Halide Substitution Research Articles

Ionic Liquid Brush as a Highly Efficient and Reusable Catalyst for On‐Water Nucleophilic Substitutions

AbstractA very efficient and reusable catalyst has been developed for the on‐water nucleophilic substitution of alkyl halides and tosylates with azide or thiocyanate in excellent to quantitative yields. The reaction proceeds smoothly and cleanly without any organic cosolvent or other adductive, and the brush can be reused at least 10 times without noticeable loss of the catalytic activity. The high efficiency, simplicity of product and catalyst isolation, outstanding recyclability, and organic‐solvent‐free conditions show promise for the use of this catalyst in the laboratory and in industry.

Highly regio- and chemoselective palladium(0)-mediated allylic substitution of difunctional allylic halides with phenols

An efficient Pd(0)-mediated, base-assisted reaction of phenols with difunctionalised allylic halides results in the formation of coupled products in good yields. The reactions proceed with excellent stereo-, regio- and chemocontrol. An appropriately functionalised Weinreb amide, synthesised by this methodology, undergoes halogen-lithium exchange and subsequent intramolecular 1,2-carbonyl addition/elimination to give an advanced macrocyclic intermediate with potential use in the synthesis of likonide B.

ChemInform Abstract: Cyclopentadienyl Replacement by Trispyrazolylborate and the Syntheses of M(η5-C5H5) (HB(C3H3N2)3)X2 (M: Hf, X: Cl; M: Zr, X: Cl, OPh, OC6H4-4-NO2, OC6H4-4-OMe, OC6H4-2-Ph).

Abstract The reactions between M{C 5 H 5 } 2 Cl 2 (M = Zr, Hf) and HB(C 3 H 3 N 2 ) 3 H afford M (η 5 -C 5 H 5 ){HB(C 3 H 3 N 2 ) 3 }Cl 2 . These compounds undergo halide substitution reactions with phenols and the new complexes Zr(η 5 -C 5 H 5 ){HB(C 3 H 3 N 2 ) 3 }X 2 (X = Cl, OC 6 H 4 Z; Z = H, 4-NO 2 , 4-OMe, 2-Ph) have been isolated and characterized.

ChemInform Abstract: Influence of Functional Substitution of Allyl Halides on Their Ni(CO)4- Promoted Carbonylative Cycloaddition with Acetylenes.

Abstract The effect of functional substitution of allyl halides on the outcome of the title reaction has been studied. Electron withdrawing and olefinic groups had different effects depending on their location. When they were placed at the central position of the allyl moiety carbonylative cycloaddition was found to be the main reaction, in acetone, to yield exclusively cyclohexenone (or aromatic) derivatives. In contrast, the same groups at the terminal site and in exteded conjugation with the allylic funtion were shown to favour competing side reactions such as allyl self-coupling. However, only cyclopentenones were obtained from either centrally or terminally substituted silylallyl halides. Substitution at both ends of the allyl moiety led to the formation of 4,5-disubstituted cyclopentenones. Important mechanistic information could be achieved from determination of the relative stereochemistry in these compounds.

Pentiptycene Building Blocks Derived from Nucleophilic Aromatic Substitution of Pentiptycene Triflates and Halides

The nucleophilic aromatic substitution (S(N)Ar) reactions of the nitro-substituted pentiptycene triflate 15 with LiBr and LiI and the resulting halides 18 and 19 with N(3)(-), CN(-), and ArS(-) in DMF provide an efficient route toward pentiptycene halides and dihalides and other new pentiptycene building blocks. The reactivity of diaminopentiptycene in Pd-catalyzed C-N coupling reactions is also demonstrated.

