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251.
Ibaniewkor Lyngdoh Mawnai Sanjay Adhikari Lincoln Dkhar Jaya Lakshmi Tyagi Krishna Mohan Poluri 《Journal of Coordination Chemistry》2019,72(2):294-308
The reaction of [(arene)MCl2]2 with pyridylpyrazolyl ligands (L1 and L2) in the presence of ammonium hexafluorophosphate leads to formation of cationic complexes having the general formula [(arene)M(L)Cl]PF6 {M?=?Ru, arene = p-cymene (1, 4); Cp*, M?=?Rh (2, 5); Cp*, M?=?Ir (3, 6); L?=?2-(1H-pyrazol-1-yl)pyridine (L1), 2-(3,5-dimethyl-1H-pyrazol-1-yl)pyridine (L2)}. Similarly the reaction of [CpRu(PPh3)2Cl] and [(ind)Ru(PPh3)2Cl] (ind?=?η5-C9H7) with L1 and L2 yielded cationic complexes which have been formulated as [(Cp/ind)Ru(L)PPh3]PF6 (7–10). All these complexes were characterized by analytical and spectroscopic techniques. The pyridylpyrazolyl ligands coordinated metal through pyridyl and pyrazolyl nitrogens forming a six-membered metallacycle. The ligands as well as the complexes were evaluated for their in vitro antibacterial activity by agar well diffusion method against two Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and two Gram positive bacteria (Staphylococcus aureus and Bacillus thuriengiensis). Results show that the ligands and the complexes have significant antibacterial activity against Gram negative bacteria. 相似文献
252.
The orientation and conformation of the cell-penetrating peptide "penetratin" associated with phospholipid vesicle membranes has been determined using polarized-light spectroscopy. The magnitude of orientation of penetratin is unprecedented for a solute in our membrane system, which we believe indicates a strong, specific interaction with the membrane. To validate the spectroscopic technique for studying the orientation of the two tryptophan residues of penetratin, we applied tryptophan octyl ester as a model compound. It is found to be incorporated in the membrane and preferentially oriented with its hydrophobic benzene edge of the indole chromophore pointing into the membrane and its hydrophilic groups oriented toward the water. For penetratin, the results indicate that a central alpha-helical part of the peptide is aligned parallel with the membrane surface, while the ends of the peptide adopt a planar structure. The planes of the two tryptophan side chains show a preferred orientation parallel with the membrane surface, indicating that they are not inserted into the membrane. 相似文献
253.
Lorna Barr Paul G. Dumanski Christopher J. Easton Jason B. Harper Kitty Lee Stephen F. Lincoln Adam G. Meyer Jamie S. Simpson 《Journal of inclusion phenomena and macrocyclic chemistry》2004,50(1-2):19-24
The ability of cyclodextrins to form inclusion complexes with hydrophobic species in aqueous solution makes them well-suited to the development of molecular reactors, to be used as miniature reaction vessels in order to control the outcomes of chemical transformations at the molecular level. In this manner, reaction rates can be increased and products may be obtained that are different to those normally accessible from reactions in free solution. Examples used to illustrate these effects include: the application of cyclodextrins to control the regioselectivity of bromination of aromatic substrates with pyridinium dichlorobromate: the use of a metallocyclodextrin to increase the rate of hydrolysis of a phosphate triester by almost five orders of magnitude; the development of modified cyclodextrins to increase the rates and reverse the regioselectivity of nitrile oxide cycloadditions ; and the use of a cyclodextrin dimer to change the ratio of formation of indigoid dyes by a factor of more than 3500. 相似文献
254.
We report the use of spectrally resolved femtosecond two-color three-pulse photon echoes as a potentially powerful multidimensional technique for studying vibrational and electronic dynamics in complex molecules. The wavelengths of the pump and probe laser pulses are found to have a dramatic effect on the spectrum of the photon echo signal and can be chosen to select different sets of energy levels in the vibrational manifold, allowing a study of the dynamics and vibrational splitting in either the ground or the excited state. The technique is applied to studies of the dynamics of vibrational electronic states in the dye molecule Rhodamine 101 in methanol. 相似文献
255.
Stephen F. Lincoln John H. Coates Bruce G. Doddridge Andrea M. Hounslow 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(1):49-53
19F nmr and ultraviolet spectroscopic studies show that the inclusion of the anion of the drug diflunisal (DF) by alpha- and beta- cyclodextrins (CD and CD) in water produces the complexes: DF.CD, DF.CD and DF.(CD)2 characterized by stability constants of 17, 1.81×105 and 3.07×103 dm3mol–1 respectively. 相似文献
256.
