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101.
Giuliano Alagona Caterina Ghio Alessandro Giolitti Susanna Monti 《Theoretical chemistry accounts》1999,101(1-3):143-150
Several histidine-tryptophan complexes (either stacked or T-shaped), derived from the crystal structures available in the
Brookhaven Protein Data Bank, have been examined with molecular mechanics (MM), using the Tripos force field with Gasteiger-Hückel
charges, whose trend was found to be analogous to the AMBER or CHARMM ones. The MM results were compared to the ab initio
MP2 results, with and without counterpoise (CP) correction, previously obtained using extended basis sets on 5-methylimidazole
and indole as model systems. MM seems to underestimate the interaction energy between the two monomers when compared to the
uncorrected MP2 results, while the agreement is much better after including the CP correction at the MP2 level in all cases.
MM was thus used to qualitatively analyse the dependence of the stacking energy on the ring rotation at a variable distance
and ring centroid displacement for these systems, while keeping the rings in parallel planes. An analogous study was carried
out for a T-shaped adduct.
Received: 24 March 1998 / Accepted: 3 September 1998 / Published online: 1 February 1999 相似文献
102.
José Fernández-Bertrán Luis M. Alfonso Juan C. Alvarez Edilso Reguera 《Journal of inclusion phenomena and macrocyclic chemistry》2000,37(1-4):131-136
The adducts of urea and solid alkyl derivatives can beobtained mechanochemically in good yields. Theproducts synthesized by grinding the solid reagentshave identical IR spectra and XRD powder patterns tothose obtained by crystallization from ethanolicsolutions. 相似文献
103.
104.
Thermal behaviour of tri(O,O'-diisopropyldithiophosphate)cobalt(III), Co(dptp)3 and bis (O,O'-diethyldithiophosphate)nickel(II), Ni(detp)2 and its adducts with pyridine, Ni(detp)2(py)2 or 4-methylpyridine, Ni(detp)(mpy)2 in a dynamic nitrogen atmosphere was investigated by TG-DTG and DSC techniques, which showed a medium endothermic peak for
the evolution process of pyridine(or 4-methylpyridine) and a strong exothermic peak for that of O,O'-diethyldithiophosphate.
The thermal stability and decomposition patterns for these compounds were compared and interpreted in terms of structural
features such as bond character and steric effects. The kinetic parameters and mechanisms of every decomposition stage involved
for all these complexes were obtained employing the non-isothermal kinetic analysis method suggested by Malek et al., which
showed the kinetics mechanism for pyrolysis of pyridine(or 4-methylpyridine) is an S-B empirical model with lower activation
energy, while that of O,O'-dialkyldithiophosphate is a diffusion model. These results are in accord with the fact that two
ligands are of different type.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
105.
106.
107.
Cover Picture: Metal‐Free Addition/Head‐to‐Tail Polymerization of Transient Phosphinoboranes,RPH‐BH2: A Route to Poly(alkylphosphinoboranes) (Angew. Chem. Int. Ed. 46/2015)
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108.
《Comptes Rendus Chimie》2015,18(2):137-148
Cancer has become a leading cause of death worldwide, which is responsible for 7.6 million cancer deaths according to GLOBOCAN survey conducted in 2008. The exploration of cis-platin analogues (carboplatin, lobaplatin, nedaplatin, oxaliplatin) and their incorporation to the treatment of cancer patients has further led interest in exploring metal-based anticancer drugs. The current study describes the synthesis of two new tetra-coordinated mono- and tetranuclear organotin(IV) carboxylate complexes and their in vitro anticancer studies. Each one of the complexes (1–2) has been characterized by analytical (micro- and gravimetric analysis) and spectroscopic (FTIR, 1H, 13C, 119Sn-NMR) techniques. Furthermore, molecular structures of 1 and 2 were elucidated using X-ray crystallography. The characterization data showed that the coordination took place via oxygen atoms from the carboxylate anions to generate 1 as an organodistannoxane dimer and 2 as a mononuclear complex. Exceptionally, the NMR spectroscopic and X-ray crystallographic study showed that acetone molecules also took part in crystallizing 2. Both complexes were tested against three cancerous (colon cancer HCT 116, breast cancer MCF 7, leukemia K562) and one non-cancerous (3T3-L1) cell lines. Both complexes showed same IC50 value (0.2 μM) against HCT 116, whereas for the other two cancer cell lines (MCF 7 and K562) and a normal cell line (3T3-L1), 2 showed results better than 1. Importantly, the complexes showed exceptional activity against MCF 7 and K562 cell lines and the IC50 values were calculated in nanomoles (MCF 7, IC50s = 86.5 and 53.4 nM; K 562, IC50s = 22.9 and 49.6 nM for 1 and 2, respectively). Both, 1 and 2, showed IC50 values many times better than the standard drugs (5-FU, Tamoxifen, betulinic acid and cis-platin) used. Compared to cancerous cell lines, the complexes showed mild toxicity against normal cells (3T3-L1). Overall, two remained relatively effective. 相似文献
109.
