Applications for polyaza macrocycles with nitrogen-attached pendant arms. Elsevier; 2001. pp. 293-334. [DOI: 10.1016/s0898-8838(05)52006-3]

A Practical Synthesis of Macrocyclic Schiff Base Bearing Hydroxyethyl Pendants Utilizing Solubility Discrepancies

Abstract:

Six macrocyclic Schiff bases bearing hydroxyethyl pendants have been synthesized in high yields via [2 + 2] condensation between the rigid dialdehydes and 2-[bis(2-aminoethyl)amino]ethanol or 1-[bis(2-aminoethyl)amino]-2-propanol at 0 oC for 12 hours in the CH3CN/H2O mixture. Solubility discrepancies between macrocyclic products and raw materials in selected solvents enable a facile separation and high yields, avoiding any intractable chromatographic purification. This straightforward synthetic protocol provides a relatively facile resolution with potential widespread applications for the synthesis of Schiff bases.

Synthesis and structural chemistry of bicyclic hexaaza-dithia macrocycles containing pendant donor groups

An efficient medium-scale synthesis and the structural characterization of a series of macrobicyclic hexaaza-dithia macrocycles with pendant donor arms is presented.

1,4,8,11-Tetra-azonia-cyclo-tetra-decane tetra-kis-(hydrogensulfate)

In the title salt, C10H28N4 (4+)·4HSO4 (-), the cation lies about an inversion center. In the crystal, O-H⋯O and N-H⋯O hydrogen bonds connect the anions and cations, forming a three-dimensional network.

Copper and cobalt complexes of octadentate azamacrocycles: spectrophotometric titration, stopped-flow kinetics and crystallographic study

Details of complex formation kinetics are reported for tetrakis(2-hydroxyethyl) substituted cyclen (L(1)) and cyclam (L(2)) with Cu(II) and Co(II). Stopped-flow kinetics and spectroscopic titration methods were employed for the activation parameters and stability constants, respectively. X-ray studies revealed that the pendant 2-hydroxyethyl groups are not equivalent: two are folded over the macrocycle and maintained by intramolecular hydrogen bonds while the others are extended and pointed away from the macrocyclic cavity. Complex formation kinetics and spectroscopic titration were performed in aqueous acidic buffer solutions. Thermodynamic and kinetic parameters revealed that the ring size of the macrocycles plays an extremely important role for each metal ion studied. Stopped-flow kinetic measurements explained the mechanism of the complex formation process of both Cu(II) and Co(II) which proceed in outer-sphere interactions with ligands. There are two steps in the complex formation of the system studied. The initial step is a second order reaction between the metal ion and macrocycle with a second order rate constant.

Synthesis and characterization of water-operative cationic and anionic metal-ion activated molecular receptors for aromatic anions

Two new, octadentate, water-soluble, macrocyclic ligands, 1,4,7,10-tetrakis((2S)-(-)-2-hydroxy-3-[3'-(N,N,N-trimethylammonium)-phenoxy]-propyl)-1,4,7,10-tetraazacyclododecane tetratriflate, ((S)-tmappc12 triflate, L1 triflate) and 1,4,7,10-tetrakis((2S)-(-)-2-hydroxy-3-[2'-sulfo-4'-methylphenoxy]-propyl)-1,4,7,10-tetraazacyclododecane, ((S)-sthmppc12, L2H4) have been prepared with a view to using them to study anion sequestration in aqueous solution. Their pKa and metal-ion binding constant values with a range of alkaline earth, transition, and post-transition metals are reported. The eight-coordinate, water-soluble Cd(II) complexes of (L1)4+ and (L2)4-, [CdL1](CF3SO3)6 and (NH4)2-[CdL2], the former cationic and the latter anionic, have both been shown to be capable of acting as anion receptors in aqueous solution. The binding constant values (log(K/M-1) given in parentheses) for binding by the cationic receptor to a range of aromatic anions in water are p-nitrophenolate (1.7), p-formylphenolate (2.1), p-nitrobenzoate (3.0), p-aminobenzoate (4.5), p-dimethylaminobenzoate (>4.5), D- and L-tryptophanate (1.6, 2.2), phenoxyacetate (2.1), and acetate (2.3). With the anionic receptor, nonzero binding constants were only measurable for p-nitrobenzoate (approximately 0.4), p-aminobenzoate (2.0), and p-dimethylaminobenzoate (1.8). By reference to the X-ray determined structures of related, but water-insoluble inclusion complexes, anion retention is thought to occur within a hydrophobic cavity, with four convergent hydroxy groups at its base, which develops in (L1)4+ and (L2)4- through the juxtapositioning of aromatic rings that occurs as a consequence of octadentate coordination.

New modulated metallic macrocycles: Electrochemistry and their interaction with calf thymus DNA

New modulated pentacoordinate complexes [C17H34N7O2Cu]ClO4 (5), [C17H34N7O2Co]ClO4 (6), [C17H34N7O2Ni] ClO4 (7) have been synthesized by the interaction of 1,8-dihydro-1,3,6,8,10,13 Cu(II) (2), Co(II) (3), Ni(II) (4) hexaazacyclotetradecane complexes and Hsalea N-(2-hydroxy benzyl)-2-amino-1-ethanol ligand (1). All the complexes have been characterized by infrared, electron paramagnetic resonance, 1H and 13C nuclear magnetic resonance (NMR), 2D correlation spectroscopy NMR and ultraviolet-visible (UV-vis) spectroscopy. In all the complexes, the metal center is encapsulated by the Hsalea ligand in a pentacoordinate environment-vis absorption titration and viscometric studies have been carried out to ascertain the interaction of complexes 5 and 6 with calf thymus DNA (CT DNA). The experimental results suggest that complex 5 binds to CT DNA through partial intercalation of the aromatic ring into the base pair of DNA while complex 6 binds binds to CT DNA by electrostatic mode. The intrinsic binding constants K(b) of complex 5 and 6 were found to be 6.8 x 10(-5) M(-1) and 1.8 x 10(-4) M(-1), respectively. The binding of complexes 5 and 6 with CT DNA has also been investigated by cyclic voltammetry.

Novel and Disparate Hydrogen-Bonding Associations in 13-Amino-6-hydroxy-13-methyl-1,4,8,11-tetraazacyclotetradecane Tetrahydrochloride Monohydrate

The title compound crystallizes in the monoclinic space group Pn with two independent [LH4]Cl4·H2O formula units (L = 13-amino-6-hydroxy-13-methyl-1,4,8,11-tetraazacyclotetradecane) in the asymmetric unit. Despite pseudo-symmetry, these two units exhibit subtle and interesting differences in their hydrogen-bonded association by the interchange of the water molecule site with one of the chloride anions. Although a pentamine, L crystallizes as a tetrahydrochloride in which the tetracation has a conformation similar to that of tetraprotonated cyclam (1,4,8,11-tetraazacyclotetradecane), despite a different pattern of protonation sites. Difficulties in purification are perpetuated in the crystal, the minor isomeric component co-crystallizing in one of the cation sites.