Australian Journal of Chemistry

The Seventh Asia-Pacific Conference of Theoretical and Computational Chemistry (APCTCC7) was held in Kaohsiung, Taiwan, from 25 to 28 January 2016. The papers in this Research Front showcase the latest research in theoretical and computational chemistry, including cutting edge applications in drug discovery, materials science, sustainable resources, and nanotechnology.

Theoretical calculations are used to explore a plausible mechanism for oxidative cleavage of cholesterol mediated by two ground-state O₂ molecules and methionine.

This work uses high-level thermochemical procedures to investigate the reaction mechanism for the conversion of important pyrolysis intermediates into levoglucosenone. This process is of importance in biomass conversion. We consider both the uncatalyzed and water-catalyzed reaction mechanisms. We find that a water catalyst leads to a significant reduction in the reaction barrier height for the entire process and to a change in the reaction mechanism.

The asymptotic functional form preservation method is developed in the framework of supersymmetric quantum mechanics to obtain the energies and wave functions of anharmonic oscillators. Several ansatz functional forms are proposed for the superpotential to obtain the ground and excited state energies with high accuracy.

The electronic and optical properties of the narrowest armchair graphene nanoribbons (NAGNRs) are studied by various density functional methods. While NAGNRs are found to have stable singlet ground states, the lowest triplet states and the ground states of the cations and anions of NAGNRs exhibit some multi-reference character.

It is demonstrated that the reason for the peripheral bonding mode of the coinage metal atoms with [2.2.2]paracyclophane and deltaphane is not an increase of steric repulsion on the inside of the molecular cavity, but rather the decrease of the electrostatic and orbital contributions to the bonding and that the interaction between the cyclophanes and coinage metal cations is non-covalent.

Salient chemical applications of the recently proposed Atoms in Molecules (AIM) concept based on molecular electrostatic potential (MESP) have been explored. The present work clearly demonstrates the connection of MESP-based AIM with reactivity as well as shielding and deshielding of atoms in NMR studies.

The catalytic mechanism and origin of stereoselectivity of pentanidium-catalyzed asymmetric phase-transfer conjugate addition were studied by DFT calculations. A docking approach was used to sample the conformational space of the diastereomeric C–C bond-forming transition states. The calculated enantioselectivity is in excellent accord with experiment result.

We present a simple yet systematic way to investigate the degree of electron delocalization and structural heterogeneity of cyclic conjugated molecules based on molecular dynamics simulations. π-Electron delocalization is strongly correlated with the planarity of the system. Torsional angle and out-of-plane distance distributions were calculated for the degree of electron delocalization.

Human DNA topoisomerase I (Htopo I) is a validated target for anti-cancer agents; however, available anti-cancer agents are linked with several limitations. Therefore, discovering novel inhibitors for Htopo I is essential. Recent studies have demonstrated that coumarins exhibit anti-cancer activity against several targets. Thus, the current study focussed on predicting coumarin-derived inhibitors as lead compounds for further drug design.

An introduction to electrochemistry at interfaces between immiscible electrolyte solutions and recent advances in the electroanalytical chemistry based on ion-transfer reactions at these interfaces are presented.

Five thiosemicarbazone ligands have been synthesized and their coordination chemistry with gallium investigated. All compounds have been fully characterized by NMR and X-ray crystal structures of two of the complexes are reported. Additionally, the positron emitting isotope ¹⁸F was introduced in the structure of the diphenyl gallium thiosemicarbazone complex using a halogen exchange method.

A multicomponent reaction capable of affording a wide range of novel 7,11-dihydro-6H-chromeno[3,4-e]isoxazolo[5,4-b]pyridin-6-one derivatives via one-pot three-component condensation of 4-hydroxycoumarin, aromatic aldehydes, and 5-amino-3-methylisoxazole in ionic liquid [C₄mim][HSO₄] is reported.

New hexaazamacrobicyclic cage bi-functional chelators (BFCs), 1-N-(3-aminobenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane-1,8-diamine (m-SarAr) and 1-N-(2-aminobenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane-1,8-diamine (o-SarAr), were synthesised and their metal complexation and conjugation to proteins were compared with p-SarAr.

