Dipyridyl Compounds Research Articles

How is the Observation of High-Order Overtones and Combinations Elucidated by the Charge-Transfer Mechanism in SERS?

The charge-transfer chemical mechanism is responsible for altering the molecular spectral pattern and providing valuable insights into the properties of adsorbates. The impact of charge transfer becomes more pronounced in SERS spectra when CT states can gain intensity through vibronic coupling with high-intensity excitations. Experimental SERS spectra of diamino molecules, such as 4,4'-diaminostilbene (DAS) and 4,4'-diaminotolane (DAT), featuring bright CT transitions, have been compared to dipyridyl compounds, such as 1,2-bis(4-pyridyl) ethylene (BPE) and 1,2-di(4-pyridyl) acetylene (DPA), characterized by nearly dark CT excitations. This comparison aims to elucidate the effect of CT transitions on the presence of overtones and combination bands. We explain this distinction using Albrecht's formalism for resonance Raman spectroscopy within the framework of path integral time-dependent density functional theory considering the Herzberg-Teller corrections. It is worth noting that the energy gap between the highest occupied metallic orbital and the lowest unoccupied molecular orbital in diamino derivatives is noticeably smaller than in compounds featuring two pyridyl rings. The high-intensity SERS-CT spectra for diamino derivatives, primarily driven by the Albrecht A term, were acquired and used to elucidate the experimental observation of high-order modes with a significant Huang-Rhys factor. Conversely, the absolute intensity of SERS-CT for dipyridyl compounds is at least 106 times smaller than that for diamines, and the C term makes a significant contribution, explaining the silent overtones.

Linking Bridged Tetracopper Complexes with Neutral Dipyridyl Compounds to Coordination Polymers and Discrete Metalacages

The bridged tetracopper(I) complex [{Cu2(μ‐dppm)2}2(μ‐(1,3‐O2CC6H4 (CO2 )2)](BF4 )2 (2(BF4 )2) was prepared. This complex and the neutral dipyridyl compounds (NN; NN = 4,4′‐bipyridine (bpy), 1,2‐bis(4‐pyridyl)ethane (bpa), 4,4′‐trimethylenedipyridine (tmp)) can form dynamic equilibria in CH2Cl2 . From the equilibrium mixtures containing 2(BF4 )2 and NN with 2(BF4 )2/NN = 1:1, different supramolecular compounds were obtained as single crystals, and their structure were determined by X‐ray crystallography. The flexibility of NN is found to be important in determining the outcome of the reactions with a rigid bpy, leading to the formation of the coordination polymer [{Cu2(μ‐dppm)2}2(μ‐1,3‐C6H4 (CO2 )2)(μ‐bpy)] n (BF4 )2n (3(BF4 )2n ), whereas with flexible bpa and tmp direct the formation of the metalacages [{Cu2(μ‐dppm)2}2(μ‐1,3‐C6H4 (CO2 )2)(μ‐NN)](BF4 )2 (NN = bpa, 4(BF4 )2; tmp, 5(BF4 )2), respectively, as supported by density functional theory (DFT) calculation results.

Linking Tribridged Dicopper Complexes with Neutral Dipyridyl Compounds to Coordination Oligomers and Polymers

Linking Tribridged Dicopper Complexes with Neutral Dipyridyl Compounds to Coordination Oligomers and Polymers

Copolymeric films obtained by electropolymerization of porphyrins and dipyridyl-spacers including Dawson-type polyoxometalates

This paper reports the formation of hybrid polyoxometalate-porphyrin copolymeric films obtained by the electro-oxidation of zinc-β-octaethylporphyrin (ZnOEP) in the presence of a functionalized Dawson-type polyoxometalate bearing two pyridyl groups (POMdbme3,3, Py-POM-Py) which will be compared to the copolymer obtained from ZnOEP and a dipyridyl compound without POM (ibme3,3). The resulting film has been characterized by UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. Electrochemical quartz crystal microbalance was employed to investigate the poly-porphyrin-POMs deposition mass.Graphical Abstract

