Electrogenerated Chemiluminescence of a Series of Donor−Acceptor Molecules and X-ray Crystallographic Evidence for the Reaction Mechanisms

Three series of donor−acceptor π-conjugated (D-π-A) molecules 1−3 have been synthesized with a 2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolinyl (Julolidine group), N,N-dimethylamino, or N,N-diphenylamino group as the donor moiety, a phenylvinyl or thienylvinyl unit as the bridge, and a bromide or aldehyde group as the acceptor moiety. The photophysical, electrochemical, and electrogenerated chemiluminescence (ECL) characters of these compounds have been studied in a 1:1 PhH/MeCN solution. Three different categories of ECL mechanisms for each of the three families of compounds are discussed, respectively. Compounds 1a−c produce typical and simple monomer ECL emission resulting from the annihilation of their radical cations and radical anions. The ECL emission of compounds 2a−c can be ascribed as an excimer emission. Compounds 3a−c exhibit an aggregate ECL emission. X-ray crystal structures of compounds 1b, 2a, and 3a provide further proof for the above-mentioned reaction mechanisms. All these compounds show stable ECL emission via the singlet excited state without the addition of any co-reactant or additional compound

The complete mitochondrial genome of <i>Tauraco livingstonii</i> (Musophagidae: Tauraco)

Livingstone’s turaco, Tauraco livingstonii, belongs to the family Musophagidae. In this study, we obtained the complete mitochondrial genome sequence of Livingstone’s turaco by high-throughput sequencing technology and constructed a phylogenetic tree. It was found that the mitochondria of this species are 19,015 bp in length and contain a total of 37 genes, comprising 13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes. The base composition of the mitochondrial genome is 31.61% A, 24.22% T, 30.64% C, and 13.52% G, with a GC content of 44%. Notably, an intriguing phenomenon of mitochondrial genome rearrangements was observed, characterized by the duplication of the tRNA Glu-L-CR gene order. In addition, the results of the phylogenetic tree analysis shed light on the taxonomic position of Livingstone’s turaco and supported the taxonomy of Otidimorphae. The study provides a basis for future phylogenetic and taxonomic investigations of Musophagiformes.</p

Preparation, Facile Deprotonation, and Rapid H/D Exchange of the μ-Hydride Diiron Model Complexes of the [FeFe]-Hydrogenase Containing a Pendant Amine in a Chelating Diphosphine Ligand

The CO-displacement of [(μ-pdt)Fe2(CO)6] with (Ph2PCH2)2N(n-Pr) in refluxing toluene gave an unsymmetrical chelating complex [(μ-pdt){Fe(CO)3}{Fe(CO)(κ2-Ph2PCH2N(n-Pr)CH2PPh2}] (1) as a major product, together with a small amount of the symmetrical intramolecular bridging complex [(μ-pdt){μ-Ph2PCH2N(n-Pr)CH2PPh2}{Fe(CO)2}2] (2) and the intermolecular bridging complex [{μ,κ1,κ1-Ph2PCH2N(n-Pr)CH2PPh2}{(μ-pdt)Fe2(CO)5}2] (3). In contrast, the reaction of [(μ-pdt)Fe2(CO)6] with (Ph2PCH2)2NR (R = n-Pr, Ph) afforded the intermolecular bridging isomers 3 and 4 in the presence of a CO-removing reagent Me3NO·2H2O in CH3CN at room temperature. The molecular structures of 1, 3, and 4, as well as the doubly protonated complex [1(HNHμ)](OTf)2] were determined by X-ray analyses. The protonation processes of 1 with HBF4·Et2O and HOTf were studied in different solvents. The presence of the Hμ···HN interaction in [1(HNHμ)]2+ was studied by relaxation time T1 and spin saturation transfer measurements. The μ-hydride of [1(Hμ)]+ and [1(HNHμ)]2+ undergo facile deprotonation with aniline and rapid H/D exchange with deuterons in solution. In contrast, neither deprotonation nor H/D exchange was detected for [(μ-H)(μ-pdt){Fe(CO)3}{Fe(CO)(κ2-dppp)}]+ ([5(Hμ)]+, dppp = Ph2PCH2CH2CH2PPh2) without internal base

Copper-Catalyzed Direct Oxidative C–H Amination of Benzoxazoles with Formamides or Secondary Amines under Mild Conditions

A facile, efficient, and practical method for copper-catalyzed direct C–H amination of benzoxazoles with formamides or secondary amines has been developed. The system can be performed in the absence of external base and only requires O2 or even air as oxidant. A variety of substituted benzoxazol-2-amines were synthesized with moderate to excellent yield

