Electronic absorption spectra of aminosilanes

Pitt, Colin G.; Fowler, Mary S.

doi:10.1021/ja01001a088

Cited by 13 publications

(6 citation statements)

References 2 publications

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“…N-acetylation, causes a shift of the absorption bands. 36 The absorption maxima of the N-acetyl aristolactam I (λ max 241, 286, 327, 387, 406 nm) reveal a hypsochromic shift of the L-I bands at 230–300 nm, whereas the effect on the long wavelength bands is less significant. This is not the case with L-Ia sulfate suggesting that the NH group has not been perturbed.…”

Section: Resultsmentioning

confidence: 99%

Aristolochic Acid I Metabolism in the Isolated Perfused Rat Kidney

Priestap

Torres

Rieger

et al. 2011

Chem. Res. Toxicol.

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Aristolochic acids are natural nitro-compounds found globally in the plant genus Aristolochia that have been implicated in the severe illness in humans termed aristolochic acid nephropathy (AAN). Aristolochic acids undergo nitroreduction, among other metabolic reactions, and active intermediates arise that are carcinogenic. Previous experiments with rats showed that aristolochic acid I (AA-I), after oral administration or injection, is subjected to detoxication reactions to give aristolochic acid Ia, aristolactam Ia, aristolactam I and their glucuronide and sulfate conjugates that can be found in urine and faeces. Results obtained with whole rats do not clearly define the role of liver and kidney in such metabolic transformation. In this study, in order to determine the specific role of the kidney on the renal disposition of AA-I and to study the biotransformations suffered by AA-I in this organ, isolated kidneys of rats were perfused with AA-I. AA-I and metabolite concentrations were determined in perfusates and urines using HPLC procedures. The isolated perfused rat kidney model showed that AA-I distributes rapidly and extensively in kidney tissues by uptake from the peritubular capillaries and the tubules. It was also established that the kidney is able to metabolize AA-I into aristolochic acid Ia, aristolochic acid Ia O-sulfate, aristolactam Ia, aristolactam I and aristolactam Ia O-glucuronide. Rapid demethylation and sulfation of AA-I in the kidney generate aristolochic acid Ia and its sulfate conjugate that are voided to the urine. Reduction reactions to give the aristolactam metabolites occur to a slower rate. Renal clearances showed that filtered AA-I is reabsorbed at the tubules whereas the metabolites are secreted. The unconjugated metabolites produced in the renal tissues are transported to both urine and perfusate whereas the conjugated metabolites are almost exclusively secreted to the urine.

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Section: Resultsmentioning

confidence: 99%

Aristolochic Acid I Metabolism in the Isolated Perfused Rat Kidney

Priestap

Torres

Rieger

et al. 2011

Chem. Res. Toxicol.

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“…MLCT transitions cannot be conclusively ruled out, but the ligand LUMOs, probably the Si d orbitals, are likely to be at high energy. (Also, in the electronic spectrum of HN(SiMe 3 ) 2 , the position of the first absorption maximum has been reported not to be highly solvent-sensitive . This argues against an assignment involving charge transfer to Si.)…”

Section: Discussionmentioning

confidence: 99%

“…Excited states of copper(I) complexes are of three types, interconfigurational, intraligand, and MLCT; the d 10 configuration makes d−d and LMCT excited states impossible . For [CuN(SiMe 3 ) 2 ] 4 , low-energy intraligand transitions are unlikely: the lowest-energy electronic absorption band in hexamethyldisilazane, HN(SiMe 3 ) 2 , is at 203 nm …”

Section: Discussionmentioning

confidence: 99%

Phosphorescence and Structure of a Tetrameric Copper(I)−Amide Cluster

et al. 1998

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The colorless copper(I) cluster [CuN(Si(CH(3))(3))(2)](4), which contains a square-planar Cu(4)N(4) core, phosphoresces in CH(2)Cl(2) solution (lambda(max), 512 nm; lifetime, 30 &mgr;s) and in the solid state at room temperature. Its electronic absorption spectrum in CH(2)Cl(2) consists of two intense bands at 283 and 246 nm; these transitions, as well as the phosphorescence, are likely to involve population of MOs reflecting substantial Cu.Cu interactions. Solid [CuN(Si(CH(3))(3))(2)](4) luminesces with approximately the same spectrum as that of the CH(2)Cl(2) solutions. At 77 K, the solid-state luminescence red-shifts slightly (lambda(max), 524 nm) and narrows substantially (fwhm, 2400 cm(-)(1); vs 3500 cm(-)(1) at 300 K); the emission lifetime in glassy Et(2)O solution is 690 &mgr;s. X-ray analysis of crystals of [CuN(Si(CH(3))(3))(2)](4) at 130 and 296 K shows that, although the previously reported structure solution (in space group I2/m, with the molecules on 2/m sites; Eur. J. Solid State Inorg. Chem. 1992, 29, 573-583) is approximately correct, the lattice is actually primitive, P2/n, and the only crystallographically required symmetry element for the molecule is a 2-fold axis. C(24)H(72)Cu(4)N(4)Si(8): monoclinic, space group P2/n, Z = 2. At 130 K, a = 9.285(3) Å, b = 13.393(3) Å, c = 17.752(5) Å, and beta = 90.53(2) degrees. [At 296 K, a = 9.3773(4) Å, b = 13.5836(7) Å, c = 17.814(2) Å, and beta = 90.207(7) degrees.] At 130 K, the Cu and N atoms in the cluster are planar within 0.007 Å, and the Cu-N and Cu.Cu distances are 1.917(4)-1.925(4) and 2.6770(7)-2.6937(7) Å, respectively. Despite the low volatility of the compound, it can be used as a precursor for chemical vapor deposition (CVD) of copper metal, under H(2) carrier gas, with both source and substrate at ca. 200 degrees C. Smaller amounts of Cu metal films are also deposited when the substrate temperature is as low as 145 degrees C (in the dark) or 136-138 degrees C (under Pyrex-filtered Xe arc lamp illumination). Thus, Cu CVD with this precursor shows slight photochemical enhancement.