Fixation of Multilayered Structures of Liquid-Crystalline 2:1 Complexes of Benzoic Acid Derivatives and Dipyridyl Compounds and the Effect of Nanopillars on Removal of the Dipyridyl Molecules from the Polymers

A polymerizable benzoic acid derivative, 3,5-bis(propenoyloxymethyl)-4- hexadecyloxybenzoic acid (1), was synthesized and complexed in a molar ratio of 2:1 with each of the dipyridyl compounds 4,4′-bipyridyl (2a), 1,2-dipyridylethane (2b), 1,2-dipyridylethene (2c), and 1,3-dipyridylpropane (2d). All of these 2:1 complexes exhibited a monotropic smectic A liquid crystal phase. Complex compound 12·2b (denoted 3b) in the liquid crystal phase was photopolymerized by UV irradiation. As the polymerization proceeded, the multilayered structure of 3b was maintained. In addition, the polymerizations of 3b containing the polymerizable rodlike compound PL at concentrations of 5 and 10 mol % also proceeded in the smectic A phases while maintaining their multilayered structures. By treatment with dilute hydrochloric acid for 216 h, all of the 2b molecules were removed from the polymer obtained from a mixture of 3b and PL in a molar ratio of 90:10, though only 50% of 2b could be removed from the polymer obtained from p...

Formation of Boronate Ester Polymers with Efficient Intrastrand Charge‐Transfer Transitions by Three‐Component Reactions (Eur. J. Inorg. Chem. 33/2007)

AbstractThe cover picture shows the formation of deeply colored boronate ester polymers by three‐component reactions of boronic acids with 1,2,4,5‐tetrahydroxybenzene and dipyridyl compounds. The strong color of the polymers is due to efficient intrastrand charge transfer excitations from the tetraoxobenzene to the dipyridyl linker. Upon dissolution of the polymers in hot chloroform, most of the B–N connections are broken, which indicates that polymer formation is a reversible process. More details on these reactions are described in the article by K. Severin et al. on page 5177 ff.

A Search for Predictable Hydrogen-Bonding Synthons in Cocrystallization of Unusual Organic Acids with a Bent Dipyridine

A bent dipyridyl compound, 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo), was employed to crystallize with 1,4-cyclohexanedicarboxylic acid (H2chdc), hydroquinone, citric acid (H4ca·H2O), barbituric acid, and ferrocene dicarboxylic acid (H2Fc) under general conditions, affording binary cocrystals [(H2chdc)·(4-bpo)] (1), [(hydroquinone)·(4-bpo)2] (2), [(H4ca)·(4-bpo)] (3), [(barbituric acid)·(4-bpo)] (4), and [(HFc)·(H-4-bpo)] (5) in high yield. X-ray single-crystal structures of these compounds reveal that a supramolecular synthon [ (7)] containing classical O−H···N and weak C−H···O interactions, usually observed in organic cocrystals of carboxylic acid and heterocyclic base, is again involved in constructing the hydrogen-bonding networks of 1, 3, and 5. Its ionic analogous synthon [consisting of strong N−H···O and weak C−H···O, (7)] also appears in the partly charge-transfer salt 5. For 2, only hydroxyl of the hydroquinone component can act as the hydrogen-bonding contributor, giving a strong O−H···N bond ...

Synthesis and characterization of novel dipyridylbenzothiadiazole and bisbenzothiadiazole derivatives.

Novel dipyridyl compounds containing a mono- and bisbenzothiadiazole unit were synthesized using the Stille coupling reaction. Their pyridinium salts, viologen analogues, were also prepared by the N-alkylation. The X-ray crystallographic analysis of the compounds containing a benzothiadiazole ring revealed nonplanar molecular structures and unique crystal structures depending on the nitrogen positions. The dipyridyl compounds are efficient fluorophores with high electron affinity. The derivative afforded complexes with chloranilic acid and cyanuric acid composed of hydrogen bonding networks. The methyl viologen analogues showed two-stage one-electron reduction waves.

