Cu(II) and Ni(II)‐1,10‐phenanthroline‐ 5,6‐dione‐amino acid ternary complexes exhibiting pH‐sensitive redox properties

Syntheses, and electrochemical properties of two novel complexes, [Cu(phendio)(L ‐Phe)(H₂O)](ClO₄) ·H₂O (1) and [Ni(phendio)(Gly)(H₂O)](ClO₄)·H₂O (2) (where phendio = 1,10‐phenanthroline‐5,6‐dione, L ‐Phe = L ‐phenylalanine, Gly = glycine), are reported. Single‐crystal X‐ray diffraction results of (1) suggest that this complex structure belongs to the orthorhombic crystal system. The electrochemical properties of free phendio and these complexes in phosphate buffer solutions in a pH range between 2 and 9 have been investigated using cyclic voltammetry. The redox potential of these compounds is strongly dependent on the proton concentration in the range of ? 0.3–0.4 V vs SCE (saturated calomel reference electrode). Phendiol reacts by the reduction of the quinone species to the semiquinone anion followed by reduction to the fully reduced dianion. At pH lower than 4 and higher than 4, reduction of phendio proceeds via 2e^?/3H⁺ and 2e^?/2H⁺ processes. For complexes (1) and (2), being modulated by the coordinated amino acid, the reduction of the phendio ligand proceeds via 2e^?/2H⁺ and 2e^?/H⁺ processes, respectively. Copyright © 2006 John Wiley & Sons, Ltd.     

Ball‐Milling‐Induced Amorphization of Zeolitic Imidazolate Frameworks (ZIFs) for the Irreversible Trapping of Iodine

The I₂‐sorption and ‐retention properties of several existing zeolitic imidazolate frameworks (ZIF‐4, ‐8, ‐69) and a novel framework, ZIF‐mnIm ([Zn(mnIm)₂]; mnIm=4‐methyl‐5‐nitroimidazolate), have been characterised using microanalysis, thermogravimetric analysis and X‐ray diffraction. The topologically identical ZIF‐8 ([Zn(mIm)₂]; mIm=2‐methylimidazolate) and ZIF‐mnIm display similar sorption abilities, though strikingly different guest‐retention behaviour upon heating. We discover that this guest retention is greatly enhanced upon facile amorphisation by ball milling, particularly in the case of ZIF‐mnIm, for which I₂ loss is retarded by as much as 200 °C. It is anticipated that this general approach should be applicable to the wide range of available metal–organic framework‐type materials for the permanent storage of harmful guest species.     

Microporosity of a Guanidinium Organodisulfonate Hydrogen‐Bonded Framework

Guanidinium organosulfonates (GSs) are a large and well‐explored archetypal family of hydrogen‐bonded organic host frameworks that have, over the past 25 years, been regarded as nonporous. Reported here is the only example to date of a conventionally microporous GS host phase, namely guanidinium 1,4‐benzenedisulfonate ( p ‐G₂BDS ). p ‐G₂BDS is obtained from its acetone solvate, AcMe@ G₂BDS , by single‐crystal‐to‐single‐crystal (SC‐SC) desolvation, and exhibits a Type I low‐temperature/pressure N₂ sorption isotherm (SA_BET=408.7(2) m² g^?1, 77 K). SC‐SC sorption of N₂, CO₂, Xe, and AcMe by p ‐G₂BDS is explored under various conditions and X‐ray diffraction provides a measurement of the high‐pressure, room temperature Xe and CO₂ sorption isotherms. Though p ‐G₂BDS is formally metastable relative to the “collapsed”, nonporous polymorph, np ‐G₂BDS , a sample of p ‐G₂BDS survived for almost two decades under ambient conditions. np ‐G₂BDS reverts to zCO₂@ p ‐G₂BDS or yXe@ p ‐G₂BDS (y,z=variable) when pressure of CO₂ or Xe, respectively, is applied.     

