Excitation energy-transfer processes between two trimers in C-phycocyanin hexamer from the cyanobacterium Anabaena variabilis. Investigation by group theory and time-resolved fluorescence spectroscopy

We have employed group theory and picosecond time-resolved fluorescence isotropy and anisotropy spectroscopy methods to explore the excitation transfers within an isolated C-phycocyanin (C-PC) hexamer (αβ)₆^PCL²⁷_RC, situated at the end of the rod proximal to the core of the pycobilisome (PBS) in the cyanobacterium Anabaena variabilis. The group-theory results imply that excitation energy transfer between two trimers occurs between the lowest exciton level of each trimer. The excitation energy-transfer process might occur at a rate of 10–20 ps, and it may be described by an exciton hopping-like Förster transfer mechanism. Dynamic components of 45–50 ps are assigned to the excitation transfer from β₁₅₅-PCB chromophores to the exciton states of dimers, which consist of two neighbouring monomers of the same trimer in an isolated C-PC hexamer.     

Efficient Photoconversion Distorts the Fluorescence Lifetime of GFP in Confocal Microscopy: A Model Kinetic Study on Mutant Thr203Val

Phototransformations of autofluorescent proteins are applied in high‐resolution microscopy and in studying cellular transport, but they are detrimental when accidentally occurring in blinking or photobleaching (BL). Here, we investigate the kinetics of phototransformations of a photoactivatable green fluorescent protein (GFP) in confocal microscopy. Photoconversion (PC) is achieved by excitation of the barely present anionic chromophore state R_eq^? in the GFP mutant Thr203Val. Besides the shift of the equilibrium between the neutral chromophore state RH and R_eq^?, the photoconverted anionic chromophore R_PC^? exhibits a reduced fluorescence lifetime τ_fl=2.2 ns. In fluorescence lifetime imaging microscopy, τ_fl is found to depend, however, on the excitation conditions and history. The underlying photochemistry is described by the kinetic scheme of consecutive reactions, R_eq^?→R_PC^?→P_dark, in which the anionic chromophore species and the dark protein P_dark are coupled by PC and BL. Time‐correlated single‐photon‐counting detection in a confocal geometry of freely diffusing species is used to compute the quantum yields for PC and BL, Φ_PC and Φ_BL. The assessed values are Φ_PC=5.5×10^?4 and Φ_BL>1×10^?5. Based on these values, PC provokes misinterpretation in fluorescence resonance energy transfer experiments and is responsible for spectroscopic peculiarities in single‐molecule detection.     

Redox properties of (RC2R')Co2(CO)6-nLn and reactivity of (RC2R')Co2(CO)6-nLn towards PPh3[LPPh3, P(OEt)3]

Cyclic voltammetric studies of clusters (C₅H₅-C₂C₆ H₄-R-p)Co₂(CO)6-n L_n[n=0,2; L=PPh₃, P(OEt)₃] and (RCH₂C)₂Co₂(CO₄) (PPh₃)₂ on Pt electrode are described. The primary reduction (0 / ?1) and oxidation (+ 1 / 0) steps are considered as a mono-electron process for all clusters. For the clusters (C₅H₅C₂C₆H₄-R-p)Co₂(CO)₆, a good linear relation between reduction potential E_p^red and Hammett constant σ_p of R in the clusters is found. For the clusters (RC₂R')Co₂(CO)₄L₂, their radical anions are extremely unstable at room temperature and fragment into a series of mononuclear species, one of which is (RC₂R')Co(CO)₂PPh₃. The reaction of radical anions of (RC₂R')Co₂(CO)_6–n (PPh₃)_n(n=0,2) with PPh₃ also produces mononuclear species (RC₂R')Co(CO)₂PPh₃ which has been detected by means of cyclic voltammetry and ESR. The influence of R on redox properties of clusters is discussed.     

