2,2 -dipyridyl structure

Stnictue. The dipyridyl structure is uraque among the herbicides (see lafale 20-1). 

Macrocyclic receptors made up of two, four or six zinc porphyrins covalently connected have been used as hosts for di- and tetrapyridyl porphyrins, and the association constants are in the range 105-106 M-1, reflecting the cooperative multipoint interactions (84-86). These host-guest complexes have well-defined structures, like Lindsey s wheel and spoke architecture (70, Fig. 27a), and have been used to study energy and electron transfer between the chromophores. A similar host-guest complex (71, Fig. 27b) was reported by Slone and Hupp (87), but in this case the host was itself a supramolecular structure. Four 5,15-dipyridyl zinc porphyrins coordinated to four rhenium complexes form the walls of a macrocyclic molecular square. This host binds meso-tetrapyridyl and 5,15-dipyridyl porphyrins with association constants of 4 x 107 M-1 and 3 x 106 M-1 respectively. 

A A -coordi nation was found in the zinc complex of 2,2 -dipyridyl diselenide, [ZnLCl2].214 The tridentate ligand 6-(2-aminophenyl)-2,2 -bipyridine contains two pyridyl and one aniline donor ligand to form a complex of the form [ZnL2]2+. The X-ray structure shows a distorted octahedral metal center with each ligand twisting from planar to accommodate the meridional binding.215... 

The potassium salt of the 2,2 -dipyridyl acetylene anion-radical represents another important example. In this case, the spin and charge are localized in the framework of N-C-C=C-C-N fragment. The atomic charge on each nitrogen atom is -0.447, that is, close to unity in total. The energy of this ion pair is minimal when the potassium counterion is located midway between the two rather close nitrogen lone pairs. Such a structure is consistent with the fact that the ESR spectrum of this species is almost insensitive to temperature. It means that the counterion does not hop between two remote sites of the anion-radical (Choua et al. 1999). 

Other coordination polyhedra based on bicapped dodecahedra, but having Dz symmetry, have been found for orthorhombic Phcn, Z =4) crystals of M(dip)2 (N03)3 (M=La, Tb and dip = 2,2 -dipyridyl) complexes (27(5, 277). Both La(III) and Tb(III) complexes have the same structure and this might be taken as evidence for the maintenance of the structure at least until Tb in the series. Sinha 218) have prepared the heavy lanthanide-bis-dipyridyl-trisnitrate complexes and the infrared studies 218, 219) showed no difference in the infrared spectra within the series, both ligands (dipyridyl and nitrate) being coordinated. 

There are six bipyridines whose structures are 2,2 -l, 2,3 -2, 2,4 -3, 3,3 -4, 3,4 -5, and 4,4 -6. The term bipyridine is in accord with current Chemical Abstracts nomenclature, although the compounds have also been named as bipyridyls and dipyridyls. 

Several extensions of these reactions are possible with respect to the electrophilic reagent as well as to the structure of the adduct. Thus functionalized alkyl groups, such as 2-hydroxyethyl and 2-hydroxy-2-phenylethyl, can be introduced into the pyridine ring at the position by treating l-lithio-2-phenyI-l,2-dihydropyridine with ethylene epoxide and styrene epoxide, respectively.144 When polyhalides such as CF3I are used, bis-(substituted-pyridyl)methanes and the dimeric substituted dipyridyls are obtained along with other products.144... 

Iron forms polydentate chelate compounds with a number of organic substances, including the oxalates, dipyridyl and orthophenaiilhroline, Such a structure is found in hemoglobin. 

The coupling can be catalysed by the presence of Fe(III) or Co(ll) but is most efficiently induced by the dipyridyl complex of Ni(II) chloride, as described by Yamamoto et al.52). It is also efficiently promoted by l,4-dichoro-2-butene, as described by Taylor et al.53). The structures of these Yamamoto polyphenylenes are discussed in Sect. 3 at this point it is sufficient to note that they are yellow/brown infusible powders, apparently having a high degree of p-coupling but relatively short (10—12 rings) chain lengths. 

Stang et al. [94JA4981, 9403776, 95JA1667, 95JA6273] described the self assembly of a series of unique cationic, tetranuclear, Pd(II)- and Pt(II)-based macrocyclic squares (e.g., 25), utilizing different bidentates as the sides of these structures. The similar self-assembly complexation of dipyridyl porphyrins by cis- and tran.v-substituted Pd(II) or Pt(II) ions possessing square planar coordination afforded multiporphyrin arrays with a square... 

K. Broctdehurst, . M. Crook, and M. KJentan. The mutability of stem bromelain evidence for perturbation by structural transitions of (he parameters that characterize the reaction of the essential thiol group of bromelain with 2,2 -dipyridyl disulphide. J. Biochem. 128379 (1972). 

A recent paper describes the reaction of 2-pyridone with sulfur dichloride when these are boiled in benzene for a week the 5,5 -dipyridyl sulfide (80) is formed in 13% yield. The structure of 80 was confirmed by its ultraviolet and nuclear magnetic resonance (NMR) spectra.173 3-Hydroxypyridine gives a poorly defined and apparently high polymeric substance under these conditions, whereas 4-pyridone is said not to react. 

It will be seen (Section 11.6.1) that metal electrodes can be usefully modified by adsorbing on them organic compounds of a structure suited to some specific task. For example, if a Pt electrode has adsorbed upon it a monolayer consisting of 4,4 -dipyridyl, then... 

The interaction between tris(2,2 -dipyridyl)ruthenium(II) with poly(p-styrene sulfonate) [80] due to the outer-sphere cooperative processes yields the following structures ... 

Polymeric Catalysts such as porphirin-containing poly-(L-phenylalanine)-Fe(III) complex in the dehydrogenation of p-phenylenediamine (132), poly(L-lysine)-protoporphirin Fe(III)-4,4 -dipyridyl complex in the oxidation of cytochrome (133), poly(L-lysine)-Cu(II) complex in the hydrolysis of oligophosphate (134), and poly(L-lysine)-Cu(II) complex in the oxidation of 3,4-dioxyphenylalanine and in the hydrolysis of phenylalanine (135-137) have their own structures. 

There has been considerable interest in the chemistry and electronic structures of cobalt and iron complexes of a s-l,2-disub-stituted ethene-1,2-dithiol1 2 and their Lewis base adducts.3-5 The complexes, and their Lewis base adducts which may contain pyridine, phosphines, NO, dipyridyl (2,2/-bipyridine), etc., are capable of undergoing reversible one-electron transfer reactions, thereby generating a series of complex ions differing from each other by only one unit of electric charge. 

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