- A Cyclic-RGD Dinuclear TbIII Macrocyclic Complex as a Tumor Integrin-Selective Luminescent Probe
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To develop small molecular integrin-selective luminescent imaging probes, we have prepared the binary dipicolinate (DPA) TbIII dinuclear macrocyclic complex, Tb2(cRGDfK-ODO2A-dimer) (DPA)22– or complex I, and reference ligands and TbIII complexes which were purified by HPLC and characterized by NMR, mass spectrometry and luminescence spectroscopy. Luminescence titrations of the structural and bonding model Tb2(m-ODO2A-dimer)2+ complex by DPA2– ion confirmed the molecular formula of the adduct was Tb2(m-ODO2A-dimer)(DPA)22–, and the first binary binding constant was determined to be log K1 = 5.76. At pH 7.4, complex I showed 300 times luminescence enhancement at 544 nm (λex = 278 nm) as compared to that without adding DPA, and was found to bind to αvβ3 integrin and human glioblastoma U87MG tumor cells in both specific and non-specific modes, via luminescence spectroscopic and confocal cell imaging competition studies. This makes complex I and its future optimized derivatives potentially feasible for preclinical bioimaging applications, particularly in the time-resolved mode.
- Chang, C. Allen,Chia, Ju-Chien,Lin, Syue-Liang
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Read Online
- Bimetallic lanthanide complexes derived from macrocycle-appended m-xylyl derivatives: Synthesis and spectroscopic properties
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A series of bimetallic lanthanide complexes was prepared from a bimacrocyclic system in which two DO3A units are linked by a m-xylyl unit appended with either a NO2 or an NH2 group (DO3A=1,4,7,10-tetraazacyclododecane-1,4,7-triacetic
- Placidi, Matteo P.,Natrajan, Louise S.,Sykes, Daniel,Kenwright, Alan M.,Faulkner, Stephen
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Read Online
- Semi-shelled melon ring C containing aniline structure33 H39 O3 N9 Synthesis method and synthesis method thereof
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The invention discloses a semi-melon ring C containing an aniline structure. 33 H39 O3 N9 , The C33 H39 O3 N Chemistry name 35 , 75 , 115 - Triamino -1 , 5, 9 (1, 3) - triazoline generation -3 , 7, 11 (1, 3) - triphenyl cyclododecatriene -12 , 52 , 92 ; Trione. C33 H39 O3 N9 The synthesis method of 5 -nitrobenzene -1, 3 - diacid-AONS-3,5 - bis - (bromomethyl) nitrobenzene-AOE286928692X0AO_ 3,5 bis (- 1,3 - (bromomethyl) -5 - 3 - 3,5 - nitrobenzene 3 -2 -) imidazoli -2 -AOE286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869286928692869 5 . 5 , 75 , 115 - Trinitro -1 , 5, 9 (1, 3) - triazoline generation -3 , 7, 11 (1, 3) - triphenyl cyclododecatriene -12 , 52 , 92 - Triketone-AOE 286928692X0AO_ 35 , 75 , 115 - Triamino -1 , 5, 9 (1, 3) - triazoline generation -3 , 7, 11 (1, 3) - triphenyl cyclododecatriene -12 , 52 , 92 ; Trione. C33 H39 O3 N9 Can regard as Fe3 + A detector; and a detector. The utility model can also be used as a detector for nitrophenol substances. The synthesis method has the characteristics of simplicity, rapidness, easiness in operation, low cost and the like.
