Structural,electronic, and magnetoresponsive properties of triangular lanthanide clusters and their free‐standing nitrides

The molecular and electronic structures, stabilities, bonding features, and magnetoresponsive properties of three‐membered [c‐Ln₃]^+/0/? (Ln = La, Ce, Pr, Nd, Gd, Lu) and heterocyclic six‐membered [c‐Ln₃E₃]^q (Ln = La, Ce, Pr, Nd, Gd, Lu; E = C, N; q = 0 or 1) rings have been investigated by means of electronic structure calculation methods at the DFT level. The [c‐Ln₃]^+/0/? clusters are predicted to be bound with respect to dissociation to their constituent atoms, the estimated binding energies ranging from 45.8 to 2056.4 kJ/mol. The [c‐Ln₃] rings capture easily a planar three‐coordinated nitrogen atom at the center or above the center of the ring yielding the lanthanide nitride clusters [c‐Ln₃(μ₃‐N)] adopting a planar geometry, except [c‐La₃(μ₃‐N)] which exhibits pyramidal geometry. The [c‐Ln₃(μ₃‐N)] clusters are predicted to be bound, with respect to dissociation to N (⁴S) atom and [c‐Ln₃] clusters in their ground states, the binding energies ranging from 53.9 to 257.9 kcal/mol. The six‐membered [c‐Ln₃E₃]^q rings are predicted to be bound with respect to dissociation to LnE^q monomers in their ground states with dissociation energies in the range of 173.8 to 318.0 kcal/mol. Calculation of the NICS_zz‐scan curves of the clusters predicted a “hermaphrodic” magnetic response of the [c‐Ln₃]^+/0/? and heterocyclic six‐membered [c‐Ln₃E₃]^q rings, manifested by the coexistence of successive diatropic (aromatic) and paratropic (antiaromatic) zones. The [c‐La₃]^+/0/? and [c‐Lu₃]^? are predicted to be weakly antiaromatic, the [c‐Lu₃]^0/+, [c‐Lu₃C₃]⁺, and [c‐Lu₃N₃] double (σ+π) aromatic, and the [c‐Gd₃C₃] and [c‐Gd₃N₃]⁺ rings (σ+δ)‐aromatic systems. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011     

PHI: A powerful new program for the analysis of anisotropic monomeric and exchange‐coupled polynuclear d‐ and f‐block complexes

A new program, PHI, with the ability to calculate the magnetic properties of large spin systems and complex orbitally degenerate systems, such as clusters of d‐block and f‐block ions, is presented. The program can intuitively fit experimental data from multiple sources, such as magnetic and spectroscopic data, simultaneously. PHI is extensively parallelized and can operate under the symmetric multiprocessing, single process multiple data, or GPU paradigms using a threaded, MPI or GPU model, respectively. For a given problem PHI is been shown to be almost 12 times faster than the well‐known program MAGPACK, limited only by available hardware. © 2013 Wiley Periodicals, Inc.     

Energies for cyclic and acyclic aggregations of adamantane and diamantane units sharing vertices,edges, or six‐membered rings

Diamondoids are hydrocarbons having a carbon scaffold comprised from polymer‐like composites of adamantane cages. This article describes computed total energies and “SWB‐tension” energies (often referred to as “strain” energies) for species having n adamantane or diamantane units sharing pairwise: one carbon atom (spiro‐[n]adamantane or spiro‐[n]diamantane); one C? C bond (one‐bond‐sharing‐[n]adamantane or one‐bond‐sharing‐[n]diamantane); or one chair‐shaped hexagon of carbon atoms (1234‐helical‐cata‐[n]diamantanes). Each of the five investigated polymer‐like types is considered either as an acyclic or a cyclic chain of adamantane‐ or diamantane‐unit cages. With increasing n values, SWB‐tension energies for acyclic aggregates are found to increase linearly, while the net SWB‐tension energies of cyclic aggregates often go thru a minimum at a suitable value of . In all five cases, a limiting common energy per unit ( ) is found to be approached by both cyclic and acyclic chains as , as revealed from plots of versus 1/n for acyclic chains and of versus 1/n² for cyclic chains. © 2015 Wiley Periodicals, Inc.     

