Synthesis and Complexation of a Chiral Sexidentate Pendant-Arm Macropolycyclic Polyamino Acid

Abstract

A Al ll l e en nq qu ui ir ri ie es s a an nd d m ma an nu us sc cr ri ip pt ts s s sh ho ou ul ld d b be e d di ir re ec ct te ed d t to o: : Volume 55, 2002 © CSIRO 2002 publishing research papers from all fields of chemical science, including synthesis, structure, new materials, macromolecules, supramolecular chemistry, biological chemistry, nanotechnology, surface chemistry, and analytical techniques. The reaction of the acyclic complex ion (methyl (SS,SS)-3-[(2´-aminocyclohexyl)amino]-2-[(2´-aminocyclohexyl)aminomethyl]propionate)copper(II) with formaldehyde and nitroethane in basic solution yields the pendant-arm macrocyclic complex (SS,SS)-(methyl-15-methyl-15-nitro-2,6,13,17-tetraazatricyclo[16.4.0.0 7,12 ]docosane-4carboxylate)copper(II) ion. Reduction with zinc in hydrochloric acid yields the hydrochloride salt of the pendantarm macrocycle (SS,SS)-15-amino-15-methyl-2,6,13,17-tetraazatricyclo[16.4.0.0 7,12 ]docosane-4-carboxylic acid (1), separated into and isolated as the major trans (1a) and minor cis (1b) isomers. Co-ordination of (1) to several metal ions [Co III , Cr III , Ni II , Zn II , Cu II ] and comparison with a previously reported analogue without the cyclohexane rings, trans-13-amino-13-methyl-1,4,8,11-tetraazacyclotetradecane-6-carboxylic acid (2a) salt, is described. The [Ni{(1a) -H + }](ClO 4 ) crystallizes in the monoclinic space group P2 1 , a 9.710(2), b 14.442(1), c 10.317(2) Å, β 96.02(2)°. The nickel displays a distorted octahedral geometry, with all four secondary amines coordinated (Ni-N range 2.044(7)-2.063(6) Å), in addition to pendant primary amine (Ni-N, 2.109(6) Å) and carboxylate (Ni-O, 2.100(6) Å) groups. Protonation constants for the trans (1a) and cis (1b) isomers and stability constants of these isomers with the labile metal ions Zn II , Cd II , Hg II , Pb II , Mn II , and Co II were determined by potentiometric titrations. The log K values for 1 : 1 complexes show small variations between geometric isomers.

Coordination Chemistry of a New Rigid, Hexadentate Bispidine-Based Bis(amine)tetrakis(pyridine) Ligand

“…Metal−ligand complexation systems with rigid (macrocyclic) ligands have been modeled, in general, with a common and relatively simple model, featuring the formation of ML, MLH, and MLH - 1 species, and likewise, this can be applied here. However, the computed appearance of MLH could also be an artifact, due to a kinetic effect in the formation of the ML complex.…”

Template-directed synthesis of macrocyclic copper(II) complexes of diazacyclam, 1,3,6,10,12,15-hexaazatricyclo[13.3.1.16,10]eicosane

“…In most cases, these reactions involve formation of heteroatom-carbon bonds such as O-C [12], S-C [13,14], N-C [15,16], and N¼C [17,18]; C-C bond formation is another type of reaction commonly encountered in preparation of macrocyclic complexes [19,20]. Other reactions are rare such as B-O bond formation for the same synthesis [21,22].…”

A highly active nickel electrocatalyst shows excellent selectivity for CO2 reduction in acidic media

“…The cobalt analogue of 2 has been reported for use in dye-sensitized solar cells with binding of the –CO 2 H group directly to the metal centre. 36 , 39 However we do recognise that the empirical nature of the relationship in Fig. 2b does not provide direct evidence of the functional role of the carboxylic acid.…”