Pterin chemistry. An unequivocal synthesis of pteroyl-gamma-L-glutamyl-gamma-L-glutamyl-L-glutamic acid]

A new and unequivocal synthesis of pteroyl-γ-L-glutamyl-γ-L-glutamyl-L-glutamic acid free of isomers is described. A melt of N(2′)-acetyl-6-formylpterine and tetramethyl-N-(p-amino-benzoyl)-γ-L-glutamyl-γ-L-glutamyl-L-glutamatewas quantitatively converted to the corresponding azomethin IX. NaBH₄-reduction followed by basic hydrolysis of acetyl and methylester groups gives pure pteroyl-γ-L-glutamyl-γ-L-glutamyl-L-glutamic acid in good yield.     

Palladium(II)‐Komplexe des 1,1,3,3,5,5‐Hexakis(dimethylamino)‐λ5‐[1,3,5]triphosphinins

Palladium(II) Complexes of 1,1,3,3,5,5‐Hexakis(dimethylamino)‐λ⁵‐[1,3,5]triphosphinine 1,1,3,3,5,5‐Hexakis(dimethylamino)‐1λ⁵‐3λ⁵‐5λ⁵‐[1,3,5]triphosphinine ( 5 ) reacts with (benzonitrile)₂PdCl₂ to give the chelate complex dichloro(dodeca‐N‐methyl‐1λ⁵,3λ⁵,5λ⁵‐1,3,5‐triphosphinine‐1,1,3,3,5,5‐hexaamin‐C²,C⁴)palladium ( 6 ). In a pyridine‐d₅ solution of 6 the complex dichloro(dodeca‐N‐methyl‐1λ⁵,3λ⁵,5λ⁵‐1,3,5‐triphosphinine‐1,1,3,3,5,5‐hexaamin‐C²)((²H₅)pyridine‐N)palladium ( 7 ) is formed. The solute 7 could not be isolated as a solid, because elimination of the solvent regenerates 6 quantitatively. Properties, nmr and ir spectra of 6 and 7 are reported. 6 is characterized by the results of an X‐ray structural analysis.     

Acyl- und Alkylidenphosphane. XXIV. (N,N-Dimethylthiocarbamoyl)trimethylsilylphosphane und 1,2-Di(tert-butyl)-3-dimethylamino-1-thio-4-trimethylsilylsulfano-1λ5,2λ3-diphosphet-3-en

Acyl- and Alkylidenephosphines. XXIV. (N,N-Dimethylthiocarbamoyl)trimethylsilyl-phosphines and 1.2-Di(tert-butyl)-3-dimethylamino-1-thio-4-trimethylsilylsulfano-1λ⁵, 2λ³-diphosphet-3-ene In contrast to bis(trimethylsilyl)phosphines R? P[? Si(CH₃)₃]₂ 1 {R ? H₃C a ; (H₃C)₃C b ; H₅H₆ c ; H₁₁C₉ d ; (H₃C)₃Si e }, the more nucleophilic lithium trimethylsilylphosphides 4 react with N,N-dimethylthiocarbamoyl chloride already at ?78°C to give (N,N-dimethylthiocarbamoyl)trimethylsilylphosphines 2 . Working up the reaction, a dismutation of the mesityl derivative 2d is observed, whereas the tert-butyl compound 2b dissolved in toluene, eliminates dimethyl(trimethylsilyl)amine to form 1,2-di(tert-butyl)-3-dimethylamino-1-thio-4-trimethylsilyl-sulfano- 1λ⁵, 2λ³-diphosphet-3-ene 6b , nearly quantitatively within several days at +20°C.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS. XVIII. INDOMETHACIN

