Search

Efficient photocatalytic solar-to-H2 conversion is pivotal to zero-carbon energy supply.

Herein, we report robust π-conjugated radical cations resulting from the oxidation of hexabenzoperylene (HBP) derivatives, HBP-B and HBP-H, which have butyl and hexyl groups, respectively, attached to the same twisted double helicene π-backbone. The radical cation of HBP-B was successfully crystallized in the form of hexafluorophosphate, which exhibited conductivity as high as 1.32 ± 0.04 S cm

Minidumbbell (MDB) is a noncanonical DNA structure found to form in several pyrimidine-rich short tandem repeats associated with neurodegenerative diseases. The most recently reported MDB contains two pentaloops formed by ATTCT repeats. Here, we studied the effects of a purine residue and a backbone discontinuous site on the structure and thermal stability of MDBs containing two pentaloops. It was found that a purine as the fourth loop residue improved the thermal stability of MDBs containing two regular pentaloops, while a backbone discontinuous site between the third and fourth, or between the fourth and fifth loop residues enhanced the thermal stability of MDBs containing a regular and a quasi pentaloops. The results of this study provide new insights into the sequence criteria and structural basis of MDBs.

Expansions of ATTTT and ATTTC pentanucleotide repeats in the human genome are recently found to be associated with at least seven neurodegenerative diseases, including spinocerebellar ataxia type 37 (SCA37) and familial adult myoclonic epilepsy (FAME) types 1, 2, 3, 4, 6, and 7. The formation of non-B DNA structures during some biological processes is thought as a causative factor for repeat expansions. Yet, the structural basis for these pyrimidine-rich ATTTT and ATTTC repeat expansions remains elusive. In this study, we investigated the solution structures of ATTTT and ATTTC repeats using nuclear magnetic resonance spectroscopy. Here, we reveal that ATTTT and ATTTC repeats can form a highly compact minidumbbell structure at the 5'-end using their first two repeats. The high-resolution structure of two ATTTT repeats was determined, showing a regular TTTTA pentaloop and a quasi TTTT/A pentaloop. Furthermore, the minidumbbell structure could escape from proofreading by the Klenow fragment of DNA polymerase I when it was located at five or more base pairs away from the priming site, leading to a small-scale repeat expansion. Results of this work improve our understanding of ATTTT and ATTTC repeat expansions in SCA37 and FAMEs, and provide high-resolution structural information for rational drug design.

This study explores a bottom-up approach toward negatively curved carbon allotropes from octabenzo[8]circulene, a negatively curved nanographene. Stepwise chemical reduction reactions of octabenzo[8]circulene with alkali metals lead to a unique highly reduced hydrocarbon pentaanion, which is revealed by X-ray crystallography suggesting a local view for the reduction and alkali metal intercalation processes of negatively curved carbon allotropes. Polymerization of the tetrabromo derivative of octabenzo[8]circulene by the nickel-mediated Yamamoto coupling reaction results in a new type of porous carbon-rich material, which consists of a covalent network of negatively curved nanographenes. It has a specific surface area of 732 m2 g-1 and functions as anode material for lithium ion batteries exhibiting a maximum capacity of 830 mAh·g-1 at a current density of 100 mA·g-1. These results indicate that this covalent network presents the key structural and functional features of negatively curved carbon allotropes.

Minidumbbell (MDB) is a newly discovered DNA structure formed by native sequences, which serves as a possible structural intermediate causing repeat expansion mutations in the genome and also a functional structural motif in constructing DNA-based molecular switches. Until now, all the reported MDBs containing two adjacent type II tetraloops were formed by pyrimidine-rich sequences 5'-YYYR YYYR-3' (Y and R represent pyrimidine and purine, respectively), wherein the second and sixth residues folded into the minor groove and interacted with each other. In this study, we have conducted a high-resolution nuclear magnetic resonance (NMR) spectroscopic investigation on alternative MDB-forming sequences and discovered that an MDB could also be formed stably with a purine in the minor groove, which has never been observed in any previously reported DNA type II tetraloops. Our refined NMR solution structures of the two MDBs formed by 5'-CTTG C