Stephen F. Lincoln Andrea M. Hounslow John H. Coates Rosa P. Villani Robert L. Schiller 《Journal of inclusion phenomena and macrocyclic chemistry》1988,6(2):183-191
The complexation of the diflunisal anion (DF) by γ-cyclodextrin (γCD) and permethylatedβ-cyclodextrin (βPCD) in aqueous solution at pH 7.00 at 298.2 K, has been studied by UV-visible and19F NMR spectroscopy. The formation of 1∶1 and 1∶2 γCD inclusion complexes proceeds through the two equilibria: (K1) $${\text{DF + }}\gamma {\text{CD}} \rightleftharpoons {\text{DF}} \cdot \gamma {\text{CD}}$$ (K2) $${\text{DF}} \cdot \gamma {\text{CD + }}\gamma {\text{CD }} \rightleftharpoons {\text{ DF}} \cdot {\text{(}}\gamma {\text{CD)}}_{\text{2}} {\text{ }}$$ characterised byK 1=(5.5±0.2)×104 dm3 mol?1 andK 2=(2.3±0.2)×104 dm3 mol?1 derived from UV-visible spectrophotometric data. The analogous βPCD complexes are characterised byK 1=(6.86±0.02)×104 dm3 mol?1 andK 2=(8.75±2.7)×101 dm3 mol?1. The variation of the19F chemical shift of DF on inclusion is consistent with the formation of 1∶1 and 1∶2 complexes also. Comparisons with related systems are made. 相似文献
257.
The polymeric lanthanide complexes (Ln(mu-CH3OC6H5C4O3)(CH3OC6H5C4O3)2 (H2O)4.xH2O)n [Ln=La (1), Eu (2), Gd (3)], formed from the reaction of aqueous solutions of anisolesquarate and Ln(NO3)3.xH2O, are all structurally similar with only subtle differences between the lanthanum complex and the isomorphous pair of europium and gadolinium analogues. The lanthanum atom in 1 has a square antiprismatic coordination geometry comprising two pendant and two mu-1,3-bridging anisolesquarate groups and four aqua ligands. Complexes 2 and 3 have two independent metal atoms in their asymmetric units compared to one for the lanthanum complex. However, the gross structures of 1-3 are essentially the same. The asymmetric unit of the terbium complex ((CH3OC6H5C4O3)3Tb(H2O)4(mu-CH3OC6H5C4O3)(CH3OC6H5C4O3)2Tb(H2O)5).H2O (4) contains two independent binuclear units which hydrogen bond to form an extended structure very similar to those of 1-3. The ionic polymers ([Ln(mu2-C4O4)(H2O)6][C6H5NHC4O3].4H2O)n [Ln=Eu (5), Gd (6), Tb (7)] result from the incomplete hydrolysis of the anilinosquarate ion during the attempted synthesis of Eu(III), Gd(III), and Tb(III) anilinosquarate complexes. However, complete hydrolysis of the substituent is accomplished by La(III) ions, and the neutral polymer (La2(mu2-C4O4)2(mu3-C4O4)(H2O)11.2H2O)n (8) is formed. In complexes 5-7, the central lanthanide atom has a square antiprismatic geometry, being bonded to two mu-1,2-bridging squarate and six aqua ligands. Two anilinosquarate counteranions participate in second-sphere coordination via direct hydrogen bonding to aqua ligands on each metal center. These counteranions, and the included waters of crystallization, serve to link neighboring cationic polymer chains via an extensive array of O-H...O hydrogen bonds to form a 3-dimensional network. The polymeric lanthanum complex 8 contains two different metal environments, each having distorted monocapped square antiprismatic geometry. For one lanthanum atom the coordination polyhedron comprises five aqua and four squarate ligands, while for the other the polyhedron consists of six aqua and three squarate ligands; in each case one of the aqua ligands occupies the capping position. The squarate ligand exhibits two coordination modes in 8 (mu-1,2- and mu-1,3-bridging), and neighboring polymer chains are cross-linked by hydrogen bonds to form a 3-dimensional network. 相似文献
258.
Adams D Ahmad S Akchurin N Birmingham P Breuer H Chang CC Cihangir S Corcoran MD Davis WL Gustafson HR Holmgren H Kasper P Kruk J Lincoln D Longo MJ Marraffino J McPherson J Miettinen HE Morrow G Mutchler GS Naples D Onel Y Skeens J Thomas GP Traynor MM Waters JW Webster MS Xu JP Zhu Q 《Physical review letters》1994,72(15):2337-2340
259.
The rotaxane serves as the basis of a light driven molecular muscle, where reversible photoisomerisation of the stilbene units causes the cyclodextrins to move off and on the stilbene units, contracting and extending the distance between the blocking groups. 相似文献
260.
Ruthenium complexes with dipyridophenazine (dppz) type ligands have several characteristics that make them good candidates for use as luminescence probes for hydrophobic environments. Most studies have concerned DNA intercalation, but also lipid membrane fluidity and liposome orientation have been assessed. We report here dipyridophenazine derivatives ([Ru(phen)2dppz]2+) substituted with one or two alkyl ether chains of different lengths aimed at finding the optimum substitution for a high quantum yield when bound to a phospholipid membrane bilayer. The orientation of membrane bound molecules is studied using flow linear dichroism (LD) with phospholipid vesicles as membrane models. LD, excitation anisotropy, steady state luminescence and excited-state lifetime measurements are used to quantitatively investigate the insertion and orientation of the complexes in the vesicles. All complexes are inserted with their long axis of the dppz moiety mainly parallel to the lipid chains, and the degree of orientation is comparable to that of the orientation probe retinoic acid. The ruthenium "head group" with its positive charge functions as a buoy at the water-membrane interface while the hydrophobic chain part embeds the complex down into the bilayer. The complex with two hexyl ether substituents (named D6) has the optimal chain length regarding membrane insertion and orientation, and together with the highest quantum yield, is the best luminescence membrane probe in the two series. 相似文献