Nitroxide‐mediated homo‐ and block copolymerization of styrene and multifunctional acryl‐ and methacryl derivatives

The ability of different alkoxyamines ( I1 , I2 , I3 , I4 , and I5 ) to initiate controlled radical polymerization of styrene was evaluated. Among them, 2‐hydroxymethyl‐2‐[(2‐methyl‐1‐phenyl‐propyl)‐(1‐phenyl‐ethoxy)‐amino]‐propane‐1,3‐diol ( I5 ) gave the highest polymerization rate of styrene, and the best control over the molecular weight and the molecular weight distribution of polystyrene. Kinetic studies confirmed that with initiator I5 the polymerization of styrene proceeded in a controlled way. The controlled radical homopolymerization of multifunctional acryl‐ and methacryl derivatives using initiator I5 could not be realized as demonstrated by the high polydispersities (PD) obtained. However, it was possible to polymerize multifunctional acryl‐ and methacryl derivatives using a polystyrene macroinitiator ( Pst ) and, thus, novel amphiphilic block copolymers with a narrow molecular weight distribution were obtained. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1873–1882, 2005     

The structure of azines derived from C‐formyl‐1H‐imidazoles in solution and in the solid state: tautomerism,configurational and conformational studies

The structures of three azines derived from 2‐formylimidazole, 4(5)‐formylimidazole, and 4(5)‐formyl‐5(4)‐methylimidazole have been determined in solution and in the solid state. Density Functional Theory (DFT) Polarizable Continuum Model (PCM) calculations (geometries, energies, and chemical shifts), NMR [solution and cross polarization magic‐angle spinning (CPMAS)], and X‐ray crystallography [azine of 4(5)‐formylimidazole] have been used. The configuration around the central C = N bonds has been determined and some insights about prototropic tautomerism and conformation have been gained. Copyright © 2013 John Wiley & Sons, Ltd.     

A rapid and sensitive LC–MS/MS method for quantification of quercetin‐3‐O‐β‐d‐glucopyranosyl‐7‐O‐β‐d‐gentiobioside in plasma and its application to a pharmacokinetic study

A rapid and sensitive LC–MS/MS method with good accuracy and precision was developed and validated for the pharmacokinetic study of quercetin‐3‐O‐β‐d ‐glucopyranosyl‐7‐O‐β‐d ‐gentiobioside (QGG) in Sprague–Dawley rats. Plasma samples were simply precipitated by methanol and then analyzed by LC–MS/MS. A Venusil® ASB C₁₈ column (2.1 × 50 mm, i.d. 5 μm) was used for separation, with methanol–water (50:50, v/v) as the mobile phase at a flow rate of 300 μL/min. The optimized mass transition ion‐pairs (m/z) for quantitation were 787.3/301.3 for QGG, and 725.3/293.3 for internal standard. The linear range was 7.32–1830 ng/mL with an average correlation coefficient of 0.9992, and the limit of quantification was 7.32 ng/mL. The intra‐ and inter‐day precision and accuracy were less than ±15%. At low, medium and high quality control concentrations, the recovery and matrix effect of the analyte and IS were in the range of 89.06–92.43 and 88.58–97.62%, respectively. The method was applied for the pharmacokinetic study of QGG in Sprague–Dawley rats. Copyright © 2016 John Wiley & Sons, Ltd.     

HPLC determination of acidic d‐amino acids and their N‐methyl derivatives in biological tissues

