Nm For Complexes Research Articles

Blue/green light‐emitting diode based on diethyl[N‐arylmethylenethiobenzahydrazonato]gallium complexes

AbstractThree diethylgallium complexes of type Et2GaL [L = N‐(4‐methoxy) benzylidenethiobenzahydrazonato (1), N‐(4‐N,N‐dimethylamino)benzy lidenethiobenzahydrazonato (2) and N‐(9‐anthryl)methylenethio benzahydrazonato (3)] were synthesized by the reaction of triethylgallium with appropriate N‐arylmethylenethiobenzahydrazones. The compounds obtained were characterized by elemental analysis, 1H NMR, IR and mass spectroscopy, respectively. Monolayer light‐emitting diodes based on the diethyl[N‐arylmethylenethio benzahydrazonato]gallium doped poly(vinylcarbazole) were fabricated using a spin coating method. The photoluminescent and electroluminescent emission spectra of 1 and 3 were measured (429 and 479 nm for 1 and 3, respectively). The electroluminescent properties of 1 and 3 were also studied. The electroluminscence bands are located in the blue/green region (465 and 510 nm for complexes 1 and 3, respectively). Copyright © 2006 John Wiley & Sons, Ltd.

Electrophosphorescent divalent osmium and ruthenium complexes: A density functional theory investigation of their electronic and spectroscopic properties

Structures of divalent osmium and ruthenium complexes of [M(bpy) 3] 2+, [M(bpy) 2P 2] 2+ and [M(dpb) 2P 2] 2+ (M=Ru, Os, bpy=2,2′-bipyridine, dpb=4,4′-diphenyl-2,2′-bipyridine, P 2=cis-1,2-bis(diphenylphosphino)ethylene) in the ground and the lowest triplet states were fully optimized with density functional theory. The features of the absorption bands and phosphorescent emission from the lowest triplet state for the complexes have been described by time-dependent density functional theory. The [Os(bpy) 3] 2+ complex in methanol solution exhibits two strong absorption bands at ∼495 and ∼445 nm, which are well reproduced by the present calculations. There is one absorption peak observed at 440-460 nm for the divalent Ru polypyridyl complexes in methanol solution, which is close to the TDDFT calculated values of 415–440 nm for the complex of [Ru(bpy) 3] 2+. All evidences from the optimized structures, the calculated atomic charges and spin densities for the triplet complexes support the conclusion that phosphorescent emission in the divalent Os and Ru complexes originate from the triplet metal-to-ligand-charge-transfer state. This has been discussed in detail.

Synthesis, structural characterization and electroluminescence study of alkylgallium derivatives of thiobenzhydrazones

Six dimethylgallium complexes of type Me 2GaL [L= N-benzylidenethiobenzahydrazonato ( 1), N-(4-methoxy)benzylidenethiobenzahydrazonato ( 2), N-(3,4-dimethoxy)benzylidenethiobenzahydrazonato ( 3), N-(4- N, N-dimethylamino)benzylidenethiobenzahydrazonato ( 4), N-(2-naphthyl)methylenethiobenzahydrazonato ( 5) and N-(9-anthryl)methylenethiobenzahydrazonato ( 6)] have been synthesized by reaction of trimethylgallium with appropriate N-arylmethylenethiobenzahydrazones. The complexes obtained have been characterized by elemental analysis, 1H-NMR, IR and mass spectroscopy. Structure of 2 has been determined by X-ray single-crystal analysis, in which Ga atom is four-coordinated. Compounds 2– 4 emit blue colors at λ max=432–479 nm when irradiated by UV light. The electroluminescent (EL) properties of 2, 3 and 4 were examined by fabricating EL devices using 2, 3 and 4 as emitter, respectively. The EL bands are located in the blue region (451, 454 and 479 nm for complexes 2, 3 and 4, respectively).

Coagulation factor X inhibitor from hundred-pace snake ( Deinagkistrodon acutus) venom

