ABSTRACT
Three triazine-based europium(III) complexes were synthesized that demonstrated strong two-photon induced europium emission with a high two-photon absorption cross-section. The modified triazine ligand of complex 3 initiated over 100% enhancement of the two-photon absorption cross-section (σ(2): 320 GM) when compared with complex 1 (σ(2): 128 GM) in a solution of DMSO. Europium complex 3 is also stable in vitro, and power-dependence curves were obtained in vitro to confirm the two-photon-induced f-f emission in HeLa cells.
Subject(s)
Europium/chemistry , Molecular Imaging , Organometallic Compounds/chemistry , Photons , Energy Transfer , HeLa Cells , Humans , Ligands , Luminescence , Luminescent Measurements , Molecular Structure , Organometallic Compounds/chemical synthesis , Quantum Theory , Stereoisomerism , Triazines/chemistryABSTRACT
Reaction of a pinene-based pyridylthioamide with 1,4-dibromo-2,3-butanedione in refluxing methanol yielded a new chiral pyridylthiazole ligand L which forms a dinuclear double-stranded helicate with Cu(i) ions; this helicate has opposite helical chirality when compared with its quaterpyridine analogue.
Subject(s)
Copper/chemistry , Thiazoles/chemical synthesis , Butanones/chemical synthesis , Cations, Divalent/chemistry , Ligands , Stereoisomerism , Thiazoles/chemistryABSTRACT
A series of single-stranded helical Re(I) complexes, of formula [Re(2)(L)Br(2)(CO)(6)], were prepared by reacting [Re(CO)(5)Br] with chiral quaterpyridines L1-4. By (1)H and (13)C NMR analysis, all the crude complexes consisted of a pair of stereoisomers. Sterically more demanding ligand L4 induced a higher ratio (80:20) than L1-3 (about 56:44). Stereochemically pure complexes could be obtained by recrystallization in CH(2)Cl(2). X-ray crystallographic analysis of single crystals from purified complexes showed a single-stranded helical structure with a bridging ligand wrapped around two distorted octahedral rhenium metals, both of which possessed one bromide ligand and three carbonyl ligands in a fac coordination. The helical core is established by extensive noncovalent electrostatic interactions and chiral information is transmitted from the ligand to the helix through these interactions. Solution behavior was studied by CD spectroscopy, and the strong Cotton effect confirms the integrity of the helical structure in solution. The diastereoselectivity of helicates is proposed to be induced by steric interaction between the bromine atom and the substituent of the bridging ligand.
Subject(s)
Crystallography, X-Ray , Pyridines/chemistry , Rhenium/chemistry , Bromides/chemical synthesis , Bromides/chemistry , Hydrogen Bonding , Ligands , Magnetic Resonance Spectroscopy , Models, Molecular , Molecular Structure , Pyridines/chemical synthesis , Quantum Theory , StereoisomerismABSTRACT
A chiral iron-sexipyridine complex-hydrogen peroxide mixture is a highly efficient catalytic system for styrene epoxidation with excellent reactivity (3 min, 95% yield) and chemoselectivity (98%).
Subject(s)
Alkenes/chemistry , Epoxy Compounds/chemical synthesis , Hydrogen Peroxide/chemistry , Iron/chemistry , Pyridines/chemistry , Catalysis , Circular Dichroism , Ligands , Nickel/chemistry , Palladium/chemistry , StereoisomerismABSTRACT
Chiral double-stranded helicates, formed between Cu(I) ion and C(2)-symmetric oligopyridines, were used for catalytic asymmetric cyclopropanation of alkenes; low catalyst loadings (0.2 mol%), high TONs (up to 404) and short reaction times (30-60 min) were achieved with [Cu(2)L(2)]OTf(2)(L = chiral C(2)-symmetric terpyridine).
Subject(s)
Copper/chemistry , Cyclopropanes/chemistry , Organometallic Compounds/chemical synthesis , Pyridines/chemistry , Crystallography, X-Ray , Ligands , Macromolecular Substances/chemical synthesis , Macromolecular Substances/chemistry , Molecular Conformation , Organometallic Compounds/chemistry , StereoisomerismABSTRACT
Chiral C2-symmetric quaterpyridine L reacts with [Pd(eta3-C3H5)Cl]2 to form a chiral single-stranded helical binuclear palladium complex of formula [Pd2(eta3-C3H5)2(L)]2+; the complex can efficiently catalyze allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate with enantioselectivity up to 85%.
ABSTRACT
A water-soluble europium(III) complex (1) has been synthesized and demonstrated to be a specific fluorescence probe for the paralytic shellfish toxin saxitoxin, a neurotoxin that blocks the voltage-gated sodium channels on cell membranes. Saxitoxin binds to the europium complex (K(B) = 6.1 × 10(4) M(-1)) and triggers a two-photon induced f-f emission enhancement by over 100% and increases the two-photon absorption cross-section from 9 to 36 GM.
Subject(s)
Europium/chemistry , Fluorescent Dyes/chemistry , Photons , Saxitoxin/chemistry , Animals , Molecular Structure , ShellfishABSTRACT
New binuclear double-stranded helicates were formed between manganese(ii) perchlorate and chiral phenyl- and polyphenyl-bridged oligopyridines; they are active catalysts for alkene epoxidation.
Subject(s)
Alkenes/chemistry , Epoxy Compounds/chemistry , Manganese/chemistry , Catalysis , Circular Dichroism , Crystallography, X-Ray , Molecular Conformation , Perchlorates/chemistry , Pyridines/chemistry , Spectrometry, Mass, Electrospray Ionization , StereoisomerismABSTRACT
Re(I) tricarbonyl bipyridine and terpyridine complexes catalyse stereospecific cyclopropanation of alkenes; high selectivity of cyclopropane vs coupling and an ee of 73% and 62% for cis- and trans-cyclopropanes of styrene respectively were achieved with the [Re(L)(CO)(3)(MeCN)]OTf complex (L = chiral C(2)-symmetric terpyridine ligand).