Synthesis and characterization of cyclic P3HT as a donor polymer for organic solar cells

In this study, cyclic poly(3‐hexylthiophene‐2,5‐diyl) (c‐P3HT) with a controlled M_n was synthesized by the intramolecular cyclization of α‐bromo‐ω‐ethynyl‐functionalized P3HT via the Sonogashira coupling reaction. The effect of the cyclic structure, which does not have terminal groups of polymers, on the photoelectric conversion characteristics was investigated in comparison to linear P3HT (l‐P3HT). c‐P3HT was successfully synthesized with M_n ≈ 17,000, dispersity ≈ 1.2, and regioregularity ≈ 99%. The hole mobility was determined to be 5.1 × 10^?4 cm² V^?1 s^?1 by time‐of‐flight (TOF) experiment. This was comparable to that of l‐P3HT of 5.6 × 10^?4 cm² V^?1 s^?1. Organic solar cell systems were fabricated with each polymer by blending them with [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM). The l‐P3HT:PC₇₁BM system showed a dispersive TOF photocurrent profile for electron transport, whereas a nondispersive profile was observed for c‐P3HT:PC₇₁BM. In addition, an amount of collected electrons in c‐P3HT:PC₇₁BM was greater than that in l‐P3HT:PC₇₁BM for TOF experiments. The photoelectric conversion characteristics were improved by using c‐P3HT rather than l‐P3HT (power conversion efficiency [PCE] = 4.05% vs 3.23%), reflecting the nondispersive transport and the improvement of electron collection. PCEs will be much improved by applying this cyclic concept to highly‐efficient OSC polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 266–271     

ESR and quantum-chemical studies of the structure and thermal transformations of vinylcyclopropane radical cations in irradiated frozen Freon matrices. Simulation of radical processes in the gas phase

Thermal trasfomations of vinylcyclopropane (VCP) radical cations (RC) in X-ray irradiated frozen Freon matrices, CFCl₂CF₂Cl and CFCl₃, were studed by ESR. Radical processes involving VCP^.+ in very rarefied and moderately thickened gaseous VCP were simulated. Monomolecular cleavage of the cyclopropane ring ofgauche-VCP^.+ (1) occurs to give the more thermally stable distonic radical cationdist(0.90)-C₅H₈ ^.+ (3). As the density of VCP increases RC3 adds at the double bond ofanti-VCP to give the distonic RC,^.CH₂CH₂CHCH(CH₂)₃CHCHCH₂ ⁺ (5). Under the same conditions, the less thermally stableanti-VCP^.+(2) undergoes monomolecular isomerization into RC1 or reacts withanti-VCP with the rearrangement (as in the condensed phase) to give its distonic form,dist(90.0)-C₅H₈ ^.+ (4). The MNDO-UHF method was adapted for quantum-chemical analysis of the constants of isotropic hyperfine coupling with¹H and¹³C nuclei in neutral and charged hydrocabon radicals, since the standard version of this method inadequately reproduces the structural parameters of low-symmetry (C ₁,C _s) paramagnetic species. A quantum-chemical analysis of the radiospectroscopic information and of the stereoelectronic control of thermal transformations of conformers of RC1 and2 into their structurally nonequivalent distonic forms3 and4, respectively, was carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 212–235, February, 1995.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-04075).     

Mass spectrometry of transition metal π-complexes. XV—The effect of substituents on the fragmentation of benchrotrenyls under electron impact

Mass spectra of substituted benchrotrenyls RC₆H₅Cr(CO)₃ where R?H, F, CI, I, CH₃, OCH₃, COOCH₃, C₂H₅, N(CH₃)₂, NH₂, C₆H₅, C(CH₃)₃, p-C₆H₄NH₂, CH₂C₆H₅, CH₂CH₂C₆H₅), 1,3,5-(CH₃)₃C₆H₃Cr(CO)₃ and 1,2,3,5-(CH₃)₄C₆H₂Cr(CO)₃ have been studied. It has been found that for monosubstituted benchrotrenyls there is a linear dependence of the parameter log [Cr]⁺/[RC₆H₅Cr]⁺) on the number of degrees of freedom of the [RC₆H₅Cr]⁺ ion. Decarbonylation of the molecular ions is not affected by the nature of the substituent R. The results are interpreted in terms of the quasi-equilibrium theory of mass spectra.     

