Pyridine electronic spectra

Diamonium pentachlorooxomolybdate(V) is an emerald green solid, stable in air. It is hygroscopic and should be stored in a stoppered vial in a desiccator. In concentrated HC1, a solution (> 10M) of the compound is green. In dilute HC1 (< 10M) the solution is greenish-brown or borwnish-red. The compound undergoes extensive ionic dissociation in aqueous solution. It is insoluble in benzene, chloroform, dichloromethane, and carbon tetrachloride. It is soluble (with decomposition) in ethanol, methanol, acetone, and pyridine a white solid of ammonium chloride precipitates from all these solutions immediately. The compound dissolves in dimethyl sulfoxide without decomposition. The electronic spectrum in 10 M HC1 contains the following absorptions 14,100(emax = 11), 22,500(emax = 10), 28,200(emax = 570),... 

VO(tpp)-CH3OH, is slightly soluble in CHC13 and CH2C12, less soluble in pyridine, and insoluble in water and alcohols. The material is stable in the solid state and stable in solution when protected from the light. The electronic spectrum contains bands at 423, 508, 547, and 581 nm with molar absorptivities of 50,100, 4900, 22,500 and 4160, respectively. 

Mesohemin IX prepared by this method shows a single band on polyamide tic (benzene/methanol/formic acid, 110 15 1 and methanol/acetic acid 100 2)10 and on silica gel tic14 (benzene/methanol/formic add, 110 30 1). The electronic spectrum of the pyridine hemochrome, prepared by reducing the mesohemin (in pyridine) with an aqueous solution of sodium dithionite, contains the bands (4 N pyridine, 0.2 N KOH) Xmax 407.5, 516, 546.2 nm. e 139.5,20.9,35.8 (mAT1). 

Octamethyltetrabenzoporphinato(2-)]cobalt(Il) is a green-blue powder that is stable towards atmospheric oxidation in the solid state. The compound is readily soluble in pyridine bases and tetrahydrofuran, and to a lesser extent in diethyl ether, benzene, ethanol, and acetone. The electronic spectrum in pyridine shows bands at 320 (e = 13,200), 455 (e = 71300), and 645 nm (e = 36,700). 

Phthalocyaninato(2-)] iron(II) is a dark blue, thermally stable solid that can be sublimed in vacuo at 300°. It is very soluble in pyridine, giving deep blue solutions of the bis(pyridine) adducts. It also forms an unstable purple hexaaniline adduct when dissolved in aniline. It is soluble in concentrated sulfuric add and dimethyl sulfoxide (slightly) but is insoluble in most other organic solvents. The iron(II) complex, unlike the corresponding iron(II) porphines, is relatively stable toward oxidation to the iron (III) state. The electronic spectrum shows the following absorption bands (1-chloronaphthalene solution) 595 (e = 16,000), 630 (e = 17,000), 658 (e = 63,000) (pyridine solution) 333 (e = 45,000), 415 (e = 15,000), 395 (e = 2000), 658 nm (e = 8000). 

The association constant of pyridazine with ethanol was found to be 4.9 (from electronic absorption spectra) and 6.8 (infrared absorption spectra), and the corresponding values for the strength of the hydrogen bond are 4.2 and 4.6 kcal. The hydrogen-bonded form of P3n-idazine was considered to comprise one alcohol at one azine-nitrogen at small mole ratios of alcohol to azine and to involve the second nitrogen at high mole ratios (an additional shift in the electronic spectrum. The association constants (3.1-3.8) of pyridine, quinoline, and isoquinoline with methanol in carbon tetrachloride have been determined by infrared spectroscopy. 

The extraordinary enhancement of the Raman spectrum of pyridine adsorbed on silver has resulted in the investigation of pyridine as a candidate for possible enhancement on other metals. More recently, SERS has been used to probe the adsorption of molecules on metals that are of catalytic importance. For example, SERS spectra have been collected of pyridine adsorbed on metallic rhodium in the first demonstration of surface-enhancement from metallic rhodium. While the enhancement of pyridine on silver is thought to arise from an electrodynamic enhancement, the enhancement of the pyridine Raman spectrum by rhodium is thought to arise from a chemical effect since rhodium, unlike silver, is not a free electron metal. 

The product has appreciable solubility in dichloromethane and more limited solubility in both benzene and pyridine. The Mossbauer spectrum and electronic spectrum of this clathrochelate are similar to those of other iron tri(glyoxime) cages.2 The compounds show an intense absorption band at 22,200 cm 1(e = 17,900). Several dominant bands in the infrared spectrum along with their proposed assignments are 1589 cm"1 (C=N stretch) 1495 cm"1 (C—Cand C=N stretch) 1234 and 1064 cm"1 (N—O stretch), and 1209 cm"1 (B—O stretch).3 In dichloromethane-d2, the pmr spectrum consists of two unresolved triplets (relative area = 24) at 1.78 and 2.91 ppm downfield from internal TMS and two multiplets (relative area 10.3) at 7.3 and 7.7 ppm downfield.3 The two multiplets are strikingly similar to that observed in the spectrum of phenyl-... 

An intervalence electron-transfer band, not present in the Fe analogue, was observed in the room temperature electronic spectrum at 13 800cm . Mossbauer spectra indicated distinct Fe" and Fe " sites at 17K while at 300 K a single absorption was observed. The thermal barrier to electron transfer in the trimer was estimated as about 470 cm. Triiron clusters of this type, in the presence of zinc powder, acetic acid, aqueous pyridine and oxygen, are reported " to effect the oxidation of saturated hydrocarbons. The exchange interactions in the series of complexes [Fe2 M 0(02 CMe)spyj] py (M = Mg, Mn, Co, Ni or Zn) which, M = Ni excepted, are isomorphous with the mixed valence complex referred to above have been measured. 

To 1 ] A further theoretical treatment of the electronic spectrum of pyridine has been given 232 ... 

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