Crystal Structures of Two New Monoprotonated Products of 1,4,7 trimethyl-1,4,7-triazacyclononane: (Me_3〔9〕aneN_3H)(SO_3CF_3) and (Me_3〔9〕aneN_3H)I

１　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｓａｔｕｒａｔｅｄｍａｃｒｏｃｙｃｌｅｓｔｒｉａｚａｃｙｃｌｏｎｏｎａｎｅ（〔９〕ａｎｅＮ３）ａｎｄ１,４,７－ｔｒｉｍｅｔｈｙｌ－１,４,７－ｔｒｉａｚａｃｙｃｌｏｎｏｎａｎｅ（Ｍｅ３〔９〕ａｎｅＮ３）ａｒｅｍｅｍｂｅｒｓｏｆａｆａｍｉｌｙｏｆｐｏｔｅｎｔｉａｌｌｙｔｒｉ－ｄｅｎｔａｔｅｍａｃｒｏｃｙｃｌｉｃｌｉｇａｎｄｓｗｈｉｃｈｆｏｒｍｔｈｅｒｍｏｄｙｎａｍｉｃａｌｌｙａｎｄｋｉｎｅｔｉｃａｌｌｙｓｔａｂｌｅｃｏｍｐｌｅｘｅｓｗｉｔｈｈｅａｖｉｅｒｍａｉｎ…     

CRYSTAL AND MOLECULAR STRUCTURE OF THE HEXANUCLE-AR DIAZENIDO-OXOMOLYBDATE [(n-C_4H_9)_4N]_3[Mo_6O_(18)-(N_2C_6H_3-2,4-(NO_2)_2]

<正> Crystal of the title complex [(n-C4H9)4N]3[Mo6O18(N2C6H3-2,4-(NO2)2](Mr= 1710. 5) is orthorhombic with space group P21cn (Pna21), a = 17. 304(3), b = 17.580(2), c=24. 355(4) (?), V = 7409(2)(?)3, Z = 4, Dc=1. 60g/ cm3, μ=10. 29cm-1, F (000) = 3647. The structural solutions and refinements based on 3900 reflections (I≥3σ(I)) converged at R = 0. 0575, Rw =0. 0498. The atoms of Mo(3), Mo(4), O(1), O(5), O(9), O(11) and the [N2C6H3-2,4-(NO2)2] unit in the complex anion locate approximately in a plane about which the complex anion is nearly symmetrical.     

Mixed-valent [FeIV(mu-O)(mu-carboxylato)2FeIII]3+ core

The symmetrically ligated complexes 1, 2, and 3 with a (mu-oxo)bis(mu-acetato)diferric core can be one-electron oxidized electrochemically or chemically with aminyl radical cations [*NR3][SbCl6] in acetonitrile yielding complexes which contain the mixed-valent [(mu-oxo)bis(mu-acetato)iron(IV)iron(III)]3+ core: [([9]aneN3)(2FeIII2)(mu-O)(mu-CH3CO2)2](ClO4)2 (1(ClO4)2), [(Me3[9]aneN3)(2FeIII2)(mu-O)(mu-CH3CO2)2](PF6)2 (2(PF6)(2)), and [(tpb)(2FeIII2)(mu-O)(mu-CH3CO2)2] (3) where ([9]aneN3) is the neutral triamine 1,4,7-triazacyclononane and (Me3[9]aneN3) is its tris-N-methylated derivative, and (tpb)(-) is the monoanion trispyrazolylborate. The asymmetrically ligated complex [(Me3[9]aneN3)FeIII(mu-O)(mu-CH3CO2)2FeIII(tpb)](PF6) (4(PF6)) and its one-electron oxidized form [4ox]2+ have also been prepared. Finally, the known heterodinuclear species [(Me3[9]aneN3)CrIII(mu-O)(mu-CH3CO2)2Fe([9]aneN3)](PF6)2 (5(PF6)(2)) can also be one-electron oxidized yielding [5ox]3+ containing an iron(IV) ion. The structure of 4(PF6).0.5CH3CN.0.25(C2H5)2O has been determined by X-ray crystallography and that of [5ox]2+ by Fe K-edge EXAFS-spectroscopy (Fe(IV)-O(oxo): 1.69(1) A; Fe(IV)-O(carboxylato) 1.93(3) A, Fe(IV)-N 2.00(2) A) contrasting the data for 5 (Fe(III)-O(oxo) 1.80 A; Fe(III)-O(carboxylato) 2.05 A, Fe-N 2.20 A). [5ox]2+ has an St = 1/2 ground state whereas all complexes containing the mixed-valent [FeIV(mu-O)(mu-CH3CO2)2FeIII]3+ core have an St = 3/2 ground state. M?ssbauer spectra of the oxidized forms of complexes clearly show the presence of low spin FeIV ions (isomer shift approximately 0.02 mm s(-1), quadrupole splitting approximately 1.4 mm s(-1) at 80 K), whereas the high spin FeIII ion exhibits delta approximately 0.46 mm s(-1) and DeltaE(Q) approximately 0.5 mm s(-1). M?ssbauer, EPR spectral and structural parameters have been calculated by density functional theoretical methods at the BP86 and B3LYP levels. The exchange coupling constant, J, for diiron complexes with the mixed-valent FeIV-FeIII core (H = -2J S1.S2; S(1) = 5/2; S2 = 1) has been calculated to be -88 cm(-1) (intramolecular antiferromagnetic coupling) and for the reduced diferric form of -75 cm(-1) in reasonable agreement with experiment (J = -120 cm(-1)).     

