Synthesis and Crystal Structure of [Pb(trz)(tfpb)(H2O)]: a Lead(II) Complex Containing 2,4,6‐Tris(2‐pyridyl)‐1,3,5‐triazine and 4,4,4‐Trifluoro‐1‐phenyl‐1,3‐butandionate

[Pb(trz)(tfpb)(H₂O)] ( 1 ) (trz and tfpb are the abbreviations of 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine and 4,4,4‐trifluoro‐1‐phenyl‐1,3‐butandionate, respectively) have been synthesized and characterized by elemental analysis and IR, ¹H NMR, spectroscopy. The single‐crystal structure of 1 shows the coordination number of the Pb²⁺ ions is eight with three N‐donor atoms from a “trz” ligand and four O‐donors from the dionate ligand and one molecule of water. The supramolecular features in this complex are guided by lone pair activity and control of strong hydrogen bonds, weak directional intermolecular interactions and aromatic π‐π stacking interactions.     

NMR analysis of 6‐(2′,3′‐dihydro‐1′H‐inden‐1′‐yl)‐1H‐indene

¹H, ¹³C and two‐dimensional NMR analyses were applied to determine the NMR parameters of 6‐(2′,3′‐dihydro‐1′H‐inden‐1′‐yl)‐1H‐indene. The measurements were accomplished with 0.5 mg of the substance, this quantity being sufficient to determine the chemical shifts of all the H and C atoms, and also the appropriate coupling constants and to give the complete NMR resonance assignments of the molecule. The predicted patterns of the four different H atoms of the methylene groups of the indane structural element coincided completely with the complex patterns in the NMR spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Conformational Re‐engineering of Porphyrins as Receptors with Switchable N−H⋅⋅⋅X‐Type Binding Modes

The selectivity and functional variability of porphyrin cofactors are typically based on substrate binding of metalloporphyrins wherein the pyrrole nitrogen units only serve to chelate the metal ions. Yet, using the porphyrin inner core system for other functions is possible through conformational engineering. As a first step towards porphyrin “enzyme‐like” active centers, a structural and spectroscopic study of substrate binding to the inner core porphyrin system shows that a highly saddle‐distorted porphyrin with peripheral amino receptor groups ( 1 , 2,3,7,8,12,13,17,18‐octaethyl‐5,10,15,20‐tetrakis(2‐aminophenyl)porphyrin) coordinates analytes in a switchable manner dependent on the acidity of the solution. The supramolecular ensemble exhibits exceptionally high affinity to and selectivity for the pyrophosphate anion (2.26±0.021)×10⁹ m ^?1. ¹H NMR spectroscopic studies provided insight into the likely mode of binding and the characterization of atropisomers, all four of which were also studied by X‐ray crystallography.     

Synthesis of a Hemispherical Geodesic Phenine Framework by a Polygon Assembling Strategy

A synthetic strategy to construct large geodesic structures of phenine (1,3,5‐trisubstituted benzene) was devised. In this strategy, five pentagons were assembled on an omphalos pentagon, and bridging peripheral pentagons furnished five additional hexagons. Thirty phenine units were synthetically assembled to afford a large C₂₂₀H₁₈₀ molecule with a phenine framework isoreticular to a hemispherical, bisected segment of C₆₀. Although a hemispherical structure of the phenine framework was suggested by solution‐phase NMR spectra, crystallographic analysis revealed an oval‐like deformation of the molecular shape. In‐depth structural analyses, including theoretical calculations, showed that structural fluctuations observed as variations in the biaryl torsion angles allowed structural deformations and, at the same time, that the dynamic fluctuations resulted in the spectroscopic observation of a hemisphere as a time‐averaged structure.     

An efficient synthetic route to well‐defined theta‐shaped copolymers

A series of well‐defined θ‐shaped copolymers composed of polystyrene (PS) and poly(ε‐caprolactone) (PCL) with controlled molecular weight and narrow molecular weight distribution have been successfully synthesized without any purification procedure by the combination of atom transfer radical polymerization (ATRP), ring‐opening polymerization (ROP), and the “click” chemistry. The synthetic process involves two steps: (1) synthesis of AB₂ miktoarm star copolymers, which contain one PCL chain terminated with two acetylene groups and two PS chains with two azido groups at their one end, (α,α′‐diacetylene‐PCL) (ω‐azido‐PS)₂, by ROP, ATRP, and the terminal group transformation; (2) intramolecular cyclization of AB₂ miktoarm star copolymers to produce well‐defined pure θ‐shaped copolymers using “click” chemistry under high dilution. The ¹H NMR, FTIR, and gel permeation chromatography techniques were applied to characterize the chemical structures of the resultant intermediates and the target polymers. Their thermal behavior was investigated by DSC. The mobility decrease of PCL chain across PS ring in the theta‐shaped copolymers restricts the crystallization ability of PCL segment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2620–2630, 2009     

