4,4’-Bipyridinium

The tria2ine family of herbicides appeared in and after 1955, and the bipyridiniums in 1960. In 1967, two new chemical herbicides (1) were registered under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The number of new registrations swelled to 11 in 1975 and subsequendy dropped to three in 1990 and two in 1991. 

Light and photosynthetic electron transport convert DPEs into free radicals of undetermined stmcture. The radicals produced in the presence of the bipyridinium and DPE herbicides decrease leaf chlorophyll and carotenoid content and initiate general destmction of chloroplasts with concomitant formation of short-chain hydrocarbons from polyunsaturated fatty acids (37,97). 

Bipyridiniums. The bipyridinium herbicides (Table 2), paraquat and diquat, ate nonselective contact herbicides and crop desiccants. Diquat is also used as a general aquatic herbicide (2,296). Bipyridinium herbicides are organic cations and are retained ia the soil complex via cation exchange. They are strongly sorbed to most soils and are not readily desorbed (332). Both paraquat and diquat are not readily leached (293). 

L. A. Summers, The Bipyridinium Herbicides, Academic Press, Inc., New York, 1980. 

Bipyridinium chlorochromate [76899-34-8] M 292.6. Washed with cold cone HCl then H2O (sintered glass funnel) and dried in vacuum (CaCl2) to a free flowing yellow-brown powder. Stored in the dark. [Synthesis 691 1980 Synth Commun 10 951 1980.] SUSPECTED CARCINOGEN. 

These authors also list thermodynamic quantities for many other amines. A// , at 25°C, ranges from 3.37 kcal mol for the very weakly basic 2,2 -bipyridinium to 13.88 kcal mol for -butylammonium for TRIS at 25°C, A// = 11.38 kcal mol . ... 

In this type of cleavage reaction, it appears that the axial benzoate is the preferred product. If water is excluded from the reaction, a bromo benzoate is obtained.The highly oxidizing medium of 2,2 -bipyridinium chlorochromate and MCPBA in CH2CI2 at rt for 36 h effects a similar conversion of benzylidene acetals to hydroxy benzoates in 25-72% yield. ... 

Derivatives of 4,4 -bipyridinium dication in electrochromic techniques 96CLY135. 

Fig. 3-4. (A) Changes in chemical shift of protons of cyclophane -CH - groups between bipyridinium and phenyl in H NMR spectra of 3 as a function of (R)-DOPA concentration (a) 0, (b) 0.111, and (c) 0.272 mol (B) Change in chemical shift plotted against the analytical concentration of (R)- and (5)-DOPA. The solid line is calculated for 1 1 host - guest complexation. (Reprinted with permission from ref. [79]. Copyright 1998, American Chemical Society.)...

Bipyridinium, lV-(benzylpolyvinyl)-AP-mcthyl-in photochemical hydrogen production from water, 6, 505... 

More recently, Kim et al. synthesized dendritic [n] pseudorotaxane based on the stable charge-transfer complex formation inside cucurbit[8]uril (CB[8j) (Fig. 17) [59]. Reaction of triply branched molecule 47 containing an electron deficient bipyridinium unit on each branch, and three equiv of CB[8] forms branched [4] pseudorotaxane 48 which has been characterized by NMR and ESI mass spectrometry. Addition of three equivalents of electron-rich dihydrox-ynaphthalene 49 produces branched [4]rotaxane 50, which is stabilized by charge-transfer interactions between the bipyridinium unit and dihydroxy-naphthalene inside CB[8]. No dethreading of CB[8] is observed in solution. Reaction of [4] pseudorotaxane 48 with three equiv of triply branched molecule 51 having an electron donor unit on one arm and CB[6] threaded on a diaminobutane unit on each of two remaining arms produced dendritic [ 10] pseudorotaxane 52 which may be considered to be a second generation dendritic pseudorotaxane. 

Fig. 3. Haptens and multivalent antigens prepared in this syudy. The viologen derivative, 4,4 -bipyridinium, l-(carboxypentyl)-l -methyl-dichloride (1), divalent antigen 2, and trivalent antigen 3. Anti-porphyrin antibodies were elicited for [5-(4-carboxyphenyl)-10,15,20-tris-(4-methylpyridyl)]porphine (3MPylC) or meso-tetrakis(4-carboxyphenyl)porphine (TCPP). meso-Tetrakis(4-methylpyridyl)porphine (TMPyP) was used to investigate the specificity of the antibody dendrimer for porphyrins...

Organic Molecules It can be seen from our earlier discussion that the presence of a transition metal ion is not always required for an electrochromic effect. Indeed, many organic molecules can yield colored products as a result of reversible reduction or oxidation. 4,4 -Bipyridinium salts are the best known example of such compounds. These compounds can be prepared, stored, and purchased in colorless dicationic form (bipm +). One electron reduction of the dication leads to the intensely colored radical cation (bipm+ ). Such radical cations exist in equilibrium with their dimers (bipm ). In the case of methyl viologen, the radical cation is blue and the dimer is red. By varying the substient group in the molecule, different colors can be obtained. 

In their first step towards building dendritic rotaxanes Stoddart et al. [140] reported the construction of such materials via a so-called slipping method (Fig. 24). Thus, treatment of bisparaphenylene-34-crown-10 (BPP34C10) with tris(bipyridinium) compound 54 at 50 °C in acetonitrile for 10 days afforded mono-, di-, and tris-rotaxanes 55, 56, and 57, respectively. ES-MS was used to determine the molar masses of these macromolecules while upfield shifts in the... 

H NMR spectra for both hydroquinone and bipyridinium protons indicated 7r-7r interactions. 

In a recent report [141] Stoddart et al. reported a new class of rotaxanes with dendritic stoppers by using a so-called threading approach (Fig. 25). Alkylation of bipyridinium based units with Frechet s third tier branched aryl ethereal dendron, in the presence of BPP34C10 afforded 58 as one of the products. Variable temperature H-NMR spectroscopy in different NMR solvents helped determine the novel shuttling process of BPP34C10 from one bipyridinium unit to the other in 58. The dendritic framework of 58 assists in its solubility in a wide range of solvents. 

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