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Paragraph 0032; 0055-0056; 0077-0078; 0083-0084; 0089-0090
(2021/10/27)
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- Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions
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A novel hemicucurbituril-based macrocycle, alternately consisting of amidobenzene and 2-imidazolidione moieties was designed and synthesized. Based on the fragment coupling strategy, nitrobenzene-containing hemicucurbituril was firstly prepared facilely u
- Cong, Hang,Ge, Qingmei,Liu, Mao,Long, Qiumeng,Lu, Jihong,Wang, Li,You, Yuting,Yuan, Xiaoting,Zeng, Qingkai,Zhang, Qianjun
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p. 2840 - 2847
(2022/01/03)
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- Liquid-Crystalline Star-Shaped Supergelator Exhibiting Aggregation-Induced Blue Light Emission
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A family of closely related star-shaped stilbene-based molecules containing an amide linkage are synthesized, and their self-assembly in liquid-crystalline and gel states was investigated. The number and position of the peripheral alkyl tails were systematically varied to understand the structure-property relation. Interestingly, one of the molecules with seven peripheral chains was bimesomorphic, exhibiting columnar hexagonal and columnar rectangular phases, whereas the rest of them stabilized the room-temperature columnar hexagonal phase. The self-assembly of these molecules in liquid-crystalline and organogel states is extremely sensitive to the position and number of alkoxy tails in the periphery. Two of the compounds with six and seven peripheral tails exhibited supergelation behavior in long-chain hydrocarbon solvents. One of these compounds with seven alkyl chains was investigated further, and it has shown higher stability and moldability in the gel state. The xerogel of the same compound was characterized with the help of extensive microscopic and X-ray diffraction studies. The nanofibers in the xerogel are found to consist of molecules arranged in a lamellar fashion. Furthermore, this compound shows very weak emission in solution but an aggregation-induced emission property in the gel state. Considering the dearth of solid-state blue-light-emitting organic materials, this molecular design is promising where the self-assembly and emission in the aggregated state can be preserved. The nonsymmetric design lowers the phase-transition temperatures.The presence of an amide bond helps to stabilize columnar packing over a long range because of its polarity and intermolecular hydrogen bonding in addition to promoting organogelation.
- Pathak, Suraj Kumar,Pradhan, Balaram,Gupta, Monika,Pal, Santanu Kumar,Sudhakar, Achalkumar Ammathnadu
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p. 9301 - 9312
(2016/10/06)
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- A phosphonic acid appended naphthalene diimide motif for self-assembly into tunable nanostructures through molecular recognition with arginine in water
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A naphthalene diimide motif bearing phosphonic acid functionalities has been found to be self-assembled with l- and d-arginine through chirality induced molecular recognitions and leads to the formation of micrometre long nanobelts and spherical aggregates at pH 9 in water, respectively.
- Nandre, Kamalakar P.,Bhosale, Sheshanath V.,Rama Krishna,Gupta, Akhil,Bhosale, Sidhanath V.
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supporting information
p. 5444 - 5446
(2013/06/27)
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- Caged CO2 for the Direct Observation of CO2-Consuming Reactions
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CO2-consuming reactions, in particular carboxylations, play important roles in technical processes and in nature. Their kinetic behavior and the reaction mechanisms of carboxylating enzymes are difficult to study because CO2 is inconvenient to handle as a gas, exists in equilibrium with bicarbonate in aqueous solution, and typically yields products that show no significant spectroscopic differences from the reactants in the UV/Vis range. Here we demonstrate the utility of 3-nitrophenylacetic acid and related compounds (caged CO2) in conjunction with infrared spectroscopy as widely applicable tools for the investigation of such reactions, permitting convenient measurement of the kinetics of CO2 consumption. The use of isotopically labeled caged CO2 provides a tool for the assignment of infrared absorption bands, thus aiding insight into reaction intermediates and mechanisms.