Bis(oxazolinyl)phenyl-Ligated Rare-Earth-Metal Complexes: Highly Regioselective Catalysts for <i>cis</i>-1,4-Polymerization of Isoprene

NCN-pincer (<i>S,S</i>)-2,6-bis­(4′-isopropyl-2′-oxazolinyl)­phenyl-ligated rare-earth-metal dichlorides [(<i>S,S</i>)-Phebox-^<i>i</i>Pr]­LnCl₂(THF)₂ (Ln = Sc (<b>1</b>); Y (<b>2</b>); Dy (<b>3</b>); Ho (<b>4</b>); Tm (<b>5</b>); Lu (<b>6</b>)) were synthesized via transmetalation between [(<i>S,S</i>)-Phebox-^<i>i</i>Pr]Li and LnCl₃ in THF solvent. Interestingly, treatment of LaCl₃ by the same method generated tris­(ligand) lanthanum complex [(<i>S,S</i>)-Phebox-^<i>i</i>Pr]₃La (<b>7</b>). Molecular structures of complexes <b>1</b>, <b>2</b>, <b>3</b>, and <b>7</b> were established by single-crystal X-ray diffraction study. Pincer ligand (<i>S,S</i>)-Phebox-^<i>i</i>Pr adopts a κC:κN:κN′ tridentate coordination mode to the central metal ion. Upon activation with [PhNHMe₂]­[B­(C₆F₅)₄] and Al^<i>i</i>Bu₃, complexes <b>2</b>–<b>5</b> exhibited highly catalytic activities and more than 98% <i>cis</i>-1,4-selectivity for isoprene polymerization while complexes <b>1</b> and <b>6</b> were inactive for this reaction. When use of the catalyst system consisted of complex <b>2</b>, [PhNHMe₂]­[B­(C₆F₅)₄], and Al^<i>i</i>Bu₃ for isoprene polymerization, the resultant polymer has a high <i>cis</i>-1,4-selectivity up to 99.5%. The reaction temperature had little effect on the regioselectivity, and high <i>cis</i>-1,4-selectivity almost remained even at 80 °C

Bis(oxazolinyl)phenyl-Ligated Rare-Earth-Metal Complexes: Highly Regioselective Catalysts for <i>cis</i>-1,4-Polymerization of Isoprene

NCN-pincer (<i>S,S</i>)-2,6-bis­(4′-isopropyl-2′-oxazolinyl)­phenyl-ligated rare-earth-metal dichlorides [(<i>S,S</i>)-Phebox-^<i>i</i>Pr]­LnCl₂(THF)₂ (Ln = Sc (<b>1</b>); Y (<b>2</b>); Dy (<b>3</b>); Ho (<b>4</b>); Tm (<b>5</b>); Lu (<b>6</b>)) were synthesized via transmetalation between [(<i>S,S</i>)-Phebox-^<i>i</i>Pr]Li and LnCl₃ in THF solvent. Interestingly, treatment of LaCl₃ by the same method generated tris­(ligand) lanthanum complex [(<i>S,S</i>)-Phebox-^<i>i</i>Pr]₃La (<b>7</b>). Molecular structures of complexes <b>1</b>, <b>2</b>, <b>3</b>, and <b>7</b> were established by single-crystal X-ray diffraction study. Pincer ligand (<i>S,S</i>)-Phebox-^<i>i</i>Pr adopts a κC:κN:κN′ tridentate coordination mode to the central metal ion. Upon activation with [PhNHMe₂]­[B­(C₆F₅)₄] and Al^<i>i</i>Bu₃, complexes <b>2</b>–<b>5</b> exhibited highly catalytic activities and more than 98% <i>cis</i>-1,4-selectivity for isoprene polymerization while complexes <b>1</b> and <b>6</b> were inactive for this reaction. When use of the catalyst system consisted of complex <b>2</b>, [PhNHMe₂]­[B­(C₆F₅)₄], and Al^<i>i</i>Bu₃ for isoprene polymerization, the resultant polymer has a high <i>cis</i>-1,4-selectivity up to 99.5%. The reaction temperature had little effect on the regioselectivity, and high <i>cis</i>-1,4-selectivity almost remained even at 80 °C

Palladium-Catalyzed Desulfitative Conjugate Addition of Aryl Sulfinic Acids and Direct ESI-MS for Mechanistic Studies

A new and efficient method for palladium­(II) catalytic desulfitative conjugate addition of arylsulfinic acids with α,β-unsaturated carbonyl compound has been developed. The key reacting intermediates including aryl Pd­(II) sulfinic intermediate, aryl Pd­(II), and COPd complexes were captured by ESI-MS/MS, which provide new experimental evidence for the understanding of addition mechanism

