Reaction of trimethylaluminum with calixarenes. I. Synthesis and structure of [Calix[8]arene methyl ether] [AlMe3]6·2 toluene and of [p-tert-butylcalix[8]arene methyl ether] [AlMe3]6·4 benzene

Reaction of the methyl ether of calix[8]arene with AlMe₃ yields [calix[8]arene methyl ether] [AlMe₃]₆·2 toluene,1, while that ofp-tert-butylcalix[8]arene gives [p-tert-butylcalix[8]arene methyl ether] [AlMe₃]₆·4 benzene,2. Both compounds1 and2 fail to react with alkali metal salts, MX. In1, the absence of a butylpara-substituent affords greater flexibility than is the case for thetert-butyl compound2. Thus, all six of the AlMe₃ groups are located on the outside of the macrocyclic ring (in projection) in1, but two AlMe₃ units are found on the inside in2. Colorless, air-sensitive crystals of1 belong to the triclinic space group witha=13.690(8),b=14.317(4),c=14.738(6) Å, =76.11(3), =62.36(4), =82.41(4)^o, andD _c =1.06 g cm^–3 forZ=1. Refinement led toR=0.101 for 1154 observed reflections.2 crystallizes in with =12.400(6),b=16.229(8),c=19.251(5) Å, =96.17(3), =107.25(3), =101.54(3)^o, andD _c =1.01 g cm^–3 forZ=1. Refinement of2 gaveR=0.128 for 4351 observed reflections. The macrocyclic array in both1 and2 lies about a crystallographic center of inversion. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82049 (48 pages).     

Calixarenes 11. Crystal and molecular structure ofp-tert-butylcalix[8]arene

Monoclinic prisms were obtained by slow evaporation of a pyridine solution ofp-tert-butylcalix[8]arene: space groupP2₁/c,a=20.312(3),b=23.020(2),c=20.006(6) ; =113.05(2)⁰;V=8707.6 ų;Z=4. Refinement led to anR value of 0.166 for 4231 reflections which, although high, is sufficient to establish the conformation of the molecule as a pleated loop in which the eight hydroxyl groups are arranged in a slightly undulating, almost planar, intramolecularly hydrogen bonded cyclic array. The possible inferences for the conformation ofp-tert-butylcalix[8]arene in solution are discussed. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82019.     

An inclusion complex between acetonitrile andp-tert-butylcalix[6]arene

p-tert-Butylcalix[6]arene forms a complex with 1.5 acetonitrile molecules, that are included in the macrocycle cavity. This complex crystallizes in the monoclinic system: space groupP2₁/m,a=14.043(4),b=16.916(11),c=14.199(11) Å,=98.27(6)°,V=3338(4) ų,Z=2 (formula units). Refinement led to a final conventionalR value of 0.113 for 1654 reflections. Thepinched cone conformation of the calixarene is the same as that of the neutral and freeR-calix[6]arene already described. The two acetonitrile molecules interact with some phenyl ring -clouds, a methylene bridge and sometert-butyl groups of the calixarene. Supplementary Data relating to this article (atomic coordinates for hydrogen atoms, anisotropic displacement parameters, selected geometrical parameters and observed and calculated structure factors) are deposited with the British Library as Supplementary Publication No. SUP 82188 (16 pages).     

Host-guest interactions in aqueous media withp-tert.-butylcalix[4]arene bearing polyoxyethylene chains

The interactions ofp-tert.-butylcalix[4]arene bearing polyoxyethylene chains (C3) with pyrene (Py), 1-anilino-8-naphthalenesulfonate (ANS) andN-phenyl-naphthylamine (NPN) in aqueous solution were studied by absorption and fluorescence measurements. Absorption spectral changes and fluorescence enhancements reveal that C3, which has a hydrophobic cavity, can include organic molecules and ions in aqueous solution and form 11 host-guest complexes with ANS and NPN. C3 forms inclusion complexes with Py at different stoichiometries depending on the host: guest molar ratio. Binding constants of 2.2×10⁴, 2.0×10⁴ and 3.6×10⁵ dm³ mol^–1 were calculated for the C3Py, C3ANS and C3NPN complexes (11), respectively, based on the Benesi-Hildebrand equation.Author for correspondence.     

