Studies of pendant-arm macrocyclic ligands. Part 1. Synthesis of two new penta-aza ligands, and observation of pH-dependent reversible equilibria between trigonal-bipyramidal and square-planar forms of their nickel(II) and copper(II) complexes. Crystal structure of a trigonal-bipyramidal nickel(II) complex

Alcock, Nathaniel W.; Kingston, R. G.; Moore, Peter; Pierpoint, Colin

doi:10.1039/dt9840001937

Cited by 83 publications

(27 citation statements)

References 4 publications

(6 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Addition of 1 equiv of Ni(II) perchlorate in n -butanol, which had been previously distilled to one-half volume to remove water, to an ethanol solution of 15 gave a bright purple precipitate which analyzed to the formula 15 :Ni(ClO 4 ) 2 ( 26 ). In full agreement with the literature, ,, the UV absorption spectrum of 26 (9.0 mM) in aqueous 1 M NaClO 4 (pH 6.9) gave three bands at 327 (sh), 531 (ε = 10) and 934 (ε = 9.1) nm, consistent with a 5-coordinate, high-spin Ni(II) complex in which the pyridine moiety is pendant-coordinated. Dissolving the solid 26 (9.0 mM) in 5 M aqueous perchloric acid gave an immediate color change from purple ( 26 ) to orange ( 27 ) (this concentration of HClO 4 was required for complete conversion of 26 to 27 ), which was found to be reversible upon alternate additions of sodium hydroxide and perchloric acid.…”

Section: Resultssupporting

confidence: 89%

Synthesis and Structure−Activity Relationships of Phenylenebis(methylene)- Linked Bis-tetraazamacrocycles That Inhibit Human Immunodeficiency Virus Replication. 2. Effect of Heteroaromatic Linkers on the Activity of Bicyclams

Padmanabhan

et al. 1996

J. Med. Chem.

View full text Add to dashboard Cite

A series of bicyclam analogs connected through a heteroaromatic linker have been synthesized and evaluated for their inhibitory effects on HIV-1 (IIIB) and HIV-2 (ROD) replication in MT-4 cells. The activity of pyridine- and pyrazine-linked bicyclams was found to be highly dependent upon the substitution of the heteroaromatic linker connecting the cyclam rings. For example, 2,6- and 3,5-pyridine-linked bicyclams were potent inhibitors of HIV-1 and HIV-2 replication, whereas the 2,5- and 2,4-substituted pyridine-linked compounds exhibited substantially reduced activity and, in addition, were found to be highly toxic to MT-4 cells. We have subsequently discovered that these effects are not unique; amino-substituted linkers also have the potential to deactivate phenylenebis(methylene)-linked bicyclams. A model is proposed to explain the deactivating effects of the pyridine group in certain substitution patterns based on the ability of the pyridine nitrogen to participate in pendant conformations (complexation) with the adjacent azamacrocyclic ring, which may involve hydrogen bonding or coordination to a transition metal. The introduction of a sterically hindering group such as phenyl at the 6-position of the 2,4-substituted pyridine-linked bicyclam appears to prevent pendant conformations, providing an analog with comparable anti-HIV-1 and anti-HIV-2 activities to the parent m-phenylenebis(methylene)-linked bicyclam. The results of this study have been used to develop a quantitative structure-activity relationship model with improved predictive capability in order to aid the design of antiviral bis-azamacrocyclic analogs.

show abstract

Section: Resultssupporting

confidence: 89%

Synthesis and Structure−Activity Relationships of Phenylenebis(methylene)- Linked Bis-tetraazamacrocycles That Inhibit Human Immunodeficiency Virus Replication. 2. Effect of Heteroaromatic Linkers on the Activity of Bicyclams

Padmanabhan

et al. 1996

J. Med. Chem.

View full text Add to dashboard Cite

show abstract

“…Compound 2,6-pyridinedicarboxaldehyde was prepared according to an established procedure, while 2,6-diacetylpyridine, MAO (10% solution in toluene), and all of the anilines were purchased from Aldrich Chemical Co. All other chemicals were obtained commercially and used as received unless stated otherwise.…”

Section: Methodsmentioning

confidence: 99%

Iron and Cobalt Ethylene Polymerization Catalysts Bearing 2,6-Bis(Imino)Pyridyl Ligands: Synthesis, Structures, and Polymerization Studies

et al. 1999

View full text Add to dashboard Cite

The synthesis, characterization, and ethylene polymerization behavior of a series of iron and cobalt halide complexes, LMX n (M ) Fe, X ) Cl, n ) 2, 3, X ) Br, n ) 2; M ) Co, X ) Cl, n ) 2), bearing chelating 2,6-bis(imino)pyridyl ligands L [L ) 2,6-(ArNCR 1 ) 2 C 5 H 3 N] is reported. X-ray diffraction studies show the geometry at the metal centers to be either distorted square pyramidal or distorted trigonal bipyramidal. Treatment of the complexes LMX n with methylaluminoxane (MAO) leads to highly active ethylene polymerization catalysts converting ethylene to highly linear polyethylene (PE). LFeX 2 precatalysts with ketimine ligands (R 1 ) Me) are approximately an order of magnitude more active than precatalysts with aldimine ligands (R 1 ) H). Catalyst productivities in the range 3750-20600 g/mmol‚h‚bar are observed for Fe-based ketimine catalysts, while Co ketimine systems display activities of 450-1740 g/mmol‚h‚bar. Molecular weights (M w ) of the polymers produced are in the range 14000-611000. Changing reaction conditions also affects productivity and molecular weight; in some systems, a bimodal molecular weight distribution is observed. On the basis of evidence gathered to date, the lower molecular weight fraction is a result of chain transfer to aluminum while the higher molecular weight fraction is produced by a combination of mainly -H transfer and some chain transfer to aluminum.

