1,4,8,11-tetraazacyclotetradecan

Figure 4 Bicyclam derivatives (A) JM2763 and (B) JM3100, each consisting of two cyclam (1,4,8,11-tetraazacyclotetradecane) moieties tethered via a propylene (JM2763) or phenylenebis(methylene) bridge (JM3100).

The monovalent Co chemistry of amines is sparse. No structurally characterized example of low-valent Co complexed exclusively to amines is known. At low potentials and in non-aqueous solutions, Co1 amines have been identified electrochemically, but usually in the presence of co-ligands that stabilize the reduced complex. At low potential, the putative monovalent [Co(cyclam)]+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) in NaOH solution catalyzes the reduction of both nitrate and nitrite to give mixtures of hydroxylamine and ammonia.100 Mixed N-donor systems bearing 7r-acceptor imine ligands in addition to amines are well known, but these examples are discussed separately in Section 6.1.2.1.3. 

The 14-membered macrocycle 1,4,8,11-tetraazacyclotetradecane (cyclam or [14]aneN4), unlike cyclen, is capable of encircling most transition metal ions and in the case of Co111 the trans configuration is much preferred by comparison with the folded cis isomer. Electrochemical reduction of A,v-[Co(cyclam)(OI I)2]+ in 3M NaOH leads to rapid isomerization to the trans form, and the relative stabilities of the trans and cis isomers of the di- and trivalent complexes were determined from a thermodynamic cycle.702 This preference for trans orientation of the non-macrocyclic donors has enabled the isolation and investigation of many Co complexes without the complications of isomerization. Some novel examples include /r[Pg.61]

Using 1,4,8,11-tetraazacyclotetradecane, the structure of complex (800) (distorted trigonal planar Cu-Cu 6.739 A) was determined. Reactivity with 02 was investigated to demonstrate the formation of trans-l,2-peroxo species.585 As part of their work with copper(I) complexes with 02, the structure of a dicopper(I) complex ((801) distorted tetrahedral 7.04 A), supported by macrocyclic ligand environment, was reported by Comba and co-workers. Tolman and co-workers structurally characterized a three-coordinate copper(I)-phenoxide complex (802) (planar T-shaped) that models the reduced form of GO.587 The copper(I) analogue [Cu(L)][CF3-SO3]-0.43MeOI I (803) of a copper(II) complex (534) was also reported to demonstrate the role of ligand framework conformability in CV /Cu1 redox potentials.434 Wilson and co-workers... 

An extremely selective electrocatalyst for C02 reduction to CO in water has recently been found by Beley et a/.135 A rather simple Ni complex of 1,4,8,11-tetraazacyclotetradecane, [Ni(II)-cyclam],... 

It is well-established that electroreduced nickel(I) complexes of cyclam and a variety of substituted cyclams add oxidatively to alkyl halides to give alkylnickel(III) complexes in organic solvents,251,276 the lifetime of the carbon-nickel bond governing the overall behavior of the system. However, it was shown that [Ni (tmc)]+ (one-electron reduced form of complex (17) tmc= 1,4,8,11-teramethyl 1,4,8,11-tetraazacyclotetradecane) reacts with alkyl chlorides in aqueous alkaline solution in a one-electron process.277,278... 

H. Stephan, A. Rohrich, S. Noll, J. Steinbach, R. Kirchner, and J. Seidel, Carbohydratation of 1,4,8,11-tetraazacyclotetradecane (cyclam) Synthesis and binding properties toward concanavalin A, Tetrahedron Lett., 48 (2007) 8834-8838. 

DMCBCy Dimethylated 1,8-ethylene cross-bridged 1,4,8,11 -tetraazacyclotetradecane... 

While the basic and or applied chemistry of saturated macrocyclic polyamines, typically represented by 1,4,7,10-tetraazacyclododecane (cyclen, 1) and 1,4,8,11-tetraazacyclotetradecane (cyclam, 2), have both... 

Spin crossover in iron(III) has been generated using the N4-donating macro-cyclic ligands 1,4,8,11-tetraazacyclotetradecane (cyclam) and its tetramethy-lated derivative (tmcyclam), as well as with the Schiff base system H2amben (Fig. 13). 

Gouanve et al. [9] presented another approach to designing copper nanosensors. They prepared cross-linked polystryrene beads (0 14 nm) and functionalized the surface with 1,4,8,11-tetraazacyclotetradecane (Cyclam), which selectively bound copper ions. The core of the beads was stained with a lipophilic fluorescent dye 9,10-diphenylanthracene by swelling. Fluorescence of the dye was quenched in the presence of Cu2+ due to FRET. The particles were suitable for sensing Cu2+ in micromolar concentrations. 

In most cases, metal ion coordination by a dendrimer takes place by units that are present along the dendrimer branches (e.g., amine, imine, or amide groups) or appended at the dendrimer periphery (e.g., terpyridine, cathecolamide ligands). When multiple identical coordinating units are present, dendrimers give rise to metal complexes of variable stoichiometry and unknown structures. Luminescent dendrimers with a well defined metal-coordinating site have been reported so far [16, 17], and the most used coordination site is 1,4,8,11-tetraazacyclotetradecane (cyclam). 

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