Ligands 1,10-phenanthroline

The use of 1,10-phenanthroline as the organic binder allows the synthesis of metallopolymers possessing different metal ions with respect to the most common Ru(ll) and Os(ll). Vidal et al. [112] synthesized and electropolymerized a monomer containing Cu(I) centers co-ordinated to two 1,10-phenanthrolines, each one bearing one, two, or three consecutive Th units in 2 and 9 positions (see Fig. 3.25 for the case of a 2,2 -bithiophene unit). 

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In search of new sensitizers that absorb strongly in the visible region of the spectrum, Arakawa and co-workers have developed several sensitizers based on 1,10-phenanthroline ligands. Among these new compounds, (29) and (30) are noteworthy they show an intense and broad MLCT absorption band at 525 nm in ethanol. The energy levels of the LUMO and HOMO for (29) were estimated to be —1.02 and 0.89 eV vs. SCE, respectively, which are slightly more positive than those of the sensitizer (22). These sensitizers, when anchored onto a Ti02 surface, yield more than 85% photon to electron injection efficiencies.8,52,53... 

The versatility of the structural types possible for 1,10-phenanthroline ligands is exemplified in a review article on metal-to-ligand charge-transfer (MLCT) excited states of copper(ll) bis-phenanthroline coordination compounds, where 14 different 1,10-phenanthroline-based ligands were discussed (Figure 2) <2000CCR243>. 

The effect of the charge may also be seen in some nickel(n) complexes. The neutral complex 4.7, containing two anionic ligands obtained by the deprotonation of the salicylaldehyde derivative, is completely stabilised towards hydrolysis. In contrast, the monocationic complex 4.8, containing two neutral 1,10-phenanthroline ligands, is rapidly hydrolysed to the corresponding salicylaldehyde complex (Fig. 4-25). Presumably, the overall positive charge of the complex promotes the attack of the nucleophile upon the electrophilic carbon centre. 

Examples of redox indicators are Indigo Carmine (C.I. 73015 [ 860-22-0] 8), which is frequently employed, and ferroin, an iron(n) complex with three 1,10-phenanthroline ligands (14), which is widely used in water and wastewater analysis in the determination of chemical oxygen demand (COD) in an internationally standardized procedure. For the structure of the organic ligand, see p. 539. 

For [Cr(CO)4(phen)] and [W(CO)4(phen)], the crystal structures are known (85CJSC66, 85CJSC69, 90MK129). The ability of 1,10-phenanthroline to substitute 2,2 -bipyridine from [Mo(CO)4(bpy)] is ascribed to the more expressed ji-acceptor function and rigidity of the 1,10-phenanthroline ligand (88IC81). 

For this latter system, the synthetic approach is based on the template effect of an octahedral ruthenium(II) centre [97-100]. Two 1,10-phenanthroline ligands are incorporated in a ring, affording the precursor to the catenane. The... 

Addition of four methyl substituents to the 1,10-phenanthroline ligand increases the basicity of its N atoms, enhancing the propensity for hydrogen bonding with the water... 

Au forms distorted square-pyramidal complexes with 2,2 -biquinolyl and 2,9-dimethyl-1,10-phenanthroline ligands. 

In contrast, the complex [Cu (N N)2] gave no ESR signs for rapid electron hopping between the two N N = 2,9-diphenyl-1,10-phenanthroline ligands— probably as a result of the nearly orthogonal arrangement of the ligand n systems... 

No attempt has been made to include coverage of the structurally related 1,10-phenanthroline ligand nor of substituted derivatives of bpy once again, this was in an attempt to keep the literature to manageable proportions. We hope that this review will be of use to those working in the area of metal-bpy complexes. Complexes of the related ligand 2,2 6, 2 -terpyridine have been reviewed previously 158). 

A further influence on electron exchange is the ligand type present. Thus with bidentate aromatic 2,2 -bipyridine and 1,10-phenanthroline ligands (L), the [RuL3] + + self-exchange rate constants are 1 x 10 sec (95, 96). In the case of the copper proteins the imidazole and S-donor ligands presumably have similar beneficial effects. 

Allyl vinyl ethers may be prepared via stereospecific copper-catalyzed coupling of allyl alcohols and vinyl halides. For example, the copper catalyst derived from the tetramethyl 1,10-phenanthroline ligand shown below facilitates C-0 bond formation between ( )-vinyl iodides and allyl alcohols when the reaction mixture is heated in the presence of air. ... 

Oxidations. Various primary and secondary alcohols are oxidized to give aldehydes and ketones by PdfOAcl -O -pyridine in the presence of 3A molecular sieves. Modified Wacker processes which obviate copper and chloride employ the Pd(OAcl -02 system and a water-soluble 1, 10-phenanthroline ligand or polypyrrole as redox-active ligand.- ... 

Dehaen and coworkers utiUzed carbazole dendrons attached to 1,10-phenanthroline ligands (phen) to construct a dendrimer around a Ru(ll) core (12, Scheme 6) (12]. Absorbance transitions assigned to carbazole, phen, and carbazole-to-phen CT transitions aU gave rise to emission from the Ru(ll) core, providing yet another hght-harvesting dendrimer, which illustrates the antennae effect. 

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