Abstract— The photochemistry, photophysics, and photosensitization (Type I and II) of indomethacin (IN) (N-[p-chlorobenzoyl]-5-methoxy-2-methylindole-3-acetic acid) has been studied in a variety of solvents using NMR, high performance liquid chromatography-mass spectroscopy, transient spectroscopy, electron paramagnetic resonance in conjunction with the spin trapping technique, and the direct detection of singlet molecular oxygen (^l O₂) luminescence. Photodecomposition of IN (λ_ex > 330 nm) in degassed or air-saturated benzene proceeds rapidly to yield a major (2; N-[p-chlorobenzoyl]-5-methoxy-2-methyl-3-methylene-indoline) and a minor (3; N-[p-chlorobenzoyl]-5-methoxy-2, 3-dimethyl-indole) decarboxylated product and a minor indoline (5; 1-en-5-methoxy-2-methyl-3-methylene-in-doline), which is formed by loss of the p-chlorobenzoyl moiety. In air-saturated solvents two minor oxidized products 4 (N-[p-chlorobenzoyl]-5-methoxy-2-methylindol-3-aldehyde) and 6 (5-methoxy-2-methyl-indole-3-aldehyde) are also formed. When photolysis was carried out in ¹⁸O₂-saturated benzene, the oxidized products 4 and 6 contained ¹⁸O, indicating that oxidation was mediated by dissolved oxygen in the solvent. In more polar solvents such as acetonitrile or ethanol, photodecomposition is extremely slow and inefficient. Phosphorescence of IN at 77 K shows strong solvent dependence and its emission is greatly reduced as polarity of solvent is increased. Flash excitation of IN in degassed ethanol or acetonitrile produces no transients. A weak transient is observed at 375 nm in degassed benzene, which is not quenched by oxygen. Irradiation of IN (λ_ex > 325 nm) in N₂-gassed C₆H₆ in the presence of 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) results in the trapping of two carbon-centered radicals by DMPO. One adduct was identified as DMPO/^.COC₆H₄-p-CI, while the other was probably derived from a radical formed during IN decarboxylation. In air-saturated benzene, (hydro) peroxyl and alkoxyl radical adducts of DMPO are observed. A very weak luminescence signal from ¹O₂ at 1268 nm is observed initially upon irradiation (λ_ex= 325 nm) of IN in air-saturated benzene or chloroform. The intensity of this ¹O₂ signal increases as irradiation is continued suggesting that the enhancement in ¹O₂ yield is due to photoproduct(s). Accordingly, when 2 and 3 were tested directly, 2 was found to be a much better sensitizer of ¹O₂ than IN. In air-saturated ethanol or acetonitrile no IN ¹O₂ luminescence is detected even on continuous irradiation. The inability of IN to cause phototoxicity may be related to its photo stability in polar solvents, coupled with the low yield of active oxygen species (¹O₂, O₂^?_-) upon UV irradiation.     

Extraction and partial characterisation of antioxidant pigment produced by Chryseobacterium sp. kr6

Pigments synthesised by Chryseobacterium sp. kr6 growing on feather waste were extracted and characterised. The pigment extract was characterised by KOH test, UV–vis, CIELAB colour system, HPLC-DAD-MS, FTIR and its antioxidant capacity was evaluated. A positive bathochromic shift was observed when kr6 colonies or pigment extracts were subjected to alkaline solution (20% KOH) and a λ_max at 450 nm was detected for acetone extracts, although no typical fine structure of carotenoids was detected in the electomagnetic spectra. The HPLC profile of the extracted pigment showed that the compound has three different peaks with λ_max near 450 nm. The FTIR analysis shows some principal functional groups from a flexirubin-like molecule. The pigmented compound also presents antioxidant activity evaluated by the scavenging of the ABTS radical.     

Synthesis and characterization of aromatic poly(ether ketone)s containing cyclotriphosphazene units

Bis(4-oxybenzoic acid) tetrakis(phenoxy) cyclotriphosphazene (IUPAC name: 4-[4-(carboxyphenoxy)-2,4,6,6-tetraphenoxy-1,3,5,2λ⁵,4λ⁵,6λ⁵-triazatriphosphinin-2-yl]oxy-benzoic acid) was synthesized and direct polycondensed with diphenylether or 1,4-diphenoxybenzene in Eaton's reagent at the temperature range of 80–120°C for 3 hours to give aromatic poly(ether ketone)s. Polycondensations at 120°C gave polymer of high molecular weight. Incorporation of cyclotriphosphazene groups in the aromatic poly(ether ketone) backbone greatly enhanced the solubility of these polymers in common organic polar solvents. Thermal stabilities by TGA for two polymer samples of polymer series ranged from 390 to 354°C in nitrogen at 10% weight loss and glass transition temperatures (T_g) ranged from 81.4 to 89.6°C by DSC. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1227–1232, 1998     

Cyclotrimethylenetriphosphinic Acid

The cyclotrimethylenetriphosphinic acid ( 1 ), isoelectronic to the cyclotriphosphoric acid, is formed in the hydrolysis of 1,1,3,3,5,5-hexakis(dimethylamino)-1λ⁵,3λ⁵,5λ⁵-[1,3,5]triphosphinine. Compound 1 is stable to acids and bases. On heating for a longer period of time in D₂O each of the three methylene groups is monodeuterated.     