Soumava Biswas Himanshu Sekhar Jena Suresh Sanda Prof. Dr. Sanjit Konar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13793-13801
Three isostructural lanthanide‐based two‐ dimensional coordination polymers (CPs) {[Ln2(L)3(H2O)2]n ? 2n CH3OH) ? 2n H2O} (Ln=Gd3+ ( 1 ), Tb3+ ( 2 ), Dy3+ ( 3 ); H2L=cyclobutane‐1,1‐dicarboxylic acid) were synthesized by using a low molecular weight dicarboxylate ligand and characterized. Single‐crystal structure analysis showed that in complexes 1 – 3 lanthanide centers are connected by μ3‐bridging cyclobutanedicarboxylate ligands along the c axis to form a rod‐shaped infinite 1D coordination chain, which is further linked with nearby chains by μ4‐connected cyclobutanedicarboxylate ligands to form 2D CPs in the bc plane. Viewing the packing of the complexes down the b axis reveals that the lattice methanol molecules are located in the interlayer space between the adjacent 2D layers and form H‐bonds with lattice and coordinated water molecules to form 1D chains. Magnetic properties of complexes 1 – 3 were thoroughly investigated. Complex 1 exhibits dominant ferromagnetic interaction between two nearby gadolinium centers and also acts as a cryogenic magnetic refrigerant having a significant magnetic entropy change of ?ΔSm=32.8 J kg?1 K?1 for ΔH=7 T at 4 K (calculated from isothermal magnetization data). Complex 3 shows slow relaxation of magnetization below 10 K. Impedance analysis revealed that the complexes show humidity‐dependent proton conductivity (σ=1.5×10?5 S cm?1 for 1 , σ=2.07×10?4 S cm?1 for 2 , and σ=1.1×10?3 S cm?1 for 3 ) at elevated temperature (>75 °C). They retain the conductivity for up to 10 h at high temperature and high humidity. Furthermore, the proton conductivity results were correlated with the number of water molecules from the water‐vapor adsorption measurements. Water‐vapor adsorption studies showed hysteretic and two‐step water vapor adsorption (182000 μL g?1 for 1 , 184000 μL g?1 for 2 , and 1874000 μL g?1 for 3 ) in the experimental pressure range. Simulation of water‐vapor adsorption by the Monte Carlo method (for 1 ) confirmed the high density of adsorbed water molecules, preferentially in the interlayer space between the 2D layers. 相似文献
110.
在水热条件下,通过使用羧酸和螯合配体得到了一个系列的四核镧系簇合物,即[Ln4(mnba)12(tzp)2(H2O)2](Ln=Gd(1),Tb(2),Er(3);Hmnba=间硝基苯甲酸;tzp=2-(1H-1,2,4-三唑-3-基)吡啶))。这3个化合物是同构的,且具有线性的四核簇结构。磁性研究表明,化合物1和3中簇内镧系离子之间是弱铁磁耦合的,但化合物2中铽离子之间是弱的反铁磁相互作用和(或)铽离子激发的斯塔克能级的去布居。化合物1具有较大的磁热效应(-ΔSmmax=20.6 J·kg-1·k-1)。交流磁化率测试表明化合物3展现出频率和温度依赖的虚部信号,这是慢磁弛豫的典型特征,原因是铒离子的强各向异性和铁磁耦合的存在。 相似文献