The Propensity of α‐Aminoisobutyric Acid (=2‐Methylalanine; Aib) to Induce Helical Secondary Structure in an α‐Heptapeptide: A Computational Study

We present a molecular‐dynamics simulation study of an α‐heptapeptide containing an α‐aminoisobutyric acid (=2‐methylalanine; Aib) residue, Val¹‐Ala²‐Leu³‐Aib⁴‐Ile⁵‐Met⁶‐Phe⁷, and a quantum‐mechanical (QM) study of simplified models to investigate the propensity of the Aib residue to induce 3₁₀/α‐helical conformation. For comparison, we have also performed simulations of three analogues of the peptide with the Aib residue being replaced by L ‐Ala, D ‐Ala, and Gly, respectively, which provide information on the subtitution effect at C(α) (two Me groups for Aib, one for L ‐Ala and D ‐Ala, and zero for Gly). Our simulations suggest that, in MeOH, the heptapeptide hardly folds into canonical helical conformations, but appears to populate multiple conformations, i.e., C₇ and 3₁₀‐helical ones, which is in agreement with results from the QM calculations and NMR experiments. The populations of these conformations depend on the polarity of the solvent. Our study confirms that a short peptide, though with the presence of an Aib residue in the middle of the chain, does not have to fold to an α‐helical secondary structure. To generate a helical conformation for a linear peptide, several Aib residues should be present in the peptide, either sequentially or alternatively, to enhance the propensity of Aib‐containing peptides towards the helical conformation. A correction of a few of the published NMR data is reported.     

Guest‐Adaptable and Water‐Stable Peptide‐Based Porous Materials by Imidazolate Side Chain Control

The peptide‐based porous 3D framework, ZnCar, has been synthesized from Zn²⁺ and the natural dipeptide carnosine (β‐alanyl‐L ‐histidine). Unlike previous extended peptide networks, the imidazole side chain of the histidine residue is deprotonated to afford Zn–imidazolate chains, with bonding similar to the zeolitic imidazolate framework (ZIF) family of porous materials. ZnCar exhibits permanent microporosity with a surface area of 448 m² g^?1, and its pores are 1D channels with 5 Å openings and a characteristic chiral shape. This compound is chemically stable in organic solvents and water. Single‐crystal X‐ray diffraction (XRD) showed that the ZnCar framework adapts to MeOH and H₂O guests because of the torsional flexibility of the main His‐β‐Ala chain, while retaining the rigidity conferred by the Zn–imidazolate chains. The conformation adopted by carnosine is driven by the H bonds formed both to other dipeptides and to the guests, permitting the observed structural transformations.     

Improved Voltammetric Response of L‐Tyrosine on Multiwalled Carbon Nanotubes‐Ionic Liquid Composite Coated Glassy Electrodes in the Presence of Cupric Ion

L ‐Tyrosine can exhibit a small anodic peak on multiwalled carbon nanotubes (MWCNTs) coated glassy carbon electrodes (GCE). At pH 5.5 its peak potential is 0.70 V (vs. SCE). When an ionic liquid (i.e., 1‐octyl‐3‐methylimidazolium hexafluorophosphate, [omim][PF₆]) is introduced on the MWCNT coat, the peak becomes bigger. Furthermore, in the presence of Cu²⁺ ion the anodic peak of L ‐tyrosine increases further due to the formation of Cu²⁺‐L ‐tyrosine complex, while the peak potential keeps unchanged. Therefore, a sensitive voltammetry based on the oxidation of Cu²⁺‐L ‐tyrosine complex on MWCNTs‐[omim][PF₆] composite coated electrode is developed for L ‐tyrosine. Under the optimized conditions, the anodic peak current is linear to L ‐tyrosine concentration in the range of 1×10^?8–5×10^?6 M, and the detection limit is 8×10^?9 M. The modified electrode shows good reproducibility and stability. In addition, the voltammetric behavior of other amino acids is explored. It is found that among them tryptophan (Trp) and histidine (His) can also produce sensitive anodic peak under same experimental conditions, and their detection limits are 4×10^?9 M and 4×10^?6 M, respectively.     