Design of donor–acceptor–donor (D–A–D) type small molecule donor materials with efficient photovoltaic parameters

Four Donor–Acceptor–Donor (D–A–D) type of donor molecules (M1‐M4) with triphenylamine (TPA) as donor moiety, thiophene as bridge, and thiazolothiazole as acceptor unit were designed and its photovoltaic parameters were equated with reference molecule “R.” DFT functional CAM‐B3LYP/6‐31G (d,p) was found best for geometry optimization and TD‐CAM‐B3LYP/6‐31G (d,p) was found suitable for excited state calculations. Among designed donor molecules, M4 manifests suitable lowest band gap of 4.73 eV, frontier molecular orbital energy levels as well as distinctive broad absorption of 455.3 nm due to the stronger electron withdrawing group. The electron‐withdrawing substituents contribute to red shifts of absorption spectra and better stabilities for designed molecules. The theoretically determined reorganization energies of designed donor molecules suggested excellent charge mobility property. The lower λ_e values in comparison with λ_h illustrated that these four donor materials would be ideal for electron transfer and M4 would be best amongst the investigated molecules with lowest λ_e of 0.0177. Furthermore, the calculated Voc of M4 is 2.04 V with respect to PC₆₀BM (phenyl‐C61‐butyric acid methyl ester). This study revealed that the designed donor materials are suitable and recommended for high performance organic solar cell devices.     

Application of alkoxy-λ6-sulfanenitriles as strong alkylating reagents

Alkoxy-λ⁶-sulfanenitriles were found to be versatile alkylating reagents toward various nucleophiles bearing at least one proton such as methanol, phenol, thiophenols, carboxylic acids, p-toluenesulfonic acid, hydrochloric acid, and primary and secondary amines. Reactivity of the alkoxy group of the λ⁶-sulfanenitriles showed an opposite trend to the usual S_N2 character, i.e. Me ( 1a ), Pr ( 1b ), and Bu ( 1d ) ≪ i-Pr ( 1c ). In the presence of p-TsOH, alkyl tosylates were predominantly formed instead of the alkylation products of nucleophiles. In addition, even a sterically hindered substrate, neopentyloxy-λ⁶-sulfanenitrile, was found to undergo an S_N2 reaction toward thiophenol without any rearrangement product to give neopentyl phenyl sulfide in good yield. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:193–198, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20006     

Ultimate tensile properties of elastomers. VII. Effect of crosslink density on time–temperature dependence

Data on tensile strength and elongation at break for a series of Viton A-HV vulcanizates are discussed. The data were obtained at various extension rates at temperatures from ?5 to 230°C (25 ? T — T_g ? 260°C) on seven vulcanizates having crosslink densities v_e (estimated from C₁ in the Mooney-Rivlin equation) from 0.46 × 10^?5 to 24.4 × 10^?5 mole/cm³. At an extension rate of 1 min^?1, an increase in v_e affects the tensile strength σ_b (based on the undeformed cross-sectional area) and the true tensile strength σ_bσ_b (based on the cross-sectional area of a deformed specimen) as follows: σ_b is essentially constant at a low temperature; it passes through a decided maximum at intermediate temperatures; and it increases to a plateau at elevated temperatures. In contrast, λ_bσ_b decreases markedly at all temperatures, an exception being the most lightly crosslinked vulcanizate(s). Application of time—temperature superposition to the ultimate-property data gave log a_T; its temperature dependence is that typical of nonpolar rubbery polymers. Data on the vulcanizates were compared in corresponding temperature states by plotting log 273σ_b/T, log 273λ_bσ_b/T, and (λ_b — 1)/(λ_b — 1)_max against logt_b/(t_b)_max, where t_b is the temperature-reduced time to break and (t_b)_max is the value at which the ultimate extension ratio λ_b attains its maximum, (λ_b)_max. Except for the most lightly crosslink vulcanizate, the comparison shows that 273λ_bσ_b/T and (λ_b — 1)/(λ_b — 1)_max are substantially independent of (or only weakly dependent on) crosslink density, that 273λ_b/T increases with v_e, and that 273λ_b/T ∝? v_e^0.6 and λ_b ∝? v_e^?0.4 at a large value of t_b/(t_b)_max.     