Synthesis and characterization of well‐defined polystyrene and poly(ε‐caprolactone) hetero eight‐shaped copolymers

Well‐defined hetero eight‐shaped copolymers composed of polystyrene (PS) and poly(ε‐caprolactone) (PCL) with controlled molecular weight and narrow molecular weight distribution were successfully synthesized by the combination of ring‐opening polymerization, ATRP, and “click” reaction. The synthetic procedure involves three steps: (1) preparation of a tetrafunctional PS and PCL star copolymer with two PS and two PCL arms using the tetrafunctional initiator bearing two hydroxyl groups and two bromo groups; (2) synthesis of tetrafunctional star copolymer, (α‐acetylene‐PCL)₂(ω‐azido‐PS)₂, by the transition of terminal hydroxyl and bromo groups to acetylene and azido groups through the reaction with 4‐propargyloxybutanedioyl chloride and NaN₃ respectively; (3) intramolecular cyclization reaction to produce the hetero eight‐shaped copolymers using “click” chemistry under high dilution. The ¹H NMR, FTIR, and gel permeation chromatography techniques were applied to characterize the chemical structures of the resulted intermediates and the target polymers. Their thermal behavior was investigated by DSC, and their crystallization behaviors of PCL were studied by polarized optical microscopy. The decrease in chain mobility of the eight‐shaped copolymers restricts the crystallization of PCL and the crystallization rate of PCL is slower in comparison with their corresponding star precursors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6496–6508, 2008     

Stereochemical analysis of the 3α‐ and 3β‐hydroxy metabolites of tibolone through NMR and quantum‐chemical investigations. An experimental test of GIAO calculations

The configuration at C‐3 of the 3α‐ and 3β‐hydroxy metabolites of tibolone was studied by extensive application of one‐ and two‐dimensional ¹H and ¹³C NMR spectroscopy combined with molecular modeling performed at the B3LYP/6–31G(d) level. Using HF and DFT GIAO methods, shielding tensors of the two molecules were computed; comparison of the calculated NMR chemical shifts with the experimental values revealed that the density functional methods produced the best results for assigning proton and carbon resonances. Although steroids are relatively large molecules, the present approach appears accurate enough to allow the determination of relative configurations by using calculated ¹³C resonances; the chemical shift of pairs of geminal α/β hydrogen atoms can also be established by using calculated ¹H resonances. Copyright © 2002 John Wiley & Sons, Ltd.     

Hydrogen bonding in polyamino‐polyalcohols: a monohydrated cocrystal of 1,3‐diamino‐5‐azaniumyl‐1,3,5‐trideoxy‐cis‐inositol iodide and 1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol

In the title monohydrated cocrystal, namely 1,3‐diamino‐5‐azaniumyl‐1,3,5‐trideoxy‐cis‐inositol iodide–1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol–water (1/1/1), C₆H₁₆N₃O₃⁺·I⁻·C₆H₁₅N₃O₃·H₂O, the neutral 1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol (taci) molecule and the monoprotonated 1,3‐diamino‐5‐azaniumyl‐1,3,5‐trideoxy‐cis‐inositol cation (Htaci⁺) both adopt a chair conformation, with the three O atoms in axial and the three N atoms in equatorial positions. The cation, but not the neutral taci unit, exhibits intramolecular O—H...O hydrogen bonding. The entire structure is stabilized by a complex three‐dimensional network of intermolecular hydrogen bonds. The neutral taci entities and the Htaci⁺ cations are each aligned into chains along [001]. In these chains, two O—H...N interactions generate a ten‐membered ring as the predominant structural motif. The rings consist of vicinal 2‐amino‐1‐hydroxyethylene units of neighbouring molecules, which are paired via centres of inversion. The chains are interconnected into undulating layers parallel to the ac plane, and the layers are further held together by O—H...N hydrogen bonds and additional interactions with the iodide counter‐anions and solvent water molecules.     