Toxicity of Dipyridyl Compounds and Related Compounds

ABSTRACTFive dipyridyl isomers, 2,2′-, 2,3′-, 2,4′-, 3,3′-, and 4,4′-dipyridyl, are products resulting from the pyrolytic degradation of tobacco products and degradation of the herbicide paraquat, and therefore may be present in the environment. In this article, the toxicological properties of these dipyridyl isomers in humans and animals are reviewed. Epidemiological studies suggest that cancerous skin lesions in workers involved in the manufacturing of paraquat may be associated with exposure to dipyridyl compounds. Experimental animal studies suggest that dipyridyl isomers may have several toxicological effects. Three of the dipyridyl isomers (the 2,2′, 2,4′, and 4,4′ isomers) appear to be inducers of some metabolic enzymes. The 2,2′-dipyridyl isomer, an iron chelator, appears to influence vasospasm in primate models of stroke. The cytotoxic effects of 2,2′-dipyridyl on several leukemia cell lines have been reported, and a potent teratogenic effect of 2,2′-dipyridyl has been observed in rats. Based on the results of paraquat studies in experimental animal models, it has been proposed that paraquat may have deleterious effects on dopaminergic neurons. These findings support the epidemiological evidence that paraquat exposure may be associated with the development of Parkinson's disease. Studies designed to determine an association between paraquat exposure and Parkinson's disease are complicated by the possibility that metabolic changes may influence the neurotoxicity of paraquat and/or its metabolites. Preliminary unpublished data in mice show that 300-mg/kg doses of 2,2′-dipyridyl are neurotoxic, and 300-mg/kg doses of 2,4′- and 4,4′-dipyridyls are lethal. These results are consistent with earlier studies in Sherman rats using high 2,2′- and 4,4′-dipyridyl doses. New studies are needed to further explore the toxicological properties of dipyridyls and their potential public health impact.

Unusual Hydrogen-bonding Networks Consisting of π-Extended 4,4′-Bipyridines and Chloranilic Acid

Hydrogen-bonding networks of π-extended 4,4′-bipyridines, 2,5-di(4-pyridyl)thiophene (1), 2,5-di(4-pyridyl)furan (2) and 1,4-di(4-pyridyl)benzene (3) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, CA) have been investigated. The dipyridyl compounds afforded complexes 4 [(dication of 1)·(monoanion of CA)2], 5 [(dication of 2)·(dianion of CA)·(MeOH)] and 6 [(3)·(dication of 3)·(dianion of CA)·(H2O)6] with CA. X-ray structure analyses revealed the formation of unusual molecular tape and sheet structures involving N–H ⃛O, O–H ⃛O, C–H ⃛O and N–H ⃛N hydrogen bonds, where the aromatic spacer groups play an important role in constructing the unique crystal structures.

Crystal engineering using anilic acids and dipyridyl compounds through a new supramolecular synthon.

The anilic acids, 2,5-dihydroxy-1,4-benzoquinone (1a), 2,5-dibromo-3,6-dihydroxy-1,4-benzoquinone (bromanilic acid; 1b), 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid; 1c), and 2,5-dicyano-3,6-dihydroxy-1,4-benzoquinone (cyananilic acid; 1d), were cocrystallized with rigid organic ligands containing two pyridine rings, 2,4-bipyridine (2a), 4,4'-bipyridine (2b), 1,2-bis(2-pyridyl)ethylene (3a), 1,2-bis(4-pyridyl)ethylene (3b), 2,2'-dipyridylacetylene (4a), 3,3'-dipyridylacetylene (4b), and 4,4'-dipyridylacetylene (4c). Fourteen complexes 5-18 were obtained as single crystals, and their crystal structures were successfully determined by X-ray analysis. All complexes except those with 2a are 1:1 and are composed of an infinite linear or zigzag tape structure, the formation of which is ascribed to intermolecular O-H...N, N(+)-H...O, or N(+)-H...O(-) hydrogen bonds or a combination of these between the anilic acids and the dipyridyl compounds. In the complexes 5 and 6, no infinite tape structure is observed although the molecular units connected by a similar hydrogen-bonding pattern are formed. For the 1:1 complexes, we have found two types of stacking arrangements, segregated stacks (7, 9, 12-15, 18) and alternated ones (8, 10, 11, 16, 17). In the complexes of 1c with the series of dipyridylacetylenes 4 (14, 15, 17), the neutral, dication, and monocaction states are formed depending on the nitrogen positions, which can be attributed to the different basicity of the pyridyl groups.