Preparation, Facile Deprotonation, and Rapid H/D Exchange of the μ-Hydride Diiron Model Complexes of the [FeFe]-Hydrogenase Containing a Pendant Amine in a Chelating Diphosphine Ligand

The CO-displacement of [(μ-pdt)Fe2(CO)6] with (Ph2PCH2)2N(n-Pr) in refluxing toluene gave an unsymmetrical chelating complex [(μ-pdt){Fe(CO)3}{Fe(CO)(κ2-Ph2PCH2N(n-Pr)CH2PPh2}] (1) as a major product, together with a small amount of the symmetrical intramolecular bridging complex [(μ-pdt){μ-Ph2PCH2N(n-Pr)CH2PPh2}{Fe(CO)2}2] (2) and the intermolecular bridging complex [{μ,κ1,κ1-Ph2PCH2N(n-Pr)CH2PPh2}{(μ-pdt)Fe2(CO)5}2] (3). In contrast, the reaction of [(μ-pdt)Fe2(CO)6] with (Ph2PCH2)2NR (R = n-Pr, Ph) afforded the intermolecular bridging isomers 3 and 4 in the presence of a CO-removing reagent Me3NO·2H2O in CH3CN at room temperature. The molecular structures of 1, 3, and 4, as well as the doubly protonated complex [1(HNHμ)](OTf)2] were determined by X-ray analyses. The protonation processes of 1 with HBF4·Et2O and HOTf were studied in different solvents. The presence of the Hμ···HN interaction in [1(HNHμ)]2+ was studied by relaxation time T1 and spin saturation transfer measurements. The μ-hydride of [1(Hμ)]+ and [1(HNHμ)]2+ undergo facile deprotonation with aniline and rapid H/D exchange with deuterons in solution. In contrast, neither deprotonation nor H/D exchange was detected for [(μ-H)(μ-pdt){Fe(CO)3}{Fe(CO)(κ2-dppp)}]+ ([5(Hμ)]+, dppp = Ph2PCH2CH2CH2PPh2) without internal base

1,2,3,4-Tetrahydro-8-hydroxyquinoline-Promoted Copper-Catalyzed Coupling of Nitrogen Nucleophiles and Aryl Bromides

Based on the dramatic accelerating effect of 2-aminophenol, three ligands derived from 2-aminophenol were developed. Copper-catalyzed coupling reaction of nitrogen-containing nucleophiles with aryl bromides was efficiently carried out under mild conditions using 1,2,3,4-tetrahydro-8-hydroxyquinoline as a novel, simple, and versatile ligand

Preparation, Facile Deprotonation, and Rapid H/D Exchange of the μ-Hydride Diiron Model Complexes of the [FeFe]-Hydrogenase Containing a Pendant Amine in a Chelating Diphosphine Ligand

The CO-displacement of [(μ-pdt)Fe2(CO)6] with (Ph2PCH2)2N(n-Pr) in refluxing toluene gave an unsymmetrical chelating complex [(μ-pdt){Fe(CO)3}{Fe(CO)(κ2-Ph2PCH2N(n-Pr)CH2PPh2}] (1) as a major product, together with a small amount of the symmetrical intramolecular bridging complex [(μ-pdt){μ-Ph2PCH2N(n-Pr)CH2PPh2}{Fe(CO)2}2] (2) and the intermolecular bridging complex [{μ,κ1,κ1-Ph2PCH2N(n-Pr)CH2PPh2}{(μ-pdt)Fe2(CO)5}2] (3). In contrast, the reaction of [(μ-pdt)Fe2(CO)6] with (Ph2PCH2)2NR (R = n-Pr, Ph) afforded the intermolecular bridging isomers 3 and 4 in the presence of a CO-removing reagent Me3NO·2H2O in CH3CN at room temperature. The molecular structures of 1, 3, and 4, as well as the doubly protonated complex [1(HNHμ)](OTf)2] were determined by X-ray analyses. The protonation processes of 1 with HBF4·Et2O and HOTf were studied in different solvents. The presence of the Hμ···HN interaction in [1(HNHμ)]2+ was studied by relaxation time T1 and spin saturation transfer measurements. The μ-hydride of [1(Hμ)]+ and [1(HNHμ)]2+ undergo facile deprotonation with aniline and rapid H/D exchange with deuterons in solution. In contrast, neither deprotonation nor H/D exchange was detected for [(μ-H)(μ-pdt){Fe(CO)3}{Fe(CO)(κ2-dppp)}]+ ([5(Hμ)]+, dppp = Ph2PCH2CH2CH2PPh2) without internal base