- Lommel, Katharina,Sch?fer, Gabriela,Grenader, Konstantin,Ruland, Christoph,Terfort, Andreas,M?ntele, Werner,Wille, Georg
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p. 372 - 380
(2013/08/24)
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- Organogelators derived from [3.3]metacyclophane skeleton with a urea unit
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Dithia[3.3]metacyclophanes with a urea unit having long alkyl chains have been prepared. It has been found out that some of them give stable organogels in some solvents, and their gelating ability depends on structural properties of both aromatic componen
- Tsuge, Akihiko,Matsushita, Ryuichiro,Sakura, Katsuhiko,Moriguchi, Tetsuji,Araki, Koji
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body text
p. 485 - 487
(2012/07/17)
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- Efficient synthetic access to cationic dendrons and their application for ZnO nanoparticles surface functionalization: New building blocks for dye-sensitized solar cells
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A new concept for the efficient synthesis of cationic dendrons, 4-tert-butyl-1-(3-(3,4-dihydroxybenzamido)benzyl)pyridinium bromide (17), 1,1′-(5-(3,4-dihydroxybenzamido)-1,3-phenylene)bis(methylene) bis(4-tert-butylpyridinium) bromide (18), N1,N7-bis(3-(
- Gnichwitz, Jan-Frederik,Marczak, Renata,Werner, Fabian,Lang, Nina,Jux, Norbert,Guldi, Dirk M.,Peukert, Wolfgang,Hirsch, Andreas
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scheme or table
p. 17910 - 17920
(2011/03/16)
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- QUINOLINE DERIVATIVES
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The invention concerns quinoline derivatives of Formula I or a pharmaceutically-acceptable salt thereof, wherein each of X1, p, R1, q, R2, R3, R4, R5Ring A, r and R6 has any of the meanings defined hereinbefore in the description; processes for their preparation, pharmaceutical compositions containing them and their use in the manufacture of a medicament for use in the treatment of cell proliferative disorders.
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Page/Page column 41
(2009/04/24)
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- Synthesis and spectroscopic studies on azo-dye derivatives of polymetallic lanthanide complexes: Using diazotization to link metal complexes together
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(Graph Presented) Heteronuclear tetrametallic lanthanide complexes have been synthesized from stable complexes by diazotization and azo-compound formation. Luminescence spectroscopy has been used to show that the complexes used as building blocks are stab
- Placidi, Matteo P.,Villaraza, Aaron Joseph L.,Natrajan, Louise S.,Sykes, Daniel,Kenwright, Alan M.,Faulkner, Stephen
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supporting information; experimental part
p. 9916 - 9917
(2009/12/06)
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- Synthesis of an azacrown template for phosphatidylinositol-4,5-bis(phosphate) recognition
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An azacrown system has been developed for selective membrane binding of phosphatidylinositol-4,5-bis(phosphate) recognition. Neutral and cationic forms of the metacyclophane macrocycles have been synthesized by divergent routes in acceptable yields. Such
- Gray Jr., Charles W.,Barry, Kathleen,Lindberg, Eric J.,Houston, Todd A.
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p. 2683 - 2686
(2008/02/03)
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- QUINAZOLINE DERIVATIVES
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The invention concerns quinazoline derivatives of Formula (I) or a pharmaceutically-acceptable salt thereof, wherein each of X1, p, R1, q, R2, R3, R4, R5, Ring A, r and R6 has any of the meanings defined hereinbefore in the description; processes for their preparation, pharmaceutical compositions containing them and their use in the manufacture of a medicament for use in the treatment of cell proliferative disorders.
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Page/Page column 112
(2008/06/13)
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- NAPHTHYRIDINE DERIVATIVES AS ANTI-CANCER AGENTS
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The invention concerns naphthyridine derivatives of Formula (I): or a pharmaceutically-acceptable salt thereof, wherein each of X1, p, R1, G1, G2, q, R2, R3, R4, R5, Ring A, r and R6 has any of the meanings defined hereinbefore in the description; pharmaceutical compositions containing them and their use in the treatment of cell proliferative disorders or disease states associated with angiogenesis and/or vascular permeability.
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Page/Page column 104
(2010/11/28)
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- QUINOLINE DERIVATIVES
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The invention concerns quinoline derivatives of Formula (I): or a pharmaceutically-acceptable salt thereof, wherein each of X1, p, R1, q, R2, R3, R4, R5, Ring A, r and R6 has any of the meanings defined hereinbefore in the description; processes for their preparation, pharmaceutical compositions containing them and their use in the manufacture of a medicament for use in the treatment of cell proliferative disorders.
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Page/Page column 143
(2008/06/13)
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- QUINOLINE DERIVATIVES FOR TREATING CANCER
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The invention concerns quinoline derivatives of Formula (I) or a pharmaceutically-acceptable salt thereof, wherein each of X1, p, R1, q, R2, R3, R4, R5, Ring A, r and R6 has any of the meanings defined hereinbefore in the description; processes for their preparation, pharmaceutical compositions containing them and their use in the manufacture of a medicament for use in the treatment of cell proliferative disorders.