Development of new photosensitizers (PSs) with high photodynamic efficacy and minimal side effects is of great interest in photodynamic therapy (PDT). In this work, we reported several pyridine-embedded phenothiazinium (pyridophenothiazinium) dyes, which could be conveniently synthesized in a few short steps and acted as highly efficient and potent PSs to selectively localize to lysosomes and photosensitively kill cancer cells. Among them, compound 5, which possessed the ability of promoting intracellular reactive oxygen species (ROS) upon light irradiation by almost 40-fold higher than that of methylene blue (MB, a general phenothiazinium-based PS), exhibited a remarkable phototherapeutic index (PI = 53.8) against HT29 cancer cells, leading to eradication of large solid tumors (∼300 mm3) in a xenograft mouse model without apparent side effects. These results suggest that the pyridophenothiazinium dyes developed herein, especially compound 5, may serve as promising lysosome-targeted PSs for efficient photodynamic antitumor therapy.

As a strategy to design stable but highly reactive metal nitrido species, we have synthesized a manganese(V) nitrido complex bearing a bulky corrole ligand, [Mn

We set forth to assess the quality of an herbal medicine sold in Hong Kong called Qianliguang by employing a multi-methodological approach. The quality is set by its identity, chemical composition, and bioactivities, among others. Qianliguang (Senecionis scandentis Herba, Senecio scandens Buch.-Ham. ex D.Don) has known antibacterial properties. However, it is poisonous and overconsumption can result in liver damage. Eighteen Qianliguang samples were purchased from herbal shops at various districts in Hong Kong. Samples were first authenticated organoleptically. DNA barcoding at the psbA-trnH, ITS2, and rbcL loci was then conducted to confirm the species. HPLC-UV was performed to screen for the presence of the chemical compounds and to quantify the flavonoid hyperoside. UPLC-MS was used to quantify the amount of the toxic pyrrolizidine alkaloid (PA) adonifoline. Microdilution assay was performed to show the antibacterial effect on Streptococcus aureus and S. pneumoniae. Results showed that five samples were found to be substituted by species belonging to the genus Lespedeza; four samples were mixtures containing not only Qianliguang but also Achyranthes aspera L., Lonicera confusa DC., or Solanum nigrum L. HPLC-UV showed that only ten contained enough hyperoside to meet the standard requirement. In addition, nine samples had adonifoline that exceeded the toxicity standard requirement. In the microdilution assay, samples containing Qianliguang showed inhibition on S. aureus and S. pneumoniae, while among the five Lespedeza sp. samples the antibacterial effects on S. aureus were not detectable; only one sample showed inhibition to S. pneumoniae. Our study illustrated the necessity of using a multi-methodological approach for herbal medicine quality assessment. We also showed that Qianliguang samples in the Hong Kong market were either toxic or adulterated. It is therefore essential to improve the quality control of Qianliguang and probably other herbs in the herbal market.

Manganese complexes in +6 oxidation state are rare. Although a number of Mn(VI) nitrido complexes have been generated in solution via one-electron oxidation of the corresponding Mn(V) nitrido species, they are too unstable to isolate. Herein we report the isolation and the X-ray structure of a Mn(VI) nitrido complex, [MnVI(N)(TAML)]- (2), which was obtained by one-electron oxidation of [MnV(N)(TAML)]2- (1). 2 undergoes N atom transfer to PPh3 and styrenes to give Ph3P═NH and aziridines, respectively. A Hammett study for various p-substituted styrenes gives a V-shaped plot; this is rationalized by the ability of 2 to function as either an electrophile or a nucleophile. 2 also undergoes hydride transfer reactions with NADH analogues, such as 10-methyl-9,10-dihydroacridine (AcrH2) and 1-benzyl-1,4-dihydronicotinamide (BNAH). A kinetic isotope effect of 7.3 was obtained when kinetic studies were carried out with AcrH2 and AcrD2. The reaction of 2 with NADH analogues results in the formation of [MnV(N)(TAML-H+)]- (3), which was characterized by ESI/MS, IR spectroscopy, and X-ray crystallography. These results indicate that this reaction occurs via an initial "separated CPET" (separated concerted proton-electron transfer) mechanism; that is, there is a concerted transfer of 1 e- + 1 H+ from AcrH2 (or BNAH) to 2, in which the electron is transferred to the MnVI center, while the proton is transferred to a carbonyl oxygen of TAML rather than to the nitrido ligand.