Deinagkistrodon acutus venom contains a collection of anticoagulant proteins that has been reported to prevent prothrombinase assembly ( Teng and Seegers, 1981, Thromb. Res. 23, 255). A partial sequence indicates that these proteins are related to the functionally equivalent protein in Trimeresurus flavoviridis ( Atoda et al., 1991, J. Biochem. 106, 808). Inhibition of prothrombinase, the complex of Factors X a and V a combined with phospholipids, is expressed in bovine, human, and rat plasmas as indicated by an assay dependent on only prothrombinase activity. The concentration dependence of inhibition of prothrombin conversion by different combinations of the components of bovine prothrombinase under the same conditions yielded estimates of apparent dissociation constants of 104 nM and 2 nM for complexes of the inhibitor with Factor X a and with Factors X a and V a, respectively. Because this inhibitor does not prevent Factor X a alone from converting prothrombin, but blocks the other combinations, we conclude the inhibitor prevents the complex of Factors X a and V a from binding to phospholipid surfaces and to prothrombin. The inhibitor also blocks the activation of Factor X by Factor VII a and thromboplastin as well. However, the inhibitor has no effect on thrombin-induced clotting or fibrinolysis induced by either plasminogen activator or streptokinase. Therefore, this inhibitor has several properties required of an anticoagulant, therapeutic agent.

Identification by affinity labeling of potential sites in 23-S rRNA interacting with the 3' end of tRNA.

A derivative of tRNAPhe carrying at its 3' end a photolyzable group was chemically synthesized by coupling p-azidobenzoylglycylhydrazide to periodate-oxidized tRNA. The reaction converts the 3'-terminal ribofuranoside residue into a six-membered ring. The binding of p-azidobenzoylglycylhydrazide-tRNA to 70-S ribosomes resembles the binding of Phe-tRNA in its requirement for poly(U) and Mg2+ dependence. Irradiation at wavelengths greater than 300 nm of complexes of p-azidobenzoylglycylhydrazide-tRNA and 70-S ribosomes results in the covalent binding of approximately 20% of the reversibly bound tRNA to the ribosomes. The labeling occurs predominantly at a single site in 23-S rRNA within the sequence included in the 18-S fragment. To identify the modified sequence, an RNase A digest of 23-S rRNA was fractionated on a hydrophobic matrix (Porapak Q) and adsorbed and non-adsorbed fractions were compared by fingerprint analysis. A relatively intense spot was observed in the expected region in the fingerprint of the adsorbed fraction. The presence of an unusual nucleotide in the sequence of this oligonucleotide was demonstrated by a mobility-shift analysis of a partial nuclease P1 digest. The sequence derived is G*-A-A-G-C (the asterisk denoting the site of modification). Sequences at six positions in the 23-S rRNA are compatible with the sequence of the oligonucleotide determined. Of the six positions five are located within nucleotides 1467-1887. This region of approximately 400 nucleotides is likely to include the sequence interacting with the 3' end of tRNA and possibly forming part of the peptidyl-transferase center.

The interaction of actinomycin C3 and actinomine with DNA. A small-angle x-ray scattering study.

Small-angle X-ray scattering was applied to solutions of calf thymus DNA and calf thymus DNA complexed with various amounts of actinomycin C3 or actinomine in phosphate-saline buffer at pH 6.9 and I equals 0.2. From the measurements of DNA in the absence of dye, two cross-section radii of gyration of R-c equals 0.875 plus or minus 0.015 nm and R-c2 equals 0.81 plus or minus 0.02 nm, and a mass per unit length of M/l equals 1906 plus or minus 43 daltons/nm resulted. The investigation of DNA complexed with dye revealed a decrease of the cross-section radii of gyration as compared to those for the DNA in the absence of dye and a relatively low increase of the mass per unit length on binding of actinomycin and a slight decrease of M/l on binding of actinomine. The latter results are interpreted on the basis of a length increase of the DNA double helix by 0.47 plus or minus 0.03 nm per actinomycin molecule and by 0.355 plus or minus 0.03 nm per actinomine molecule bound. The results for R-c and R-c2 obtained for the various samples of complexed DNA were extrapolated to the limiting binding ratio where each dye molecule is associated with a minimum of six nucleotide pairs. According to this extrapolation, the cross-section radii of gyration of such a complex would amount to (R-c)b equals 0.805 plus or minus 0.015 nm and (R-c2)b equals 0.76 plus or minus 0.015 nm for the complex with actinomycin, and to (R-c)b equals 0.77 plus or minus 0.015 nm and (R-c2)b equals 0.75 plus or minus 0.01 nm for the actinomine complex. On the basis of a core and shell model for solvated DNA, these results can be understood as to indicate a decrease of the radial dimensions of both the core and the shell when the dye is bound. The experimental results are compared with theoretical data calculated from the atomic coordinates of the detailed intercalation model for the actinomycin - DNA complex as recently proposed by Sobell and Jain. The model proves to be consistent fairly well with our data on the length increase of the double helix, but it appears to be unable to explain the experimentally observed decrease of R-c2 on binding of dye.