Synthesis and ring‐opening (co)polymerization of L‐lysine N‐carboxyanhydrides containing labile side‐chain protective groups

This contribution describes the synthesis and ring‐opening (co)polymerization of several L ‐lysine N‐carboxyanhydrides (NCAs) that contain labile protective groups at the ?‐NH₂ position. Four of the following L ‐lysine NCAs were investigated: N^?‐trifluoroacetyl‐L ‐lysine N‐carboxyanhydride, N^?‐(tert‐butoxycarbonyl)‐L ‐lysine N‐carboxyanhydride, N^?‐(9‐fluorenylmethoxycarbonyl)‐L ‐lysine N‐carboxyanhydride, and N^?‐(6‐nitroveratryloxycarbonyl)‐L ‐lysine N‐carboxyanhydride. In contrast to the harsh conditions that are required for acidolysis of benzyl carbamate moieties, which are usually used to protect the ?‐NH₂ position of L ‐lysine during NCA polymerization, the protective groups of the L ‐lysine NCAs presented here can be removed under mildly acidic or basic conditions or by photolysis. As a consequence, these monomers may allow access to novel peptide hybrid materials that cannot be prepared from ?‐benzyloxycarbonyl‐L ‐lysine N‐carboxyanhydride (Z‐Lys NCA) because of side reactions that accompany the removal of the Z groups. By copolymerization of these L ‐lysine NCAs with labile protective groups, either with each other or with γ‐benzyl‐L ‐glutamate N‐carboxyanhydride or Z‐Lys NCA, orthogonally side‐chain‐protected copolypeptides with number‐average degrees of polymerization ≤20 were obtained. Such copolypeptides, which contain different side‐chain protective groups that can be removed independently, are interesting for the synthesis of complex polypeptide architectures or can be used as scaffolds for the preparation of synthetic antigens or protein mimetics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1167–1187, 2003     

One‐pot Chemoenzymatic Synthesis of Chiral 1,3‐Diols Using an Enantioselective Aldol Reaction with Chiral Zn2+ Complex Catalysts and Enzymatic Reduction Using Oxidoreductases with Cofactor Regeneration

We previously reported on enantioselective aldol reactions of acetone and some aldehydes catalyzed by chiral Zn²⁺ complexes of L ‐prolyl‐pendant [12]aneN₄ (L ‐ZnL¹) and L ‐valyl‐pendant [12]aneN₄ (L ‐ZnL²) in aqueous solution. Here, we report on the one‐pot chemoenzymatic synthesis of chiral 1,3‐diols in an aqueous solvent system at room temperature by a combination of enantioselective aldol reactions catalyzed by Zn²⁺ complexes of L ‐ and D ‐phenylalanyl‐pendant [12]aneN₄ (L ‐ZnL³ and D ‐ZnL³) and the successive enantioselective reduction of the aldol products using oxidoreductases with the regeneration of the NADH (reduced form of nicotinamine adenine dinucleotide) cofactor. The findings indicate that all four stereoisomers of 1,3‐diols can be produced by appropriate selection of a chiral Zn²⁺‐complex and an oxidoreductase commercially available from the “Chiralscreen OH” kit.     