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Page/Page column 110
(2008/06/13)
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- Arginine- and lysine-specific polymers for protein recognition and immobilization
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Free radical polymerization of methacrylamide-based bisphosphonates turns weak arginine binders into powerful polymeric protein receptors. Dansyl-labeled homo- and copolymers with excellent water solubility are accessible through a simple copolymerization protocol. Modeling studies point to a striking structural difference between the stiff rodlike densely packed homopolymer 1 and the flexible copolymer 2 with spatially separated bisphosphonate units. Fluorescence titrations in buffered aqueous solution (pH = 7.0) confirm the superior affinity of the homopolymer toward oligoarginine peptides reaching nanomolar KD values for the Tat peptide. Basic proteins are bound almost equally well by 1 and 2 with micromolar affinities, with the latter producing much more soluble complexes. The Arg selectivity of the monomer is transferred to the polymer, which binds Arg-rich proteins 1 order of magnitude tighter than lysine-rich pendants of comparable pl, size, and (Arg/Lys vs Glu/Asp) ratio. Noncovalent deposition of both polymers on glass substrates via polyethyleneimine layers results in new materials suitable for peptide and protein immobilization. RlfS measurements allow calculation of association constants Ka as well as dissociation kinetics kD. They generally confirm the trends already found in free solution. Close inspection of electrostatic potential surfaces suggest that basic domains favor protein binding on the flat surface. The high specificity of the bisphosphonate polymers toward basic proteins is demonstrated by comparison with polyvinyl sulfate, which has almost no effect in RlfS experiments. Thus, copolymerization of few different comonomer units without cross-linking enables surface recognition of basic proteins in free solution as well as their effective immobilization on surfaces.
- Renner, Christian,Piehler, Jacob,Schrader, Thomas
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p. 620 - 628
(2007/10/03)
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- QUINAZOLINE DERIVATIVES
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The invention concerns quinazoline derivatives of Formula (I) or a pharmaceutically-acceptable salt, solvate or pro-drug thereof, wherein each of X1, p, R1, q, R2, R3, R4, R5, Ring A, r and R6 has any of the meanings defined hereinbefore in the description; processes for their preparation, pharmaceutical compositions containing them and their use in the manufacture of a medicament for use in the treatment of cell proliferative disorders or in the treatment of disease states associated with angiogenesis and/or vascular permeability.
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(2008/06/13)
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- QUINOLINE DERIVATIVES
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The invention concerns quinoline derivatives of Formula (I) or a pharmaceutically-acceptable salt, solvate or pro-drug thereof, wherein each of p, R1, q, R2, R3, R4, R5, Ring A, r and R6 has any of the meanings defined in the description; processes for their preparation, pharmaceutical compositions containing them and their use in the manufacture of a medicament for use in the treatment of cell proliferative disorders or in the treatment of disease states associated with angiogenesis and/or vascular permeability.
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(2008/06/13)
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- Participation of benzene hydrogen bonding upon anion binding
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(Chemical Equation Presented) A m-xylene-bridged imidazolium receptor, 1, has been designed and synthesized. The receptor 1 utilizes two imidazole (C-H)+...anion hydrogen bonds and one benzene hydrogen...anion hydrogen bond. The major driving force of complexation between the receptor 1 and anions comes from two imidazole (C-H) +...anion hydrogen bonds. However, both NMR experiments and ab initio calculations show that the benzene hydrogen attracts the anion guests, clearly indicating benzene (C-H)...anion hydrogen bonding.
- In, Sungjae,Seung, Joo Cho,Kyu, Hwan Lee,Kang, Jongmin
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p. 3993 - 3996
(2007/10/03)
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- Synthesis and evaluation of bifunctional chelating agents derived from bis(2-aminophenylthio)alkane for radioimaging with 99mTc
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Novel bifunctional chelating agents bearing an aromatic rigid backbone have been synthesized and characterized on the basis of spectroscopic techniques. These macrocyclic multidentate chelating agents were conjugated with monoclonal antibody which forms stable complexes with 99mTc with high radiochemical purity.
- Chhikara, Bhupender S.,Kumar, Nitin,Tandon, Vibha,Mishra, Anil K.
