Mononuclear and dinuclear trimethylplatinum(IV) iodide complexes of 3-substituted pyridines

New Journal of Chemistry
Reaction of tetrameric trimethylplatinum(IV) iodide with excess of 3-substituted pyridines in chloroform afforded mononuclear complexes, [PtMe3L2I] (L = 3-CNpy, 3-Brpy, 3-MeOpy, 3-Mepy and 3-Etpy). The complexes have been characterized by 1H NMR, CHN analysis and X-ray single crystal structure analysis. The mononuclear complexes undergo reaction with trimethylplatinum(IV) iodide in chloroform to form corresponding dinuclear forms (both syn and anti). A comparison of both the mononuclear and dinuclear forms in solution for a particular pyridine substituent have been studied in detail with the help of 1H NMR spectroscopy, ably supported by DFT computational studies. The investigation further shows the influence of the pyridine substituent on controlling the mode of the reaction. The crystal structures of two dinuclear complexes, syn-[PtMe3(3-CNpy)I]2 and anti-[PtMe3(3-Brpy)I]2, have also been described here.Read more

MOLECULAR RECOGNITION OF AN ACYL-ENZYME INTERMEDIATE ON THE LIPASE B FROM Candida antarctica

Catalysis Science & Technology
This investigation provides evidences of the acyl enzyme species involved in the interaction of R/S-ketoprofen with the lipase B from Candida antarctica. The interaction between the profen and the enzyme was studied by in situ Time-Resolved ATR-FTIR both in static and transient conditions. Particularly, modulation excitation spectroscopy (MES) with phase sensitive detection (PSD) allowed to univocally distinguishing the signals belonging to the interaction between ketoprofen and the enzyme from the strong background signals. These experimental tools coupled with theoretical DFT analysis allowed to propose various species due to the interaction of ketoprofen with serine through H bonding (without reaction) and the acyl enzyme species (ester bond formation) that are the intermediates in the biocatalytic assisted esterification and hydrolysis using lipases.Read more

Difference Hirshfeld fingerprint plots: A tool for studying polymorphs

CrystEngComm
A new tool has been developed to help elucidate the differences in packing between different polymorphs, especially when the differences of interest are small. The technique builds upon the Hirshfeld fingerprint plot pioneered by Spackman and co-workers by subtracting the value at every point in a fingerprint plot from the value at every point in another. This is found to reveal differences that are not readily apparent to the eye. By summing the absolute values of these differences, a quantitative measure of the difference between two fingerprint plots can be obtained. The technique was applied to Ni and Cu trans-bis(2-hydroxy-5-methylphenonethanoneoximato) complexes determined at two temperatures, with the Ni complex displaying temperature-dependent polymorphism. Difference Hirshfeld fingerprint plots were also generated for calculated structures from DFT simulations that were performed on the experimental structures. These demonstrated that the simulations reproduced the fine...  Read more

FLP Reduction and Hydroborations of Phenanthrene o-Iminoquinones and α-Diimines

Dalton Transactions
Redox active, or non-innocent, ligands containing O or N heteroatoms are frequently used in transition metal complexes, imparting unique catalytic properties, but have seen comparatively limited use in the chemistry of group 13 elements. In this article we report the frustrated Lewis pair (FLP) hydrogenations and hydroboration of an N-aryl-phenanthrene-o-iminoquinone and two N,N’-diaryl-phenanthrene α-diimines. These reactions exploit B(C6F5)3/H2, HB(C6F5)2 and H2BC6F5·SMe2 to give a series of derivatives including 1,3,2-oxaza- and diazaboroles and borocyclic radicals. The reaction pathways leading to these products are outlined and supported by DFT-calculations and experimental insight. The modular and unusual synthetic strategies described herein give access to new boroles as well as air-stable boron-containing radicals, thus extending the chemistry of redox active ligands in main group systems.Read more

Formation of mono- and binuclear neodymium(III)-gluconate complexes in aqueous solutions in the pH range of 2–8