A series of novel 3D Ln–organic frameworks ([Ln(tia)(C₂O₄)_0.5(H₂O)]) with excellent magnetic and luminescent properties have been designed and synthesised.

A N,N-dibenzylacetoamide derivative of p-tert-octylcalix[4]arene has been synthesised and its solvent extraction of precious metals in nitric acid media was investigated for determining the effects of extractant concentration and its contact time as well as nitric acid concentration in comparison with a N,N-diethylacetoamide derivative.

Double-headed nucleotides are designed for using the recognition potential of the additional nucleobases in various nucleic acid constructs. Presented here is a review of the double-headed nucleotide monomers investigated so far and their effects in nucleic acid duplexes and other secondary structures.

This work involves the experimental and theoretical study of the nucleophilic substitution of meta- and para-substituted benzyl bromides with benzylamine.

Three series of THQ-based derivatives were synthesised and evaluated for their anticancer activity against a panel of cancer cell lines. Initial screening revealed that compounds 5d and 6 exerted better activity against MCF-7 than TQ, with IC₅₀ values of 9.6 and 10.0 μM, respectively. These compounds were able to elicit apoptotic cell death through activation of caspase 3/7.

Two new complexes based on 5-nitroisophthalic acid (NIPH) and bis(imidazol) ligands (bimb, mbix), namely, [Co(NIPH)(bimb)(H₂O)]_n (1) [Ni(NIPH)(mbix)]_n (2), have been successfully synthesised under hydrothermal conditions.

Amphiphilic peptides with or without oligoethylene glycol (OEG) chains based on 3,4-bis(benzyloxy)benzoic-linked glutamide were designed and their self-assembly was investigated. The studies showed that the amphiphilic peptide 3 with OEG chains could not only form stable gels in a wide range of solvents, but also allowed control of the width of nanofibres in the gel formed with changing water content.

Three zinc phosphites have been synthesized and characterized. Their frameworks are constructed from 4-connected ZnO₄ tetrahedra and 3-connected HPO₃ pseudopyramids. There are 12-membered ring (12-MR) and 8-MR apertures in their (3,4)-connected network. Helical chains are observed in compound 3.

A polyglycidyl methacrylate electrospun scaffold was fabricated encapsulating a lipophilic drug, PXS64. Efficacy of the developed scaffold was explored for skin scar therapy applications.

The elasticity of a range of vertebrate and particularly human tissues depends on the dynamic and persistent protein, elastin, which is predominantly made by assembling tropoelastin. This overview considers tropoelastin’s molecular features and biological interactions in the context of its value in tissue repair.

In this paper, we summarize recently reported breakthroughs in the arena of nanocatalysts for the oxidative coupling of thiols to their corresponding disulfides with the goal of stimulating further progress in this field.

Many studies have identified the microRNA, miR-494, as a regulator of many cellular processes, and we have demonstrated the role of miR-494 in regulating thrombosis via direct targeting of the anticoagulant factor, Protein S. Changes in miR-494 levels have been reported to be detectable in various biological fluids, thus making miR-494 a good diagnostic marker and therapeutic target.

Ionic liquids are composed of ions only. However, they are not always completely soluble in water. Mixtures of phosphonium/phosphonate-type ionic liquids and water prepared herein exhibited stimuli-responsive phase transition, lower critical solution temperature phase transition, and thermoreversible viscosity change, and underwent rheopectic gelation depending on the water content

Herein, we present the use of tert-butyldimethylsilyl amine (TBDMS-NH₂) as a silylating reagent for phenols, benzyl alcohols, and carboxylic acids under solvent-free conditions. Interestingly, this process is rapid and does not involve the formation of HCl unlike other protection processes.

Polyanhydrides are a fascinating class of degradable polymers that have application in drug delivery, stimuli-responsive materials, and novel nanotechnologies because of their degradability and capacity to undergo surface erosion. This review examines approaches for polyanhydride synthesis, thermomechanical properties, biocompatibility, and hydrolysis and degradation processes.