Functional polyisobutylenes via a click chemistry approach

1-(ω-Azidoalkyl)pyrrolyl-terminated polyisobutylene (PIB) was successfully synthesized both by substitution of the terminal halide of 1-(ω-haloalkyl)pyrrolyl-terminated PIB with sodium azide and by in situ quenching of quasiliving PIB with a 1-(ω-azidoalkyl)pyrrole. Azide substitution of the terminal halide was carried out in 50/50 heptane/DMF at 90 °C for 24 h using excess azide. The 1-(ω-haloalkyl)pyrrolyl-PIB precursors included 1-(2-chloroethyl)pyrrolyl-PIB, 1-(2-bromoethyl)pyrrolyl-PIB, and 1-(3-bromopropyl)pyrrolyl-PIB. In situ quenching involved direct addition of 1-(2-azidoethyl)pyrrole to quasiliving PIB initiated from 5-tert-butyl-1,3-di(1-chloro-1-methylethyl)benzene (bDCC)/TiCl4 at −70 °C in hexane/CH3Cl (60/40, v/v). 1H NMR analysis of the quenched product revealed mixed isomeric end groups in which PIB was attached at either C2 or C3 of the pyrrole ring (C2/C3 = 0.40/0.60). SEC indicated the absence of coupled PIB under optimized conditions, confirming exclusive mono-substitution on each pyrrole ring. 1-(3-Azidopropyl)pyrrolyl-PIB was reacted in modular fashion with various functional alkynes, propargyl alcohol, propargyl acrylate, glycidyl propargyl ether, and 3-dimethylamino-1-propyne, via a Huisgen 1,3-dipolar cycloaddition (Click) reaction, using Cu(I)Br/N,N,N′,N″,N″-pentamethyldiethylenetriamine or bromtris(triphenylphosphine)Cu(I) as catalyst. The reactions were quantitative and produced PIBs bearing terminal hydroxyl, acrylate, glycidyl, or dimethylaminomethyl groups attached via exclusively four-substituted triazole linkages. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2533–2545, 2010

Diversity of Metal−Ligand Interactions in Halide (X = I, Br, Cl, F) and Halide-Free Ambiphilic Ligand Rhodium Complexes

Reaction of the neutral ambiphilic ligand 2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene (TXPB) with [{Rh(mu-Cl)(CO)(2)}(2)] yields [RhCl(CO)(TXPB)] (1) (Emslie et al. Organometallics 2006, 25, 5835). Complex 1 is square planar with the TXPB ligand bound to rhodium via the phosphine and thioether donors (these are features common to complexes 2-5, vide infra). Treatment of 1 with Me(3)SiBr and Me(3)SiI allowed for halide substitution to afford [RhBr(CO)(TXPB)] (2) and [RhI(CO)(TXPB)] (3), respectively. The halide co-ligands in complexes 1 and 2 form a strong bridging interaction between rhodium and the borane group in TXPB. The presence of stronger borane-halide coordination in 1 is clearly illustrated by an (11)B NMR chemical shift of 12 ppm versus 27 ppm in 2. In contrast, the iodide ligand in 3 forms only a weak bridging interaction to boron, leading to a B...I distance of 3.125(7) A, and an (11)B NMR chemical shift of 56 ppm (versus 69 ppm for free TXPB). A lower carbonyl stretching frequency in 3 (2002 cm(-1)) versus 1 or 2 (2008 and 2013 cm(-1), respectively) could be attributed to weakening of the Rh-X bond in 1 and 2 as a consequence of halide-borane coordination and/or a shorter Rh-S bond in complex 3. [Rh(CO)(TXPB-F)] (4) and the halide-free cation [Rh(CO)(TXPB)][PF(6)] (5) were accessed by reaction of 1 with [NMe(4)]F and Tl[PF(6)], respectively. Complex 4 is zwitterionic with fluoride bound to boron [(11)B NMR delta 4 ppm; B-F = 1.445(6) A; Rh...F = 3.261(3) A] and an eta(2)-interaction between the cationic rhodium center and the ipso- and ortho-carbon atoms of a B-phenyl ring in TXPB-F. By contrast, rhodium in 5 engages in an eta(2)-interaction with boron and the ipso-carbon of one B-phenyl ring; Rh-B and Rh-C(ipso) bond lengths in 5 are 2.557(3) and 2.362(2) A, respectively. The long Rh-B distance and an (11)B NMR chemical shift of 57 ppm are consistent with only a weak Rh-B interaction in 5, and a CO stretching frequency of 2028 cm(-1) (Nujol), versus 2004-2013 cm(-1) for complexes 1-4, is indicative of greatly reduced electron density in 5, relative to 1-4.