Dalton Transactions
The complex formation between Nd(III) and D-gluconate (Gluc–) is of relevance in modelling the chemical equilibria of radioactive waste repositories. In the present work, the formation of NdpGlucqH–r complexes at 25 °C and pH = 2–8 was studied via spectrophotometry, potentiometry, freezing point depression, conductometry and NMR spectroscopy. In addition to the four mononuclear complexes (pq–r = 110, 120, 130 and 11–2), the formation of two binuclear, so far unknown complexes (pq–r = 23–2 and 24–2) was revealed. Between pH = 5.5 and 7, with the increasing metal ion and ligand concentrations, the Nd2Gluc3H–2+ species becomes progressively predominant. Under the conditions characteristic to waste repositories, however, the formation of these complexes can be neglected. Regarding the binding sites of Gluc–, the C2–OH and C3–OH groups, in addition to the carboxylate ion, were identified from 1H and 13C spectroscopic measurements. Above pH = 6, the metal-ligand...  Read more

Unveiling the effects of in situ generated arene anion radical and imine radical on catecholase like activity: A DFT supported experimental investigation

Dalton Transactions
Two new dinuclear nickel(II) complexes namely [Ni2(L1)2(OAc)2(H2O)2].CH3CN (1) and [Ni2(L2)2(SCN)2(CH3OH)2].CH3OH (2) have been synthesized from designed Schiff-base ligand 4-Bromo-2-[(2-hydroxy-1,1-dimethyl-ethylimino)-methyl]-phenol (HL1) and its reduced analogue 4-Bromo-2-[(2-hydroxy-1,1-dimethyl-ethylamino)-methyl]-phenol (HL2), respectively. Both 1 and 2 have been characterised by usual physicochemical techniques (UV-Vis, FT-IR, ESI-MS study, Single crystal XRD) and their variable temperature magnetic study has been performed. The nickel(II) centres in the dinuclear complexes 1 and 2 are antiferromagnetically coupled through participation of bridging phenoxyl oxygen. In acetonitrile solution both 1 and 2 retain their dinuclear structural integrity as is evident from ESI-MS study. Catecholase like activity of 1 and 2 have been performed in acetonitrile medium using 3, 5 -di-tert-butylcatechol (3, 5-DTBC) as model substrate. Complex 1 shows higher catalytic activity than that of...  Read more

Photoswitching storage of guest molecules in metal-organic framework for photoswitchable catalysis: exceptional product, ultrahigh photocontrol, and photomodulated size selectivity

Journal of Materials Chemistry A
MOF materials as new emerged catalyst have been demonstrated to show high catalytic activity and size-, regio-, and stereo-selectivity. However, how to artifically controlling the catalytic process by convenient external stimulus such as light is still unexploited. Such photocontrol over organic reaction may enable switchable catalytic activities and/or selectivities, consequently producing desired products from a pool of building blocks according to the order and type of stimuli applied. In this work, we present a novel MOF catalyst, which not only offers ultrahigh photocontrol with the ON/OFF ratio as high as 407, but also displays disparate photomodulation in reaction kinetics towards various aldehyde substrates in light of their sizes, thus creating the first example in MOFs showing photoswitchable catalysis. The origin, as unveiled by photoswitching adsorption experiments and density functional theory calculations, is due to photoswitching storage of guest molecules in...  Read more

Conductive Metal Adatoms Adsorbed on Graphene Nanoribbons: A First-Principles Study of Electronic Structures, Magnetization and Transport Properties

Journal of Materials Chemistry C
Using density functional theory (DFT) in combination with non-equilibrium Green’s functions, we have investigated the electronic structures, magnetization, and quantum transport properties of zigzag graphene nanoribbons (ZGNRs) functionalized with conventional conductive metal adatoms (Al, Cu, Ag and Au). On the basis of the adsorption energies, our simulation demonstrates that Al and Cu adatoms are chemically bonded with ZGNR, while the adsorptions for Ag and Au are between weak chemisorption and strong physisorption. The properties of charge transfer and magnetic moment are in reasonable agreement with the previous calculations. The adsorption of metal adatoms induce a net magnetic moment -1 μB to 6ZGNR-metal systems. On the other hand, the transport studies of metal adatoms adsorbed ZGNR suggest that the metal adatoms play an important role in the transport properties of devices and exhibit different effects on the transport properties of 6ZGNR-based and 7ZGNR-based devices. The...  Read more