Here we report that incorporation of an abasic site to DNA minidumbbells formed by natural sequences can lead to significant enhancements in their thermodynamic stability. Based on these stable minidumbbells, the first metal ion-controlled molecular switch which can regulate instant and reversible DNA duplex formation and dissociation has been constructed.

The synthesis and X-ray structure of a new manganese(V) mesitylimido complex with a tetraamido macrocyclic ligand (TAML), [MnV (TAML)(N-Mes)]- (1), are reported. Compound 1 is oxidized by [(p-BrC6 H4 )3 N]+. [SbCl6 ]- and the resulting MnVI species readily undergoes H-atom transfer and nitrene transfer reactions.

DNA methylation is a prevalent regulatory modification in prokaryotes and eukaryotes. N1-methyladenine (m1A) and N6-methyladenine (m6A) have been found to be capable of altering DNA structures via disturbing Watson–Crick base pairing. However, little has been known about their influences on non-B DNA structures, which are associated with genetic instabilities. In this work, we investigated the effects of m1A and m6A on both the structure and thermodynamic stability of a newly reported DNA minidumbbell formed by two TTTA tetranucleotide repeats. As revealed by the results of nuclear magnetic resonance spectroscopic studies, both m1A and m6A favored the formation of a T·m1A and T·m6A Hoogsteen base pair, respectively. More intriguingly, the m1A and m6A modifications brought about stabilization and destabilization effects on the DNA minidumbbell, respectively. This work provides new biophysical insights into the effects of adenine methylation on the structure and thermodynamic stability of DNA.

Minidumbbell (MDB) is a recently identified non-B DNA structure that has been proposed to associate with genetic instabilities. It also serves as a functional structural motif in DNA nanotechnology. DNA molecular switches constructed using MDBs show instant and complete structural conversions with easy manipulations. The availability of stable MDBs can broaden their applications. In this work, we found that substitutions of cytosine with 5-methylcytosine could lead to a significant enhancement in the thermal stabilities of MDBs. Consecutive methylations of cytosine in MDBs brought about cumulative stabilization with a drastic increase in the melting temperature by 23 °C. NMR solution structures of two MDBs containing 5-methylcytosine residues have been successfully determined and revealed that the enhanced stabilities resulted primarily from favorable hydrophobic contacts, more stable base pairs and enhanced base-base stackings involving the methyl group of 5-methylcytosine.

Here we report that incorporation of an abasic site to DNA minidumbbells formed by natural sequences can lead to significant enhancements in their thermodynamic stability. Based on these stable minidumbbells, the first metal ion-controlled molecular switch which can regulate instant and reversible DNA duplex formation and dissociation has been constructed.

A new strategy was developed for the efficient synthesis of di-, tetra-, and hexa-substituted 1,3-butadienes. This one-pot procedure involves lithium–iodine exchange to generate the corresponding vinyllithium intermediates. A subsequent iron-catalyzed ligand-free oxidative homo-coupling eventually led to the formation of 1,3-butadienes in acceptable to excellent isolated yields.

While valence-pure copper alkynyl nanoclusters show near-infrared TADF, the mixed-valence ones exhibit semiconductivity., We report herein that copper alkynyl nanoclusters show metal-core dependent properties via a charge-transfer mechanism, which enables new understanding of their structure–property relationship. Initially, nanoclusters 1 and 2 bearing respective Cu(i)15 (C1) and Cu(i)28 (C2) cores were prepared and revealed to display near-infrared (NIR) photoluminescence mainly from the mixed alkynyl → Cu(i) ligand-to-metal charge transfer (LMCT) and cluster-centered transition, and they further exhibit thermally activated delayed fluorescence (TADF). Subsequently, a vanadate-induced oxidative approach to in situ generate a nucleating Cu(ii) cation led to assembly of 3 and 4 featuring respective [Cu(ii)O6]@Cu(i)47 (C3) and {[Cu(ii)O4]·[VO4]2}@Cu(i)46 (C4) cores. While interstitial occupancy of Cu(ii) triggers inter-valence charge-transfer (IVCT) from Cu(i) to Cu(ii) to quench the photoluminescence of 3 and 4, such a process facilitates charge mobility to render them semiconductive. Overall, metal-core modification results in an interplay between charge-transfer processes to switch TADF to semiconductivity, which underpins an unusual structure–property correlation for designed synthesis of metal nanoclusters with unique properties and functions.

