TRIAD Base

Having verified that the photophysical and electrochemical properties of the Ir(terpy)2+ derivatives were satisfying the characteristics we looked for, in that the excited state energy was well above 2 eV and that reduction was easier than for the related Ru(terpy)2+ derivatives, we decided to use Ir(terpy)2+ as assembling unit and as electron relay in the following evolution of the project. We then synthesized two triads based on the Ir(III) complex, using zinc or free base tetra-aryl-porphyrin as the donor and photoactive centre and a gold tetraarylporphyrin as the acceptor. 

Late in 2002, US EPA, working with an organization called the Brownfields Technology Support Center, decided that the Cos Cob site would be appropriate for application of the Triad approach. In February 2003, a Triad-based field investigation was conducted at the Cos Cob site over the course of one week. In a single mobilization, the field team characterized the site for all constituents of concern effectively (US EPA, Office of Solid Waste and Emergency Response, 2004). 

Dyads and triads based on the photoactive, multibridging [Ru(bpz)3] (bpz = bipyrazine) complex directly bound to transition metal complexes were obtained by following the procedures previously reported for the generation of symmetric heptanuclear supermolecules (67-69). Such systems contain a tris(bpz)ruthenium (II) ion [RuJ attached to bis(bpy)chlororuthenium(II)/(III) [Rup], or penta-cyanoferrate(II)/(III) complexes via a bpz bridging ligand, as shown for the... 

Finally, it is important to note (Section 5.3.6) that electrochemistry and UV-Vis absorption spectra of molecular dyads or triads based on metal polypyridines show that electronic interactions between the components of the systems discussed above are too small to influence ground-state behavior. Nevertheless, they are sufficient to allow for very fast intramolecular electron transfer when electronically excited. In fact electronic coupling of 0.002-0.005 eV would be quite enough, but hardly detectable electrochemically. Detailed studies of electrochemistry and spectroscopy of these supramolecular systems and their components are, nevertheless, essential for the understanding of the energetics of photoinduced intramolecular electron and energy transfer reactions. 

A simple synthesis of pyrazolo[4, 5 ][60]fullerenes from pyrazolyl hydrazones with [60]fullerene was achieved with microwave irradiation evidence of intramolecular charge-transfer interaction was shown <1999TL1587>. Novel C6o-fused isoxazolines have been synthesized from 1,3-dipolar cycloadditions of pyrazole nitrile oxides to Ceo under thermal or microwave irradiation <1999T4889>. A new triad based on pyrazolino[60]fullerene and a conjugated... 

In general, the stability of Y RY triplexes containing cytosine residues in the third strand decreases as the pH of the solution is raised from acidic to alkaline values [27, 45, 46]. This is due to a decreased protonation at the N3 of C with increased pH. The triplex stability reaches a maximum around pH 5.8, close to the pAa of the N3 of C. Various approaches have been described to overcome this pH limitation (Figure 14), since any triplex-dependent in vivo applications demand stable triplexes at physiological pH. Since the R RY motif does not involve any charged triad bases, its stability is independent of pH. 

In the case of triads, the adoption of atomic number has an intriguing consequence that has seldom been discussed About 50% of all vertical triads based on atomic number, rather than atomic weight, are absolutely exact This remarkable result is quite easy to appreciate by referring to the long form of the modern periodic table (figure 6.7). 

The meso triad-based, enantiomorphic site control type of stereochemical errors, mm, are formed whenever the said balanced nonbonded steric interaction is perturbed, and the correct alignment of the substituents of the three main participants (ligand, polymer chain and monomer) is not materialized perfectly. In such a case, a monomer with wrong face is inserted and a unit with inverted configuration is enchained. The ability of occasional reverse face selectivity emanates firom the inherent structural factors of the metallocene-based catalyst. It is independent of monomer concentration and cormter-ion pairing nature however, it is dependent on polymerization temperature. 

In Part I we present a survey of the work done in the preparation and characterization of synthetic and semi-synthetic chiral thermotropic liquid crystal polymers. For convenience, we have grouped the polymeric materials (until now reported) according to the nature of the repeat unit and relevant position of the mesogen, side chain and main chain polymers. In Part II we report on the results obtained in our laboratories on optically active thermotropic polyesters containing mesogenic aromatic dyads or triads based on / -oxybenzoic acid. 

Welsch S, Nohra B, Peresypkina EV, Lescop C, Scheer M, R au R (2009) Chemistry of bridging phosphanes a comparative study within Cu-I-Ag-I-Au-I triad-based homonuclear dimers. Chem Eur J 15 4685... 

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