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61.
Anion‐Directed Copper(II) Metallocages,Coordination Chain,and Complex Double Salt: Structures,Magnetic Properties,EPR Spectra,and Density Functional Study 下载免费PDF全文
Prof. Dr. Jing‐Yun Wu Ming‐Shiou Zhong Prof. Dr. Ming‐Hsi Chiang Dr. Dibyendu Bhattacharya Yen‐Wei Lee Prof. Dr. Long‐Li Lai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(21):7238-7247
A series of CuII metallo‐assemblies showing anion‐directed structural variations, including five metallocages [(Gn?)?{Cu2(Hdpma)4}](8?n)+(A?)8?n (Gn?=NO3?, ClO4?, SiF62?, BF4?, SO42?; A?=NO3?, ClO4?, BF4?, CH3SO4?; Hdpma=bis(3‐pyridylmethyl)ammonium cation), a complex double salt, namely, (H3dpma)4(CuCl4)5Cl2, and a coordination chain, namely, [Cu2(dpma)(OAc)4], are reported. The influence of the anion can be explained by its coordinating ability, the affinity of which for the CuII center interferes significantly with metallocage formation, and its shape, which offers host–guest recognition ability to engage in weak metal–anion coordination and hydrogen bonding to the organic ligand, which are responsible for metallocage templation. EPR studies of these metallocages in the powder phase at room temperature and 77 K showed a trend of the g values (g||>2.10>g⊥>2.00) indicating a ‐based ground state with square‐pyramidal geometry for the CuII centers. The magnetism of these metallocages can be interpreted as the result of a combination of relatively small magnetic coupling integrals and a substantial contribution of temperature‐independent paramagnetism (TIP). The weak magnetic interaction is corroborated by the results of DFT calculations and the EPR spectra. Availability of the low‐lying state for spin population was confirmed by a magnetization study, which revealed a magnetic moment approaching 2Nβ, which would explain the presence of the larger TIP term. 相似文献
62.
Madhuri Mukhopadhyay Debi Banerjee Aleksander Koll Aleksander Filarowski Samaresh Mukherjee 《Chemical physics letters》2006,420(4-6):316-320
The effect of neutral, cationic and anionic micellar environments on the ground and excited state proton transfer reactions of salicylidine-3,4,7-methyl amine (SMA) in water has been studied by steady state and time resolved fluorescence spectroscopy. In the ground state, the formation of the primary form of SMA is enhanced at the expense of the zwitterionic species due to micellization. In the excited state, anion formation decreases both in the presence of Triton-X and cetyl trimethyl ammonium bromide (CTAB). However, in the presence of sodium dodecyl sulphate (SDS), the anionic emission increases after reaching a certain micellar concentration. The lifetime of the anion is significantly reduced in CTAB compared to that in the bulk water and also in the presence of Triton-X. It is proposed that the destabilization and modification of SMA anion occurs due to the different electrostatic environments produced by micellization. 相似文献
63.
We report the first experimental and theoretical study of gas phase excited electronic state decomposition of a furazan based, high nitrogen content energetic material, 3,3'-diamino-4,4'-azoxyfurazan (DAAF), and its model systems, diaminofurazan (DAF) and furazan (C2H2N2O). DAAF has received major attention as an insensitive high energy explosive; however, the mechanism and dynamics of the decomposition of this material are not clear yet. In order to understand the initial decomposition mechanism of DAAF and those of its model systems, nanosecond energy resolved and femtosecond time resolved spectroscopies and complete active space self-consistent field (CASSCF) calculations have been employed to investigate the excited electronic state decomposition of these materials. The NO molecule is observed as an initial decomposition product from DAAF and its model systems at three UV excitation wavelengths (226, 236, and 248 nm) with a pulse duration of 8 ns. Energies of the three excitation wavelengths coincide with the (0-0), (0-1), and (0-2) vibronic bands of the NO A 2Sigma+<--X 2Pi electronic transition, respectively. A unique excitation wavelength independent dissociation channel is observed for DAAF, which generates the NO product with a rotationally cold (20 K) and a vibrationally hot (1265 K) distribution. On the contrary, excitation wavelength dependent dissociation channels are observed for the model systems, which generate the NO product with both rotationally cold and hot distributions depending on the excitation wavelengths. Potential energy surface calculations at the CASSCF level of theory illustrates that two conical intersections between the excited and ground electronic states are involved in two different excitation wavelength dependent dissociation channels for the model systems. Femtosecond pump-probe experiments at 226 nm reveal that the NO molecule is still the main observed decomposition product from the materials of interest and that the formation dynamics of the NO product is faster than 180 fs. Two additional fragments are observed from furazan with mass of 40 amu (C2H2N) and 28 amu (CH2N) employing femtosecond laser ionization. This observation suggests a five-membered heterocyclic furazan ring opening mechanism with rupture of a CN and a NO bond, yielding NO as a major decomposition product. NH2 is not observed as a secondary decomposition product of DAAF and DAF. 相似文献
64.