Polymers with pendent functional groups: VII. Polysaccharide derivatives containing viologen groups

The paper presents the synthesis of new polysaccharide derivatives containing viologen groups, by reaction of chloroacetylated crosslinked dextran microparticles with dipyridyl compounds as: 4,4 ′ dipyridyl, N- n-octyldipyridinium chloride and N-benzyldipyridinium chloride. The influence of the reaction conditions on the substitution degree with dipyridyl groups was discussed and a reaction mechanism was proposed. Some preliminary studies concerning antimicrobial activity of the polymeric dipyridyl compounds were also reported.

Concurrent induction of rat hepatic microsomal cytochrome P450 and haem oxygenase by 2,2'-dipyridyl ketone: comparison with the effect of 2,2'-dipyridyl amine

1. The effect of 2,2'-dipyridyl ketone and 2,2'-dipyridyl amine on the induction of hepatic microsomal cytochrome P450 (P450) and heme oxygenase was compared, and their effects on five different P450 isoforms (P4501A1, 3A2, 2B1, 2E1 and 2C11) in rat were examined. 2. Treatment of rat with 2,2-dipyridyl amine resulted in the marked induction of haem oxygenase to about seven-fold of the controls with a decrease in P450 content. 2,2-'Dipyridyl ketone produced concomitant induction of both P450 and haem oxygenase activity in a dose- and time-dependent manner without showing any sex differences. 3. Immunoblot analysis revealed that 2,2'-dipyridyl ketone slightly increased CYP2E1 and CYP3A2 at low doses, but not at high dose levels. There was no effect on P4502C11. P4502B1 was induced by the treatment with 2,2'-dipyridyl ketone in a dose-dependent manner. 4. These results indicate that dipyridyl compounds having different bridges between two aromatic moieties act as differential inducers of hepatic microsomal P450s and haem oxygenase.

Design of molecular solids: utility of the hydroxyl functionality as a predictable design element

In order to design a new molecular solid one needs a library of functional groups that will self assemble into predictable structural patterns. To test the utility of the hydroxyl group for this purpose, a series of ureas and oxalamides with side-arm substituents containing the hydroxyl functionality were prepared. X-Ray crystallographic analysis of five such compounds revealed a variety of structural features indicating that the hydroxyl group alone was not a predictable design element. However, when a pair of co-crystals of dihydroxyl substituted oxalamides with dipyridyl compounds were prepared, supramolecular structures were prepared consistent with predictions. This suggests that the hydroxyl group coupled to a pyridine hydrogen-bond acceptor is a useful design element for the preparation of molecular networks.

Differential effects of 3 dipyridyl isomers on hepatic microsomal cytochrome P450 and heme oxygenase in rats

We compared the effects of 3 dipyridyl isomers, 2,2′-dipyridyl, 2,4′-dipyridyl and 4,4′-dipyridyl, on hepatic microsomal heme oxygenase and drug-metabolizing enzyme activities in male rats. 2,2′-Dipyridyl increased cytochrome P450 (P450) content at lower doses, but decreased with increasing dose levels. Immunoblot analysis revealed that 2,2′-dipyridyl did not induce both P450 1A1/2 and P450 2B1/2, in contrast to 2,4′- and 4,4′-dipyridyls, both of which were inducers of either P450 1A1/2 and/or P450 2B1/2. Some drug-metabolizing enzyme activities gradually declined with the increasing dose level of 2,2′-dipyridyl. 2,2′-Dipyridyl was able to induce hepatic microsomal heme oxygenase in a dose-dependent manner, but 2,4′- and 4,4′-dipyridyls did not, even at the highest dose (0.80 mmol/kg) examined. Treatment of rats with 2,2′-dipyridyl resulted in the increase of glutathione (GSH) content in a dose-dependent manner, but not 4-substituted isomers. A time course study with 2,2′-dipyridyl revealed that it produced a significant decrease in hepatic GSH content at early time periods (2–6 h) after its administration with an inverse increase in heme oxygenase activity. The present investigation has revealed that in contrast to the induction of P450 by 4-substituted dipyridyl compounds, 2,2′-dipyridyl is a novel inducer of hepatic microsomal heme oxygenase, together with the change in hepatic GSH content. This study would provide information on the differential effects of simple dipyridyl isomers on hepatic enzymes involved in heme and drug metabolism.

