The metathetical reactions between SnBr4 and Li2[E'C(PPh2E)2] in toluene produce the homoleptic tin(IV) complexes Sn[E′C(PPh2E)2]2 [E = E′ = S ( 1b ); E = S, E′ = Se ( 1c )], which were isolated as red crystals and structurally characterized by X‐ray crystallography. The metrical parameters of these octahedral complexes are compared with those of the all‐selenium analog Sn[E′C(PPh2E)2]2 (E = E′ = Se, 1a ), which was prepared previously by a different route. 相似文献
A combined synchrotron X‐ray and density functional theory (DFT) study on the structure of a Jäger‐type N2O2 chelate complex was carried out. The ethoxy‐substituted bis(3‐oxo‐enaminato)cobalt(II) complex ( 1 ) was an original sample from the laboratory of the late Professor Ernst‐G. Jäger (University of Jena, Germany). Single‐crystal X‐ray analysis revealed essentially flat molecules of 1 , which are unsolvated and coordinatively unsaturated. The DFT calculations on the isolated molecule predict a planar structure for the non‐hydrogen atoms, which is a local minimum on the energy surface. The crystal packing is achieved through off‐set stacking (staircase arrangement), resulting in a herringbone pattern in the space group P212121. The structure of 1 is compared to known structures of related bis(3‐oxo‐enaminato)cobalt(II) complexes ( 2 – 4 ). Original bulk material of 1 was investigated by scanning electron microscopy (SEM), powder X‐ray diffraction (PXRD), melting point determination, and infrared (IR) spectroscopy. 相似文献
In the present work a modular pathway towards the synthesis of a new versatile MRI contrast agent is reported and its physico-chemical properties are described. Two different functional groups were attached on two arms of the gadolinium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) in order to get a platform able to bind one probe designed to target specific biological marker and a fluorescent molecule likely to be used for optical imaging. The nuclear magnetic relaxation dispersion (NMRD) profile, the oxygen-17 relaxometric NMR study and stability assessment versus transmetalation of the Gd-complex show that this new contrast agent has a relaxivity and transmetalation stability similar to Gd–DOTA. 相似文献
<正>1 General methods Unless otherwise noted, all reactions and manipulations involving air- or moisture-sensitive compounds were performed using standard Schlenk techniques or in a glovebox. All solvents were purified and dried using standard procedures. Melting points were measured on a RY-I apparatus and uncorrected. 1H, 13 C, 31 P and 19 F NMR spectra were recorded on Varian Mercury 300 or 400 MHz spectrometers. Chemical shifts(δ values) were reported in ppm downfield from internal TMS(1H NMR), CDCl3(13C NMR), external 85% H3PO4(31P NMR), and external CF3CO2H(19F NMR), respectively. Optical rotations were determined using a Perkin Elmer 341 MC polarimeter. The IR spectra were measured on a BRUKER TENSOR 27 相似文献
The electronic properties of four divinylanthracene‐bridged diruthenium carbonyl complexes [{RuCl(CO)(PMe3)3}2(μ? CH?CHArCH?CH)] (Ar=9,10‐anthracene ( 1 ), 1,5‐anthracene ( 2 ), 2,6‐anthracene ( 3 ), 1,8‐anthracene ( 4 )) obtained by molecular spectroscopic methods (IR, UV/Vis/near‐IR, and EPR spectroscopy) and DFT calculations are reported. IR spectroelectrochemical studies have revealed that these complexes are first oxidized at the noninnocent bridging ligand, which is in line with the very small ν(C?O) wavenumber shift that accompanies this process and also supported by DFT calculations. Because of poor conjugation in complex 1 , except oxidized 1+ , the electronic absorption spectra of complexes 2+ , 3+ , and 4+ all display the characteristic near‐IR band envelopes that have been deconvoluted into three Gaussian sub‐bands. Two of the sub‐bands belong mainly to metal‐to‐ligand charge‐transfer (MLCT) transitions according to results from time‐dependent DFT calculations. EPR spectroscopy of chemically generated 1+ – 4+ proves largely ligand‐centered spin density, again in accordance with IR spectra and DFT calculations results. 相似文献
3,6‐Connected cyclohexadienes as precursors for polyphenylenes are synthesized and characterized by mass spectrometry and NMR spectroscopy. Pure fractions of trimers, hexamers, and nonamers are collected after separation of the product mixture by recycling GPC. The anticipated formation of rigid linear structures, due to the trans‐configuration of the monomeric units, is supported by density functional theory and experimentally confirmed by dynamic light scattering from dilute solution at low scattering angles. The obtained translational diffusion coefficients are represented by rigid rod‐like or prolate ellipsoid‐like molecular shapes. The measurements of diffusion coefficients reveal a length‐dependent ratio of 1:2:3 between the three oligomers, which directly correlates to the expected length extension from trimer to nonamer.
Two new chemically stable metalloporphyrin-bridged metal-catechol frameworks, InTCP-Co and FeTCP-Co, were constructed to achieve artificial photosynthesis without additional sacrificial agents and photosensitizers. The CO2 photoreduction rate over FeTCP-Co considerably exceeds that obtained over InTCP-Co, and the incorporation of uncoordinated hydroxyl groups, associated with catechol, into the network further promotes the photocatalytic activity. The iron-oxo coordination chain assists energy band alignment and provides a redox-active site, and the uncoordinated hydroxyl group contributes to the visible-light absorptance, charge-carrier transfer, and CO2-scaffold affinity. With a formic acid selectivity of 97.8 %, FeTCP-OH-Co affords CO2 photoconversion with a reaction rate 4.3 and 15.7 times higher than those of FeTCP- Co and InTCP-Co, respectively. These findings are also consistent with the spectroscopic study and DFT calculation. 相似文献
Combining the selectivity of G-quadruplex (G4) ligands with the spatial and temporal control of photochemistry is an emerging strategy to elucidate the biological relevance of these structures. In this work, we developed six novel V-shaped G4 ligands that can, upon irradiation, form stable covalent adducts with G4 structures via the reactive intermediate, quinone methide (QM). We thoroughly investigated the photochemical properties of the ligands and their ability to generate QMs. Subsequently, we analyzed their specificity for various topologies of G4 and discovered a preferential binding towards the human telomeric sequence. Finally, we tested the ligand ability to act as photochemical alkylating agents, identifying the covalent adducts with G4 structures. This work introduces a novel molecular tool in the chemical biology toolkit for G4s. 相似文献