SYNTHESIS AND CRYSTAL STRUCTURE OF A TUNGSTEN-COPPER-SULFUR CLUSTER [Et_4N]_2[WCU_3S_4(S_2CNEt_2)_3]

<正> [Et4N]2 [WCu3S4 (S2CNEt2)3], Mr = 1172. 01, orthorhombic, space group P212121 with a=12. 858(9),b=13. 204(5) ,c=29. 501(9) A ,V=5008. 7 A3, Z = 4, Dc = 1. 55gcm-3, μ(MoKa) = 40. 3cm-1. The final R and Rw are 0. 069 and 0. 075, respectively, for 3072 observed unique reflections. The anion contains a slightly distorted WS42~ tetrahedron coordinated by three CuS2 CNEt2 units,with four metal atoms lying in a plane.     

Synthesis and Structural Characterization of [Cu(DMF)_6][(η~5-C_5Me_5)WS_3(CuBr)_3]_2·Et_2O

1 INTRODUCTION In the last decade, we have been interested in the synthesis of [PPh4][(h5-C5Me5)MS3] (M = Mo, W)[1, 2] , Whose organometallic trisulfido anions show high reactivity towards various transition metals[3~6] . We once reported that the reaction of [PPh4][(h5-C5Me5)WS3] with CuBr in CH3CN afforded a double incomplete-cubane cluster [PPh4]2[(h5-C5Me5)WS3(CuBr)3]2[3], while the analogous reaction of [PPh4][(h5-C5Me5)WS3] with CuBr in CHCl3 gave rise to a 揻our-…     

Synthetic, X-ray Structure, Electron Paramagnetic Resonance, and Magnetic Studies of the Manganese(II) Complex of 1-Thia-4,7-diazacyclononane ([9]aneN(2)S)

Reaction of manganese(II) perchlorate hexahydrate with a methanol solution of 1-thia-4,7-diazacyclononane ([9]aneN(2)S) resulted in the isolation of the manganese(II) complex [Mn([9]aneN(2)S)(2)](ClO(4))(2). The X-ray structure of this complex is reported: crystal system orthorhombic, space group Pbam, No. 55, a = 7.937(2) ?,b = 8.811(2) ?, c = 15.531(3) ?, Z = 2, R = 0.0579. The complex is high spin (S = (5)/(2)) with an effective magnetic moment (&mgr;(eff)) 5.82 &mgr;(B) at 298 K and 5.65 &mgr;(B) at 4.2 K. Computer simulation of the Q-band EPR spectrum of [Mn([9]aneN(2)S)(2)](ClO(4))(2) yields g = 1.99 +/- 0.01, |D| = 0.19 +/- 0.005 cm(-)(1), and E/D = 0.04 +/- 0.02. For the analogous hexaamine complex [Mn([9]aneN(3))(2)](ClO(4))(2) ([9]aneN(3) = 1,4,7-triazacyclononane) analysis of the EPR spectra produced the following values: g = 1.98 +/- 0.01, |D| = 0.09 +/- 0.003 cm(-)(1), and E/D = 0.1 +/- 0.01. The spin Hamiltonian parameters for [Mn([9]aneN(2)S)(2)](ClO(4))(2) derived from the EPR spectra produced a good fit to the magnetic susceptibility data.     