d ‐Aspartate (d ‐Asp) and N‐methyl‐d ‐aspartate (NMDA) occur in the neuroendocrine systems of vertebrates and invertebrates, where they play a role in hormone release and synthesis, neurotransmission, and memory and learning. N‐methyl‐d ‐glutamate (NMDG) has also been detected in marine bivalves. Several methods have been used to detect these amino acids, but they require pretreatment of tissue samples with o‐phthaldialdehyde (OPA) to remove primary amino acids that interfere with the detection of NMDA and NMDG. We report here a one‐step derivatization procedure with the chiral reagent N‐α‐(5‐fluoro‐2,4‐dinitrophenyl)‐(d or l )‐valine amide, FDNP‐Val‐NH₂, a close analog of Marfey's reagent but with better resolution and higher molar absorptivity. The diastereomers formed were separated by HPLC on an ODS‐Hypersil column eluted with TFA/water–TFA/MeCN. UV absorption at 340 nm permitted detection levels as low as 5–10 pmol. d ‐Asp, NMDA and NMDG peaks were not obscured by other primary or secondary amino acids; hence pretreatment of tissues with OPA was not required. This method is highly reliable and fast (less than 40 min HPLC run). Using this method, we detected d ‐Asp, NMDA and NMDG in several biological tissues (octopus brain, optical lobe and bucchal mass; foot and mantle of the mollusk Scapharca broughtonii), confirming the results of other researchers. Copyright © 2009 John Wiley & Sons, Ltd.     

Substituent effect on structure,electron density,and intramolecular hydrogen bonding in nitroso‐oxime methane

Density functional calculations with Beck's three‐parameter hybrid method using the correlation functional of Lee, Yang, and Parr (B3LYP) were carried out for investigation of the intramolecular hydrogen bond strength in Nitroso‐oxime methane and its derivatives. Also, vibrational frequencies for them were calculated at the same level of theory. The π‐electron delocalization parameter (Q) and as a geometrical indicator of a local aromaticity, the geometry‐based harmonic oscillator measure of aromaticity index has been applied. Additionally, the linear correlation coefficients between substituent constants and selected parameters in R position have calculated. The obtained results show that the hydrogen bond strength is mainly governed by the resonance variations inside the chelate ring induced by the substituent groups. The topological properties of the electron density distributions for O? H ··· O intramolecular bridges have been analyzed in terms of the Bader theory of atoms in molecules (AIM). Correlations between the H‐bond strength and topological parameters have been also studied. The electron density (ρ) and Laplacian (?²ρ) properties, estimated by AIM calculations, show that O ··· H bond have low ρ and negative (?²ρ) values (consistent with covalent character of the HBs), whereas O? H bond have positive (?²ρ) Furthermore, the analysis of hydrogen bond in this molecule and its derivatives by quantum theory of natural bond orbital (NBO) methods fairly support the ab initio results. Natural population analysis data, the electron density, and Laplacian properties as well as υ(O? H) and γ(O? H) were further used for estimation of the hydrogen bonding interactions and the forces driving their formation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

The mutual effect of a carbonyl polar bond and an endocyclic oxygen on the 1JC‐F coupling constant of fluorinated six‐membered rings

The ¹J_C‐F coupling constant can be useful to probe the conformational landscape of organofluorine compounds and the intramolecular interactions governing the stereochemistry of these compounds. Neighboring oxygen electron lone pairs and a carbonyl group relative to a C─F bond affect this coupling constant in an opposite way, and therefore, analysis of the interactions involving these entities simultaneously indicates which effect dominates ¹J_C‐F. Spin–spin coupling constant calculations for a series of fluorinated tetrahydropyrans, cyclohexanones, and dihydropyran‐3‐ones indicated that an electrostatic/dipolar interaction between the C─F and C═O bonds is more important than the steric interaction between the C─F bond and the oxygen electron lone pairs. An intuitive consequence of such outcome is that this interaction not only drives the coupling constant but can also be taken into account when aiming at the stereochemical control of functionalized organofluorine compounds.     

Synthesis of photocleavable poly(methyl methacrylate‐block‐d‐lactide) via atom‐transfer radical polymerization and ring‐opening polymerization

The synthesis and characterization of a photocleavable block copolymer containing an ortho‐nitrobenzyl (ONB) linker between poly(methyl methacrylate) and poly(d ‐lactide) blocks is presented here. The block copolymers were synthesized via atom transfer radical polymerization (ATRP) of MMA followed by ring‐opening polymerization (ROP) of d ‐Lactide and ROP of d ‐lactide followed by ATRP of MMA from a difunctional photoresponsive ONB initiator, respectively. The challenges and limitations during synthesis of the photocleavable block copolymers using the difunctional photoresponsive ONB initiator are discussed. The photocleavage of the copolymers occurs under mild conditions by simple irradiation with 302 nm wavelength UV light (Relative intensity at 7.6 cm: 1500 μW/cm²) for several hours. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4309–4316     