Synthesis of star‐shaped poly(D,L‐lactic acid‐alt‐glycolic acid)‐b‐poly(L‐lactic acid) with the poly(D,L‐lactic acid‐alt‐glycolic acid) macroinitiator and stannous octoate catalyst

Two types of three‐arm and four‐arm, star‐shaped poly(D,L ‐lactic acid‐alt‐glycolic acid)‐b‐poly(L ‐lactic acid) (D,L ‐PLGA50‐b‐PLLA) were successfully synthesized via the sequential ring‐opening polymerization of D,L ‐3‐methylglycolide (MG) and L ‐lactide (L ‐LA) with a multifunctional initiator, such as trimethylolpropane and pentaerythritol, and stannous octoate (SnOct₂) as a catalyst. Star‐shaped, hydroxy‐terminated poly(D,L ‐lactic acid‐alt‐glycolic acid) (D,L ‐PLGA50) obtained from the polymerization of MG was used as a macroinitiator to initiate the block polymerization of L ‐LA with the SnOct₂ catalyst in bulk at 130 °C. For the polymerization of L ‐LA with the three‐arm, star‐shaped D,L ‐PLGA50 macroinitiator (number‐average molecular weight = 6800) and the SnOct₂ catalyst, the molecular weight of the resulting D,L ‐PLGA50‐b‐PLLA polymer linearly increased from 12,600 to 27,400 with the increasing molar ratio (1:1 to 3:1) of L ‐LA to MG, and the molecular weight distribution was rather narrow (weight‐average molecular weight/number‐average molecular weight = 1.09–1.15). The ¹H NMR spectrum of the D,L ‐PLGA50‐b‐PLLA block copolymer showed that the molecular weight and unit composition of the block copolymer were controlled by the molar ratio of L ‐LA to the macroinitiator. The ¹³C NMR spectrum of the block copolymer clearly showed its diblock structures, that is, D,L ‐PLGA50 as the first block and poly(L ‐lactic acid) as the second block. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 409–415, 2002     

Two Heterometallic–Organic Frameworks Composed of Iron(III)‐Salen‐Based Ligands and d10 Metals: Gas Sorption and Visible‐Light Photocatalytic Degradation of 2‐Chlorophenol

Two examples of heterometallic–organic frameworks (HMOFs) composed of dicarboxyl‐functionalized Fe^III‐salen complexes and d¹⁰ metals (Zn, Cd), [Zn₂(Fe‐L)₂(μ₂‐O)(H₂O)₂] ? 4 DMF ? 4 H₂O ( 1 ) and [Cd₂(Fe‐L)₂(μ₂‐O)(H₂O)₂] ? 2 DMF ? H₂O ( 2 ) (H₄L=1,2‐cyclohexanediamino‐N,N′‐bis(3‐methyl‐5‐carboxysalicylidene), have been synthesized and structurally characterized. In 1 and 2 , each square‐pyramidal Fe^III atom is embedded in the [N₂O₂] pocket of an L^4? anion, and these units are further bridged by a μ₂‐O anion to give an (Fe‐L)₂(μ₂‐O) dimer. The two carboxylate groups of each L^4? anion bridge Zn^II or Cd^II atoms to afford a 3D porous HMOF. The gas sorption and magnetic properties of 1 and 2 have been studied. Remarkably, 1 and 2 show activity for the photocatalytic degradation of 2‐chlorophenol (2‐CP) under visible‐light irradiation, which, to the best of our knowledge, is the first time that this has been observed for Fe^III‐salen‐based HMOFs.     

Redox Sorption and Recovery of Silver Ions as Silver Nanocrystals on Poly(aniline‐co‐5‐sulfo‐2‐anisidine) Nanosorbents