Synthesis,Antiproliferative Activity and DNA-Binding Properties of Nitrogen and Sulfur Heterocyclic Norcantharidin Acylamide Acid

Three novel norcantharidin acylamide acids (L¹?N‐thiadiazole norcantharidin acylamide acid, C₁₀H₁₁N₃O₄S; L²?N‐thiazole norcantharidin acylamide acid, C₁₁H₁₂N₂O₄S and L³?N‐benzothiazole norcantharidin acylamide acid, C₁₅H₁₄N₂O₄S) were synthesized by the reactions of norcantharidin (NCTD?7‐oxabicyclo[2,2,1]heptane‐2,3‐dicarboxylic acid anhydride, C₈H₈O₄) with 2‐amino‐1,3,4‐thiadiazole (C₂H₃N₃S), 2‐aminothiazole (C₃H₄N₂S) and 2‐aminobenzothiazole (C₇H₆N₂S), respectively. Their structures were characterized by elemental analysis, IR, and NMR. The inhibition rates of L³ was much higher than those of L¹ and L² against human hepatoma cells SMMC7721 cell lines in vitro. The interaction between the compounds and DNA was studied by means of fluorescence quenching studies and viscosity measurements. The emission intensities decreased obviously with increasing concentration of the compounds in the fluorescence quenching experiments. The linear Stern‐Volmer quenching constant K_sq values were 0.62 (L¹), 0.55 (L²) and 1.08 (L³), respectively. The binding abilities followed the trend from high to low were L³, L¹ and L², respectively. The results of viscosity measurements showed that L¹ and L² might bind to DNA via partial intercalation, while L³ bound mainly in intercalation.     

Analysis of Phytochelatins and Other Thiol-Containing Compounds by RP-HPLC with Monobromobimane Precolumn Derivatization

In this article, a method for quantitative determination of phytochelatins (PC _n being the classic example) and other thiol-containing compounds in mixed standard solution and plant tissues is presented. Thiols were converted to fluorescent derivatives by precolumn derivatization with monobromobimane. The results showed that PC _n and other thiol-containing compounds in standard mixed solutions were rapidly separated within 15 min by using a ACN 0.1% trifluoroacetic acid binary gradient elution. Glutathione was representatively selected to test the precision of this method. The calibration curve was linear in the range of 1.25–160 ng μl⁻¹ (regression coefficient r ²=0.9999). It was confirmed that this method was rapid, simple, highly sensitive, stable, and had the property of simultaneous determination of PC _n and other thiol-containing compounds. This method was applied to determine PC _n and other thiol-containing compounds in a Cd hyperaccumulator Sedum alfredii in response to Cd. It was found that no PC _n was detected in any tissue at any Cd treatment, suggesting that Cd hyperaccumulation and detoxification in this plant is not based on PC synthesis. Translated from Journal of Nanjing University (Natural Science Edition), 2005, 41(3) (in Chinese)     

Structural features of the phosphorus heterocumulene ylides (<Emphasis Type="Italic">sp</Emphasis>-ylides)

The features in phosphorus heterocumulene yilides Ph₃PCCX [X = NPh, NC(O)Ph, C(CN)CO · (OMe), O, S] with the ylide carbon geometry close to sp-hybridization are studied using ab initio methods. Estimation of structural parameters of a new member in the Ph₃PC^α=C^β=NC(O)Ph series on the B3LYP/6-31G(d,p) level and together with experimental data for related ylide (X = NPh) gave the following values: r(PC^α) 1.665 Å, r(C^α=C^β) 1.237 Å, ω(PC^αC^β) 145.2°. Nonvalent interactions of sp ^λ orbital of the ylide carbon atom bearing extra negative charge with coplanar π-electrons of the nearest C^β=N bond are found close to those of nitrogen lone pair with the C^α=C^β bond and leading to up to 10° nonlinearity of C^α-C^β=N triad of the phosphorus iminoketene ylides. Chemical nonequivalence of the PC^ipso bonds in the triphenylphosphonium fragment, relation of \(^1 J_{PC^\alpha } \) spin-spin coupling and antisymmetric bonding vibration ν^as(C=C=X) to the structure of the carbanion, and inductive hyperconjugative influence of atom (or group) X on the ylide carbon geometry are discussed.     

