Dimeric structures mono complexes

Thus, the formation of a cylinder-like supramolecular dimer is the key step in the construction of some micellar and vesicular assemblies. Several methods can be employed to make building blocks having cylinder-shaped structures. For example, cylinder-like supramolecular dimers can be initially formed from mono-functionalized pillararenes through supramolecular interactions such as ti-ti stacking. Functional groups can be used to modify pillararenes, and the pillararene derivatives obtained may form daisy-chain type dimers through the complexation. However, such dimers prefer to form further supramolecular polymers rather than spherical assemblies at certain concentrations. Therefore, it should be noted that the functional groups... 

The mono-thiocarbamate complexes [Ni(OSCNR2)2] [R = Me, Et, Pr", Pr , or Bu", R2 = ( 112)4 or (CH2)j] have been prepared. The isopropyl complex is dimeric in the vapour phase and low-polymeric or cyclic oligomeric structures are proposed for the others. Bis-pyridine and bis-pyrrolidine adducts have been isolated. - ... 

The routes for controlling the synthesis of mono- (903) and dinuclear (904) structure is, evidently, related to the donor properties of additional ligands [Scheme (4.62) L and L1]. In case of highly basic N-donors (L = py, bipy, o-phen), the mononuclear complexes 903 are generally formed [11,229,232], while the weakly basic solvents (L = MeOH [233]) lead to binuclear chelates of type 904. At the same time, the only example for 805 (L = o-phen) of a stable dimeric adduct with sufficiently high-basic o-phenanthroline is known and was shown above (Sec. 3.4.2). 

Oxidation of one of the hydroxyl groups of a 1,2 glycol to form an a-hydroxy carboxylic acid increases the complexity of the vanadate chemistry. Mono, di, tri and higher nuclearity compounds are formed with a-hydroxy carboxylic acids. Except for the dimeric products, the structures adopted by these compounds are not known with any degree of certainty. 

Somewhat surprisingly, maltol (2-methyl-3-hydroxy-4-pyrone), an aromatic analogue to a-hydroxy carboxylic acids, shows little inclination toward formation of dimeric complexes. Rather, the chemistry is more in parallel with that of oxalate, and an x-ray structure of the bismaltolato complex [25] shows a cis octahedral coordination similar to that found for the oxalate complex. Under mildly acidic to moderately basic solution, the major complexes are mono- and bisligand derivatives. The corresponding vanadium chemical shifts are -509 and -496 ppm, respectively [25,26], The closely related amines, 2-methyl-3-hydroxy-4-pyridinone and its N-... 

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