Poly[aniline(AN)‐co‐5‐sulfo‐2‐anisidine(SA)] nanograins with rough and porous structure demonstrate ultrastrong adsorption and highly efficient recovery of silver ions. The effects of five key factors—AN/SA ratio, Ag^I concentration, sorption time, ultrasonic treatment, and coexisting ions—on Ag^I adsorbability were optimized, and AN/SA (50/50) copolymer nanograins were found to exhibit much stronger Ag^I adsorption than polyaniline and all other reported sorbents. The maximal Ag^I sorption capacity of up to 2034 mg g^?1 (18.86 mmol g^?1) is the highest thus far and also much higher than the maximal Hg‐ion sorption capacity (10.28 mmol g^?1). Especially at ≤2 mM Ag^I, the nanosorbents exhibit ≥99.98 % adsorptivity, and thus achieve almost complete Ag^I sorption. The sorption fits the Langmuir isotherm well and follows pseudo‐second‐order kinetics. Studies by IR, UV/Vis, X‐ray diffraction, polarizing microscopy, centrifugation, thermogravimetry, and conductivity techniques showed that Ag^I sorption occurs by a redox mechanism mainly involving reduction of Ag^I to separable silver nanocrystals, chelation between Ag^I and ? NH? /? N?/? NH₂/ ? SO₃H/? OCH₃, and ion exchange between Ag^I and H⁺ on ? SO₃^?H⁺. Competitive sorption of Ag^I with coexisting Hg, Pb, Cu, Fe, Al, K, and Na ions was systematically investigated. In particular, the copolymer nanoparticles bearing many functional groups on their rough and porous surface can be directly used to recover and separate precious silver nanocrystals from practical Ag^I wastewaters containing Fe, Al, K, and Na ions from Kodak Studio. The nanograins have great application potential in the noble metals industry, resource reuse, wastewater treatment, and functional hybrid nanocomposites.     

Controlled Gas Exfoliation of Boron Nitride into Few‐Layered Nanosheets

The controlled exfoliation of hexagonal boron nitride (h‐BN) into single‐ or few‐layered nanosheets remains a grand challenge and becomes the bottleneck to essential studies and applications of h‐BN. Here, we present an efficient strategy for the scalable synthesis of few‐layered h‐BN nanosheets (BNNS) using a novel gas exfoliation of bulk h‐BN in liquid N₂ (L‐N₂). The essence of this strategy lies in the combination of a high temperature triggered expansion of bulk h‐BN and the cryogenic L ‐N₂ gasification to exfoliate the h‐BN. The produced BNNS after ten cycles (BNNS‐10) consisted primarily of fewer than five atomic layers with a high mass yield of 16–20 %. N₂ sorption and desorption isotherms show that the BNNS‐10 exhibited a much higher specific surface area of 278 m² g^?1 than that of bulk BN (10 m² g^?1). Through the investigation of the exfoliated intermediates combined with a theoretical calculation, we found that the huge temperature variation initiates the expansion and curling of the bulk h‐BN. Subseqently, the L ‐N₂ penetrates into the interlayers of h‐BN along the curling edge, followed by an immediate drastic gasification of L ‐N₂, further peeling off h‐BN. This novel gas exfoliation of high surface area BNNS not only opens up potential opportunities for wide applications, but also can be extended to produce other layered materials in high yields.     

Asymmetric Aldol Reactions between Acetone and Benzaldehydes Catalyzed by Chiral Zn2+ Complexes of Aminoacyl 1,4,7,10‐Tetraazacyclododecane: Fine‐Tuning of the Amino‐Acid Side Chains and a Revised Reaction Mechanism

We previously reported that chiral Zn²⁺ complexes that were designed to mimic the actions of class‐I and class‐II aldolases catalyzed the enantioselective aldol reactions of acetone and its analogues thereof with benzaldehyde derivatives. Herein, we report the synthesis of new chiral Zn²⁺ complexes that contain Zn²⁺? tetraazacyclododecane (Zn²⁺? [12]aneN₄) moieties and amino acids that contain aliphatic, aromatic, anionic, cationic, and dipeptide side chains. The chemical and optical yields of the aldol reaction were improved (up to 96 % ee) by using ZnL complexes of L ‐decanylglycyl‐pendant [12]aneN₄ (L ‐ZnL⁷), L ‐naphthylalanyl‐pendant [12]aneN₄ (L ‐ZnL¹⁰), L ‐biphenylalanyl‐pendant [12]aneN₄ (L ‐ZnL¹¹), and L ‐phenylethylglycyl‐pendant [12]aneN₄ ligands (L ‐ZnL¹²). UV/Vis and circular dichroism (CD) titrations of acetylacetone (acac) with ZnL complexes confirmed that a ZnL? (acac)^? complex was exclusively formed and not the enaminone of ZnL and acac, as we had previously proposed. Moreover, the results of stopped‐flow experiments indicated that the complexation of (acac)^? with ZnL was complete within milliseconds, whereas the formation of an enaminone required several hours. X‐ray crystal‐structure analysis of L ‐ZnL¹⁰ and the ZnL complex of L ‐diphenylalanyl‐pendant [12]aneN₄ (L ‐ZnL¹³) shows that the NH₂ groups of the amino‐acid side chains of these ligands are coordinated to the Zn²⁺ center as the fourth coordination site, in addition to three nitrogen atoms of the [12]aneN₄ rings. The reaction mechanism of these aldol reactions is discussed and some corrections are made to our previous mechanistic hypothesis.     