Xiao-Tao Chen Bishan Zhou Samit K. Bhattacharya Clare E. Gutteridge Thomas R. R. Pettus Samuel J. Danishefsky 《Angewandte Chemie (International ed. in English)》1998,37(6):789-792
An “sp 2 –sp 3 Stille coupling” of the vinyl triflate 1 and the stannyl compound 2 is a key step toward the completion of the total synthesis of eleutherobin, a natural product exhibiting taxol-like cytotoxic activity. 相似文献
65.
Bagkar N Choudhury S Bhattacharya S Yakhmi JV 《The journal of physical chemistry. B》2008,112(20):6467-6472
We report here the synthesis of nickel hexacyanoferrate (NiHCF) crystals using calf thymus DNA (CT-DNA) as a template. The double-stranded CT-DNA has been used as a template to self-assemble NiHCF crystals and to produce aggregates having different morphologies at different temperatures. The guided self-assembly behavior of DNA was studied at different temperatures by scanning electron microscopy. The cube-shaped crystals of NiHCF with an average diameter of 400 nm are observed along the DNA framework at room temperature; however, at higher temperatures, the morphology of NiHCF changed from open tubular to dendrimer. The intermediate temperatures show long chains (up to many micrometers) and spherical structures of NiHCF crystals. The micrometer long DNA template plays a key role in the formation of extended arrays of NiHCF crystals, suggesting that the templating action is retained even at the higher temperatures. 相似文献
66.
Parameterization of peptide 13C carbonyl chemical shielding anisotropy in molecular dynamics simulations. 总被引:1,自引:0,他引:1
Daniel M Jordan K Maria Mills Ioan Andricioaei Akash Bhattacharya Kim Palmo Erik R P Zuiderweg 《Chemphyschem》2007,8(9):1375-1385
NMR chemical shielding anisotropy (CSA) relaxation is an important tool in the study of dynamical processes in proteins and nucleic acids in solution. Herein, we investigate how dynamical variations in local geometry affect the chemical shielding anisotropy relaxation of the carbonyl carbon nucleus, using the following protocol: 1) Using density functional theory, the carbonyl (13)C' CSA is computed for 103 conformations of the model peptide group N-methylacetamide (NMA). 2) The variations in computed (13)C' CSA parameters are fitted against quadratic hypersurfaces containing cross terms between the variables. 3) The predictive quality of the CSA hypersurfaces is validated by comparing the predicted and de novo calculated (13)C' CSAs for 20 molecular dynamics snapshots. 4) The CSA fluctuations and their autocorrelation and cross correlation functions due to bond-length and bond-angle distortions are predicted for a chemistry Harvard molecular mechanics (CHARMM) molecular dynamics trajectory of Ca(2+)-saturated calmodulin and GB3 from the hypersurfaces, as well as for a molecular dynamics (MD) simulation of an NMA trimer using a quantum mechanically correct forcefield. We find that the fluctuations can be represented by a 0.93 scaling factor of the CSA tensor for both R(1) and R(2) relaxations for residues in helix, coil, and sheet alike. This result is important, as it establishes that (13)C' relaxation is a valid tool for measurement of interesting dynamical events in proteins. 相似文献
67.
Sarmistha Das Samirgopal Bhattacharya Rupendra Nath Banerjee Debabrata Banerjea 《Transition Metal Chemistry》1982,7(5):249-252
Summary The title complex aquates in acid media, first to [Co(mal)-(H2O)2(en)]+ (1) (Step 1) and subsequently to [Co(H2O)4(en)]3+
(2) (Step 2). Complex species (1) has been separated and characterised in solution. While Step 1 involves only a second-order acid catalysed path, Step 2 involves both a first-order acid independent path and a second-order acid catalysed path. The rate constants and activation parameters evaluated for these reaction paths have been compared with those for similar carboxylato-cobalt(III) complexes. This, together with an observed isokinetic relation, indicates that the rate-determining step involves opening of the unprotonated (in the spontaneous acid independent path) or the protonated (for the acid catalysed path) chelate ring of the malonate ligand and insignificant solvation of the central metal ion. 相似文献
68.