Symmetry-based magnetic anisotropy in the trigonal bipyramidal cluster [Tp2(Me3tacn)3Cu3Fe2(CN)6]4+

Reaction of [(Me3tacn)Cu(H2O)2]2+ (Me3tacn = N,N',N' '-trimethyl-1,4,7-triazacyclononane) with [TpFe(CN)3]- (Tp- = hydrotris(pyrazolyl)borate) in a mixture of ethanol and acetonitrile affords the pentanuclear cluster [Tp2(Me3tacn)3Cu3Fe2(CN)6]4+. Single-crystal X-ray analysis reveals a trigonal bipyramidal structure featuring a D3h-symmetry core in which two opposing FeIII (S = 1/2) centers are linked through cyanide bridges to an equatorial triangle of three CuII (S = 1/2) centers. Fits to variable-temperature dc magnetic susceptibility data are consistent with ferromagnetic coupling to give an S = 5/2 ground state, while fits to low-temperature magnetization data indicate the presence of a large axial zero-field splitting (D = -5.7 cm-1). Frequency dependence observed in the ac magnetic susceptibility data confirms single-molecule magnet behavior, with an effective spin reversal barrier of Ueff = 16 cm-1. When compared with the much lower anisotropy barrier previously observed for the face-centered cubic cluster [Tp8(H2O)6Cu6Fe8(CN)6]4+, the results demonstrate the enormous influence of the geometry in which a given set of metal ions are arranged.     

Crystal Structure of 3－hydroxyl－1，5－diazacycloheptane Dihydrobromide C_5H_（12）N_2O·2HBr

ＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆ３－ｈｙｄｒｏｘｙｌ－１，５－ｄｉａｚａｃｙｃｌｏｈｅｐｔａｎｅＤｉｈｙｄｒｏｂｒｏｍｉｄｅＣ_５Ｈ_（１２）Ｎ_２Ｏ·２ＨＢｒＬＩＵＹｏｎｇ；ＸＵＥＧｕｏ－Ｐｉｎｇ；ＷＵＣｈｅｎｇ－Ｔａｉ（Ｄｅｐａｒｔｍｅｎｔｏｆ?..     

[CH3NH3][NH3(CH2)6NH3]H3[P2Mo2W16O62]·H2O的水热合成与表征

首次合成了[CH3NH3][NH3(CH2)6NH3]H3[P2Mo2W16O62]·H2O,通过元素分析、红外光谱和X射线单晶衍射对合成产物进行了表征,并用TGA-DSC研究了化合物的热稳定性.晶体属单斜晶系,P21/m空间群,a=1.2596(3)nm,b=1.8715(4)nm,c=1.9816(4)nm,α=γ=90°,β=90.16(3)°,V=4.671(2)nm3,Z=2,Mr=4358.66,Dc=3.100g·cm-3,μ=19.978mm-1,F(000)=3792,R=0.0835,Rw=0.2026.结果表明,在晶体结构内形成了0.7364nm×0.8354nm的微孔.     

Alkene cis-dihydroxylation by [(Me3tacn)(CF3CO2)RuVI O2)]ClO4(Me(3)tacn = 1,4,7-Trimethyl-1,4,7-triazacyclononane): structural characterization of [3 + 2] cycloadducts and kinetic studies

cis-Dioxoruthenium(VI) complex [(Me(3)tacn)(CF(3)CO(2))Ru(VI)O(2)]ClO(4) (1, Me(3)tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) reacted with alkenes in aqueous tert-butyl alcohol to afford cis-1,2-diols in excellent yields under ambient conditions. When the reactions of 1 with alkenes were conducted in acetonitrile, oxidative C=C cleavage reaction prevailed giving carbonyl products in >90% yields without any cis-diol formation. The alkene cis-dihydroxylation and C=C cleavage reactions proceed via the formation of a [3 + 2] cycloadduct between 1 and alkenes, analogous to the related reactions with alkynes [Che et al. J. Am. Chem. Soc. 2000, 122, 11380]. With cyclooctene and trans-beta-methylstyrene as substrates, the Ru(III) cycloadducts (4a) and (4b) [formula; see text] were isolated and structurally characterized by X-ray crystal analyses. The kinetics of the reactions of 1 with a series of p-substituted styrenes has been studied in acetonitrile by stopped-flow spectrophotometry. The second-order rate constants varied by 14-fold despite an overall span of 1.3 V for the one-electron oxidation potentials of alkenes. Secondary kinetic isotope effect (KIE) was observed for the oxidation of beta-d(2)-styrene (k(H)/k(D) = 0.83 +/- 0.04) and alpha-deuteriostyrene (k(H)/k(D) = 0.96 +/- 0.03), which, together with the stereoselectivity of cis-alkene oxidation by 1, is in favor of a concerted mechanism.     