A New Route for Preparation of 5‐Deoxy‐5‐(hydroxyphosphinyl)‐ D‐mannopyranose and ‐L‐gulopyranose Derivatives

Starting from methyl 2,3‐O‐isopropylidene‐α‐D ‐mannofuranoside ( 5 ), methyl 6‐O‐benzyl‐2,3‐O‐isopropylidene‐α‐D ‐lyxo‐hexofuranosid‐5‐ulose ( 12 ) was prepared in three steps. The addition reaction of dimethyl phosphonate to 12 , followed by deoxygenation of 5‐OH group, provided the 5‐deoxy‐5‐dimethoxyphosphinyl‐α‐D ‐mannofuranoside derivative 15a and the β‐L ‐gulofuranoside isomer 15b . Reduction of 15a and 15b with sodium dihydrobis(2‐methoxyethoxy)aluminate, followed by the action of HCl and then H₂O₂, afforded the D ‐mannopyranose ( 17 ) and L ‐gulopyranose analog 21 , each having a phosphinyl group in the hemiacetal ring. These were converted to the corresponding 1,2,3,4,6‐penta‐O‐acetyl‐5‐methoxyphosphinyl derivatives 19 and 23 , respectively, structures and conformations (⁴C₁ or ¹C₄, resp.) of which were established by ¹H‐NMR spectroscopy.     

Controlled surface‐initiated ring‐opening polymerization of L‐lactide from risedronate‐anchored hydroxyapatite nanocrystals: Novel synthesis of biodegradable hydroxyapatite/poly(L‐lactide) nanocomposites

Risedronate‐anchored hydroxyapatite (HA‐RIS) nanocrystals were prepared with 4.1 wt % RIS and used for controlled surface‐initiated ring‐opening polymerization (ROP) of L ‐lactide (L ‐LA). The strong adsorption of RIS to HA surface not only led to enhanced dispersion of HA nanocrystals in water as well as in organic solvents but also provided alkanol groups as active initiating species for ROP of L ‐LA. HA‐RIS was characterized by thermogravimetric analysis, dynamic light scattering, ¹H NMR, Fourier transform infrared spectrometer, and X‐ray diffraction. The graft polymerization of L ‐LA onto HA‐RIS took place smoothly in the presence of stannous octoate in toluene at 120 °C, resulting in HA/poly(L ‐LA) nanocomposites with high yields of 85–90% and high poly(L ‐LA) contents of up to 97.5 wt %. Notably, differential scanning calorimetry measurements revealed that the poly(L ‐LA) in HA/poly(L ‐LA) nanocomposites exhibited considerably higher melting temperatures (T_m = 173.3?178.1 °C) and higher degrees of crystallinity (X_c = 41.0?43.1%) as compared to poly(L ‐LA) homopolymer (T_m = 168.5 °C, X_c =25.7%). In addition, our initial results showed that these HA/poly(L ‐LA) nanocomposites could readily be electrospun into porous matrices. This study presented a novel and controlled synthetic strategy to HA/RIS/poly(L ‐LA) nanocomposites that are promising for orthopedic applications as well as for bone tissue engineering. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