Synthesis, characterization and primary evaluation of the synthetic efficiency of supported vinyltins and allyltins

Supported vinyltins and allyltins grafted to an insoluble cross-linked polystyrene matrix were prepared using methods usually employed in solution, like hydrostannylation of alkynes, transmetallation of a tin halide with organomagnesium or organozinc reagents, and substitution of an allyl halide by a supported stannylanion or SN2′ substitution of a supported β-stannylacrolein acetal by cyanocopper reagents in the presence of boron trifluoride etherate. The insoluble grafted organotin reagents were analysed by HRMAS NMR, allowing an unambiguous assignment of their isomeric distribution or the identification of side products. When involved in Stille cross-coupling reactions (vinyltins) or in addition on aldehydes (allyltins), these supported reagents exhibit similar reactivity and similar stereoselectivity when compared to the tributyltin analogues, with the advantage to prevent problems due to the contamination by tin residues.

Expedient access to branched allylic silanes by copper-catalysed allylic substitution of linear allylic halides

An unprecedented copper-catalysed allylic transposition enables the regioselective synthesis of branched allylic silanes from linear allylic halides through direct C-Si bond formation.

Synthesis, characterization, and study of the photophysics and photocatalytic properties of the photoinitiated electron collector [{(phen) 2Ru(dpp)} 2RhBr 2](PF 6) 5

The heterometallic photoinitiated electron collector [{(phen) 2Ru(dpp)} 2RhBr 2](PF 6) 5 (phen = 1,10-phenanthroline, dpp = 2,3-bis(2-pyridyl)pyrazine) has been synthesized and studied by spectroscopic, photophysical, electrochemical, and photochemical techniques. Substitution of chloride with bromide in the previously reported [{(phen) 2Ru(dpp)} 2RhCl 2](PF 6) 5 complex presents a new photoinitiated electron collector which can assist in understanding the functioning of our supramolecular systems [{(TL) 2Ru(BL)} 2RhX 2](PF 6) 5 (TL = terminal ligand, BL = bridging ligand, X = halide) in the photoinitiated electron collection and generation of hydrogen through the reduction of water and a detailed comparison is presented. Both the bromide and chloride analogues of these supramolecular complexes contain low energy, emissive metal-to-ligand charge transfer ( 3MLCT) excited states that populate lower lying metal-to-metal charge transfer ( 3MMCT) excited states. The electrochemistry of these complexes showed an impact on the reduction of the central Rh III upon halide substitution with the bromide analogue [(phen) 2Ru(dpp)} 2RhBr 2](PF 6) 5 having a slightly lower reduction potential than the corresponding chloride counterpart. The more positive reduction of Rh III to generate the Rh I species in the bromide analogue impacts the photocatalytic properties upon photolysis in the presence of a sacrificial electron donor. The trimetallic complex [{(phen) 2Ru(dpp)} 2RhBr 2](PF 6) 5 generates hydrogen through the reduction of water with higher yields than the chloride [{(phen) 2Ru(dpp)} 2RhCl 2](PF 6) 5 analogue under the same conditions. Despite the longer lived 3MLCT state of both [(TL) 2Ru(dpp)] 2+ and [{(TL) 2Ru} 2(dpp)] 4+ when TL = phen vs. bpy (bpy = 2,2′-bipyridine), the phen trimetallics with X = Cl − or Br − do not display longer lived 3MLCT states and show lower H 2 yields than the analogous bpy trimetallic systems.

Syntheses of fluorous quaternary ammonium salts and their application as phase transfer catalysts for halide substitution reactions in extremely nonpolar fluorous solvents

Perfluoromethyldecalin solutions of the fluorous alkyl halides R f 8(CH 2) m X ( m=2, 3; X=Cl, I) are inert toward aqueous NaCl, KI, KCN, and NaOAc. However, substitution occurs at 100 °C in the presence of 10 mol % of the fluorous ammonium salts ( R f 8(CH 2) 2)(R f8 (CH 2) 5) 3N + I − ( 1) or ( R f 8(CH 2) 3) 4N + Br − ( 2) (10 mol %), which are fully or partially soluble in perfluoromethyldecalin under these conditions. Stoichiometric reactions of (a) 1 and R f 8(CH 2) 3Br, and (b) 2 and R f 8(CH 2) 2I are conducted in perfluoromethyldecalin at 100 °C, and yield the same R f 8(CH 2) m I/ R f 8(CH 2) m Br equilibrium ratio (60–65:40–35). This shows that ionic displacements can take place in extremely nonpolar fluorous phases, and suggests a classical phase transfer mechanism for the catalyzed reactions. Interestingly, the non-fluorous ammonium salt mixture CH 3(CH 3(CH 2) m ) 3N + Cl − ( 3, Aliquat ® 336; m=2:1 7/9) also catalyzes halide substitutions, but under triphasic conditions with 3 suspended between the lower fluorous and upper aqueous layers. NMR experiments establish very low solubilities in both phases, suggesting interfacial catalysis.