Design,Sonosynthesis, Quantum‐Chemical Calculations,and Evaluation of New Mono‐ and Bis‐pyridine Dicarbonitriles as Antiproliferative Agents

A highly efficient, simple, and clean single‐step sonosynthetic procedure has been sophisticated for assembling new series of mono‐ and bis‐pyridine dicarbonitriles from ketones, HCl, and tetracyanoethylene. The presented protocol is applicable for the preparation of a broad range of uniquely substituted pyridine dicarbonitriles and seems to be superior in comparison with other previously reported methods. The antiproliferative impact of the newly synthesized derivatives was screened towards three representative cancer cell lines (MCF‐7, A549, and HCT116). Most of the evaluated derivatives showed a moderate to excellent anti‐proliferative activity towards the selected cell lines. Of these, compounds 4h , 4k , 10 , 12a , and 12b showed both potent anticancer activity (IC₅₀<10 μM) and lower cytotoxic effect (IC₅₀ > 58 μM) on non‐tumorigenic cells (MCF‐10A and NCM460), suggesting their promising potential to be lead molecules for future antitumor drug discovery. The structure‐activity relationships have been also discussed. Moreover, quantum chemical studies based on Density Functional Theory (DFT) of the synthesized compounds were investigated and found to be consistent with the in vitro inhibitory activities.     

1,3,5‐Triethynylbenzene and melamine as monomers to synthesize three‐dimensional network porous aromatic frameworks based silica/florisil for determination of carbendazim and thiabendazole in spinach

In this study, the new and efficient three‐dimensional network porous aromatic frameworks materials called Silica‐PAFs‐a, Florisil‐PAFs‐a, Silica‐PAFs‐b, and Florisil‐PAFs‐b were first synthesized. The properties of materials were analyzed by five characterization methods. The materials were used as adsorbents in pipette‐tip solid‐phase extraction for the effective determination of carbendazim and thiabendazole in spinach sample. Meanwhile, the obtained materials were tested by static adsorption and dynamic adsorption. The result showed that the specific surface area of materials greatly increased after introducing three‐dimensional network porous aromatic frameworks. Microstructural modification exposed a large number of amino reactive groups that made them have a better adsorption amount for the two targets. The calibration graphs of carbendazim and thiabendazole in methanol were linear over 0.10–300.0 µg/mL, and the limits of detection and quantification were 0.00546 and 0.0182 µg/mL, and 0.00741 and 0.0247µg/mL respectively. A reliable analytical method was developed for recognition targets in spinach sample by Silica‐PAFs‐b with satisfactory extraction recoveries (96.25 and 100.51%). The proposed method using the material was applied for trace analysis of the carbendazim and thiabendazole residue.     

Pallada‐ and platinacycle complexes of phosphorus ylides; synthesis,X‐ray characterization,theoretical and electrochemical studies and application of Pd(II) complexes as catalyst in Suzuki‐Miyaura coupling reaction

The new unsymmetrical phosphonium salts [Ph₂PCH₂PPh₂CH₂C(O)C₆H₄R]Br (R= m ‐Br ( S ₁ ) and p ‐CN ( S ₂ )) were synthesized in the reaction of 1,1‐bis(diphenylphosphino)methane (dppm) and BrCH₂C(O)C₆H₄R (R= m ‐Br and p ‐CN) ketones, respectively. Further treatment with NEt₃ gave the α‐keto stabilized phosphorus ylides Ph₂PCH₂PPh₂C(H)C(O)C₆H₄R (R= m ‐Br ( Y ₁ ) and p ‐CN ( Y ₂ )). These ligands were reacted with [MCl₂(cod)] (M= Pd and Pt; cod= 1,5‐cyclooctadiene) to give the pallada‐ and platinacycle complexes [MCl₂(Ph₂PCH₂PPh₂C(H)C(O)C₆H₄R)] (M= Pd, R= m ‐Br ( 3 ); R= p ‐CN ( 4 ) and M= Pt, R= m ‐Br ( 5 ); R= p ‐CN ( 6 )). Cyclic voltammetry, elemental analysis, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic methods were used for characterization of the obtained compounds. Further, the structure of complexes 3 and 4 were characterized crystallographically. Palladacycles 3 and 4 were proved to be excellent catalysts for the Suzuki‐Miyaura coupling reactions of various aryl chlorides and arylboronic acids in mixed DMF/H₂O media. Also, the bonding situations between two interacted fragments [PtCl₂] and Y ₁ and Y ₂ ligands in platinacycles 5 and 6 were investigated based on DFT method by using NBO, EDA and ETS‐NOCV analysis.     