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p. 4713 - 4720
(2007/10/03)
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- An expedient approach to internally functionalized chiral dendrimers: Synthesis of a dendritic molecule incorporating furanoside skeleton
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In an approach to chiral dendritic molecules, a dendrimer incorporating pentose units in the interior and hexose units in the periphery is built up on a 1, 3, 5-trisubstituted aromatic core by using 1,2:5,6-diisopropylidene glucose as the carbohydrate precursor and a 3, 5-disubstituted aromatic unit as the branching block. The carbohydrate moiety also provides internal functionalities in the form of hemiacetal moiety of the furanoside ring.
- Ghorai, Subir,Bhattacharjya, Anup,Basak, Ajoy,Mitra, Abhijit,Williamson, R. Thomas
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p. 617 - 620
(2007/10/03)
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- Optimization of a synthetic arginine receptor. Systematic tuning of noncovalent interactions
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The simple arginine binder 1 could be optimized by strengthening π-cation as well as electrostatic interactions. Electron-donating or -withdrawing substituents in the 5-position provide experimental evidence for π-cation interactions, because binding energies increase by up to 0.6 kcal/mol due to a single benzene-guanidinium interaction. Even more effective is the introduction of a third phosphonate functionality at the correct distance, so that the guanidinium cation is recognized by optimal electrostatic and hydrogen bond interactions. Monte Carlo simulations and NOESY experiments confirm the expected complex geometries. The optimized host molecule 8 binds arginine half an order of magnitude more efficiently than the parent molecule.
- Rensing,Arendt,Springer,Grawe,Schrader
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p. 5814 - 5821
(2007/10/03)
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- Structure-activity relationships of pyridoxal phosphate derivatives as potent and selective antagonists of P2X1 receptors
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Novel analogues of the P2 receptor antagonist pyridoxal-5′-phosphate 6-azophenyl-2′,5′ disulfonate (2) were synthesized and studied as antagonists in functional assays at recombinant rat P2X1, P2X2, and P2X3 receptors expressed in Xenopus oocytes (ion flux stimulation) and at turkey erythrocyte P2Y1 receptors (phospholipase C activation). Selected compounds were also evaluated as antagonists of ion flux and the opening of a large pore at the recombinant human P2X7 receptor. Modifications were made in the 4-aldehyde and 5′-phosphate groups of the pyridoxal moiety: i.e. a CH2OH group at the 4-position in pyridoxine was either condensed as a cyclic phosphate or phosphorylated separately to form a bisphosphate, which reduced potency at P2 receptors. 5-Methylphosphonate substitution, anticipated to increase stability to hydrolysis, preserved P2 receptor potency. At the 6-position, halo, carboxylate, sulfonate, and phosphonate variations made on the phenylazo ring modulated potency at P2 receptors. The p-carboxyphenylazo analogue, 4, of phosphate 2 displayed an IC50 value of 9 nM at recombinant P2X1 receptors and was 1300-, 16-, and > 10000-fold selective for P2X1 versus P2X2, P2X3, and P2Y1 subtypes, respectively. The corresponding 5-methylphosphonate was equipotent at P2X1 receptors. The 5-methylphosphonate analogue containing a 6-[3,5-bis(methylphosphonate)]phenylazo moiety, 9, had IC50 values of 11 and 25 nM at recombinant P2X1 and P2X3 receptors, respectively. The analogue containing a phenylazo 4-phosphonate group, 11, was also very potent at both P2X1 and P2X3 receptors. However, the corresponding 2,5-disulfonate analogue, 10, was 28-fold selective for P2X1 versus P2X3 receptors. None of the analogues were more potent at P2X7 and P2Y1 receptors than 2, which acted in the micromolar range at these two subtypes.