Lysine residues in the coenzyme-binding region of mouse lung carbonyl reductase.

Tetrameric carbonyl reductase (CR, EC 1.1.1.184) of guinea-pig, mouse and pig lung differs from CRs of other mammalian tissues in subunit structure, broad substrate specificity for aromatic and aliphatic carbonyl compounds, reversibility of the reaction and sensitivity to pyrazole (Nakayama et al., 1982, 1986; Oritani et al., 1992). It is also uniquely activated by fatty acids and dipyridyl compounds (Hara et al., 1992a, 1993). The cDNA for pig lung has been cloned (Nakanishi et al., 1993). The enzyme is composed of 244 amino acids, and is structurally related to members of the short-chain alcohol dehydrogenase (SCAD) family, which includes eucaryotic and procaryotic enzymes with different substrate specificity (Persson et al., 1990; Neidle et al, 1992; Krozowski, 1992).

Involvement of Fe3+(dipyridyl)3compounds in Fe3+reduction reactions

Abstract Much of the methodology used in the measurement of rhizosphere iron reduction involves the chelation of ferrous ions by BPDS (batho‐phenanthrolinedisulfonic acid) and other related dipyridyl derivatives. This technique was applied to monitor the rates of iron reduction by the root system of citrus seedlings at both slightly alkaline and acidic pH. The results of this Study demonstrated unusual effects of these dipyridyl compounds on the rates of iron reduction. These effects included a strong dependence on both the concentration and the type of the dipyridyl compound present. Also affecting the rates of iron reduction were the presence of divalent metal ions. Iron (Fe3+) chelates of HEDTA and EDDHA, both of which are common sources of soluble iron in nutrient solutions, dramatically iniibited iron reduction by the cituus roots. These feateres of the iron reduction reactions, monitored by the use of dipyridyl compounds, are consistent with the involvement of Fe3+ (dipyridyl)3‐type chelates as the actual electron acceptors. This role of dipyridyl compounds, such as BPDS, in rhizosphere iron reduction measurements, demonstrates the need to accurately evaluate the actual electron‐transfer activities being monitored.

Determination of moisture in ketones and lower carboxylic acids by new Karl Fischer coulometric reagent.

A new odorless Karl Fischer coulometric reagent was tested for determining the moisture in ketones and lower carboxylic acids. The mixture of aminopyridine compound and dipyridyl compound was used as odorless amine, instead of pyridine. Coulometric reagent which contains methanol produces water by reacting with ketones or lower carboxylic acids. Therefore the moisture contained in them can not be determined by such a reagent. Methanolfree coulometric reagent was studied for avoiding these interfering reactions. The mixture of chloroform and ethylene glycol monomethyl ether was found to be the most suitable solvent of the reagent for determining the moisture in ketones and lower carboxylic acids. Determination of moisture in ketone and lower carboxylic acids was feasible even at room temperature.

Synthesis of 7, 7-diaryl-4, 5, 6, 7-tetrahydroimidazo-[4, 5-c]pyridines

The synthesis and characterization of various 7, 7-diaryl-4, 5, 6, 7-tetrahydroimidazo-[4, 5-c]pyridines are reported. Convulsant activity was observed with a dipyridyl compound.

An improved synthesis of gliamilide®, a high‐potency sulfamylurea hypoglycemic agent

AbstractAn efficient synthesis of the sulfamylurea, Gliamilide®, is described, which involves as a key feature the selective reduction of the more basic alkyl‐substituted pyridine ring in the mono‐hydrochloride salt of dipyridyl compound 11 to form 12 without affecting the 2‐methoxy‐nicotinamide moiety.