Investigation of Molecular Iridium Fluorides IrFn (n=1–6): A Combined Matrix-Isolation and Quantum-Chemical Study

The photo-initiated defluorination of iridium hexafluoride (IrF₆) was investigated in neon and argon matrices at 6 K, and their photoproducts are characterized by IR and UV-vis spectroscopies as well as quantum-chemical calculations. The primary photoproducts obtained after irradiation with λ=365 nm are iridium pentafluoride (IrF₅) and iridium trifluoride (IrF₃), while longer irradiation of the same matrix with λ=278 nm produced iridium tetrafluoride (IrF₄) and iridium difluoride (IrF₂) by Ir−F bond cleavage or F₂ elimination. In addition, IrF₅ can be reversed to IrF₆ by adding a F atom when exposed to blue-light (λ=470 nm) irradiation. Laser irradiation (λ=266 nm) of IrF₄ also generated IrF₆, IrF₅, IrF₃ and IrF₂. Alternatively, molecular binary iridium fluorides IrF_n (n=1–6) were produced by co-deposition of laser-ablated iridium atoms with elemental fluorine in excess neon and argon matrices under cryogenic conditions. Computational studies up to scalar relativistic CCSD(T)/triple-ζ level and two-component quasirelativistic DFT computations including spin-orbit coupling effects supported the formation of these products and provided detailed insights into their molecular structures by their characteristic Ir−F stretching bands. Compared to the Jahn-Teller effect, the influence of spin-orbit coupling dominates in IrF₅, leading to a triplet ground state with C_4v symmetry, which was spectroscopically detected in solid argon and neon matrices.     

Photocatalytic Formic Acid Conversion on CdS Nanocrystals with Controllable Selectivity for H2 or CO

Formic acid is considered a promising energy carrier and hydrogen storage material for a carbon‐neutral economy. We present an inexpensive system for the selective room‐temperature photocatalytic conversion of formic acid into either hydrogen or carbon monoxide. Under visible‐light irradiation (λ>420 nm, 1 sun), suspensions of ligand‐capped cadmium sulfide nanocrystals in formic acid/sodium formate release up to 116±14 mmol H₂ g_cat^?1 h^?1 with >99 % selectivity when combined with a cobalt co‐catalyst; the quantum yield at λ=460 nm was 21.2±2.7 %. In the absence of capping ligands, suspensions of the same photocatalyst in aqueous sodium formate generate up to 102±13 mmol CO g_cat^?1 h^?1 with >95 % selectivity and 19.7±2.7 % quantum yield. H₂ and CO production was sustained for more than one week with turnover numbers greater than 6×10⁵ and 3×10⁶, respectively.     

Enantioselective Intramolecular [2+2] Photocycloaddition Reactions of 4‐Substituted Coumarins Catalyzed by a Chiral Lewis Acid

Eight coumarins, which carry a terminal alkene tethered by a CH₂XCH₂ group to their 4‐position (X=CH₂, CMe₂, O, S, NBoc, NZ, NTs, NBn), were synthesized in overall yields of 51–80 %. Starting materials for the syntheses were either commercially available 4‐hydroxycoumarin or 4‐formylcoumarin. The intramolecular [2+2] photocycloaddition of these coumarins gave diastereoselectively products with a tetracyclic 3,3a,4,4a‐tetrahydro‐1H‐cyclopenta[2,3]cyclobuta[1,2‐c]chromen‐5(2H)‐one skeleton. Direct irradiation at λ=300 nm in dichloromethane (c=10 mM ) led to product formation in good yields for most substrates, presumably via a singlet excited state intermediate. Due to the low coumarin absorption at λ >350 nm the photocycloaddition was slow upon irradiation at λ=366 nm. Addition of a chiral oxazaborolidine‐based Lewis acid (50 mol %) increased the reaction rate at λ=366 nm and induced a significant enantioselectivity in the [2+2] photocycloaddition. Six out of eight coumarin substrates (X=CH₂, CMe₂, O, NBoc, NZ, NTs) gave the respective products in yields of 72–96 % and with 74–90 % enantiomeric excess (ee) upon irradiation in dichloromethane (c=20 mM ) at ?75 °C. The Lewis acid presumably acts by coordination to the coumarin carbonyl oxygen atom, which leads to a bathochromic shift (redshift) of the UV absorption and which increases the singlet state lifetime. A second electrostatic interaction of the hydrogen atom at C3 with the oxygen atom of the oxazaborolidine is likely.     