Organoaluminum Compounds as Catalysts for Monohydroboration of Carbodiimides

The effective catalytic activity of organoaluminum compounds for the monohydroboration of carbodiimides has been demonstrated. Two aluminum complexes, 2 and 3 , were synthesized and characterized. The efficient catalytic performances of four aluminum hydride complexes L¹AlH₂ (L¹=HC(CMeNAr)₂, Ar=2,6-Et₂C₆H₃; 1 ), L²AlH₂(NMe₃) (L²=o-C₆H₄F(CH=N-Ar), Ar=2,6-Et₂C₆H₃; 2 ), L³AlH (L³=2,6-bis(1-methylethyl)-N-(2-pyridinylmethylene)phenylamine; 3 ), and L⁴AlH(NMe₃) (L⁴=o-C₆H₄(N-Dipp)(CH=N-Dipp), Dipp=2,6-iPr₂C₆H₃; 4 ), and an aluminum alkyl complex L¹AlMe₂ ( 5 ) were used for the monohydroboration of carbodiimides investigated under solvent-free and mild conditions. Compounds 1 – 3 and 5 can produce monohydroborated N-borylformamidine, whereas 4 can afford the C-borylformamidine product. A suggested mechanism of this reaction was explored, and the aluminum formamidinate compound 6 was characterized by single-crystal X-ray, also a stoichiometric reaction was investigated.     

Analytical approach for characterization of cadmium-induced thiol peptides—a case study using <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

Phytochelatins (PC) were described earlier to play a role in metal detoxification in Chlamydomonas reinhardtii but were not clearly identified. The focus of this case study was to identify PC synthesized by C. reinhardtii exposed to Cd. Only low intracellular concentrations of cadmium (85 nmol g⁻¹ fresh weight) were sufficient to cause significant changes in thiol peptide pools. Thus, results showed a progressive decline of the glutathione content, accompanied by an induction of phytochelatins. Not only canonic phytochelatins but for the first time also the iso-phytochelatins CysPC _n and PC₂Ala were identified in this unicellular green alga using electrospray ionization quadrupole time-of-flight tandem mass spectrometry. Additionally, CysPC _n desGly, PC _n desGly, CysPC _n Glu, and PC₂Glu were found throughout MS analysis. Also, low abundant PCs could be detected due to the high sample preconcentration combined with little sample amounts (0.3 μL min⁻¹) necessary for electrospray. Identified PCs had a maximum number of 5 γ-glutamyl cysteine (γ-GluCys) units. Thiol peptides of higher molecular masses suggesting PC _n with n > 5 could be identified as intermolecular oxidation products of smaller PCs. Thiols may easily be oxidized. Therefore, PCs were reduced prior to MS analysis. Dithiothreitol and tris(2-carboxyethyl) phosphine were compared concerning their reduction effort.      

Stability of arsenic peptides in plant extracts: off-line versus on-line parallel elemental and molecular mass spectrometric detection for liquid chromatographic separation