Theoretical Studies of the Nucleophilic Substitution of Halides and Amine at a Sulfonyl Center

Gas-phase nucleophilic substitution reactions, F(-) + CH(3)SO(2)F, Cl(-) + CH(3)SO(2)Cl, Cl(-) + CH(3)SO(2)F, and NH(3) + CH(3)SO(2)Cl, have been investigated at the B3LYP/6-311+G** and MP2/6-31+G* levels of theory. A very shallow well for the reaction intermediate in a triple-well potential energy surface (PES) was observed for the identity fluoride exchange, but double well PESs were obtained for the other three reactions with three different PES profiles. NBO analyses of the transition states showed substantial charge transfer interactions in all cases which provided a much larger amount of stabilization energy compared with the corresponding species at the carbon center of methyl halides. This difference is primarily caused by the strong electropositive nature of the sulfur center. The F-S-F axial linkage in the distorted TBP type intermediate in the identity fluoride exchange reaction exhibited a weak three-center, four-electron omega-bonding, which is considered to provide stability of the intermediate. All the reactant (RC) and product complexes (PC) have Cs symmetry. The symmetry plane bisects angles HCH (of methyl group), OSO (of sulfonyl group), and HNH (of ammonia). Vicinal charge transfer interactions between the two out-of-plane C-H, S-O, and N-H bonds provide extra stabilization to the ion-dipole complexes together with H-bond formation of in-plane H atom with the nucleophile and/or leaving group.

Heats of Formation and Bond Dissociation Energies of the Halosilanes, Methylhalosilanes, and Halomethylsilanes

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for SiH(3)X, SiH(2)XCH(3), and SiH(3)CH(2)X with X = F, Cl, Br, and I from coupled cluster theory (CCSD(T)) calculations with effective core potential correlation-consistent basis sets for Br and I. To achieve near chemical accuracy (+/-1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, and a correction for first order atomic spin-orbit effects. Vibrational zero point energies were computed at the CCSD(T) level of theory and the C-H and Si-H stretches scaled to experiment. The C-H, Si-H, Si-C, C-X, and Si-X (X = F, Cl, Br, and I) bond dissociation energies (BDEs) in the halosilanes, halomethysilanes, and methylhalosilanes were predicted. Except for methyliodosilane, methyl substitution leads to an increase in Si-X BDE when compared to the Si-X BDE in the halosilanes. Except for methyliodosilane, halide substitution leads to an increase in the Si-C BDE in comparison to the Si-C BDE in methylsilane of 86.9 kcal/mol at 0 K. Unlike the methylhalosilanes, the halomethylsilanes all show a decrease in the Si-C BDE when compared to the Si-C BDE in methylsilane. The trends correlate with the electronegativity of the substituent.

Ionic Transformations in Extremely Nonpolar Fluorous Media: Easily Recoverable Phase-Transfer Catalysts for Halide-Substitution Reactions

Solutions of the fluorous alkyl halides R(f8)(CH(2))(m)X (R(fn)=(CF(2))(n-1)CF(3); m=2, 3; X=Cl, Br, I) in perfluoromethylcyclohexane or perfluoromethyldecalin are inert towards solid or aqueous NaCl, NaBr, KI, KCN, and NaOAc. However, halide substitution occurs in the presence of fluorous phosphonium salts (R(f8)(CH(2))(2))(R(f6)(CH(2))(2))(3)P(+)X(-) (X=I (1), Br (3)) and (R(f8)(CH(2))(2))(4)P(+)I(-) (10 mol %), which are soluble in the fluorous solvents under the reaction conditions (76-100 degrees C). Stoichiometric reactions of a) 1 with R(f8)(CH(2))(2)Br and b) 3 with R(f8)(CH(2))(2)I were conducted under homogenous conditions in perfluoromethyldecalin at 100 degrees C and yielded the same R(f8)(CH(2))(2)I/R(f8)(CH(2))(2)Br equilibrium ratio ( approximately 60:40). This shows that ionic displacements can take place in extremely nonpolar fluorous phases and suggests a classical phase-transfer mechanism for the catalyzed reactions. Interestingly, the nonfluorous salt (CH(3)(CH(2))(11))(CH(3)(CH(2))(7))(3)P(+)I(-) (4) also catalyzes halide substitutions, but under triphasic conditions with 4 suspended between the lower fluorous and upper aqueous layers. NMR experiments established very low solubilities in both phases, which suggests interfacial catalysis. Catalyst 1 is easily recycled, optimally by simple precipitation onto teflon tape.

