2,2 -bipyridyl 2,2 :6 ,2"-terpyridyl

Figure 12.3 Emission spectra of Pt(II) complex 84 (dotted line) and its PtNd2 (solid line), PtEr2 (dashed line), and PtYb2 (dash-dotted line) adducts in dichloromethane solutions at 298 K [129]. (Reprinted with permission from H.B. Xu et aL, Modulation of Pt Ln energy transfer in PtLn2 (Ln = Nd, Er, Yb) complexes with 2,2 -bipyridyl/2,2 6 2 -terpyridyl ethynyl ligands, Crystal Growth and Design, 9, 569, 2009. 2009 American Chemical Society.)...

Chromium(II) complexes of bipyridyls, terpyridyl and the phenanthrolines have been discussed in Section 35.2.2.1. Complexes of the ligands 2-aminomethylpyridine (pic, 2-picolyl-amine) and 8-aminoquinoline (amq), which have one heterocyclic and one amino nitrogen donor atom, have been prepared by methods similar to those in Scheme 10. The bis(amine) complexes are typical high-spin, distorted octahedral complexes, and the mono(amine) complexes, from their antiferromagnetic behaviour and reflectance spectra, are six-coordinate, halide-bridged polymers (Table 15).103 No tris(amine) complexes could be prepared so the attempt to find spin isomeric systems in octahedral chromium(II) systems was unsuccessful ([Cr(en)3]X2 are high-spin and [Cr(bipy)3]X3 and [CrX2(bipy)2] low-spin). 

Complexes of pyridines, bipyridyls, terpyridyls, and other polypyridines differ considerably from those of NH3 and aliphatic amines. They have been intensively studied because many of them have unusual properties for photoinduced energy migrations and charge separation, luminescence, photocatalytic reactions, and water activation. They are also involved in the construction of double-helical complexes, complexes that bind to DNA, and molecular rods and wires28 for fast electron transfers.29... 

Another advance seems likely through the use of zeolites as enzyme mimics.This centers on the reactions of organometallics with zeolite internal surfaces. The best-known example is the production of a [Co (bipyridyl)(terpyridyl)] + complex inside the main cavity of zeohte Y that can selectively and reversibly absorb oxygen from the air. The catalytic potential of a Co phthalocyanine moiety prepared in the Y cavity has also been demonstrated. 

Bipyridyl, terpyridyl, and phenanthroline behave as weak bases, usually forming monoprotonated species. Typical values for the first... 

As a convenient subdivision we may consider complex formation, dissociation, and racemization as one distinct topic i.e., the replacement of solvent as a ligand by bipyridyl, terpyridyl, or phenanthroline the replacement of these ligands by a molecule of solvent or its conj ugate acid or base and the racemization of an optically active complex in a solvent, the solvent usually being water... 

Under this heading we collect together those reactions which do not involve substitution reactions between solvent molecules and bipyridyl, terpyridyl, or phenanthroline. 

Spectra have also been reported for alkaline earth complexes of bipyridyl, terpyridyl, and substituted bipyridyls and phenanthrolines (106,107) of the type M +(L )2. For Be, Mg, Ca, and Sr the spectra show the presence of a ground, orvery lowexcited, triplet state consistent with a divalent metal cation in a tetrahedral environment with one electron on each chelate ligand. The similarity in splittings for Be and Mg is thought to show that interligand interactions prevent the achievement of the small Be + ionic radius. Treatment of bipyridyl with zinc amalgam does... 

Classic A/-heterocychc ligands, eg, bipyridyl (bipy), terpyridyl, imidazole, pyrazine, phenanthroline, piperazine (including alkyl- and aryl-substituted derivatives), and polypyrazol-l-yl-borates (bis, tris, and tetra), have all been found to coordinate Th(IV) chlorides, perchlorates, and nitrates. The tripodal hydrotris(pyrazolyl)borates, HBPz, have been used to stabilize organometaHic complexes (31). Bis-porphyrin Th(IV) "sandwich" complexes have been... 

PArEs with pendant bipyridyl or terpyridyl ligands have also been reported [26]. At 3.08x10" M polymer concentration, a concentration of 1.0x10" M quenched 24 and 25 to 10.9 and 38.2% of their respective initial fluorescence... 

Since complexes of 2,2 -bipyridyl and 1,10-phenanthroline with chromium in oxidation states I and 0 can be obtained by reduction (Scheme 64) of the chromium(n) complexes, these oxidation states will be considered together. Oxidation, as shown in Schemes 65 and 68 of Section 35.4.2.5, gives chromium(III) complexes, which are often best prepared in this way. Earlier work has been extensively reviewed, and few complexes of 2,2 6, 2"-terpyridyl are known.32 A chromium(I) phthalocyanine derivative is mentioned in Section 35.4.9.3. 

Mono and bis 2,2 -bipyridyl and 1,10-phenanthroline complexes of silver(II) have been isolated as red-brown crystals by either peroxydisulfate, anodic or ozone oxidation techniques.497,519 No tris-chelated species have been substantiated,497 although it is worth noting that a 2,2, 2"-terpyridyl bis complex has been isolated and claimed to be a six-coordinate... 

Keywords Bipyridyl Energy transfer Osmium complexes Osmium photochemistry Osmium photophysics Photosubstitution Terpyridyl... 

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