The instability of metal and metalloid complexes during analytical processes has always been an issue of an uncertainty regarding their speciation in plant extracts. Two different speciation protocols were compared regarding the analysis of arsenic phytochelatin (As^IIIPC) complexes in fresh plant material. As the final step for separation/detection both methods used RP-HPLC simultaneously coupled to ICP-MS and ES-MS. However, one method was the often used off-line approach using two-dimensional separation, i.e. a pre-cleaning step using size-exclusion chromatography with subsequent fraction collection and freeze-drying prior to the analysis using RP-HPLC–ICP-MS and/or ES-MS. This approach revealed that less than 2% of the total arsenic was bound to peptides such as phytochelatins in the root extract of an arsenate exposed Thunbergia alata, whereas the direct on-line method showed that 83% of arsenic was bound to peptides, mainly as As^IIIPC₃ and (GS)As^IIIPC₂. Key analytical factors were identified which destabilise the As^IIIPCs. The low pH of the mobile phase (0.1% formic acid) using RP-HPLC–ICP-MS/ES-MS stabilises the arsenic peptide complexes in the plant extract as well as the free peptide concentration, as shown by the kinetic disintegration study of the model compound As^III(GS)₃ at pH 2.2 and 3.8. But only short half-lives of only a few hours were determined for the arsenic glutathione complex. Although As^IIIPC₃ showed a ten times higher half-life (23 h) in a plant extract, the pre-cleaning step with subsequent fractionation in a mobile phase of pH 5.6 contributes to the destabilisation of the arsenic peptides in the off-line method. Furthermore, it was found that during a freeze-drying process more than 90% of an As^IIIPC₃ complex and smaller free peptides such as PC₂ and PC₃ can be lost. Although the two-dimensional off-line method has been used successfully for other metal complexes, it is concluded here that the fractionation and the subsequent freeze-drying were responsible for the loss of arsenic phytochelatin complexes during the analysis. Hence, the on-line HPLC–ICP-MS/ES-MS is the preferred method for such unstable peptide complexes. Since freeze-drying has been found to be undesirable for sample storage other methods for sample handling needed to be investigated. Hence, the storage of the fresh plant at low temperature was tested. We can report for the first time a storage method which successfully conserves the integrity of the labile arsenic phytochelatin complexes: quantitative recovery of As^IIIPC₃ in a formic acid extract of a Thunbergia alata exposed for 24 h to 1 mg As^v L⁻¹ was found when the fresh plant was stored for 21 days at 193 K. Figure On-line HPLC–ICP-MS/ES-MS (bottom) is the preferred method for MS determination of unstable arsenic peptide complexes in plant extracts, since this avoids fractionation and subsequent freeze-drying that are responsible for loss of arsenic phytochelatin complexes in the 2D off-line method (top) Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Voltammetric Analysis of Phytochelatin Complexation in Ternary Metal Mixtures Supported by Multivariate Analysis and ESI‐MS

The competitive binding of Cu²⁺, Cd²⁺ and Pb²⁺ in ternary mixtures by the phytochelatins PC₂ and PC₅ (PC_n; (γGlu‐Cys)_n‐Gly, n=2 and 5) are examined by voltammetry, which allows one to follow the displacements of the voltammetric signals induced by the competitive binding among the metal ions towards PC₂ or PC₅ complexation, and direct injection positive‐mode Electrospray Ionization Mass Spectrometry (ESI‐MS), in order to obtain the stoichiometries of the complexes. Voltammetric data are analyzed by Gaussian Peak Adjustment (GPA), which is a recently developed multivariate analysis method for nonlinear electrochemical data. Different complexes have been detected or deduced their presence, depending on the experimental conditions. Ternary complexes CuCdPC_n and CdPbPC_n were detected for both PC₂ and PC₅, while the ternary CuPbPC_n complex was only detected for PC₂. Some of the complexes have been only detected by ESI‐MS because in some cases voltammetry data could not be totally resolved, even by using GPA. The quaternary CdPbCuPC_n complex has been detected for PC₅, but for PC₂ data are not so conclusive. In summary, the signal evolution for mixed CdCuPC_n complexes is quite different. These observations could be a reflection of an antagonistic effect for the case of PC₂ and a synergetic one for PC₅.     

Cyclooctenyl complexes of palladium(II) with multidentate N-heterocycles

[Pd(cod)(cotl)]ClO₄ (cod = 1,5-cyclooctadiene, cotl = cyclooctenyl, C₈H₁₃ ^–) undergoes substitutions with multidentate N-heterocycles: 1,3-bis(benzimidazolyl)benzene (L¹), 1,3-bis(1-methylbenzimidazol-2-yl)benzene (L²), 2,6-bis(benzimidazolyl)pyridine (L³) and 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (L⁴) to yield mono/binuclear complexes: [Pd(cotl)(L¹)(OClO₃)], [Pd(cotl)(L)]ClO₄ (L = L² or L³) and [Pd(cotl)₂(L⁴)](ClO₄)₂. Dihalobridged binuclear complexes [PdX(cotl)]₂ (X = Cl or Br) undergo halogen bridge cleavages with the multidentate N-heterocycles to form binuclear complexes of the type [PdX(cotl)₂L] (X = Cl or Br; L = L¹, L², L³ or L⁴). The complexes were characterized by elemental analyses, ¹H-, ¹³C-n.m.r., i.r., far-i.r. and FAB-mass spectral studies.     