Crystal and molecular structure of two calix[6]arenes:p-Isopropylcalix[6]arene andp-tert-butylcalix[6]arene—benzene(1∶3) complex

The isopropyl derivative crystallizes from a mixture of carbon disulfide and benzene in the orthorhombic system: Space groupP2₁ nb, a=17.420(3),b=17.708(3),c=18.972(3) Å,V=5852(3) Å,Z=4. Thet-butyl derivative crystallizes from benzene, but the crystal is a complex (13), space groupP,a=15,065(5),b=19.103(3),c=13.878(3) Å, =106.95(2), =102.72(2), =80.61(2),V=3703(2) ų,Z=2. Refinement led toR=0.185 for 1512 reflections for the isopropyl derivative, a sufficiently high number to establish the conformation of the molecule; for thet-butyl complexR=0.12 for 7340 reflections. Intramolecular hydrogen bonds are given as well as comparison of the conformation of both compounds. Thet-butyl groups and the benzene molecules are disordered but the isopropyl groups are not. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82071 (57 pages).     

Molecular inclusion in functionalized macrocycles part 10*: Crystal and molecular structure of ap-tert-butylcalix[6]arene hexapodand

Colourless prismatic crystals of (3) were obtained from ethanol/CH₂Cl₂ (1:1) solution, space groupP2₁/c,a=14.581(5),b=22.517(8),c=11.799(5) , =92.13(4)°. Refinement led to a final conventionalR value of 0.074 for 4247 reflections. The conformation of the molecule, which lies on a center of symmetry, is 1,2,3-alternate with one oligoethereal chain pointing inside the molecular cavity. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. 82011 (30 pages).For part 9, see [1]. Results presented in part at the Second International Symposium of Clathrate Compounds and Molecular Inclusion Phenomena, Parma, Italy, 1982.     

p-tert-Butyldihomooxacalix[4]arene/p-tert-Butylcalix[4]arene: Transition and Heavy Metal Cation Extraction and Transport Studies by Ketone and Ester Derivatives

The binding properties of two phenylketones (2a and 3a) and two ethylesters (2b and {3b) derived from p-tert-butyldihomooxacalix[4]arene or from p-tert-butylcalix[4]arene, in the cone conformation, towards transition (Ag⁺, Ni²⁺, Cu²⁺, Co²⁺, Zn²⁺, Fe²⁺ and Mn²⁺) and heavy (Cd²⁺, Hg²⁺ and Pb²⁺) metal cations have been determined by extraction studies with metal picrates and liquid membrane transport experiments with the same salts. The affinity of these ligands for Ag⁺ has also been investigated by ¹H NMR spectroscopy. Both ketones are better extractants than the esters, and show a strong preference for Ag⁺, while Cu²⁺ is the most extracted cation with the esters. ¹H NMR titrations with AgSO₃CF₃ indicate 1 : 1 complexes for all ligands, those with ketones are more stable, on the NMR time scale, than those with esters. Both esters are good carriers for Ag⁺, and 2b exhibits the highest transport rate (4.7 mol h^-1) found until now with dihomooxacalix[4]arene derivatives.     

Polymeric membrane sodium-selective electrodes based on calix[4]arene ionophores

Six kinds of tetra alkylester type calix[4]arene derivatives, (R₁=R₂=CH₃1, C₂H₅2, C₃H₇3,n-C₄H₉4,t-C₄H₉5,n-C₁₀H₂₁6), a diethyl-didecyl mixed ester type (R₁=C₂H₅, R₂ =C₁₀H₂₁7), and three kinds of lower rim bridged types (R₁=C₂H₅, R₂–R₂=(CH₂)₁₀8, (CH₂)₁₂9, (CH₂)₂(OCH₂CH₂)₃10) were characterized by electrochemical measurement to elucidate the effect of the length of the alkyl group of alkoxycarbonyl substituents on Na⁺ selectivity. To obtain excellent Na⁺ selective ionophores, introduction of short chain alkyl groups rather than long chain ones, such as a decyl group, and maintenance of sufficient solubility of the calix[4]arene derivatives in the membrane solvent are required concurrently. Among the calix[4]arenes tested, 25,26,27,28-tetrakis[(ethoxycarbonyl)methoxy]-p-tert-butylcalix[4]arene2, and the diethyl-didecyl mixed ester type derivative7 are the best ionophores for a Na⁺ selective electrode. On the other hand, sodium selectivity of the bridged type derivative9 is comparable or even superior to that of the known bis(12-crown-4).This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

p-t-Butylcalix[4]arene tetra-acetamide: a new strong receptor for alkali cations [1]