Well-defined imidotitanium alkyl cations: agostic interactions, migratory insertion vs.[2+2] cycloaddition, and the first structurally authenticated AlMe(3) adduct of any transition metal alkyl cation

The imidotitanium alkyl cations [Ti(NtBu)(Me3[9]aneN3)R]+ (R = Me (3+) or CH2SiMe3(4+)) possess either a very weak alpha-agostic or beta-Si-C agostic interactions, respectively, according to 13C and 29Si NMR and DFT studies; reaction of (4+) with iPrNCNiPr gives totally selective insertion into the Ti-alkyl bond; reaction of 3+ with AlMe3 gives the first structurally characterised AlMe3 adduct of a transition metal alkyl cation (Me3[9]aneN3 = 1,4,7-trimethyltriazacyclononane).     

Osmium Complexes of 1,4,7-Triazacyclononane (tacn) and 1,4,7-Trimethyl-1,4,7-triazacyclononane (Me(3)tacn) and the X-ray Crystal Structure of [(Me(3)tacn)Os(eta(6)-C(6)H(5)BPh(3))]BPh(4).CH(3)CN

The complexes of osmium with tacn (1,4,7-triazacyclononane) and Me(3)tacn (1,4,7-trimethyl-1,4,7-triazacyclononane), [LOs (eta(6)-C(6)H(6))](PF(6))(2) (L = tacn) and LOsCl(3) (L = tacn, Me(3)tacn), have been prepared by substitution of L on [Os(eta(6)-C(6)H(6))Cl(2)](2) or [Os(2)Cl(8)](2)(-), respectively. Reaction of LOsCl(3) with neat triflic acid leads to partial replacement of chloride and formation of the binuclear Os(III)-Os(III) complexes [LOs(&mgr;-Cl(3))OsL](PF(6))(3) (L = tacn, Me(3)tacn). The binuclear nature was established by NMR spectroscopy and elemental analysis and, for L = tacn, a partially refined X-ray crystal structure which shows the Os-Os separation to be 2.667 ?, indicative of significant metal-metal bonding. Reduction of [LOs(&mgr;-Cl(3))OsL](3+) over zinc amalgam in either aqueous or non-aqueous solution yields the intensely colored Os(II)-Os(III) mixed-valence ions [LOs(&mgr;-Cl(3))OsL](2+). Electrochemical measurements on [LOs(&mgr;-Cl(3))OsL](3+) in CH(3)CN reveal the reversible formation of the mixed valence ions. These are further reduced at lower potential to the Os(II)-Os(II) binuclear species, reversibly for L = Me(3)tacn. (Me(3)tacn)OsCl(3) is oxidized by persulfate ion to give [(Me(3)tacn)OsCl(3)](+); zinc amalgam reduction in an aqueous solution at high concentration produces the binuclear complex [(Me(3)tacn)Os(&mgr;-Cl(3))Os(Me(3)tacn)](3+) or, at low concentration, a solution containing an air sensitive osmium(II) species. Addition of BPh(4)(-) results in the eta(6)-arene zwitterion [(Me(3)tacn)Os(eta(6)-C(6)H(5)BPh(3))](+), which was characterized by X-ray diffraction on the BPh(4)(-) salt. The compound crystallizes in the triclinic space group P1 with a = 11.829(2) ?, b = 12.480(3) ?, c = 17.155(4) ?, alpha = 84.42(2) degrees, beta = 83.52(2) degrees, gamma = 71.45(2) degrees, V = 2380(2) ?(3), Z = 2, and R = 7.62%, and R(w) = 7.39%.     