Reactions of [Mo(≡CBr)(CO)2{HB(pzMe2)3}] (pz = pyrazol-1-yl) with Amines: Synthesis of Amino, Pyridinium, and Thiolato Carbyne Complexes

The reactions of the bromocarbyne complex [Mo(≡CBr)(CO)2{HB(pzMe2)3}] (pz = pyrazol-1-yl) with a range of secondary and heterocyclic amines have been investigated and found in each case to proceed via simple nucleophilic halide substitution to provide N-functionalized carbyne derivatives, some of which are not available via conventional approaches. With diethylamine or piperazine the simple dialkyaminocarbyne complexes [Mo(≡CNEt2)(CO)2{HB(pzMe2)3}] or [Mo{≡CN(C2H4)2NH}(CO)2{HB(pzMe2)3}] were obtained. With 4-N,N-dimethylaminopyridine the pyridiniumcarbyne salt [Mo(≡CNC5H4NMe2-4)(CO)2{HB(pzMe2)3}]Br was obtained; pyridine provided a complex intractable mixture and collidine failed to react. N-Methylimidazole provided the imidazolium derivative [Mo(≡CNC3H3NMe)(CO)2{HB(pzMe2)3}]Br, while N-(trimethylsilyl)imidazole gave the neutral imidazolyl derivative [Mo(≡CNC3H3N)(CO)2{HB(pzMe2)3}] and N,N′-bis(trimethylsilyl)imidazolium bromide. The sulfenamide HN(SPh)2 afforded the thiolatocarbyne complex [Mo(≡CSPh)(CO)2{HB(pzMe2)3}] rather than the expected aminocarbyne complex [Mo{≡CN(SPh)2}(CO)2{HB(pzMe2)3}], while HN(PPh2S)2 failed to react. The complex 1 is unreactive toward 1,8-diazabicycloundecene (DBU); however prolonged heating results in the formation of [DBUH][Mo(O)3{HB(pzMe2)3}] via base-induced hydrolysis/oxidation.

Low-Frequency Mode Activity of Heme: Femtosecond Coherence Spectroscopy of Iron Porphine Halides and Nitrophorin

The low-frequency mode activity of metalloporphyrins has been studied for iron porphine-halides (Fe(P)(X), X = Cl, Br) and nitrophorin 4 (NP4) using femtosecond coherence spectroscopy (FCS) in combination with polarized resonance Raman spectroscopy and density functional theory (DFT). It is confirmed that the mode symmetry selection rules for FCS are the same as for Raman scattering and that both Franck-Condon and Jahn-Teller mode activities are observed for Fe(P)(X) under Soret resonance conditions. The DFT-calculated low-frequency (20-400 cm (-1)) modes, and their frequency shifts upon halide substitution, are in good agreement with experimental Raman and coherence data, so that mode assignments can be made. The doming mode is located at approximately 80 cm (-1) for Fe(P)(Cl) and at approximately 60 cm (-1) for Fe(P)(Br). NP4 is also studied with coherence techniques, and the NO-bound species of ferric and ferrous NP4 display a mode at approximately 30-40 cm (-1) that is associated with transient heme doming motion following NO photolysis. The coherence spectra of three ferric derivatives of NP4 with different degrees of heme ruffling distortion are also investigated. We find a mode at approximately 60 cm (-1) whose relative intensity in the coherence spectra depends quadratically on the magnitude of the ruffling distortion. To quantitatively account for this correlation, a new "distortion-induced" Raman enhancement mechanism is presented. This mechanism is unique to low-frequency "soft modes" of the molecular framework that can be distorted by environmental forces. These results demonstrate the potential of FCS as a sensitive probe of dynamic and functionally important nonplanar heme vibrational excitations that are induced by the protein environmental forces or by the chemical reactions in the aqueous phase.

Do general nucleophilicity scales exist?