Dinuclear iron nitrido phthalocyanine complexes are of interest owing to their applications in catalytic oxidation of hydrocarbons. While nitrido-bridged diiron phthalocyanine complexes are well documented, the oxidation chemistry of heterodinuclear iron(IV) phthalocyanine nitrides has not been well explored. In this paper we report on the synthesis of a heterometallic FeIV/RuIV phthalocyanine nitride and its oxidation to yield phthalocyanine cation radical and hydroxyphthalocyanine complexes. Treatment of [FeII(Pc)] (Pc2– = phthalocyanine dianion) with [RuVI(LOEt)(N)Cl2] (LOEt– = [Co(η5-C5H5){P(O)(OEt)2}3]−) (1) afforded the heterometallic μ-nitrido complex [Cl2(LOEt)RuIV(μ-N)FeIV(Pc)(H2O)] (2) that contains an RuIV=N = FeIV linkage with the Ru–N and Fe–N distances of 1.689(6) and 1.677(6) A, respectively, and Ru–N–Fe angle of 176.0(4)°. Substitution of 2 with 4-tert-butylpyridine (Bupy) gave [Cl2(LOEt)RuIV(μ-N)FeIV(Pc)(Bupy)]. The cyclic voltammogram of 2 displayed a reversible Pc-centered oxidation cou...

The development of highly active and selective metal catalysts for efficient oxidation of hydrocarbons and identification of the reactive intermediates in the oxidation catalysis are long-standing challenges. In the rapid hydrocarbon oxidation catalyzed by ruthenium(IV) and -(III) porphyrins, the putative Ru(V)-oxo intermediates remain elusive. Herein we report that arylruthenium(III) porphyrins are highly active catalysts for hydrocarbon oxidation. Using catalyst [RuIII(TDCPP)(Ph)(OEt2)] (H2TDCPP = 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin), the oxidation of C–H bonds of various hydrocarbons with oxidant m-CPBA at room temperature gave alcohols/ketones in up to 99% yield within 1 h; use of [nBu4N]IO4 as a mild alternative oxidant avoided formation of lactone from cyclic ketone in C–H oxidation, and the catalytic epoxidation with up to 99% yield and high selectivity (no aldehydes as side product) was accomplished within 5 min. UV–vis, electrospray ionization–mass spectrometry, resonance Raman, elec...

A series of cis-dioxorhenium(V) complexes containing chiral tetradentate N4 ligands, including cis-[ReV(O)2(pyxn)]+ (1; pyxn = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)cyclohexane-1,2-diamine), cis-[ReV(O)2(6-Me2pyxn)]+ (cis-2), cis-[ReV(O)2(R,R-pdp)]+ (3; R,R-pdp = 1,1′-bis((R,R)-2-pyridinylmethyl)-2,2′-bipyrrolidine), cis-[ReV(O)2(R,R-6-Me2pdp)]+ (4), and cis-[ReV(O)2(bqcn)]+ (5; bqcn = N,N′-dimethyl-N,N′-di(quinolin-8-yl)cyclohexane-1,2-diamine), were synthesized. Their structures were established by X-ray crystallography, showing Re–O distances in the range of 1.740(3)–1.769(8) A and O–Re–O angles of 121.4(2)–124.8(4)°. Their cyclic voltammograms in MeCN (0.1 M [NBu4]PF6) display a reversible ReVI/V couple at E1/2 = 0.39–0.49 V vs SCE. In aqueous media, three proton-coupled electron transfer reactions corresponding to ReVI/V, ReV/III, and ReIII/II couples were observed at pH 1. The Pourbaix diagrams of 1·OTf, 3·OTf, and 5·OTf have been examined. The electronic absorption spectra of the cis-dioxorhenium(...

