Cyclam functionalization

Jermakowicz-Bartkowiak D. A preliminary evaluation on the use of the cyclam functionalized resin for the noble metals sorption. Reactive and Functional Pol3tmers 2007 67 1505-1514. 

The synthesis of metal-complexing nanoparticles with an average size ranging from 15 to 25 nm was recently described (Larpent et al, 2003). It consists of a two-step procedure starting first with the microemulsion polymerization of a mixture of styrene and vinylbenzylchloride in the presence of a cationic surfactant, then followed by the postfunctionalization with a selective macrocyclic ligand, tetrazacyclotetradecane (cyclam). The authors showed the ability of these cyclam-functionalized nanoparticles to complex copper and in addition they observed that they exhibited a solution-hke complexation behavior, demonstrating the accessibility of the immobilized ligand. 

Goubert-Renaudin S, Etienne M, Rousselin Y, Denat F, Lebeau B, Walcarius A (2(K>9) Cyclam-functionalized silica-modified electrodes for selective determination of Cu(II). Electroanalysis 21 280-289... 

Countless macrocycles containing basic functionalities have been synthesized and, for a large number of compounds, values have been determined (Patai, 1980 Gokel and Korzenowski, 1982 Kaden, 1984 Kimura, 1985 Lindoy, 1989 Vogtle, 1989, 1991 Gokel, 1991, 1992 Izatt et al., 1991, 1992 Dietrich et al., 1993). Usually, the basic function in these macrocycles is a nitrogen atom the compounds are (poly)azamacrocycles. But in azacrowns like [1] or cyclams [2] the /n-orientation of the lone pair at the nitrogen atom is not assured. Murakami et al. (1991) synthesized the... 

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. 

The redox properties of the hexaaza monocyclic complexes 1-7 are similar to those of the cyclam. This indicates that the electrochemical properties of the complexes are only slightly affected by the presence of uncoordinated tertiary nitrogen atoms, the length of the pendent chain, and the type of the functional group appended at the bridgehead nitrogen 16, 58). 

However, the redox potentials of the Ni(II) complexes of the aza-cyclam (3b-3g) containing carboxamide or sulfonamide functional groups are reported to be influenced by the nature of the functional group. In particular, the amide fragment controls the reduction potential for the Nim/Nin and NiI1/NiI redox couples, which may be attributed to the it interaction between the nickel ion and the amido group 14). 

Introduction of optically active functionalized pendants to cyclam to give 32 and 33 was tried in order to examine their effects on reactivity and enantioselectivity. However, the overall result was not much different from that for simple cyclam, and no enantiomeric excess was observed (93). 

Functionalized CCs can also be obtained in good yields under mild conditions from epoxides and C02 by using an electrochemical procedure [149, 150]. For this, the CC formation is catalyzed by Ni(cyclam)Br and is carried out in singlecompartment cells fitted with a magnesium anode. The presence of functional groups such as chlorine, bromine, ether, ester or olefins is compatible with the reaction conditions. 

The standard synthesis for cyclam was developed by Barefield and Wagner in 1976.29 They used similar starting materials to the van Alphen procedure but the cyclisation yield is improved through the use of a nickel (II) template. Glyoxal completes the macrocycle by a Schiff base condensation reaction. The resulting imine functionalities are reduced with sodium borohydride to leave the complexed macrocycle. The metal ion is then removed by reaction with cyanide and the free ligand extracted with chloroform (Scheme 3.19). Yields are typically in the region of 60%. 

Cyclam, or 1,4,8,11-tetraazacyclotetradecane is a popular macrocyclic ligand for d-tran-sition metal coordination chemistry. It also coordinates to lanthanide ions, although much less strongly than the better size-adapted cyclen. As for the latter, however, derivatization of the amine functions by amide, carboxylate, or phosphinate groups considerably improves the coordination ability of the macrocycle. 

Disregarding this aspect, and since cyclam is an interesting core for constructing den-drimers because it can be easily functionalized and because despite its absence of spectroscopic properties, it can interact in such a way with dendrons as to modify their photophysical properties, the interaction of lanthanide ions with cy clam-based dendrimers has been investigated. The dendrimers are constmcted from the cyclam core fitted with four dimethoxyben-zene and eight naphthyl units (generation 1, fig. 81) second generation introduces a total of 12 dimethoxybenzene and 16 naphthyl moieties. Coordination to Lnm ions occurs in acetoni-trile/methylene chloride (Ln = Nd, Eu, Gd, Tb, and Dy), but no sensitized Ln-luminescence was observed (Saudan et al., 2004). Another example of a macrocycle-based dendrimer is discussed below in section 3.3.2. 

Aliphatic amines with three or more amine functions which form complexes with Rhm are represented in (48). These can be subdivided into linear (trien, 2,3,2-tet, etc.), branched (tren) and cyclic (cyclam, cyclen, etc.) amines, and will be discussed in that order. 

Bis-macrocycles (10), another extension of the concept of functionalized macrocycles, can be made by several different methods. One of the more commonly used is the coudeusation of two precursor chains already joined by the hnker. Bis-macrocycles also can be formed from cyclam (1) as a by-product bis-macrocycle in low yield (24)." ... 

The three components of the self-assembled structure have complementary properties so that new functions emerge from their assembly. Dendrimer 5 has a very high molar absorption coefficient in the UV spectral region because of 12 dimethoxybenzene and 16 naphthyl units, but it is unable to sensitize the emission of an Nd ion placed in its cyclam core. The [Ru(bpy)2(CN)2] complex can coordinate (by the cyanide ligands) and sensitize the emission of Nd ions. Self-assembly of the three species leads to a quite unusual Nd complex which exploits a dendrimer and an Ru complex as ligands. Such a system behaves as an antenna that can harvest UV to VIS light absorbed by both the... 

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