Doxorubicin (Dox) is a substrate of drug resistance marker P-glycoprotein (P-gp) and, therefore, on entry is effluxed out of cells via P-gp activity. The E-cadherin aptamer–doxorubicin conjugate (Ecad01-Dox) can enter the cell directly as well as by receptor (E-cadherin)-mediated internalization, leading to increased intracellular uptake of Dox.

An efficient, mild, and environmental friendly method has been developed for the synthesis of dihydropyrano[2,3-c]pyrazole over TBD-MSN catalyst by assembling ethyl acetoacetate, hydrazine hydrate, different aldehydes, and malononitrile affording the product in excellent yields. The catalyst was reused several times with retention of activity.

A series of novel carbazoles were synthesized based on structural modifications to lead carbazole 1; several analogues were subsequently demonstrated to exhibit anthelmintic activity both in vitro (H. contortus) and in vivo (H. polygyrus).

Palladium(ii) complexes with N-benzyliminodiacetic acid derivatives, RN(CH₂COOH)₂ (RidaH₂; R = benzyl, para-chlorobenzyl, para-nitrobenzyl, or para-methoxybenzyl), were prepared and characterized by infrared spectroscopy and thermal analysis. Two types of complexes, dihydrates [Pd(RidaH)₂]·2H₂O and anhydrous complexes [Pd(RidaH)₂], were successfully distinguished on the basis of their infrared spectra with the aid of density function theory calculations at the BP86/6–311+G(d,p) level of theory with SDD pseudopotentials.

The synthesis of metal (Cr, Mo, Rh, Au) complexes bearing 4-phosphonamide and 4,5-bis(phosphonamide)-imidazol-2-ylidene ligands (NHC^P) is reported. Phosphonamidyl NHC ligands are generated by deprotonation of imidazolium salts or imidazolium-based ionic liquids.

This paper investigates the use of (10,10) armchair carbon nanotube (CNT(10,10)) as a new drug delivery system for 1,4-dihydropyridine derivatives.

The kinetics of hydrolysis of the most commonly used attractant, cuelure (CL), for Queensland fruit fly, Bactrocera tryoni (Froggatt), and two closely related compounds, melolure (ML) and a newly developed lure, 4-(4-(2,2,2-trifluoroacetoxy)phenyl)-2-butanone (RKTA), were quantitatively investigated by GC-FID.

Under the initiation of ammonium persulfate, acrylic acid was successfully grafted onto the polyvinyl alcohol and sodium lignosulfonate in the reaction system with the assistance of ultrasound, and then an environmental friendly and biodegradable superabsorbent with semi-interpenetrating networks structure was formed due to the binding effect of N,N′-dimethyl acrylamide.

We describe an efficient method for the direct preparation of nitriles from aldehydes and hydroxylamine hydrochloride catalyzed by sulfonated nanohydroxyapatite functionalized by 2-aminoethyl dihydrogen phosphate (HAP@AEPH₂-SO₃H) as an eco-friendly and recyclable solid acid nanocatalyst.

Novel restricted access media–molecularly imprinted magnetic microspheres that displayed water-compatibility, exclusion of biomacromolecules, and selective enrichment of analytes were prepared by a one-pot surface imprinting method for the magnetic dispersion microextraction of trace fluoroquinolones from egg samples.

The incorporation of a simple fluorinated polymer additive in small amounts facilitated the formation of regular honeycomb (HC) films from polymers. Typically highly ordered HC films are difficult to form from such polymers. From analysis of the properties of these mixtures, a new hypothesis was developed, which will provide a new tool to guide and allow the use of a broader range of polymers to prepare HC films.

Irregular hollow polyacrylamide (PAAm) particles were prepared in ethanol/water mixtures by template polymerization of acrylamide using polyvinyl butyral (PVB) as the template material and 2,2′-azobisisobutyronitrile (AIBN) as the initiator. It was found that the shrinkage and dehydration on hollow PAAm particles results in the formation of micro-sized irregular hollow PAAm particles.

