IZCp and PZCp: Redox Non-innocent Cyclopentadienyl Ligands as Electron Reservoirs for Sandwich Complexes

A long-sustained effort of systematic steric and electronic modification of cyclopentadienyl (Cp) ligands has enabled them to find wide-ranging, valuable applications. Herein, we present two novel Cp ligands: imidazolium- and pyrrolinium-substituted zwitterionic Cps (IZCp and PZCp), whose key utility is redox non-innocencethe ability to participate cooperatively with the metal center in redox reactions. Through the simple metalation of ZCps, the Cr(0) and Mo(0) half-sandwich complexes (IZCp)Cr(CO)3, (PZCp)Cr(CO)3, (IZCp)Mo(CO)3, and (PZCp)Mo(CO)3, respectively, as well as the Ru(II) sandwich complexes [(IZCp)RuCp]PF6 and [(PZCp)RuCp]PF6 were prepared. The sandwich complexes were fully characterized and showed by cyclic voltammetry reversible one-electron reduction at E1/2 potentials ranging from −1.7 to −2.7 V vs Fc/Fc+. These values are unusually low and have not been observed with other Cp ligands due to the instability of the reduced complexes. Density functional theory (DFT) calculations for the reduced sandwich derivatives with IZCp and PZCp showed their spin densities to be highly delocalized over their ZCp ligand moieties (70–90%). Electron paramagnetic resonance (EPR) analysis of the isolated K[(PZCp)Mo(CO)3] and (PZCp)RuCp also indicated a high degree of ligand-localized radical character. Thus, the IZCp and PZCp ligands act as electron reservoirs to sustain these sandwich complexes in highly reduced states. At the same time, the CO stretching frequencies of K[(PZCp)Mo(CO)3]: νCO 1871, 1748, and 1699 cm–1, rank the [PZCp]− ligand as the strongest electron-donating Cp ligand among the reported CpMo(CO)3 derivatives, whose νCO > 1746 cm–1. In addition, these redox non-innocent Cps were obtained in high yields and found to be practically air- and moisture-stable, unlike typical Cps

Pyrrolinium-Substituted Persistent Zwitterionic Ferrocenate Derivative Enabling the Application of Ferrocene Anolyte

Here, we report the imidazolium-/pyrrolinium-substituted persistent zwitterionic ferrocenate derivatives, which were characterized by electron paramagnetic resonance (EPR) and 57Fe Mössbauer spectroscopy. Additional theoretical studies on these zwitterionic ferrocenate derivatives clearly explain the origin of their thermal stability and the orbital interactions between iron and imidazolium-/pyrrolinium-substituted zwitterionic cyclopentadienyl ligand. Exploiting the facile Fe­(II/I) redox chemistry, we successfully demonstrated that the pyrrolinium-substituted ferrocene derivative can be applied as an example of derivatized ferrocene anolyte for redox-flow batteries. These zwitterionic ferrocenate derivatives will not only deepen our understanding of the intrinsic chemistry of ferrocenate but have the potential to open the way for the rational design of metallocenate derivatives for various applications

Formation of Highly Stable 1,2-Dicarbonyl Organic Radicals from Cyclic (Alkyl)(amino)carbenes

Two air-stable organic radicals derived from oxalyl chloride and cAAC were synthesized, resulting in the unexpected formation of a known (amino)(carboxy) radical cation ([2]BF4) and the oxidative formation of a 1,2-dicarbonyl radical cation ([3]BF4) from a neutral 3-oxetanone compound (4). The highly strained and newly discovered 4 was obtained by a single-electron reduction of [3]BF4 with a mild reducing agent. This result differs from the generation of NHC-based 1,2-dicarbonyl radicals, indicating the uniqueness of cAAC

Additional file 1: of Purple Brassica oleracea var. capitata F. rubra is due to the loss of BoMYBL2–1 expression

Table S1. Primers used to clone BoMYBL2. (DOCX 19 kb

Additional file 4: of Purple Brassica oleracea var. capitata F. rubra is due to the loss of BoMYBL2–1 expression

Figure S1. Total anthocyanin content (A) of samples of the cabbages (B) shown in Fig. 1. (DOCX 109 kb

Additional file 7: of Purple Brassica oleracea var. capitata F. rubra is due to the loss of BoMYBL2–1 expression

Figure S5. Comparison of different BoMYBL2–1 nucleotide sequences obtained from cabbages. Shaded regions indicate exon sequences. Sequences corresponding to Bol016162 from B. oleracea var. capitata were omitted. (DOCX 31 kb

Additional file 6: of Purple Brassica oleracea var. capitata F. rubra is due to the loss of BoMYBL2–1 expression

Figure S3. Results of genomic DNA-PCR preformed to detect the presence or absence of genes regulating anthocyanin biosynthesis other than BoMYBL2–1. A: B. oleracea var. capitata F. alba or rubra varieties with contrasting characteristics in anthocyanin accumulation were selected for analysis; varieties with green and purple colors are indicated in green or purple. B: PCR analysis of other varieties of B. oleracea. The color of each variety is indicated above each lane. (DOCX 293 kb

Additional file 3: of Purple Brassica oleracea var. capitata F. rubra is due to the loss of BoMYBL2–1 expression

Table S2. List of primer sequences used in RT-PCR and genomic PCR analyses of BoMYBL2. (DOCX 32 kb

Additional file 2: of Purple Brassica oleracea var. capitata F. rubra is due to the loss of BoMYBL2–1 expression

Figure S2. Schematic illustration of the strategy used to clone BoMYBL2–1 from various B. oleracea species. A: Genomic region around the BoMYBL2–1 based on information obtained from two different databases (upper: http://brassicadb.org/brad ; Liu et al. 2014; lower: http://plants.ensembl.org/Brassica_oleracea/Info/Index ; Parkin et al. 2014). B: Illustration showing the positions of the fragments, amplified using different combinations of primer sets, used to assemble the entire promoter and coding sequence of BoMYBL2–1. The yellow block represents a 159 bp repeat sequence. All primer sets are listed in Table 2. BoLPR2 is B. oleracea multicopper oxidase LPR2; BoPUB10 is B. oleracea U-box domain-containing protein 10. (DOCX 72 kb

Additional file 8: of Purple Brassica oleracea var. capitata F. rubra is due to the loss of BoMYBL2–1 expression

Figure S4. Expression of genes associated with anthocyanin biosynthesis in various purple cabbages. Daebakna is a green cabbage used as a reference. (DOCX 387 kb