properties of a closely related series of Co(II) cubane structures, viz. [Co 4 (mbm or bm) 4 (ROH) 4 Br 4 ] (1-MeOH, 1-EtOH, 2-MeOH, and 2-EtOH, where 1 = [Co 4 (mbm) 4 Br 4 ], 2 = [Co 4 (bm) 4 Br 4 ], bm = (1H-benzo[d]imidazol-2-yl)methanolate. and mbm = 1-Me-bm.) The [Co 4 (OR) 4 ] cubane core consists of an octahedral Co II center chelated by the alkoxide oxygen and imidazole nitrogen atoms from monoanionic bm or mbm and coordinated by methanol/alcohol and bromine. Interestingly, electrospray ionization mass spectrometry (ESI-MS) indicates that 1-MeOH and 2-MeOH are unstable in methanol and transformed to the butterfly [Co 4 L 6 ] 2+ but that 1-EtOH and 2-EtOH are stable in ethanol. Their magnetic susceptibilities suggest ferromagnetic coupling between the nearest cobalt centers to give a theoretical S = 4 × 3/2 ground state with considerable magneto-crystalline behavior. The packing and intermolecular interactions appear to influence the geometry of the cubes and thus the anisotropy of cobalt, which leads to different blocking temperatures (T B ). Consequently, the compounds with mbm, 1-MeOH and 1-EtOH, exhibit T B > 2 K as shown by the relaxation of magnetization in zero applied dc field where the barriers U eff /k B are respectively 27 and 21 K and relaxation times are τ 0 = 1.3 × 10 -9 and 9.7 × 10 -9 s. However, the compounds with bm, 2-MeOH and 2-EtOH, remain paramagnetic above 2 K and do not show nonlinear response of the ac susceptibilities. These findings reaffirm the subtle dependence of single-molecule magnetism on coordination geometry and intermolecular interaction.

Notopterygium H. de Boissieu (Apiaceae) is an endangered perennial herb endemic to China. A good knowledge of phylogenetic evolution and population genomics is conducive to the establishment of effective management and conservation strategies of the genus Notopterygium . In this study, the complete chloroplast (cp) genomes of four Notopterygium species ( N. incisum C. C. Ting ex H. T. Chang, N. oviforme R. H. Shan, N. franchetii H. de Boissieu and N. forrestii H. Wolff) were assembled and characterized using next-generation sequencing. We investigated the gene organization, order, size and repeat sequences of the cp genome and constructed the phylogenetic relationships of Notopterygium species based on the chloroplast DNA and nuclear internal transcribed spacer (ITS) sequences. Comparative analysis of plastid genome showed that the cp DNA are the standard double-stranded molecule, ranging from 157,462 bp ( N. oviforme ) to 159,607 bp ( N. forrestii ) in length. The circular DNA each contained a large single-copy (LSC) region, a small single-copy (SSC) region, and a pair of inverted repeats (IRs). The cp DNA of four species contained 85 protein-coding genes, 37 transfer RNA (tRNA) genes and 8 ribosomal RNA (rRNA) genes, respectively. We determined the marked conservation of gene content and sequence evolutionary rate in the cp genome of four Notopterygium species. Three genes ( psaI , psbI and rpoA ) were possibly under positive selection among the four sampled species. Phylogenetic analysis showed that four Notopterygium species formed a monophyletic clade with high bootstrap support. However, the inconsistent interspecific relationships with the genus Notopterygium were identified between the cp DNA and ITS markers. The incomplete lineage sorting, convergence evolution or hybridization, gene infiltration and different sampling strategies among species may have caused the incongruence between the nuclear and cp DNA relationships. The present results suggested that Notopterygium species may have experienced a complex evolutionary history and speciation process.

Aceraceae is a large forest tree family that comprises many economically and ecologically important species. However, because interspecific and/or intraspecific morphological variations result from frequent interspecific hybridization and introgression, it is challenging for non-taxonomists to accurately recognize and identify the tree species in Aceraceae based on a traditional approach. DNA barcoding is a powerful tool that has been proposed to accurately distinguish between species. In this study, we assessed the effectiveness of three core standard markers ( mat K, rbc L and ITS ) plus the chloroplast locus trn S -trn G as Aceraceae barcodes. A total of 231 sequences representing 85 species in this forest family were collected. Of these four barcode markers, the discrimination power was highest for the ITS (I) region (50%) and was progressively reduced in the other three chloroplast barcodes mat K (M), trn S- trn G (T) and rbc L (R); the discrimination efficiency of the ITS marker was also greater than any two-locus combination of chloroplast barcodes. However, the combinations of ITS plus single or combined chloroplast barcodes could improve species resolution significantly; T+I (90.5% resolution) and R+M+T+I (90.5% resolution) differentiated the highest portion of species in Aceraceae. Our current results show that the nuclear ITS fragment represents a more promising DNA barcode marker than the maternally inherited chloroplast barcodes. The most efficient and economical method to identify tree species in Aceraceae among single or combined DNA barcodes is the combination of T+I (90.5% resolution).

Two polymorphs of supramolecular isomers, a discrete dimer and a zig-zag chain, having the same chemical composition, [Mn(Hbit)Cl 2 ] (Hbit=1-methyl-2-(1H-1,2,3-triazol-4-yl)-1H-benzo[d]imidazole), were obtained solvothermally in a one-pot synthesis. The isomers differ in a number of ways: orange blocks versus pale-yellow needles, triclinic P1‾ versus orthorhombic Pbcn, double μ 2 -Cl versus alternate single and triple μ 2 -Cl, coordination number 5 versus 6, and antiparallel versus parallel near-neighbor orientation of Hbit. The packing in each case is driven by the supramolecular interactions, H-bonds (N-H⋅⋅⋅Cl, C-H⋅⋅⋅Cl) and π⋅⋅⋅π overlaps, calculated to be in the range 20-36 kcal mol -1 . Calculations gave a difference of only 2 kcal mol -1 in favor of the dimer, which confirms with the observation of principally the dimer at short reaction time. ESI-MS spectra of the dissolved crystals reveal the same fragments with similar distributions. The presence of two fragments at m/z 286.96 [Mn IV (Hbit)Cl-2H] + and 323.94 [Mn III (Hbit)Cl 2 ] + indicates that [Mn(Hbit)Cl 2 ] is the building unit in both cases; thus, the different orientations of the ligands lead to the two polymorphs stabilized by the respective supramolecular interactions. Importantly, the chain form represents the first example with alternate single and triple μ 2 -Cl bridges. The magnetic interactions are weakly antiferromagnetic in both cases, with J in the range 0.07-0.34 cm -1 ; however, high-field EPR analysis reveals moderate magneto-anisotropy with D=0.26(1) cm -1 , E=0.06(1) cm -1 and D=0.17(1) cm -1 , E=0.03(1) cm -1 , respectively., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)