Multigram quantities of asperuloside, a glycoside natural product, have been isolated from Coprosma quadrifida in a time-efficient and practical manner via rapid pressurised hot water extraction employing an unmodified household espresso machine. By this approach one of the highest yields of asperuloside from a plant species was obtained.

A new Fourier transform infrared gas-phase method for measuring the vapour pressure of each component of a poorly volatile mixture, and determining the vapour phase composition for each system, is described. The method has been validated using two standards, and a Raoult’s plot surface of a ternary system is reported as proof-of-principle.

An alkyl chain length dependent structure transition was found in [C_nmim][AOT] aqueous solutions, which was induced by the penetration of longer alkyl chains into the aggregate.

Wine is a fascinating natural product containing many hundreds of volatile compounds. A much smaller number of key compounds typically contribute to wine aroma, and odorants with characteristic aroma qualities may even define a particular varietal wine. Examples include the varietal thiols, present as odourless precursors in grape berries, that typify the aroma of Sauvignon Blanc wine.

The 6–7 ring system of the frondosins has been synthesized using a highly stereo- and regioselective ring expansion cascade reaction that was inspired by a biosynthetic proposal.

The nonlinear optical (NLO) coefficients of (triphenylphosphine)gold alkynyl complexes are better than those of (N-heterocyclic carbene)gold alkynyl complexes; calculations suggest that the key low-energy transitions are from the (phosphine)gold to the alkynyl ligand in the former, and from the Au-alkynyl group to NHC in the latter.

Poly(γ-4-methylbenzyl-L-glutamate) pyridinium tetrafluoroborate conjugates with constant main chain length, various pyridinium pendants, and high grafting efficiency can be readily prepared by nucleophilic substitution and ion-exchange reaction. They can exhibit reversible UCST-type phase behaviours in both methanol and water depending on the type of pyridinium pendants.

Oxidative N-dealkylation of tertiary amines with tetraethyl ammonium periodate led to formation of corresponding N-dealkylated and mono-oxygenated products. One electron transfer dominates over hydrogen abstraction in the reaction mechanism.

Al₂O₃ microspheres were prepared by cathode plasma electrolysis without additional heating treatment. The microspheres, with diameters of 5–30 μm, consisted of γ-Al₂O₃ and α-Al₂O₃. The mechanism and model were put forward in the formation process.

Hydrogels have been gaining increasing popularity as biomimetic materials for their unique properties such as high water content, ease of functionalisation, and high biocompatibility. This highlight article describes the recent developments of hydrogels, with a large focus on the supramolecular variants, in their application for 3D cell cultures.

This work presents a practical and simple alternative method for studying the leaching of copper from copper sulfide. It is demonstrated, for the first time, that micro-patterned thin films can be used as a model system for studying mineral leaching of copper-bearing minerals directly by measuring changes in the film thickness using white light interferometric profilometry and changes in the film morphology and elemental composition using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy.

Ketoconazole (KCZ) is an antifungal compound and an active ingredient of anti-scaling shampoos and skin ointments. In this work, the cyclic voltammetric behaviour of KCZ was studied with a gold nanoparticle (AuNP)-modified glassy carbon (GC) electrode.

Peak separation of a long-length DNA aptamer complexed with its target via non-equilibrium capillary electrophoresis of equilibrium mixtures (NECEEM) and its enrichment through selection process cycles have been demonstrated.

O-(3,5-dinitrobenzoyloxy)benzohydroxamate crystallizes as its imino tautomer in the presence of dimethyl sulfoxide and its amide tautomer in the absence of dimethyl sulfoxide.

Novel strontium oxide/calcium oxide (SrO-CaO) mixed metal oxides heterogeneous catalyst is synthesized to highlight its catalytic potential for the transformation of Jatropha oil to green biofuels via an ultrasonic-assisted transesterification process.

Although PhI(OAc)₂ is known as an oxidizing agent, it can also serve as a reagent or a catalyst in different types of chemical reactions in organic synthesis. PhI(OAc)₂ is used in radical reactions, oxidation reactions, and in heterocycle synthesis. This paper reports some relevant and recent new uses of PhI(OAc)₂.