Rama Acharyya Shie-Ming Peng Ren-Zhang Wang Samaresh Bhattacharya 《Journal of organometallic chemistry》2005,690(17):3908-3917
Reaction of 2-(2′,6′-dimethylphenylazo)-4-methylphenol with [Ir(PPh3)3Cl] in refluxing ethanol in the presence of a base (NEt3) affords an organoiridium complex 5, where the 2-(2′,6′-dimethylphenylazo)-4-methylphenol is coordinated to iridium, via C-H activation of a methyl group, as a dianionic tridentate C,N,O-donor. Two triphenylphosphines and a hydride are also coordinated to the metal center. A similar reaction carried out in toluene affords complex 5 along with a similar complex 7, where a chloride is coordinated to iridium instead of the hydride. Reaction of 2-(2′-methylphenylazo)-4-methylphenol with [Ir(PPh3)3Cl] in refluxing ethanol in the presence of a base (NEt3) affords an organoiridium complex 12, where the 2-(2′-methylphenylazo)-4-methylphenol is coordinated to iridium, via C-H activation at the ortho position of the phenyl group in the 2′-methylphenylazo fragment, as a dianionic tridentate C,N,O-donor. Two triphenylphosphines and a hydride are also coordinated to the metal center. A similar reaction carried out in toluene affords a complex 12 along with a similar complex 13, where a chloride is coordinated to iridium instead of the hydride. Structures of complexes 5, 12 and 13 have been determined by X-ray crystallography. In all these complexes, the two triphenylphosphines are trans. All these complexes show intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows an Ir(III)-Ir(IV) oxidation within 0.60-0.73 V vs. SCE, followed by an oxidation of the coordinated 2-(arylazo)phenolate ligand within 1.08-1.39 V vs. SCE. A reduction of the coordinated 2-(arylazo)phenolate ligand is observed within −1.10 to −1.26 V vs. SCE. 相似文献
69.
Samaresh Ghosh 《Supramolecular chemistry》2013,25(5):409-414
A novel hyperbranched polyesteramine (PEA) architecture 1 was found to display light-harvesting properties by hosting anthracene-9-carboxylic acid guest 3. The light-harvesting ability has been studied by means of fluorescence spectroscopy. The binding behaviour has also been described by FT-IR and 1H NMR spectroscopic methods. Hyperbranched host 1 also acts as the photon-harvesting chemosensor of the anthracenyl guest over the benzoic acid guest. Furthermore, the host loaded with the anthracenyl guest also exhibited ‘ON–OFF’ switching on protonation of amine sub-units with HCl, thereby making it of potential use as a pH-assisted photon-harvesting material. 相似文献
70.
Amal Halder Sandip K. Nayak Subrata Chattopadhyay Sumanta Bhattacharya 《Journal of solution chemistry》2012,41(2):223-240
The present article reports the host-guest complexation of a calix[4]arene derivative, namely 4-iso-propyl-calix[4]arene (1), with fullerenes (both C60 and C70) in toluene and benzonitrile solutions. It is observed that the charge-transfer (CT) absorption bands are located in the
ground state for the C60 and C70 complexes of 1. By utilizing the CT absorption bands, various important physicochemical parameters like the oscillator strength, resonance
energy, transition dipole moment, electronic coupling element and solvent reorganization energies have been estimated for
the C60-1 and C70-1 complexes. The CT transition energy is very helpful for determining the vertical ionization potential of 1 in solution. Jobs method of continuous variation was used to establish 1:1 stoichiometry for the fullerene complexes of 1. The most fascinating feature of the present study is that 1 binds C70 preferentially compared to C60 as obtained from binding constant (K) data. The effect of solvent on the complexation of fullerenes (C60 and C70) with 1 is clearly observed from the trend in the K values: in toluene and whereas in benzonitrile, and . Molecular mechanics force field (MMMF) calculations reveal fascinating features regarding the binding pattern of fullerenes
towards 1 in vacuo in terms of enthalpy of formation. MMMF calculations establish that during C70-1 complexation, C70 is directed in an end-on manner rather than the traditional side-on pattern. 相似文献