NOPR Collection:

Oxidation of nitrous acid by tris( diimine) iron (III) complexes

Sat, 01 May 1999 00:00:00 GMT

Title: Oxidation of nitrous acid by tris( diimine) iron (III) complexes Authors: Ayoko, G. Adefikayo; Iyun, J. Femi; Faruk, Yusuf U. Abstract: The kinetics of the oxidation of nitrous acid by Fe(LL)₃³⁺ (LL = 2,2' -bipyridine or 1,10 phenanthroline) has been studied in aqueous acidic medium. In the acid range [H⁺] = 0.20-2.00 mol dm^-3,the rate conforms to the equation : Rate = 2k[Fe(LL)₃³⁺][HNO₂ where k = 0.38 and 0.24 mol^-1 dm³ s^-1 I at 25.0°C for the reactions with LL = 1,10 phenanthroltne and 2,2’ -bipyridine respectively. The reactions are thought to occur by the outer sphere mechanism based on (i) substitution inertness of the oxidants, (ii) excellent Marcus-type correlation and (iii ) low ion-pair formation constants. Page(s): 458-461

Effect of steric crowding : Synthesis, spectral characterization and redox studies of isomers of ruthenium(II) N(1)-ethyl-2-(arylazo)- imidazoles

Sat, 01 May 1999 00:00:00 GMT

Title: Effect of steric crowding : Synthesis, spectral characterization and redox studies of isomers of ruthenium(II) N(1)-ethyl-2-(arylazo)- imidazoles Authors: Misra, Tarun Kumar; Das, Debasis; Sinha, Chittaranjan Abstract: Arylazoimidazoles are N,N-chelators (N(imines), N and N(azo), N’). Ruthenium(II) complexes of o-substituted arylazoimidazoles [N( l )-ethyl-2-(7-methylphenylazo)imidazole (L¹), N( l)-ethyl-2-(7,8-dimethylphenylazo)imidazole (L³)] (RuL₂Cl₂) give four different isomers while non-orthosubstituted ligands [N(1)-ethyl-2-(S -methylphenylazo)imid azole(L²), N( l )-ethyl-2-(8,9- dimethylphenylazo)irnidazole (L⁴)] give only two isomers. Considering the coordinating pairs in the order of Cl, N, N', the isomers are characterised as trans-cis-cis (tcc), cis-cis-trans (cct), cis-trans-cis (ctc) and cis-cis-cis (ccc) for [Ru(L¹)₂Cl₂]/[Ru(L³)₂Cl₂. The two isomers for [Ru(L²)₂Cl₂)/[Ru(L⁴)₂Cl₂] are tcc and ctc type. They exhibit t₂(Ru)→π*(L) transition (MLCT) in the visible region and the energy of transition follows the order ccc > ctc > cct > tcc. The ¹H NMR spectra give one quartet and one triplet corresponding to N(1)CH₂-and (N(l)-CH₂)-CH₃respectively in tcc-RuL₂CI₂. The N(l)-CH₂ part in other isomer gives complex spectra of AB type multiplets and the geminal coupling constant follows the order cct (J = 14.0 Hz) < ctc (J = 20.0 Hz) < ccc (J = 28.0 Hz). The Ar-Me (7- or 8-Me) or Ar-Me2 (7,8 or 8,9Me₂) exhibit one or two equally intense signal(s) for tcc, cct and ctc isomers and support Cl-symmetry in the complexes. The ccc-RuL₂Cl₂ shows two equally intense signals for (1d)/(3d) while three signals for (2d)/(4d). This may be due to inequivalence of Me group in ccc isomers (C₁ -symmetry). Redox studies show ruthenium(III)/ruthenium(II) couple at 0.4 V (vs SCE) for tcc isomers and 0.5 - 0.6 V (vs SCE) for other isomers (cct/ctc/ccc). Page(s): 416-422

Acid-base equilibrium of neutral red in benzene-in-water microemulsions

Sat, 01 May 1999 00:00:00 GMT

Title: Acid-base equilibrium of neutral red in benzene-in-water microemulsions Authors: Paul, B.C.; Ismail, K. Abstract: Acid-base equilibrium of neutral red (NR) has been studied spectrophotometrically at 25°C in two o/w microernulsions (ME's) containing benzene/sodium dodecyl sulphate/aqueous buffer/ 1-propanol (ME1) and benzene/sodium dodecyl sulphate/aqueous buffer/1-butanol (ME2). NR resides at the interfacial region of the MEs. A modified Henderson-Haselbach (HH) equation is found to be applicable and only one protonation of NR takes place in the pH range of 1.2 to 11 .2. NR appears completely in the protonated form at pH ≤ 4.5, and in the basic form at pH ≥ 9.5. The values of pK_a, for NR in MEl and ME2 are found to be 6.88 and 7.05, respectively. These pK_a values were factorized into contributions due to (1) effective dieiectric constant of the interfacial region, (2) interaction between protonated NR and negatively charged droplet, and (3) surface potential of the droplet. The surface potentials of the propanol and butanol containing droplets have been estimated to be approximately equal to -75 ± 10 and -85 ± 10 mV, respectively. Page(s): 496-500

Synthesis, structure and separation of a new chiral metal cluster (μ₃-S)FeCoMo(CO)₈ {C₅H₄C(O)C₆H₄C(O)OCH₃-4} on an amylopectin tris-(phenylcarbamate) chiral column by HPLC

Sat, 01 May 1999 00:00:00 GMT

Title: Synthesis, structure and separation of a new chiral metal cluster (μ₃-S)FeCoMo(CO)₈ {C₅H₄C(O)C₆H₄C(O)OCH₃-4} on an amylopectin tris-(phenylcarbamate) chiral column by HPLC Authors: Zhou, Zhigiang; Ding, Errun; Hou, Jingguo; Chen, Liren Abstract: Preparation of amylopectin tris(phenylcarbamate) (ATP) chiral stationary phases (CSPs) coated on small-particle (5μm, 120Å) spherical silica support is reported. A new chiral tetrahedral cluster FeCoMo(μ₃-S) (CO)₈{C₅H₄C(O)C₆H₄C(O)OCH₃-4) (2) has been synthesized by the thermal reaction of the precursor (μ-S)FeCO₂ (CO)₉ with functionally substituted cyclopentadienyl tricarbonyl metal anion [Mo(CO)₃C₅H₄C(O)CH₃] and it has been resolved on the amylopectin tris (phenylcarbamate) chiral stationary phase. Page(s): 411-415

NOPR Collection:

Oxidation of nitrous acid by tris( diimine) iron (III) complexes

Effect of steric crowding : Synthesis, spectral characterization and redox studies of isomers of ruthenium(II) N(1)-ethyl-2-(arylazo)- imidazoles

Acid-base equilibrium of neutral red in benzene-in-water microemulsions

Synthesis, structure and separation of a new chiral metal cluster (μ3-S)FeCoMo(CO)8 {C5H4C(O)C6H4C(O)OCH3-4} on an amylopectin tris-(phenylcarbamate) chiral column by HPLC

Synthesis, structure and separation of a new chiral metal cluster (μ₃-S)FeCoMo(CO)₈ {C₅H₄C(O)C₆H₄C(O)OCH₃-4} on an amylopectin tris-(phenylcarbamate) chiral column by HPLC