How to design ultraviolet emitting persistent materials for potential multifunctional applications: a living example of NaLuGeO4:Bi3+,Eu3+ phosphor

Journal of Materials Chemistry C
We exhibit a living story to design the ultraviolet (UV) emitting persistent (PersL) material dynamically as required. Understanding the luminescence mechanism of Bi3+, the occupation rules of sites, the density functional theory (DFT) calculations and an empirical energy level scheme guide us to select the most appropriate emitters, host and traps. Finally, the NaLuGeO4:Bi3+,Eu3+ phosphor is successfully designed. The experimental results indicate that the NaLuGeO4:Bi3+,Eu3+ material is indeed able to emit excellent UV PersL, which can be recorded for more than 63h. This exciting result is sufficiently encouraging for the initiation of a more thorough investigation. Accordingly, the excitation temperature-dependent and fading thermoluminescence experiments are conducted, and the traps properties are deeply studied by the initial rising method. The results reveal the PersL mechanism and the significant role of Eu3+ codopants as foreign traps. On the basis of this work, it clearly...  Read more

Amplification of Surface-Enhanced Raman Scattering Due to Substrate-Mediated Localized Surface Plasmons in Gold Nanodimers

Journal of Materials Chemistry C
Surface-enhanced Raman scattering (SERS) is ubiquitous in chemical and biochemical sensing, imaging and identification. Maximizing SERS enhancement is a continuous effort focused on the design of appropriate SERS substrates. Here we show that significant improvement in a SERS signal can be achieved with substrates combining localized surface plasmon resonances and a nonresonant plasmonic substrate. By introducing a continuous gold (Au) film underneath Au nanodimers antenna arrays, an over 10-fold increase in SERS enhancement is demonstrated. Triangular, rectangle and disc dimers were studied, with bowtie antenna providing highest SERS enhancement. Simulations of electromagnetic field distributions of the Au nanodimers on the Au film support the observed enhancement dependences. The hybridization of localized plasmonic modes with the image modes in a metal film provides a straightforward way to improve SERS enhancement in designer SERS substrate.Read more

Rapid contrast matching by microfluidic SANS

Lab on a Chip
We report a microfluidic approach to perform small angle neutron scattering (SANS) measurements of contrast variation and matching, extensively employed in soft and biological matter research. We integrate a low scattering background microfluidic mixer and serpentine channel in a SANS beamline to yield a single phase, continuous flow, reconfigurable liquid cell. By contrast with conventional, sequential measurements of discrete (typically 4-6) solutions of varying isotopic solvent composition, our approach continually varies solution composition during SANS acquisition. We experimentally and computationally determine the effects of flow dispersion and neutron beam over-illumination of microchannels in terms of the composition resolution and precision. The approach is demonstrated with model systems: H2O/D2O mixtures, a surfactant (sodium dodecyl sulfate, SDS), a triblock copolymer (pluronic F127), and silica nanoparticles (Ludox) in isotopic aqueous mixtures. The system is able to...  Read more

A Fluorescein-Based Chemosensor for Relay Fluorescence Recognition of Cu(II) Ions and Biothiols in Water and its Applications to Molecular Logic Gates and Living Cell Imaging