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“…Both (TiCl4)2-OMT and (TiCl4)2-HMT (d°s ystems) show charge-transfer bands at -~35,000, ~39,000, and ~44,000 cm'1, the first two being assigned to titanium(d) chlorine(-7r) transitions21 and the latter to an internal ligand transition. 22 The ligand field peak (2Eg *-2T2g) observed for (TiCl3)2-OMT-2-THF shows distinct double structure with a band at 13,250 cm-1 (lODg) and a shoulder at 12,390 cm'1 indicating that the field must contain a component of lower symmetry than Oh. Using the 10Dq values for TiCl3,23 TiCl3-3THF,3 and TiCU-HMT1 (here three chlorine atoms and three nitrogen atoms of the trimeric silazane ring comprise the octahedral titanium(III) environment) and Jorgensen's rule of average environment, the predicted peak position is at 14,010 cm'1 which implies a weaker donor ability ~760 cm-1 of the nitrogen atoms of OMT as compared to HMT.…”

Section: Discussionmentioning

confidence: 97%

Evaluation of the donor role of octamethylcyclotetrasilazane

Hughes¹,

Willey²

1973

J. Am. Chem. Soc.

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NMes; and (MC14)20MT where M = Ti. The stereochemistry of these neutral complexes and the coordination of the metal centers have been assessed in the light of spectral, conductivity, and chemical evidence, and possible molecular structures are proposed. Lewis base participation of the tetrameric (Si-N) ring is seen to involve only two of the four available nitrogen centers in (M-N) bonding and this bidentate behavior is reconciled with the favored metal hexacoordination of these powerful Lewis acids. Hexamethylcyclotrisiiazane [Me2SiNH]3, abbreviated HMT, and titanium(IV) chloride give (TiCl4)2 HMT as a neutral six-coordinate complex, and the donor behavior (bidentate) of the trimeric silazane ring is similarly discussed.In an earlier investigation of the reactions between hexamethylcyclotrisiiazane (Me2SiNH)8, abbreviated HMT, and titanium(III) chloride or vanadium (III) chloride we showed that six-cooordinate adducts of the type MC13 HMT are formed in which all three of the skeletonal nitrogen atoms of the ligand are involved in metal-nitrogen bonding.1 Having established HMT as a nitrogen donor (terdentate), it seemed reasonable to suppose that its tetrameric analog octamethylcyclotetrasilazane (Me2SiNH)4, abbreviated OMT, would behave in similar fashion. Indeed, with a maximum of four nitrogen atoms formally available for coordination, this tetrameric ring clearly has intriguing potential as a multidentate ligand. The present investigation is essentially concerned with an evaluation of the exact donor role of OMT following a study of its reactions with titanium(IV) chloride, titanium(III) chloride, vanadium(III) chloride, and chromium(III) chloride. Experimental SectionMaterials. HMT and OMT were prepared by ammonolysis of dimethyldichlorosilane following the method of Osthoff and Kantor.2 Titanium(IV) chloride (Hopkin and Williams, Essex), titanium(III) chloride and vanadium(III) chloride (K and K Laboratories, Plainview, N. Y.), and chromium(III) chloride (Pfaltz and Bauer Inc., Flushing, N. Y.) were obtained as anhydrous materials and their respective adducts were prepared by standard procedures described in the literature; MC13 • 3THF where M = Ti,3 V,4 and Cr,5 MCl3-2NMe3 where M = Ti,6 V,7 and Cr.7 All solvents were stored over calcium hydride and phosphoric oxide and distilled in vacuo when required.Physical Measurements and Analyses. Infrared spectra (4000-200 cm-1) were recorded on a Perkin-Elmer 621 spectrometer with Nujol and fluorolube mulls held between Csl plates. Conductivity measurements were performed using a Wayne Kerr Universal B221 conductance bridge. The conductivity cell used was calibrated with standard aqueous KC1 solutions and readings were taken at 298.0 ± 0.1 °K on samples of approximately 10-4 M concentration in dichloromethane solution. Absorption spectra were recorded on a Cary 14 spectrophotometer with samples either as solutions in 1-cm

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Electronic absorption spectra of aminosilanes

Cited by 13 publications

References 2 publications

Aristolochic Acid I Metabolism in the Isolated Perfused Rat Kidney

Aristolochic Acid I Metabolism in the Isolated Perfused Rat Kidney

Phosphorescence and Structure of a Tetrameric Copper(I)−Amide Cluster

Evaluation of the donor role of octamethylcyclotetrasilazane

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