The first 3′:5′‐cyclic nucleotide–amino acid complex: l‐His–cIMP

In the crystal structure of the l ‐His–cIMP complex, i.e.l ‐histidinium inosine 3′:5′‐cyclic phosphate [systematic name: 5‐(2‐amino‐2‐carboxyethyl)‐1H‐imidazol‐3‐ium 7‐hydroxy‐2‐oxo‐6‐(6‐oxo‐6,9‐dihydro‐1H‐purin‐9‐yl)‐4a,6,7,7a‐tetrahydro‐4H‐1,3,5,2λ⁵‐furo[3,2‐d][1,3,2λ⁵]dioxaphosphinin‐2‐olate], C₆H₁₀N₃O₂⁺·C₁₀H₁₀N₄O₇P⁻, the Hoogsteen edge of the hypoxanthine (Hyp) base of cIMP and the Hyp face are engaged in specific amino acid–nucleotide (His...cIMP) recognition, i.e. by abutting edge‐to‐edge and by π–π stacking, respectively. The Watson–Crick edge of Hyp and the cIMP phosphate group play a role in nonspecific His...cIMP contacts. The interactions between the cIMP anions (anti/C3′–endo/trans–gauche/chair conformers) are realized mainly between riboses and phosphate groups. The results for this l ‐His–cIMP complex, compared with those for the previously reported solvated l ‐His–IMP crystal structure, indicate a different nature of amino acid–nucleotide recognition and interactions upon the 3′:5′‐cyclization of the nucleotide phosphate group.     

Synthesis and characterization of macroinitiator‐amino terminated PEG and poly(γ‐benzyl‐L‐glutamate)‐PEO‐poly(γ‐benzyl‐L‐glutamate) triblock copolymer

Macroinitiator‐amino terminated poly(ethylene glycol) (PEG) (NH₂‐PEO‐NH₂) was prepared by converting both terminal hydroxyl groups of PEG to more reactive primary amino groups. The synthetic route involved reactions of chloridize, phthalimide and finally hydrazinolysis. Furthermore, poly(γ‐benzyl‐L ‐glutamate)‐poly(ethylene oxide)‐poly(γ‐benzyl‐L ‐glutamate) (PBLG‐PEO‐PBLG) triblock copolymer was synthesized by polymerization of γ‐benzyl‐L ‐glutamate N‐carboxyanhydride (Bz‐L‐GluNCA) using NH₂‐PEO‐NH₂ as macroinitiator. The resultant NH₂‐PEO‐NH₂ and triblock copolymer were characterized by FT‐IR, ¹H‐NMR and gel permeation chromatography (GPC) techniques. The results demonstrated that the degree of amination of the NH₂‐PEO‐NH₂ could be up to 1.95. The molecular weight of the PBLG‐PEO‐PBLG triblock copolymer could be adjusted easily by controlling the molar ratio of Bz‐L ‐Glu NCA to the macroinitiator NH₂‐PEO‐NH₂. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis,Spectroscopy, and Structures of Mono‐ and Dinuclear Copper(I) Halide Complexes with 1,3‐Imidazolidine‐2‐thiones

