No abstract

Coordination polymers on the basis of the assembly of metal ion "connectors" and multidentate ligand "linkers" have been of great interest due to their intriguing architectures and versatile applications.1-9 Metallotetraazamacrocycles bearing equatorial amines coordinated to the central metal ions and axial sites opened for incoming "linkers" are good "connectors" as building blocks for the construction of coordination polymers. 10-15Among multidentate ligands, polycarboxylates have been widely used as "linkers" due to their versatile coordination modes toward metal ions. [16][17][18][19] An fdc (fdc = 1,1'-ferrocenedicarboxylate ion) ligand as a kind of polycarboxylates has attracted attention not only in the field of coordination chemistry but also in the field of organometallic chemistry. [20][21][22][23] During our efforts to explore the molecular interactions between metallomacrocycles and polycarboxylate ligands in zinc(II) and cadmium(II) tetraazamacrocycles containing bridging polycarboxylate ligands, we successfully synthesized and structurally characterized two 1D zinc(II) coordination polymers 1 and 2, where each ferrocenyl of bridging fdc ligands adopts different conformation, and a macrocyclic cadmium(II) dimer 3. Thus, two Cp (Cp = cyclopentadienyl) rings of fdc ligands in 1 are mutually staggered, whereas they are eclipsed in 2. The cadmium(II) cyclams with folded macrocycles are bridged by an oxalate ligand in 3. In this report we describe the details of the synthesis and structures of 1-3.

Macrocyclic transition metal complexes with polycarboxylate ligands have been proved to be good building blocks for the construction of coordination polymers and supramolecular networks. 1-6 Coordination polymers are generally composed of metal ion 'connectors' and multidentate ligand 'linkers', and the dimensionality of coordination polymers can be tuned by controlling the coordination sites of metal ion 'connectors' for multidentate ligand 'linkers'. 1 Thus, the construction of 1D coordination polymers is possible to be achieved by blocking equatorial sites of metal ions with polyazamacrocycles and leaving axial sites open for bridging ligands. Among multidentate ligand 'linkers', H4pm (pm = pyromellitate, 1,2,4,5-benzenetetracarboxylate) is one of the attracting linkers due to its versatile coordination tendencies of carboxylic acid groups to metal ions depending on the degree of deprotonation. 7-17 Moreover, the carboxylic acid groups of H4pm in metal complexes can act as hydrogen bond donors and/or acceptors via inter-and/or intramolecular fashion in extending the structures. In this report we describe the synthesis and structure of an undulated 1D coordination polymer {[Zn(L1)(H2pm)]•H2O}n (1) built by taking advantage of the directionality of zinc(II) macrocycles and the ability of H2pm ligands to bridge between zinc(II) ions, where the bridging H2pm ligand shows an unusual coordination of 1,5-COO − groups to zinc(II) ions. Experimental Section Materials, Methods and Apparatus. All chemicals used in the synthesis were of reagent grade and used without further purification. Distilled water was used for all procedures. Infrared spectra of solid samples were recorded on a Perkin-Elmer Paragon 1000 FT-IR spectrophotometer between 4000 cm −1 and 400 cm −1 as Nujol mulls on KBr discs. Elemental analysis was performed by the Korea Research Institute of Chemical Technology, Daejeon, Korea. The free ligand L1 was prepared according to a literature procedure. 18,19 The precursor complex Zn(L1)(NO3)2 was prepared by refluxing ligand L1 (3.36 g, 1.0 mmole) and Zn(NO3)2•6H2O (3 g, 1.01 mmole) in stirring methanol for a day, filtering, washing with methanol, and finally drying in air. The white powder of Zn(L1)(NO3)2 was obtained in 95% (5.0 g) yield. Synthesis of 1. To a DMF/H2O solution of Zn(L1)(NO3)2

No abstract

The amphiphilic TEMPO molecules consist of two dissimilar parts. One part is hydrophilic (head) and the rest part is hydrophobic (tail). The derivatives of 4-alkaneamino-2, 2, 6, 6-tetramethyl-1-piperidinyloxy radical ( C n-amino-TEMPO, n = 14, 16, 18, 20, 22) was synthesized with 4-amino-TEMPO and carboxylic acid. The C n-amino-TEMPOs equilibrated at the air/water interface form Langmuir monolayer by classical Langmuir monolayer techniques. The stable monolayers of C 14-22-amino-TEMPOs were characterized by pressure–area isotherms. The features of collapse pressure of C 14-22-amino-TEMPOs were confirmed on alkyl chain length. Limiting area points and take-off area points from surface pressure-MMA isotherms were subjected to the influence of subphase. The monolayer of C 22-amino-TEMPO which has longer alkyl chain was characterized by Brewster Angle Microscopy. So we can confirm phase transition by BAM images as monolayer is expanding at the room temperature.