Highly efficient ethylene polymerisation by scandium alkyls supported by neutral fac-kappa3 coordinated N3 donor ligands

Reaction of [M(CH2SiMe3)3(THF)2] (M = Sc or Y) with the neutral fac-kappa3 N3 donor ligands (L) Me3[9]aneN3 or HC(Me2pz)3 gave the corresponding trialkyls [M(L)(CH2SiMe3)3]; activation of the scandium congeners with B(C6F5)3 in the presence of ethylene afforded highly active polymerisation catalysts (Me3[9]aneN3 = 1,4,7-trimethyltriazacyclononane).     

Syntheses,Crystal Structures and IR Spectra of Two Mixed Metal Complexes:〔Cr_nFe_(3-n)(μ_3-O)-(μ-O_2CC_2H_5)_6 Py_3〕Cl(n=1,2)

1INTR0DUCTI0NTrinuclearoxo-carboxylatocomplexescontainingmixedmetalionshavebeenofintenseinterestsincethefirststructuredeterminedbyX-raydiffractioninl965t1i,Theimportanceofthesecompoundsshowsinservingasmodelstotesttheoriesforthepotentialmagneticcoupllngbetweenmetalionsinmultinuclearsystem,asempha-sizedbyCANNONDetal.t2i.However,inrecentyears,wehavefoundthatthiskindofcompoundsmayactasaprecursorofthecatalystfortheadditi0nreactionofacetylenewitheitherH,O0rH,,andf0rtheketonizationofacidbydec…     

Synthesis and Structure of a Dimolybdenum Carbonyl Compound with Thiolato-Bridges [Et4N] 2 [Mo2 (CO) 8 (SC6H4-Cl -p) 2]

Reaction of Mo (CO)6 with p-Cl-C6H4SNa and Et4NCl · H2O in CH3CN afforded a dinuclear molybdenum (0) compound [Et4N]2 [Mo2 (CO)8 (SC6H4-Cl-p)2] (1). The crystal structure was determined by X-ray diffraction. The crystallographic data: C36H48Cl2Mo2N2O8S2, Mr= 963.71, monoclinie, P21/c, a=9. 269(4),b=13.750(3), c=17.466(6) A ;β=104.84(3)°; V=2151.8(3) A3; Z=2; Dc=1.49 g/cm3; F(000)=984; μ=8.3 cm-1; MoKα radiation (λ=0. 71073A ); Final R = 0. 055 and Rw=0. 065 for 3287 reflections with I＞3. 0σ(I). The X-ray structure analysis revealed that the Mo2S2 core is planar. The geometry around each Mo atom is a distance is 4. 014(2) A , and this obviously indicates the absence of Mo-Mo bond.     

Synthesis and Structure of Dinuclear Molybdenum Carbonyl Thiolate Compound [Et4N ] 2 [Mo2 (CO) 8 (SC6H4-OCH3-p) 2]

Reaction of Mo(CO)6 with p-H3CO-C6H4SNa and Et4NCl · H2O in CH3CN afforded a dinuclear molybdenum(0) compound [Et4N]2[Mo2 (CO)8 (SC6H4-OCH3-p)2] (1). The crystal structure was determined by X-ray diffraction. The crystallographic data: C38H54Mo2N2O10S2, Mr = 954.87, triclinic, P-1, a = 11.348 (7), b =11.616(5), c=10.065(7) A, a=113.86(4), β=111.39(5), γ=91.92(5)°, V=1104.0(1) A3, Z=1, Dc=1.44 g/cm3, F(000)=492, μ=7.0cm-1, Final R=0. 046 and Rw=0. 049 for 2657 reflections with I＞3. Oσ(I). The X-ray structure analysis revealed that the Mo2S2 core of 1 is planar. The geometry around each Mo atom is a distorted octahedron, the two octahedrons form an edge-sharing bioctahedron. The bond. In addition, the 95Mo NMR chemical shift of 1 is discussed.     

PREPARATION AND STRUCTURAL CHARACTERIZATION OF [Cd(2-SC_5H_3NH-3-SiMe_3)I_2]_2

<正> Reaction of cadmium iodide (CdI2) with 3-(trimethylsilyl)-pyri-dine-2-thiol(TSPT ) in methanol yields the title compound. The dimeric complex C16-H26NzSi2S2I4Cdz crystallizes in the monoclinic system, space group P21/n, a = 7. 712 (3), b = 24. 55(1), c = 8. 170(1) A,β=95.86(2)°, V = 1539(2) A3, Mr=1099. 12, Z = 2, F(000) =1008, μ= 55.65cm~1,Dc = 2. 37gcm-3, final R = 0. 046 and Rw = 0. 052 for 1066 observed unique reflections. The molecule with [Cd2I4]0 core has a center symmetry and the TSPT ligand is present as monodentate donor in the neutral thione form , protonated at the pyridine nitrogen. The existence of this structure may be rationalized on the basis of intermolecular hydrogen bonding between the NH proton of the ligand and the terminal iodine atom of the adjacent molecules.     