Red‐NIR Luminescent Hybrid Poly(methyl methacrylate) Containing Covalently Linked Octahedral Rhenium Metallic Clusters

The embedding of functional inorganic entities into polymer matrices has become an intense field of investigation in which the main challenges are to keep the added value of the inorganic entities while preventing their self‐aggregation within the organic matrix. We present a simple way to obtain a homogeneous highly red‐NIR luminescent hybrid copolymer that contains covalently bonded nanometric‐sized {Re₆} octahedral clusters. The [Re₆Seⁱ₈(OH)^a₆]^4? cluster complexes are primarily functionalized in two steps with tert‐butylpyridine (TBP) and methacrylic acid (MAC) to give neutral [Re₆Se₈(TBP)₄(MAC)₂] building blocks that are copolymerized with methyl methacrylate (MMA) either in solution or in bulk in the presence of azobisisobutyronitrile as an initiator. Several samples containing 0, 0.025, 0.05, and 0.1 wt % of functionalized {Re₆} clusters were prepared. As the {Re₆} cluster/MMA ratio is very low, the obtained copolymers keep the entire processability of pure poly(methyl methacrylate) (PMMA), as demonstrated by differential scanning calorimetry and thermogravimetric analysis. Voltammetric and luminescence studies also indicate that the intrinsic properties of the clusters are preserved within the polymer matrix. All the samples show a bright (emission quantum yield=0.07), broad, and structureless emission band, which extends from λ=600 nm to more than λ=950 nm, with the maximum wavelength centered around λ_em=710 nm either in solution or in the solid state. Moreover, the high stability of the incorporated inorganic phosphors prevents the material from photobleaching, and thus the luminescence properties are kept entirely even after nine months of ageing.     

A square‐planar tellurium(II) complex with Te,Te′‐chelating ligands

While exploring the chemistry of tellurium‐containing dichalcogenidoimidodiphosphinate ligands, the first all‐tellurium member of a series of related square‐planar E^II(E′)₄ complexes (E and E′ are group 16 elements), namely bis(P,P,P′,P′‐tetraphenylditelluridoimidodiphosphinato‐κ²Te,Te′)tellurium(II) (systematic name: 2,2,4,4,8,8,10,10‐octaphenyl‐1λ³,5,6λ⁴,7λ³,11‐pentatellura‐3,9‐diaza‐2λ⁵,4λ⁵,8λ⁵,10λ⁵‐tetraphosphaspiro[5.5]undeca‐1,3,7,9‐tetraene), C₄₈H₄₀N₂P₄Te₅, was obtained unexpectedly. The formally Te^II centre is situated on a crystallographic inversion centre and is Te,Te′‐chelated to two anionic [(TePPh₂)₂N]⁻ ligands in an anti conformation. The central Te^II(Te)₄ unit is approximately square planar [Te—Te—Te = 93.51 (3) and 86.49 (3)°], with Te—Te bond lengths of 2.9806 (6) and 2.9978 (9) Å.     

Synthesis,Photophysics and Redox Properties of Aza-BODIPY Dyes with Electron-Donating Groups

A series of novel aza-BODIPY dyes substituted with p-(dimethylamino)phenyl groups were synthesized and their spectral and electrochemical properties were compared. In particular, the impact of p-(Me₂N)Ph- groups on these characteristics was of consideration. For two aza-BODIPYs studied, a near-IR absorption band was observed at circa λ_abs=796 nm. Due to the pronounced intramolecular charge transfer (ICT) exerted by the presence of strongly electron-donating p-(Me₂N)Ph- substituents, the compounds studied were weakly emissive with the singlet lifetimes (τ_S) in the picosecond range. Nanosecond laser photolysis experiments of the brominated aza-BODIPYs revealed T₁→T_n absorption spanning from ca. 350 nm to ca. 550 nm with the triplet lifetimes (τ_T) ranged between 6.0 μs and 8.5 μs. The optical properties of the aza-BODIPYs studied were pH-sensitive. Upon protonation of the dimethylamino groups with trifluoroacetic acid in toluene, a stepwise disappearance of the NIR absorption band at λ_abs=790 nm was observed with the concomitant appearance of a blue-shifted absorption band at λ_abs=652 nm, which was accompanied by a prominent emission band at λ_fl=680 nm. The transformation from a non-emissive to an emissive compound is associated with the inhibition of the ICT. As estimated by CV/DPV measurements, all aza-BODIPYs studied exhibited two irreversible oxidation and two quasi-reversible reduction processes. All compounds studied exhibit extremely high photostability and thermal stability.     