Spectroscopic,Thermal and Structural Studies of Aza‐aromatic Base Adducts of Cadmium Furoyltrifluoroacetonate

Three aza‐aromatic base adducts of cadmium(II) furoyltrifluoroacetonate, [Cd(4,4′‐bpy)(ftfa)₂]_n ( 1 ), [Cd(2,2′‐bpy)(ftfa)₂] ( 2 ) and [Cd(dmp)(ftfa)₂] ( 3 ) (“4,4′‐bpy”, “2,2′‐bpy”, “dmp” and “ftfa” are the abbreviations of 4,4′‐bipyridine, 2,2′‐bipyridine, 2,9‐dimethyl‐1,10‐phenanthroline and furoyltrifluoroacetonate, respectively) have been synthesized and characterized by elemental analysis and IR, ¹H NMR and ¹³C NMR spectroscopy and studied by thermal as well as X‐ray crystallography. The single‐crystal structure of these complexes shows that the coordination number of the Cd^II ions are six with two N‐donor atoms from aza‐aromatic base ligands and four O‐donors from two the furoyltrifluoroacetonates. The supramolecular features in these complexes are guided/controlled by weak directional intermolecular interactions.     

Quadruple‐Resonance Magic‐Angle Spinning NMR Spectroscopy of Deuterated Solid Proteins

¹H‐detected magic‐angle spinning NMR experiments facilitate structural biology of solid proteins, which requires using deuterated proteins. However, often amide protons cannot be back‐exchanged sufficiently, because of a possible lack of solvent exposure. For such systems, using ²H excitation instead of ¹H excitation can be beneficial because of the larger abundance and shorter longitudinal relaxation time, T₁, of deuterium. A new structure determination approach, “quadruple‐resonance NMR spectroscopy”, is presented which relies on an efficient ²H‐excitation and ²H‐¹³C cross‐polarization (CP) step, combined with ¹H detection. We show that by using ²H‐excited experiments better sensitivity is possible on an SH3 sample recrystallized from 30 % H₂O. For a membrane protein, the ABC transporter ArtMP in native lipid bilayers, different sets of signals can be observed from different initial polarization pathways, which can be evaluated further to extract structural properties.     

Tadpole‐shaped amphiphilic copolymers prepared via RAFT polymerization and click reaction

The tadpole‐shaped amphiphilic copolymers with cyclic polystyrene as the head and a linear poly(N‐isopropylacrylamide) as the tail have been successfully synthesized by combination of reversible addition‐fragmentation chain transfer (RAFT) polymerization and “click” reaction. The synthesis involves two main steps: (1) preparation of a linear acetylene‐terminated PNIPAAM‐b‐PS with a side azido group anchored at the junction between two blocks; (2) intramolecular cyclization reaction to produce the cyclic PS block using “click” chemistry under high dilution. The structures, molecular weights, and molecular weight distributions of the resulted intermediates and the target polymers were characterized by their ¹H NMR, FTIR, and gel permeation chromatography. The difference of surface property between tadpole‐shaped polymer and its linear precursor was observed, and the water contact angles on the former surface are larger than that of the latter surface. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2390–2401, 2008     

Synthesis of ABCD 4‐Miktoarm star‐shaped quarterpolymers by combination of the “click” chemistry with multiple polymerization mechanism

Well‐defined ABCD 4‐Miktoarm star‐shaped quarterpolymers of [poly(styrene)‐poly(tert‐butyl acrylate)‐poly(ethylene oxide)‐poly(isoprene)] [star(PS‐PtBA‐PEO‐PI)] were successfully synthesized by the combination of the “click” chemistry and multiple polymerization mechanism. First, the poly(styryl)lithium (PS^?Li⁺) and the poly(isoprene)lithium (PI^?Li⁺) were capped by ethoxyethyl glycidyl ether (EEGE) to form the PS and PI with both an active ω‐hydroxyl group and an ω′‐ethoxyethyl‐protected hydroxyl group, respectively. After these two hydroxyl groups were selectively modified to propargyl and 2‐bromoisobutyryl group for PS, the resulted PS was used as macroinitiator for ATRP of tBA monomer and the diblock copolymer PS‐b‐PtBA with a propargyl group at the junction point was achieved. Then, using the functionalized PI as macroinitiator for ROP of EO monomer and bromoethane as blocking agent, the diblock copolymer PI‐b‐PEO with a protected hydroxyl group at the conjunction point was synthesized. After the hydrolysis, the recovered hydroxyl group of PI‐b‐PEO was modified to bromoacetyl and then azide group successively. Finally, the “click” chemistry between them was proceeded smoothly. The obtained star‐shaped quarterpolymers and intermediates were characterized by ¹H NMR, FT‐IR, and SEC in detail. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2154–2166, 2008     