The synthesis and structural characterization of RhI, IrI and AuI metal complexes derived from 2-quinolyl-linked (thiophosphoranyl)methane CH2(iPr2P=S)(C9H6N-2) (A) are reported. Metathesis reactions of 2-quinolyl-thiophosphinoyl potassium complex [K{CH(iPr2P-S)(C9H6N-2)}]n (1) with 1 equiv. of [MCl(COD)]2 (M = Rh, Ir; COD = cycloocta-1,5-diene) afforded monomeric 2-quinolyl-thiophosphinoyl-rhodium(I) and iridium(I) complex [M(COD){CH(iPr2P=S)(C9H6N-2)}] {M = Rh (2), Ir (3)}, respectively. Upon treatment of 1 with 2 equiv. of [MCl(COD)]2 (M = Ir, Rh), bimetallic complexes [M(COD){CH(iPr2P=S)(C9H6N-2)(M(COD)Cl)}] {M = Rh (4), Ir (5)} were obtained. The reaction of 1 with [AuCl(PPh3)] afforded a geminal dinuclear gold(I) methandiide complex [{Au(PPh3)}2{C(iPr2P-S)(C9H6N-2)}] (6), featuring an aurophilic interaction. Meanwhile, the metathesis reaction of 1 with 1 equiv. of gold(I) complex [AuCl(IPrNHC)] {IPrNHC = C[N(2,6-iPr2C6H3)CH]2} afforded a monomeric two-coordinate monoaurated product, 2-quinolyl-thiophosphinoyl-gold(I) N-heterocyclic carbene complex [Au(IPrNHC){CH(iPr2P-S)(C9H6N-2)}] (7). The structures of 3–7 have been determined by X-ray crystallography and the UV/Vis absorption properties of 2–6 have also been studied.

A new strategy was developed for the efficient synthesis of di-, tetra-, and hexa-substituted 1,3-butadienes. This one-pot procedure involves lithium-iodine exchange to generate the corresponding vinyllithium intermediates. A subsequent iron-catalyzed ligand-free oxidative homo-coupling eventually led to the formation of 1,3-butadienes in acceptable to excellent isolated yields.

This chapter presents 19 problems covering the subject of bioinorganic chemistry, along with their corresponding solutions.

This chapter presents 20 problems covering the subject of bonding and reactivity of metal clusters, along with their corresponding solutions.

This chapter presents 23 problems covering the subject of atomic orbitals, along with the corresponding solutions.

This chapter presents 32 problems covering the subject of transition metal chemistry, along with their corresponding solutions.

This chapter presents 47 problems covering the subject of crystal structure, along with their corresponding solutions.

This chapter presents 22 problems covering the subject of vibrational spectroscopy, along with the corresponding solutions.

This chapter presents 52 problems covering the subject of molecular geometry and bonding, along with the corresponding solutions.

This chapter presents 41 problems covering the subject of crystal field theory, along with the corresponding solutions.

This chapter presents 23 problems covering the subject of molecular symmetry, along with the corresponding solutions.

The First Edition of this book, which appeared in 2013, serves as a problem text for Part I (Fundamentals of Chemical Bonding) and Part II (Symmetry in Chemistry) of the book Advanced Structural Inorganic Chemistry published by Oxford University Press in 2008. A Chinese edition was published by Peking University Press in August in the same year. Since then the authors have received much feedback from users and reviewers, which prompted them to prepare a Second Edition for students ranging from freshmen to senior undergraduates who aspire to attend graduate school after finishing their first degree in Chemistry. Four new chapters are added to this expanded Second Edition, which now contains over 400 problems and their solutions. The topics covered in 13 chapters follow the sequence: electronic states and configurations of atoms and molecules, introductory quantum chemistry, atomic orbitals, hybrid orbitals, molecular symmetry, molecular geometry and bonding, crystal field theory, molecular orbital theory, vibrational spectroscopy, crystal structure, transition metal chemistry, metal clusters: bonding and reactivity, and bioinorganic chemistry. The problems collected in this volume originate from examination papers and take-home assignments that have been part of the teaching program conducted by senior authors at The Chinese University of Hong Kong over nearly a half-century. Whenever appropriate, source references in the chemical literature are given for readers who wish to delve deeper into the subject. Eight Appendices and a Bibliography listing 157 reference books are provided to students and teachers who wish to look up comprehensive presentations of specific topics.

This chapter presents 33 problems covering the subject of introductory quantum chemistry, along with the corresponding solutions.

This chapter presents 29 problems covering the subject of electronic states and configurations of atoms and molecules, along with the corresponding solutions.