From the reaction ofp-t-butylcalix[4]arene with -chloro-N,N-diethyl acetamide a new lipophilic ether-amide ligand (2) has been obtained in high yield. Solution studies show (2) to be a very strong cation receptor for alkali cations, especially sodium and potassium. The X-ray crystal structure determination of the free ligand (2) and two potassium complexes (KI and KSCN) shows the calix[4]arene in a fixed cone structure and the cation completely encapsulated in a polar cavity of eight oxygen atoms. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82059 (57 pages).Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Inclusion of multi-ring compounds byp-tert-butylcalix[5]arene

The inclusion complex ofp-tert-butylcalix[5]arene with tetralin has been characterized in the solid state by a single crystal X-ray diffraction study and by¹³C CP/MAS NMR experiments. A crystallographic mirror plane bisects the calix[5]arene and contains the tetralin molecule (which is dynamically disordered). The guest penetrates the upper rim of the calixarene and the experimental results indicate the saturated ring is imbedded most deeply.p-tert-Butylcalix[5]arene (tetralin) · 2 EtOH belongs to the monoclinic space group C2/m witha = 22.187(6),b = 15.823(6),c = 18.168(5) Å, = 99.70(2)°, andD _c = 1.09 g cm^–3 forZ = 4. Refinement based on 1652 observed reflections led to a finalR value of 0.081. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82/82129 (19 pages).     

Alternative methods of modifying the calixarene conformation. The synthesis and molecular structures oft-butylcalix[4]arene methyl ether complexed with aluminum alkyl species

The configurations of calix[4]arenes may be modified by the formation of donor-acceptor complexes which make use of the basicity of the oxygen atoms of the macrocycle. The complex [t-butylcalix[4]arene methyl ether][AlMe₃]₂,2, exhibits the previously unseen 1,2-alternate geometry, while [t-butylcalix[4]arene methyl ether][MeAlCl₂]₂,3, and [t-butylcalix[4]arene methyl ether][EtAlCl₂]₂,4, show the 1,3-alternate configuration.2 crystallizes in the triclinic space groupPl witha=11.14(1),b=11.60(1),c=12.02(1) Å, =77.32(8), =67.91(8), and =69.34(8)^o withD _c =1.06 g cm^–3 forZ=1. Refinement based on 1270 observed reflections led toR=0.106.3 as the benzene solvate belongs to the monoclinic space groupC2/c witha=12.116(2),b=21.557(7),c=23.470(6) Å, and =104.05(2)^o withD _c =1.13 g cm^–3 forZ=4. Refinement based on 2335 observed reflections led toR=0.075.4 crystallizes in the monoclinic space groupC2/c witha=12.062(4),b=21.175(6),c=21.596(5) Å, and =100.78(4)^o withD _c =1.18 g cm^–3 forZ=4. Refinement based on 2529 observed reflections gaveR=0.082. The Al-O lengths in all three complexes are normal for donor-acceptor interactions. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82053 (45 pages).     

A Rational Approach Towards Determination of Optical Ionicity and Non-covalent Interactions in Fullerene-Calix[4]arene Host-Guest Complexes

The present article reports the host-guest complexation of a calix[4]arene derivative, namely 4-iso-propyl-calix[4]arene (1), with fullerenes (both C₆₀ and C₇₀) in toluene and benzonitrile solutions. It is observed that the charge-transfer (CT) absorption bands are located in the ground state for the C₆₀ and C₇₀ complexes of 1. By utilizing the CT absorption bands, various important physicochemical parameters like the oscillator strength, resonance energy, transition dipole moment, electronic coupling element and solvent reorganization energies have been estimated for the C₆₀-1 and C₇₀-1 complexes. The CT transition energy is very helpful for determining the vertical ionization potential of 1 in solution. Jobs method of continuous variation was used to establish 1:1 stoichiometry for the fullerene complexes of 1. The most fascinating feature of the present study is that 1 binds C₇₀ preferentially compared to C₆₀ as obtained from binding constant (K) data. The effect of solvent on the complexation of fullerenes (C₆₀ and C₇₀) with 1 is clearly observed from the trend in the K values: in toluene and whereas in benzonitrile, and . Molecular mechanics force field (MMMF) calculations reveal fascinating features regarding the binding pattern of fullerenes towards 1 in vacuo in terms of enthalpy of formation. MMMF calculations establish that during C₇₀-1 complexation, C₇₀ is directed in an end-on manner rather than the traditional side-on pattern.     