show abstract

“…[7] All solvents and chemicals were reagent-grade quality, commercially purchased and used as supplied, except for 1,3,5-tris(aminomethyl)-2,4,6-triethylbenzene and 2,6-pyridinedicarbaldehyde which where prepared according to literature methods. [19] KNO 3 , Cu-A C H T U N G T R E N N U N G (NO 3 ) 2 ·2.5H 2 O and CuA C H T U N G T R E N N U N G (ClO 4 ) 2 ·6H 2 O were analytical-grade quality, commercially purchased and used as supplied. All the solutions were prepared with demineralised water (obtained by a Millipore/Milli-Q system) and methanol purified by standard methods.…”

Section: Methodsmentioning

confidence: 99%

“…[7] All solvents and chemicals were reagent-grade quality, commercially purchased and used as supplied, except for 1,3,5-tris(aminomethyl)-2,4,6-triethylbenzene and 2,6-pyridinedicarbaldehyde which where prepared according to literature methods. [19] All the solutions were prepared with demineralised water (obtained by a Millipore/Milli-Q system) and methanol purified by standard methods. [20] IR spectra were recorded in the 4000-450 cm À1 region at room temperature by using KBr pellets and a UNICAM Mattson 7000 spectrometer.…”

Section: Methodsmentioning

confidence: 99%

A Trinuclear Copper(II) Cryptate and Its μ₃‐CO₃ Cascade Complex: Thermodynamics, Structural and Magnetic Properties

Mateus

Delgado

Lloret

et al. 2011

Chemistry A European J

View full text Add to dashboard Cite

The 2,4,6-triethylbenzene-capped hexaamine macrobicycle with pyridyl spacers (pyr) was able to coordinate three copper(II) ions within its cavity. Potentiometric studies performed at 298.2 K in MeOH/H(2)O (50:50 v/v) and at ionic strength 0.10 mol dm(-3) in KNO(3) revealed that trinuclear species predominate in solution from pH 5.0, the hydroxo complexes being the main species, which start forming at unusual very low pH values. The single-crystal X-ray determination of the trinuclear complex showed that the three copper centres have square-planar geometry, arranged in an almost equilateral triangle, and have carbonate bridging the three metal centres. The presence of carbonate resulted from fixation of atmospheric CO(2). The present study represents the first μ(3)-CO(3)-bridged trinuclear copper(II) complex located in the interior of a macrobicyclic cavity. The magnetic data of [Cu(3)(pyr)(μ(3)-CO(3))]·(ClO(4))(4) showed ferromagnetic intramolecular interactions [J=3.80 cm(-1), based on the Hamiltonian H=-J(S(1)S(2)+S(2)S(3)+S(1)S(3))] yielding a spin quartet, S=3/2, ground state. Density functional calculations on the experimental geometry of the trinuclear complex showed that the ferromagnetic nature of the magnetic coupling can be attributed to the syn-anti conformation of the carbonato bridge, and a magneto-structural correlation, based on the different conformations (syn-anti, syn-syn and anti-anti), is presented. The interesting properties observed, namely the lowering of the pK(a) of coordinated water molecules to unusual values and the good fit of the carbonate anion between the copper centres, derive from the special architecture of pyr.

show abstract

Cited by 83 publications

References 4 publications

Synthesis and Structure−Activity Relationships of Phenylenebis(methylene)- Linked Bis-tetraazamacrocycles That Inhibit Human Immunodeficiency Virus Replication. 2. Effect of Heteroaromatic Linkers on the Activity of Bicyclams

Synthesis and Structure−Activity Relationships of Phenylenebis(methylene)- Linked Bis-tetraazamacrocycles That Inhibit Human Immunodeficiency Virus Replication. 2. Effect of Heteroaromatic Linkers on the Activity of Bicyclams

Iron and Cobalt Ethylene Polymerization Catalysts Bearing 2,6-Bis(Imino)Pyridyl Ligands: Synthesis, Structures, and Polymerization Studies

A Trinuclear Copper(II) Cryptate and Its μ₃‐CO₃ Cascade Complex: Thermodynamics, Structural and Magnetic Properties

Contact Info

Product

Resources

About

Cited by 83 publications

References 4 publications

Synthesis and Structure−Activity Relationships of Phenylenebis(methylene)- Linked Bis-tetraazamacrocycles That Inhibit Human Immunodeficiency Virus Replication. 2. Effect of Heteroaromatic Linkers on the Activity of Bicyclams

Synthesis and Structure−Activity Relationships of Phenylenebis(methylene)- Linked Bis-tetraazamacrocycles That Inhibit Human Immunodeficiency Virus Replication. 2. Effect of Heteroaromatic Linkers on the Activity of Bicyclams

Iron and Cobalt Ethylene Polymerization Catalysts Bearing 2,6-Bis(Imino)Pyridyl Ligands: Synthesis, Structures, and Polymerization Studies

A Trinuclear Copper(II) Cryptate and Its μ3‐CO3 Cascade Complex: Thermodynamics, Structural and Magnetic Properties

Contact Info

Product

Resources

About

A Trinuclear Copper(II) Cryptate and Its μ₃‐CO₃ Cascade Complex: Thermodynamics, Structural and Magnetic Properties