AbstractComprehensive nucleophilicity scales including π‐, n‐ and σ‐nucleophiles have been constructed using benzhydrylium ions and structurally related quinone methides as reference electrophiles. It is shown how the correlation (Eqn (1)) log k20°C = s(E + N), where s and N are nucleophile‐specific parameters and E is an electrophile‐specific parameter, has recently been employed to characterize further classes of nucleophiles (phosphines, amines, isonitriles, trifluoromethanesulfonyl‐substituted carbanions) and electrophiles (2‐benzylideneindan‐1,3‐diones and benzylidenebarbituric acids). Practical applications of the reactivity parameters E, N and s for developing Friedel–Crafts alkylations in neutral alcoholic or aqueous solution and for characterizing nucleophilic organocatalysts will be discussed. Eventually, a new correlation equation will be presented, which includes Eqn (1), the Ritchie equation (nucleophilic additions to stabilized carbocations), and the Swain–Scott equation (nucleophilic substitutions of methyl halides) as special cases. Copyright © 2008 John Wiley & Sons, Ltd.

Rearrangement, Nucleophilic Substitution, and Halogen Switch Reactions of Alkyl Halides over NaY Zeolite: Formation of the Bicyclobutonium Cation Inside the Zeolite Cavity

Rearrangement and nucleophilic substitution of cyclopropylcarbinyl bromide over NaY and NaY impregnated with NaCl was observed at room temperature. The first-order kinetics are consistent with ionization to the bicyclobutonium cation, followed by internal return of the bromide anion or nucleophilic attack by impregnated NaCl to form cyclopropylcarbinyl, cyclobutyl, and allylcarbinyl chlorides. The product distribution analysis revealed that neither a purely kinetic distribution, similar to what is found in solution, nor the thermodynamic ratio, which favors the allylcarbinyl halide, was observed. Calculations showed that bicyclobutonium and cyclopropylcarbinyl carbocations are minimal over the zeolite structure, and stabilized by hydrogen bonding with the framework structure. A new process of nucleophilic substitution is reported, namely halogen switch, involving alkyl chlorides and bromides of different structures. The reaction occurs inside the zeolite pores, due to the confinement effects and is an additional proof of carbocation formation on zeolites. The results support the idea that zeolites act as solid solvents, permitting ionization and solvation of ionic species.

Dipalladium Bis(μ-isopropylthiolato) Complexes with a [Pd2S2] Core Supported by N-Heterocyclic Carbenes

The reaction of Pd(OAc)2 with 1,3-dibenzylbenzimidazolium bromide (A) and 1-propyl-3-methylbenzimidazolium iodide (B) afforded the dihalo-bis(carbene) complexes cis-[PdBr2(Bz2-bimy)2] (1) and cis-[PdI2(Pr,Me-bimy)2] (2), respectively. Halide substitution of 1 and 2 with AgO2CCH3 gave the mixed diacetato-bis(carbene) complexes cis-[Pd(O2CCH3)2(Bz2-bimy)2] (3) and cis-[Pd(O2CCH3)2(Pr,Me-bimy)2] (4). In situ deprotonation of isopropylthiol with the mixed carbene-carboxylato complexes 3 and 4 yielded the novel dipalladium complexes [Pd2(μ-iPr-S)2(Bz2-bimy)4](BF4)2 (5) and [Pd2(μ-iPr-S)2(Pr,Me-bimy)4](BF4)2 (6) with a [Pd2S2] core solely supported by N-heterocyclic carbenes. All compounds have been fully characterized by multinuclei NMR spectroscopies and ESI mass spectrometry. The solid state molecular structures of complexes 2, 3, 5, and 6 have also been confirmed by X-ray diffraction studies.

Structural analysis of xCsCl(1 − x)Ga2S3 glasses

Sulphide glasses doped with rare-earth ions have been demonstrated to be suitable for photonic applications such as optical amplifiers, up-converters and fiber lasers. The substitution of metal halides into the glass network has been shown to result glasses with desirable properties in terms of quantum efficiency and fiber manufacture [J.R. Hector, J. Wang, D. Brady, M. Kluth, D.W. Hewak, W.S. Brocklesby, D.N. Payne, Journal of Non-Crystalline Solids 239 (1998) 176]. To assist in the understanding of this improvement a structural analysis of glasses with a composition xCsCl(1−x)Ga2S3 has been undertaken in order to examine the nature of the gallium environment. Information collected by high energy X-ray diffraction and neutron diffraction have been analyzed to permit the identification of the structural units as Ga centered tetrahedra. The interconnection between the tetrahedra was found to be predominantly corner sharing.