Synthesis,crystal structure and photophysical properties of 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene: a new π building block

A dimerized 1,3‐diazaazulene derivative, namely 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene [or 2,2′‐(1,4‐phenylene)bis(1,3‐diazaazulene)], C₂₂H₁₄N₄, (I), has been synthesized successfully through the condensation reaction between 2‐methoxytropone and benzene‐1,4‐dicarboximidamide hydrochloride, and was characterized by ¹H NMR and ¹³C NMR spectroscopies, and ESI–MS. X‐ray diffraction analysis reveals that (I) has a nearly planar structure with good π‐electron delocalization, indicating that it might serve as a π building block. The crystal belongs to the monoclinic system. One‐dimensional chains were formed along the a axis through π–π interactions and adjacent chains are stabilized by C—H…N interactions, forming a three‐dimensional architecture. The solid emission of (I) in the crystalline form exhibited a 170 nm red shift compared with that in the solution state. The observed optical bandgap for (I) is 3.22 eV and a cyclic voltammetry experiment confirmed the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The calculated bandgap for (I) is 3.37 eV, which is very close to the experimental result. In addition, the polarizability and hyperpolarizability of (I) were appraised for its further application in second‐order nonlinear optical materials.     

Double‐hydrophilic block copolymer for encapsulation and two‐way pH change‐induced release of metalloporphyrins

A double hydrophilic block copolymer composed of poly(acrylic acid) (PAA) and poly(4‐vinyl pyridine) (P4VP) was obtained through hydrolysis of diblock copolymer of poly(tert‐butyl acrylate) (PtBA) and P4VP synthesized using atom transfer radical polymerization. Water‐soluble micelles with PAA core and P4VP corona were observed at low (acidic) pH, while micelles with P4VP core and PAA corona were formed at high (basic) pH. Two metalloporphyrins, zinc tetraphenylporphyrin (ZnTPP) and cobalt tetraphenylporphyrin (CoTPP), were used as model compounds to investigate the encapsulation of hydrophobic molecules by both types of micelles. UV–vis spectroscopic measurements indicate that micelles with P4VP core are able to entrap more ZnTPP and CoTPP as a result of the axial coordination between the transition metals and the pyridine groups. The study found that metalloporphyrins encapsulated by the micelles with PAA core could be released on pH increase, while those entrapped by the micelles with P4VP core could be released on pH decrease. This behavior originates from the two‐way pH change‐induced disruption of PAA‐b‐P4VP micelles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1734–1744, 2006     

Investigation of the use of density functionals in second‐ and third‐row transition metal dimer calculations

We explore the use of density functionals in calculating the equilibrium distances, dissociation energies, and harmonic vibrational frequencies of the homonuclear diatomics of the second‐row transition metals, platinum, and gold. The outermost s–d interconfigurational energies (ICEs) and the outermost s and d ionization potentials (IPs) were also calculated for the second‐ and third‐row transition metal atoms. Compared with the first‐row transition metal dimer calculations (J Chem Phys 2000, 112, 545–553), the binding energies calculated using the combination of the Becke 1988 exchange and the one‐parameter progressive correlation (BOP) functional and Becke's three‐parameter hybrid (B3LYP) functional are in better agreement with the experiment. However, the pure BOP functional still gives the deep and narrow dissociation potential wells for the electron configurations containing high‐angular‐momentum open‐shell orbitals. Analysis of the s–d ICEs and the s and d IPs suggests that the overestimation may be due to the insufficient long‐range interaction between the outermost s and d orbitals in the exchange functional. The hybrid B3LYP functional seems to partly solve this problem for many systems by the incorporation of the Hartree–Fock exchange integral. However, this still leads to an erroneous energy gap between the configurations of fairly different spin multiplicity, probably because of the unbalance of exchange and correlation contributions. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1995–2009, 2001     