Preparation of Complexes of Nickel(II) Aryl Carboxylates with Morpholine and Piperidine

Complexes of nickel(II) aryl carboxylates with a general formula Ni(RC₆H₄COO)₂L₂ where R=H, p-CH₃. p-Cl, m- & p-NO₂; and L = morpholine and piperidine; have been prepared by the interaction of nickel(II) aryl carboxylates with a large excess of appropriate amine. Unlike parent anhydrous nickel(II) aryl carboxylates all these complexes are soluble in common organic solvents.     

Less Is More: Three‐Coordinate C,N‐Chelated Distannynes and Digermynes

We report here the synthesis of new C,N‐chelated chlorostannylenes and germylenes L³MCl (M=Sn( 1 ), Ge ( 2 )) and L⁴MCl (M=Sn( 3 ), Ge ( 4 )) containing sterically demanding C,N‐chelating ligands L^{3, 4} (L³=[2,4‐di‐tBu‐6‐(Et₂NCH₂)C₆H₂]^?_; L⁴=[2,4‐di‐tBu‐6‐{(C₆H₃‐2′,6′‐iPr₂)N=CH}C₆H₂]^?). Reductions of 1 – 4 yielded three‐coordinate C,N‐chelated distannynes and digermynes [L^{3, 4}M ]₂ for the first time ( 5 : L³, M=Sn, 6 : L³, M=Ge, 7 : L⁴, M=Sn, 8 : L⁴, M=Ge). For comparison, the four‐coordinate distannyne [L⁵Sn]₂ ( 10 ) stabilized by N,C,N‐chelate L⁵ (L⁵=[2,6‐{(C₆H₃‐2′,6′‐Me₂)N?CH}₂C₆H₃]^?) was prepared by the reduction of chlorostannylene L⁵SnCl ( 9 ). Hence, we highlight the role of donor‐driven stabilization of tetrynes. Compounds 1 – 10 were characterized by means of elemental analysis, NMR spectroscopy, and in the case of 1 , 2 , 5 – 7 , and 10 , also by single‐crystal X‐ray diffraction analysis. The bonding situation in either three‐ or four‐coordinate distannynes 5 , 7 , and 10 was evaluated by DFT calculations. DFT calculations were also used to compare the nature of the metal–metal bond in three‐coordinate C,N‐chelating distannyne [L³Sn]₂ ( 5 ) and related digermyme [L³Ge]₂ ( 6 ).     

Development of an electrochemical sensor based on Schiff base for Cu(II) determination at nano level in river water and edible materials

Plasticised membranes using 2-[{(2-hydroxyphenyl)imino}methyl]-phenol (L₁) and 2-[{(3-hydroxyphenyl)imino}methyl]-phenol (L₂), have been prepared and investigated as Cu²⁺ ion-selective sensors. Effect of various plasticisers, namely, dibutyl phthalate (DBP), dibutyl sebacate (DBS), benzyl acetate (BA), o-nitrophenyloctylether (o-NPOE) and anion excluders, oleic acid (OA) and sodium tetraphenylborate (NaTPB) was studied and improved performance was observed in several instances. Optimum performance was observed with membranes of (L₁) having composition L₁ : DBS : OA : PVC in the ratio of 6 : 54 : 10 : 30 (w/w, %). The sensor works satisfactorily in the concentration range 3.2 × 10^?8–1.0 × 10^?1 mol L^?1 with a Nernstian slope of 29.5 ± 0.5 mV decade^?1 of a _cu²⁺ . The detection limit of the proposed sensor is 2.0 × 10^?8 mol L^?1 (1.27 ng mL^?1). Wide pH range (3.0–8.5), fast response time (7 s), sufficient (up to 25% v/v) non-aqueous tolerance and adequate shelf life (3 months) indicate the utility of the proposed sensor. The potentiometric selectivity coefficients as determined by matched potential method indicate selective response for Cu²⁺ ions over various interfering ions, and therefore could be successfully used for the determination of copper in edible oils, tomato plant material and river water.     