Synthesis,X-ray crystal structure and cation binding properties of a tetrahomodioxacalix[4]arene tetraester

Treatment ofp-t-butyltetrahomodioxacalix[4]arene with ethyl bromoacetate yields a tetraester derivative (4) whose crystal and molecular structure have been determined and whose ion binding properties have been assessed by phase transfer and stability constant measurements. Colorless transparent triclinic crystals (obtained from methoxyethanol) C₆₂H₈₄O₁₄,a = 10.347(2),b = 11.583(2),c = 13.448(3) Å, = 72.04(2), = 86.50(2)°, = 81.23(2)°, space group ,Z = 1, MoK radiation = 0.70930 Å. Refinement was carried out using 2221 reflections withI > 1.5(I). The complexation properties resemble those of calix[6]arene hexaester (6), although weaker, with a preference for the larger alkali cations. Ca²⁺ and Ba²⁺; though not extracted, are more strongly complexed than alkali cations. Eu³⁺ is better complexed than Na⁺.Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82106 (22 pages) and at the Cambridge Crystallographic Data Centre, University Chemical Laboratory, Lensfield Road, Cambridge CB2 9EW, U.K.     

X-ray crystallographic studies of tricarbonylchromium complexes of calix[4]arene conformers: On an unusual conformation which appears in cone conformers

The structures of three arene-tricarbonylchromium complexes prepared from cone and 1,3-alternate-25, 26,27,28-tetrapropoxycalix[4]arene(1) and Cr(CO)₆ were determined by single crystal X-ray studies. Crystal data for 1,3-alternate-1·Cr(CO)₃ are space groupP2₁/a,a=19.496(3)Å,b=11.118(2)Å,c=19.121(2)Å, =109.95°(1) andV=3895ų. The structure was refined toRw=0.068. Crystal data for cone-1·Cr(CO)₃ are space groupP2₁/a,a=21.457(4)Å,b=12.184(1)Å,c=14.816(2)Å, =91.61°(1) andV=3872ų. The structure was refined toRw=0.077. Crystal data for cone-1·2Cr(CO)₃ are space groupP2₁/a,a=18.019(3)Å,b=41.347(4)Å,c=11.743(2)Å, =97.39°(1) andV=8676ų. The single crystal included two similar but slightly different structures but the data were successfully refined toRw=0.092. The structure of 1,3-alternate-1·Cr(CO)₃ differs only slightly from that of the regular 1,3-alternate calix[4]arene. In contrast, cone-1·Cr(CO)₃ and cone-1·2Cr(CO)₃ show an unusual conformation with a pair of faced gablelike roofs, which is considerbly distorted from the regular cone calix[4]arene. The origin of this distortion is discussed in combination with the spectral studies.This paper is dedicated to the commemorative issue of the 50th anniversary of calixarenes.     

Crystal and molecular structures of binuclear caesium complexes with 1,3-calix[4]-bis-crown-6 and 1,3-calix[4]-bis-benzo-crown-6

The crystal structures of two binuclear complexes between caesium and 1,3-calix[4]-bis-crowns have been determined. Cs₂ Bis-benzoC6(NO₃)₂. 3CHCl₃ (1) in whichBis-benzoC6 is 1,3-calix[4]-bis-benzo-crown-6, crystallizes in the orthorhombic system: space groupPca2 ₁ a=19.513(10),b=15.382(5),c=23.708(9) Å,V=7116(5) ų,Z=4. Refinement led to a final conventionalR value of 0.065 for 2321 reflections. The structure of (1) is analogous to those already reported withBis-C6, (in whichBis-C6 is, 1,3-calix[4]-bis-crown-6) and NO ₃ ^– as a counter-ion. Cs₂ Bis-C6(NCS)₂ (2) crystallizes in the monoclinic system: space, groupC2 a=36.57(2),b=11.47(1),c=13.65(1) Å, =109.03(5)°.,V=5415(6) ų,Z=4. Refinement led to a final conventionalR value of 0.063 for 2227 reflections. Compound (2) is made of dimers bridged by a disordered NCS^– ion. The crown ether chain conformations are discussed. Supplementary data relating to this article (atomic coordinates, anisotropic displacement parameters, bond distances and angles and observed and calculated structure factors) are deposited with the British Library as Supplementary Publication No. SUP 82199 (52 pages).     

