Trimers supramolecular

Yang, G. and Raptis, R.G. (2003) Supramolecular assembly of trimeric Gold(l) pyrazolates through aurophihc attractions. Inorganic Chemistry, 42, 261-263. 

Charge-transfer adducts are formed with the gold(I) trimers [Au3(MeN=COR)3] (R = Me, Et), which act as electron donors, and organic electron acceptors as nitro-9-fluorenes. The structures of these adducts involve mixed stacks in which the gold trimers and the planar nitro-fluorenes are interleaved.3130 No luminescence has been observed from these solid charge-transfer adducts, which is not surprising since the luminescence of [Au3(MeN=COR)3] is a property that is associated with the supramolecular organization in the solid. 

Hawthorne and co-workers have also produced a series of macrocyclic Lewis acid hosts called mercuracarborands (156, 157, and 158) (Fig. 84) with structures incorporating electron-withdrawing icosahedral carboranes and electrophilic mercury centers. They were synthesized by a kinetic halide ion template effect that afforded tetrameric cycles or cyclic trimers in the presence or absence of halide ion templates, respectively.163 These complexes, which can bind a variety of electron-rich guests, are ideal for catalytic and ion-sensing applications, as well as for the assembly of supramolecular architectures. 

Sasaki and coworkers have examined reversible metal coordination as a mechanism for DCL generation in the presence of lectin biomolecules [49,50]. The use of metal ions in reversible processes is canonical to supramolecular chemistry, and has been explicitly demonstrated for doublelevel orthogonal DCLs by Lehn and Eliseev [51]. Sasaki s system is designed around octahedral Fe(II) bipyridine complexes. The bipyridine-modified A-acetylgalactosamine (bipy-GalNAc) (78) was found to trimer-ize in the presence of Fe(II) to afford a 3 1 mixture of the fac (79) and mer (80) diastereoisomers, each as a racemic mixture (A+A) (Scheme 2.12). 

The overall relative orientation of the secondary structures of an enzyme determines its three-dimensional shape, or tertiary structure. Some enzymes require multiple copies of the same enzyme to function. The individual enzymes cluster into groups of two or more (called dimers, trimers, etc.) and are held together by intermolecular forces. The relative positioning of the separate enzymes in the cluster determines the overall structure, or quaternary structure, of the supramolecular complex. While all enzymes have tertiary structure, only clusters of multiple enzyme subunits have quaternary structure. The overall folded conformation of a protein in its active, catalytic form is called the active or native conformation. 

Phthalocyanines and porphyrins are often used as model compounds for the manipulation (guest molecule) of surface-supported supramolecular two-dimensional arrays both in UHV and in solution. Spillmann et al. reported that zinc(II) 5,15-bis(3-cyanophcnyl)-10,20-bis 3,5-di(/c/7-bu(yl )phcnylj porphyrin, 2, molecules predominantly formed a hexagonal pattern by trimer formation, when 0.5-0.7 MLs of 2 was deposited on Ag(l 11) especially, 2 forms a characteristic nanostructure on Ag(l 11) at low coverage [163], As reported by Yokoyama et al., it is suggested that the molecular assembly is driven by both van der Waals and dipole-dipole interactions involving the polar 3-cyanophenyl residues [79], After further deposition of C60... 

Precursors based on Mo2" + and Rh2" + cores have been used in combination with dicarboxylate linkers to construct supramolecular arrays. Dimer-of-dimers, trimer-of-dimers (molecular triangles), and tetramer-of-dimers (molecular squares) have been prepared using this approach. Judicious selection of precursors and linkers are essential for the successful synthesis of the desired molecular architectures. A total of twelve dimer-of-dimers (100-111) of general formula [(DAniF)3M02]O2C-X-CO2M02[(DAniF)3] (DAniF = A,A -di(/ -anisyl)formamidinate) have been synthesized in which two M02 units are connected by bridging dicarboxylates. These compounds were prepared in one-pot reactions (Scheme 27). It is important to note that the six equatorial positions of the precursors are blocked in order to... 

Figure 3 Supramolecular dimers, trimers, and oligomers generated by H-bonding self-assembly of (a) adenine, (b) uracil, and (c) adenine-uracil base-pair. (R = sugar, alkyl, etc.)...

Ab initio and density functional theory (DET) methods have been exploited to determine the structures and the interaction energies of 2/7-isoxazol-5-one B, and its dimer and trimer structures in the gas phase. For the cyclic trimer, the computed structural parameters resulted in excellent agreement with the X-ray determination of the supramolecular aggregate of 4-(2-methoxybenzyl)-3-phenyl-4//-isoxazol-5-one, involving very strong intermolecular H-bonds of the NH tautomeric form, interpreted in terms of the RAHB (resonance-assisted hydrogen bond) model (see Section 4.03.3.1) <2002HCA2364>. 

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