Synthesis and single crystal X-ray structures of the first paramagnetic transition metal complexes containing chiral ethylenedithio-tetrathiafulvalene-oxazoline (EDT-TTF-OX) 1a-c and ethylenedithio-tetrathiafulvalene-thiomethyloxazoline 2 (EDT-TTF-(SMe)OX) ligands based on copper (II) and cobalt (II) are described. The racemic [EDT-TTF-OX][Cu(hfac)2] complex 3a crystallizes in the triclinic centrosymmetric space group , whereas the enantiopure counterparts 3b-c crystallize in the triclinic non-centrosymmetric space group P1. Cu(II) adopts a distorted square pyramidal coordination geometry, a much weaker Cu?STTF interaction also being identified. The same coordination pattern around Cu(II) is observed in the complex [(rac)-EDT-TTF-(SMe)OX][Cu(hfac)2] (4) in spite of the bidentate nature of the redox active ligand. DFT theoretical calculations afforded two equilibrium configurations for a corresponding model complex, in which the metal centre establishes secondary coordination either with one STTF or with the SMe group. The same ligand coordinates the cobalt (II) to afford the octahedral complex [(rac)-EDT-TTF-(SMe)OX][Co(hfac)2] (5). In all these novel complexes, the paramagnetic centres are structurally and magnetically isolated. Cyclic voltammetry measurements show the stability of the radical cation species. 相似文献
Interactions of cationic porphyrins bearing five-membered rings at the meso position, meso-tetrakis(1,2-dimethylpyrazolium-4-yl)porphyrin (MPzP; M is H2, CuII or ZnII), with synthetic polynucleotides poly(dG-dC)2 and poly(dA-dT)2 have been characterized by viscometric, visible absorption, circular dichroisim and magnetic circular dichroism spectroscopic and melting temperature measurements. Both H2PzP and CuPzP are intercalated into poly(dG-dC)2 and are outside-bound to the major groove of poly(dA-dT)2, while ZnPzP is outside-bound to the minor groove of poly(dA-dT)2 and surprisingly is intercalated into poly(dG-dC)2. The binding constants of the porphyrin and poly(dG-dC)2 and poly(dA-dT)2 are on the order of 106 M−1 and are comparable to those of other cationic porphyrins so far reported. The process of the binding of the porphyrin to poly(dG-dC)2 and poly(dA-dT)2 is exothermic and enthalpically driven for H2PzP, whereas it is endothermic and entropically driven for CuPzP and ZnPzP. These results have revealed that the kind of the central metal ion of metalloporphyrins influences the characteristics of the binding of the porphyrins to DNA.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
Helix–coil transition curves are calculated for poly (dA) poly(dT) and poly (dA-dT) poly (dA-dT) using the integral equation approach of Goel and Montroll.5 The transitions are described by the loop entropy model with the exponent of the loop entropy factor, k, remaining an arbitrary constant. The theoretical calculations are compared with experimental transition curves of the two polymers. Results indicate that the stacking energies for these two polymers differ by about 1 kcal/mole of base pairs. Also, a fit between theory and experiment was not possible for k > 1.70. 相似文献
Lithioamidines {R′N(Li)C(R)NR′, I; R = CH3, R′ = C6H5, p-CH3,C6H4} react with iron(III) chloride in monoglyme to produce navy-blue, high spin Fe{R′NC(R)NR′}3 complexes which are extremely air and moisture sensitive. The corresponding reaction when R = R′ = C6H5 produces a soluble red complex and an air-stable green complex, whereas when R = H, R′ = C6H5 and R = R′ = C6H5 and the reaction is started at ca. ?20°, red and green complexes respectively are formed. Though all the complexes are formulated Fe{R′NC(R)NR′}3, their properties reflect association through bridging amidino-groups. Iron(II) chloride reacts with I(R = CH3, R′ = p-CH3C6H4) to form two complexes, one crimson and soluble in organic solvents, and one brown and insoluble, which are fomulated [Fe{R′NC(R)NR′}2]n. The iron(III) complexes failed to react with, or were decomposed by, a variety of reducing, electrophilic and nucleophilic reagents, though blue Fe{p-CH3C6H4NC(CH3)N-p-CH3C6H4}3 reacts readily with nitric oxide to form a purple addition complex from which the N-nitroso-compound p-CH3C6H4NC(CH3)N(NO)-p-CH3C6H4 was obtained in high yield. Treatment of the corresponding brown iron(II) complex with nitric oxide gave no reaction. 相似文献
Two structurally related vanadium(V) complexes, K3[VO2(C2O4)2]·3H2O and K3[VO(O2)(C2O4)2]·1/2H2O, were thoroughly characterized by infrared, Raman, and electronic spectroscopies. The effect of both complexes on the viability of the human MG-63 osteosarcoma cells was tested using the MTT assay. The monoperoxo complex shows a very strong antiproliferative activity (at 100-μM concentration, this complex diminished the cell viability ca. 80 %), whereas the dioxo complex was inactive. 相似文献
N-(3,5-Dichlorophenylsulfonyl)-(R)-thioprolyl biarylalanine 10a has been identified as a potent and specific antagonist of the alpha(4)beta(1) integrin. Altering the configuration of thioproline from R to S led to a series of dual antagonists of alpha(4)beta(1) and alpha(4)beta(7), and the N-acetyl analogue 8b was found to be the most potent dual antagonist. A binding site model for alpha(4)beta(1) and alpha(4)beta(7) is proposed to explain the structure-activity relationship. 相似文献
The trinuclear [{RuII(bpy)2(bpy-terpy)}2CoII]6+ complex (16+) in which a Co(II)-bis-terpyridine-like centre is covalently linked to two Ru(II)-tris-bipyridine-like moieties by a bridging bipyridine-terpyridine ligand has been synthesised and characterised. Its electrochemical, photophysical and photochemical properties have been investigated in CH3CN. The cyclic voltammetry exhibits two successive reversible oxidation processes, corresponding to the CoIII/CoII and RuIII/RuII redox couples at E1/2 = −0.06 and 0.91 V vs Ag/Ag+ 10 mM, respectively. The one-electron oxidized form of the complex, [{RuII(bpy)2(bpy-terpy)}2CoIII]7+ (17+) obtained after exhaustive electrolysis carried out at 0.2 V is fully stable. 16+ and 17+ are only poorly luminescent, indicating that the covalent linkage of the Ru(II)-tris-bipyridine centre to the cobalt subunit leads to a strong quenching of the RuII excited state by an intramolecular process. Luminescence lifetime experiments carried out at different temperatures indicate that the transfer is more efficient for 17+ compare to 16+ due to lower activation energy. Continuous irradiation of 17+ performed at 405 nm in the presence of P(Ph)3 acting as sacrificial electron donor leads to its quantitative reduction into 16+, whereas similar experiment starting from 16+ with a sulfonium salt as sacrificial electron acceptor converts 16+ into 17+ with a slower rate and a maximum yield of 80%. These photoinduced electron transfers were followed by UV-Visible spectroscopy and compared with those obtained with a simple mixture of both mononuclear parent complexes i.e. [RuII(bpy)3]2+ and [CoII(tolyl-terpy)2]2+ or [CoIII(tolyl-terpy)2]3+ (tolyl-terpy = 4′-(4-methylphenyl)-2,2′:6′,2′′-terpyridine). 相似文献