A Solution‐Processable Donor–Acceptor Compound Containing Boron(III) Centers for Small‐Molecule‐Based High‐Performance Ternary Electronic Memory Devices

A novel small‐molecule boron(III)‐containing donor–acceptor compound has been synthesized and employed in the fabrication of solution‐processable electronic resistive memory devices. High ternary memory performances with low turn‐on (V_Th1=2.0 V) and distinct threshold voltages (V_Th2=3.3 V), small reading bias (1.0 V), and long retention time (>10⁴ seconds) with a large ON/OFF ratio of each state (current ratio of “OFF”, “ON1”, and “ON2”=1:10³:10⁶) have been demonstrated, suggestive of its potential application in high‐density data storage. The present design strategy provides new insight in the future design of memory devices with multi‐level transition states.     

Synthesis of a novel graft copolymer with hyperbranched poly(glycerol) as core and “Y”‐shaped polystyrene‐b‐poly(ethylene oxide)2 as side chains

The graft copolymers composed of “Y”‐shaped polystyrene‐b‐poly(ethylene oxide)₂ (PS‐b‐PEO₂) as side chains and hyperbranched poly(glycerol) (HPG) as core were synthesized by a combination of “click” chemistry and atom transfer radical polymerization (ATRP) via “graft from” and “graft onto” strategies. Firstly, macroinitiators HPG‐Br were obtained by esterification of hydroxyl groups on HPG with bromoisobutyryl bromide, and then by “graft from” strategy, graft copolymers HPG‐g‐(PS‐Br) were synthesized by ATRP of St and further HPG‐g‐(PS‐N₃) were prepared by azidation with NaN₃. Then, the precursors (Bz‐PEO)₂‐alkyne with a single alkyne group at the junction point and an inert benzyl group at each end was synthesized by sequentially ring‐opening polymerization (ROP) of EO using 3‐[(1‐ethoxyethyl)‐ethoxyethyl]‐1,2‐propanediol (EEPD) and diphenylmethylpotassium (DPMK) as coinitiator, termination of living polymeric species by benzyl bromide, recovery of protected hydroxyl groups by HCl and modification by propargyl bromide. Finally, the “click” chemistry was conducted between HPG‐g‐(PS‐N₃) and (Bz‐PEO)₂‐alkyne in the presence of N,N,N′,N″,N”‐pentamethyl diethylenetriamine (PMDETA)/CuBr system by “graft onto” strategy, and the graft copolymers were characterized by SEC, ¹H NMR and FTIR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A Dipleiadiene‐Embedded Aromatic Saddle Consisting of 86 Carbon Atoms

This study presents a new type of negatively curved nanographene (C₈₆H₃₂) that contains an unprecedented pattern of heptagons. A tert‐butylated derivative of C₈₆H₃₂ was successfully synthesized using tetrabenzodipleiadiene as a key building block. This synthesis involved a ring expansion reaction as a key step to form the seven‐membered rings in the framework of tetrabenzodipleiadiene. The single‐crystal structure reveals a saddle‐shaped molecule with a highly bent naphthalene moiety at the center of the polycyclic backbone. As found from the DFT calculations, this aromatic saddle is flexible at room temperature and has a saddle‐shaped geometry as the dominant conformation. The DFT calculations along with experimental results show that the attachment of t‐butyl groups to the central tetrabenzodipleiadiene moiety of nanographene C₈₆H₃₂ can stabilize the saddle conformation and make this nanographene less flexible.     

Deuteration of Water Enables Self‐Organization of Phospholipid‐Based Reverse Micelles