- Kim,Brown,Harden,Boyer,Dubyak,King,Burnstock,Jacobson
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p. 340 - 349
(2007/10/03)
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- Acyclic analogues of deoxyadenosine 3',5'-bisphosphates as P2Y1 receptor antagonists
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P2Y1 receptors are activated by ADP and occur on endothelial cells, smooth muscle, epithelial cells, lungs, pancreas, platelets, and in the central nervous system. With the aid of molecular modeling, we have designed nucleotide analogues that act as selective antagonists at this subtype. The present study has tested the hypothesis that acyclic modifications of the ribose ring, proven highly successful for nucleoside antiviral agents such as gancyclovir, are generalizable to P2Y receptor ligands. Specifically, the binding site of the P2Y1 receptor was found to be sufficiently accommodating to allow the substitution of the ribose group with acyclic aliphatic and aromatic chains attached to the 9-position of adenine. Three groups of adenine derivatives having diverse side-chain structures, each containing two symmetrical phosphate or phosphonate groups, were prepared. Biological activity was demonstrated by the ability of the acyclic derivatives to act as agonists or antagonists in the stimulation of phospholipase C in turkey erythrocyte membranes. An acyclic N6-methyladenine derivative, 2-[2-(6- methylaminopurin-9-yl)-ethyl]-propane-1,3-bisoxy(diammoniumphosphate) (10), containing an isopentyl bisphosphate moiety, was a full antagonist at the P2Y1 receptor with an IC50 value of 1.60 μM. The corresponding 2-Cl derivative (11) was even more potent with an IC50 value of 0.84 μM. Homologation of the ethylene group at the 9-position to 3-5 methylene units or inclusion of cis- or trans-olefinic groups greatly reduced antagonist potency at the P2Y1 receptor. Analogues containing a diethanolamine amide group and an aryl di(methylphosphonate) were both less potent than 10 as antagonists, with IC50 values of 14 and 16 μM, respectively, and no agonist activity was observed for these analogues. Thus, the ribose moiety is clearly not essential for recognition by the turkey P2Y1 receptor, although a cyclic structure appears to be important for receptor activation, and the acyclic approach to the design of P2 receptor antagonists is valid.
- Kim, Yong-Chul,Gallo-Rodriguez, Carola,Jang, Soo-Yeon,Nandanan, Erathodiyil,Adams, Mary,Harden, T. Kendall,Boyer, José L.,Jacobson, Kenneth A.
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p. 746 - 755
(2007/10/03)
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- Dendritic amplifier molecules having multiple terminal active groups stemming from a benzyl core group
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Dendritic derivatives of 3,5-bis(aminomethyl)benzene and aminomethyl benzene core groups are disclosed. In each derivative, termed an "amplifier" because the dendritic structure on each molecule terminates with multiple termini to each of which an "active
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- Reversible dioxygen binding and aromatic hydroxylation in O2-reactions with substituted xylyl dinuclear copper(I) complexes: Syntheses and low-temperature kinetic/thermodynamic and spectroscopic investigations of a copper monooxygenase model system
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The binding and subsequent reactivity of dioxygen (O2) upon binding to copper ion centers is of fundamental interest in chemical and biological processes. We provide here a detailed account of the reaction of O2 with dicopper(I) complexes, involving O2-reversible binding, followed by the stoichiometric aromatic hydroxylation of the ligand. Thus, tricoordinated dicopper(I) complexes [Cu2(R-XYL)]2+ (R = H, MeO, t-Bu, F, CN, NO2; 1a-f) possess dinucleating meta-substituted xylylene ligands with two chelating tridentate bis[2-(2-pyridyl)ethyl]amine (PY2) moieties and a 5-R substituent. Upon reaction with O2, dioxygen adducts [Cu2(R-XYL)(O2)]2+ (2a,c-f) form reversibly, and these subsequently yield 2-xylylene-hydroxylated products [Cu2(R-XYL-O-)(OH)]2+ (3a-f), which are phenoxo- and hydroxo-bridged copper(II) complexes. The products 3 have been characterized via the X-ray structure of the parent complex 3a, and by their UV-visible, infrared, and room-temperature magnetic properties. Incorporation of the O-atom from dioxygen into the phenolic products has been proven by isotopic labeling experiments, except in the case of 3f, where workup results in an exchange reaction causing loss of the oxygen label. In reactions of O2 with 1 in dichloromethane at room temperature, 10-25% yields of unhydroxylated complexes [Cu2(R-XYL)(OH)]3+ (5) are obtained. A stopped-flow kinetics study of O2 reactions of 1 in CH2Cl2 demonstrates that [Cu2(R-XYL)(O2)]2+ (2a,c-f) complexes form reversibly, proceeding via the reaction 1 + O2 ? 