Synthesis and Structure of Dinuclear Molybdenum Carbonyl Thiolate Compound[Et4N]2[Mo2(CO)8(SC6H4-CH3-p)2]

1　ＩＮＴＲＯＤＵＣＴＩＯＮＳｉｎｃｅｔｈｉｏｌａｔｅｌｉｇａｎｄｗａｓｉｎｔｒｏｄｕｃｅｄｉｎｔｏｍｏｌｙｂｄｅｎｕｍｃａｒｂｏｎｙｌｃｏｍｐｏｕｎｄｉｎ1 984 [1],ｔｈｅｉｎｖｅｓｔｉｇａｔｉｏｎｏｎｌｏｗ ｖａｌｅｎｃｅＭｏ -ＳＲｃｏｍｐｏｕｎｄｓｈａｓｒｅｃｅｉｖｅｄａｔｔｅｎｔｉｏｎｆｏｒｔｈｉｓｋｉｎｄｏｆｌｏｗ ｖａｌｅｎｃｅｃｏｍｐｏｕｎｄｓｐｏｓｓｅｓｓｃｅｒｔａｉｎａｄｖａｎｔａｇｅｏｎｃｏｍｐｏｕｎｄｓｙｎ ｔｈｅｓｉｓ,ｍｏｌｅｃｕｌｅｓｔｒｕｃｔｕｒｅａｎｄｐｈｙｓｉｃａｌａ…     

Synthesis and Crystal Structure of (E)-[1-Ferrocenyl-2-(4-Chlorophenyl) ethylene]

1INTRoDUCTIoNCurrently,thereisaconsiderableinterestintheinvestigationoforganicandorganometallicmaterialsshowinglargenonlinearopticalresponse.Theirpotentialusehasbeenresearchedindeviceapplicationswhicharerelatedtothetelecommuni-cations,opticalcomputingandopticalinformationprocessing"2i.Onamicroscopiclevel,oneofthemajorphysicalparameterstodecidethenonlinearopticalpropertiesofmaterialsisthemolecularhyperpolarizability,avaluedeterminedbyelectronicandgeometricstructureofmolecule.Thetitlecompoun…     

Encapsulation of metal cations and anions within the cavity of bis(1,4,7-triazacyclononane) receptors

The synthesis and characterisation of a new bis([9]aneN3) ligand (L4) containing two [9]aneN3 macrocyclic moieties separated by a 2,6-dimethylenepyridine unit is reported. A potentiometric and 1H NMR study in aqueous solution reveals that ligand protonation occurs on the secondary amine groups and does not involve the pyridine nitrogen. The coordination properties toward Cu(II), Zn(II), Cd(II) and Pb(II) were studied by means of potentiometric and UV spectrophotometric measurements. The ligand can form mono- and binuclear complexes in aqueous solution. In the 1 : 1 complexes, the metal is sandwiched between the two [9]aneN3 moieties and the pyridine N-donor is coordinated to the metal, as actually shown by the crystal structure of the compound [ZnL4](NO3)2.CH3NO2. L4 shows a higher binding ability for Cd(II) with respect to Zn(II), probably due to a better fitting of Cd(II) ion inside the cavity generated by the two facing [9]aneN3 units. The formation of binuclear complexes is accompanied by the assembly of OH-bridged M2(OH)x (x = 1-3) clusters inside the cavity defined by the two facing [9]aneN3 units, and pyridine is not involved in metal coordination. A potentiometric and (1)H NMR study on the coordination of halogenide anions by L4 and its structural analogous L3 in which the two [9]aneN3 units are separated by a shorter quinoxaline linkage, shows that bromide is selectively recognised by L4, while chloride is selectively bound by L3. Such a behaviour is discussed in terms of dimensional matching between the spherical anions and the cavities generated by the two [9]aneN3 units of the receptors.