Zur kenntnis nichtmetallischer iminverbindungen : LXVIII . 2,4,1η5,3η3-diazadiphosphetidin,ein phosphorstickstoff-vierring mit 3- und 5-bindigem phosphor

The complex Mo(CO)₂L₂ [L = S₂CNEt₂] reacts with acetylenes to yield both Mo(CO)(RC₂R')L₂ and Mo(RC₂R')₂L₂, with diazenes giving Mo(RN₂R')L₂ and Mo(RC₂R')₂L₂, with diazenes giving Mo(RN₂R')L₂ and Mo(RN₂R')₂L₂, and with CO and PPh₃ to form Mo(CO)₃L₂ and Mo(CO)₂(PPh₃)L₂.     

Di‐μ‐hydroxido‐bis{[bis(6‐methyl‐2‐pyridylmethyl)(2‐phenylethyl)amine‐κ3N′,N′′,N′′′]copper(II)} bis(perchlorate)

The title compund, [Cu₂(OH)₂(C₂₂H₂₅N₃)₂](ClO₄)₂, is a copper(II) dimer, with two [CuL]²⁺ units [L is bis(6‐methyl‐2‐pyridylmethyl)(2‐phenylethyl)amine] bridged by hydroxide groups to define the {[CuL](μ‐OH)₂[CuL]}²⁺ cation. Charge balance is provided by perchlorate counter‐anions. The cation has a crystallographic inversion centre halfway between the Cu^II ions, which are separated by 3.0161 (8) Å. The central core of the cation is an almost regular Cu₂O₂ parallelogram of sides 1.931 (2) and 1.935 (2) Å, with a Cu—O—Cu angle of 102.55 (11)°. The coordination geometry around each Cu^II centre can be best described as a square‐based pyramid, with three N atoms from L ligands and two hydroxide O atoms completing the coordination environment. Each cationic unit is hydrogen bonded to two perchlorate anions by means of hydroxide–perchlorate O—H...O interactions.     

A one‐dimensional coordination polymer of 5‐[(imidazol‐1‐yl)methyl]benzene‐1,3‐dicarboxylic acid with CuII cations

5‐[(Imidazol‐1‐yl)methyl]benzene‐1,3‐dicarboxylic acid (H₂L) was synthesized and the dimethylformamide‐ and dimethylacetamide‐solvated structures of its adducts with Cu^II, namely catena‐poly[[copper(II)‐bis[μ‐3‐carboxy‐5‐[(imidazol‐1‐yl)methyl]benzoato]] dimethylformamide disolvate], {[Cu(C₁₂H₉N₂O₄)₂]·2C₃H₇NO}_n, (I), and catena‐poly[[copper(II)‐bis[μ‐3‐carboxy‐5‐[(imidazol‐1‐yl)methyl]benzoato]] dimethylacetamide disolvate], {[Cu(C₁₂H₉N₂O₄)₂]·2C₄H₉NO}_n, (II), the formation of which are associated with mono‐deprotonation of H₂L. The two structures are isomorphous and isometric. They consist of one‐dimensional coordination polymers of the organic ligand with Cu^II in a 2:1 ratio, [Cu(μ‐HL)₂]_n, crystallizing as the dimethylformamide (DMF) or dimethylacetamide (DMA) disolvates. The Cu^II cations are characterized by a coordination number of six, being located on centres of crystallographic inversion. In the polymeric chains, each Cu^II cation is linked to four neighbouring HL⁻ ligands, and the organic ligand is coordinated via Cu—O and Cu—N bonds to two Cu^II cations. In the corresponding crystal structures of (I) and (II), the coordination chains, aligned parallel to the c axis, are further interlinked by strong hydrogen bonds between the noncoordinated carboxy groups in one array and the coordinated carboxylate groups of neighbouring chains. Molecules of DMF and DMA (disordered) are accommodated at the interface between adjacent polymeric assemblies. This report provides the first structural evidence for the formation of coordination polymers with H₂Lvia multiple metal–ligand bonds through both carboxylate and imidazole groups.