Oxidation of the biologically active compound d-penicillamine (Depen) by acidic bromate has been studied. It is oxidized as far as its sulfonic acid. ESI spectroscopy shows that Depen is oxidized through addition of oxygen atoms on the sulfur centre to successively yield sulfenic and sulfinic acids before the product sulfonic acid.

The colorimetric sensing of polycyclic aromatic hydrocarbons (PAHs) was achieved using a photochromic compound. This detection technology was highly sensitive (by absorbing UV radiation) and selective (using different excitation wavelengths). PAH mixtures were successfully identified, allowing fast in-field identification of spilled oil sources.

Convenient, multigram scale syntheses of FeCl(dppe)Cp* (pictured), FeCl(dppe)Cp, RuCl(dppe)Cp*, and RuCl(dppe)Cp are described.

Citric acid-coated magnetite nanoparticles Fe₃O₄ (nano-Fe₃O₄-CA) interacted with anthracyclines, and the aggregates (nano-Fe₃O₄-CA-drug) formed. Further studies indicated that the interactions between them were electrostatic and hydrophobic forces. Additionally, the cytotoxicity of nano-Fe₃O₄-CA-drug was investigated by cytotoxicity experiment and cell morphology study, which indicated that the nano-Fe₃O₄-CA-drug has a lower cytotoxicity than anthracyclines.

The facile transformation of aryl/heteroaryl nonaflates into corresponding amides via Pd-catalyzed aminocarbonylation using Mo(CO)₆ as a solid CO source under microwave-enhanced condition is reported. The method was found to be tolerant with respect to a diverse range of electronically biased aryl/heteroaryl nonaflates, and exceptional yields were obtained. The optimized protocol was further extended to a diverse range of amines.

The Diels–Alder reaction is one of the most powerful, well-established, and versatile reactions in organic chemistry; however, its application in certain settings remains a challenge as a result of functional group incompatibility. In this review, we examine the methods in which masked ketenes can be employed as dienophiles, taking particular note of applications in complex settings.

Effect of imidazolium cation (MIM⁺) on the electroreduction of CO₂ to CO was investigated by linear sweep voltammetry (LSV), cyclic voltammetry (CV), constant potential electrolysis (CPE), and density functional theory (DFT) computations. It is interesting to find that the catalytic effect of MIM⁺ is sensitive to the alkyl chain length on its N1-position.

Various glycosylation reactions were tried in an effort to synthesise β-linked tutin glycosides, found in toxic honeys. Cationic palladium-mediated glycosylation gave the α-linked tutin tetrabenzyl glucoside (5 : 1, α : β). Hydrogenolysis of the benzyl ether groups resulted in tutin double-bond migration. Epoxide opening and rearrangement were observed upon acetylation of the tutin glucoside.

Biomass deconstruction and conversion of sugar and lignin to high-value products are the essential steps in the implementation of next-generation lignocellulosic biorefineries. Understanding the interplay between conversion processes and the structure of lignocellulosic feedstocks is a critical point, warranting the development of feedstock engineering techniques and advanced characterization methods, in tandem with the deployment of tailored deconstruction and upgrading processes.

Two novel zinc coordination polymers have been synthesised and characterised. Their topological structures show 4-connected 8- and 3-fold interpenetrating 3D frameworks. Furthermore, they exhibit good photodegradation capability and photoluminescence properties.

A macroporous TiO₂ monolith-entrapped pipette-tip was developed for phosphorylated peptide enrichment with a detection limit of 1 ng mL^–1 and better enrichment efficiency compared with a commercial tip.

A novel norbornene-functional poly(lactide)s backbone-based redox-responsive prodrug, P(LA-g-mOEG)-b-P(LA-SS-PTX), was successfully synthesized by combination of ring-opening polymerization, click, ester, and condensation reactions. The self-assembled micelles formed from paclitaxel prodrugs displayed a spherical shape with appropriate sizes for enhanced permeability and retention effect and a narrow size distribution. With disulfide linkages, prodrug micells showed redox-responsive drug release behaviours in response to the intracellular level of reducing potential.