Biosynthesis of verrucarins and roridins. 2. Incorporation of acetate in cis-transmuconic acid and of mevalonate in roridinic acid]

Incorporation experiments using sodium [1-¹⁴C]-acetate and sodium [2-¹⁴C]- and [2-¹⁴C,2-³H₂]-mevalonate and degradations of the verrucarin A ( 1 ) and roridin A ( 2 ) so produced demonstrate that cis,trans-muconic acid ( 3 ) is formed from 3 acetate units. The cis,trans-muconic acid and the C₂-side-chain structural elements of roridinic acid ( 6 ) are built up from 4 acetate units; the cis-oricntcd C(11)-carboxyl group of 6 originates from C(1) of acctic acid. The structural moiety of roridinic acid ( 6 ) corresponding to verrucarinic, acid ( 7 ) originates from mevalonate, as does 7 . A new degradation scheme was devised for roridinic acid ( 6 ); the oxime 23 of its 13 dehydro-detrahydro derivative 21 underwent cleavage with SOCl₂ and subsequent hydrolysis to yield verrucarinolactone ( 8 ), acetonitrile ( 26 ) and methyl adipaldohydate ( 27 ) by a heterolytic Beckmann fragmentation reaction.     

Photochemische Reaktionen. 117. Mitteilung [1] Zur Photochemie von 5,6-Epoxydienen und konjugierten 5,6-Epoxytrienen

Photochemistry of 5,6-Epoxydienes and of Conjugated 5,6-Epoxytrienes On singulet excitation (δ = 254 nm) the 5,6-epoxydiene 6 and the conjugated 5,6-epoxytrienes 7 and 8 exclusively give products arising from cleavage of the C, C-bond of the oxirane (cf. 6 → 9 , 10 , 11 ; 7 → (E)- 15 , 16 , 17 ; 8 → 18 (A+B) , 19 (A+B) , 20 , 21 ). The dihydrofuran compounds 11 and (E/Z)- 15 are formed by cyclization of a ketonium-ylide a and d , respectively. Photolysis of a gives the carbene b which yields the cyclopropene 9 , whereas d forms photochemically the carbenes f and g which yield the methano compounds 16 and 17 . The isomeric cyclopropene derivatives 20 and 21 are products of the intermediates h and i , respectively, which are formed by photolysis of the ylide e . The cyclopropene 21 isomerizes by intramolecular cycloadditions to 18 (A+B) and 19 (A+B) . - On triplet excitation (λ?LD nm; 280 nm; acetone) 6 undergoes cleavage of the C(5), O-bond and isomerizes to 12 and 14 . However, 7 is converted by cleavage of the C, C-bond of the oxirane to yield 15 . On treatment with BF₃O(C₂H₅)₂ 6 gives 14 , whereas 7 yields 22 , and 8 forms 23 and 24 .     

Empirical Relationships between Transport Coefficients of Liquid Metals over a Range of Thermodynamic States

Abstract

Assuming the Wiedemann-Franz law, measured data for electrical conductivity α of liquid Cs and Rb is converted to λ_e , the electronic contribution to the thermal conductivity A. While the major part of the measured thermal conduction is thereby accounted for, the “residual” ionic contribution, denned as (^λ-1—λ_e ^?1)^?1, does not simply increase as the metal-insulator transition is approached along the coexistence curve.

Since λ is dominated by _λe, it is surprising that a hard sphere model, which predicts λ/n = 5k_B/2M with n the shear viscosity and M the ionic mass, still gives correctly a relatively constant ratio, though a difference in behaviour of λ/n as a function of thermodynamic state is noted for liquid Rb and Cs compared with liquid argon.

A generalization of Andrade's formula for shear viscosity at the melting point is also discussed, including the work of Zwanzig relating the self-diffusion coefficient D to n via the bulk viscosity.     

Reactions of iPr2N?CP with methylating agents: Formation of the diamino-2-phosphaallylic cation ⊕

The reaction of di(isopropyl)aminophosphaethyne 1 with iodomethane or the methyl ester of trifluormethylsulfonic acid (methyl triflate) yields the ionic 1λ³, 3λ³-diphosphetene derivatives ⁺ X⁻ ( 2a : X = I; 2b : X = CF₃SO₃). On the basis of NMR spectroscopic and X-ray diffraction studies, the cation can be described as a combination of an amino-2-phosphaallylic cation and its methylated derivative.