Organic & Biomolecular Chemistry
Relay recognition of copper(II) ions and biothiols via a fluorescence “on−off−on” cascade was designed and realized as a new sequential combination of cation and small molecule. Probe 1 bearing a fluorescein skeleton was thus synthesized and performed well in 100% HEPES buffer (pH = 7.0) solution, as a highly sensitive, selective fluorescence sensor for Cu2+. The limit of detection (LOD, 0.017 ppm) was obtained, and this value is much lower than 1.3 ppm allowed by US EPA. The 1:1 complex generated from a fast sensing of Cu2+ when excited at 491 nm, showed good relay recognition for biothiols (i.e., Cys, Hcy and GSH with low detection limits of 0.12 μM, 0.036 μM and 0.024 μM, respectively) via remarkable fluorescence enhancement. The origin of this relay process was disclosed through ESI−MS and corresponding density function theory (DFT) computations. Notably, probe 1 can be utilized for a construction of molecular logic gate with IMPLICATION function by using the above...  Read more

Investigating the Optical Properties of BOIMPY Dyes with ab initio Tools

Physical Chemistry Chemical Physics
Using a computational approach combining the Time-Dependent Density Functional Theory (TD-DFT) and the second-order Coupled Cluster (CC2) approaches, we investigate the spectral properties of a large panel of BOIMPY dyes. BOIMPY derivatives constitute a new class of fluorophores that appeared only very recently [Angew. Chem. Int. Ed., 2016, 55, 13340-13344] and display intriguing properties. First, we show that theory is able to reproduce the experimental 0-0 energies with a reasonable accuracy, and more importantly an excellent consistency (R=0.99). Next, by analyzing the nature of the excited-states, we show that the first electronic transition does not imply a significant charge-transfer character and significantly differs from the one of the parent BODIPYs. Third, we unravel the vibrational modes responsible for the specific band shapes of the BOIMPY derivatives. Finally, using theory to design new compounds, we propose new substitution patterns leading to redshifted absorption...  Read more

Temperature Profiles and Heat Fluxes Observed in Molecular Dynamics Simulations of Force-Driven Liquid Flows

Physical Chemistry Chemical Physics
This paper concentrates on the unconventional temperature profiles and heat fluxes observed in non-equilibrium molecular dynamics (MD) simulations of force-driven liquid flows in nano-channels. Using MD simulations of liquid argon flows in gold nano-channels, we investigate manifestation of the first law of thermodynamics for the MD system, and compare it with that of the continuum fluid mechanics. While the energy equation for the continuum system results in heat conduction determined by viscous heating, the first law of thermodynamics in the MD system includes an additional slip-heating term. Interaction strength between argon and gold molecules are varied in order to investigate the effects of slip-velocity on the slip-heating term and the resulting temperature profiles. Heat fluxes and temperature profiles from “continuum”, “continuum augmented with slip-heating”, and “heat conduction due to power input by the driving force” are modeled and compared with the MD...  Read more

Atomistic non-adiabatic dynamics of the LH2 complex with a GPU-accelerated ab initio exciton model

Physical Chemistry Chemical Physics
We recently outlined an efficient multi-tiered parallel ab initio excitonic framework that utilizes time dependent density functional theory (TDDFT) to calculate ground and excited state energies and gradients of large supramolecular complexes in atomistic detail – enabling us to undertake non-adiabatic simulations which explicitly account for the coupled anharmonic vibrational motion of all the constituent atoms in a supramolecular system. Here we apply that framework to the 27 coupled bacterio-cholorophyll-a chromophores which make up the LH2 complex, using it to compute an on-the-fly nonadiabatic surface-hopping (SH) trajectory of electronically excited LH2. Part one of this article is focussed on calibrating our ab initio exciton Hamiltonian using two key parameters: a shift δ, which corrects for the error in TDDFT vertical excitation energies; and an effective dielectric constant ε, which describes the average screening of the transition-dipole coupling between chromophores....  Read more

Sodium – Carboxylate Contact Ion Pair Formation Induces Stabilization of Palmitic Acid Monolayers at High pH