Two barium(ii) 2D coordination polymers, {[Ba(µ-H₂O)(H₂O)₂(µ-pyzdc)]}_n (1) and {[Ba(H₂O)₂(µ-Hpyzdc)(Hpyzdc)]2H₂O}_n (2) (pyzdcH₂ = pyrazine-2,3-dicarboxylic acid), were prepared by reaction of barium(ii) chloride dihydrate and pyzdcH₂ under slightly different pH values. The barium(ii) ion has distorted bicapped square antiprismatic coordination geometry in 1 and distorted tricapped trigonal prismatic geometry in 2.

Small interfering RNA (siRNA) is a class of therapeutic with extremely high potential. However, further understanding of how siRNA behaves in vivo is still required before significant uptake into clinical application. To this end, molecular imaging has been utilised to gain a better understanding of administered siRNA and delivery vehicle biodistribution and pharmacokinetics.

This paper describes a simple way to synthesize poly(caprolactone) or poly(siloxane-block-caprolactone) copolymers through anionic polymerization by employing lithium silanolates.

MnO_x-CeO₂/TiO₂-SiO₂ were prepared by an impregnation method and their selective catalytic reduction of NO with NH₃ at low temperature was evaluated. NO conversion of the MnO_x/TiO₂-SiO₂ catalyst could be improved by the addition of CeO₂ in the temperature range of 100–180°C. MnO_x-CeO₂/TiO₂-SiO₂ with 10 wt-% CeO₂ showed the highest activity with 96 % NO conversion at 180°C.

The generalized anomeric relationships in halocarbonyl isocyanates (1–3) and halocarbonyl azides (4–6) result from the cooperative effects of the hyperconjugative generalized anomeric effects (HC-GAE) and Pauli exchange-type repulsion (PETR). The electrostatic model associated with the dipole–dipole interactions (EM-DDI) and the attractive electrostatic interactions (AEIs) between the natural atomic charges have no significant effects on the conformational preferences in compounds 1–3 and 4–6.

Thiaoxaaza macrocycles incorporating NO₂S₂ (L¹) and NO₂S₃ (L²) donors were employed and their silver(i) nitrate complexation in solid and solution states was investigated.

CoWO₄/g-C₃N₄ was synthesized by precipitation and calcination, and used as a catalyst for oxidative desulfurization. In the process, CoWO₄/g-C₃N₄ showed excellent desulfurization activity and the desulfurization rate reached 92.9 %. Moreover, the catalyst could be recycled at least five times without any clear decrease in catalytic activity.

The kinetics of the nucleophilic substitution reactions of bis(N,N-diethylamino)phosphinic chloride with XC₆H₄NH₂(D)₂ are investigated in MeCN at 65.0°C. This study examines the substituent effects, deuterium kinetic isotope effects (DKIEs), and mechanism of the phosphoryl transfer reactions. A concerted S_N2 mechanism involving the predominant backside attack is proposed.

The anticancer metal complex [(1,10-phenanthroline)(1S,2S-diaminocyclohexane)platinum(ii)]²⁺ forms a supramolecular complex with multi-walled carbon nanotubes through π–π stacking.

A variety of different evolutionary mechanisms have allowed metalloenzymes to gain or enhance xenobiotic-degrading activity.

An orthogonal molecular interaction (OMI) system between a native hydrogen bond (H-bond) and a constructed halogen bond (X-bond) across the complex interface of oncogenic protein MDM2 with the p53 peptide was designed computationally. Fluorescence polarization assays revealed that the designed OMI system can considerably improve peptide binding affinity to MDM2.

Because it is an ozone-depleting substance, carbon tetrachloride is slowly disappearing from laboratories but it is still used in industry. There is more carbon tetrachloride in the upper atmosphere than can be accounted for by estimated releases from anthropogenic activities. The figure shown is adapted, with permission of the authors, from a recent report.

The construction of the first Salen-type 3D lanthanide complex using Salen ligands and mixed lanthanide counter-ions is described.