Advances in square arrays through self‐assembly and directed self‐assembly of block copolymers

This review covers recent advances in developing square arrays in thin films using block copolymers. Theoretical and experimental results from self‐assembly of block copolymers in bulk and thin films, directed self‐assembly of block copolymers confined in small wells, on substrates with arrays of posts, and on chemically nanopatterned substrates, as well as applications as nanolithography are reviewed. Some future work and hypothesis are discussed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Exploring the relevance of thiophene rings as bridge unit in acceptor‐bridge‐donor dyes on self‐aggregation and performance in DSSCs

The possibility of dye charge recombination in DSSCs remains a challenge for the field. This consists of: (a) back‐transfer from the TiO₂ to the oxidized dye and (b) intermolecular electron transfer between dyes. The latter is attributed to dye aggregation due to dimeric conformations. This leads to poor electron injection which decreases the photocurrent conversion efficiency. Most organic sensitizers are characterized by an Acceptor‐Bridge‐Donor ( A ‐Bridge‐ D ) arrangement that is commonly employed to provide charge separation and, therefore, lowering the unwanted back‐transfer. Here, we address the intermolecular electron transfer by studying the dimerization and photovoltaic performance of a group of A ‐Bridge‐ D structured dyes. Specifically, eight famous sulfur containing π‐bridges were analyzed ( A and D remained fixed). Through quantum mechanical and molecular dynamics approaches, it was found that the formation of weakly stabilized dimers is allowed. The dyes with covalently bonded and fused thiophene rings as Bridges, 6d and 7d as well as 8d with a fluorene, would present high aggregation and, therefore, high probability of recombination processes. Conversely, using TiO₂ cluster and surface models, delineated the shortest bridges to improve the adsorption energy and the stability of the system. Finally, the elongation of the bridge up to 2 and 3 units and their photovoltaic parameters were studied. These results showed that all the sensitizers are able to provide similar photocurrent outcomes, regardless of whether the bridge is elongated. © 2017 Wiley Periodicals, Inc.     

Crystallographic study of self‐organization in the solid state including quasi‐aromatic pseudo‐ring stacking interactions in 1‐benzoyl‐3‐(3,4‐dimethoxyphenyl)thiourea and 1‐benzoyl‐3‐(2‐hydroxypropyl)thiourea

1‐Benzoylthioureas contain both carbonyl and thiocarbonyl functional groups and are of interest for their biological activity, metal coordination ability and involvement in hydrogen‐bond formation. Two novel 1‐benzoylthiourea derivatives, namely 1‐benzoyl‐3‐(3,4‐dimethoxyphenyl)thiourea, C₁₆H₁₆N₂O₃S, (I), and 1‐benzoyl‐3‐(2‐hydroxypropyl)thiourea, C₁₁H₁₄N₂O₂S, (II), have been synthesized and characterized. Compound (I) crystallizes in the space group P , while (II) crystallizes in the space group P 2₁/c . In both structures, intramolecular N—H…O hydrogen bonding is present. The resulting six‐membered pseudo‐rings are quasi‐aromatic and, in each case, interact with phenyl rings via stacking‐type interactions. C—H…O, C—H…S and C—H…π interactions are also present. In (I), there is one molecule in the asymmetric unit. Pairs of molecules are connected via two intermolecular N—H…S hydrogen bonds, forming centrosymmetric dimers. In (II), there are two symmetry‐independent molecules that differ mainly in the relative orientations of the phenyl rings with respect to the thiourea cores. Additional strong hydrogen‐bond donor and acceptor –OH groups participate in the formation of intermolecular N—H…O and O—H…S hydrogen bonds that join molecules into chains extending in the [001] direction.