Physical Chemistry Chemical Physics
Sea spray aerosols (SSA) are known to have an organic coating that is mainly composed of fatty acids. In this study, the effect of pH and salt on the stability and organization of a palmitic acid (PA) monolayer is investigated by surface vibrational spectroscopy and molecular dynamics simulations. Results indicate that alkyl chain packing becomes more disordered as the carboxylic headgroup becomes deprotonated. This is associated with packing mismatch of charged and neutral species as charged headgroups penetrate deeper into the solution phase. At pH 10.7, when the monolayer is ~99% deprotonated,, palmitate (PA–) molecules desorb and solubilize into the bulk solution where there is spectroscopic evidence for aggregate formation. Yet, addition of 100 mM NaCl to the bulk solution is found to drive PA– molecules to the aqueous surface. Free energy calculations show that PA– molecules become stabilized within the interface with increasing NaCl concentration. Formation of contact...  Read more

NMR Probing and Visualization of Correlated Structural Fluctuations in Intrinsically Disordered Proteins

Physical Chemistry Chemical Physics
A novel statistical analysis of paramagnetic relaxation enhancement (PRE) and paramagnetic relaxation interference (PRI) based nuclear magnetic resonance (NMR) data is proposed based on computation of correlation matrices. The technique is demonstrated with an example to the intrinsically disordered protein (IDP) Osteopontin (OPN) and the brain acid soluble protein 1 (BASP1). The correlation analysis visualizes in detail the subtleties of conformational averaging in IDPs and highlights the presence of correlated structural fluctuations of individual sub-domains in IDPs.Read more

Buckling behaviour of composites with double wall nanotubes from carbon and phosphorous

Physical Chemistry Chemical Physics
Due to weak interaction among phosphorus atoms in black phosphorene, the nanotube obtained by curling single-layer black phosphorus is not as stable as a carbon nanotube (CNT) at finite temperature. In the present work, we recommend a new 1D composite material with a double-wall nanotube (DWNT) from a black phosphorus nanotube (BPNT) and a CNT. The dynamic response of the composite DWNTs is simulated using molecular dynamics approach. Effects of factors including temperature, slenderness and configurations of DWNTs on dynamic behavior of the composite are discussed. Comparing with a single-wall BPNT, the composite DWNTs under uniaxial compression shows some unique properties. When the BPNT is embedded in a CNT which will not only isolate BPNT from the ambient condition, but also improve the capability of axial deformation of BPNT, the system will not collapse rapidly even if the BPNT has been buckled.Read more

Metal–organic frameworks for the removal of toxic industrial chemicals and chemical warfare agents

Chemical Society Reviews
Owing to the vast diversity of linkers, nodes, and topologies, metal–organic frameworks can be tailored for specific tasks, such as chemical separations or catalysis. Accordingly, these materials have attracted significant interest for capture and/or detoxification of toxic industrial chemicals and chemical warfare agents. In this paper, we review recent experimental and computational work pertaining to the capture of several industrially-relevant toxic chemicals, including NH3, SO2, NO2, H2S, and some volatile organic compounds, with particular emphasis on the challenging issue of designing materials that selectively adsorb these chemicals in the presence of water. We also examine recent research on the capture and catalytic degradation of chemical warfare agents such as sarin and sulfur mustard using metal–organic frameworks.Read more

Optimized synthesis of π-extended squaraine dyes relevant to organic electronics by direct (hetero)arylation and Sonogashira coupling reactions

Organic & Biomolecular Chemistry
This study reports on the synthesis and characterization of four molecular π-extended squaraine compounds relevant to the field of organic electronics. The compounds each consist of a bis-indole squaraine core end-capped with indoloquinoxaline units employing three different bridging units, namely thiophene, thiazole, and acetylene. Compound 10 bears a thiophene bridge, 11 consists of a thiophene bridge and fluorinated indoloquinoxaline terminal units, and compounds 12 and 13 are bridged by thiazole and acetylene, respectively. The final compounds are constructed using the atom economical direct (hetero)arylation or the classic Sonogashira carbon-carbon bond formation protocols. Each carbon-carbon bond forming reaction employing thiophene bridges (i.e. synthesis of compounds 10 and 11) has been optimized using the stable and reusable silica supported Pd catalyst, SiliaCat® DPP-Pd, streamlining the synthetic procedure. While compounds 12 and 13 were also accessible using the...  Read more