A new strategy to construct electron-precise B-B single bond via direct borylene insertion into B-H bond is described. Reduction of bromoborylene stabilized by carborane-fused silylenes with 2 equiv of sodium gives a new compound with a B-B single bond. Both experimental and density functional theory results suggest that such an electron-precise B-B single bond is formed via in situ generated borylene insertion into B-H bond.

Here we report a facile one-step low-temperature solution-based method to treat native TiO2 with NaH. The NaH treatment effectively induces the Ti(iii) species and oxygen vacancies into the TiO2 host lattice, and enables the absorption edge of TiO2 to be conveniently adjusted from the UV region to the red end of the visible spectrum.

Zinc oxysulfide (ZnO0.6S0.4) nanoparticles, prepared via a coprecipitation–calcination method, were used as an effective visible-light-driven (VLD) photocatalyst for the inactivation of a typical Gram-negative bacterium, Escherichia coli K-12 for the first time. An energy-saving white light emitting diode (LED) lamp was employed as the visible light (VL) source. Compared to the only UV-responsive pure ZnO and ZnS, the light active region of ZnO0.6S0.4 was expanded as far as 550 nm in the VL region. Significantly, the obtained ZnO0.6S0.4 nanoparticles showed considerable VLD photocatalytic bacterial inactivation activity under white LED irradiation. The mechanism of inactivation was investigated in-depth. Photogenerated holes (h+) and hydrogen peroxide (H2O2) were predominantly responsible for the bacterial inactivation. Moreover, H2O2 was evidenced to be derived only from electrons in the conduction band of ZnO0.6S0.4 in the present photocatalytic system. The integrated damage from the direct oxidation effect of the h+ and continuous accumulation of H2O2 resulted in a high bacterial inactivation efficiency of ZnO0.6S0.4 nanoparticles under visible white LED lamp irradiation. The destruction process of bacterial cells by the ZnO0.6S0.4 photocatalyst was also monitored. This was shown to begin with an attack of the cell membrane and then end in the release of intracellular components.

A number of different nanomaterials produced and incorporated into various products are rising. However, their environmental hazards are frequently unknown. Here we consider three different metal oxide compounds (SnO2, In2O3, and Al2O3), which have not been extensively studied and are expected to have low toxicity. This study aimed to comprehensively characterize the physicochemical properties of these nanomaterials and investigate their toxicity on bacteria (Escherichia coli) under UV illumination and in the dark, as well as on a marine diatom (Skeletonema costatum) under ambient illumination/dark (16-8h) cycles. The material properties responsible for their low toxicity have been identified based on comprehensive experimental characterizations and comparison to a metal oxide exhibiting significant toxicity under illumination (anatase TiO2). The metal oxide materials investigated exhibited significant difference in surface properties and interaction with the living organisms. In order for a material to exhibit significant toxicity, it needs to be able to both form a stable suspension in the culture medium and to interact with the cell walls of the test organism. Our results indicated that the observed low toxicities of the three nanomaterials could be attributed to the limited interaction between the nanoparticles and cell walls of the test organisms. This could occur either due to the lack of significant attachment between nanoparticles and cell walls, or due to their tendency to aggregate in solution.

Conflicting reports on the toxicity of CeO2 nanomaterials have been published in recent years, with some studies finding CeO2 nanoparticles to be toxic, while others found it to have protective effects against oxidative stress. To investigate the possible reasons for this, we have performed a comprehensive study on the physical and chemical properties of nanosized CeO2 from three different suppliers as well as CeO2 synthesized by us, and tested their toxicity. For toxicity tests, we have studied the effects of CeO2 nanoparticles on a Gram-negative bacterium Escherichia coli in the dark, under ambient and UV illuminations. We have also performed toxicity tests on the marine diatom Skeletonema costatum under ambient and UV illuminations. We found that the CeO2 nanoparticle samples exhibited significantly different toxicity, which could likely be attributed to the differences in interactions with cells, and possibly to differences in nanoparticle compositions. Our results also suggest that toxicity tests on bacteria may not be suitable for predicting the ecotoxicity of nanomaterials. The relationship between the toxicity and physicochemical properties of the nanoparticles is explicitly discussed in the light of the current results.