Complexation of alkali metal cations by calix[4]Arene-bis-crown-6 in methanol,acetonitrile and propylene carbonate

Résumé The interactions of Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺ with the double-crown calix, calix[4]arene-bis-crown-6, have been studied in methanol, acetonitrile, and propylene carbonate at 25°C using precise conductivity measurements. For Li⁺ and Na⁺ in solutions containing this calix[4]arene, only 1:1 cation:ligand complexes are formed which permit the determination of the thermodynamic complexation formation constants,K _f. The conductivity data strongly suggest that 2:1 cationcalixarene complexes form with K⁺, Rb⁺, and Cs⁺. The existence of 2:1 complexes was experimentally confirmed for the potassium systems by a mass spectroscopic method.     

Exo-H- andendo-H-η4-pentamethylcyclopentadiene complexes of platinum

A mixture ofendo-H andexo-H isomers (1a and1b) of the (⁴-C₅Me₅H)PtCl₂ complex was prepared by the reaction of K₂PtCl₄ with C₅Me₅H in MeOH. The mixture of isomers reacts with CpTl in the presence of TiBF₄ to give a novel complex, [(⁴-C₅Me₅H)Pt(⁵-C₅H₅)]⁺BF₄ ^–, as a mixture ofendo-H- andexo-H-isomers (2a and2b). The data of¹H and¹³C NMR spectroscopy of the resulting complexes are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 514–517, March, 1994.     

Synthesis,characterization, and X-ray structure of 1,2-bis-crown-5-calix[4]arene. Modeling of metal complexation

1,2-bis-crown-5-calix[4]arene (3) was prepared by reacting calix[4]arene (1) with tetraethylene glycol di-p-toluenesulphonate (2) in the presence of cesium carbonate in 9% yield. The X-ray structure of (3) was determined. Crystal data for C₄₄H₅₂O₁₀ are as follows: monoclinic, space groupP _2/c witha=18.006(8) Å,b=10.680(4) Å,c=22.359(6) Å, =112.93(3)°,V=3958(6) ų,Z=4,D _calc=1.2 g cm^–3, the finalR value is 0.11 for the 1851 observed reflections (I>3(I)). The single crystal included two similar but slightly different molecules immobilized in a pinched-cone conformation withC ₂ symmetry. The two enantiomorphous molecules were analyzed by molecular mechanics using the GenMol program to model the selective alkali-metal complexation.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Unexplored metallic cation effect in the acidity constants of p-t-butylthiacalix[4]arene,p-t-butylcalix[4]arene and p-t-butylcalix[6]arene in aqueous-organic media

The influence of the metallic cation of the base (Li⁺, Na⁺ or K⁺) was determined on the acid–base constants of p-t-butylthiacalix[4]arene (TC4), p-t-butylcalix[4]arene (CA4) and p-t-butylcalix[6]arene (CA6) in ethanol/water in an large interval of pH values by potentiometry and spectrophotometry. The pK_a values determined by both methods correlate very well and these are characteristic for each macrocycle with influence of the cation of the base without a straight evidence of an effect by the size of the metallic cation. In the case of TC4, pK_a1 and pK_a2 were lower to Li⁺ and Na⁺ than with K⁺. For CA4, an effect of K⁺ on the pK_a2 with respect to Li⁺ was observed. A very different behaviour was observed for CA6 with Li⁺ and K⁺ showing a lower pK_a2 and a higher pK_a3 than with Na⁺. These effects were interpreted on the basis of the interaction/complexation of each cation with each macrocycle.     

Structural study of the 1:1 clathrate of an asymmetric calix[4]arene and acetone

The crystal and molecular structure of the 1:1 clathrate of the asymmetric calix[4]arene,1, and acetone has been determined by X-ray analysis. The crystal data are: tetragonal, space groupP4/n,a=b=12.574(6),c=12.572(6) Å,V=1988(2) ų,Z=2,D _x =1.111 g cm^–3,D _m =1.108 g cm^–3. Least-squares refinement based on 1131 observed reflections withF ₀>3(F ₀) and anisotropic temperature factors led toR=0.096. In spite of the molecular asymmetric calixarene1 the crystal structure has high symmetry, because a part of the host and guest molecules are in disordered states.