2 (K1 = k1/k-1); this is followed by the irreversible reaction 2 → 3 (k2). Analysis of temperature-dependent data which is accompanied by spectrophotometric monitoring yields both kinetic and thermodynamic parameters for R = H, t-Bu, F, and NO2. Dioxygen binding to 1 occurs in a single observable step with low activation enthalpies (6-29 kJ mol-1) and large, negative activation entropies (-66 to -167 J K-1 mol-1). The remote R-substituent has a significant effect on the dioxygen-binding process and this is explained in terms of its multistep nature. Strong binding (K1) occurs at low temperature (e.g. -80 °C), and thermodynamic parameters indicate a large enthalpic contribution (ΔH° = -52 to -74 kJ mol-1), but room-temperature stabilities of the dioxygen adducts are precluded by very large unfavorable entropies (ΔS° = -156 to -250 J K-1 mol-1). Electron-releasing R-substituents cause a small but significant enhancement of k2, the hydroxylation step, consistent with a mechanism involving electrophilic attack of the Cu2O2 intermediate 2 upon the xylyl aromatic ring. The influence of substituent upon the various rates of reaction allows for stabilization (~minutes), allowing the bench-top observation of 2d,e,f using UV-visible spectroscopy at -80 °C. "Vacuum-cycling" experiments can be carried out on 1f/2f, i.e., the repetitive oxygenation of 1f at -80 °C, followed by removal of O2 from 2f by application of a vacuum. Dicopper(I) complexes I have been characterized by 1H and 13C NMR spectroscopy, along with analogs in which an ethyl group has been placed in the 5-position of the pyridyl ring donor groups, i.e., [CuI2(R-XYL-(5-Et-PY))]2+ (1g, R = H; 1h, R = NO2). Variable-temperature 1H NMR spectroscopic studies provide clues as to why [Cu2(MeO-XYL)]2+ (1b) does not oxygenate (i.e., bind O2 and/or hydroxylate) at low temperature, the conclusion being that significant interactions of the coordinately unsaturated copper(I) ion(s) with the chelated methoxybenzene group result in conformations unsuitable for O2-reactivity. The biological implications of the biomimetic chemistry described here are discussed, as a system effecting oxidative C-H functionalization using O2 under mild conditions and as a monooxygenase model system for tyrosinase (phenol o-monooxygenase), with its dinuclear active site.
- Karlin, Kenneth D.,Nasir, M. Sarwar,Cohen, Brett I.,Cruse, Richard W.,Kaderli, Susan,Zuberbühler, Andreas D.
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p. 1324 - 1336
(2007/10/02)
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- Electron Donor-Acceptor Compounds, XXXVIII. Electron Donor-Acceptor Metacyclophanes: Synthesis, Structure, and Charge-Transfer Spectra
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Donor-acceptor metacyclophanes 1-4 as well as 24 were synthesized via the correspondingly substituted 2,11-dithiametacyclophanes 8, 13, and 25 and their disulfone derivatives.The anti-compound 1 and the syn-isomer 2 were isolated and characterized.The attempt of the analogous synthesis of 5/6 via 21 and 22 failed since with loss of the intraanular substituents and by transanular C-C formation the tetrahydropyrene derivative 23 was formed.For spectroscopic comparison 27 was prepared via 28.- X-Ray structure analyses of 21, 24, and 25 were performed.The molecular structures of these compounds are discussed under the aspects of sterical strain and donor-acceptor overlap.The structure analyses confirm the assignment to the syn- and anti-series as derived from 1H NMR.- Absorption spectra of 1, 2, 3, and 24 were measured; especially the surprising absorption behaviour of the isomers 1 and 2 with very different donor-acceptor overlap was of interest.Determination of the solvent dependence of fluorescence made sure that the absorptions dealt with are indeed charge-transfer transitions.
- Staab, Heinz A.,Schanne, Lothar,Krieger, Claus,Taglieber, Volker
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p. 1204 - 1229
(2007/10/02)
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