Copper(I) halides with triphenyl phosphine and imidaozlidine‐2‐thiones (L ‐NMe, L ‐NEt, and L ‐NPh) in acetonitrile/methanol (or dichloromethane) yielded copper(I) mixed‐ligand complexes: mononuclear, namely, [CuCl(κ¹‐S‐L ‐NMe)(PPh₃)₂] ( 1 ), [CuBr(κ¹‐S‐L ‐NMe)(PPh₃)₂] ( 2 ), [CuBr(κ¹‐S‐L ‐NEt)(PPh₃)₂] ( 5 ), [CuI(κ¹‐S‐L ‐NEt)(PPh₃)₂] ( 6 ), [CuCl(κ¹‐S‐L ‐NPh)(PPh₃)₂] ( 7 ), and [CuBr(κ¹‐S‐L ‐NPh)(PPh₃)₂] ( 8 ), and dinuclear, [Cu₂(κ¹‐I)₂(μ‐S‐L ‐NMe)₂(PPh₃)₂] ( 3 ) and [Cu₂(μ‐Cl)₂(κ¹‐S‐L ‐NEt)₂(PPh₃)₂] ( 4 ). All complexes were characterized with analytical data, IR and NMR spectroscopy, and X‐ray crystallography. Complexes 2 – 4 , 7 , and 8 each formed crystals in the triclinic system with P$\bar{1}$ space group, whereas complexes 1 , 5 , and 6 crystallized in the monoclinic crystal system with space groups P2₁/c, C2/c, and P2₁/n, respectively. Complex 2 has shown two independent molecules, [(CuBr(κ¹‐S‐L ‐NMe)(PPh₃)₂] and [CuBr(PPh₃)₂] in the unit cell. For X = Cl, the thio‐ligand bonded to metal as terminal in complex 4 , whereas for X = I it is sulfur‐bridged in complex 3 .     

Novel Carbohydrate‐Appended Metal Complexes for Potential Use in Molecular Imaging

Seven discrete sugar‐pendant diamines were complexed to the {M(CO)₃}⁺ (^99mTc/Re) core: 1,3‐diamino‐2‐propyl β‐D ‐glucopyranoside ( L ¹ ), 1,3‐diamino‐2‐propyl β‐D ‐xylopyranoside ( L ² ), 1,3‐diamino‐2‐propyl α‐D ‐mannopyranoside ( L ³ ), 1,3‐diamino‐2‐propyl α‐D ‐galactopyranoside ( L ⁴ ), 1,3‐diamino‐2‐propyl β‐D ‐galactopyranoside ( L ⁵ ), 1,3‐diamino‐2‐propyl β‐(α‐D ‐glucopyranosyl‐(1,4)‐D ‐glucopyranoside) ( L ⁶ ), and bis(aminomethyl)bis[(β‐D ‐glucopyranosyloxy)methyl]methane ( L ⁷ ). The Re complexes [Re( L ¹ – L ⁷ )(Br)(CO)₃] were characterized by ¹H and ¹³C 1D/2D NMR spectroscopy which confirmed the pendant nature of the carbohydrate moieties in solution. Additional characterization was provided by IR spectroscopy, elemental analysis, and mass spectrometry. Two analogues, [Re( L ² )(CO)₃Br] and [Re( L ³ )(CO)₃Br], were characterized in the solid state by X‐ray crystallography and represent the first reported structures of Re organometallic carbohydrate compounds. Conductivity measurements in H₂O established that the complexes exist as [Re( L ¹ – L ⁷ )(H₂O)(CO)₃]Br in aqueous conditions. Radiolabelling of L ¹ – L ⁷ with [^99mTc(H₂O)₃(CO)₃]⁺ afforded in high yield compounds of identical character to the Re analogues. The radiolabelled compounds were determined to exhibit high in vitro stability towards ligand exchange in the presence of an excess of either cysteine or histidine over a 24 h period.     

Zn‐ and Cd‐based Coordination Polymers Offering H‐Bonding Cavities: Highly Selective Sensing of S2O72− and Fe3+ Ions

We present two Zn^II‐ and Cd^II‐based coordination polymers (CPs), L ‐Zn and L ‐Cd , offering H‐bonding‐based cavities of varying dimensions. Both CPs were used for the highly selective detection of S₂O₇^2? and Fe³⁺ ions where H‐bonding based cavities played an important role. Fluorescence quenching, competitive binding studies and binding parameters substantiated significant recognition of S₂O₇^2? and Fe³⁺ ions by both CPs.