Phospholipid‐based reverse micelles are composed of branched cylinders. Their branching points are known to attract themselves and to slide along branches. The rate of this sliding is governed by the lifetime of H(D)‐bonded water bridges between phospholipid molecules. This lifetime is increased when the water is deuterated. On condition that the water contains at least 40 D atoms %, water/dipalmitoylphosphatidylcholine (DPPC)/deuterated pyridine reverse micelles with the composition 1.1:1:250 (v/v) have been shown to self‐organize into a liquid crystal in the 310–316 K temperature range. The mechanism of this self‐organization is unraveled by following the FTIR and ¹H NMR spectra of more concentrated micelles upon heating. During the preparation of micelles, pyridine‐(D⁺)H⁺ ions are formed. They give rise to hydron transfers, under the influence of the DPPC electric charges, evidenced by two broad FTIR absorptions above (BB1) and below (BB2) the ν(C? O) stretch. These hydron transfers occur along strong (D⁺)H⁺ bonds of pyridinium ions with pyridine (BB1) and DPPC C?O groups (BB2). The proton transfers at the interface of micelles, relayed in the continuous pyridine medium, create a tenuous link between separated micelles, thus facilitating their organization. Upon heating, DPPC heads shrink and DPPC chains expand to make wedge‐shaped DPPC molecules. The micelles then change in shape: cylinders constrict and enclosed water drifts towards branching points, which swell. Branching points of neighboring micelles come into contact. Due to the deuteration of water these contacts are prolonged and H bonds are formed between DPPC molecules located in each branching point. Upon storage at 39 °C, these branching points fuse. The lateral diffusion of DPPC molecules becomes free, as evidenced by a narrowing of all ¹H NMR resonances. Upon further heating, reorganization into a liquid crystal occurs.     

Complexation‐Induced Supramolecular Assembly Drives Metal‐Ion Extraction

Combining experiment with theory reveals the role of self‐assembly and complexation in metal‐ion transfer through the water–oil interface. The coordinating metal salt Eu(NO₃)₃ was extracted from water into oil by a lipophilic neutral amphiphile. Molecular dynamics simulations were coupled to experimental spectroscopic and X‐ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the organic phase combine with long‐range interactions to produce spontaneous changes in the solvent microstructure. Extraction of the Eu³⁺–3(NO₃^?) ion pairs involves incorporation of the “hard” metal complex into the core of “soft” aggregates. This seeds the formation of reverse micelles that draw the water and “free” amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod‐shaped polynuclear Eu^III‐containing aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, containing high densities of O‐donor ligands and anions, provide improved Eu^III solvation environments that help drive interfacial transfer, as is reflected by the increasing Eu^III partitioning ratios (oil/aqueous) despite the organic phase approaching saturation. For the first time, this multiscale approach links metal‐ion coordination with nanoscale structure to reveal the free‐energy balance that drives the phase transfer of neutral metal salts.     

Air‐stable copper derivatives as efficient catalysts for controlled lactide polymerization: Facile synthesis and characterization of well‐defined benzotriazole phenoxide copper complexes

Air‐stable copper catalysts supported by bis‐ BTP ligands ( BTP = N,O‐bidentate benzotriazole phenoxide) were synthesized and structurally characterized. The reactions of Cu(OAc)₂·H₂O with 2.0 molar equivalents of sterically bulky 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐bis(1‐methyl‐1‐phenylethyl)phenol ( ^CMe2PhBTP ‐H) and 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐di‐tert‐butylphenol ( ^t‐BuBTP ‐H) in refluxing ethanol solution afforded monomeric copper complexes [(^CMe2PhBTP)₂Cu] ( 1 ) and [(^t‐BuBTP)₂Cu] ( 2 ), respectively. The four‐coordinated copper analogue [(^TMClBTP)₂Cu] (3 ) resulted from treatment of 2‐tert‐butyl‐6‐(5‐chloro‐2H‐benzotriazol‐2‐yl)‐4‐methylphenol ( ^TMClBTP ‐H) as the ligand under the same synthetic method with ligand to metal precursor ratio of 2:1, but treatment of complex 3 in acetone gave five‐coordinated monomeric complex [(^TMClBTP)₂Cu(Me₂CO)] (4 ). X‐ray diffraction of single crystals indicates that Cu complex 4 assumes a distorted square pyramidal geometry, penta‐coordinated by two BTP ligands, and one Me₂CO molecule. Catalysis for lactide (LA) polymerization of BTP ‐containing Cu complexes in the presence of various alcohol initiators was investigated. Complex 3 initiated by 9‐anthracenemethanol catalyzes the ring‐opening polymerization effectively not only in a “living” fashion but also in an “immortal” manner, yielding polymers with the predictable molecular weights and narrow molecular weight distributions. Initiations from multifunctional alcohols were able to produce PLLAs with two‐arm linear and three‐arm star‐shaped molecular architectures. The controlled character of Cu complex 3 also enabled us to synthesize the PEG‐b‐PLLA copolymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3840–3849